Cush Drive Rubbers Vaporized!

So much for the new cush drive inserts, they disappeared on Sunday. The brake must have been rubbing a tad and the hub got hot enough to melt the new insert rubbers. My rear wheel looked like it had a black plastic Spider web on the spokes.
Here is the dilema, the rear brake is pretty ineffective on a good day and adjusted to be too loose doesn't help . Anybody have any experience with this?

You could try arcing the shoes like some do with the front drums. I was thinking about doing that, also because I seem to have a rub spot despite trying to center the shoes while tightening the axle. Then I heard someone had found some high friction rear shoes, maybe RGM?

Dave
69S

I've had to sand and sand and sand the high regions off the shoes going by the heat burnished appearance. Also drum then cross sanding to get some detectable grip friction. Suspect bad bearings off centering drum or some spacer wrong or missing. Be pensive on dumb axle fracture now, if being weirdly loaded like brake and heated too much. Also heated drum expands to loose grip on the staked paddles plus without any support sans cushions, check for looseness or twist to tach down. I've finally gotten mine to brake 'right' and roll free but most of least year both me and Wes had to adj. so slight drag on no brake to speak up. Did not seem to bearly warm drum after long rides. Implies should be able to find something obvious as takes a good bit of drag to melt the cushions. I had melted them w/o brake drag when paddles twisted while playing hard so they got chewed up till melted sheets oozed out the seams.

Make sure the circlip that holds the bearings in the drum hasn't come off as that will make the drum rub on the brake backing plate and cause heat to melt the cush rubbers, mine had broke the outer retaining resess, but I was able to machine the grove deeper and put a larger circlip in, to melt the crush rubbers it would have been very hot.

Ashley

kingdaddyo

Whenever you disturb the short dummy axel you need to apply the brake when everything is assembled.
Here is what I do.
Assemble short axel on swing arm loosely with the drum brake as an assembly.
Put the wheel on with cush blocks in proper orientation.
Assemble Speedo gearbox into the notches of wheel assembly; include the top hat for Speedo and large spacer between the swing arm. It’s a tight fit but should be doable without tools. (Remember you need to be able to remove the wheel for a flat if you are on the side of the road).
Put long axel and thick washer through the swing arm and through the hub centre.
Press everything up against the chain adjusters.
Stand or use great force on rear brake pedal to centralize the drum with the shoes alignment while tightening the nut for short axel first. Then do the long axel tightening sequence. I also stand on the brake when doing this tightening. keep an eye on the chain adjuster position for the axels.
If you have a centre stand, spin the rear wheel and listen for drag noise and chain hit on guard. No noise.
Go for a ½ mile drive no more and stop and check rear drum for heat build up.
If you don’t do that then the brake will drag, heat up and melt your brand new rubber cush drive rubbers into goo.
CNN

kingdaddyo said:

So much for the new cush drive inserts, they disappeared on Sunday. The brake must have been rubbing a tad and the hub got hot enough to melt the new insert rubbers. My rear wheel looked like it had a black plastic Spider web on the spokes.
Here is the dilema, the rear brake is pretty ineffective on a good day and adjusted to be too loose doesn't help . Anybody have any experience with this?

Click to expand...

You might want to check the inside of the drum when you take the wheel apart. If things got hot enough to melt the cushions the it might have melted the grease in the bearing inside the drum. Look for lines of melted grease radiating from the bearing on the inside of the drum. If it has it then the shoes are probably contaminated with grease, so they are shot. Replace the bearing with a sealed one from Walrige. 06-7688s

I had the adjuster bolt at the brake pedal back out till it caused the brake to drag. The lock nut on the adjuster must not have been tight enough and the bolt backed out, tightening the cable. You'd think the nearly constant tension of the cable from the spring in the brake would drive the bolt in but it did the opposite. Check out Vintage Brake's website regarding contaminated brake shoes and arcing new ones.

http://www.vintagebrake.com/index.html

I would agree with rpatton
if you cooked the cush blocks you probably did the same to the double roller bearing in there.
Time to change that and order with the new cush blocks.
CNN

I follow the procedure described - pressure on brake pedal before tightening stub axle - but I still get an off center backing plate/shoes.

Never any real heat, although there is a slight brake shoe drag if the brake is adjusted tight enough to be of any use.

No rubbers, Atlas hub/backing plate.

Can't figure it out, ideas?

xbacksideslider said:

I follow the procedure described - pressure on brake pedal before tightening stub axle - but I still get an off center backing plate/shoes.

Never any real heat, although there is a slight brake shoe drag if the brake is adjusted tight enough to be of any use.

No rubbers, Atlas hub/backing plate.

Can't figure it out, ideas?

Click to expand...

Try using Ferodo shoes
deglaze the drum.
That might help
CNN

I have encountered that problem once, on the race bike, when I had pulled the axle back to adjust the rear chain and forgot to loosen the rear brake cable accordingly in a rush between two trainings. So the shoes were wearing lightly on the drum all the time and things were obviously heating up in that training. Naturally had no cush blocks with me so substituted with bits cut from a petrol pipe. Those lasted the rest of the meeting, fortunately!

I follow the procedure described - pressure on brake pedal before tightening stub axle - but I still get an off center backing plate/shoes.

Click to expand...

If the hole for the short axle in the brakeplate is not large enough then even this procedure does not work as the shoes cannot move enough to centralise, you can open out the hole in the brakeplate to allow more movement as once the nut on the short axle is torqued up the brakeplate cannot move.

Postby kommando » Wed Jun 06, 2012 3:43 am
If the hole for the short axle in the brakeplate is not large enough then even this procedure does not work as the shoes cannot move enough to centralise, you can open out the hole in the brakeplate to allow more movement as once the nut on the short axle is torqued up the brakeplate cannot move.

Click to expand...

Ohhhh my, a new one on me I'd not known to keep in mind, thanks.