How are band brakes supposed to be adjusted?

[swbluto]

I have band brakes on my scooter which I have dreaded from the beginning, but yet they've been working reasonably well in dry weather. It's been raining a bit recently and it seems like my band brakes have given away to completely sucking, and they've lost pretty much all power.

So, I take it inside and confirm the brake is engaging like it should. It's really weak and think it was due to wetness. So, I kept pushing the brakes over and over by pushing the scooter around and engaging the brakes and finally they started gradually becoming better and finally the wheel would start to skid instead of squeal. Before the process, I changed out a washer for a bolt so that the band would be more aligned with the brake drum/disc.

Now, today, when I try out the brakes, all they do is squeal and they are only semi-effective (About one third the force of wheel locking). It looks like the band is about as closely aligned with the brakes as far as I could get it (Even more so than when it was working before), but yet it just squeals. Anybody know how it's supposed to be set up? Thinking it may have been wet, I tried drying it by braking and using the motor at the same time just to speed up the drying process, and the brake got pretty warm, but it never became more effective, so it seems like it's something else.

Do these brakes die? How can you tell if you have a dead band brake? How much does angle alignment matter? How much does offset distance matter?

There seems to be surprisingly little information online about these little buggers.

 

[johnrobholmes]

Can you see the brake material on the band still, or is it just metal rubbing on metal now?

 

[Storm]

How far do you pull the brake lever in, does it touch the grip? can you adjust the slack from the line?

 

[Ypedal]

I hate those darn things.. had them on a trike i converted this summer for a guy.

My understanding is that band brakes are not meant to be a hard braking device, but rather just a slow you down and assist the main brakes type thing.

As john pointed out, If you still have material left on the band, taking it apart and lightly sanding the surface of the drum and the brake liner may help with the squeal ( usually caused by the surfaces glazed over and making that horrible noise ), might even be able to slide a piece of sand paper in the slot between the drum and band then spin the wheel around a bit.

 

[Storm]

There is a screw w/locknut on outer edge of the band housing, it controlls the evenness of the band contact around the drum, screw till seated then back off 2-3 turns and tighten locknut, adjust cable to remove slack. It may help to sand the drum as it may be shinny/greasy from ingression.

 

[swbluto]

Interesting, I don't see a particular lock-nut on mine. I would have to take a picture so you could point it out.

Anyways, I started vigorously sanding the drum and band with a low grit number and in a way perpendicular to the direction of rotation, and it seems to have got a little better. It still isn't "braking hard" like it used to, but at least it's slowing down now in a slightly useful way. Apparently it seems water seems to cause this problem for some reason, as it gets weak in rain as well - perhaps water transports dirt onto the drum where the belt compresses it into a smooth slippery layer. Maybe that's partially why they disallow using so-called "toy" electric scooters in the rain (Except for the fact they're electric but mine is pretty much weather-proof by design - my design. ).

 

[swbluto]

There is a screw w/locknut on outer edge of the band housing, it controlls the evenness of the band contact around the drum, screw till seated then back off 2-3 turns and tighten locknut, adjust cable to remove slack. It may help to sand the drum as it may be shinny/greasy from ingression.

OH WAIT!

Maybe that's what the screw is for that connects the band-brake to the frame. It only has a single locknut on it now and that squeezes to the frame, but who knows how many nuts it had on originally. I took it apart and had little clue on how it went back together; trust me, there was a ton of trial and error involved.

 

[liveforphysics]

Friction surfaces glaze when brakes are under-sized, and never break-in and collect oil/grease films when over-sized for an application. Hitting them with a sand paper flapper wheel in a drill or die-grinder can de-glaze them. Hitting them with some strong solvents can de-grease them.

If you experienced a rapid change in brake performance, it sounds to me like you might have worn through the friction material on the band, and now you're trying to brake with metal/metal, which often has about 1/2-1/4 of the friction co-efficient.

 

[AussieJester]

Dunno if it would help in this application but you can buy a product from Automotive stores that you put on your fan belts
that helps stop it slipping, might be worth trying if the other options fail?

KiM

 

[swbluto]

Ok, so I found out that my existing bolt wasn't long enough to ideally adjust the band brake to the wheel's tilt, so I picked up a longer bolt to replace it. After adjusting it, it still seems like it's not perfectly parallel and it won't "go in further" naturally, but it looks pretty parallel to the drum. Well, it stops pretty good now! It still has that annoying squeak, but it's nowhere as squeal prone as it used to and the braking power has substantially improved. I now have to engage the brake slowly and smoothly if I don't want to be jolted.

So, yeah, it appears everything's good now.