Observed trials bike designing

General Discussion about large electric scooters and motorcycles and other things with no pedals.
Altair   1 kW

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Re: Observed trials bike designing

Post by Altair » Jul 20 2020 6:08pm

bikerpete wrote:
May 02 2020 6:46pm
/snip
To have a manageable throttle there must be some ramping, but for the clutch we want none.
How about a switch on the clutch lever that when the lever is pulled switched the controller to no-ramp mode. This might make the effect of pulling and releasing the lever more similar to a mechanical.

Still doesn't solve the flywheel issue, but it's possibly achievable today.
Just to be sure we are on the same wavelength, does "ramping" for the throttle refer to either:
Slew rate limiting of the throttle signal, which limits the rate of acceleration of the motor, or:
Non-linearity in the throttle signal, which produces an exponential response curve, resulting in less throttle sensitivity at low openings, and more at higher openings.

Personally, I don't like slew-rate limiting because it kills the small throttle corrections you need to make on rough terrain.
Non-linearity is the thing. Some controllers have a choice of different curves, others allow you to "bend" the curve as you want.
However, if your controller doesn't have that feature, there is a way to accomplish non-linearity if you have a resistive throttle. By adding a trim pot between the wiper and the ground connection of the resistive throttle, it becomes possible to obtain a VARIABLE curve that you can adjust to your liking. I've been wanting to order a Domino throttle for quite a while, to be able to develop that.
It's on my "to do" list, I promise. :wink:

One (small) problem with a non-linear throttle is that you never quite get used to the sensitivity of the throttle, because it's different for each position. But this is still better than a straight throttle.
However, on a low-power bike, the straight throttle won't be much of a problem, while a high-power bike will be difficult to ride at low speed. There's also personal preferences in all of this.
End of rant.

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DanGT86   100 kW

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Re: Observed trials bike designing

Post by DanGT86 » Jul 20 2020 10:29pm

Glad you are back in the thread.

The Domino throttle is the best thing for any ebike. I love mine. Well worth the money.

I didnt realize you could tune the curve with resistors though. I thought you could only remove the deadband at the bottom or change the max point to an earlier position. I assumed it would always stay linear though. Is this not the case? Could it be made exponential/progressive with just resistors?

bikerpete   10 W

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Re: Observed trials bike designing

Post by bikerpete » Jul 21 2020 5:32am

Nice to have you back Guy.

I was thinking slew rate with the throttle stuff, but really I still think an electronic clutch is a very poor cousin to a "real" clutch.

Altair   1 kW

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Re: Observed trials bike designing

Post by Altair » Jul 21 2020 8:30am

Yes, the response curve of a pot can be distorted away from linear, by adding a single resistor between the wiper and the ground connection.Depending on the value of the resistor relative to the value of the pot, the curve can be "curved" away from linear.
Check the article here:
http://electro-music.com/forum/phpbb-fi ... mz_168.pdf
The graph for the Log Taper shows how the curve is affected. The resistor could be replaced by a pot, which would then allow to vary the distortion of the curve at will.
Other articles: http://www.geofex.com/article_folders/p ... tscret.htm
https://www.qsl.net/om3cph/sw/pot.html

There is a problem however, in that the very low end of the resulting curve is distorted in the wrong direction, as seen on the graph. But it would be possible to eliminate this small part by either, limiting the mechanical rotation of the throttle so it cannot go as low. You will then adjust the controller settings so the minimum is now at that new voltage.
If not possible, you could try to just set the controller input to "Hall" instead of "0-5V". By doing so, the controller now expects an input voltage between 1 to 4V. You might now have to limit the maximum mechanical opening of the throttle to stay below 4V.

Those are the things I was planning to experiment with, once I have a Domino throttle. :roll:

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DanGT86   100 kW

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Re: Observed trials bike designing

Post by DanGT86 » Jul 21 2020 9:10am

Interesting. I find that I like a little less rotation than the domino has anyway so having to limit the bottom of the rotation is not a bad thing. The logarithmic curve in that link might be exactly what I am looking for trying to tame my cheap speed based controller.

bikerpete   10 W

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Re: Observed trials bike designing

Post by bikerpete » Apr 08 2021 5:49am

I rather abandoned this thread and the time has come to explain why.

I was reasonably well down the track of building my dual-suspension fat-bike based e-trial bike when I happened upon an interesting e-trial that seemed pretty similar to what I was planning.
Now after something more than a year communicating with the manufacturer, testing the bike and putting everything in place I have started importing and selling these bikes in Australia.

So my e-fat bike is returning to it's original role.

This new bike runs a brushed motor and a simple controller, with a 2-speed gearbox. The combination is responsive and effective. The LMX motor and Nucular controller I have will fit nicely into the bike, so I'll fit them at some stage.
Maybe I'll get as far as integrating the clutch and flywheel as I'd planned with the e-fat bike - we'll see. I still think a flywheel and clutch is a key enabler for some trials moves, although I've also learnt that a light, responsive, clutchless e-trials bike has it's own attractions.

If you're interested, http://www.dobbikes.com.au
Last edited by bikerpete on Apr 08 2021 7:19am, edited 1 time in total.

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spinningmagnets   100 GW

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Re: Observed trials bike designing

Post by spinningmagnets » Apr 08 2021 7:04am

Do you have any pics of the 2-speed gearbox internals?

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Re: Observed trials bike designing

Post by SlowCo » Apr 08 2021 7:17am

The link you posted doesn't work as it puts the E-S site in front of it.

Nice looking bike and a smart 2 speed gearbox! Any more info/specs on that box and maybe even a possibility to buy those seperately for home builders?

It reminds me a bit of the Oset bikes:https://osetbikes.com/au/bikes/new-20r- ... order-now/
Although I would prefer the Sur Ron Light Bee at that price point:https://www.surronaustralia.com.au/surr ... egal-d4nbl

bikerpete   10 W

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Re: Observed trials bike designing

Post by bikerpete » Apr 08 2021 7:17am

spinningmagnets wrote:
Apr 08 2021 7:04am
Do you have any bnb pics of the 2-speed gearbox internals?
No, I haven't pulled one apart yet. It's on my list of things to do!
It's impressively compact - 10ml is the recommended amount of oil!
I'm guessing it's straight spur gears inside from the sound and feel of it.
There's no syncro, but it changes quite nicely either stationary or moving (not under power).

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Re: Observed trials bike designing

Post by bikerpete » Apr 08 2021 7:26am

SlowCo wrote:
Apr 08 2021 7:17am
The link you posted doesn't work as it puts the E-S site in front of it.

Nice looking bike and a smart 2 speed gearbox! Any more info/specs on that box and maybe even a possibility to buy those seperately for home builders?

It reminds me a bit of the Oset bikes:https://osetbikes.com/au/bikes/new-20r- ... order-now/
Although I would prefer the Sur Ron Light Bee at that price point:https://www.surronaustralia.com.au/surr ... egal-d4nbl
I've edited the link so it works now.

I don't think the gearboxes will be available separately any time soon - mostly because at present the demand for the bikes in China is so high that they're flat out keeping up.

Yes, it's very similar to the Oset - kind of overlaps both the 20" & 24" Oset. I think it's a nicer build than Oset in several areas, although Oset has it's own advantages.

It's a very different beast to the Sur-Ron - I don't really see them in competition at all. The Sur-Ron is rubbish as a trials bike in comparison, and the dob will never compete with the Sur-Ron as a fast trail bike. Sur-ron weighs 50kg vs dob 35kg.

SlowCo   1 MW

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Re: Observed trials bike designing

Post by SlowCo » Apr 08 2021 7:49am

It does seem to sit in its own niche indeed. The more bikes like these to choose from the better :thumb:

Grantmac   10 kW

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Re: Observed trials bike designing

Post by Grantmac » Apr 08 2021 10:30am

I've said time and again that what a lightweight Emoto needs is a 2-speed, preferably a deep reduction and a direct gear.
I think a clutch and flywheel would be an asset however.

How does the bicycle sourced air suspension hold up?

Altair   1 kW

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Re: Observed trials bike designing

Post by Altair » Apr 08 2021 10:51am

I love it! It is small, light & cute.
Do the tires have a good grip on wet rock? The knobs seem a bit small. Are they made of a good compound?
Tubeless or not?

bikerpete   10 W

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Re: Observed trials bike designing

Post by bikerpete » Apr 10 2021 3:01am

Altair wrote:
Apr 08 2021 10:51am
I love it! It is small, light & cute.
Do the tires have a good grip on wet rock? The knobs seem a bit small. Are they made of a good compound?
Tubeless or not?
There are two tyres available (3, but the third is not a great option for any condition so we ignore it):
Kenda Krusade 20 x 4 - quite low profile knobs but largest volume and softest, grippiest rubber. Better for hard surfaces.
CST 20 x 4 - bigger knobs, more ramp on them in one direction, lower volume. Better for softer surfaces.

It's been summer here so wet rocks haven't been on the menu. With winter coming I guess I'll find out soon.

I tend to think riding this bike should be considered closer to riding an electric trials bicycle rather than a trials motorcycle - the technique is closer to a bicycle than a moto, although there's a fair bit of overlap.
Grantmac wrote:
Apr 08 2021 10:30am
How does the bicycle sourced air suspension hold up?
As well as any suspension I guess. If you service the forks periodically then they should last a long time. The rear shock is working exactly as designed, and well within it's design pressure/load so it should last many years if kept clean.

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