Anyone have experience with front + rear motors?

[OCD Garage]

Recycled, tilting, recumbent, reduction-drive trike

I cut up my drift trike to make a tilting, recumbent trike that was both fwd and sketchy AF taking off from a standing start. It was fun enough that it has now been converted to rwd but I'm looking at it wondering if it would be okay as a 2wd (one front, one rear) and may offset some of the new found torque steer to the right. Could I add a second controller (connected to a Y-splitter for the throttle). Would I have to be concerned with one motor over-speeding the other or need to use a Cycle Analyst to scale back the power of the front motor? I believe the current battery should be able to supply enough amps for the two controllers.

 

[amberwolf]

My Crazybike2 was front/rear 2WD hubmotosr in the wheels for much of it's lifespan.

The new Schwinn-based alternate / replacement for SB Cruiser will be AWD (middrive rear, hub front).

If both your motor systems are direct drive hubmotors in the wheels, then as long as they are the same winding and wheelsize, they'll spin at the same speeds in most situations, whether powered or not.

If they're different, then whichever one is faster will create less voltage when backdriven.

If one is a middrive then it won't be backdriven or create regen if you have a freewheel betweeen it antd the wheel. So ti won't be affecterd by a DD in a wheel's output.

You can use two separate CAs if you like, one on each system, to keep their outputs matched at whatever point you want them to be by limiting the system taht would be faster so it's only going to go as fast as the slower one at the same point in the same sitaution.

if you need to match two unmatched systems for all loading and situations and speeds, you'd probably have to create an MCU-based system thatmonitors everything and is programmed / calibrated on each one so it can make each one provide the proportion of total system power/etc that you want it to, for each load/situation/speed.

I never really bothered with any of that, not even for the SB Cruiser's 2WD rear wheels-only setup, and not had problems with the setups doing things I didn't want. That includes not having issues with controllability due to one side of SBC pushing harder than another during acceleration at various speeds due to diffeerent motors or different windings of the same motor on each side, or different controllers on each side (there wasn't a problem with this even if I only used one of the motors, with the other unpowered).

I *did* have problems with *regen* using different controllers on each side (the motor didn't matter that much) because each one had different ways of causing regen, and different amounts it could create. So one that could regen high currents vs one that only did low curretns would drag to the side with high currents during braking, though it was still controllable you could feel it. But a tandem (front-rear) motor setup like crazybike2's didn't have that issue...and I could also easily use different levers to control each motor, jus tlike you would for the mechanical brakes, for the same reasons.





There are many threads for 2WD or AWD bikes/trikes/etc including my builds that you can look around for more results.

 

[OCD Garage]

Thanks AW: Of course I started by searching different combinations here and on Google and came up with many unrelated hits. I found a few AWD/2WD but not much useful info that pertains to me. I'll keep digging, just thought as the motor wheel is up front doing nothing now and before I build a motor-less front wheel... may have to experiment once the current snow level here drops.

 

[OCD Garage]

I did find this link to a YouTube video from Justin that delves into the subject of multiple motors/combo hub + mid drive etc. It's lengthy but likely contains good info.

 

[classicalgas]

I've done a couple bikes with both front and rear motors ( on the same bike at once) I run two separate systems, making no effort to get them to talk two each other ( two each controller, battery, motor) or even match output. As long as you don't have enough torque (or low enough traction) to spin the front wheel it works fine. Your brain figures out how to limit front toque under low traction conditions pretty fast with two throttles.

Front wheel drive trike? With a tadpole, I think that torque steer and loss of traction would be a problem, With a delta, just loss of traction/wheel slip.

Edit: I should note that I typically run either two geared hub motors, or a torque sensing mid drive and a rear geared hub. The second is especially nice to ride, and that setup seems to work well on a tadpole trike as well.

 

[lnanek]

People have mentioned you can link two VESC controllers to support keeping two identical motors at the same RPM even if one slips.

 

[OCD Garage]

The Exoquad - the ultimate all terrain wheelchair — EXOTEK Here is a good example of what I'm interested in, a quad designed for those with mobility impairments that uses two single sided hub motors up front and two motors running through chain reductions to each rear wheel. You can choose from 2wd or 4wd. These things are torquey, able to stop and start off again on a set of steep stairs or dirt hill. I know they are not going to answer my questions about their proprietary designs, but I'd be interested to know how it's done.

 

[amberwolf]

Thanks AW: Of course I started by searching different combinations here and on Google and came up with many unrelated hits. I found a few AWD/2WD but not much useful info that pertains to me.

What did you find irrelevant about them?

Unfortunately your original request at the start of the thread doesn't give enough specifics for what you want to know, other than the bits I already answered with the info I have.

Most of how a 2WD (+) system will behave is up to the specifics of your actual usage, terrain, and how you choose to set it up and control it.

 

[OCD Garage]

Thanks AW, I'll keep digging.

 

[OCD Garage]

The above link to the video from Justin fills in most of the blanks with regard to multiple motors, whether mirrored side to side, front and rear or combining mid drive with front hub motor etc. There is a lot of explanation about how they would work together and suggestions about how to match them to work together, etc. Definitely worth watching if you are reading this post already.

edit: Just found this video where the dual motor setup created an issue, then was problem solved by cooperation from the members of this board... go team!

 

[OCD Garage]

So the answer to running multiple motors from one throttle seems to be: (1) to bridge the (-) wire and sensing wire from the primary controller throttle to however many controllers you're using, (don't connect the 5v+ or it will cause weird modulation problems). (2) Use the same motors where possible and/or match their top speeds by adjusting controller settings. (3) Run all your controllers from one battery (or multiples in parallel).

 

[E-HP]

So the answer to running multiple motors from one throttle seems to be: (1) to bridge the (-) wire and sensing wire from the primary controller throttle to however many controllers you're using, (don't connect the 5v+ or it will cause weird modulation problems). (2) Use the same motors where possible and/or match their top speeds by adjusting controller settings. (3) Run all your controllers from one battery (or multiples in parallel).

Just out of curiosity or maybe just for clarification; after looking at a couple of threads, are you randomly jumping back and forth between two member IDs? I see people responding to one of the ID posts, then a response to them from a different ID (e.g. post 9 above).

Recycled, tilting, recumbent, reduction-drive trike

Put together a test bench of ideas to work with. Originally fwd, I'm playing with V2 now. It's all up and running and a blast to ride. The trike develops some notable G-forces on acceleration. I'm really impressed with the hill climbing ability considering it's not really geared down much. With...

endless-sphere.com

 

[OCD Garage]

I only post on ES with one member ID: One post is about my build, it's in the build section. This post in the techical section could be applied to that build, but it is so I can learn something to apply to future projects (I'm looking to build an e-quad eventually). I'm not jumping back and forth and did discover the answer to my questions. Thanks.

 

[Patchogue]

Mine is a 2WD with synched controllers, it works brilliantly.

I just saw this thread and didn't have much time to read the replies properly, give me a shout if you have any questions but the Grin Tech vid explains pretty much everything you need to know.

 

[Patchogue]

Recycled, tilting, recumbent, reduction-drive trike

I cut up my drift trike to make a tilting, recumbent trike that was both fwd and sketchy AF taking off from a standing start. It was fun enough that it has now been converted to rwd but I'm looking at it wondering if it would be okay as a 2wd (one front, one rear) and may offset some of the new found torque steer to the right. Could I add a second controller (connected to a Y-splitter for the throttle). Would I have to be concerned with one motor over-speeding the other or need to use a Cycle Analyst to scale back the power of the front motor? I believe the current battery should be able to supply enough amps for the two controllers.

If it's just one motor in the front, most likely you will have torque steer. But regarding the concern of one motor pushing more than the other, with the Grin Tech bits you won't have that problem. You can even tune each controller separately.