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PostPosted: Wed May 25, 2011 9:25 pm 
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Location: Bay Area
I had one of the springs snap off of my MRC brakes. I plan on using these on my RekTek build (see link below), so I had to fix them. I've been working like a dog lately and decided to take some time off or regular duties and hit the machine shop. :)

The original springs were made of 0.10" titanium rod. I couldn't find that diameter, but I found some slightly beefier 0.125" stock.

These are the pics of the repair.

I drilled the new holes with a #31 bit 0.1200" so that I could get a good press fit.

I then put the titanium rods in some liquid nitrogen to cool and shrink them, and I heated the aluminum block up with a heat gun. I then lined everything up and gave a few good hits with the ballpeen hammer.

I'm pretty ....chuffed (is that what you say in the UK?) with the results.


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originally I was just going to drill out the remaining piece of the titanium that was stuck. You can see that I started to do that. Then I remembered that the replacement was slightly larger in diameter and might be too close to the outer edge. I decided to drill the other side and offset the hole slightly to accommodate the larger dia. rod.

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here you see the old spring on the right. I was able to pull it out of by hand. I had one broken spring and one intact. I didn't think the brakes would feel correct if I had different springs on the left and right so I pulled the spring out.

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Last edited by classen on Thu May 26, 2011 11:08 pm, edited 1 time in total.

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PostPosted: Thu May 26, 2011 12:33 pm 
Gold Trader / MacRetro rider
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Joined: Sun Apr 02, 2006 1:03 pm
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top job mate

its good fun fixing/making stuff 8)


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PostPosted: Thu May 26, 2011 1:00 pm 
retrobike rider / Gold Trader
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Top work indeed, 8)

And it's given me a bit of hope should mine ever fail.. :shock:


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PostPosted: Thu May 26, 2011 10:56 pm 
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blimey - good skills !

i'm sure i'm missing a nut from mine.
i don't suppose you could show a picture of the brakes with their component parts could you?

plus i didn't know the rod was ti. ta for that!


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PostPosted: Thu May 26, 2011 11:31 pm 
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Here's my bits.

The only thing I might want to add is a washer that would sit between the brakes and the brake boss on the frame. I think it would go some way to keeping dirt/dust away from the brass bushings.
Image

whoa!!! gotta clean those brake pad holders :shock:


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PostPosted: Tue May 31, 2011 1:48 pm 
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Location: Near Ilkley
ah, that's brilliant thank you.

i think i'm missing the washer you mention - i thought it was a tensioned nut though.
and i don't have a brace either - i guess they're not essential.

i'll break mine down later and take a picture to compare.


thanks!


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