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Hydraulic cross levers

Old 10-19-17, 11:52 PM
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Hydraulic cross levers

This is a project I've been working on that maybe others might be interested in:
cross1.jpg

I've added a hydraulic brake as a cross lever that my front brifter can also pull.

I chose SRAM levers because their Matchmaker split clamp was the best for converting from 22.2 to 31.8mm bar diameter. I 3D printed a few parts to allow me to bolt on a cut up hose clamp, so the levers can be used on almost any diameter bar. This is also good for those people who have had problems with SRAM's not quite fitting on their bars, but it doesn't clamp on as tightly as the stock hardware. I'll want to upgrade some of the 3D printed parts with milled aluminum before cranking down on the hose clamps, but I'll still want something to protect the finish on the bars.

Here's the underside of the lever where I attached the cable:
cross underside.jpg

I made a quick and dirty cable bracket that I'm planning on using with a flexible brake noodle with adjuster barrel once I put on some longer brake housing, thus all the extra brake cable.

I milled a longer lever pivot that the lever and the currently round clamp arm bolt to, then I filed flat parts so the set screws don't spin around on the shaft.

I had 1" aluminum rod, but that was too small in diameter to use for the clamp arm, so I'm using it slightly offset. I should probably just use 1/2" aluminum sheet instead. The cable is clamped on with parts I cannibalized from other components in my garage.

Braking power at the drop levers isn't too great, but I still need to bed the pads. Surprisingly, even with the housing pulling a 180 degree turn, there doesn't seem to be that much cable friction. The springs in both levers is enough to snap the drop lever back.

I'm still trying to figure the best clamp arm diameter for optimum power vs. travel. The free stroke of the lever seems to be a bit much, rather, the drop lever still travels a lot before the pads start to grab. I can decrease the clamp arm diameter to bring the pads in faster, but then there goes the braking power.

I may be able to shape the clamp arm like a cam or something to bring the pads in quickly then ramp up the power, but that requires a bit more precision than I'm capable of at the moment, and I don't really like the feel of variable ratio levers (ServoWave or SwingLink). Really, I just want to get this mostly working before optimizing it.

It's still a work in progress, I want to use a thicker piece of steel for the cable bracket, and all the torque from the clamp arm is going through the pivot to a plastic SwingLink (that's what SRAM calls it in their manual, it's more just a pivoting link), so I want to add an arm that actually pushes on the lever instead. And obviously, I'll need to shorten the hydraulic line, but there's no good straight path with the lever so far inboard. A banjo fitting on the lever would help. A U-shaped fitting would be even better, if they exist.

So, there's a lot of work to be done, but it's working well enough to ride as it is, which I'll need to do if only to bed the pads and see how the braking is afterwards.

I'm not too sure if I'll do the same for the rear. It depends on how confident I feel about this kludge not breaking.
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Old 10-20-17, 01:00 PM
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Just a couple years ago there were many cable to hydraulic converters , from several companies

the twin master cylinders sat under the stem,, cable up to there, hose from there..




Magura Used to make their HS77 road rim brake , hard to find those levers now.

But they use a closed hydraulic system, So bleed is just the fitting on the end of the whole thing..

The HS 33 uses 4 identical slave cylinders, mounted in pairs , one has a supply fitting and a connecting hose to it's opposite,

same can happen on the lever end, bleed fitting becomes a supply hose, & bleed would be in the roadlever master at the end..


But the German Company has shown no intrest in making any more , but they did begin selling a new Road brake caliper
but targets the aero bar dwelling Triathlon racers..

TRP has Non Brifter Drop bar hydro disc brake. Gevenalle has a version of that for adding their cable shifters ..

with the open expansion tank common to disc brakes the daisy chain thing does not work so well ..





....

Last edited by fietsbob; 10-20-17 at 01:07 PM.
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Old 10-20-17, 06:31 PM
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I just found out about the TRP version and there are a few available on eBay for less than I paid for the SRAM brakes. And they certainly would have been much less of a time sink. Oh well, don't tell my boss how much time I spent at the machine shop at work working on this.
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