Electronic clutch / inverted hall signal - assistance required

I am just beginning a Fat Bike Trials conversion.

I have a rudimentary understanding of electronics, but cannot design anything.

What I would like to put together, as simply as possible, is a clutch lever that proportionally cancels the throttle signal. Nett effect should be that you can twist the throttle to full with the clutch lever in and nothing happens, hold the throttle and ease out the clutch and the controller should ramp up progressively until it reaches full throttle when fully out.

Video example
[youtube]2w7iJWABctk[/youtube]

Ideally I'd like to use a hall throttle control.
I have no real idea what to do on the clutch side of things!

A possible complication is that the clutch needs to be consistent in positioning for zero (or other) output. ie at a certain position the final output is always zero, irrespective of how much throttle is applied. It wont work if the clutch position for zero (or any other percentage) is always moving about with throttle movement.
Another way of describing this is that if I pull the clutch in fully (fully is actually only part-way, it hits your fingers) and then twiddle the throttle it will stay at zero output. If it's at 50% clutch in and twiddle the throttle it will send 50% of the current throttle signal to the controller.

gwhy! appears to have made a trials bike with this setup using an arduino, but it seems that build thread has gone AWOL. I'm still hunting through the 67 pages of his posts!
I'd prefer no to have to get into building and programming a digital controller if I can possibly avoid it.

Conceptually, it sounds like you could achieve this using a potentiometer as a voltage divider between the signal wire from the throttle and ground. On one extreme, it would drop the signal to 0v and on the other it would equal the output of the throttle in whatever position it happens to be in.


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E-HP said:

Conceptually, it sounds like you could achieve this using a potentiometer as a voltage divider between the signal wire from the throttle and ground. On one extreme, it would drop the signal to 0v and on the other it would equal the output of the throttle in whatever position it happens to be in.

Click to expand...

That sounds suitably low-tech for me.

A few clarifications if you could please:
1. The Nucular has over/under voltage detection on the throttle to protect against failures. If the throttle is close to the low voltage end and the divider is at it's biggest V drop, would that result in an under voltage signal to the Nucular and so a shut down? The thresholds are configurable but I'm guessing if the divider was too high resistance then the difference between a short and the high resistance setting might be too small to be functional.
As you can tell, my understanding of these things is very sketchy!

2. How would I pick a suitable pot value?

3. Am I right in thinking that if eg. the pot was at 50% deflection, then the throttle full span would be 0-50% of normal? This could be pretty nice, having on-the-fly throttle sensitivity adjustment! Added bonus feature.

Thanks a lot.

bikerpete said:

That sounds suitably low-tech for me.

A few clarifications if you could please:
1. The Nucular has over/under voltage detection on the throttle to protect against failures. If the throttle is close to the low voltage end and the divider is at it's biggest V drop, would that result in an under voltage signal to the Nucular and so a shut down? The thresholds are configurable but I'm guessing if the divider was too high resistance then the difference between a short and the high resistance setting might be too small to be functional.
As you can tell, my understanding of these things is very sketchy!

2. How would I pick a suitable pot value?

3. Am I right in thinking that if eg. the pot was at 50% deflection, then the throttle full span would be 0-50% of normal? This could be pretty nice, having on-the-fly throttle sensitivity adjustment! Added bonus feature.

Thanks a lot.

Click to expand...

For #1, it may be tricky. Normally I'd suggest adding a fixed resistor in series with the leg of the pot that goes to ground. However, since the input voltage will vary due to throttle position, the resistor can't be fixed. I have to think about that more.

For #2, 10k seems to be a good value that works when using a pot with a throttle when using it, similarly, to adjust the minimum voltage output, so probably good in this application as well.

For #3, the output would be proportional to the throttle voltage setting. So, if the throttle were set to output 3V, then the pot would adjust that voltage between 0v and 3v.

I don't know how trials works, but maybe you can explain how you use the controls, and maybe there's another solution that gives you the same level of control.

E-HP said:

....
I don't know how trials works, but maybe you can explain how you use the controls, and maybe there's another solution that gives you the same level of control.

Click to expand...

This could get bigger than Ben Hur, but I'll try to keep it brief and just cover the broad points.

Trials is lots of slow speed maneuvering over obstacles, often stationary and balancing then literally jumping the bike onto an obstacle and immediately stopping again.

A throttle is very hard to control with the precision and speed required. A clutch has the advantages of your hand being braced on the bars and just one finger running the clutch. A twist throttle tends to bounce around as you jump and so on.
Sometimes twisting the throttle as fast as you can simply isn't fast enough, and going from zero to max and back to zero in maybe a meter is nigh on impossible with a twist grip.

The solution is a clutch. Wind up the throttle to the power setting you want (approximately) then dump the clutch. You can dump the clutch and get off the throttle virtually simultaneously to achieve a burst of power then immediate stop.

ICE engined trials riding above the most rudimentary level is all about balance and clutch control.

There's lots more to it, but that gives the idea.

I'm actually working to fit a mechanical clutch to a motor and into the fat bike (there's plenty of discussion been had around that elsewhere, so not going into it here), but an electronic one could be much simpler to make, and adequate on a fat bike.

bikerpete said:

A clutch has the advantages of your hand being braced on the bars and just one finger running the clutch. A twist throttle tends to bounce around as you jump and so on.

Click to expand...

have you tried a thumb throttle?

or taking a thumb or half grip twist throttle, and modifying it's input rotary section to give you teh form of control grip you want to have.

amberwolf said:

bikerpete said:

A clutch has the advantages of your hand being braced on the bars and just one finger running the clutch. A twist throttle tends to bounce around as you jump and so on.

Click to expand...

have you tried a thumb throttle?

or taking a thumb or half grip twist throttle, and modifying it's input rotary section to give you teh form of control grip you want to have.

Click to expand...

Haven't built the bike yet, so tried nothing.

But it's definitely going to be a clutch lever or nothing at all.
The fine control of a clutch takes years of practice to develop, I don't have the time or patience to develop the skills on another input device.

Hi bikerpete,

I agree that the potentiometer route would be the easiest to implement, and was thinking how you might mechanically make it happen.

This video that a poster I was working with had a neat homemade solution... just replace the throttle cable with a clutch lever cable.

https://youtu.be/mCWXkSVuOw8

Although I would have put all the components inside a weather proof box. There are also store bought remote throttle boxes, just giving you food for thought.

Regards,
T.C.

TommyCat said:

Hi bikerpete,

I agree that the potentiometer route would be the easiest to implement, and was thinking how you might mechanically make it happen.

This video that a poster I was working with had a neat homemade solution... just replace the throttle cable with a clutch lever cable.

https://youtu.be/mCWXkSVuOw8

Although I would have put all the components inside a weather proof box. There are also store bought remote throttle boxes, just giving you food for thought.

Regards,
T.C.

Click to expand...

That's pretty much what I have planned if the mechanical clutch proves too hard.
I'll possibly make a pulley rather than a lever so it's a bit more linear in it's response (or I can make it cam shaped if I find I want to make it non-linear).

The remote throttle boxes I've found have all been hall effect. I've got a couple on the way although I think they'll be used for throttle rather than clutch.