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View Full Version : Aluminium alloy for brake disk / freewheel carrier?



marcusj
02-03-2010, 12:19 PM
Hi

I am thinking about using aluminium alloy (I think it's a 6061 or very similar) for machining these from a 65mm diameter billet. Gut feeling tells me that it's going to be plenty strong enough. Any dissent?

Marcus

Odd Man Out
02-04-2010, 02:32 AM
Hi

I am thinking about using aluminium alloy (I think it's a 6061 or very similar) for machining these from a 65mm diameter billet. Gut feeling tells me that it's going to be plenty strong enough. Any dissent?

Marcus

Of course strength depends on the design. I use AL for the disc brake rotor attachment point. Have not had problems. Not sure I would use AL to attach a freewheel -- seems like it would cause too much stress for AL to handle. You might try the 7000 series AL (7050 -7025 - 7005) they have the highest strength rating for all AL types -- the downside is that you really can not weld them.

vrooom3440
02-22-2010, 08:13 PM
I have to ask OMO... considering that many bicycle hubs are aluminum and the freewheels mount up and function there just fine... why would aluminum be too weak for an adapter?

Odd Man Out
02-22-2010, 09:04 PM
I have to ask OMO... considering that many bicycle hubs are aluminum and the freewheels mount up and function there just fine... why would aluminum be too weak for an adapter?

True but the freewheels attach to the steel part that is attached to the end of and through the aluminum hub...

check out http://forum.atomiczombie.com/showthread.php?t=1275 specifically the pict on post #28

vrooom3440
02-23-2010, 12:54 PM
Interesting post and method, I likey. Now I have yet another thing to consider and figure out.

But that post is talking about cassette setups rather than the (I think?) more typical freewheel setup. The freewheels I have seen all thread directly onto a fairly thin aluminum extension of the hub. Not as much cantilever affect as your adapter either.

Odd Man Out
02-23-2010, 01:15 PM
Interesting post and method, I likey. Now I have yet another thing to consider and figure out.

But that post is talking about cassette setups rather than the (I think?) more typical freewheel setup. The freewheels I have seen all thread directly onto a fairly thin aluminum extension of the hub. Not as much cantilever affect as your adapter either.

Try it -- that's what experimentation is all about...

I don't deal much with freewheels but I bet if you take a magnet to the part you think is AL that it will probably stick. Check out figure 10 in Brad's "Bicycle Free Wheel Basics" Tutorial on this site = steel. http://www.atomiczombie.com/ct-freewheel.html

BTW it was not my adapter (wish it was I'd be a millionnaire) it is the industry standard for cassettes. Cassettes are standard for all bikes nowadays -- freewheels are so 20th century.

marcusj
02-24-2010, 04:01 AM
But that post is talking about cassette setups rather than the (I think?) more typical freewheel setup.

Sorry for any confusion - I'm talking about the threaded all-in-one with sprockets and freewheel thingy, not the newfangled device with end-user rebuildable sprocket set cassettes.

Anyway, as per another thread, I am going with steel for the thread for the freewheel. There is an option (which I won't pursue for this project) which is a hybrid of steel and Al alloy for those with a mini lathe of small motor (mine's got a 350W / .5HP motor).

Take 35mm steel bar stock and cut a ~ 40mm long piece off. Face both ends. Drill / bore out 20mm all the way through. Turn about 25mm of the O/D down to 33mm so that you have a nice undercut for threading (you could have used a part off tool - good luck with that on a mini-lathe with mild steel!). Flip the part in the chuck, turn the OD down to what you can measure off of a male thread that you get off another part, then thread at 24TPI (I used a 60 degree point tool).

You could now make an Al alloy brake disk carrier on the lathe / drill press / mill and then drill through both brake disk carrier and threaded steel spigot in a couple of places and join with (good) screws. Take care to use decent machine screws and ideally have the shear face going through a screw shoulder, not through the threaded portion of a screw.

Would be very sweet...

But I shall be welding two steel versions of these parts together for my current project.