Rhoades Car: a design mess: some fixes

I'm not sure if this goes under E-bike builds or somewhere else.

A guy that has bought several of my bikes builds brought me a Rhoades Car with some problems. Originally designed as a 4 wheel pedal only, side by side tandem, this model, came with a 24v brushed motor and heavy lead acid batteries.

The owner had bought it used for 10% of new, played with it a few days and managed to burn out the controller. It's motor/controller was a 1960's design industrial set normally used on floor sweepers and pallet lifts. The cost of a new controller was too high, not to mention the performance was terrible. 10 mph on the flat with hard pedaling. I didn't have enough power for even a moderate hill, and downhill was worse. A single mechanical disc on 1 wheel had very little stopping power for so much weight.

I had a new 26" Crystalyte 5303 front wheel/motor and 48v40a controller, bought for a standard tandem build. That combo is too powerful and fast for safety, IMO. https://www.youtube.com/watch?v=s5sa6fC5Hig It's powered by 54v21AH; six, 18v10.5ah LiMnCo Makita mount tool batteries (3s2p). The controller limits the currents to 35amps (54vx35a~=2000watts).

It's about right to power this car/bike. 25mph on the flat with decent hill climbing. Mounting the motor was a bit of a challenge and the look of a 5th, pusher wheel is a bit unusual. Controlling the axle torque was very important on such a powerful motor. The left rear 20" wheel is actually 1/4" off the ground and is only for show. Probably the biggest performance improvement is braking. The 26" power wheel adds a 2nd brake (rim vbrake). More importantly, the controller's regen brake/charging circuit now does 90% of the braking. The 2 friction brakes are only need for the last few feet of a stop. Oh..... It has a power reverse too. I didn't implement the 3 speed power switch or cruise control. Too much stuff for this user.

The gearing makes pedaling possible only to about 12mph but it seems faster and feels safe and fun. The range at that speed is much better than I expected. It will go much faster, but without suspension and rather the loose steering, it's pretty exciting. Hopefully it won't be used at those speeds. Sorry, I couldn't post a video.

That's an interestng way to do it.

FWIW, you could use the hubmotor, not in a wheel, to drive the chain cog on the rear axle; mounting it similarly to how you have the whole wheel mounted now.

Because it's a front wheel, it doens't have a sprocket, but you could cut the threaded side of a regular bike hub off, and bolt it to the side cover (I did this on a 9C front; it worked fine other than an issue with me forgetting to tie down the wires out of the way of the bolt heads inside the cover).

Then you can install a freewheel, and use whichever cog on it will give you the speed/torque ratio you need with this quad.

SInce the freewheel (and threads) would not drive the cog if you just wrap teh chain around it, you'd need to run the chain *under* it, like Rassy did on his trike driven this way. So the freewheel drives the *top* of the chainline, by running the motor in reverse.

The disadvantage to this is that it loses both regen braking ability, and powered reverse. :/

Amberwolf,

Thank you for the alternate hub motor mounting idea. Somewhere in ES I saw a hub motor mounted to a frame driving a rear wheel via a chain. I thought the hub was fixed and a sprocket mounted to the axle. I gave up when I realized the wires have to spin with the axle. I couldn't figure how to solve that. Thanks for explaining.

Probably just as well. The drive axle on this thing is a 3/4" dia with a slot. The pedaling freewheels, derailleurs and the brake disk are bolted to collars and hammered on to the axle. There are 4 or 5 other collars also on the axle associated with original motor and to control bearings . The collars have a setscrew, but are not needed because it's so tight. The brake disk was originally on the left. Changing it to the right took most of a day. I suppose heating the collars would have helped.

It's the pedaling cadence that too is too fast after 12mph. But the customer is happy only pedaling to start and on hills. The overall speed of the bike using the 26" rim is about right. Some gearing flexibility would have been nice, but not necessary. Loosing reverse, I think is trivial, but loosing regen is not. Without it, new brakes would have had to been fitted to more wheels, probably all 4, to make it safe.

Is it possible to post a short video(2.8mb) directly without uploading to Utube or a server? I tried in .mkv and .mp4 format and was refused.

Firedog said:

The left rear 20" wheel is actually 1/4" off the ground and is only for show.

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Given that I'd consider going to a pusher trailer (centered on the back.) All the benefits, plus extra cargo space and a place for the batteries/controller - but the quad rides like it is "supposed" to. And you can unbolt it and get it back to normal in half an hour.

Firedog said:

Somewhere in ES I saw a hub motor mounted to a frame driving a rear wheel via a chain. I thought the hub was fixed and a sprocket mounted to the axle. I gave up when I realized the wires have to spin with the axle.

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That might be Crossbreak's geared hub as middrive thread (or one of them). That required a significant modification of the geared hubmotor he used (as documented in his thread), and would take even more modification of the DD hubmotor you have.

There are also dozens of other types of DIY middrives using hubmotors, RC motors, and other types of motors, documented to varying degrees here on ES and elsewhere.


But Rassy's method of driving hte "top" of a chainline with a hubmotor running in reverse is really simple, and easy, and allows the driven wheel/chain to rotate/move without backdriving the motor. (so it also works in the middle of a pedal chainline, which is where he used it; he also had freewheeling cranks, so the motor didn't drive the pedals if you had to stop your feet but keep motor going).

It's the pedaling cadence that too is too fast after 12mph.

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Even when shifting gears at the rear clusters? Or are they not shiftable? (if so, that should be easy enough to fix)

You can also change the gearing on the pedals. Either use a smaller sprocket on the rear, or a larger one on the pedals. Since the chainline is pretty long, you could even add a front derailer and triple to give three speeds at the cranks.

Or install an IGH (internally geared hub) as a "jackshaft" between pedals and rear axle. I did this on my SB Cruiser trike to get 3 pedal speeds, to give me a really low gear (about 1mph) and a direct drive (about 2-3mph), and a high gear (about 5mph), that let me pedal the trike unpowered for (very) short distances, in case the power system fails.

Loosing reverse, I think is trivial, but loosing regen is not. Without it, new brakes would have had to been fitted to more wheels, probably all 4, to make it safe.

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Might be a good idea to add brakes to more wheels anyway, simply because there are several ways regen may fail (generally when you're trying to use it!). The controller could die, or the batteries (if tehy have a BMS) could shutdown due to etiehr HVC or LVC (or overcurrent), shutting down teh controller and preventing regen, connections can become loose (or corrode), etc. Or the axle can break (or spin out in the dropouts) from the rockign back and forth caused by acceleration and then regen (this, plus other shock loading, broke the axle on my front X5304).

I keep telling myself I'm going to put phsyical brakes on my rear wheels on SB Cruiser, in addition to the electric braking they have now...but so far I have avoided it due to needing to redesign the frame to do it. But I do have dual rim brakes on the front, which are enough to skid the wheel under any loading I've had so far. (but not necessarily enough to stop the trike without the electric braking too, cuz most of the weight is in the back).

Is it possible to post a short video(2.8mb) directly without uploading to Utube or a server? I tried in .mkv and .mp4 format and was refused.

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AFAICR video uploads aren't allowed anmore, and all the ones that did exist were deleted back when this was changed, even though this could cause data loss of projects not documented any other way, by people that aren't on the forum anymore.

You could try renaming it to .zip and uploading it, with a note to downloaders to change the file extension back to whatever it is supposed to be.

Otherwise, youtube is your best option, since its' accessible by more people than any of the other video sites (and is easy to block the ads on).

Both rear wheels on the ground is a balance issue. It can be done.