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A Metalwork Problem

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This is the gear cassette from my beloved tandem. As you can see the teeth are bent on the smallest cog. We bought a replacement cassette but it doesn't fit... so I'm now trying to see if the original can be fixed. Are there any metalworkers out there who want to give me some advice... or preferably fix it for me?!! I can bring it to any of the UAL colleges and there is a beer in it for you...!!

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swood's picture

For a split second I thought, yeah having a tandem must be really awkward if you both have to ride it.

Doh!

 

Steve

lindsayjordan's picture

Ah - thanks Steve - no, it's not as good news as 'sure, I can bash that out for you, bring it over and I'll have it done by 4pm' but at least now I know how unfeasible fixing it is! We will have to book it into the bike shop and get them to fit the new cassette they sold us.

One of the challenges of having a tandem is that both of you have to then take the day off work in order to ride it to the bike shop ;)

Thanks again!

swood's picture

Hi Lindsey

You have a few of problems here;

The cog you need to repair is riveted to the others, in order to get to the cog to begin to attempt a repair, it will need to be separated which means grinding the tops off of the rivets and knocking it apart, it also means it's got to go back together again and very securely. Riveting is out of the question as the tooling to do this is very powerful and beynd the scope of most engineers workshops. It could be welded although I don't know how successfully, or bolted together with very strong hex bolts.

Cogs are very hard, they need to be in order to resist the amount of wear they are going to get, this makes it very difficult to work them; drill, file, hammer etc, on top of this they are very accurately made as they need to engage and release from the pins of the chain without fouling. The type of repair you want to achieve is going to have to be very accurate and the material will not let itself be worked in this way. It is very very difficult to move a stubborn material a short distance without applying a lot of force which in the process could damage it.

In short, you really need to get a set of cogs that fit.

Not good news I know.

Regards

Steve

 

 

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This Work, A Metalwork Problem, by lindsayjordan, is free of known copyright restrictions.