Another GasGas trials bike conversion

[rynhardt]

it's easy to get used to two throttles, one for each wheel. after a while of practice, you learn to use each wheel for the best traction, just like you do with two brake levers for braking.

if you're using throttle controlled motor braking it's even easier.


if you were using a 2wd bike that didn't need independent control of the wheels, you can use just one throttle for both controllers (probably not the goal for this build).

Yeah I suspect it's just a matter of getting used to it, like anything else.

[rynhardt]

I had originally planned to run the front motor with its own throttle, controller and battery pack.. but..
..since these are brushed DC motors, I thought why not run them in series and see what happens.

[rynhardt]

I've done a bit of riding with the two motors in series, on the same controller.

With both wheels on the ground, it appears to perform much the same as before, and it's pretty much impossible to tell which wheel is providing drive.

With one wheel in the air, however, all the power seems to go to the free wheel, much like a limited slip diff. This makes it pretty useless in low traction conditions, and difficult to wheelie unless you brake the front wheel.

Which means the next step is to put the front wheel on its own controller and throttle..

[DanGT86]

What about trying them in parallel?

[macribs]

Look forward to see how you overcome the lsd issues and to see video if the bike ridden on hard core trial sections to see if the front motor will help you climb or if most of the traction will be planted in the rear tire so front will break traction before it actually helps driving the bike up the hill. Cool project. And a very unusual way to solve traction issues, but I like it alot.

[rynhardt]

I've put the front motor on its own controller and throttle, and the result is much more usable. It's also surprisingly easy to get used to the left handed throttle.

Some early experiments suggest improved capability in scenarios which would typically require more momentum or a run-up to the obstacle. For example, when your front wheel is right up against a large obstacle, you would typically need to back up and lift the front wheel to get the the front wheel to track upwards. With front wheel drive there's no need to back up.. just apply a bit of traction from the rear to press the front wheel against the obstacle and then apply traction with the front wheel.. and it climbs up.. magic

Next step is to get a LiPo battery pack and then go do another full trials event.

[macribs]

What you said about pushing with rear motor, the front tire well into the obstacle for added traction before cranking the left throttle for the front motor was very clever. I really look forward to see you video from the trail event. This time you will have much greater climb and "take off" up those steep sections. Now with two motors and two controllers.

Keep up wrenching and making em videos

[rynhardt]

Keep up wrenching and making em videos

Thanks for the encouragement

[rynhardt]

Small update - upgraded the front SLA pack to LiPo's.
I'm using two 5s 5200mah 25C packs, which gives me 36V nominal 5Ah with 130A continuous, 250A max.

The weight and space saving is significant, and performance is very consistent - no sagging under full load like with the SLA's.

Definitely a massive upgrade.

[rynhardt]

Thought I'd post a quick update.

I removed the front wheel drive. Turns out it's not that useful and the additional complexity and weight wasn't worth it. Also, they wouldn't let me compete with it. Was a fun experiment though.

I've upgraded my controller from 100A to 130A and changed the rear sprocket from 102T to 121T, giving me a very nice torque boost.
I'll post some pics of these later (they're on an old phone somewhere).

I finished another regional comp yesterday with my bike (clubman class), in some really hilly and rocky terrain.
I had some concerns about the big rear sprocket fouling some rocks but I guess I got lucky. I do want to add a chain/sprocket guard at some point.

So far, so good, and having a lot of fun with it.

The first pic doesn't do it justice but it's like a 30deg incline.

[gbeals]

Ohhh - Yes, let's see the size of that sprocket on that 18" wheel.

[rynhardt]

I finally got around to getting the video done. yay!
So here's the 121T sprocket in all its glory

[rynhardt]

I ziptied my phone to the breastplate and had a quick blast around the garden after work.
Not great footage, but super fun

[gbeals]

That is one hell of a back yard. Nice to be able to hop on a do a quick spin. Your skills must be improving big time! How much HP/Torque you think you have? Also, with your air box removed, did you add any other support for the rear fender?