As promised, pics (and video!) of the Cieling Fan motor rewired as BLDC.
First up is the raw pieces, showing the brown Hampton Bay motor from 1986 in a partial state of disassembly. It looked much like the other cieling fan motor in the background of the first image, which is a 1995 motor from China, by an unknown manufacturer, for Hampton Bay. I chose the 1986 Hampton Bay unit to start experiments with primarily because it was easier to get apart, having been apparently designed to be serviced, but also because it was marked as made in the USA (though the windings could have been done by a 3-year-old for all I can tell by their messiness, especially compared to the Chinese motor :-) ). I also picked it because it is a rounded case, with thicker metal and no vent holes for water and dirt to enter (unlike the other that has plenty of finger-sized holes), and I might as well go for any advantages it might have being used on the bike. It does have a lot of threaded mounting holes, but that's an advantage, since any I don't use can still have screws threaded into them to seal them up, or silicone if I'm feeling chintzy.
This motor has 9 teeth on the stator, which is a common number, as is 12, for RC hobbyists to pick to rewind into BLDC's. I'd rather have had a 12-tooth version, as there is a variation on winding called LRK that gives better efficiency, but I'll have to make do with what I have in hand. I don't like the open bearings it's got--they have no cover plates to keep dirt and dust out, and I have no way of pulling them off and replacing them with different ones (even if I had others to do this with right now).
Here's an image from during the unwinding of the outer coils, showing the old RadioShack wire spool I was putting it on. It barely fit; by the time I was done it was bulging over a bit, since I didn't wind it tightly (didn't want to risk stretching the wire; it's pretty thin).
The Chinese motor is below, though I haven't done much to it besides open it up to look at it. That was tough, as they didn't make it to be serviced, and I was afraid I'd have to damage the casing to open it. Fortunately, being very patient and gently pulling the case halves apart with two wide-blade chisels by rotating and rocking them as levers on opposite sides of the case, over about 30-40 minutes, eventually opened it without damage.
As you can see here, with it on my "test rig", it's got a different way of winding than the 1986 motor--every gap has been used to wind on, where the 1986 motor only used every other one, since the smaller gaps on 1986 were only so the inner circle of windings could be installed. I have no real idea why it's wound differently from the other one, but since it is still an AC motor with those windings, it's irrelevant, since I must unwind and rewind it differently to use it as BLDC anyway.
Something else you can see here if you look carefully is that one of the bearing case covers (which the 1986 doesn't have) is dented. That's probably why it was in the junk box of fans in the first place, since it causes it to rub and make a bit of noise every rotation--probably got annoying in the middle of the night to whoever had them originally.
The test rig itself is just a couple blocks of wood with two of the fan blade mounts screwed to it with some of the fan case screws, and a long thick nail inserted thru the shaft hole (it's hollow for wires to run down to the lamp and switches, remember?) to hold it up, to allow the rotor bell to freely spin without me having to hold the thing up all the time (it's a bit heavy, perhaps 6 pounds or more). Since it doesn't clamp the motor shaft down, both the rotor and the stator can spin, which is a problem as you'll see in the video below. But it did let me test a theory, and it was very quick to throw together out of parts already laying there from the fans. Only thing I had to step away for was the block of wood, just around the side of the house outside. The two-minute test stand. :-)
For this test, I did not yet rewind the 1985 motor, I simply cut the loose wire between each of the inner windings, so I could temporarily change the order they're hooked up in (which for AC was just series circumferential), to put them in the Wye configuration. I didn't do anything fancy, just lap-solder some wires between the appropriate winding ends, to give me ABCABCABC for the pattern.
Then, I used 6 harddisk magnets placed all in the same polarity around the circle (you'll see some appear backwards, but they're not--they're not polarized front-to-back, but rather end-to-end on the same face, which makes them poor candidates for motor magnets). I'll get better magnets before I actually make this a motor for the bike, but it's all I have right now. They're of course just close to where they should be, but since they're all different strengths and sizes as well, it's irrelevant how I place them, since I only need to see if it will work *at all* for this test.
I haven't had time to build a controller yet, but as I was digging thru parts bins, I found both a dead 5.25" floppy drive and a mirror-scanner assembly from an HP laserjet. Both of them have controllers built in to them, as single-chip types. Of course, they're nowhere near the wattage I need to run the motor I will make out of all this, but they will both run this test-stand version long enough to verify the idea. Both can run on 12vdc, with just an enable line held low on the 4 wires coming off of each one. I think the 4th wire is a "motor is at speed ok" signal, but I don't care, since I only want to see it spin at all. In any finished controller for this, I would not have a set speed anyway, it would change all the time so such a feedback would be nearly useless to me (unless I had the whole bike computer-controlled, which might happen some day long from now).
Since I couldn't get the FDD motor off to access it's hall sensors (they're under a metal plate that's held down with some really soft and tiny screws, probably locktited in place, which I stripped out thoroughly trying to undo them), I went with the easily-disassembled HP controller board. The HP board has a different and lower-wattage chip on it, but it is very simple to wire to the motor, once I carefully removed the motor that was on it. This also left the Hall sensors exposed so I could simply hold the board up in the magnet path, rather than having to unsolder the sensors, glue them in place on the stator teeth in a position similar to the ones on the board, and run 8 wires from the three sensors' 12 pins total back to the controller (4 pins are simply chained together between the sensors). Big time saver for the test, though of course it can't really be used properly like this for any real work.
Now that you've suffered thru my rambling, here's the video of it actually working, only a bit over a minute. I was mumbling to myself, really, not expecting the camera to be able to pick me up over the heater fan in the room (the central heat failed just as it was getting dark today, and even though this is Phoenix, it still gets mighty cold mighty fast in this old house). The camera itself is the same one I take the stills with, a Sony DSC-50 I got really cheap at the CompUSA closeout when they shut down here back in May, because they had it marked as defective. It wasn't defective, just missing it's charger (which I found later in a bin of assorted adapters and junk, which they were gracious enough to give me for free).
Saturday, December 29, 2007
As promised, pics (and video!) of the Cieling Fan motor rewired as BLDC.
Friday, December 28, 2007
Since I can't afford to buy a motor, and fixing the one I have may not be possible for the time being (as I don't have the right thickness of wire on any other motor to unwind from and rewind to the failed one), and none of the other DC motors I have is anywhere near what's needed to run the bike, I finally decided to build one, or rather, rebuild an AC motor into a DC motor.
I don't have any brushed AC motors that could handle enough current and/or have the right size or shape or mounting points on them to be able to use for this purpose, but I do have three fairly hefty cieling fan motors, each of a slightly different design. The best one is a Hampton Bay motor from 1985. It's made as a brushless AC motor, with an outer ring of staggered ferrous elements embedded in a 5.5" solid ring of nonmagnetic material (probably bismuth), which is friction-fit into the rotor "bell" that the blades bolt to, and a 9-tooth stator inside that is about 4.5" across, with two layers of coils, one with less windings than the other and also farther inside the stator (away from the outer ring).
The way it originally worked, the outer windings were series-circumferentially wound, all clockwise, and run out to a pair of wires. The inner windings were done the same way, separately from the outer set. To get low fan speed, only the inner would engage. To get medium, only the outer. To get high, both would engage (done by the switch on the lampshade section, or a wall control if you had one). Reversing it would require switching the direction of the AC input to the coils, which I guess changes the phase relationship to the outer ring staggered segments, causing reverse rotation (guessing).
The way I need it to work will be as a 3-phase, 9-tooth, 12-pole BrushLess DC motor (BLDC), run from a different, more complicated kind of controller than the one I need for the regular Brushed DC motor, of course. Fortunately, there are lots of RC Aircraft DIYers who have been rewinding CDROM (and similar) motors for years to do the same thing. (except that CDROM motors are already BLDC 3-phase, as are HDD and FDD motors. Case fans are also BLDC, but all the bad ones I have taken apart for their Hall sensors were 2-phase rather than 3, with only 4 teeth and likely very few poles, making it a lot easier to control with a very simple two-transistor circuit.
For what I have to do, if I had the PIC or AVR programming equipment (some of the PIC stuff is super-easy to build, so I don't really have an excuse for not trying it, except for not having any PICs), I could use one of the many freely published designs (including software) that have been made for RC Aircraft or Boat control, and simply upscale the power-output stage for my motor. But since I don't have the PIC or AVR equipment or any of the actual uC's to program, and no money to buy any, I'll have to design my own made from parts I already have here.
Now, I have a lot of stuff in various "dead" equipment, as the last post explained, but I don't have everything needed to just quickly adapt something for the task, because it's kind of complicated in how things have to be turned on and off, so that the batteries are never shorted out, and the windings are turned on in the correct sequence and at the right times for the right amount of time, based on how fast the motor is spinning. It's not simple, at least not for me. Especially considering that there are several possible ways to choose to wind the motor. I also have to calculate how many windings of what diameter wire will get me the torque and speed I need. More windings = more torque, less windings = more speed. I need torque way way more than speed. Also, the more powerful the magnets on the outside, the more torque, and the less current flow there is, making the motor more efficient.
I actually have a basic block diagram on a napkinsketch, but don't yet know even what parts I need to use to create the unit from with those blocks. It's a fairly simple idea, but will probably rapidly get more complex as I go. Starting with the basic Y-scheme (Wye) where all three windings (two each of A B and C) are connected together at one end, and the other end of each brought out as a single terminal for the motor to run from.... Basically, all I have to do is shift a 1 around a 3-output ring counter (like a 4017 used as "count-to-n"), then invert that output and use the two "zeros" that are now "ones" to turn on two of the windings at any one time (A&B, B&C, or C&D). That is what sequences the motor, "enabling" each power driver section in turn. The clock input for this is driven by the Hall sensors that are verifying the position of the rotor on each rotation, by sensing the change in magnetism between poles of the magnets attached to the rotor. The faster the Halls detect change happening, the faster it clocks the sequencer, which keeps it in sync with the motor speed. If the motor is forced to slow down, by new load on it or whatever, the slower the Halls will signal and thus the slower the rotors will be powered, to keep the whole thing syncronized.
The actual power control is still done by good old PWM turning all the pairs of MOSFET's on, with high and lowside drivers for H-Bridge type control, only 3-way instead of two-way like the Brushed DC motors could use (though for a different purpose).
The throttle will still change the PWM duty cycle, higher for more power, and lower for less. The sequencer above will simply enable or disable each pair of power output sections as needed to drive the right pair of coils in the right polarity, so they don't short out the input power (battery) to ground.
It sounds complicated, but it also sounds easy. I'm not sure which it will finally be. I *am* sure I will get some smoke before I am done with a prototype, though. :-P
Now, the good news is that for a temporary test unit, I have found an old HP Laserjet scanning mirror (that used to draw the images on the toner drum to be transferred to paper to pick up toner to get melted onto the paper) that has an integrated controller chip on it designed back in the 90's specifically for 3-phase small BLDC's. This one, unlike an earlier one I found on a 5.25" floppy drive, has an option for a non-crystal clock input, so I can vary it's speed. The other would not be variable, and I need that for testing the motor. Now, this chip can't handle more than about 8 watts, but I should be able to use it to drive MOSFETs that *can* handle my motor's power (which I do not yet have any idea how much it will be). It also is made to run at 24V, which is good, as that's probably the voltage I'll test the system at. It's going to take a while to modify the circuit to work like I need it to, but i don't have to build the sequencer or other stuff--this has all that built in; I just have to clock it, hook it up to the Hall sensors I will need to install on the stator, and hook it up to the power output section I'd have to build for *any* BLDC controller I'd be making. Hopefully I can install the controller chip and everything but the MOSFETs inside the motor casing--I'd like to put those in there too, but I don't think I could fit it in along with heatsinks, and because the case will be rotating around the motor, I cannot bolt the heatsinks to the casing!
I still need to actually build the motor, whcih at the moment has it's first outer set of windings removed, and temporarily rewired the inner set to be Wye ABCABCABC (for 9-tooth 6-pole) instead of the series-winding it had been as an AC motor. I put HDD magnets (which while very strong are permanently polarized thru the wrong axis to use for this, really) on the rotor bell (case) in the appropriate configuration (NS NS NS NS NS NS), spaced as evenly as I could, and used just a row of wires and a set of contacts to make a manual commutator, and rubbed the wires from a battery to that, and got it to spin very slowly and jerkily after a fashion. Not bad for "digital" operation :-P
Also, it has enough stall torque at 24v when just solidly energizing a set of coils that I cannot really budge the stator and rotor apart from whatever position they are in. Keep in mind that's with the really badly/loosely wound coils as they already were when it used to be an AC motor--I did nothing so far except cut the inter-tooth connections and reconnect them into the above Wye configuration, and they are also very far away from the outside of the stator, and the magnets being used are polarized ineffectively for this purpose, and there is a HUGE airgap between magnets and stator (perhaps 3/4"), since I am placing the magnets directly to the rotor bell's inner surface, and they are nowhere near thick enough to come close to the stator's outer edges. I would like to find a usable perfectly round and centered ferrous ring I could use in place of the orignal, and put the magnets in or on that, but I have nothing of the sort, and no tools to make one with. So instead, I am going to probably have to find very thick magnets somewhere, preferably neodymium, and preferably arc-segments, but so far I cant' even find any usable arc-segments for this motor on the web anywhere, unless I want to order a few thousand from China, where they will *make* them exactly the way I specify. I can't afford to do that.... Especially since I don't know if this whole thing will even work out.
It's difficult to do this stuff, but it is actually fun figuring out ways to do it with stuff I already have. :-) Unfortunately I don't always have the right thing to finish something, so I end up putting a lot of work into paths that I have to abandon due to lack of materials, but it is still fun to try, and to engage my brain into thinking about things in ways I had not done before.
Wow...I'm going to have to come back to this post later and add the URL's where I got my information, and pics of the motor work so far. Probably tomorrow, after I get some sleep (somehow, it's 4am, and I am wiped out).
Sunday, December 23, 2007
I had decided that to do some more testing of ideas, such as throttles, I'd have to actually have a working controller, so thanks to someone on a forum for scooter/bike info, I got a rough reverse-engineered schematic of the smoked Electra controller off the dead scooter I have, and that let me figure out what parts used to be filling those empty burned sockets. :-)
Once I knew that, I dug around in my old dead-boards boxes, and found a bunch of old motherboards, including an old Compaq Athlon board (from back when Athlons could burn your hands if you touched the heatsinks, and came in SlotA packages similar to PentiumII's), which had some good-enough-for-this-purpose MOSFETs, diodes, and resistors. I had to take a couple of dud PC power supplies apart for their AC-side capacitors, though, since none of the PC-side caps in them were any good (and weren't high-enough voltage ratings anyway), same thing on the motherboards.
I also took off dozens of discrete logic chips, assorted op-amp and comparator chips, other analog type chips, medium-power transistors, caps, resistors, etc, off all these boards, which will probably be useful during the design of various parts of the bike's electronics (such as battery chargers for the Li-Ion setups, turn signals, lighting controls to be run by PWM and/or other types of charge-pumps to keep them as bright as possible even as the battery runs down).
After a couple of retries (I missed a dying driver transistor the first time, and a diode killed by the overload caused by that the second time), I got the controller working, though I need to find a way to mount the outsized caps closer in to the PCB, because the extra lead/wire length is causing them to get very hot. I don't relish exploded capacitor all over the room during experiments, so this is an important thing to fix before continuing further. But it does drive the motor, and the Hall-effect sensor the scooter had for it's throttle works to control the speed.
The relay that is used to switch current to the rest of the unit past the "ignition switch" is unfortunately melted inside, from whatever caused the original meltdown/smoke of the controller before I got it. The contacts for the relay were welded together, and distorted from the heat. I pried them apart, but could not straighten them well enough to make them work properly without pushing on them with an eraser (otherwise it arcs trying to connect, then just re-welds itself). I need to just replace the relay.
Fortunately, one of the old HP laser printer boards I have has a control relay on it that can handle the current/voltage, though it's a problem that it's contacts will not line up with the original relay on the PCB. That means more wires, and heating problems, most likely. Will still work for testing, but I don't think I can depend on this controller very long.
Now, the throttle itself is physically broken, with the plastics coming apart and cracked, so I'm going to have to build a throttle; this one won't survive even if I repair it. I took the HEsensor out and verified it's a typical type. Then I began rummaging thru various PC case and CPU fans with bad bearings and/or broken/chipped blades (I've gotten a lot of broken stuff like this from PC's other people scrap out or give away, because it's still very useful inside), until I found a few that use a regular 3-pin HEsensor just like the one in the throttle, with an analog level output (some HEsensors in fans are latching output or comparator output, so can't be used for throttles--they only need to detect the passing of the magnetic pole in the strip magnet wrapped around the fanblade core of a brushless fan motor, to trigger the next pulse that keeps the fan spinning, so it's just about as common to see digital outputs on those HEsensors as analog ones, in older fans. Newer fans probably all have digital outputs, but all the new ones I have still work, and I'm not taking them apart to check. :-P ).
So now I have 3 more HEsensors to do throttle-design experiments with. I think the first one to do is the glove-controlled one, as it's got no moving parts, just some experimenting with distances, spaces, and angles of mounting for the magnet and the sensor.
Sorry no pics at the moment, though I will probably take some of the donor boards in their stripped-down lack of glory, and the pile of usable parts from them all. When I do, I'll add them to this post.
It's always fun to take things apart; even moreso when I don't have to put them back together! :-P
Friday, December 14, 2007
Now I have a "bike computer" courtesy of an old discarded Sony Clie (PEG-S360)
(sometimes it randomly gets a "database error", no matter what you're doing, guess that's why it was tossed), a free program called VeloAce,
and a few minutes of soldering the IR version (InfraRed) of the wheel-counter circuit together from parts I already have laying around will complete the assembly later tonite or tomorrow. I've already tested it with a remote control pointed at the IR port to verify it counts pulses ok.
Since I didn't have the cradle or cables or charger for the Clie, I had to do a bit of disassembly so I could reach the battery to put a charger on it for testing (currently just an old Nokia celphone charger). I reseated all the connections in hopes of curing it's database error message, but that didn't cure it. Doesn't really matter, as it doesn't affect it's use on the bike--mostly I want the speedometer and odometer functions anyway.
I had to use IR to transfer the VeloAce program to it, since I don't have the cable, and for that I had to fiddle with an old sort-of-mostly-working Compaq laptop, since nothing else I have has IR in it. I've got a USB IR unit from some Sony desktop that had GigaPocket on it, presumably for the Gigapocket "TV remote", but there are no drivers *anywhere* for it, so I can't use it! Sadly enough, I do also have the restore kit of CD's for that specific Sony in my restore kit library, but of course I cannot extract the encrypted files from them without restoring an actual Sony desktop of that specific model. :( If I *had* that model, I would copy the files from it, and wouldn't need the restore kit. Sony support doesn't even answer my questions about it (I tried years ago when I first got it, and I tried again the last few days, hoping for some answer, but nothing at all, which has been typical of support requests from Sony my entire PC career--great products as long as they work, but if you need help, well, you're probably screwed). Doesn't matter since I got the laptop working well enough to do the transfer--unless the program gets lost off the PDA now, I don't have to worry about needing IR again anyway.
I haven't mounted it to the bike yet, as I'm still figuring out a good mounting method that will allow quick removal but also won't fall off and is rainproofed, but still lets me access the touchscreen. Otherwise, if I left it mounted when it's outside somewhere unattended, someone would either break it or steal it thinking it was worth something.
I'm testing an even simpler version of the IR circuit I've used before for other things, and spent a few minutes drawing up,
but I don't know if the battery will last as long if I use it (just uses a CR2032 watch battery, like most motherboards use for CMOS/Clock backup--that's where I got it from, actually, along with several other parts).
Posted by M.E. at 12/14/2007 09:42:00 PM
Tuesday, December 11, 2007
Well, I keep saying I'll post pics, so here are a few. First up is the Plan A 1/2 (version 1.3.1 now), using my Columbia aluminum frame bike as the base, with the portion of the wrecked steel Schwinn Ranger attached to the back end, in reverse, at the rearwheel axle points.
This is the "overview" of the motor drivetrain, with the wheel chainring cassette at the left, the derailer (currently only being used as a tensioner--it can't work the way it's designed on the left side yet as a derailer, I must first rebuild it, or build one from scratch, in mirror image) in the middle, and the motor's chainrings on the right. Currently no motor is attached, but it would be on the other side, out of view.
Here we have a couple of shots of the wheel's new leftside chainring, which because I have no machine shop available to me, I had to just build from the raw chainrings JBWelded together in a stack (which was very hard to keep aligned, even with a vise, both before applying the JBWeld and during cure). I also had to JBWeld it to the spokes and hub for the testing stage, as there is no way to mount it on here with any tools or hardware I have available, until I can build a freewheeler that ratchets in reverse so it will work on the left side. Again, need a machine shop.
View from the front (forgot to rotate the image) and outside:
View from the rear and inside (again forgot to rotate the image):
This is the rear assembly from the motor's side; you can see the 7/8" drive socket bolted onto the former pedal crank mount--I simply ran the bolt thru the socket's drive hole and into the pedal crank mount as I would have to put the crank itself on. There's a washer I milled out with the Dremel inside the socket that forces the bolt to fit exactly in the center of the hole, as it was a bit smaller than the actual square drive hole in the socket, of course.
At the top of the image is the kitty litter pail I used for a cargo container, which has proven watertight during two trips in heavy rain this last week. The angled post sticking out the back isn't an exhaust, it's simply the support I'll use to put the cargo container on (vertically) when I move it off my cargo rack at some point, to help lower the bike's center of gravity and make it easier to balance and ride when loaded. It's possible I might end up with a pair of them on either side of that post instead of a single one on top of it, too, depending on how wide the rest of the bike ends up with battery trays and such. I don't want to put too much of a cargo load behind the rear axle, though, because it will take so much weight off the front of the bike I might lose traction turning, and skid out; at the very least it is going to put more strain on the rear tire (which is already hard to take off to repair/replace; another point I need to consider and fix, so it's just as easy as it started out to be).
Just below it is my taillight/brakelight, made from a Microtek scanner attachment light--I simply cut it's cord off and wired it into my controls at the handlebar, via diodes to the headlight switch and a switch on the rear brake handle. It will be on both brakes later, but just this for now, since I always use the rear brake, but cannot always use the front brake due to sometimes having to have my left hand off the bars for turn and stop signals.
Later on, I will have LED turn signals to replace the hand signals, once I have enough super-bright yellow and/or amber LED's for the purpose. I need them visible in daylight, so there need to be more than a few of them at each position. There will be rear- and front-facing ones, as well as some on each corner for visibility to the side and from angles. I already tried just wiring up some auto lamps, and they drained the battery in only a few minutes of use, thus are impractical. LED's are the only low-current high-brightness option I really have.
The same will be true of the brake lights and regular taillights, though I already have enough red LED's to build those.
All of the turn signals will also be steady marker lamps that will activate automatically at a much lower level when it's dark enough, including when I go into shadier areas and tunnels and whatnot, just to make me more visible. The taillight and headlight will generally be on all the time anyway, even in daylight, because they are already bright enough to be visible enough to catch the eye (as daytime running lights or headlights on cars do, which I like when I see them, as they help *me* see oncoming traffic I might not otherwise see as soon due to road conditions).
This is the switchbox I'm using right now to control the lights. It's from an old Hampton Bay electronic ceiling fan control that mounted in the wall in place of the lightswitch. Two of the switches were momentary-on's, and one is a standard on-off switch, with both normally-on and normally-off sides available inside it. I'm currently only using the righthand standard switch to control headlight/taillight, but had planned on using the momentaries for the turn signals, on a 15-second timer (or thereabouts). Now I have an actual 3-position switch in it's own ring-mount off a scooter for the signals, plus a horn button (and a dinky horn), so will probably ditch this whole switchbox later, once I build a mount for the keyed switch for headlights/power/etc from the same scooter. A bit of silicone around all it's edges and the holes in the back, and around the switches and their rockers made it watertight as well, again proven by the recent rain-soaked trips.
Now here is the Plan B (version 1.2.1) bike, based on my Kensington frame. First pic is the handlebars showing my radiator-hose-clamp mount for the "headlight", which is actually just 1 of a $10 set of water-resistant LED flashlights from Walgreens I'd bought a long time ago, and rarely use this one (it's 3 AA batteries, so it's a bit long for a pocket light). The metal casing makes it durable enough, and the switch is a rubber dome, which I left pointing downward to minimize the chances of water pooling on the membrane and leaking around it.
The duct-taped item hanging by wires is the window-motor switch off the Ford. I just did a quick wrap of the tape around it to keep some water out and to hold it all together during the tests; it's left hanging so I can use it with either hand, since I have to hold the switch on against a reasonably strong spring (it's a power window switch; they're made to not come on accidentally) so my hand gets tired in less than a mile. A better switch will be forthcoming once I build the throttle grip, and build a controller instead of just either on or off for the motor.
That throttle grip will be another "key" for the bike as well: Instead of putting the magnet in a rotating cuff, and a Hall-effect sensor in the throttle mounting ring as many systems do, this will have the Hall-effect sensor mounted in the handlebar grip rubber (a silicone-filled patch in a cutout area of the regular grip will keep it watertight), and a magnetic strip along the palm of my glove will activate it. No one will be able to engage the motor at all without it, and unless they're reading this blog, won't know it's designed this way to even try a separate magnet on that sensor area. As I rotate my hand around the grip, it will go faster or slower. Just moving my hand a bit off the grip, or up or down the grip lengthwise, will stop the motor power entirely, so when I reach for the brake lever , it would take my hand far enough off the grip to deactivate the motor, for instance. I've tested the theory with a sensor, a small harddisk magnet in the glove, and a multimeter reading the sensor output, and it should work fine. The harddisk magnet has a very closely-held field, unlike the average magnet whose field can still be fairly strong some distance from it; this is the basis of how I came up with the idea to cut off the throttle just by moving my hand away.
With this, there are no "stuck throttles", which I've had happen several times testing the scooter's throttle grip. No "scratchy pots" either, which can happen with some of the potentiometer-based throttles. No moving parts, just my hand, a magnet in a glove, and a sensor glued in place in the grip. Like magic. :-)
This is an overview shot of the motor, mounting, and drivetrain of the Plan B bike. The motor is mounted on two thin blocks of wood (leftover from when I did a conversion of my waterbed's "box spring" section to a frame to hold it higher off the ground so more drawers could go underneath it), which are mounted to a piece of aluminum cut from a scrapped out patio door frame someone threw out. That frame has been very useful on the bikes, as it has an open section where the glass was held in that fits over all the thin tubing of the rear frames tightly, and can then be clamped to the tubing easily.
In this case, I used two more radiator hose clamps, and tightened them enough to partially crush the aluminum against the bike frame (which is steel), so the motor can't jerk the mounting loose or change it's angle, since I have nothing else stopping it from rotating around the tube besides the friction of the aluminum against the bike frame--it's only a test bed, so permanent mountings would be a waste, especially since I'll have to change the distance and angles sometimes for different motors, mounts, chains, etc.
The blocks of wood make mounting motors with bolt-on points easy, as I can just screw them to it with drywall screws for test runs. The scooter motor was made with such a mounting option, and that's what I used first on this bike, to a reasonable degree of success despite the condition of the motor.
A better-lit shot of the mount, from slightly above.
Here I also had to use JBWeld to hold the scooter's former wheel chainring onto the hub and spokes, though at least on this chainring I had space and mounting holes for bolts to run thru the entire wheel. Those bolts are themselves also JBWelded at each end, to add a bit more strength. Definitely need a machine shop for this kind of thing.
What would have been perfect would have been being able to use the scooter's freewheeler, but again it's made in the wrong direction to use here, and worse was that I couldn't even get it off the scooter's wheel. It's *very* tightly threaded down onto it, and the dissimilar metals may even have oxidized together--I can't see in the threads to tell until I can get the thing off the scooter wheel.
Also, because of the way the freewheeler is made for the scooter wheel, I *might* be able to mount it on the bike's left side without mirroring it first, by putting it on backwards (relative to the side of the bike it's on), keeping the freewheeling direction correct. I don't have that option with the bike-type freewheeler, because it has multiple chainrings on it, not just one, so mounting it backwards like that would mean the larger chainrings would interfere with the bike's frame, not to mention the space needed for the chain itself, and clearance for shifting the chain from ring to ring. The scooter's freewheel mounted this way would just barely allow the very large single chainring, plus the smaller-than-bike-version chain to clear the bike's frame.
Lots of ideas, not enough tools or materials so far. But I've still gotten things to work for testing, at least, even though I wouldn't expect them to last all that long in actual road use. We'll see how long they do last, though, since I really can't proceed any further with new designs without a different motor and a fair number of tools I don't have yet (and won't be able to afford for some time to come--useful machining tools are one thing it's very hard to find scrapped out).
Thursday, December 6, 2007
I still need a better motor, but at least the one I've got is still working so far as an assist when I need it.
I restarted work on the other version, which uses a whole backend of another bike for a left-side drivetrain, with a motor in place of the rear pedal cranks. Looks crazy crappy, but it does work. Unfortunately the 12v power window motor doesn't have enough torque even at 24v to turn the wheel if I have my fingers lightly pressing on the tread. I need it to be powerful enough that the brake applied to medium pressure would not even stop the wheel once it's at full speed, so it will have enough torque to actually move me and the bike along.
I've got several gears it could shift into now, though the actual shifting won't work until I can build a mirror-image derailer for the left side (no one makes one, unsurprisingly). JBWeld strikes again. :)
Oh, and I figured out a way to use the freewheel on the motor side without having to build it in mirror-image, too, though it's not as efficient as if I did the mirror-image version and used it at the rear-wheel hub like it normally is on the right side, to mount the chainrings on. Gonna take some searching for the right bolt at a hardware store, though, because nothing I have here has the right thread pitch and/or is not the right diameter or length. I need a two-inch version of the one-inch bolt that normally holds the pedal cranks on, because it has to go thru a washer, a bearing set and cup, the motor-drive-socket, a metal mounting plate, and the freewheel mechanism, then into the crank socket, so that everything will rotate correctly and freely.
I think it will be a while before I get the full version of the Electricle™ working. :)
Posted by M.E. at 12/06/2007 11:46:00 PM
On a whim, I wrote the company that makes Slime™ products an email about the punctured liner, asking if they made anything tougher than that liner type, and unlike most companies I've dealt with over the years, the representative was very nice, responded quickly, actually read what I wrote and responded appropriately, even when I asked questions about who makes their tires, which I did not expect an answer to! (Cheng-Shin, which also made the tires that used to be on my spare bike, now on my main bike to test tread and shape differences from my Kenda's).
She said that they don't make any separate product tougher than the original liners, but that mine were probably an old batch from before some improvements they've made. So she sent a pair of those new liners at no charge, and also threw in a thorn-resistant pre-Slimed tube. Due to an error in their shipping department, they actually sent me a pair of non-thorn-resistant pre-Slimed tubes instead of the liners at first, but she quickly rectified that and got me the liners (which are now in my main bike's tires).
I was going to just put the thorn-resistant pre-Slimed tube in the tool pack as a spare, but as I was re-airing up the tires after installing the liners, the stem valve on the last of my spare tubes I'd put in that rear wheel ejected itself from the tube as it got around 40PSI! So I swapped it out for the Slimed tube, and instead will carry one of the non-thorn-resistant pre-Slimed tubes as a spare (it's much smaller and lighter, easier to fit in the pack, anyway). No problems there, at 60PSI.
I really don't know what is up with the tubes blowing out their valve stems, but it must have been the entire batch of them--I think I had three of them, and they all did roughly the same thing, only varying in how much of the rubber of the stem came with the valve--the last one was rubber-free, totally separated from the stem. I'm hoping I will be able to repair them and use them reliably, but I doubt it--I will have to find a bonding agent to adhere the rubber to the brass stem. JBWeld unfortunately won't do that--it'll stick great to the brass, but not the rubber, and the same is true of most other adhesives I have around here, including one- and two- part silicones of various types. I'll worry about it later, since for the moment, I have two spare tubes, courtesy of Slime™.
Posted by M.E. at 12/06/2007 08:36:00 PM
Saturday, December 1, 2007
More good news: It still works, more or less.
I couldn't get the mounting ring off the scooter wheel, so I just went ahead with the JBWeld plan, and added some long bolts thru the spokes to help clamp it in place as well--they won't stop any real torque breakages but they'll minimize any flexing from spoke bending as the wheel turns (which might be what broke it off the first time).
I didn't realize it was 3am when I finished up, though, so I ended up sleeping till midday. Still raining all night and morning, so no big deal, there--didnt' want to test in the rain if possible not to. :)
The big moment: Pedaled up to speed, engaged motor, stopped pedaling--no crunchy sounds. It's about as fast as my comfortable pedalling speed, so it's certainly good enough--I don't need fast, just easier. Went around the block a few times, probably a mile's worth. Checked motor, it's getting pretty warm, but that was expected--it's moving about 10 pounds more than the original scooter it came off of, and it's turning a much bigger wheel (which probably masses twice what the original wheel did, perhaps nearly thrice).
Kept going, then about halfway thru the very next loop around the block (1/8th mile, perhaps), there was a zap sound, and suddenly I was slowing to only half speed or less. I stopped the motor immediately, it was *very* hot, several times as hot as it had been just before, when I had checked. Definitely something wrong.
Pedaled back home, opened up the motor casing, and immediately wished I'd done that outside--it stank of burned insulation and melted metal. At least one winding (of 16) is burned thru completely in one spot, and it is very apparent that more enamel has darkened, some of it has actually charred off the surface of the windings. Other than rewinding the motor myself, there's nothing I can do to fix it. If I can get the wiring off of one or more of my old cieling fan motors intact, I might try it, but not yet.
The motor still works, just not as fast as it would if all windings worked, and eventually more will probably go if I let it get hot again. There are identical replacements for only $40 off electricscooterparts.com, but as I said before, I don't want to buy one. I'm checking Craigslist and Freecycle to see if anyone has another old scooter like the one I salvaged already, so I can take the motor off of it (thus not having to change my mounting already built--though that's just a couple blocks of wood screwed into a section of aluminum patio door frame held to the bike by two radiator hose clamps :-) ).