Yesterday, it was hot enough that the thermometer I'd laid on the workbench in the yard the night before exploded sometime during the afternoon. I forgot about it, and I guess it couldn't handle the internal pressure from the heat, so the little bulb at the bottom just crumbled. The top of it's scale was 120F, and it had another unmarked few degrees of space after that, so I guess that it was significantly more than 130F in the direct midday sunlight. Around 112F for shaded air temperatures, according to the thermal sensor I still had on the bike for the motor controller tests.
That makes the second exploded thermometer I've had this year. I need to remember to not leave them in the sun. :roll:
Today, it was hotter and more humid, then around 830pm it finally dumped a bunch of water on us, along with some gusty medium winds. Around an hour later, when I left work, the rain was down to a drizzle with bursts of showering, and it was STILL HOT; the rain was like a shower just before the hot water runs out. :( Better than nothing, but I was hoping to ride home in cold wetness.
The bike performed way better than I thought, after I'd taped clear plastic bags around the PDA bike computer and the two DMMs I still had on it for testing. The brakes pretty much don't work when wet unless I adjust them down so much that they squeak on the wheel with just a touch on the handle; then I actually get a little stopping power and if I squeeze REALLY hard I can actually lock up the wheel and make it skid (kinda fun, but scary). I really wish I had disc brakes.
I'm seriously considering taking some 5.25" harddisk platters I have and drilling them for mounting holes and vent/drainage holes, then designing a clamping/braking system for them and using them for disc brakes front and rear. I'd have to remove the media surface so they wouldn't be slick, and just have a plain aluminum surface. It should be possible to do this; I'm just not sure how well they'll work. First I need to learn more about how disc brakes are designed, as I only know the very *basic* stuff I've seen when helping change pads on a car's brakes once, many years ago.
The rest of it kept working fine even when I went thru some several-inch-deep puddles that were longer than the bike. Some of them 20+ feet long, and one at least 6 or 7" deep at an intersection where water just piles up due to no drainage. Deep enough that the pedals and my feet went down under the water at the bottom of the stroke. Glub blubblub glub. The motor kept getting very wet, so it was still pretty cool when I got home, despite riding using motor only, not pedalling (just leaving my feet on the pedals as they go round). Usually it's too hot to keep my hand on for long. It was noticeably warm, but only that, this time.
Monday, August 31, 2009
Yesterday, it was hot enough that the thermometer I'd laid on the workbench in the yard the night before exploded sometime during the afternoon. I forgot about it, and I guess it couldn't handle the internal pressure from the heat, so the little bulb at the bottom just crumbled. The top of it's scale was 120F, and it had another unmarked few degrees of space after that, so I guess that it was significantly more than 130F in the direct midday sunlight. Around 112F for shaded air temperatures, according to the thermal sensor I still had on the bike for the motor controller tests.
Sunday, August 30, 2009
Now I am nearly done making my pedal freewheel. Just the adapter to bolt the chainring to the freewheel is left, and deciding if I want to weld, braze, or JBWeld the freewheel adapter to the crank.
I really don't think JBWeld would hold up, based on past attempts at using it for stuff like this. It just can't take the twisting loads and shear forces like that.
So here's the basic adapter:
The rightside bottom bracket bearing cup is press-fit onto the carefully-filed (but still not perfectly round or centered) crank arm, at the shaft end. Then the freewheel is threaded onto it backwards from the way it would go on a rear wheel, since now it's on the left side of the bike, and has to ratchet in the opposite direction.
Once it's threaded fully on, then the lockring from the BB bearing cup is threaded onto it, and tightened down to ensure the freewheel will not unthread itself with the force of pedalling, since the threads are the same direction as the unscrewing forces would be from the forces on the chainring/freewheel against the crank.
I wanted to round off the crank arm's axle end on the lathe, but the arm is too long to fit above the bed, and moving the bed upwards and securing it so it would not move with the high loads placed on it by the swinging crank arm in it's jaws proved impossible with the things I have here. It just moved too much with each rotation, and would have come loose from the bed (very bad).
If I had something like a pottery wheel with a centerbolt, I could've used that to do it, but I don't, and the time it would take to create something similar is too great right now, even though I could use it for many things later.
I had some 1/8" hard aluminum (dunno what alloy) from scrapped custom-made test fixtures, so I chose that to make the chainring adapter plate since I can more precisely work with it than with steel.
I first clamped down the chainring in question to the surface of the aluminum plate, then used a drywall screw to score around the edges of it as needed to mark where I will need to cut and drill to attach it and clear the teeth, etc. Then I determined the center of it, and used the only hole saw I have (about 1/4" smaller than the freewheel's rim, unfortunately) to bore the center hole. I also drilled out the six chainring mounting holes using the plastic chainring spacer as a guide to mark them first.
The adapter will be the same diameter as the plastic spacer, partly to act as a chain guard for the sprocket (I have had two pairs of pants "eaten" by the chain on this in high winds so far, even though I had the second pair tucked into the sock!). It's also so that I can use it to bolt to larger chainrings should that be desireable later on, without making a new adapter.
The plastic spacer will be used between the adapter and the chainring, just as it was between this chainring and the larger one that actually connected to the spider/crank on the cottered cranks it came off of.
More or less, this is what it might look like if I also use the chainguard that came with it (except that the adapter plate will of course be cut out round).
This is the set of parts for it, including the cottered crank the chainring and plastic spacer came from.
Mostly what's left is to cut out the adapter plate from it's source plate, then get that plate on the lathe (probably using the larger cottered ring bolted to it, minus the crank, so that I can clamp it in the chuck jaws), and then lathe out the center hole to be perfectly round and centered, and as good a fit as I can get on the freewheel. First I have to put the lathe back together, and I was way too overheated and oversunned today to do that.
Then I drill holes near the inner edge to line up with the tooth gaps, and bolt that adapter to the freewheel's teeth. Then I can play with spacing if needed, so it will fit the space between the crank and the BB. Might require some filing away of BB bearing cup hex head on this adapter assembly, but shouldn't take much. It fits perfectly on the right side, but I need it on the left side, which has a BB cup that sticks out a tad farther.
Then all that's left is that brazing/welding decision. I don't have stuff to braze with, but I know someone that does, and I will ask if he will do it or let me use his stuff to do it. Welding I can do here very easily, but I am not confident that I can keep from destroying the threads with spatter or warping if i do it that way, even if I could mask it off somehow.
I am so close; it would be great to not have to windmill my feet to keep up with the motor driving the pedals when I choose not to pedal but want to run the motor for these tests (or later in the winter when I know my knees will hurt a lot worse than they do now).
Also so that I can then come up with a regen-braking-capable shiftable drivetrain for the motor side of things, that won't feed back into the pedals.
Remember I had been running on 24V, and I upped that to 36V?
So far the performance difference is pretty noticeable. Zippier starts with less current draw, both very important as the idea is to keep me from having to put any load on my poor knees (especially the kind of load needed to start from a stop, with a 120 pound bike plus me and cargo). Plus I need to keep current draw low so as to be able to draw more total power from the batteries over a longer period (Peukert's Law).
I didn't just change the voltage, I also changed the gearing for the motor, so that it still outputs about the same max speed to the rest of the drivetrain, but because of that it has better startup torque and gets to speed faster, and is in the high-current/low-speed region for a much shorter time.
So now, even with less total Ah on the bike (was 2x 12v 31Ah, is now 3x 12V 17Ah) it gets better results than it did before. I have not yet tested it's full range, but I think it will probably wind up slightly better range (was 15+ miles at around 15-16mph average cruising speed including sometimes generous pedalling, is now at least 10 miles at around 17-18mph average cruising speed with no pedalling, and only lost about 1-2mph over the last couple of miles).
I think that higher voltage, causing it to draw less amps for less time during acceleration, is combining with the Peukert effect to allow me to draw more from the lesser-capacity batteries.
At 24V the average cruising current was at a guess 15+ amps (didn't have a way to measure exactly, as I had no meter to do that). Startup currents were enough to pop the little 25 amp breaker I had installed, if I didn't help it start by pedalling pretty hard for at least a few strokes. At 36V the average cruising current is around 6-10 amps. Startup currents are over 20 amps (HF meter now used only goes that high), but it never pops the breaker.
The temperature of the heatsink never went more than about 11°F above ambient. When it was really hot on the way to my friend's place, around 1pm, it was about 112°F in the area, and that's the same thing the sensor read. On the way back home, about 2am-ish, it was around 80F when I started, and rose to 91°F for short periods during and just after high-current acceleration tests (starting up in the highest gear to put the most load on the motor). It cooled by several degrees within about 30 seconds or less, and stayed generally around 86°F.
So I guess I don't need a heatsink any bigger than that little bitty one for the small current draws this motor pulls with this gearing at these voltages. That's good, because bigger heatsinks generally weigh more and they take up more space, both of which are bad for this bike. ;)
Well, the quick road test day before yesterday with the panel meter was half success, half failure, in that I found it only drew around 7 or 8 amps most of the time for cruising (at around 17-18MPH no pedalling), and pegged at 30+ at startup from complete stop for just about half a second before dropping quickly down to that steady rate.
However, after I parked the bike outside a store while I got some groceries, something must have happened to the meter, possibly because of direct sunlight heating it up (though I can't see why; there is no visible sign of a problem). When I came out it was stuck at around 6 amps, and I panicked at first as I thought something had shorted in the controller and was powering the motor even at a dead stop.
But after quickly yanking the main controller's Anderson connector (I haven't installed the battery cutoff yet), it stayed at 6 amps. I could tap the face and it wiggles, so it's not stuck, but it doesn't go to zero (it *was* at zero when I went inside, after turning it off and taking the key with me).
I hooked the power back up, turned it on and tested, and the system
itself still works fine, but the meter does not respond at all.
I unscrewed the casing and verified the movement coil is not burned open, but it doesn't respond to a controlled tiny voltage input either, not even from my multimeter on Diode Test. So something must be mechanically wrong; I suspect they must have used some adhesive to
secure the needle movement to the actual coil, which may have come loose from the heat of sunlight. I have to take the movement out of it to check that. There is nothing obvious wrong with it other than cheap physical construction.
Well, it looks like the movement coil itself has no continuity, so either one of the fine wires connecting it to the external red & black wires is broken, or it's burned open (which makes no sense since it still worked at shutoff, and had not yet had power thru it again).
Only a few hours and I already broke a new toy. :-(
In the meantime, I decided to ride the bike a longer distance (5 miles) on main streets on the way to a friend's to then carpool to a meeting all the way across the valley. I wanted to run it without pedalling at max speeds wherever possible, to test out the batteries and the controller heatsink, etc.
To that end, I wired up and zip-tied on a current meter (in the motor loop), a pack voltmeter, and a temperature-capable meter (with it's sensor down at the base of the heatsink). It looks awful, but I can glance down and read pack voltage and motor current draw at any moment, as well as controller heatsink temperature.
I thought about placing the thermal sensor on the MOSFETs themselves, inside the case, but decided not to, partly because I would have to dismount the controller, open the case, etc., and then do that again when I wanted to take it off after the test. Since I already verified that the MOSFETs don't get enough different temperature from the heatsink even at stall current for me to feel the difference with my fingers, then they should not be more than a few degrees different from it at most even though they're inside the case while the heatsink protrudes out of it.
If my theory is wrong, Murphy will notify me sooner rather than later, I'm sure. ;-)
I've also had a problem with the PDA and our intense midday sunlight, in that when it shines directly on the LCD, it darkens it and makes it difficult at best to read. Probably also damages it.
So I put this smoke-transparent plastic paper-guide-support from the back of some Epson inkjet in my junkpile onto the bars above it, in a way that shades it from most light above and at least a little to the sides, to see how well that might work but still allow some light thru for me to see it by, and not block my view of it.
I tried to get better pics of it, but it's just hard to see. Maybe it will show up better when I take the bike out on the driveway for some overall pics later.
It works pretty well, and unexpectedly it also helps keep certain road dust and whatnot out of my face, without blocking airflow to me. I'm not sure why that works, but it does.
Friday, August 28, 2009
JEB, a very generous person that found my project via Endless Sphere's EV forums, sent me a care package of some things that might be useful. I didn't really have any idea what to expect; mostly I figured it might be scrap bike parts and stuff like that, leftover from his own projects.
But it was better than that. :-)
That's the box, on the kitchen table.
Of course, it was opened as carefully as possible, not knowing the contents. This USPS box design is pretty good; it has a couple of straps that pass up from the bottom that can be secured to the inner flaps to hold them down, making it a lot more secure in shipping than if it only was taped together on the outer flaps. I think you could ship a couple of lead-brick wheelchair batteries in here. Seriously.
Not much popcorn. Generally that means that with a box this full, there must be lots of goodies. ;-)
This is the overview of what's in there. Just the stuff closer than the computer tower and cooking implements.
There's an HF battery cutoff switch, which I've been needing (all I really had before that'd be appropriate for that was some household-circuit-breaker sized switch/breakers, from a stage lighting system, but which each weigh a lot more than I'd want to use just for a cutoff switch (plus whatever mounting method I'd have to use).
Radio Shack analog meter. I love analog displays. They just have a...visual texture to them that digital ones can't meet. :) I used to have one by some other company, similar to it but larger, but I have not seen it in years (I also had abused it before I understood enough about how to use it to have damaged it some, so it never gave accurate readings).
Even though digital gauges might be more accurate than analog, and easier to instantaneously read a value from, the analog response is faster, usually, and you can see swings in the readings
that you do not get to see in the digital ones. Having both would be the best ideal, but that's only easily achieved in software with a pixellated display. Then the response time is slowed, because it's still being sampled and digitized and then displayed.
Perhaps it will become a part of the bike instrumentation panel, to monitor battery pack voltage and the like.
There's two angle grinders look serviceable, though the note explains they're old and not used for years, so I'll probably check and clean bearings and such before trying them out. Same for the straight grinder, which is potentially even more useful, as it's like a heavy-duty version of my Dremel (minus the variable speeds).
Even the variable speeds can be done, because I still have the power controller out of the treadmill my motor came from, which simply took rectified AC and switched it on and off. If this motor will take DC (haven't checked yet, but most power tools will), then I can simply put an AC-style outlet on the treadmill controller board, plug it into the grinder, and have a variable speed controller for the grinder. :) It's slightly more complicated than that, but not much.
The 30A-range panel meter is going to go on the bike today, so I can see what current draw I have directly during operation. I just have to splice it into the battery line or motor power supply line. (I am considering making it switchable between the two). At the moment I'm more interested in motor current, so I'll probably do that first.
The nuts and bolts and washers--very useful. I've been running out of matching ones large enough to be usable for the bike without being too large for the purpose. These are identical in threading and size to some I'm already using, including those on the wheelchair battery posts. There's at least two lengths of the same thread/size bolt, plus nuts and washers that match.
The cutoff wheels are an amusing thing, because I had just a day or so ago been looking around for and not finding the identical pack of them I am *sure* I had around here somewhere, and had to use a modified 3" wheel instead (had to bore out the center hole to fit the arbor). The smaller wheels sure don't last very long. :)
All the other wheels/etc (even the well-used ones) are helpful, because they will be used until there is no more nub left. :) The brush should really help with cleaning up some of my welds and such. Much easier than the manual method.
There's also some small brushes and some electrical tape (can't ever have too many rolls of that around, as it is nearly as handy as duct tape and zip ties).
Then there is the big surprise: A Curtis 1204-410 motor controller.
48V/125A 1-hour rating (200A 5-minute rating, 275A 2-minute rating). I presume it's dead, since it's been opened up, but haven't tested it. There's no obvious blown parts or anything, so whatever is wrong is probably going to take some work to find. It should be very useful once fixed. I'll have to check it out and see what's wrong soon. I'd hoped to find schematics available online, even if just reverse-engineered, but there weren't any in about 30 minutes searching. Otmar of http://cafeelectric.com (home of the Zilla) has partial documentation of a different model, and that will probably help some since I'm sure the engineering culture is similar enough between the two to figure things out from there.
There are also pics of his own projects (since he doesn't have a web presence for them), which are very interesting; a regular recumbent with ICE on an extension frame, a recumbent trike with electric assist, and an electric pusher trailer, amongh others.
I like his style of doing things in these projects; they're much better made than mine, but also appear to be salvage at least in some part.
While I was at lunch at work, I moved the rear turn signals down to the same place as the rest of the rear lighting cluster, simply because where they were on the back of the seat, they'd be blocked by any cargo I put on that rear rack that's wider than a foot or so.
I needed to take home a stack of empty boxes, and they were going to cover the whole width of the bike, plus some. I could just use the LED turn signals, of course, but the automotive ones are brighter and more noticeable due to their larger surface area (and will be brighter still for daylight once I have the LEDs in them instead, with less power consumption. At night they will automatically be dimmer if I can make the ALS work correctly, so they won't blind people close to me, especially those in a direct line behind me).
So now rather than being screwed down into the steel tube of the seat back support, they're screwed into the aluminum bracket for the taillight bars, and then ziptied (for now) to keep them from wiggling.
Previously the wiggling was stopped by the back square of the signal housing resting on the top of the tubing, but now that's out in the air.
All these pics in this post of the lights simply show different lighting conditions, with the brake light engaged and the left turn signal blinking.
Most of the time I think I caught that signal somewhere around 2/3 brightness or less; it's hard to be sure.
If I'd been clever I'd've temporarily just hooked power directly to the light, bypassing the signal flasher, but I didn't think of that until just now. So the light amount varies from image to image--but it's so bright at this range that it's hard to tell.
The pics start out with a 15W CFL in an overhead light fixture on, plus the camera flash. I turned off the flash, then the overhead light, so that you can see the lights in different conditions. They light up the room pretty well, perhaps a third of the light given off by the overhead, including my CCFL headlights.
Another big change I made was to move the third battery from the top of that rack down to the middle triangle formed by the two bikes' intersections, above the motor.
This radically changes the balance of the bike, and it's handling improves enormously. Now, along with the forward shift of weight from having the batteries on the trays in front of the pods instead of *in* the pods, not having the lighting batteries on there (they were in the pods, too, recently), this change gives better steering at speed, and makes a more relaxing turn possible, with less white-knuckling when taking turns faster.
Used to be that the front wheel *could* skid during the turn, causing me to make a larger radius turn than I should have to, because all the weight at the back kept me from getting enough traction in front, unless I slightly squeezed the brake during turns to force the front end down some. Hitting bumps during turns sometimes made for unpredictable behavior.
Now, it doesn't do any of that. It might still do it if I have heavy cargo in back, especially on top of the pods, but for now it's fine.
You can also see the chain clearance to the battery is pretty narrow, but it's enough. The battery is not clamped down or anything yet, but it's in there prett tight. Took some doing, figuring, and putzing around with it to get it in there at all. :-) Now I need to find more of my big hose clamps to secure it and the other two batteries in place. Since the one I had holding this to the rack isn't quite (by about 1/4") big enough to work on the front battery, I put it on the leftside underseat battery, clamping both holder rack and battery to the cargo pod frame.
After I added the lighting to the leftside battery, it does run down a little bit quicker than the others, so I am making it my new starting point for the Sorenson, with the other pair on the wheelchair charger, then swapping them when they get closer to charging.
As soon as I have some money (yeah, right), I'm going to order some of the VoltBlocher PCBs so I can build a set of three for this pack. They basically only affect the charging when a battery goes over the limit you set in the VB. Then they shunt that extra thru large power resistors as heat, so that it does not overcharge and destroy a battery that's already charged more than the others in a string.
Then I can leave them all always hooked up, and just plug the battery main plug into the Sorenson's test input, which I would just set to a high enough voltage to charge them all. Or a better supply than even that once I can make or find one.
The next step in the cargo-hauling improvements is going to be to move both cargo pods up about an inch or two, so their tops are just above the top of the tire, meaning anything laid across them will automatically clear the tire. Then the rack will be levelled out and made flush with the tops of the pods, to just clear the tire.
Then I can flip that rear seat support so that it makes a top bar for the entire seat. It's only hose-clamped on, so it's easy enough to move around. But with it up there, I can then attach a headrest to it and relax a little more on the rides, at least when I'm testing the motor stuff out and not pedalling.
Wednesday, August 26, 2009
I didnt' get anywhere yet on the pedal freewheel, because something is sort of nagging at me about it but I can't figure out what yet. Safer not to start it till I do.
So today I just did a few cleanup things, such as putting the 2QD in a smaller case (the one I had was just so big that there's no good spot on the bike for it).
I also decided to test it out with 2 pairs of smaller TO220 Fairchiled MOSFETs as described in a previous post, instead of the NTY100N10 on each leg of the half bridge. They'll be much lower RDSon this way, so should stay cool even with a small heatsink, with the airflow I can generate near the rear wheel. I have a few of them from various things, so we'll see how they work out. If they blow up due to voltage issues, I'll put the others back on instead.
So there's what it looks like now, with the four smaller MOSFETs directly board-mounted, bolted to a heatsink pulled out of a dead PC power supply. It's small, but may be fully sufficient, since the other ones barely even got warm from operation on their heatsinks. Even if this one gets fairly hot, it should still be safe to run for testing for a while.
I wanted to use an old modem case that was made of aluminum, but I can't find the thing now.
But I remembered I had some similar-sized old Pactec enclosures I got from TriTek many years ago (they're not around anymore), when I was still a student at DeVry. All I can remember is that they were part of some super-deal of a grab-bag sale, and I thought I would use them all up quickly, but only ever used a couple.
I guess I've had these laying around for almost 20 years now, time to finally use one of them again. :) I drilled a hole *exactly* the same size as the OD of the main cap, since it's a lot taller than the case. I actually want that cap out in the air, because it gets more than warm doing it's work, and if it can be cooled a bit by airflow it will last longer.
Halfway installed into the case, you can see the directly-soldered on motor and battery wires, which lead to connectors outside the case. The throttle plug I didn't use an external connector for (not enough time today to dig around for one), so it's run right from the throttle/key up on the bars down into the case, and plugged into the 3-pin header on the PCB (uses the same connector as a PC case fan). When I have more time, I will cut the connector/wires off a dead case fan, desolder the connector for a fan from a dead motherboard, then make an extension cable that will stay as part of the controller with the external connector available for the throttle. Then I can take it off easily when I want to service it or whatever.
This is the fully enclosed 2QD hooked up to the bike, but not mounted yet.
The cap looks dumb but it should stay cooler, and wouldn't have fit in any other enclosure I had, anyway, except the one that's too large to fit on the bike properly.
It now fits neatly under the seat/cargopod crossbars. It's just ziptied for now, but I'll use a radiator hose clamp once I find one large enough in my junk.
It runs fine like this so far, though it does get warmer. I went around the block and it held up ok. We'll see about a longer trip tomorrow when I go to work. I'll just head out early enough that I have time to just pedal if it blows up or something. :-) I'm way too tired to go out and test it on the road right now--I'd probably crash.
One more thing you can see in this pic if you know what you're looking for is the lighting wiring.
The white wires to the black UPS battery in the tray go to the lighting system. I finally decided that the extra 7-14 pounds I was carrying in the one or two smaller SLAs is too much, and just hooked it up to this part of the traction pack for now. It makes a difference to the bike feel, not a lot but definitely noticeable not to have the other weight there.
While I was at it, I found one radiator hose clamp large enough to go around the battery that's on the cargo rack, but I forgot to take a pic of it. It's now secure enough I have no worries about it bouncing off during a ride anymore. Still gotta find some for the two on the white racks.
Also thinking about moving the cargo rack battery down to the midships area where the controller box used to be, where the two bike frames meet above the motor. Not sure it's quite big enough space, though. If it is, it'd improve the handling even more.
Another part of detail cleanup was to add the brake cutoff for the controller. All it is is a N.O. reed switch (under the foam tape sandwich protecting it, horizontally near it's bottom edge), wired in series with the throttle V+ wire (just like the keyswitch is).
Then a magnet off an old CompUSA name badge holder on the side of the head of a stripped-head bike-accessory screw.
I had to have some way to hold the magnet "upright" so it's field would activate the reed switch, and the smallest bit of steel I had just laying around that didn't have sharp edges I'd have to file was that screw (and others like it). I ziptied one end of the screw, played around with the positioning until squeezing the brake lever just enough to begin engaging the brakes also cut out the motor. Once it was adjusted I added Gorilla Glue with little moisture around it to secure it in place, then the zip tie can come off with no worries about losing it on the road.
That screw doesn't just give the magnet a handy place to stick upright, it also is doing something to shape the field, because without it, I can't get the reed switch to reliably operate for *on* unless the magnet is so close that pulling the brake lever doens't give enough distance to go beyond the hysteresis point of the reed switch and let it turn *off*. With the screw, it works at a nominal distance just fine.
A third thing I actually added a few days ago but forgot about was this little door-holder.
I dont' know what it was originally from, as I found it laying on the ground. It's got two little clips, one on each end, and a weakish long spring between them. I simply clipped one end to a hole already in the top cover, and the other to an existing slot in the side cover, and the tension of it holds the cover open no matter which way the bike leans when parked (it rests on the edge of a cargo pod, since I never put the kickstand back on), even when it's really windy.
It also helps hold it closed, although i don't particularly understand why.
Since it was there, I also took a pic of the repaired Sorenson power supply that I use to finalize the battery charge now that I have to swap the real charger around from pair to pair (it being for 24v and me now having a 36V pack).
It's current limited, so I can set it for 14.4-15.0V (per the battery's label for cycle use) and charge for a while first at the full 1.5A it can handle, then cut it down to half and then 1/4 of that current, as each battery gets closer to full charge (13.6V unloaded after sitting an hour or so off charger).
Kludgy and operator-dependent, but it works for now and only takes a moment to setup and change around, every so often.
I was trying to figure out how much power I am using in my 5-mile work trips, but I'm not exactly sure. The 24V charger (nominally a 3A charger) charges the first pair (A & B) for about an hour and a half at 2amps fading down to .25amps somewhere along the way (I tried to stay and watch it but got pulled away by the dogs every time so far). Then the uncharged one (C) plus one of the first pair (A) are hooked up and it charges for around 20-30 minutes at 2A, then quickly fades out to nothing, leaving C barely recharged and A closer to fully charged. Move it to C & B, same thing, maybe a few minutes less at 2A.
Moving around in pairs like that I let it top off as much as it can, but only takes a minute or less for the 2A charge to stop whenever A or B are in the loop.
So I use the Sorenson to finish charging C, which by itself sucks the 1.5A for maybe 30-40 minutes or more (again, got pulled away by the dogs), and then the battery voltage starts to catch up to the setting on the Sorenson and current drops way down to around 300mA or less, where it tends to stay until I disconnect it.
Unfortunately, with all that shuffling around, I'm not sure how to calculate what power I'm actually putting back into the pack!
I discovered that I don't have the right parts or tools to do this as I had thought I could at the end of the last Pedal Freewheel post. All the screws, bolts, or threaded rods I have that are long enough and thin enough to be welded to the inside face of the crank arm's core don't have any nuts that will fit! Anything I have nuts for is either too short or too large a diameter.
Worse, however, is that I forgot about the face of the BB bearing cup/nut, which sticks out far enough that despite having that small clearance, only has it because it is smaller diameter than the inside face of the freewheel/etc. So I could fit the plate, but not the boltheads or nuts, thus the idea is unworkable with anything I have on hand.
All is not lost, however, because I had a fortuitous accidental discovery. As I was dejectedly spinning the freewheel and hub piece around on the BB spindle first one way and then the other, the threads on the freewheel engaged the threads on the BB bearing cup!
They are the same diameter, threading, etc!
I pulled out the only "spare" BB bearing cup I have, and it happens to be the same diameter, and it is wide(deep) enough to give full-width support to the freewheel (unlike the hub, which only engages about half of the FW's threaded width). The bearing cup is 30mm inside diameter, just a bit smaller than the outside of the crank's core, so if I lathe the outside of the crank to match that, it'd slip right over and everything would fit perfectly. But if I lathe it down, it'll just be a slip-fit (even if it's a tight one), and would almost certainly come off or just spin in place once I really lean into the cranks on hills and whatnot if I ever have to.
Since I don't want to weld the cup to the crank, I can use splines to transfer the power. If I either just file away the unwanted diameter of the crank in places I don't want splines to be, and then file corresponding notches in the cup's flat cylindrical surface (the part that doesn't actually get used inside the BB) to the ridges on the crank, then it should transfer power well enough without further attachment. Given the hardness of the metal on both pieces, I'll probably have to use the Dremel for the majority of the work, and then file to get squared edges/corners later, or it'll take weeks to make. :)
The only catch is that the bearing cup has no outer retaining ring built into it, and I don't think the locking ringnut that normally goes onto it on the BB will fit here, unless I grind off the hexnut outer portion of it used to tighten it into the BB. I'd rather not modify it in any way I can't reverse, since I may need to use this part on the next version of this bike, what with not having been able to get any more scrapped bikes for a long time now.
So I *could* weld a couple of tabs across the flat outside of the hexnut area, and later grind them off if necessary to reuse it for it's normal application.
Or I could drill a hole laterally thru a couple of the hex nut's faces, then press fit a pin into that that would protrude just enough to prevent the freewheel from unthreading itself beyond the edge of that face. I have several pins that are just long enough for that, removed from the wheelchair motors' power-brake-lock that I am not using on the bike. This is probably what I will do, assuming any of my drill bits are hard enough to make it thru the bearing cup's hardened metal (probably not).
So I think I have a solution, and will ponder it overnight in case something else crops up that kills the idea or I get a better one.
EDIT: I've found that (naturally) what I discovered is already known to others, as exampled in this thread on Endless Sphere, and this thread too.
Monday, August 24, 2009
Now that I am adding a freewheel to the pedal cranks, I'm seriously considering disabling the freewheel in the rear wheel cassette, so that I can get regen on the motor, and use the motor itself to help brake the bike, as well as recover a small amount of power.
I would probably also want to put a kind of clutch into the motor drivetrain, so that I could still coast on flats or down slight grades without running the motor but also without triggering regen braking. It'd be of a type that is electrically controlled, and on all the time except when I trigger the "cruise" mode to free it up.
I considered the clutch from the air conditioner compressor in the parts Ford LTD, but that operates the opposite way I want it to--only engaged when power is applied. Maybe I can reverse that, but I'd have to take it apart first to see how it works as-is.
Disabling the freewheel shouldn't be that hard, but I don't want to do it in a permanent way if I can avoid it; most likely I will have to simply sacrifice the freewheel permanently to the experiment, and weld it together.
I have a number of them around, but only the one on the bike has 7 chainrings on it (except for the free*hub* that's on the DayGlo Avenger) , and I don't think they'll fit on any of the others that have 5 or 6. So for the experiment I would have to use one of the 6-ring units, and simply not have all the available gears I've got now. Not too big a deal with the motor on there, but having more gear ratio choices is certainly helpful for pedalling should I need to do solely that at some point.
Rather than the foot pegs, I decided to add a freewheel at the pedal chainrings. Now, these things exist already, but I've never even physically seen a bike with them (only pictures). There have been DIY ones before, some of them doing something a bit like what I'm doing, but they were on the right side of the bike, which would make it easier. My pedal chain is on the left side, so it's tougher.
If I had a steel crank on the drivetrain input I'd do this back there, instead, which would again make it easier. But it's aluminum, swaged to the steel chainrings, so I'm afraid if I weld there, I'll destroy (or at least weaken) the swage to the crank which would make the whole system fail, since the motor input is also there. At least if the pedal output section fails during testing this idea, it will only leave me unable to pedal, but the motor would still work. Redundancy. :)
The pic below shows the parts used:
The crank without a chainring on it already will be used for this, so I can leave the other chainring intact in case of failure, and swap them back while on the road if I have to. I've done a little shaping of the area around the square-taper hole to better fit the freewheel/adapter, and to ensure clearance with the bottom bracket of the adapter later on. Hopefully it hasn't weakened it too much, but only time will tell.
The freewheel on the right is a fixed-gear freewheel, to which I'll bolt a chainring with as close to 43 teeth as I can find in my stuff, to match the 43-tooth ring on the other crank I'd just been using. The freewheel is threaded all the way thru from one side to the other, so it can be flipped over to use it in reverse of the normal action or be used on the other side of something.
The left half of a rear hub that's sitting near the crank is the unused part; I only need the ring with the freewheel threads on it, in the bottom part of the pic.
That bit will have the freewheel threaded onto it, then will be welded to the crank.
The other bit there is what's left of the bearing cup/race from inside the threaded section of the hub, which is in the way of doing what I need it to do.
This is a pic of just those latter two parts.
I would *prefer* to weld the former spoke-hole ring to the crank, but if I do that, the threads will be facing the wrong way, and then it will unscrew itself as I pedal. That's why I wish I could do this on the receiving end of the pedal chain; if I had more steel square-taper cranks I could.
This is pretty much what it will look like when attached:
That's a view as if you were looking *thru* the bottom bracket at the inside of the crank.
An oblique-ish view:
A "top" view, showing the spacing.
There will be about 1-2mm between the outermost part of the BB cup threads/nut/etc and the innermost edge of this adapter, once the crank is tightened back down.
The real catch is the welding on of the adapter to the crank. I'm afraid it will end up warping the threads, or damaging the freewheel. The threads might be irrelevant, because once it's welded on the freewheel can no longer be removed anyway, without cutting the adapter off.
What I might end up doing is welding it on by the spoke ring anyway, even though it could unthread. Then use a tack weld across the threads to the adapter and the freewheel to hold the freewheel in place against pedalling forces (which it probably wont' actually do if I had to pedal full force without the motor, but since I'll only be pedalling if I absolutely have to for these tests, and only minimally, it should be ok.
I can still dremel out the tack weld and unthread the freewheel if necessary (for instance, if it breaks).
But I'd rather figure out another way. Perhaps loctite or something similar. Probably insufficient.
There is a possibility that I could weld pair of small bolt to the crank itself, to either side of the square-taper hole, then use those to bolt a plate against the inner edge of the freewheel that would then prevent the freewheel from unthreading itself. It's the most repairable solution, but I am not sure I can find bolts small enough to fit.
Sunday, August 23, 2009
I think for a little while, I'm going to bolt on some foot pegs in front of the seat on the bottom edge of the frame, so my toes are just behind where the pedals circle around (they move when the motor runs), so that I can do some serious hard-testing of the system without any pedal input at all, and be sure that I don't "help" the system by unrealizingly pedalling (since I'm so used to it).
I'd like to test it to breaking if it's going to, while I am on shorter trips that aren't time-sensitive (so I can pedal home with all that weight if I have to).
The end result of the system will be to have a pedal-assist that *requires* some pedalling, but not a lot, but at the moment I am more interested in breaking all the stuff I can before I rely on it. ;-)
I asked this question over on the DIYElectricCar forums, where there are a LOT of very knowledgeable and helpful people, and I'll post the gist of the answers I get in a later post. I've already done some searching around the web before asking, but my google-fu is not working well these last days, and hasn't come up with very much relevant info, and really nothing about what I am considering trying to do. Many things about doing the opposite (which I've already done myself), just not this. That might be a hint that it's not worth doing. :-)
I'm sure this is possible to do, but I'm not sure how I'd go about calculating the windings' pattern, number of turns, or gauge of wire to be used.
Essentially, I have those smallish PMDC brushed motors in the form of the wheelchair/powerchair motors. The way I'm using them, they get pretty hot. Part of that is certainly because of the enclosed design of the motor, which I have some solutions for, as discussed in the last post.
Part of it might be, so I've read here and there, because of the PMs themselves, and possibly because of the flux ring (cylinder, actually) around them that constitutes the heavy thick main body of the motor. For a few reasons, including that, I'm considering an experiment in converting one of them to wound-field instead of PM. It would theoretically also give me finer control over the power used in the motor, and it's response to various situations.
The motors are radial-flux, and have PMs about 4" long with an outer radius of around 3", a bit more than 1/4" thick. They're not rare-earths. I don't have any real idea of the magnet strength, but it is fairly high, but not nearly what you'd see in a modern harddisk servo magnet.
What I'd like to do is replace the PMs with a set of field windings for the stator. I actually already have a number of motors around here that are of similar but not identical diameters/radii, which have such windings, but I suspect I could not simply move those windings over to this one and use as-is. (though I *have* taken the entire cylindrical PM assembly from other motors and tested them with some success on former wound-field AC motors to turn them into PMDC motors for experiments). Most of the ones I have were drills and the like, run from 115VAC at a few amps max.
One is from a 115VAC weedeater by Ryobi, and it's windings are the best size match for the powerchair motor armature radius, but still not an exact match. It might be possible for me to heat and bend the Ryobi field windings to more closely match the radius, but it may also damage the insulation on the wire, so I'm curious to know if it is worth trying that. The field windings appear ok, but the armature windings are heat-damaged from overlong use of it in our Phoenix summers. :( That makes it a good donor candidate because I don't think I'll ever rewind it's armature. :)
Now we find out: Is this yet another of my crazy and stupid ideas, or is it just crazy?
Saturday, August 22, 2009
Well, that rubber noise dampener might not be the best idea. The motor and it's gearbox gets too hot to leave my hand on for more than 10 seconds, after my 2.5 mile commute to work with many full stops and starts, plus a few 15-18MPH stretches. The controller itself barely gets warm (I think the sunlight heats it up more than the operation).
Part of the motor's heat comes from sunlight on it's black casing, but most of it is from the trip, because at night I only get two more seconds of holding my hand on it before I have to let go. I'm a wimp, so many people could probably leave their hand on it much longer, if they had to take it off at all. I don't know it's actual temperature. I'm sure it's not good for the magnets over the long term.
Realistically, I think that the motor will probably work for quite a while like this, but definitely not forever--it was designed for quite a load for long periods, but not what I'm putting it thru. :)
I've been considering some heatsink fins around it, secured to it's main cylindrical casing, but it is more likely that I will add forced-air cooling to it by drilling some holes in that cylindrical casing and adding a vacuum-cleaner hose to a hole cut in the flat end of the plastic ex-brake-solenoid cover. The hose will go to a fan up on the "deck" above it, facing rearward and downward, with a filter ring over the holes in the motor casing to keep dust out. The fan will suck air thru the filter, holes, casing, along the motor shaft, then out the fan exhaust. That will keep it at least somewhat cooler, with minimal work and parts added to the bike. The fan will probably just be one of my 12V 5" high-volume PC case fans if I can find them.
If I also add the heatsink fins, it should help even more. I have plenty of aluminum to do this with, from various bits and pieces around here. I even have a bunch of huge heatsinks I could bolt to the flat bottom of the gearbox casing, which would help spread the heat.
Since that rubber pad between the motor and the mounting plate keeps it from transmitting heat thru the bike frame (even though steel is a poor conductor of heat it is better than nothing), I'm probably going to take that off, and live with the noise the bike makes with the induced vibrations and whines in the frame. :roll:
Posted by M.E. at 8/22/2009 11:25:00 PM
Friday, August 21, 2009
I found the battery specs:
Naturally, they don't list any model matching these exactly, as they show an SSP12-18, but these are SSP12-17. Close enough to base any assumptions about it's specs on, though.
On the battery that died in last post's ride, I took a look under the barely-glued-on strip covering the rubber vent caps, and I am going to try adding drops of water into it's cells to see if I can revive it. I mean, I can't hurt it any worse than it already is, right? ;-)
I'm sort of thinking about trying the bike out at 48V, since that (with 4x 12V 17Ah) would have about the same energy density as two of the larger 12V 31Ah U1s as a 24V pack, but should theoretically take a lot less current to get the same torque/speed out of it. That means the batteries would last even longer, because the Peukert effect that causes batteries to supply less total power the faster the power is sucked out of them would apply less.
The motor appears able to handle it, as I don't see any more sparking on the brushes at 36V than 24V when I watch it in the dark, so I will probably test it with one of the motors I've got pulled apart right now (the one that had the grease leak).
I wanted to use that 4pole motor on the bike but so far hadn't found any bolts in my stuff that would fit it, except for carriage bolts, which don't have a shaped head on them to turn, just a round-stud end, and a several-inch-long machine bolt with threads only on the first inch or so, which means if I cut it to make it fit without several inches of washers stacked on it, it won't have any threads. And I only had the two total, and need four--two short, even two inches would be fine, maybe less, plus two longer, perhaps 3 inches.
I found some good short machine bolts that will work for the short end of the 4pole motor mount plate. I'll weld a nut to the head end of a carriage bolt and use that to tighten down the long-bolt end of it. 3 bolts should be able to hold it at least for testing. If I find a second carriage bolt I'll use two. I'm sure I have several just like this one, in a box somewhere. I *really* want to see what this motor can do. :)
I could definitely do this higher voltage stuff with the treadmill motor, and I'm still pondering a drop-in drivetrain and motor plate that would let me put the treadmill motor on in place of the wheelchair motor without modifying that bottom plate any further, and would come off and go on as quickly and easily as the wheelchair motors do (which is one thing I really like about them).
One thing I *don't* like about them is that they're pretty noisy. I fixed a little of that by putting a rubber pad between the motor and the bike frame's mounting plate, but noise is still conducted thru the bolts, and I don't have a long enough set of them to use a pad on the bolt side, too, with fender washers and whatnot to keep things from sliding around against that chain tension. The pad itself came out of an old dead Macintosh Plus, from what looks like an optional harddisk bay I didn't have in mine back when I still had it working, a decade or two ago. At least, I don't remember it.
The treadmill motor by itself is a lot quieter, but I suspect most drivetrains I make for it are going to add significant noise, just because I'm not great at machining the parts and mounts for things, so nothing lines up exactly right.
One problem I have is that none of the crank-mounted chainring sets are perfectly round. The rings might be round but if so they're offset a little from center, so there can be as much as 1/8" or more difference in distance from center to edge from one extreme to the other, which means the chain gets tighter and looser and causes more wear and also more noise. Since the teeth aren't 1:1, it also means that as they rotate around they offset their rotation, so the tighter/looser pattern changes over time.
Not only does this cause noise, but it is going to make my tension-based throttle system impractical until I can fix it. As I watch that spring-loaded throttle arm roll over the chain, it goes up and down by almost 1/3 of it's full travel, with no load on the chain at all except this tighter/looser rotation pattern!
I'm not even sure I *can* fix it, because, for instance, the chainring on the drivetrain input is steel swaged to the aluminum crank/squaretaper socket. If the offset is there, I can do nothing about it. If the offset is due to a bent BB spindle/crankshaft (possible but highly unlikely) I can't fix that either, because I dont' have an extra.
For the front chainring, it's not only offset circumferentially, it's also bent around the entire gainring rim just a little bit here and there, so the edges appear to "wobble", making it rub more on the sides of the chain at some point than others (and possibly one day under the right conditions to even lift the chain off the ring, if the teeth ever catch an edge of the chain). It did not start out this bad, so I think the little bending it already had is being made worse by the very high tension forces on it as I pedal hard during startup from a dead stop without a motor on there. Shouldn't worsen more if that's true, now that I have the motor back on.
What I need to fix that is newer and/or better-made square-taper cranksets with the chainring sets on them. What I would *like* if I could pick and choose is a handful of the *same kind* of crank spiders, plus the chainrings that go on them in a good variation of sizes. Then I could pick and choose my ratios, and they'd be stiff enough to not have to worry about this offset and bending happening, hopefully.
Thursday, August 20, 2009
Again, couldn't get to sleep at all, so worked on the bike till way past dawn, then was finally worn out enough to sleep about 4 hours before having to get up for work, so I rode the bike to work as a test.
First, I fixed the "quirk" mentioned in the last post. It was indeed just a zener; I had stacked 36V worth of zeners for my 24V version of the controller, and forgotten that when I hooked up 36V to it. Since that's more like 41V fully charged, it meant that parts of the controller might be at 41V, but the rest of it at 36V (because of the zener protection shunting away the rest of that), so likely the comparator's reference is one of those things that was affected, causing the motor power to be partly turned on even at 0V throttle. I just stacked up 48V worth of zeners instead, and it works fine now. I added an Anderson connector for power while I was at it.
I finished up working out some temporary mounts for these lighter batteries, and moved wires around in the Anderson connectors (they can be slipped out using a flatblade screwdriver if you're careful, without damaging or uncrimping/cutting/etc, to just reconfigure the wiring). This gave me a harness that hooks 3 12V batteries in series for 36V, to give the greater motor speed necessary for the ratios I setup a few hours before.
The mounts are actually from a discarded "power panel" retail display, meant to hold some sort of spray cleaners for a display at the side of an aisle endcap. They looked like decent steel wire frames that I might someday hang on pegboard or something, to use for trays, so I saved them. Now they are battery trays. :) I did not know how well they would work, so I only zip-tied them in place, rather than welding, for now. I still would rather make lockable batteryboxes (once I find some good cabinet locks with keys, or keys for the ones I already have a pile of).
These trays hold one battery each (could hold two 12V/12Ah or smaller, I think), so the third went on my slanted rear cargo rack, zip tied down under the spring-loaded backpack-hold-down. Cabling with the Anderson connectors runs to each one, with each having it's own bolted to it's terminal tabs. The bad part is that nothing is fused yet, with no circuit breaker either, because I did not want to cut the cables at all, and don't yet have a terminal block mounted on the bike where I could safely connect the motor and pack to where I could put fuses and/or breakers.
There's also no charge connector, because I don't have a 36V charger. I'd have to use my 24V charger to do a pair of them at a time. Probably by charging one pair halfway up, then swapping to one of those plus the 3rd battery for another half-charge time, then the other plus the third battery for the rest. It is not a perfect solution, but is the best I can easily do. I can also automate this process by using some of those relays from the UPS, and a comparator circuit to check the voltages across each battery, and automatically flip things around in a "circle" until charged up to whatever set point I find works.
As a temporary option for slow charging, I can also simply hook it up to my Sorenson current-limited bench supply, set it to the final pack voltage, limit it to say, 1.5 amps (it's max continuous rating), and just let it charge all three overnight. Since it's current limited, and voltage regulated, in theory this should charge them fully but not overcharge them; in reality I'd need to do this to each battery individually to balance them correctly. Maybe I should build myself some "Volt Blochers"-style current shunts for each cell during charge (switched in and out of circuit by those relays so only connected during charge).
Anyhow, I had already charged all the batteries up as far as the 24V charger I have will go, since it has a light that comes on when it thinks they're done. Once it finished them (while I was working on the controller and the wiring harness), I just picked three out of the set of 7 (since one only goes up to 9V and is definitely bad). I hooked them up to the bike physically, then tied them and the controlller down, and took it for a spin around the block.
Wow, it works pretty well. Other than the derailers needing serious adjustments (I've switched around a lot of stuff including sprockets and haven't got that far yet), it works very well. I don't even have to pedal at all to get started from a stop, which is the main thing I really really wanted to work. Even if I have it in the highest gear it still easily pulls away from a stop (it might actually be working *better* in higher gears than lower ones). No tire-smoking, but maybe if I had a lighter bike and batteries. ;-) I think it'd probably throw gravel and/or sand on an unpaved canal path.
No video of it working on the road, since again I don't have someone to use the camera while I ride or vice-versa. I did not do any speed testing, as I had forgotten to charge the batteries in the PDA since I last had the whole thing working, before summer. Ooops.
After I made sure it all worked, I put the PDA batteries on the charger and went to bed. After getting up, I put them in the PDA and sync'd it up to put VeloAce back on, reset it to Miles and 192cm for my 24" tires, then set the odometer back to the last place it was plus the standard-distance trips I have put on it since then: 412.9 miles. (some places I go to exactly the same way and I have notes with their distances via trip odometer, so it's reasonably easy to just add in that times how many times I went there). I'm going to guess that half that mileage is entirely under human power, without the motor and batteries on it at all, both before I got the motor on it and during the time I had it all taken off during the long dark repair time of the controller.
I got ready for work, left, and rode around a mile before suddenly it acted like there was a bad connection somewhere, and I could get no torque at all. The motor was spinning, but not pushing the bike. I stopped and checked them all, but it all seemed ok. I had no DMM with me (stupid, since it is a test ride), so I couldn't check a lot of things. I just disengaged the motor clutch and pedalled the rest of the way to work. I had not gotten to the parts of the trip where I don't have to start and stop a lot, so I had not yet shifted into higher gears or used higher throttle speeds, so the max speed it had reached at that point was 13.5MPH (just before the failure).
Later during lunch at work I found it was caused by one of the batteries. I just disengaged the clutch so the motor can run without moving the bike, and run it at minimal speed so I could hear it change if I found a loose connection as I went thru it all again. It would barely run at all; maybe a third of full speed, if even that. Probably a lot less.
Probing around with my fingers, I found that the negative terminal of the righthand underseat battery was VERY warm, almost hot. Nowhere else on the bike was anything remotely warm (except the motor a little bit, after a while). Connection was good, and I took it off and scraped the metal post and tab and cable connector clean in case there was something invisible causing excessive resistance, but no change. Eventually I had to just take the Anderson connector off that battery and bolt the cable's pos and neg wires together so I could at least use the bike at 24V.
After doing that, it seemed ok, but wouldnt' know for sure till I tried to ride home. Worked alright during that ride, and still had decent startup power, though top speed was only about 12MPH. Made it home safely, and am now typing up this post.