OSET 20R - Traction & Power Delivery

[mobiledd]

My son is eight and is the final year of the D Class. He is a reasonably good little rider, riding the hard route in OSET Cup events and in Adult events the Sportsman route. Due to his physical size we haven't moved onto a Beta 80 like the majority of his friends. OSET bikes have been fantastic for us, he has had the 12.5R, the 16R and now the 20R but now his friends are on petrol hikes and he is getting flustrated with the bike.

He finds it hard to find traction despite me running about 2 to 6psi, depending on the conditions and venue. We run two rim locks on the rear with a Cheng Shin tyre (I am not aware of any other tyre option, is there?).

But I think the main problem is the difficulty in getting smooth power delivery, especially at this time of the year when we are riding on wet ground. If I could get smooth bottom end power delivery for him without losing the power to get over obstacles while possibly reducing the throttle delay it would be great

We use Boost batteries from Keith, and he has recommended the Kelly KDS72200E controller what are peoples thoughts / experiences?

I have also been reading threads about changing the throttle, again what are peoples thoughts / eperiences?

TBH I have very little technical knowledge / ability so I would really appreciate any guidance.

Thank you in advance. 

Edited March 6, 2019 by mobiledd

[breagh]

Hello, I've got a 20r with a lithium battery which is mainly used for practice. My 13year old rarely has it spinning as I think his extra weight helps a lot as the bike weighs nothing.

Just a suggestion but is there any way of moving the footrests back  mine has bolted on brackets which give about an inch but there's plenty room on the frame to move them further back. 

[lennie]

I think the thing with a oset compared to a petrol is you have no clutch to slip when riding in tricky conditions, this would defiantly help with the wheel spin problem feed the power in slowly using clutch and throttle or rev it up and dump the clutch for big stuff.

I watch my son on his oset 20 he has just moved up to that size bike but if I turn the power up so he can wheelie over a log the power is too instant on slow turns. I don't see a way around it,

[gwhy]

I would like to try to throw some light on this subject if I can,  There are 2 types of motor control ( controller ) there is speed control and torque control and some controller mix these 2 to blend these types of control. The current going through the motor generates the torque and the voltage regulates the velocity ( speed ) . With a speed type controller the max Current that is allowed through the motor is fixed at a maximum level  at any throttle position i.e 100A  , so for example when you twist the throttle this send a voltage to the motor proportional to the throttle position ( so the more voltage the faster the wheel rotate ) which sounds fine but the problem with that is very slow throttle control is difficult..

think of this extreme example of a speed based control at very slow speeds:  you are approaching some large slippery stones at a very slow speed ( maybe 1/3 throttle position ) and the approach is flat, at that moment the Current will only be high enough  to produce enough torque to maintain momentum on the flat as you come to the first stone the front wheel hits the stone and decreases you momentum but not enough so that you come to a stand still and the bike still moves forward, when the rear wheel hits the slippery stone this then decreases the momentum even more by which time the front wheel have also dropped into a ridge and if you did not increase the torque the bike will become stationary so you twist the throttle a little more to try a push the front wheel through the ridge , you may have to increase the throttle much more than needed to achieve this ( because the voltage to motor generates the needed current ( torque) you may have to increase the throttle position to 2/3 just to keep up the bikes momentum to overcome the ridge ), all is good upto this point  but as soon as the front wheel comes out of the ridge the current then drops but you still have a 2/3 throttle speed demand at the rear and this can then break traction on a slippery surface and so the cycle continues.

There are good torque controllers and there are bad ones, the kelly controllers allow you to mix the 2 types through the programming software and can achieve pretty good results, but ideally the 2 systems should be independent of each other unless you also setup electronic motor breaking ( normally done through the throttle).

Torque based only control would be comparable to riding a petrol bike at full throttle all the time and  using the clutch to regulate speed, which is fine when there is a load on the bike i.e uphill or over stuff, but riding down a hill velocity will just keep increasing unless you also shut the throttle off  , and this is where a blend of torque a speed is needed to maintain good control of the bike.

I think this is why a lot of people have problems with the osets ( electric bikes in general) for very slow control, a electric bike needs quite a bit of torque (on a speed based controller this can mean you need to twist the throttle 1/2 of its travel before it generates enough current at the motor) to start moving but the instant the rear wheel starts spinning the torque ( current ) drops but  speed is still dialled in to 1/2 throttle (speed), some people learn to compensate others dont this results in very jerky throttle control at very slow speeds.

Edited March 7, 2019 by gwhy

[gwhy]

1 hour ago, lennie said:

I think the thing with a oset compared to a petrol is you have no clutch to slip when riding in tricky conditions, this would defiantly help with the wheel spin problem feed the power in slowly using clutch and throttle or rev it up and dump the clutch for big stuff.

I watch my son on his oset 20 he has just moved up to that size bike but if I turn the power up so he can wheelie over a log the power is too instant on slow turns. I don't see a way around it,

I look at a clutch on a petrol bike is torque control and the throttle on a petrol bike is speed control and when riding a petrol bike you mix the 2 to achieve nice smooth riding..

 

the power control sets the maximum current limit ( i think depending on the oset controller ) if that control was used as a clutch function on the handlebars then this may solve the problem but then you will also need to move the rear brake on the handlebars to a foot brake.

Edited March 7, 2019 by gwhy

[breagh]

When I watch the boy on the 20r he's no real issue with the power delivery. what I notice is the "snatchiness" at very low speeds as the chain takes up slack.

I suppose they don't run a tensioner as it would wreck the motor bearings but you wouldn't run a petrol bike without one.Keeping the chain correctly tensioned will help this but wont solve the issue,maybe a very lighty sprung tensioner would work? 

[gwhy]

8 minutes ago, breagh said:

When I watch the boy on the 20r he's no real issue with the power delivery. what I notice is the "snatchiness" at very low speeds as the chain takes up slack.

I suppose they don't run a tensioner as it would wreck the motor bearings but you wouldn't run a petrol bike without one.Keeping the chain correctly tensioned will help this but wont solve the issue,maybe a very lighty sprung tensioner would work? 

there should be no slack in the chain on a oset as the chain stays at a fixed length , you need a tensioner on a petrol bike  (engine in the main frame ) because the distance changes as the suspension goes up and down

[micm]

GWHY..."I look at a clutch on a petrol bike is torque control and the throttle on a petrol bike is speed control and when riding a petrol bike you mix the 2 to achieve nice smooth riding.."

A useful comparison, thanks. The take off or slow speed control seems to be the Achilles' heel of the battery bikes, not so much the battery life itself.

Perhaps that is why the new adult Gas Gas TXT-E and the Mecatecno Dragonfly Electric bikes (neither bike is on the market yet) have 'proper' clutches and gears as well. 

The new Electric Motion Sport has an 'electronic' clutch called a PELS system. It allows you to semi disconnect the drive as if slipping a normal clutch from the quite powerful single speed motor, but it's still a bit different to a normal clutch. 

[ninefives]

On 3/7/2019 at 5:24 PM, micm said:

GWHY..."I look at a clutch on a petrol bike is torque control and the throttle on a petrol bike is speed control and when riding a petrol bike you mix the 2 to achieve nice smooth riding.."

A useful comparison, thanks. The take off or slow speed control seems to be the Achilles' heel of the battery bikes, not so much the battery life itself.

Perhaps that is why the new adult Gas Gas TXT-E and the Mecatecno Dragonfly Electric bikes (neither bike is on the market yet) have 'proper' clutches and gears as well. 

The new Electric Motion Sport has an 'electronic' clutch called a PELS system. It allows you to semi disconnect the drive as if slipping a normal clutch from the quite powerful single speed motor, but it's still a bit different to a normal clutch. 

I've ridden/pwned competed EMs since the first pre-production bike in Canada - I think 2014.  The low speed ability of the EM has been stellar.  Hanging stationery half way through a steep uphill cambered turn, the power can be fed in and the bike crawls forward completely under control.  I see the addition of a clutch as giving the ability for splatter type riding where you need to build potential energy and apply it in an instant, I honestly see no other reason. I don't do splatters, because they will do it back to me.

I came to this topic because  a young fellow was riding an Oset 20 yesterday and the throttle was unworkable.  No reaction for a half turn and then a very delayed power response.  I cannot believe the bike comes like this.  Is this just adjustment?

Edited March 23, 2020 by ninefives

[oldtrialer]

If the throttle is the same as the 24R, you can put a piece of plastic in the groove in the throttle tube. this will take up the play in the throttle. You just remove the cap where the wires go in to access. The cap is the throttle stop.