Recumbant Mid-Drive Scrapbuilt Buildlog. Pics & Questions.

[MattsAwesomeStuff]

how about this one?

I dunno let me look...

"The criteria to building the bike, is, well, to uh, not spend any money." <-- I like it already!

Not too much I can use, since you're reusing triangular frames, but, gave me some more ideas.

Power-side pulleys or sprockets are becoming intimidating to me, since people are suggesting they be 4"+. Hopefully I can get away without that. Second biggest concern is if I include rear suspension, how I will manage chain flex. The pivot will have to be between the crank and the rear wheel, so it will flex on the power side. I don't know how much, or how much is too much or enough to warrant a spring-mounted tensioning pulley.

[amberwolf]

For suspension vs chain growth, if you're willing to build the pivot point as a jackshaft, you can end the power side chain there and begin the wheel side chain at the same point. Then there is no problem, other than a very small efficiency drop from the extra teeth/chain friction.

Basically all you need is two sprockets that are joined axially, and both can ride on a bearing on the pivot shaft *or* on the tubing of one of the frame sections on either part that pivots on that point.

As long as the sprockets and the pivot share the center point, there's no chain growth, and no tensioner needed. .

[REdiculous]

Maybe, you're saying that I'll be gearing the motor way down to turn the big crank slow enough, which then turns the back wheel at a higher rpm than the crank?

Right. If you want the wheel to spin 250-500rpm, say, then why reduce the motor down to 80rpm just to bring the rpms right back up?

The right-angle looks beefy enough but there'd have to be a damn good reason to use it or I'd fine another way.

I went way off the reservation w/ my build because I wanted to see if my idea would work, and how well. Now I've got the most powerful 12v ebike on ES...lol...sometimes it's better if we just ignore the questions, advice and criticism so we can push on w/ the original plan.

[MattsAwesomeStuff]

As long as the sprockets and the pivot share the center point, there's no chain growth, and no tensioner needed.

Right right. But this is a contingency plan, 'cause I'm not sure I can pull that off. So, suppose I have to put the pivot 1" away or something.

[MattsAwesomeStuff]

A hundredpack of 10A anti-reversing diodes. I ordered these before I understood LiIon chemistry better. When hooked up one per series cell, these prevent batteries from being negatively charged via over-drain in series, by bypassing the battery if its voltage ever hits zero. I.E. They'll stop NiCads from ever being destroyed by being over-drained. But LiIons are already toast under 2.7V maybe, but certainly under 1V, let alone getting drained until negative. I might install them on my battery pack anyway (I'll need 42 of them if I have 170V) just because they're light, add no bulk and would prevent a dying battery from exploding.



Also, the 90-degree outboard motor gearbox arrived today:



It is a 2:1 geardown, and quite small. The bottom bulb is half the size of my fist.

One complication, it has no bearings, just seals, and the gears grind badly if it's not aligned both tilt-wise and depth-wise. This is a pain in the ass but not insurmountable.

So, the motor might be a little bit overpowered. Bit of a difference in shaft sizes here...



And the "completed" driveline:



Too much geardown as is. I'll have to remove, at least, one of the drill geardown stages.

As-is, with all 4 stage geardowns:

3200 RPM @ 130V.
90' gearbox is 2:1 so 1600 RPM.
The drill is 38:1 so 42 RPM
The drive sprocket will be ~3" and the rear cassette varies from 4.5" to 2.5", so, between 1.5:1 and 0.8:1, so between 28 and 53 RPM.

The rear wheel is 26"=0.66m or 2.07m circumference, so between 3.48-6.69 km/hour. Or, between a slow and a moderate walking speed. *Fail Stamp*

Kill one of the 6:1 geardowns in the drill gearbox.. 21-41 km/hour. Not bad. And if I use 170V instead of 130V like it's supposed to.. 27.5-53.7 km/hour.

Still a bit weak. I'd like a max speed a bit higher than that, batteries will drain too, so, maybe I'll upgrade to a 4" drive gear and increase those numbers by 33%.

Hrm, let's see if I get rid of the drill gearbox entirely, but pulse it on average at 130V still.. 126-246 km/hour (75-147 mph). Nope. Guess not.

4" drive sprocket it is. 37 - 71 km/hour (22 - 42 mph). Slower is not a problem, can do that electronically.

I guess the next step is laying it all out and start disassembling/cutting.

[MattsAwesomeStuff]

So I'm a bit stuck on what to do gear-wise. Maybe some of you with experience can help.

I'd ideally like to get rid of the drill gearbox entirely and just go Motor --> 90'. It's less weight, less bulk, less bracing, less machining, less figuring, less noise, etc. I put the numbers out there in the end of my previous post. But I'll update them presuming the actual battery voltage I'll be using. Let's deal in RPM rather than speeds.

Rear Tire RPM (26"), I want roughly 200-600. That's 25-75km/hour (15-45mph).

Wide open throttle, my motor spins at 4200 RPM @170v.
The 90 degree gearbox is 2:1, so, 2100 RPM. Those two are set and not changing.

I need somewhere around a 4:1 geardown still. Some of this could be done electronically, but I'd rather have my wide open throttle actually capable of hitting a high speed rather than never being able to go above a 25% duty cycle for example.

The easiest way is to make the drive sprocket quite small. How small could I reasonably make it? I've heard people say never go below 3-4", though I don't know why. I presume more tooth wear? The rear cassette will be a normalish cassette.

I'm also about to have a million bike-related questions about disassembly and connecting things and all that. But, baby steps.

[Lebowski]

don't forget that when you ask lots of power the motor will bog down by a certain %, so your
reduction should maybe be like 3:1 instead of 4:1 . I always liked the idea of using a read-axle
of a bicycle as a reduction axle. Drill out the spoke holes and attach a big sprocket. You can take
the reduced off of the X-mas tree (sorry can't think of the correct word right now). If you do
it correctly it will even give you a one-way freewheel so you can pedal without turning the motor
(for when the battery dies).

[MattsAwesomeStuff]

Drill out the spoke holes and attach a big sprocket.

The problem with this is that I want to actually use the rear gear, not have one big freak sprocket. If I was okay with a single speed, this would be fine.

I'm considering it though, because my motor is overpowered enough to slam its way up hills at speed without issue, which is the only reason you'd ever really need rear gears anyway. That and so you can pedal normally.

My motor can handle 2000-2500W continuous, conservatively (as in, that's what it's safely rated for).
Uphill 10% @ 50km/h (30mph) takes 2500W.

So if I go with electronic speed control and a single huge rear sprocket, I might never get into trouble. It's starting to get tempting.

But, more so interested right now in how small a drive sprocket could be.

[amberwolf]

I think he means to use a separate rear hub as a jackshaft, so that you have the freewheeling sprockets on one side and a fixed sprocket on the spoke flange.

[MattsAwesomeStuff]

I think he means to use a separate rear hub as a jackshaft, so that you have the freewheeling sprockets on one side and a fixed sprocket on the spoke flange.

So, moving the rear sprockets up to a middle place between gears, and then using a big sprocket at the wheel?

Well, the whole purpose of this is to eliminate a stage. I have the drill gearbox to geardown if I need it, I just want to eliminate a stage if possible.

[MattsAwesomeStuff]

Trying to get at freewheels. Bike question time. I'm a bike mechanic novice.

Here's a rear wheel from a Shimano mountain bike:


Here's the rear stuff from a single speed kid's bike (with backpedal braking):


Both should have freewheels yes? I can't figure out how to get them out/off.

I've read Atomic Zombie's tutorial on freewheel disassembly, but I can't quite put the pieces together (or in this case, take them apart).

I believe the top one is a cassette-style freehub, and the second is a threaded freewheel?

Help?

[Warren]

The top picture is a cassette mounted on a freehub style hub.

http://www.parktool.com/blog/repair-hel ... el-service

The lower picture appears to be parts from a single speed, coaster brake hub. No "freewheel" ratchet and pawl stuff in one of those.

[MattsAwesomeStuff]

Thanks Warren! I guess the whole cassette just slides right off the splines.

The lower picture appears to be parts from a single speed, coaster brake hub. No "freewheel" ratchet and pawl stuff in one of those.

So it's fixed like a kid's tricycle? There's no ability to coast? I figured it was a BMX type thing, with backpedalling to brake but still coasting when forward.

I have a couple others bikes I can gut for freewheels, I'll look into those next.

Thanks for the tutorials.

[MattsAwesomeStuff]

Update.

Mostly have been stuck on the gear ratio thing and not knowing what direction to take it. This, in turn, has been holding up any frame fabbing 'cause I don't know what will have to go where yet.

Progress:

- Stripped about half of the red (little, front) bike. Started at the back since I'm using the front as-is. Might use the rear gears/derailleur under the seat at the drive gears. Will use the (nice) brakes). Chain was great.

- Stripped about half of the blue (big, rear) bike. Rear gears are in great condition, long teeth and durable, they don't make them that way anymore. Rear tires are nice and fat, good for the weight. Left the rear as is and stripped from the seat post down. Tossed the crappy cantilever breaks. Kept the chain and front derailleur. Yanked the cables out, will re-use. Seat post came with a handy trailer mount.

- Got a chain breaker tool and figured out how to use it. Harvested 4 chains so I'm probably good for those.

- Sent an email to an electronics salvage place about reusing their junk laptop cells, no reply yet.

- Grabbed a couple dozen bearings from inside industrial copiers, none fit any of my shafts though.

- Took apart an old almost-junk grinder after I realized they must have 90 degree gearboxes in them, (it does, 3:1) and considered using it instead of the propeller gearbox (2:1) if I never add another geardown stage. But I couldn't figure out how to take the damned thing apart any further than the back casing.

- Did a COSTCO trip on a hardtail mountain bike and bought mostly canned goods (50 lbs worth). Threw them in the paniers and in a backpack and then kept my ass in the seat (no leg shock absorbing) up and down all curbs to see what 50lbs of motor/batteries and no shocks would feel like and how much fun it was climbing hills (what I'd be doing if the batteries died). Hills were manageable but I had to drop an extra chainring down. Square curbs are quite the crash down. Enough so I'm considering mounting the motor under the seat/top tube rather than behind the seat, to get some of the weight under the front shocks.

- Couldn't figure out how to get the cranks off their posts. Tried prybars and such. Bought a $10 gear pullet, but couldn't get the teeth in. Returned it and bought a $6 bearing puller that uses rectangular jaws rather than round ones. It just flexed and bent. Apparently there's a "Bottom Bracket Tool" for this. Some of my cranks are on shafts with a female (nut) thread, some have a male (bolt) thread. I hate buying 1-purpose tools, so maybe I could get a local bike shop to lend me one overnight. Stuck there.

- Tried to pull off the rear cassette like in Warren's linked tutorial, but they won't budge. I'm stumped, cone nuts are off, I can see clear through the other side.


It's not much but, seeing bike frames that are a lot closer to being used was encouraging.


Can anyone suggest what the smallest possible drive gear would be? I might just try going with electronic speed control and leave the bike geared for 125-250km/h WOT even if I'll never get close to it. I can't figure out a way to easily get a 4-5:1 geardown.

[amberwolf]

- Took apart an old almost-junk grinder after I realized they must have 90 degree gearboxes in them, (it does, 3:1) and considered using it instead of the propeller gearbox (2:1) if I never add another geardown stage. But I couldn't figure out how to take the damned thing apart any further than the back casing.

Post some pics, we might be able to help. Most come apart pretty easy, but also some of the cheap ones have so much lash (gear slop/wiggle) that if you really put a lot of power thru them you may well rip teeth off the gears with power from a bike motor. Also, they don't always use bearings in them, but sometimes just bushings, and those tend to be very worn in old grinders, and end up causing lash or other slop that wears gears quickly. I've got a harbor freight one that is trashed like that, becuase the bushings wore too much. Motor works great but gearbox is junked.

Keep in mind also that often the hsaft of the motor has one of the gears machined into it, meaning you must cut the shaft and create a coupler between it and the motor you are wanting to use.

- Couldn't figure out how to get the cranks off their posts. Tried prybars and such. Bought a $10 gear pullet, but couldn't get the teeth in. Returned it and bought a $6 bearing puller that uses rectangular jaws rather than round ones. It just flexed and bent. Apparently there's a "Bottom Bracket Tool" for this. Some of my cranks are on shafts with a female (nut) thread, some have a male (bolt) thread. I hate buying 1-purpose tools, so maybe I could get a local bike shop to lend me one overnight. Stuck there.

Many bike shops will take them off for you, but they usually charge for each set to be removed. Around here the going rate varies from $5 to $30, when I asked around before I just said screw it, and bought my own tool, because the tool can often be had for less than $10, which I think is about what I paid for mine.

The way it works is the cranks have threads on the inside of the hole surrounding where the nut or bolt goes in. You remove the bolt or nut using a regular socket wrench, then thread in the tool to those big threads. Tighten that down with the wrench (often part of the tool), then wrench the other half of the tool (usually clockwise, I think) to push against the threaded-in piece, which pushes the part you're now turning against the crankshaft (where the nut or bolt actually was at before), and forces the crank off of the shaft.

If you have any very large bolts with the same thread pitch and diameter as your cranks' hole, you could drill a hole in the bolts, and then tap them for a smaller but longer bolt to thread into them, and this will do the same job as the crank-removal tool.

- Tried to pull off the rear cassette like in Warren's linked tutorial, but they won't budge. I'm stumped, cone nuts are off, I can see clear through the other side.

First question: are you trying to get the sprockets off, so you can use them or the wheel hub (and it's built-in freewheel) separately, or are you wanting to use the whole freewheel mechanism on something other than the wheel hub?

I ask because that looks like a freehub type, using a cassette of sprockets that slide onto a splined section of the hub itself. The freewheeling mechanism is part of the hub, and is not easily going to be usable without the hub or at least some part of it.

Have you removed the locking sprocket(s) on the outside? Usually one or two of the smallest sprockets unscrews, or a separate lockring just outboard of all the sprockets. Depending on how they are made, it may require a "chain whip" to hold the other sprockets while you use the sprocket removal tool (splined with a nut built in for a large wrench) to loosen the small sprocket. Sometimes you just need the sprocket removal tool, turning against the locked freewheel mechanism (but it may require a very large amount of force / leverage to get it started--I've often had to use a hammer on the end of the wrench, while standing with my feet on the bottom edge of the rim to keep it from spinning).


I'll have to come bakc to try to help with the gearing--my brain isn't up to doing math right now.

[MattsAwesomeStuff]

I just said screw it, and bought my own tool, because the tool can often be had for less than $10, which I think is about what I paid for mine.

Yeah, that's what I figured. I bought a gear puller for $10 'cause at least it's useable as a gear puller too. Maybe I'll just buy and then return one if I can't borrow one.

then thread in the tool to those big threads.

Ahhhhh... the BIG threads. That makes more sense. I was thinking "Do I have to buy 2 different tools now, for the different small threads?". Duh. Great, thanks.

First question: are you trying to get the sprockets off, so you can use them or the wheel hub (and it's built-in freewheel) separately, or are you wanting to use the whole freewheel mechanism on something other than the wheel hub?

Either/or. General disassembly. I think I will have a single big gear at the cranks, and then mount a cassette under the seat (so I'll have 1 rear set at the rear, one rear set next to the power sprocket, coming from the front wheel).

The freewheel, I'm aware on this type is somewhat built into the hub, so probably not going to try too hard with that.

Have you removed the locking sprocket(s) on the outside? Usually one or two of the smallest sprockets unscrews, or a separate lockring just outboard of all the sprockets.

Aha. I could not find a lockring, and I could not pull the cassette off. I wasn't aware sometimes the small sprockets unscrew first.

It has spline teeth but they're only 1/8" deep. So chain whip (chain-in-a-vice for me, since I don't own a whip), and I'll make a spline tool from a bolt. I noticed when I turn them backwards it freewheels and presumed that must not be how they come off. Duh, gotta hold it with a whip.

Thanks again. Total bike noob I am.

I'll have to come bakc to try to help with the gearing--my brain isn't up to doing math right now.

I don't need help with the math. My question is related to... I see people saying things like, for power-side chain-redirector pulleys never go smaller than 3". I'm wondering about torque or tooth wear or anything like that. Like, any reason I couldn't use a very small sprocket, that wouldn't be obvious to me right away.

[amberwolf]

Ahhhhh... the BIG threads. That makes more sense. I was thinking "Do I have to buy 2 different tools now, for the different small threads?". Duh. Great, thanks.

When I first saw the tool itself, "Duh!" was exactly what went off in my head, because I had not figured out how it would work until that moment.

It has spline teeth but they're only 1/8" deep. So chain whip (chain-in-a-vice for me, since I don't own a whip), and I'll make a spline tool from a bolt. I noticed when I turn them backwards it freewheels and presumed that must not be how they come off. Duh, gotta hold it with a whip.

On the two cassettes I have here right now, both can be disassembled using the same splined removal tool that is used to take regular Shimano-type freewheel clusters off of thread-on hubs. I forget if I had to use a chain whip (chain screwed to the benchtop in my case) or not, on these, but on others I have.

It's not uncommon for me to find trashed bikes or wheels where the whole thing is rusted together, but I can still use sprockets separately if I can get them off--bolted or welded to other things for chain guides, tensioners, drive or receiver sprockets, etc. It's where I got most of the sprockets used on CrazyBike2's original powerchair drivetrain, and for the many failed attempts at chaindrive on DayGlo Avenger before that.

Thanks again. Total bike noob I am.

So was I when I started my quest almost 5 years ago...Sheldon Brown's site was the most helpful place for me learning the bike stuff.

My question is related to... I see people saying things like, for power-side chain-redirector pulleys never go smaller than 3". I'm wondering about torque or tooth wear or anything like that. Like, any reason I couldn't use a very small sprocket, that wouldn't be obvious to me right away.

Ah. Noise is one reason to keep pulleys big. The smaller they are, the tighter the angles between chain links, so the more they clatter on things they're going around. Also can cause more wear.

For drive and receiver sprockets, anything the chain is actually pulling on or being pulled by, the larger you can go the better, for power transfer. Otherwise it tends to wear things faster, or even slip right off if you are using derailers.

For instance, on CrazyBike2, using the Shimano single-speed freewheel, which I think is 14T (maybe 16, I forget) on the rear wheel, and the 48T or whatever it is on the front ring, I can pedal hard enough even with the motor putting out 2KW at startup from a stop to make the chain jump teeth (and this damages the teeth and the chain). So increasing chain tension by not using a derailer but just some other tensioning method would help that, but it might not stop it because the rear ring has so few teeth in contact with the chain. Using a bigger sprocket in the rear would fix it, too, but I'd have to super-size the front chainring to make up for that, and end up with one probably a foot in diameter.

[MattsAwesomeStuff]

Well, my source for dead laptop batteries didn't work out.

Sadly, that means this project is pretty much dead in the water for me, as, paying for batteries would cost more than a cheaper used motorbike.

A big deal on many of my project is the low barriers to tinkering. I never know 100% if it will work out, so I avoid spending. Also, I was interested in the whole "this was built entirely out of junk" challenge.

Thanks everyone for their feedback anyway. I have a couple more things to try but this was by far my best option, now sunk.

[amberwolf]

You might check stores that collect batteries for recycling, including toolpack batteries at hardware stores, places like Sears, Home Depot and Lowe's, etc, as you might be able to make a deal to take those away so they dont' have to deal with recycling them.

Computer stores and repair centers also often end up with dead or old batteries, and may be willing to let you have those, too. When I worked at CompUSA and Computer City before that, we would have given them to anyone that wanted them, as long as the manufacturers didn't require a return of them for warranty purposes.

[MattsAwesomeStuff]

You might check stores that collect batteries for recycling, including toolpack batteries at hardware stores, places like Sears, Home Depot and Lowe's, etc, as you might be able to make a deal to take those away so they dont' have to deal with recycling them.

Someone said Dewalt, I called, he said I could have all they have, and to check back in a while if I want more. Bingo. They're dead-ish LiFe, but, beggars and choosers and all that.

Computer stores and repair centers also often end up with dead or old batteries, and may be willing to let you have those, too. When I worked at CompUSA and Computer City before that, we would have given them to anyone that wanted them, as long as the manufacturers didn't require a return of them for warranty purposes.

These are the ones that are the least cooperative. There is an industry consortium that runs many of our provincial (and your state) "recycling" programs that is corrupt. Their goal is to destroy the second hand market by having free "electronics dropoffs" and such, so that people don't give or sell them away... so everyone has to buy new.

Even the "good guys" recycling programs, volunteer run charities, are jackasses. The big setback that had me discouraged earlier today was one big such group telling me if I wanted their dead batteries, $10 each. I was like "But, they're garbage to you, you're literally paying to dispose of them aren't you? I don't want the used ones that work, just the dead ones". Nope, $10 or stop wasting our time. Great, thanks, so much for the protecting the environment, maximizing re-use mission statement for this "charity". It was more the attitude than anything that got to me.

But I'll keep asking around for individual stores, maybe they're not as big of jackasses.

[MattsAwesomeStuff]

Progress:



Out of each pack, 1 or 2 cells dead. 70% working just fine overall.

Then on an old powered golf caddy I found some freewheels, (the rusting things):



And pulled off they look like so:



These are overrunning clutches, not pawl-type or ratcheting. Completely silent when coasting.



These were gifted to me, someone bought them off Ebay and ended up not using them. Not sure if LiCo or LiFe. I suspect LiCo.

A word of caution about Ebay buys of extracted batteries. Out of the box, 34 chargeable, 78 dead and gone. 30% success rate. (Compared to 70% from disassembling packs I rescued myself). These packs have clearly been picked through already, likely by the sellers, and the ones on top were, by far, the more often working ones than lower down. I suspect they threw in a few questionable ones and padded the bottom of the box with ones they knew were dead (visibly leaking electrolyte or chained to ones that were). So, buyer beware. You'd be better off buying packs not disassembled yet so you can be the lion rather than the jackal.

Batteries were all 3V+ or under 0.1V anyway, so that made Keep vs. Scrap easy.

For my gearbox I found possibly a better option. An acquaintance repairs powered wheelchairs and said I could have a dead motor/gearbox. They are 90 degree, and have geardown. He said I could have one with a working motor (24V) but I asked for one with a blown motor since I already have a motor.

Also made contacts with people at an EV shop who're looking to hook me up with some old stock, or things they don't want to repair.

Things are looking up.

[MattsAwesomeStuff]

Been slacking on this while waiting for parts for a month. But, progress is being made.

Built a massive parallel charger for the 18650-sized cells.



And picked up another load of "Dead" batteries. Still about 70% recoverable:



And then the motherscore. Had a contact hook me up with some "dead" LiPo packs and their BMSs:



65 pounds worth of LiPo. $5000 worth of cells, if new and functional. Which is somewhere around 4000Wh. Which is somewhere around 1000km (600mile) range at 25km/h (15mph) with no pedaling.

A few issues:

1 - I presume for them to be "dead" that some cells are overdischarged and gone. But they're stuck together with adhesive powerful enough that I think I'll tear (or at least bend) the bags if I try to actually remove the dead cells. So, I'll probably just disconnect them and haul their carcasses around.

2 - Cells are maybe not all matched, and with cells so large this actually matters (8 in parallel at a time averages out, 1 does not). Many of these cells seem similar, but I might find myself limited to the capacity of the smallest cell.

3 - LiPos are fragile.

4 - Charging might be an issue now, I might have to build a gigantic switchmode power supply to regulate current.

5 - I don't know how to configure the BMS in each of them, so that they'll cooperate with each other (multiple BMSs in.. series I guess).

I'd hoped to be riding back in April already, but, feature creep is having me lean towards building a better bike later than a crappy bike sooner.

[amberwolf]

Built a massive parallel charger for the 18650-sized cells.

Just beware of it not actually contacting all the ends at the same time. If you use enough clamping force, fully parallel along the wood, it should "indent" the wood wherever some cells stick up a teeny bit more than others and then get them all connected properly. I ran into problems trying to do the same thing using only two inflexible metal bars, where the cells didn't all make contact properly at both ends, as they are not all exactly identical (even the ones from the same manufacturer), sometimes because of torn-off tab welds and such.

1 - I presume for them to be "dead" that some cells are overdischarged and gone. But they're stuck together with adhesive powerful enough that I think I'll tear (or at least bend) the bags if I try to actually remove the dead cells. So, I'll probably just disconnect them and haul their carcasses around.

Denatured alcohol (or even isopropyl) will usually at least temporarily "deactivate" many adhesives, and usually permanently remove them. Just test to be sure it won't damage the cell casings first. (almost certainly will not, but check...).

Outside or in a well-ventilated area, put DA in a bowl or container big enough to partially immerse the pack in, and let it soak a few minutes, then try a plastic shim (about like a credit card but with no stamped-raised stuff on it) to slowly insert into the gaps between cells. Once a gap is enlarged a little, re-immerse the pack and soak, and keep repeating till it's all done. Alternately just use something to apply the DA to the adhesive areas/gaps and enlarge with the card, if you don't have a container large enough for the pack.

2 - Cells are maybe not all matched, and with cells so large this actually matters (8 in parallel at a time averages out, 1 does not). Many of these cells seem similar, but I might find myself limited to the capacity of the smallest cell.

You could test them once assembled into groups, under load, and see which groups of parallel cells have more voltage drop or run empty faster. Mark each group with this info, and then build a pack with the best groups. The other groups you then troubleshoot with a binary search to find and remove the problem cells, and repair with any spare cells.

3 - LiPos are fragile.

If by "LiPo" you mean "pouch cell", then yes, they often are. But remember that LiPo doesn't specifically mean that type of cell.

4 - Charging might be an issue now, I might have to build a gigantic switchmode power supply to regulate current.

Look around for old lab power supplies; usually adjustable voltage and adjustable current. FInd one that will handle all the current you need, evne if it's voltage is not high enough. Find other power supplies (with isolated outputs) that can also supply at least the max current you want, even if they have no current limiting, and can do it at at least (or more) the difference in voltage between what you want the pack to charge to and the lab PSU's max voltage. Then series all the PSUs, and use the lab PSU to adjust the final total voltage, and the max current limit.

5 - I don't know how to configure the BMS in each of them, so that they'll cooperate with each other (multiple BMSs in.. series I guess).

Maybe, but you might need diodes for that. There are several discussions from the last few weeks about that; sorry I don't have a link. Might be a wiki article with the links.
http://endless-sphere.com/w

[MattsAwesomeStuff]

Just beware of it not actually contacting all the ends at the same time. [...] as they are not all exactly identical

*takes a better photo*



Not a problem. There's at least 1/8" of compression from each, and I clamp the whole top bar anyway.

Mark each group with this info, and then build a pack with the best groups.

This was the plan when I was using many LiFe cells and had extras and an infinite supply of them. But my supply of LiPo pouches is probably, at least for the foreseeable future, limited to what I already have. So, "extras" might be hard to come by. No matter, I'll have to make do.

Look around for old lab power supplies; usually adjustable voltage and adjustable current.

I have enough electronic knowledge to build my own power supplies, for free, from dead appliances and such. At least, pegging a constant voltage anyway. But adjustable current requires actual dynamic electronic control and isn't easy to build.

The bigger problem is that my LiPo pack might be as large as 4000 Wh. The fastest I can drain a home circuit is at 1800W, so that's ~2.5 hours to charge if I'm flatlining the breaker. Charging at home, overnight, whatever is a trivial task for me. But charging on the road while making rest stops isn't as easy. An 1800W charger would weigh ~20-40 pounds.

Versus, if I was using LiFe batteries, you don't need to bother with current control on the charge cycle, I carry a power cord with a built in rectifier and smoothing cap, and a big run cap in series to limit current and I'm done. No transformer, no regulator, just right out of the wall at 120vac --> 170vdc.

Good news: Of the first 43 cells I tested, 42 of them seem in perfect condition. I'm not even sure how these got reported as "dead", even cells marked as dead show identical voltage to the others. *shrugs*. Maybe the BMS left on them for weeks/months slowly revived the dead cells.

Maybe, but you might need diodes for that. There are several discussions from the last few weeks about that

Ahh crap. I've ignored the forums for the last couple weeks since I had nothing to contribute. I'll dig around.

[MattsAwesomeStuff]

Picked up the powrechair gearbox today.



I pounded the wheel off, am left with a keyed shaft, and a 32:1, 90 degree all-in-one gearbox.



Note it also has that other shaft protrusion on the bottom left there. That is a shaft that bends like a hockey stick about an inch into it. I know it's supposed to have a manual freewheel engage/disengage so you can push it without cranking the motor. I'm not sure how it works, if you pull on it or twist it. I would definitely like to use it though, to disengage the motor when batteries are dead (4000Wh and 1000km range at 25km/h probably never, but..).

Anyone familiar with powerchairs?

Other feature: Where the output shaft (long one) comes out, next to it is another rubber plug thing. The opposite side also has this pair, (with both plugged). So 4 options total. I presume both sides is to make the gearbox flippable to the other wheel. But what is the 2nd plug on each side for? The box is literally packed with grease so I can't see anything, would rather not scoop it out without reason. Is it likely to be a two stage geardown and the other position is for using only one set of the geardown?

At full open throttle I'm at 4200 RPM (170V) off the motor, so, at 32:1 geardown, that's 131.25 rpm on the drive sprocket.

Ideally, I want 200-600 RPM on the rear wheel using the rear sprockets (25-75km/h, 15-45 mph).

So, I should have a drive sprocket that is a ~50% bigger than the largest rear sprocket and it should all match up. Except this is stupid, I'm gearing down to 131 and then gearing back up almost 5x for high speed. Would make more sense to remove one stage of the gearbox, same problem as before.

But, it's at least doable, since I don't have to contend with the extra 2:1 geardown from the prop gearbox. I have chainrings of the appropriate size. If I go 32:1 down and then back up, so be it.