Roll Away Brake on Demand

2013 e2
Is there any way to invoke the roll away safety brake?
I’m after hill holder at a light

I think the modern carts do that via a coil and a brake disc. It is actually a power to release/no power to lock deadman brake/clutch.
These Gem motors will need some serious engineering to fit one of those. They do not come standard.

Or are they actually doing a hill hold through the AC motor like an extension of regen/electric braking?

Yes, that is what we do with the Sevcon controllers and AC motors.
I don’t have a stock 16+ GEM car but I don’t think that feature is enabled by default. We can do it an AC conversion of a 05 - 15’ GEM car.

In a roll away event I feel the motor hold the car
Or when I’m at a light after some time around 30 seconds I can hear a solenoid engage/disengage & some sort of electrical hold occurs, I can let my foot off the brake

I had to go back up to read the OP has a '13 car.

A real savage/brute force way to do this would be to rig a pin on a cable that would jam itself into the fins on an air cooled armature.

Sounds like a great way to scatter some parts too.

Is this on your 2013 Gem e2?

I swear a few of us talked about this some time back… I seem to recall that there is an anti-roll back “feature”, but what I don’t remember, is that if it’s independent, or part of another parameter on the controller.

Seems to be related to field weakining

T4 manual is here:

Just built one like that for SueZ-Q. But solenoid controlled.
Needs a shaft to connect sprocket for the pin to engage. In my case motor had a stub shaft on free end of motor.
Also needs a zero speed switch which the Sevcon has. I don’t know how to access it in a ge controller. Could be done through the speed sensor i guess.
My next one will be a reverse acting line lock in rear brake line.
Solenoid will be normally closed. That way it will “remember” brake pressure when motor reaches zero speed.
It will take some getting used to, as it will only work if braking to a stop.
The same n.c. solenoid can be connected to a switch. Greatly simplifying the control system.
I think it a safe design. Front brakes are always available. Any failure mode only disconnects rear brakes. It can not activate them during a control failure.

***** Warning: Free thinking zone ahead. *****
Random thoughts may be damaging to those that like to stay all comfy in their box.
Reality and Physics sometimes do not apply here.

I was trying to imagine an easy way to extend the motor shaft a bit so a small brake disc can be bolted on.

  1. Something that can installed on to the coupler? Press fit with a keyway on the coupler end. This would mean the brake/coil all needs to fit inside the tight space in that end when the motor is mated to gearbox.

  2. Weld on a shaft extension the Comm end? The Speed sensor will need to be moved out a bit more or go to a Hall switch to send the speed pulse? We start getting close to the tire zone on the ling motors.

  3. Weld on a shaft extension the input shaft and extend out the gearbox side? Plenty of room over on that end. The gearbox case would need to be cut for the longer shaft and another seal to worry about leaking. Good that you could swap motors and still retain your brake mod.

  • The pin in the cooling fins was more/less an exercise to see how much force it would take to pull the pin out when under load. I’m not sure a coil has enough to reliably pull to go.
  • Parts - Maybe use the ring coil and clutch from an ACond compressor? Need to figure a way to reverse the action to being “energized → brake off” condition.

  • Control - The action and timing of the Main Contactor might be something that can be tapped into.

I was going to spit out to a new thread, but I guess it’s on topic.
SueZ-Q is in the bsmt for a coming picture.

That’s the trick. I used a 12v solenoid and powered with capacitor discharge from 48 volts, thru a M.C. type relay. Current limiting resistor after pulling in.
Sevcon is set up for this. They have 3 coil drivers and one can be mapped as “brake”.
Logic is set to pull with motor speed over zero.
The line lock method is much simpler to implement.
Connect “resettable one-shot” relay to the speed sensor. Every pulse pulls solenoid in for xx ms. Timeout starts over every pulse. Miss a pulse and brake line locks. I guess it can be called a missing pulse detector logic as well.

Set the delay long enough, 4 pulse=1 rev, to be able to touch the brake pedal. Brake will remain at that level until motor moves.
May need off delay as well. As if sensor toggled only 1 pulse, brake would release, car rolls back, and not hold until the next cycle.

Bed needs to come off for better picture.
Sprocket, lever, solenoid.

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like clockwork. Nice! Really helps that the controller is involved too.

The plan was that pawl skipped teeth if accidently engaged at speed. It actually works too. Bms tripped a couple times on regen going downhill. Not scary at all. Just a buzz as pawl skips over the teeth.

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I was thinking more along the lines of
Trick the controller into thinking that the cart has run-away after stopping?
A push button sends few pulses to the motor sensor circuit if the throttle off switch is made

I could use the same thing on my modded ezgo, as the run-away function is better than the rear drum only brakes on dirt down hills
I lock the back wheels for a couple of seconds, let off & run-away kicks in, giving me a nice controlled descent

Roll away yes, but not hill hold. AFAIK

Look here in case you have thoughts of an ac motor conversion.