Converting rear brake to hydraulic activation...

I think someone did something like this but the thread was never 'finished'. I'm going a slightly different direction and input is appreciated. So here's the prelim idea...
Use a MC something like this..



to activate a cylinder like this...

<-- .75 stroke


Pushrod off brake pedal activates MC, mini-cylinder mounted on swingarm drives brake armature. Lots of work in that 'simple' system, aside from the nit picky details of mini-cylinder has to be on some sort of semi-pivotal mount to track with the radial movement of the brake armature, and developing a solid/smooth/consistent pushrod system for the MC to brake pedal (and a spring return for said pedal..) Anyone see any inherent engineering flaws in my idea??

 

You would need to machine a bearing surface on the inner frame of the brake shoes for the cylinder to push against, same way they work in the rear brakes of your truck.
Honestly if I was going to go to this much trouble, I would just fabricate a rear disc setup.

 

I was thinking of having the cylinder drive the stock armature via a short connecting rod... here's a quick photchopped version of my idea..

 

Ah, I see now. You need to beef up that brake linkage room then. Currently it is pulling the brake arm on the rear wheel, you are asking the hydraulic system to push that rod which is going to cause it to flex, effectively lessening the braking force applied by the shoes.

 

Why not mount the master cylinder up on the forward control bracket with a braided line back to the hydraulic actuator/cylinder mounted in front of the pivot armature? This way, the cylinder piston would be pushing backward on the armature, which would then still be pulling the brake linkage rod. You would have to have a fixed point for the piston on the opposite end of the hydraulic cylinder or else it will just pop itself out.

 

You're absolutely right.....I momentarily forgot that was a pull-me, not a push-u
Revision back to what was my original (more meticulously, well thought out ) plan...




This would be more like an HD setup with the MC right at the pedal...

 

Scooterists have been doing that very modification for decades. A quick search with your favorite search engine will give you lots to read up on. You are on the right track, you just need to do your maths to figure the sizing of the cylinders to give you good feel and good braking while preventing too early of a lock up.

 

you were typing as I was photochopping Bigshank!!

 

Interesting........

 

Oh. There are pull slave cylinders out there. Magura uses one for their cable to hydraulic clutch conversion kit. I think your using a push cylinder will work fine, but using a pull cylinder will remove some potential slop from the system.

 

I was looking at those as well Moe.... I just don't get a warm-fuzzy when I consider the force needed to activate the brake sufficient to stop/lock up the rear wheel. I come from the old school of thinking, if one pound of nails is good... two pounds are better I typically over-engineer things to compensate for the fudge factor. When it comes to braking, I'd rather design/build a system that has almost a 100% safety factor in terms of foot-pounds of push or pull to get the job done, if that makes sense..Those units for clutches just don't seem like they could tolerate being used for a rear drum brake... JMO, I could be totally wrong...

 

That's exactly what I was thinking Mad Bo.

 

I wasn't suggesting to use the Magura kit (though they have been used on scooters for years). I was suggesing sourcing a properly sized pull cylinder.

 

The cylinder is a threaded mini from Vektec. I have the cylinder, just gotta get an MC and braided steel line and get to fabricating