Adding titanium pickup pins to extralite chainrings

Discuss light weight issues concerning road bikes & parts.
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alcatraz
Posts: 1948
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

Hi ww...

I hate to disappoint you by saying this will likely not be attempted but I'm just toying with the idea to upgrade these chainrings with titanium pickup pins for better upshifts.

The idea is to drill a hole in each ramp and tap them with m2 or m3 threads, sink the holes to be able to screw in a sunk titanium bolt to sit flush with the rest of the ramp.

What do you think? Probably there isn't enough material to tap sufficient threads into.
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Marin
Posts: 3409
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

I'd use steel pins. Press fit should be enough, but I don't see a problem cutting threads - I did this for a chain catcher pin on the outside, no issues.

by Weenie


Caadnme
Posts: 6
Joined: Sat Feb 06, 2016 3:03 pm

by Caadnme

This is a project for a machine shop which you can thrust the hability and carefull work.
The tip of your “pins” must be positionned accurately from the gear teeth inner face. Far enough to properly pick up the chain when upshifting but not so far that it will cause chain suck.
I am not sure if you could control the position of your pin tips accurately enough with press fin pins. Pick-up pins usually look like steel rivets.
The countersinking cutting tool has to be carefully adjusted to give a consistent depth to result in a very precise pin tip position. It is difficult to precisely machine carbon matrix parts. An almost new carbide cutting tool gives best results.
Stock screws don’t have tight tolerance for their lenght. Your option may be to grind the tips after installation. Use cooling lubricant, heat may affect the strenght of the chainring resin while grinding.
And their is also the strength of the drilled chainring to consider. A hole in any metal part weakens the part. Stress tend to concentrate around the holes in a part submitted to stress. It is worse in all fiber matrix parts because on top of this phenomenon, you add the fact that the fibers have been cut. These will no longer be continuous within the part.
But it still is a nice project and I would like to see someone try it. 😃

Marin
Posts: 3409
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Caadnme wrote:
Wed Apr 03, 2019 9:56 am
countersinking cutting tool has to be carefully adjusted to give a consistent
You are overthinking this. He needs to add pins in a similar location and similar size as on regular chainrings. Not a problem with a drill and a file.

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