How Much To Machine A Small Aluminium Piece?

[jyl]

I have a bicycle frame with a broken derailleur hanger. See pic.



The hanger is a small piece (appx 1" between the holes), made of aluminum, designed to be sacrificial. D If the rear derailleur gets caught in the spokes, the hanger is supposed to break off before the frame dropout breaks, the derailleur breaks, or the wheel is collapsed and the rider crashes. Some hangers are cast, others are machined. Some are 6061 T6 aluminum, others are a softer alloy.

This particular hanger, for a Vitus 997, is NLA. Can't get it anywhere in the US. Probably could find it in a dusty box in some French bike shop, but not online. Doesnt show up on eBay. I've even been searching Google.fr using the French term. Jeez, you'd think the French would have some attachment to their vintage Vitus bikes.

I could buy a hanger that is "close" and use file and drill to hack a fit. Or I could get a piece of aluminum bar stock and hand make a "close enough" piece.

Or . . . I could take this piece to a machine shop and have them make me 10 or so replicas. I'd keep a couple and sell the rest.

Question is, how much (ballpark) might it cost to have that done? I don't have a CAD file or CAD software. I could model it in Google Sketchup and export that to a CAD file, I guess.

The dimensions of the holes and the end of the hanger with the holes are somewhat critical, as it needs to fit on the bike's dropout. The dimensions of the other end are, frankly, not critical. The derailleur has enough adjustment. The finish is irrelevant, machining marks are fine. The material can be pretty soft aluminium alloy.

Any advice or thoughts? I know there are some machinist-savvy folks here.

[rcooled]

In the SF Bay Area, a quantity of 10 parts made from 6061-T6 aluminum would run about $75-$90/ea. and would include anodizing the pieces after machining. That price would assume that you supply an accurate drawing or CAD model of the part. If the shop has to measure it up first, the price will be higher.

['73-914guy]

If you can get me accurate dimensions, I can model it up in Solidworks no problem. then you can have some drawings at least to send to someone..

[herr_oberst]

John, you might have already seen this, but try this site, they have a boatload of hangers;
Wheels Manufacturing - All Hangers

If they don't have the Vitus part, maybe they can steer you in the right direction.

I was thinking, too, you could get a similar part and then have it machined to fit your bike.

(Also, you might open up a new thread here at Pelican with a more accurate title, something like "I need a Vitus derailleur hanger". There are a lot of smart cyclists here.)

Good luck.

PS, I'm enjoying the book, but the British slang is sometimes difficult to wade through, so it may be a while before you get it back!

[Zeke]

Well, if you custom machine a new part it won't do its job anymore. No way could you design in the fail point.

[cgarr]

Glue it for a pattern then get some sand and cast a new one...

[Zeke]

Originally Posted by cgarr

Glue it for a pattern then get some sand and cast a new one...

How easily is that done? I bet it was pressure cast.

[dad911]

RFQWork.com- Online Quotes from Machine Shops, Fabricators, Molders, Stampers, Casters Forgers and more!

Online Quotes from Machine Shops, Fabricators, Molders, Stampers, Casters Forgers and more!

[teenerted1]

DerailleurHanger

[jyl]

Let me check an assumption.

Assuming that: The exact location of the hole and surface on which the derailleur mounts is not critical. It can be a little bit forward or backward, a little bit inward or outward, and most derailleurs have sufficient adjustment and pivoting action to compensate. The up or down position is more critical, but still a 1/4" variance would usually be fine, since simply swapping cassettes would change the sprocket-to-derailleur clearance by more than that.

Is that correct?

[dad911]

Rather than make a new one, can it be welded at the break?

[Flieger]

Originally Posted by Zeke

Well, if you custom machine a new part it won't do its job anymore. No way could you design in the fail point.

That is easy. Just put a knotch in where you want it to fail.

[masraum]

JB Weld, Baby!! Yeah!

['73-914guy]

Was the tab even originally designed with a defined failure point? Or was it simply made out of a soft enough material that allowed it to break wherever it chose too when it gets caught in the wheel. I say either try to TIG it back together, or machine the part out of aluminum.

[jyl]

It is fairly soft aluminium. There is no pre-defined break point that I can see, admittedly it is already broken. The stays are carbon fiber so I definitely want the hanger to be the weak point. I prefer to get a new piece, vs having this one welded, since then I could have a spare, and other Vitus 992 frames could be back on the road. I will measure it up this week.

[jyl]

I did consider building this frame with a eight speed internal hub gear. Shimano's Alfine is reasonably priced. but they are still heavier, the gear range is not as good, the steps between gears are larger, and the hub is big and ugly. I have decided I want a traditional derailleur drivetrain.

[David]

Draw the piece in CAD 20 min
Water cut the shape 10 min
Drill and tap the holes 30 min
Machine down the thin section 30 min
Material $1

$100/hr so $151

CAD would only have to be done once no matter how many pieces
Water cuting 10 pieces would still be about 10 minutes
Drilling, tapping, and machining would be less per part for more parts since set up time takes the longest

[speedracing944]

I used these guys for laser cutting stainless steel gauges for our company. Laser is highly accurate and they would be able to cut the holes for you too.

Spartan Laser Inc
4413 Triangle Street, McFarland, WI 53558-9814
(608) 838-6638

I was able to get 7" X 2" X 1/4" stainless laser cut for ~$15. Just supply them a .DXF file.

Speedy

[LWJ]

John,
I used to work for an aluminum mill in town that made thousands of bike frames. That part is very easy. We did 6061 t6 all day long - by the truck full.

If it was me, I would have someone TIG weld it. Take a grinder / file to it afterward to make it pretty.

The second option is buy a small hunk of aluminum and make your own. Hack saw, file, two drill bits and you can remove metal to make this work.

This part is easy. I think someone like Milt / Zeke would do this in an hour or less. You and me? More like 2.5 hours.

Good luck.
Larry

['73-914guy]

This is a super rough model.. just from the pictures. this is about 20-30 minutes on solidworks just due to the slightly odd curvatures.