E Quad considering dual hub motors, have questions

[neithermovingnorstill]

Update: Turns out this won't work, as Gray Kard pointed out, the quad has single sided hubs, so hub motors won't work because they need support on both sides. I'll either have to run mid-drive, or choose another steed.

Hi,
After test riding one, I'm seriously considering a quad (quadricycle).
I was very set on a delta trike (two wheels in rear), which would be easy to motorize with a geared front hub motor.
Then I tried the quad, which is basically impossible to tip, and rides like a gokart. Fun.
Motorizing the quad however, poses a challenge. I wonder about dual geared front hub motors, but have concerns:

I have read that a unified throttle causes one motor to be powered preferentially, which would be disastrous if they were side by side. Any ideas on how to mitigate this? Would I stuck with two throttles? Why can't the two throttles be mechanically merged, while remaining electrically separate?

Front vs Rear:
The quad has a differential, so it already has 2WD in the rear. So if I put em up front, it would have 4WD.
(Although this is significantly undercut by the fact that the differential does not have positraction, meaning that if one wheel is off the ground, the wheel on the ground stops being powered by the pedals. D'oh. Lightfoot makes a quad, and their 2WD option has positraction, but the price difference is significant)
Also, I might go with IGH in rear (to get rid of the low hanging derailer) which would rule out rear hub motors.
I'm not sure how it would work if I used a single rear hub motor, since it has a differential?
I suppose it might make sense to go with mid-drive, but I had settled on geared hub motors for simplicity, and being able to pedal at a different cadence from the motor.
To keep cost down, I'd probably go with MACs or even MXUSs.
Is this too crazy to work?

 

[Rassy]

First, which you are probably already aware of, most places do not allow quads on public roads and multipurpose paths.

The issue concerning throttles on dual hub motor applications comes up frequently. It is still my belief that a single throttle paralleled to equal controllers powered from a common battery pack that run equal motors will not be a problem.

My experiences with several two and three motor applications, mostly two wheel pusher trailers, never exhibited any "fighting" problems. However, it is possible you would feel some steering pull on the front of a tadpole trike or a quad. So far I've never seen a report from someone that put two hub motors on the front steering wheels.

 

[neithermovingnorstill]

Thanks Rassy, I''m glad to hear you think it should work to use one throttle.
I live in California, where a bicycle can have any number of wheels:

VC 231
Defines bicycle as a device upon which any person may ride, propelled exclusively by human power through a belt, chain, or gears and having one or more wheels. Specifically provides that persons riding bicycles are subject to Vehicle Code provisions specified in Sections 21200 and 21200.5

And a motorized bicycle can either have 2 to 3 wheels and go up to 30mph (and produce 2HP or less) and not need pedals,
OR it can have more than 3 wheels, but then it may only go up to 20mph (and produce 1000w or less) and must have pedals:
http://www.dmv.ca.gov/pubs/vctop/d01/vc406.htm

Thanks for the word of caution. I think if I lived in a place where this was not the case, I would try riding one anyway.
Safety laws are usually enforced when there is an obvious danger, and those laws were written before quads were available, so in the unlikely event of a ticket, if I didn't want to just pay it, I might argue that the law is outdated and not intended to be construed to ban quads. They tip less easily than trikes, so if trikes are ok, there really is no argument to punish quad owners.

 

[dogman dan]

I've always thought it would be fun to make a skid steer trike or quad, especially if you have the reverse function enabled on a joystick for each motor. Let the other wheel or wheels caster.

Maybe just me, but I find the skid steer loaders and mowers a lot of fun to operate.

 

[motomech]

Don't worry about electrical vulgarities when doing 2WD w/ geared motors. Things like, "sync'ing, "push", etc. don't manifest at moderate power levels.
Your problems will be mechanical.
A pair of MXUS motor would have pleanty of power and will be easier to mount.
One throttle will work, but two are more fun.
Here's how I do mine;

left-hand half twist with a thumb next to it

Easy to operate and intuitive.

 

[neithermovingnorstill]

Dogman: I'm assuming skid steer means front wheel drive so the rear wheels can slide around a bit? I hadn't thought of that, but it does sound fun.

Motomech: Good to hear. Thanks for showing me your setup, that looks great, it would never have occurred to me to combine two types of throttle. After reading your post, I realize that it's not necessary for both front wheels to be powered equally/simultaneously all the time, so it makes sense to have two throttles, for tight turns, or if a motor dies on the road. Your setup makes the two throttles much easier to use, since I could still have one hand free to signal, or drink water etc.
I had assumed the front wheels need to be powered together or it would veer to one side, (like how wheelchairs pivot when you push one wheel) but delta trikes usually only have one wheel drive.
It might be fine to actually just have a single front hub motor, but the idea of 4WD is just too tempting

 

[dnmun]

richard has a thread somewhere on how to adjust the throttle signal by adding a resistor so the throttle does not have the dead space at the bottom.

if you use identical controllers, then you would adjust the throttle dead space resistor for each controller so that the controllers both were starting at the same position on the throttle so that the further increase in throttle would give similar power outputs from each motor.

someone may have a link to that thread and it will be easily implemented. you could use a trim pot to find the right resistor value and then just replace the trim pot with a fixed resistor for permanent solution.

 

[neithermovingnorstill]

Thanks Dnmun, I didn't know they had dead spots, it's good to know there is a workaround if it bothers me, which I imagine it would.

I had imagined using a unified throttle, with a dial that could rotate the power balance from left to right and equal in the middle. It could either be continuous, or just have the three setting. If it was continuous, it would need some kind of divet/mechanism to help it click into place in the center, so it was easy to realign. Three settings might be a lot easier.

 

[motomech]

Or run the throttle signal thru a Cycle Analyst, then to both controllers.

 

[neithermovingnorstill]

Update: Turns out this won't work, as Gray Kard pointed out, the quad has single sided hubs, so hub motors won't work because they need support on both sides. I'll either have to run mid-drive, or choose another steed.

I have added this note to the original post as well.

Sorry everybody - it was too good to be true, an off-the-shelf 4wd e-quad will have to wait till the technology advances.

 

[motomech]

Don't give up so easily, what about a this motor?


No lack of speed with a pair of those.
Might speedily empty your wallet though.
You could use less battery and perhaps save some there.

I guess one would have to run backwards.

 

[The fingers]

I've seen dual hubmotors on electric wheelchairs with single sided axels similar to this, so they are out there. :wink:

 

[shock]

Why not run the quad with only 1 hub motor on one side? My first gas gokart was setup this way, one driving wheel so a differental is not needed. Wow factor would not be as cool as 2x, but one would work to get ya rollin.

 

[neithermovingnorstill]

My evil plan is revived!
Well, sort of.
Thanks for that Motomech, and The Fingers.
Shock, that might make it more doable, thanks.

I had given up on the quad, so I went ahead and bought a used tadpole etrike which just needs a battery and controller and it should run. It was a lot cheaper, but the quad is the dream, so I won't forget it.

 

[ian.mich]

Couldn't you buy a regular hub but use one axle side?

 

[sigimem]

@ dogman also i would like the idea of a skid steer quad it puts a lot more stress to the frame and requires much torque from the motors, so I guess you can go efficient and lightweight or skid steer :| .

 

[Kingfish]

My first EV was a 3-wheeled handicap vehicle, a Schwinn frame conversion back in 1986. Front wheel like a regular bike, and rear as 2 independent wheels. The left side rear wheel was driven by a 24V high-speed motor with internal reduction to chain-driven sprocket.

That was fine for a school project, but an asymmetrical single driven design is flawed for anything beyond experimentation. If you must use a single power source then use a transaxle to distribute power to both wheels, otherwise performance will be really disappointing. Imagine getting stuck in the muck, one wheel spinning out, the other - sitting there like a lame duck. Transaxles, and more precisely posi-track/limited-slip axles kick in to get the vehicle moving again. The other weird behavior is driving over slick surfaces such as in light rain on asphalt, frost, painted stripes, etc. It's like you are steering a boat to correct for drift; the one-side drive will always try to turn you. My 3HV only went 11 mph; I can't imagine the torque above 25 mph - but it has me thinking in perilous terms. I don't care for it.

You have the option to do it correctly. Make it so. :wink:
~KF