One-off/ small run complex parts (CNC?)

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One-off/ small run complex parts (CNC?)
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Posted: Nov 17, 2020 at 6:49 Quote
Hi folks, wondering if anyone knows of companies that produce aftermarket parts which are no longer available as manufacturer spares? I have a TREK RUMBLEFISH ELITE (2012), on which the rocker link (aka swing link) has cracked.

The answer should be simple, go and buy another link and bolt it in, job done.

BUT... TREK no longer make the part, and nobody worldwide appears to have any in stock, nobody appears to be breaking a similar bike for spares. Without a functioning link, the whole bike is useless. This appears to be not a unique case, there are a few posts here from people looking for the same part (also used on SUPERFLY 100, I believe), but is also not a large volume problem with a potential production run of thousands.

I have done some scouting on the interweb, and so far not found anyone who manufactures this sort of thing. I did track down one company in UK who used to machine odd parts, but they withdrew as they it was a great way to lose money...

Anyone got any good ideas?

Posted: Nov 17, 2020 at 8:46 Quote
As a person who had a one-off car part made, you can certainly get it done if you have the money to throw at it.

The problem is that they don't just look at the part and bang one out. Even the fancy laser scanning that supposedly makes everything so easy is limited in its actual capability. There are lot of man hours that go into taking that scan and converting it into something that a CNC machine can actually use.

If you could get the original part files from Trek, then you could get it done for sure...but good luck with that.

If you get some CAD software and build the part you want in there properly so that a CNC shop could just throw it in the machine and get their tool paths and cut it, it's still going to be a lot of your time and money to make the part.

I'd recommend buying a new frame...you'll probably save money.

Posted: Nov 18, 2020 at 10:47 Quote
Fabrication isn't cheap or easy. I'm sure you can find someone that will do it but it wont be cheap. A lot of hours from a skilled machinist go into something like this.

You are probably better off trying to find a used frame you can steal the link from. Any ideas if Trek maybe used this link on other models of that year?

Posted: Nov 18, 2020 at 11:46 Quote
Could you get it welded? Presuming it ali. Otherwise any CNC machining facility should be able to it, its just a case of cost. Search for local aluminium welders first then local CNC shops and start asking around.

Posted: Nov 18, 2020 at 20:47 Quote
I do aerospace cnc programming for a living and I could definitely make it judging by the pictures I could find on the internet. That said, I would charge so much to do a one off that you probably wouldn't want to do it. First off I would have to reverse engineer the part. I would have to figure out what kind of hole sizes to cut for proper bearing fits, measure all the dimensions, etc. Then I would have spend time modeling it in CAD. Next I would need to program tool paths to cut it. Then I would likely need to build a fixture to to hold it for a least one machining operation. I'd have to make programs to make that as well. And finally the easy part, actually running it and making it. By the time it was done I'd probably have at least fifty hours of labor working on it.

If it were my bike and I loved it I'd probably go through with it.

But in your case I'd recommend trying to find someone to weld it up, assuming it's a weldable alloy.

Posted: Nov 19, 2020 at 18:03 Quote
I believe it's magnesium. Find someone to TIG weld it.

Posted: Nov 20, 2020 at 8:55 Quote
Sometimes you can simplify the design, a lot of links on
modern bikes have a sort of organic alien shape to them,
they contour into all sorts of curves and are a one piece design.

The easiest to make is a 3 piece link, two flat plates and a bridge or
connecting peice that bolts them all together,
Cove Hustler, Kona Coiler as an example to my meaning.

I don't know the type of bike you have so it may not be possible, but its another
angle of thought on the issue.

Posted: Nov 22, 2020 at 6:24 Quote
Thanks all, you have confirmed my suspicions, that it's not economic for one-offs. That said, I'm a bit surprised that, somewhere in the webisphere, someone hasn't set up a cottage industry making these sort of obsolete bits & bobs (could even be with the support of the major manufacturers, as if they no longer make or keep the parts there is no commercial value in hiding the shape models so logically could share with trusted third parties...). Anyhow, TREK blurb says it's magnesium, so I'm now looking out for a suitable TIG welder who does magnesium welding...

Posted: Nov 22, 2020 at 12:31 Quote
KMJ wrote:
Thanks all, you have confirmed my suspicions, that it's not economic for one-offs. That said, I'm a bit surprised that, somewhere in the webisphere, someone hasn't set up a cottage industry making these sort of obsolete bits & bobs (could even be with the support of the major manufacturers, as if they no longer make or keep the parts there is no commercial value in hiding the shape models so logically could share with trusted third parties...). Anyhow, TREK blurb says it's magnesium, so I'm now looking out for a suitable TIG welder who does magnesium welding...

Affordable CNC on non-trivial parts means the person doing it is making well under minimum wage. There's a lot that goes into it. I learned the hard way. I have a great gauge panel for my car though!

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