Left side drive, prevent chain from derailing?

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StinkyGoalieGuy   100 W

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Left side drive, prevent chain from derailing?

Post by StinkyGoalieGuy » Sep 10 2019 6:20pm

For those of you running a left side drive, given that there is no free-wheel on that side, how do you prevent the chain from derailing given that when you are not applying throttle, the spinning of the rear wheel is actually driving the chain forward on the front motor sprocket. Typically, all the chain management features such as rollers and chain tensioners are arranged to keep the chain on while the motor is pulling the chain over the rear wheel sprocket, not the other way around.

flat tire   1 MW

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Re: Left side drive, prevent chain from derailing?

Post by flat tire » Sep 10 2019 6:23pm

Your chain line is messed up or you have too much slack. With a good chainline you don't really need a tensioner even with a lot of slack.

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Re: Left side drive, prevent chain from derailing?

Post by aCeMadMod » Sep 11 2019 5:52am

You get right chian line plus good rollers. And spings

My never come off in 3 months . Plus downhill tracks.

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ferret   1 kW

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Re: Left side drive, prevent chain from derailing?

Post by ferret » Sep 11 2019 7:55am

StinkyGoalieGuy,
the Phaserunner controller has a new "virtual electronic freewheeling" feature which helps with the problem you are describing. Only 2 rides with it, but I like it very much.

Avner.
justin_le wrote:
Jul 04 2019 6:57am

In addition to that, we've also changed some things around on the layout and added a few features. First and foremost is something that I've alluded to on our GMAC product page which we're calling virtual electronic freewheeling.

This causes the Phaserunner controller to inject a small amount of phase current through the motor winding even when the throttle is off. As soon as the motor stops turning (based on the stall timeout) then the current drops to zero properly so you don't have to worry about it wasting power when the bike is parked.

For systems that have an always engaged motor (direct drive or a geared motor with a locked clutch), what you can do is tweak this value so that it's just about cancels out the drag torque of the motor itself. Then when you let go of the throttle to pedal unassisted, there will still be a small ~10-30 watts of power going through the motor in order to cancel the drag, and the experience for the rider is exactly the same as if the motor was actually freewheeling. The downside is that this draws a bit of power from the battery (unlike an actual freewheel), but on the upside you'll almost always get more energy back from regenerative braking than you expend on this virtual freewheeling behavior.

That's our main intention of the feature, but there is another use with mid-drive or geared motor setups in order to keep the motor always engaged with the drivetrain. That way there is no windup delay and jarring kick once the motor spins and catches up with the clutch, which has been the source of many premature mechanical features.
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StinkyGoalieGuy   100 W

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Re: Left side drive, prevent chain from derailing?

Post by StinkyGoalieGuy » Sep 11 2019 12:02pm

Thanks, Avner. That's perfect since I'm already running a Phaserunner! I'm going to give that a try.

The issue came up because the freehub on my rear wheel has locked up, so now the chain is getting spun by the rear-wheel instead of freewheeling. I figured the left side drive folks have already figured this issue out. The problem is I can't get perfect chain alignment with my BBSHD. Fortunately I'm only running single speed, so I can get it pretty close, but not perfect since I need to run a pretty large sprocket in the back. If I shift it any further, I'll hit the seat stays or the chain stays. I also noticed one of the teeth has broken off on the front chainring, so I'm sure that's contributing to the chain popping off. I'll replace that and see if it helps.

devo1223   100 W

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Re: Left side drive, prevent chain from derailing?

Post by devo1223 » Sep 11 2019 3:03pm

The nucular controller has the same feature, I've been meaning to try it. Let us know how it goes. My problem is my chain keeps skipping on the motor sprocket
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