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Old 2019-11-08, 09:14 PM   #1
MuniAddict
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D-brake reinforcement support

Made this using aluminum flat bar 1/8 inch thick 1/2 in wide. Twisted the upper end so it could be attached to lower brake boss. Lower end attached to the outside D-brake bracket.

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Old 2019-11-08, 11:21 PM   #2
OneTrackMind
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I would have thought it would bend under load over such a great length.
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Old 2019-11-09, 12:20 AM   #3
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Quote:
Originally Posted by OneTrackMind View Post
I would have thought it would bend under load over such a great length.
It's simply an auxiliary support to help buttress the D-brake. It would not bend since there is no evident movement of the D-brake during braking. The braking forces originally stressing the bottom arm are now partly shared by the added strut. The added reinforcement makes it less likely that the D-brake arm will fail. If this were to happen, then and only then, would the strut be likely to bend under the stress of the breakage.
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Old 2019-11-09, 01:48 AM   #4
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Quote:
Originally Posted by MuniAddict View Post
It's simply an auxiliary support to help buttress the D-brake. It would not bend since there is no evident movement of the D-brake during braking. The braking forces originally stressing the bottom arm are now partly shared by the added strut. The added reinforcement makes it less likely that the D-brake arm will fail. If this were to happen, then and only then, would the strut be likely to bend under the stress of the breakage.
Sure, but in order to perform as a strut, a member must resist bending. It will make some contribution to strength but not much.
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Old 2019-11-09, 02:15 AM   #5
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Quote:
Originally Posted by OneTrackMind View Post
Sure, but in order to perform as a strut, a member must resist bending. It will make some contribution to strength but not much.
The main problem with dBrakes isn't so much bending (although that does happen) but chatter and vibration. The strut should help with that.
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Old 2019-11-09, 02:24 AM   #6
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By the way Terry, if you're worried about bending there is a newer version of the dBrake which is a bit more beefy than the one you have.

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Old 2019-11-09, 04:56 AM   #7
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Quote:
Originally Posted by lightbulbjim View Post
By the way Terry, if you're worried about bending there is a newer version of the dBrake which is a bit more beefy than the one you have.

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Very cool, thanks for letting me know!
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Old 2019-11-09, 06:15 PM   #8
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Terry, do you have problems with disk brake chatter on steep downhills? I do, and had to add a bracket to support the D-brake adapter.

I'm just curious about when other people have issues with chatter. For me, I'm riding a KH 29" with a 203-mm disk and TRP 4-piston calipers with steel pads. If I'm on a hill that is >22 degree grade, this setup chatters really bad. So far, my little bracket has fixed the problem. But, what a hassle.

It makes me think that there is room for KH or UDC to develop a better out-of-the-box production solution.
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Old 2019-11-09, 06:22 PM   #9
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By the way, I have the newer D-brake bracket. I think it looks even beefier than the "new D-brake" in the picture above. Plus, my D-brake bracket is 7075 aluminum which has a slightly higher Young's Modulus than 6061AL.

Actually, the higher modulus makes the 7075 bracket stiffer. There is a chance that this may make the chattering worse (don't remember my vibrations class that well). Are there any mechanical engineers out there that would know if chatter would be worse with a D-brake made from 7075 AL vs 6061 AL?
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Old 2019-11-09, 07:50 PM   #10
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I don't use a d-brake bracket but I wonder if this would help. On my bearing caps I add carefully selected washers/shims so that the bolts can be tightened without deforming the bearings. Maybe using shims on both bolts that hold the d-brake and bearing cap on would help. With the correct shims the bolts can be fully tightened and maybe would help reduce any vibrations or looseness in the d-brake.

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Old 2019-11-09, 08:23 PM   #11
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I was just about to order a new 7075 version D brake when I discovered that I already had one! It was buried in a drawer and covered with swirl dip from an old paint job. So I cleaned it up. Here it is next to the original 6061 version.

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And here is a more direct method for reinforcing the D brake, with no attachment to the frame required.


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Last edited by MuniAddict; 2019-11-09 at 08:41 PM.
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Old 2019-11-09, 08:59 PM   #12
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Quote:
Originally Posted by SanJoseUnicyclist View Post
I'm just curious about when other people have issues with chatter. For me, I'm riding a KH 29" with a 203-mm disk and TRP 4-piston calipers with steel pads. If I'm on a hill that is >22 degree grade, this setup chatters really bad. So far, my little bracket has fixed the problem. But, what a hassle.
There are lots of reports of chatter (and pictures of braces) in this thread.

Quote:
Originally Posted by SanJoseUnicyclist View Post
It makes me think that there is room for KH or UDC to develop a better out-of-the-box production solution.
Nimbus has switched to welded mounts in their current gen.
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Old 2019-11-09, 09:14 PM   #13
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Quote:
Originally Posted by lightbulbjim View Post
There are lots of reports of chatter (and pictures of braces) in this thread.



Nimbus has switched to welded mounts in their current gen.
I wish KH frames came with disc tabs on the left side as well for those who want to run an external system.
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Old 2019-11-09, 10:17 PM   #14
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Quote:
Originally Posted by MuniAddict View Post
I wish KH frames came with disc tabs on the left side as well for those who want to run an external system.
The Mad4One frames have double disc mounts. Not sure that they do a 36" though .
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Old 2019-11-09, 11:58 PM   #15
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Originally Posted by lightbulbjim View Post
The Mad4One frames have double disc mounts. Not sure that they do a 36" though .
yeah, unfortunately they don't make any frame larger then 29er.
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