Brake advice please

[greybeard]

Handicare Puma 40, AMT 6mph motors. FWD.

The right hand brake no longer operates. The motor functions fine, but if stationary on a downhill slope the right drive wheel rolls forward, turning the chair to the left.

I took the cap off a spare motor and saw that the freewheel lever opens a microswitch that must isolate the brake to prevent it engaging.

Looking for some pointers for what to do to make the faulty brake work properly again.
Thanks.

[Burgerman]

It works the opposite way.

The brake is always on when not powered up.
As you move the joystick from the centre, it clicks and the brake is powered up. That releases it. As you centre the stick, and the chair stops, the power is removed, and the brake clicks, on. Its like a handbrake that is always on unless powered up.

The microswitch is there to cause an ERROR on the joystick. It senses that theres a break in the cable to the brake. And so the chair wont run the motors. The lever you pull, manually releases that same brake. So the motor can turn.

So... You problem can be 2 things.
1. Brake is worn, and so it slips. Most of mine are a bit like that after a years hard use. So it needs replacing.
2. The lever that releases the brake is somehow holding the brake off when it should not be. I suspect that its 1. above.

Only some careful examination will tell you for sure whats up.

[ex-Gooserider]

I would add the possibility that there is corrosion or other crap that is keeping the brake from engaging properly...

There is also a very slight possibility that the connection between the motor and the brake is slipping...

It is probably NOT electrical, as most electrical failures would have tripped an inhibit that keeps the chair from moving and would give an error code on the joystick.

Taking apart and examination is the only way to go.... It's pretty easy on a motor that is out of the chair, harder with it in the chair just because of access...

Typically under the cover you will find some screws that hold the brake coil on, remove them and the coil will come off. The coil assembly has inside it, the brake disk, a pressure plate and a spring. It will have a sort of hex-nut looking socket in it. A bolt the with the right size head can fit in and be turned w/ a pair of pliers on the bolt shank... With power off, you should not be able to turn the socket at all, or only w/ great difficulty... When you apply the right voltage it should turn easily.

Start by making sure the freewheel lever isn't holding the brake open at all...

Then if it doesn't go 'clunk' when power is turned on and off, it suggests that either the disk is frozen in place, or the spring has died - try some wiggling back and forth, possibly some penetrating lube, cleaning solvent, etc. to get it moving, and keep working until it seems reliably free...

The hex socket in the brake fits over a hex bit that will be on the motor shaft - usually there are one or two small Allen setscrews that hold it onto the shaft, make sure those screws are tight, and locked into any flats on the shaft. The hex bit should not have any play between it and the shaft...

Hope this helps,

ex-Gooserider

[greybeard]

Thanks for the suggestions.

[Scooterman]

On the subject of ramps and brakes. Why does my scooter roll back down the ramps when stopped halfway up? I thought the electric brake was supposed to prevent that?

[Irving]

On the subject of ramps and brakes. Why does my scooter roll back down the ramps when stopped halfway up? I thought the electric brake was supposed to prevent that?

There's a limit to how steep a ramp the brakes will hold on - depends on brake material, holding force of brake springs and ramp angle - usually 6 - 15 degrees for brand new brakes. That looks a lot steeper...

[LROBBINS]

Irving,
I'll bet the brakes hold on grades of 6-15 percent, not 6-15 degrees. A 15 percent slope is only 8.5 degrees, and a 15 degree slope is a whopping 26 percent.

[Irving]

Irving,
I'll bet the brakes hold on grades of 6-15 percent, not 6-15 degrees. A 15 percent slope is only 8.5 degrees, and a 15 degree slope is a whopping 26 percent.

Hi Lenny, you are right, that was a boo boo due to brain fade... it's been a long day already...

[rlnguy]

In addition to the steepness of the incline, every system I've ever seen had a delay before the brakes engage.
This is to allow the chair to come to a stop, before they lock-to minimize the chance of user being (possibly) thrown from the seat, when the brakes lock.
During that delay, on a steep incline, the chair will roll some.

[wheelie junkie]

In addition to the steepness of the incline, every system I've ever seen had a delay before the brakes engage.
This is to allow the chair to come to a stop, before they lock-to minimize the chance of user being (possibly) thrown from the seat, when the brakes lock.
During that delay, on a steep incline, the chair will roll some.

Adjustable in a Dynamics system but AFAIK R Net doesn't let you adjust this. There are a couple of parameters you can use in Wizard software for this. On my off road chair I have it slightly longer to reduce skidding but it will roll back on a steep incline.

[shirley_hkg]

irving is right . Check brake is not held up first. Then try one at a time :
1, take out the brake plate and disc for cleaning .

2, Add a small item to the base of those springs, so that springs are exposed further before compression. That is meant to increase compression / pressure.

3, roughen the surface of the brake plate.