Nimbus D-brake -vs- Mountain Uni UCM brake mounts

[Eric aus Chemnitz]

This is the comparison of forces on the d'break (top) and the UCM caliper (bottom)

[chainreactionphysics]

Got a large vibration when doing steep downhill today. Checked this thread out and made a heath robinson fix.

I used an old cateye light clamp and a bit of metal from an old b**e rack.

Seems to work on light braking - test in anger later.

Stewart

[lightbulbjim]

Posted elsewhere already, but... another one for the collection. Improved braking massively on my 36er.

[Eric aus Chemnitz]

Originally Posted by lightbulbjim

Posted elsewhere already, but... another one for the collection. Improved braking massively on my 36er.

Is there any connection between the tube and the brake adapter (thread in the tube?)? Or didn't you attach both parts to another because the brake force will always push the adapter onto the tube?

[lightbulbjim]

Originally Posted by Eric aus Chemnitz

Is there any connection between the tube and the brake adapter (thread in the tube?)? Or didn't you attach both parts to another because the brake force will always push the adapter onto the tube?

The bolt is extra long, and protrudes about 8mm beyond the adapter. There's a piece of 8mm diameter aluminium rod about 12mm long which is drilled and tapped and tightened onto the protruding bolt. The strut tube has an ID of 8mm so it fits tightly over the stub. The tubing is bent very slightly to line up the bolt and hole in the frame.

So to answer the question, it is quite securely aligned but is strong in compression only.

[lobbybopster]

Hello lightbulbjim, I like your torque arm ! , how would this action be effected if you drilled and pinned the 8mm x 12mm rod (internal) to the outer tube ? Would the ability to no longer expand cause any vibrations ?

Mark

[Eric aus Chemnitz]

Originally Posted by lobbybopster

Hello lightbulbjim, I like your torque arm ! , how would this action be effected if you drilled and pinned the 8mm x 12mm rod (internal) to the outer tube ? Would the ability to no longer expand cause any vibrations ?

Mark

I don't think so. Because all the others I've seen so far, including mine, have no ability to expand and all help against vibrations.
http://unicyclist.com/forums/showthr...58#post1673658
I've put a thin layer of rubber between every part (frame - d'brake, brake-adapter - hugo-strut, hugo-strut - frame) but I don't thik it was necessary. Hugo (who built the first of theese) used no rubber at all and was able to eliminate all vibration of his brake with this strut. I've also put a bit of pre-load on mine in hope that it might support the d'brake even better.

[lightbulbjim]

Originally Posted by lobbybopster

Hello lightbulbjim, I like your torque arm ! , how would this action be effected if you drilled and pinned the 8mm x 12mm rod (internal) to the outer tube ? Would the ability to no longer expand cause any vibrations ?

Mark

Maybe, but disassembly would be harder and I would have to be careful when tightening the assembly onto the bolt to ensure it ended up in the same position. Having two separate pieces makes this a bit simpler.

The vibration is pretty much under control. There's a small amount of squeal with light braking pressure but once it loads up it's silent.

I'm happy with this for now. The next improvement will be to weld a bracket to the frame, but I have a bunch of house projects which I need to finish before I can play .

[chainreactionphysics]

Originally Posted by chainreactionphysics

Attachment 69780

Got a large vibration when doing steep downhill today. Checked this thread out and made a heath robinson fix.

I used an old cateye light clamp and a bit of metal from an old b**e rack.

Seems to work on light braking - test in anger later.

Stewart

Just tested down steep hills - no vibration.

It seems that more people should be suffering with this problem??

[mowcius]

Originally Posted by chainreactionphysics

It seems that more people should be suffering with this problem??

Pretty sure a lot of people are suffering but don't realise what the issue is or that there's a solution.

I've recently hacked together a quick and dirty one for my old KH29er with stuff I had lying around as the vibration made using it as a freewheel basically impossible, and I know at least two people with oracle 36ers facing the same issue.

The steel has since cracked at the brake end as really I need to join it to the d'brake mount (to avoid stresses on a bend) as Hugo initially did, but this quick fix worked for three rides to test the concept.

[mowcius]

Strut attempt #2

0.5mm wall mild steel tubing

25g

[saskatchewanian]

My solution to the vibrating brake was to switch from sintered metal pads to rosin organic pads. Not perfect but I would consider it a 80% fix, and it particularly helped on the slightly softer Mountain Uni disks. I haven't tried a brace but imagine it would be a much better especially if if set up like mowcius sandwiched between mount and adaptor.

One thing I recently found out is that you can't use a 160mm disk with the Nimbus d'Brake mount, but it works just fine with a UCM brake mount (at least with a 160R/180F adaptor). This is slightly ironic as the UCM was specifically designed designed to be paired with their 180mm disk.

[mowcius]

One thing I recently found out is that you can't use a 160mm disk with the Nimbus d'Brake mount

You can't? I thought you just needed to use a 160mm front adaptor?

[lightbulbjim]

I used a 160mm rotor with a dBrake for a long time, it works fine.

BTW, here is my final strut design as of a few months ago

[mowcius]

Originally Posted by lightbulbjim

BTW, here is my final strut design as of a few months ago

That's a nice strut you've got there...

Wait a minute
https://youtu.be/EVekNsgUqn4?t=09