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How do frame builders add chainring clearance to the R/H chainstay ?

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How do frame builders add chainring clearance to the R/H chainstay ?

Old 01-29-11, 03:42 PM
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Unknown Cyclist
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How do frame builders add chainring clearance to the R/H chainstay ?

I've got an oldish frame that was originally 14 spd (2 x 7) and I want to add a triple chainset.

I've fitted a narrow BB and a chainset - the cranks clear the chainstays by an equal distance and although I'd like a lower Q factor it's probably ok.

The problem is the R/H chainstay isn't recessed for inner chainring clearance.

I just wondered how frame builders add this and whether it's possible to add now ?

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Old 01-29-11, 04:03 PM
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The process by which framebuilders add those dents is called dimpling. I have seen it done on frames that have already been built, but unless you have the tools and are willing to possibly be risking the integrity of your frame, I would suggest that you take it to skilled framebuilder.

However, If you think you can do it yourself, you will need a bench vise, a wood block carved to match the contours of the inside of the chainstay, and a short steel rod or bar approximately the desired length of the finished dimple. The procedure for dimpling would be as follows: clamp the chainstay between the wooden block and the steel dimpler and slowly tighten the vise being very attentive to any averse damage beyond the desired dimple. Good Luck!

Cheers
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Old 01-29-11, 05:24 PM
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It'll ruin the paint doing it at this point. But as long as you don't mind sanding down the separated chip edge and touching it up you should be able to do the dimples with the trick above.
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Old 01-29-11, 05:30 PM
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The other, and less difficult, way to get chainring clearance is to use a longer bb spindle. Your Q factor suffers but your frame doesn't.
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Old 01-29-11, 08:23 PM
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Originally Posted by lverhagen View Post
The process by which framebuilders add those dents is called dimpling. I have seen it done on frames that have already been built, but unless you have the tools and are willing to possibly be risking the integrity of your frame, I would suggest that you take it to skilled framebuilder.

However, If you think you can do it yourself, you will need a bench vise, a wood block carved to match the contours of the inside of the chainstay, and a short steel rod or bar approximately the desired length of the finished dimple. The procedure for dimpling would be as follows: clamp the chainstay between the wooden block and the steel dimpler and slowly tighten the vise being very attentive to any averse damage beyond the desired dimple. Good Luck!

Cheers
That's overthinked. Just get a ball peen hammer and one whack.
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Old 01-30-11, 10:34 AM
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At Trek we used an Arbor press with shaped blocks on the chain stays before they were brazed into the frame. Other builders use a similar method in a bench vise. Some companies (e.g. Columbus) would send the chainstays pre-dimpled from the factory.
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Old 01-30-11, 12:53 PM
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That's overthinked. Just get a ball peen hammer and one whack.
maybe 2 hammers, so hold the ball peen over the right spot. then with #2, hit it.
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Old 02-05-11, 03:36 PM
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Originally Posted by lverhagen View Post
However, If you think you can do it yourself, you will need a bench vise, a wood block carved to match the contours of the inside of the chainstay, and a short steel rod or bar approximately the desired length of the finished dimple. The procedure for dimpling would be as follows: clamp the chainstay between the wooden block and the steel dimpler and slowly tighten the vise being very attentive to any averse damage beyond the desired dimple. Good Luck!
I've been trying to do this.

I can't find a vice with jaws that will fit between the chainstays and allow any room for a wood block.....

It's quite a close clearance frame, the idea is fine in principle or if the chainstay wasn't already part of a frame......
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Old 02-05-11, 03:44 PM
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c clamp
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Old 02-06-11, 12:12 PM
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As always, thanks to everyone for their suggestions.

In the end I made support from 4x4 and supported the stay from underneath and both sides (to stop it spreading).

I taped a piece of bar (about 10mm) in the right place and adjusted the stay with a large hammer.

It has to be said the results aren't too bad......

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Old 02-06-11, 03:36 PM
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do you have pictures? i'd love to see them (i bet some others would too )
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Old 02-11-11, 06:52 AM
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Originally Posted by jchabalk View Post
do you have pictures? i'd love to see them (i bet some others would too )
I guess before and after photos of the chainring clearance would be best, but I didn't take a before photo.

Here's the chainstay, it's not amazingly impressive, but there's a few mm clearance now....
Attached Images
File Type: jpg
Chainstay.jpg (42.9 KB, 65 views)
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