I've been reading around, and found someone in the EVDL mailing list is thinking a bit like me. They posted a link recently, about a turn-of-the-previous-century SOC meter called a Sangamo.
Basically, what it does is use a shunt with a movable center tap, and the charge going in spins up an electromechanical counter to read out battery capacity in Ah, and the charge going out spins the same counter back down to null that out as it is used up in the motor. The center tap is adjusted to compensate for the fact that you'll put more into the batteries than you actually get out.
I have a few electromechanical counters around here that I could set up to count this; I think one I got many years ago at Apache Reclamation runs on 28VDC for aircraft stuff, and is a 3-digit power-on counter. That might mean that it can't be run in reverse to count back down, but if it can it'd be perfect for this.
I'm tempted to try working out how to build one just because it is old technology that is "good enough", and is certainly durable enough for the heat and vibration the bike endures. An electronic one isn't necessarily. Plus, this one would cost me nothing but time and brain power, neither of which I have in abundance but do have more of than money. ;)
Monday, September 28, 2009
I've been reading around, and found someone in the EVDL mailing list is thinking a bit like me. They posted a link recently, about a turn-of-the-previous-century SOC meter called a Sangamo.
Sunday, September 27, 2009
While discussing the pedal chain problem with someone else, it suddenly occured to me that it could actually be the frame twisting, which was not really possible before due to the multiple triangles of the center frame, which no longer exist. A tensioner should still fix that, but there can't be *much* twisting happening, as I can't feel or see it, so that tells me the chain is on the edge of coming off all the time even *without* this problem. :-(
Speaking of chains, I just tied the chain up out of the way for all of my riding to and from work today, and it worked ok. However, I don't get nearly the speeds I think I should be getting; I think the 12A shunt analog ammeter might be restricting the current flow, or I might have a poor connection somewhere (probably with the wires from the battery pack to the meter, quite possibly in the crimp connections to the spades for plugging into the back of the meter).
That's easy to check, by bypassing the meter at the pack, just bolting the two wires back together again.
Now, I know it'll be slower with the 24" vs 26" for the same gear, but this is more drastic than that. Maybe 3-4MPH less than before. According to this calculator:
it shouldn't be more than at most 1.5MPH difference, not even that, for top speed in highest gears.
Also, I think the rear brakes might be flopping back and forth touching the wheel, slowing it down in bursts, because when cruising I can watch the ammeter fluctuate by a couple of amps or more, with a period of less than a second, which I think is about what a wheel rev ought to be, especially since as I slow down I can watch the oscillation slow as well. It doesn't always happen, but there's enough noise on the road including the motor noise that I can't really hear sounds well enough from the back of the bike to hear if something is rubbing.
So between those possible problems, both of which are still awaiting confirmation, I guess it could be robbing me of enough power to cause this.
A completely random thought regarding the name and looks of the bike:
I am seriously considering a mutation of the CrazyBike into the Junkyard Wolf, with "fairing" that would look like a wolf leaping/running, with it's legs over the front wheel in a kind of pounce position, rear legs astride the rear wheel as if having just leapt into the air. Head would be right where the lighting is now. Then my seat would end up just over the curved back.
I think a prototype version of this look is in order first, and then when I rebuild the bike "from scratch" to improve all the many things that need it from this prototype, I can make a better more permanent version of the "wolf fairing".
Friday, September 25, 2009
Today was not a good day at all, so I did not get any of the testing with the old tires redone. By the time I was done being frustrated by life, all I felt like doing was installing the new tires to see how they work, so that's just about all I did.
I didn't fix the rightside rear axle-nut clearance problem, so I still have to take the rail loose to put it on or take it off. I think I'm going to go with the hole thru the cargo pod and rail to get to it--it's the easiest to do. Whenever I have a day where things are going better for me and I am not afraid I'll totally screw it up. :-(
Here are the new tires, on the bike:
If I had any spray paint, I'd give them white sidewalls. Since I don't, I'm trying to remember where I put the latex wall paint that's off-white, and I'll use that, even if it peels off later--the visibility factor of light colored sidewalls is large enough I want it back.
Here's a shot of them with some dirt on the treads, so you can see the contact area they have rolling over dirty pavement. Nice and wide area, compared to the MTB types.
Closer shot below:
Also shows the brakes, which need readjusting again.
Speaking of brakes, here's a shot of the rear wheel with new tire, plus the brake arm extensions I had to make:
The arms fit the 26" wheel fine, but they are about 1/8" or more from being long enough to hold the pads on the 24" rim without rubbing the sidewall even if I have them properly installed, before engaging the brake!
So I cut the slotted tabs off a set of bent up calipers off some junked bike and bolted these tabs to the existing arm tabs at an angle, giving me just the right positioning of the pads.
The pads are at the funky angle when not engaged because the downward force on the calipers is so strong that at speed if I brake hard the calipers are pulled downward at their wheel ends so far the pads would tear into the tire if I didn't do this. As they are, they end up gripping the rim perfectly once engaged, and angle normally to the rim.
I had tried some retaining tabs bolted to these tabs, with a hook that went up and over the frame stays above, but when I braked hard they just bent, slipped over the frame, and jammed the brakes against the rim so I had to actually unbolt the pads to get the jam cleared. So I'll live with the flexing until the calipers break off at the swivel/mounting bolt or something.
I like the feel of these tires a lot better than the old ones. It sort of feels like they might be doing better shock absorption, but I think it's probably just because I don't have any of the knobbly vibration I did before. It's especially noticeable in turns, because of the front wheel now being a smooth curved surface instead of rows of rubber rocks, basically.
Since I couldn't do any scientific testing today, I took some photos of the side-view of the contact patches for the various tires I had on the bike. They're not all on the same rims, since I didn't want to unmount the bike's wheels with the new tires just for this.
Front new tire:
Rear new tire:
Old front tire from powerchair:
Old MTB/road hybrid tire:
Original "roadmaster" wheel tires I started with:
26" Cheng Shin I use on my upright bike, which was in use on Crazybike2 for the rear most of this month until today.
That's it for today, except to report that I kept having the pedal chain come off and get jammed up in the rear sprocket during all riding today, about every few hundred feet, to the point where I finally got frustrated and just tied it up out of the way and used the motor for everything instead.
The problem is getting worse, but I cannot see *where* the slackness is coming from:
- There's no additional wear measurable on the chain at any point; I cannot see a difference between it now and when I marked it on the tape for making it up when i redid the frame.
- The chainrings don't seem any different, but I can't really measure those. Photos appear the same when I compare them.
- The frame itself does not appear to be bending or shifting, but I didn't do any accurate measurements right after the modifications to compare to now; it's just a by-eye thing.
The motor chain is not having a problem at all, just the pedal chain. And I can't see the mechanism by which it is being popped off, either, as it happens at random times, with no one thing causing it.
- I can hit a pothole or a bunch of bumpy road and nothing happens, but later if I am just cruising BAM it pops off, even with no change in speed, torque, etc.
- I can shift gears one time and it'll pop off, but the next shift doing the same thing doesn't do it.
- Pedalling harder than the motor is spinning (which puts tension on top of the chain and loosens the bottom) doesn't make it happen any more often than running the motor without pedalling at all (which forces tension on the chain along the bottom and loosens it on top).
So I'm stumped; I only know that it always happens at the rear end of the pedal chain, not the front. I'll have to put a chain tensioner back on to stop it from happening, because this sucks.
The technical problems mentioned in the previous post about coastdown testing was that somehow the righthand nut on the rear axle had been very very slightly loose, but I was unable to tell that due to the placement of the bottom cargo rail plus the derailer. I thought I had it as tight as possible, but actually the wrench was hitting the derailer's swivel point and resisting, so I thought the nut was tight when it really had at least a half turn or more. With the cargo rail on there, the wrench would push against the rail and the derailer's swivel point, start to turn then slowly get resistance as the derailer spring compressed, then feel snug. With the cargo pod in the way, I can't really see that happening, so I thought I had it. :(
The effect was that the left front sidewall would rub on the frame, and because there is extra room behind the leftside axle in the dropout (since no derailer is behind it to stop it sliding up) I *thought* that the left side was loosening because of all the weight on it and slowly sliding up the open dropout, since it seemed to be happening after I hit bumps and whatnot.
After each test I went home to change the wheel/tire, and I had the problem with both the 24's, after swapping out the 26". The 26" had not had a problem, because I had put it on *before* I put the cargo rail on, last time I was working on stuff, and without the rail there the wrench can be placed on the nut differently and there is no problem with this kind of thing. But I did not realize that was what was causing it until too late....
I only had to "fix" it once on the 24" MTB/road hybrid test. I had to do it a couple of times on the 24" gray test, and it got worse faster (because I had probably been in a hurry changing it out). Then when I was done with the tests because it was getting dark, I went up to the store to get 40lbs of dog food, loaded 20lbs into containers in each cargo pod, and went home (about 6 miles total), planning to go somewhere else when I got the dog food unloaded at home.
So as I rode I kept fixing it, and the fixes became more frequent as I rode on, even though I deliberately shifted into lower gears and rode slower. That was my mistake.
Shifting into lower gears put more torque and pull on the chain on the right side, which was the loose side, so it kept pulling farther and farther forward. Each time I "fixed" the left side, I was moving it forward in the dropout just a hair, closer and closer to not being *in* the dropout anymore. But it was already dark, and I did not really notice that. Each stop I had to carefully tilt the bike onto it's side and try not to spill any dog food (the containers are closed and latching, but not spillproof if you suddenly tip them over; they're cheap), and I was paying a lot more attention to not losing my cargo than fixing the bike.
Bad idea. Plus I was getting frustrated that it was even happening, because I couldn't figure out how it could possibly work it's way loose like that.
I was about half a mile from home when I stopped the last time to fix it, and loosened the left nut to "fix" it again, and the wheel came out of the dropouts on *both* sides!
Suddenly I realized what the problem was, why it was happening, and that there was no way I could fix it till I got home and got my cargo out, because I'd have to take the rightside cargo pod off to take the rail off to reach the right nut properly. Wow.
I got it back together well enough to walk it home, but even just activating the motor on the teensiest amount of throttle to let it help me push the bike along (it's really heavy, about 180-190 pounds including that dog food and the containers and stuff I had with me right then!). If I did that, it immediately pulled the right side loose again, though at this point knowing what was wrong I was able to use a screwdriver and wrench as spike and hammer to push against the axle nut to get the wheel back in place. Then I walked it home that half mile or so. Yuck.
So major design flaw is revealed. As someone that came by as I was fixing it the last time pointed out, it's like the car you have to take the passenger wheel off to take out the battery (don't know if there is actually a car like that, but that was his phrase). Seriously hampers fixing stuff on the road, since while it can be done, it is a major operation and will take a lot more time than it should, just to tighten that nut.
Oddly, I did not have this problem before changing the central frame, so something in the angles of frames must have changed slightly despite me trying to keep that from happening, leaving me less space for the wrench, plus the newer derailer is a different shape and closer to the wheel nut than the old one was.
Two possible fixes:
--One is to carve out a bit of the bottom edge of the rail, so that a socket wrench can fit thru it to tighten the nut. However, that would still require loosening the bottom bolts of the cargo pod to get the socket onto the nut, unless I also drill a hole in the cargo pod that lines up with that nut and is large enough for the socket and extender. Plus I have to then carry a socket wrench, extender, and socket for those nuts, none of which I have to have right now. That is another couple of pounds or more to the bike weight.
--Two is to remount the rail itself higher, to give full clearance for the regular open-ended box wrench i already carry for this. But it would have to go at least two inches or so higher, to be able to reach it. I'm not sure how well it would really support the bottom of the pod at that point, since it would be near the middle of it.
For now, I don't actually have to do anything, because as long as I tighten it without the rail on there when installing the wheel, it should be fine. But should I ever have to fix the tire on the road, it'd end up being a major operation to do, and I really really don't like that idea. If I am riding in the daytime, it'll be hot and melty while I do it, and if I am riding at night (much more common) I risk getting stuck on some poorly lit area with who knows what kind of people waiting for just such a sucker as me to be stuck there as their prey. If the wheel is messed up as it was tonight, I can't even walk it home, since the sidewall rubs so hard against the frame that I can't push the bike against it!
So...somethings gotta change; I just haven't decided what yet. Probably it'll be option one, because it's simplest to do with the least consequences structurally.
I also need to change out the tires to the new slicks, and finish the testing.
I had been planning on doing various types of tests for later comparison as I change things on the bike, but somehow I never ended up getting around to it. One of those tests was a coastdown test, to determine comparison data for later rolling resistance and aerodynamics tests.
Today I tried to do them, but it turned out to be almost a waste of time, because due to technical difficulties on the way home after the last test, I lost the paper I'd written the results down on when I stopped to fix the problems at some point. However, I'll post what results I do have, for later perusal, for what use they may be.
For the current tests, I used this donated analog ammeter, apparently from an old charger:
It's wired on the battery side this time, rather than the motor side, since the current draws should be lower based on the PWM multiplication effect, and maybe would all stay within the range of the meter (12A).
I tried the red HF DMM that I'd fixed, but there's something seriously wrong inside, as it got hot and began smoking at the shunt (visible easily thru the hole I'd cut to both keep the shunt ventilated and to resolder it thru if it failed again later) even with only 3A current thru it, so I decided to not use it for these tests. If I spent the time to fix it now, I wouldn't get the tests done.
Unfortunately, ultimately all the startup currents were still out of range of the ammeter, though operational cruising currents were roughly the same as they had been with previous tests of motor side currents using the HF DMM, several posts back.
Now, for the coastdown tests, I accelerated to 20MPH on a relatively flat stretch of smooth paved road, then as I passed a marker on the side of the road I cut all power, started the stopwatch function on a wristwatch, and coasted down to 10MPH (the point at which I begin having a little trouble keeping it stable--at 9MPH it's difficult and below that it's really problematic) and stopped the timer. I repeated this in the opposite direction, and did each run twice, to help eliminate wind, even though it was essentially still air at the time, noting each time down on paper, because I have a mind like a steel trap (everything comes out crushed and mangled).
The first test was the 26" already on there, so when I rode home after that test, I changed the whole wheel out for the previous 24", using the MTB/road hybrid tire. It also has the identical rear cassette as the 26", for some current tests under different tire diameters. After that I rode home and changed out just the tire to the gray powerchair tire identical to the front one. Then it was too dark to continue, plus on the last trip home after that test, I had my technical difficulties mentioned above.
I cannot remember any of the actual times, but there was basically no difference between these three rear tires:
(Gray 24" powerchair knobby on front in all cases)
26" rear road
24" MTB/road hybrid
24" gray p/c knobby
Maybe I'll redo the tests with the last tire on it before I do the tests with the new slicks.
There was also no significant difference between the battery side current draw for any of the 24" rears. The 26" rear, however, at the same gears as the 24" (using the identical rear cluster), was I think about 2 amps more than the 24" for accelerations; cruising at speed generally seemed around the same but fluctuated a lot more on 26" than 24".
With the 26", I also did a braking test from 20MPH, squeezing both front and rear brakes really hard to skid it and see how far I would skid, but the number was lost with the paper.
I couldn't do the test with the 24s since I did not have a rear brake with them. That I still have to add a crossbar to mount them on, and would test them then.
I did do a test with the 24" front gray knobbly only, while I had the 26" rear on there, but again, it was lost with the paper. :( I had planned to compare that to the 24" slick once I changed them out.
The problems I had later will be in the next post, to keep this one short and to the point.
First, pardon the rush of posts; I've been typing these up over several days, but due to life didn't get any of them finished till today, so there's several in a row for today.
Well, they're unused, so you could call them new, but they're recycled in that they come from a place selling stuff "salvaged" from old inventory from somewhere else--stuff that would probably have ended up in a landfill eventually if no one had bought the stock.
They're cheap enough that they don't even have a brand name on them, just "made in china", which if I had a choice I would avoid. But my budget being what it is (negative, actually having to skimp a lot on groceries to get these), I can't really not take a deal that gets me smoother road tires for a price I *can* skimp and live with, since they should help significantly (I hope) with a few issues I have with the current 24" MTB knobby and hybrid tires I've got.
So here's what they look like:
Then these are the others I've got for the rear
Now, the problem with this particular tire is that while it is slick enough in the very center, that's not a very wide strip,
*plus* it is rotting from wherever it sat before I got it, causing cracks like this one in the sidewall:
and there is a chunk that's actually missing out of it too:
Then the front gray powerchair tire:
which again has a narrow continuous strip in the very center, but is still knobby everywhere else, and you can feel it as you ride even at 50PSI (where I keep all the tires).
Thus with both of the existing tires, there's not as much contact patch for traction or for braking. The new tires fix that. I just have to install them (after some testing) and see how they perform.
EDIT: I forgot to put a pic of the 26" road tire and tread in, so here it is:
That center is not exactly like it looks; the very center line is a valley between the two halves, and the tread to either side curves *down* into it, to give a long trough for water/etc to be pushed into, leaving the tread on either side essentially in constant contact with the road, since it alternates back and forth overlappingly.
Thursday, September 24, 2009
A cyclist friend interested in the project came by a few days back, and we did some riding down the street near my house around dusk, just to test some things, see how it looked, etc. Nothing new on the bike at that point really, except the frame configuration, battery location, and circuit breaker, I think.
You can see how the bike lighting looks, in darkening light conditions, compared to other lighting sources though. Celphone camera, so don't expect IMAX quality here. :-)
Tuesday, September 22, 2009
I thought of something a while back, but have not yet tested the idea beyond a simple quick check:
If I have a 4-pole PMDC motor, is it possible to run it using only two of the poles?
A few minutes ago, I decided to formally ask the question over at DIYElectricCar forums, where I've gotten useful answers before about motor stuff like this. I'll post the gist of the answers I get once a conclusion is reached.
Basically, this 4-pole motor is wired so that two brushes, 180° apart, are both connected to one of the input leads. To use just one pair, two consecutive brushes would be disconnected or removed.
So, if I apply power only to one set of brushes, should the motor operate "normally", except for consuming only part of the current, and producing only part of the speed and torque? Potentially with cogging issues at lower speeds since it is a PM motor?
I have tested with only one set of brushes installed and it does function, reducing (at 12V) the no-load current from about 4A to about 3.5A (using my gloved hand to grip the shaft as hard as I can, which slows it down a little, gives a load of about 6A with 4 brushes, and about 5A with 2 brushes).
The speed (loaded or unloaded) is significantly less with only one set of brushes, though I don't know by how much--I'd presume 1/2 speed; it sounds like it. I don't have a tachometer at the moment to test that.
I am thinking of doing this because most of the time I will not need all of the torque or speed that this motor can produce, and so do not want to "waste" the power the second set of windings would consume unless I am actively using them.
So if I setup a pair of relays (contactors) at the motor housing near the input contacts, and wire the brushes independently, so that I can cut off the power to one of the two brush pairs after I have gotten moving from a stop or finished going up a hill (the only times I should need the extra torque), is it likely to have any serious side effects?
I doubt it, but I'll wait for the experts to reply there before I perform vehicle-power-level experiments with it. :)
EDIT: I was typing up something to someone else, and thought of a more concise way to say some of the above test results:
All readings are approximate, and done on a harbor-freight DMM. ;) Single MKP 12V U1 used for power, no controller, just direct wiring.
load of gloved hand 5A
current ratio around 1.2
load of gloved hand 4A
RPM sounds about 1/2 of 4-poles.
current ratio around 1.14
Margin of error on the current ratios is too high to presume that the higher ratio on the 4-pole tests would be valid under higher voltages and higher loads without testing using a known load, such as a brake handle squeezed to a specific angle. But if it does continue upward like that, it would probably make a significant difference in current with only 2 poles vs 4 at the normal vehicle loads.
However, since the no-load draw at 12V with 2-poles is already almost as much as that of the 2-pole motor at 24V, I wonder if it will make much real difference.
Hmmpf. Any power savings is still a power savings, I guess. :)
Monday, September 21, 2009
I'm still trying to think of good weight reductions I can safely do, but there's not a lot yet.
- The frame mods already done took off perhaps 3-5 pounds.
- I might get a half a pound off by going to the single-cable multi-conductor thin-gauge wire for all the bike lighting and sensors and stuff, removing that scooter harness.
- I'll probably gain an ounce or two going to the all-LED lighting for the turn signals/marker lights, but I'll lose at least a pound by removing the other lighting system that was on the DayGlo Avenger (which I'd like to put back on it).
- The cargo pods and their attachment frame are maybe 15-20 pounds, empty. Part of that frame (the front half of the square tubing) is also the seat mount, though, so doesn't count.
- The batteries alone are I think 51 pounds. I'd have to go to something like A123 cells to get enough power in a lighter package that wouldn't be damaged by what I use it for.
- The difference between the 4 pole motor about to go on and the heat-damaged 2 pole motor about to come off is more weight added than I took off with those frame modifications.
- The front fork can lose around 5 pounds, maybe less, if I go to the non-shock fork. I'll gain at least two of that back if I add the headtube shock later.
- The steel front cranks are maybe 2 or 3 pounds heavier than aluminum ones would be (if I had any to spare for it).
- Can't get the seat any lighter.
- Handlebars are as light as they'll get for the shape I need, unless I could get some modern ones custom-made out of thinner but stronger tubing (or get lucky and find some scrapped like I did these).
- Those little white baskets that held the batteries before could take off a pound or so, but they will actually hold my backpack or something else, bungeed between them and the bottom of the seat, should I take the cargo pods off for any reason.
- There's nothing else I think I can safely remove from the bike frames themselves.
- The 26" wheel with wide steel rim is probably a couple of pounds more than a 24"; since I only really went to 26 because I had a lower-rolling resistance tire for 26 but not 24, I can go back to 24 once the tires arrive from All Electronics.
- The toolkit could probably be slimmed down a couple of pounds if I could standardize all the fasteners on the bike, so that any emergency roadside work doesn't require the large assortment of tools and driver bits that I carry right now.
A friend found All Electronics in California had some salvage NOS 24" road slick tires (ex-Currie Izip chopper front tires) for only $5...but couldn't take them on the plane. However, I checked with AE and they will ship them for a reasonable cost, so I skimped on a bunch of things on my last grocery run and ordered four, since it's unlikely I'll run across this kind of deal anytime soon, and I do need better rolling resistance tires, with a smoother tread. Of course, now I'll have a dozen comments from blog readers telling me about much better deals. ;-)
I figured four since then I have one pair plus two spares, or if I later use all three on a trike I have one spare. I can't afford any more than that.
Hopefully they'll ship them Monday, and be here within the week, if I'm lucky. Then I can test speed vs current compared to the tires I already have, as well as a coastdown test to see what difference they make in just plain rolling resistance.
I'll test first the already-mounted rear 26" with road-type tire, and front 24" MTB-style wheelchair tire. Next, the same front tire with the old 24" Schwinn-marked tire that is a cross between MTB and road; still knobbly but not nearly so much as the front one is. Then I'll pull both tires off and replace with the new smoother ones.
The coastdown test will be done hopefully somewhere with no traffic at the time, so I can concentrate on a stopwatch and the spedometer and the start point on the road, without worrying much about anyone suddenly being in my path or they in mine. Basically I'd just mark a point on the road at which to turn off the motor and coast down to a stop (or actually, down to a known speed, around 9mph in my case being the slowest it's really stable at), from a specific known speed (20mph, giving me the longest coast test, if I can).
I can't do the traditional coast to a stop because the bike is not self-stable at lower speeds than that, and I'd have to keep either wobbling and weaving to stay up, and then at some point start touching the ground with my feet to balance, which will all be significantly different each time I do it, and affect the run's results too much. So I just have to make a cutoff point in speed, and stop the timer there.
Repeat the test a few times with each tire set, and average the times, to help account for changing wind conditions.
This will also tell me something about the bike's aerodynamics (which are pretty awful, I'm sure), for later comparisons as I add fairing bits.
I passed 500 miles sometime in the last week or so I think, and am now nearly at 550. That's the total miles on the whole bike/frame/etc, even though some parts have changed at various points in there. Here's to hoping it lasts at least that amount again, since it is taking far longer to get to the trike than I had expected.
Since I now have bolts that will secure the 4-pole motor in place, and the heat-damaged 2-pole motor gives me a good reason to swap it out, I'm going to try to do it this week, since I only work two days :( and packing/sorting is driving me crazy and depressing me too much to keep at it for more than short bursts before I have to do something else for a bit, then go back to it.
First I have to make a wedge-shaped box or plate to go between the new gearbox and the motor mounting plate on the frame, because the 4-pole motor has an angled top, plus a longer motor cylinder, which combine to mean that even with the cylinder touching the BB between the pedals, and the gearbox as far forward as possible without it's output shaft conflicting with the cranks' rotation, there's still a wedge-shaped gap between the gearbox's top and that mounting plate.
I'll be working on two ideas for making the wedge. One will just be wood to test the angle and see if that is sufficient, and if it holds up to tests without crushing/splintering or working loose from vibration/compression, I will just leave it. The other, if the wood isn't sufficient but does work, will be some steel plate welded into a wedge-shaped box, with reinforcement ridges inside next to the bolts, diagonally (making the interior an octagon).
The chainline shouldn't change more than a couple of millimeters laterally if I measured it correctly, so it should stay tracking fine once I put it under tension and tighten down the motor mounts.
Since it is a faster output gearbox, it'll use a smaller output sprocket on it's shaft, a 21T. This should keep the max output speed still down around something sane for pedalling along with it (since they're still linked, as I have not yet completed that sprocket adapter disc to then hook to the pedal freewheel and try it out).
I should get around the same final speed, but it should be able to handle a LOT more mass and accelerate a lot quicker (at the cost of using more power all the time, because it is 4-pole instead of 2-pole). Theoretically, it makes hill-climbing at speed much easier, but mostly it will make hauling cargo easier (especially if I carry extra batteries on the trailer).
Saturday, September 19, 2009
I was going to swap out the heavy shock fork for a lighter aero-tube 10-speed fork from a 70s or 80s bike, and it looked like a good plan.
I knew I'd have a problem with the brake distance, since those v-brakes you see on the gold fork are set up for a 700c size wheel (I think), and I'll be using a 24" wheel, but I had a couple plans for that...however Murphy was watching again:
--first, the wheel I needed to use has a wider spacing than the fork was made for, by maybe 5mm or more. Ok, I can spread the dropouts.
--Then, the axle is larger diameter than the dropouts, by at least 2mm. Ok, I can file the dropouts a little bit, or use the axle from an older wheel that's made for these forks.
--I don't have any axles that small that will *also* work with the bearings and races for this wheel.
--Filing the dropouts will weaken them a little. This is a really heavy bike, and for a while will have no suspension, until I find all the stuff I need for the headtube shock.
--If I use the smaller axles out of the 10-speed wheel, they'll be too short to fully secure with the nuts on the wider wheel with the dropouts spread enough to fit. That could be dangerous.
--If I live with the nuts being not fully threaded on, the races still aren't large enough to press the bearings fully against the hub's races, even if I use larger bearings. That means the wheel will rattle around on the axle. Very bad idea.
--Since it's a 24" wheel on a 26" (actually 700c, I think) fork, it'll need something to extend the old v-brake arms far enough to actually work on the rims. Cutting the slotted section off some other brake arms and bolting them on wouldn't be long enough by far, it'd need at least two of those, maybe three. So I'd have to take some aluminum bar I have and drill it and bolt it on, to get the length.
--Even if I use that, none of the regular brake handles I have use the right mechanical advantage to pull the vbrake hard enough to even touch the rims, so I'd have to use the old style brake handle, which requires reworking some stuff on the bars to make room.
I think I had some other issues but I can't remember them right now, with all the other stuff above.
Wednesday, September 16, 2009
The experiment today was a partial success; I forgot to really crank down the mounts on the 2-pole and it got pulled back by the chain little by little as I rode, and about halfway thru my pre-work riding the chain slipped off because it was too loose, and got wrapped up in the chainrings and locked up the motor/drivetrain.
Unfortunately, Murphy was watching, and so an unrelated wiring issue (loose splice and tape on the throttle cable from an emergency repair I had forgotten to fix more permanently) happened to fail at the same time, in such a way that the throttle acted stuck full "on". :( Since I couldn't hear the motor turning (because it was jammed) and I'd turned the throttle lever all the way down, I didn't notice the problem until I smelled something and then saw smoke coming out of the motor housing, while I was stopped trying to unravel the chain mess.
I flipped the breaker and checked temperatures by hand, and I could not even touch the motor's cylindrical housing without burning myself, and after a couple of minutes the gearbox and output shaft and sprocket heated up to be really really uncomfortable to touch (was still trying to get the chain untangled), even though I was melting ice cubes out of my water cup on the motor housing to cool it as fast as I could, and had taken the plastic nose cap off to let air in there. The controller's heatsink was pretty hot, but I could comfortably leave even the back of my hand against it. Dunno what the inside temperature on it was like, though.
Before continuing, I let it cool till I could leave my hand on it (barely), left the cover off, and rode to work still using the motor, but at reduced speed with lots of pedalling, so I wouldn't overheat it any worse. It does still work, but it is definitely damaged--I can see the winding color is changed even without taking the armature out, the smell is pretty yucky, and there is a lot of commutator/brush noise, so I think one or more segments may have lifted a little from the heat. :(
It worked on the way home, too, still noisy, but the chain kept coming off over and over which was very annoying. I couldn't tighten it without taking the batteries out first, because the two-stack is right on top of the front motor bolts. :( SOMEbody did a crappy job of engineering this part of the bike for on-road adjustments. ::rolls eyes::
On the other hand, the radiator-hose-clamp battery straps held them in place fine, even with the potholes I ran into. I had expected them to shift around, especially the rear one.
No other problems besides the motor/chain issue, so I am going to try mounting the 4-pole motor, now that I have some bolts to fit it, and see if it runs the bike well enough without anything breaking. :)
The newly-added rear brakes worked fine, though there is almost no brake action until it is squeezed really hard. Also, I forgot to point this out in the previous post, but I decided to use the Honda scooter's brake lever that has a parking-brake latch, which physically holds the brake in squeezed position when set. I'm pretty sure that the scooter's brakes used a different amount of mechanical advantage and that's why the sensitivity is very different from the usual bike brakes, with me using the scooter brake lever to control regular bike caliper brakes.
Nice thing about the parkng brake is that unless someone messes with that, it's also not going anywhere even if somehow the motor gets turned on, since the parking brake is on the driven wheel.
Balance of the bike is definitely different, with that third battery up higher than the other two, and all of them a little higher than they were in the side trays, but centered on the bike both longitudinally and laterally.
Tuesday, September 15, 2009
Looks positively skeletal already. :)
Lost about 5 pounds today, taking out some of the middle frame struts, and condensing some of the wiring down (more of that to come later as I swap out all the wiring harness mess for a single multiconductor cable to each end of the bike).
The part I don't like is that this will weaken the frame torsionally, as it had lots of cross-connection before that isn't there now, but it should still function well enough. If not, I guess I'll see what I can do to fix it!
Above is down thru the center of the frame, where the downtube used to connect to the rear BB. That's the gearbox on the left side of the pic.
Also got a LOT more room in the central frame area. Not yet road tested like this; might need changes.
Clearer shot of the new V connecting the front to the back at the bottom. The cargo rails are also bolted to the dropouts on both frames, adding a bit more stiffness.
Managed to get rear brakes installed, though, while I had it apart. Nice to have them in addition to front brakes!
Betters side shot. Regular caliper brakes using modern brake pads.
Full side shot of the whole thing.
That black mass in the middle is the three 12V 17Ah UPS batteries. They are held very securely in with radiator hose clamps, which have successfully held my seat to the bike frame this whole year so far as well, with no wiggling or looseness.
Ideally, I'd like more of them, for cross-clamping, but that's all I have except for a handful of tiny ones that are different widths, and thus can't be chained together.
Closer shot of the power area. That white box is a hefty breaker to use as a mains switch.
I dont' recall the rating but it is enough that a battery pack short pops it, but even full stall current on the motor at full charge voltage does not.
The way they sit in there, there is enough clearance to the chains and sprockets that I could probably take some 1/8" aluminum and build a "box" around them, clamped to the frame. But that will add more weight, too. :(
A shot down from the top showing the not-so-neat rightside, before tying it all down.
Closer shot of the breaker. It's arranged so that to trip it manually I only have to reach down and flick it up. To engage it takes a bit of downward force while holding the breaker a bit, so it can't come on accidentally.
I also have the battery cutoff keyswitch I still have to install, but it needs a mounting plate to bolt to.
Still in progress, gotta swap out the really heavy shock fork for an old 10-speed aero fork. Which interestingly enough is still the same distance from the bottom of the headtube/crown to the dropouts as the 24" shock fork, even though it is from a 700C bike). Guess there is a lot of movement room in that shock fork. But first, I have to weld a tab across the fork to mount the brakes on, and temporarily use just some caliper brakes, until I decide if I'm going to keep using this fork, at which point I'll put some studs for linear pull brakes on there. It should save several pounds minimum without that shock fork.
Because of a change made to the angle of the bottom frame, to make the line between the two BBs as straight as I could, the motor's angle changed.
It just clears the pedal chain, which hangs about 1/2" below the output shaft when it's not under tension.
Now to take it out and test ride it on my way to work. ;-)
Sunday, September 13, 2009
Since so far all I have had is estimates of total weight based on various component weights, some of which themselves were estimates, I finally got tired of the guessing game on weight, and set the bathroom scale so I could put the bike on it upright resting on the rear ends of the cargo rails. I could barely hold it in place and still read the scale, which kept wiggling between 140 and 150 pounds, including my toolkit, air pump, and a handful of bungee cords (probably 10 pounds at most).
So the bike weighs a LOT more than I had thought, since I was estimating roughly 120 pounds.
I'm guessing that the square-tubing I used for the seat mount and cargo top rails is much heavier than I thought (I never weighed it). Among other parts, I am going to see if I have bike tubing or something else of the right type to replace it and make it lighter.
That will save from 5-30 pounds, depending on exactly how much that square tubing weighs.
I am also going to cut the downtube of the rear frame off, along with the seat stays of the front frame and those ex-front-fork braces that go from the top of the seatpost on the rear frame to the dropouts of the front frame. That will be replaced with a reversed pair of chainstays welded to the rear BB so that their dropouts line up with the front frame's dropouts, and then I'll bolt those together.
That will save some undetermined amount of weight (maybe 5-15 pounds), and also clear up the middle of the bike frame for placement of stuff.
I'm also going to replace the MTB shock fork with a regular 10-speed fork, no shocks, very light, and then work out a headtube shock system with whatever I have on hand for later, which should weigh less than 1/2 of what that MTB shock weighs. (it's currently at least 10 pounds, maybe 15).
If I manage to take the max off of each one, that'll take at least 50 pounds off the bike. Even if it's just the minimums, it'll be at least 15-20 pounds. Any lightening will help my tires, wheels, and also make less work for the motor to do especially in acceleration. And less work for brakes to do.
While I'm at it, I'll see what brake system I can fit on the rear, because I've put that off long enough.
All these things won't happen at once, but over several days, since I need to use the bike a few days this week off and on.
Now, I *am* worried that this is going to weaken the frame for cargo capacity and whatnot, but really, the bike has always been too heavy, so heavy that it is a chore to pedal without having the motor and batteries on it--because apparently it weighs around 90-100 pounds BY ITSELF!
So it's time for the bike to go on a diet, and lose some weight. :-)
Saturday, September 12, 2009
On the Endless Sphere forums, in a thread regarding hub motor cooling, someone proposed a very interesting idea:
jsplifer said: "Basically you modify the suspension to pump a fluid through one way valves in order for the fluid to make a loop through the motor, and through a heat sink/radiator mounted somewhere."There's a link to his sketch of the idea in that thread.
It made me start thinking, and in a moment I had a more complex but improved idea for essentially the same thing. Below is essentially the post I made there, preserved here on the blog too, in case I need to find the idea later:
Rather than modifying the shock directly, use a lever and/or gear system to take the very small linear movement of the shock, and convert it into a long linear throw for pumping much more volume, using an external little pump. That way you could just bolt it on any bike, rather than modifying a specific shock fork (the modifications of which would be different for each one, too).
All it would need is to connect between the crown and the U below that where the screw mount is often unused (when they come equipped with linear pull or other types of brakes using the studs).
The compression between those points could act across a lever, or could have teeth on a straight strip that engage a rotating gear, which (if necessary) in turn engages a different sized gear to give the ratio needed for high speed pump movement.
Also, one-way valves would be unnecessary, just use a ratcheting gear (freewheel) so it only goes one way, and connect that gear to a regular little motorized fluid pump, just not using any power on the motor--driving the shaft from outside, instead. This way if you really needed to, because of being on a really smooth road, you could still power the pump to cool things.
It's more complicated, but would be even more efficient, as much more coolant could be moved thru the system in much less time.
The same system could be used on the rear shock for a rear-mounted hub motor (which could probably not be done, at least not easily, with the original method).
It is even possible to tie both ends together to make a larger circulation system (but it would get heavier quick due to more fluid in the system).
This system could be used to cool controllers and/or battery packs as well as motors.
I have some stuff laying around somewhere that could be adapted to test this, to try cooling my wheelchair motor without using an electric pump, using some parts off a PC liquid cooling system.
Additionally, though it would not generate a lot of power, using a small motor in place of the pump in that same setup would generate some electricity, more on bumpy roads than others, and depending on how sturdily the system was built, would even provide some damping of the shock system (but slowing it's response, so shocks would not be absorbed quite as well, if the motor/generator was under too high a load). It could possibly generate enough power to run small LED lights, at least, on a rough enough road. :)
Thursday, September 10, 2009
One of them would basically have me running "dualies" in the back, so even if one tire pops I still have the other, etc. It would use a double rim, with independent tires and tubes on each, but both laced to the same hub.
This would require a wider hub and axle, so I'd need to modify an existing one to lengthen it. The hub should be easy to do, but I'm not totally certain about the axle. I think I would have to do the axle first, and in addition to welding a section of another axle into the middle of it, I'd also want to lathe that down to flush surface and then weld some tubing over that that is longer than the added axle piece.
Then I would use one of the thicker-bodied hubs, cut it in half, place the axle between them (since it will no longer fit thru the axle hole from outside), and weld them together with proper diameter tubing sleeved over the outside of the central hub.
I'm not sure if everything would remain as hard as it should after doing that, so it might not work as well as I'd like.
I'd need to use longer spokes for some of the cross-lacing, and I have some older likely 700c wheels that might have the right length. I am not certain how it will affect wheel strength to do this kind of lacing, where every other spoke will go to opposite rims.
Another option is if I have any hubs with enough space between holes to drill new spoke holes in them, I could drill a complete new set of holes in each flange, and lace up each rim to it's own set of holes.
A third option is to weld a second set of flanges on the hub, and give each rim it's own pair of flanges, just as if it were two wheels physically joined.
I'm not yet sure if I should weld the rims together or leave them so they can individually flex to handle loads on their own--I suspect the latter would be more effective.
The wider effective tire would probably make straightline riding a bit more stable, but introduce some funkiness in turning. Double contact patch means double rolling resistance, but it also means double drive power and double braking power.
Well, that is, if I also build a rim brake that's twice as wide. :) Or come up with some way to build disc brakes out of my junkpile of regular brakes, 5.25" harddisk platters, and other stuff like that.
I'm still pondering it, and may never even attempt it. More web research is in progress to see if anyone else has tried this and hopefully posted their results.
Tuesday, September 8, 2009
I'd installed a 25-amp circuit breaker between battery pack positive and the rest of the system, as I thought it would be helpful to prevent potential short circuits, given my jury-rigged wiring and stuff. It turned out to not be nearly enough for the startup-from-complete-stop power demands of this motor.
Having the breaker pop as I pull out into traffic to make a lefthand turn is very bad. :( Can still pedal but it's really hard without the motor, unless I have time to flip the clutch lever to disengage the gearbox! Like going up a REALLY steep hill. One reason I still keep considering a shift-lever cable-actuated clutch disconnect. (Another reason is possible motor runaway should a controller fail short circuit).
So I took the breaker out. I'll have to live with the risk of wire harness shorts, and just minimize them as usual. Better that than getting hit by a car!
I suppose I could put two or three breakers in parallel, but I'm not sure how well that will work if something *does* short.
I would use one of the 100A fuses out of the UPS, but I prefer something resettable, so I don't have to dink around with wiring around it if it gets blown on the road somewhere, either because of a short or because of a motor overcurrent, that I can fix.
Right at the moment, CrazyBike2 is undergoing a mutation with the 26" rear wheel tests. This is going much better using a wider steel rim with a regular 7-ring freewheel cassette than it did with the narrow aluminum one that bent.
Speaking of that, here's some pics of that rim. It's more obvious that it's bent without the tire on it.
I have it stacked on top of the rim I am going to use to replace it, once I get the freehub relaced into it.
Yeah, it's pretty bad. I'm surprised I couldn't really feel it that much while riding--it looks like I ought've been going THUMPETY THUMP down the road, but it didn't.
A side by side shot shows the rim i will be using is not quite twice as wide as the one that bent:
I'm hoping the extra width will also allow the tire to better support the bike, giving it more room for air inside the tube, and better side-loading resistance during turns, against the weight of the bike. Also when it's parked, since it rests on the bottom edge of one cargo pod, tilted to one side, plus the tires, it side-loads the wheel then, too, though it's static rather than dynamic.
I don't have it laced up yet, so I'm using one of the rims off the old Kensington "spare" upright bike, which I've been kind of parting out for some of my experiments and repairs to both this bike and the Columbia upright, my main "spare" bike (which is still short a rear wheel till I lace one up for it, since the bent one was from that, though I can in a pinch put the original first wheel it had back on, which has some truing problems I need to fix).
It's not as wide a rim as the one above, but it's close, and it's also steel. It has a regular thread-on freewheel hub, so I put the 7-ring cluster from the 24" wheel on to it, and back on the CrazyBike2. You can see it a little in the pics below (about the derailer). I've ridden about 10 miles on it now, and it works as well or better than the aluminum one that bent, and the current draw (and road speed per ring) is lower than it was with the freehub with the lower tooth count on each ring.
The tire I used is narrower and rounder than the Kenda Kross road tire I had been using on the bent rim, mostly because the chainstays are not far enough apart for that tire to not rub a little, even on a non-bent rim. I used the only other road tire I have, which is the "spare" for the upright DayGlo Avenger's front tire, a Cheng-Shin with a more car-like tread, which appears designed around a wet road environment (but is still smoother by far than any of the 24" tires I have).
I can still reach 20MPH on the next to highest gear, and haven't tried to see what the max is on the very highest, but I suspect around 22MPH, on motor alone. I don't intend to use that speed for anything other than emergency "passing gear" in case of a situation in which going faster is a better solution than braking, which does not happen very often, but on occasion has been something I would like to have had (would have saved me lots of panic).
Plus it would probably suck about 25-30A doing that, and kill the 17Ah batteries in only a few minutes.
The point of the bike is not speed, but rather range and ease of riding, as well as comfort and cargo capacity, all in roughly equal parts.
Now, I mentiond that the Cheng Shin tire is narrower than the Kenda Kross, but since I put it on the wider rim, it "balloons" out more because the bead is spread wider. Effectively, it is almost as wide as the Kenda, but not in the same place, so it's not as bad a problem.
So, until I get the chainstays spread a tiny bit more where the tire passes between them at the front, the little ridges (where whitewall would be on some tires) around it's sidewall rub ever so slightly on the chainstay tubes, just enough to cause a really interesting "robotic motor" whine while I'm at speed going down the road. It's such a high pitch it gets dogs looking around, but people can hear it too, for at least a couple hundred yards.
It sounds so strange, it grabs their attention. Not loud, but definitely an ear-catcher. Wish I had a quick way to record it, but it isn't picked up right by my camera. Gotta dig out the old recording studio stuff for the computer and set it up, before I fix the problem, because it is such an odd sound.
Funny that it would sound so much like a really high speed servo motor/gearbox, because the actual motor/gearbox is nearly silent!
Since I forgot to take pics of the "new" derailer, here's the one I'm using now:
You can see the gap between the top and bottom derailer wheel cages that lets one simply drop the chain right in there. I don't understand why they're not *all* made like that, because it is MUCH easier to deal with, and makes even pulling the wheel off to change a tire easy. Just lift the chain out, and now you don't have to deal with the derailer's spring tension pulling the chain taut while you're trying to pull the wheel out or put it in!
A clearer but more distant shot, above.
Another pic I forgot to take before, of the battery strapping:
It looks stupid, but it works fine until I get something better. Maybe someone will submit it to "ThereIFixedIt". ;-)
I was riding along on the way home from work last night when the multimeter started reading really wierd, then suddenly the motor stopped. I was afraid I'd burned out the motor windings or something, but a quick check revealed the motor wasn't even hot yet.
I pulled over under a streetlight, and verified the circuit breaker wasn't popped, so I disconnected the DMM I was using as a voltmeter for the pack voltage, and metered across first the breaker, then the DMM I was using as a motor current meter, with the motor engaged and set (with the clutch disengaged) to half throttle. There was no voltage across the CB, so that's ok, but full voltage was across the DMM, so that meant something was wrong inside that.
As a quick fix, I just unbolted the wires running into it from the banana plugs on it and bolted the wires directly together, bypassing the DMM's shunt, and everything worked ok motor-wise.
When I got home, I opened up the DMM, and found this:
It's a little hard to see in that pic if you don't know what you're looking for, so here's a bigger one:
The solder holding the shunt to the PCB has actually **MELTED**, and the shunt has come completely out of the PCB thruhole at the top end.
Wow. Well, considering it's only rated for 10A, and even that is almost certainly a limited-time spec (can't remember the specific time, but this is the $2 Harbor Freight Centech DMM, so it's probably in the online PDF manual for it if you are just dying to know). With the testing I've been doing it's probably had 30-50A thru it for quite a few times for at least a second or three during acceleration from a complete stop, and had constant 6-11A thru it during cruising for at least several minutes at a time.
So I really wasnt' that surprised that it failed like this, only that it took this long to do it.
I soldered the shunt back on, and now it works fine again. :)
I'm thinking of taking the shunt out of that failed 30A panel meter and temporarily adding it to this one, if I can figure out if there is a way to recalibrate this meter to read correctly with the larger shunt (probably not).
If I can't, no biggie. I have some mA-scale panel meters that I can put that shunt in, instead, and mark the current draw on them based on my Fluke's readings thru the same circuit, then draw up a new faceplate in the computer, print it out, and put it behind the needle of the panel meter. It'll be accurate enough for my purposes, plus I love analog meter displays. :)
But for those of you using those cheap meters, be careful with the 10A range--they're not fused, so you'll melt the solder holding the shunt in, possibly burn the PCB, and maybe even melt your DMM's casing, if you do what I did and aren't lucky enough to have the shunt fall out before anything *REALLY* bad happened. ;-)