oneclick 

Found this mech with a broken spring cover (they all do that sir):



The problem is they aren't just spring covers, they are also the stop for the upper end of the spring - this one has stopped stopping:



This is the stop pattern. I made this mostly with a hacksaw and files from a scrap of aluminium. You probably could make one from 3/16 thick but thicker is ok, up to 5/16" should work.

The big hole is 7/16", the small one is 5/64".

I started with a bigger piece, drilled the big hole and made the shoulder, then scribed an outline from the edges of the broken one. and put a mark through the spring-hole in the plastic, to put my centre-punch on for the small hole. It does not have to be terribly accurate, it's for a spring after all and that will happily bend a bit.

Then I cut the outline with a hacksaw, and finished it with files. It's important to allow clearance for the arm-pivots, and when installed it should sit flush with the knuckle rim, so filing to thickness might be necessary.

I made a fancy one, but I think a plain flat one with no step should work fine. You could also just make an L step. The thickness of the whole thing is 7.3mm and just the thinner part, 5.1mm.




It goes here - you must get the outside small enough so it does not stick against the inner walls of the knuckle, if it does not want to go don't force it, file it. It's quite difficult to get it out if it sticks.




And the spring goes like this:




The cover I made from a bit of stainless, it was originally the post for a stick-in-the-ground solar garden light. You could use pretty much anything, as long as it's more or less the right diameter, I was thinking of marker bodies before I checked those bits of stainless I'd been saving - for - something...

To cut it I found a marker that would just fit inside to reinforce it, and used a cutoff wheel in a dremel in the vice.



it goes on like this:



And there it is in situ:

Prowler 

Well done. I have quite a pile of "things too small to throw away". Things and materials that can become solutions to a problem, can be part of a fabrication that fixes something. A lot of junk, a saw, a good vernier caliper and a distain for authority (those who say 'that cannot be done') and away we go.

markk900

Dare I say looks *better* than original? Well done.

gthomson

Great job and in the event this ever happens to my RD I know who to call on for a repair!

oneclick 

I'm halfway thinking of offering this as a service; I have a fair bit of that stainless, and making the flat stop-bits won't be that much trouble now that I've done the first one.

The trouble would be postage costs, the cover is large enough that it would have to go as a parcel, costs more. The flat bit could go in an envelope.

gthomson

What ever the cost of the postage would be, I'm sure it's cheaper but more importantly, easier than trying source out a new RD. I don't have any tools or resources to make that myself so I would come a calling.

thook

@oneclick nice job...wow! either you really liked that derailleur or you just like being able to fix things. or both most people i think would've chucked the thing considering it not "worthy" of the effort

BFisher

An unfortunate design flaw in otherwise nice derailleurs, especially the Altus system with a Centeron pulley. Really nice shifting stuff. I don't use them anymore because they so easily fail.

Good job improving on that.

LarryBSky

I have been riding around with this. How much longer will it hold on?.
t's on my Astro Damiler Inter 10 that I'm using as my gravel bike.

oneclick 

Well, you'll know when it doesn't, because there'll be a significant change in the derailleur's behaviour. I'd suggest using shoes you can walk with.

madpogue 

I reckon most of us could come up with the cover portion, just buy some brass tubing stock at the local hardware or something. The flat part would be the more sought-after part, so you may want to consider offering the option of selling/sending the flat part only. I have one Arabesque RD and it's holding up so far, but I'll keep this in mind, for sure.

thook

it'd be really bling if you offered ano'd tubing cover. (j/k )

jamesj

I have the same problem on one of mine, would you consider making another?

oneclick 

I'm already considering it. It was time-consuming enough that I'd either have to streamline the making or charge too much; don't like plan B.