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Old 02-26-2016, 02:20 PM   #1
Dave T
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Default Triumph crank repair

I have a T100 Triumph crank with the keyway on the stator end is beat out and cracked. Has anyone tried a repair in this area? I have thought about welding it and remachining it or cutting the end off and making new stub that would thread into the crank. I don't know if drilling and taping the crank would weaken it too much. I don't think welding out on the end of the crank would cause a warpage problem if I don't get carried away with the heat. What kind of rod to use is another question. At this point I have nothing to loose, with out the repair the crank is junk. Any ideas and imput would be helpful. Thanks, Dave T
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Old 02-26-2016, 02:37 PM   #2
beaverbikes
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Default Re: Triumph crank repair

Don't know how bad yours is. I've made my own special key before. Clean and square up the slot in the crank using a dremel. Then you get a thicker key and file, file, file. Get it to fit your new slot, then narrow down the top to fit rotor keyway. Incredibly fussy and takes a while. I'm not the only one to have done this, I'm sure I probably read it on one of the forums first, it can work good.
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Old 02-26-2016, 02:54 PM   #3
vorhese
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Default Re: Triumph crank repair

I had Wes' machinist fix my crank keyway when he did the journals. All this thing is really doing is turning a rotor, so it's not too big of a deal.



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Last edited by vorhese; 02-26-2016 at 03:01 PM.
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Old 02-26-2016, 03:04 PM   #4
Luckypabst
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Default Re: Triumph crank repair

Just cut a new keyway 180 degrees out from original.

Edit: this will throw off your timing marks on a later engine so don't forget to re-mark the rotor.

Chris

Last edited by Luckypabst; 02-26-2016 at 03:24 PM.
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Old 02-26-2016, 04:10 PM   #5
Dave T
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Default Re: Triumph crank repair

The crank has a crack that comes out of the inboard end of the keyway and about 45 deg. around then all the way out through the threaded end. I'm afraid that if I don't cut all of the crack out the area will be to weak to support the rotor. A custom fit key is a good idea but he crack is the big problem. Same deal if I cut a new keyway, the crack, I think, weakens the stub too much. This is what makes old stuff fun.
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Old 02-26-2016, 05:36 PM   #6
bobscogin
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Default Re: Triumph crank repair

Quote:
Originally Posted by Dave T View Post
The crank has a crack that comes out of the inboard end of the keyway and about 45 deg. around then all the way out through the threaded end.
You may want to consider another crank.

Bob
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Old 02-26-2016, 07:35 PM   #7
Dave T
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Default Re: Triumph crank repair

A new crank, only as a last resort. A good idea, but I don't want to admit defeat. I'm used to making junk work. I'll let you all know how it works out.
Thanks for the imput. Dave T
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Old 02-26-2016, 10:37 PM   #8
Luckypabst
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Default Re: Triumph crank repair

In my experience, forging alloys like to crack at the weld toe using ER70S-2. I've only kept it crack free with lots of pre- and post-heat. It can be pretty frustrating... And then you'll have time in getting the OD concentric without removing any material beyond the weld, and getting the threads fixed on the ID. Are cranks that hard to find/expensive?

Chris
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Old 02-27-2016, 12:10 AM   #9
Tony the torch
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Default Re: Triumph crank repair

Quote:
Originally Posted by Luckypabst View Post
In my experience, forging alloys like to crack at the weld toe using ER70S-2. I've only kept it crack free with lots of pre- and post-heat. It can be pretty frustrating... And then you'll have time in getting the OD concentric without removing any material beyond the weld, and getting the threads fixed on the ID. Are cranks that hard to find/expensive?

Chris
Hey Chris ...
if you get bored we still have stuff that needs welding around the shop.

Tony
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