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post #11 of 16 (permalink) Old 11-29-2012, 06:50 PM
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Originally Posted by JohnA View Post
If you drop a ball down the hole then screw the stud in, doesn't the stud end up higher than before, by the diameter of the ball?
No.The tapped holes are quite deep,and the thread length is longer on the turned down end of the stud.The 1/4" ball sets the stud to correct height.
The studs were designed to be used turned end down,but Triumph continued to tap the holes deeply as they did when previously using bolts (it was OK with bolts,but not studs).
Their fix was to fit the studs turned end up,but it's bad engineering.

If the stud comes loose when you undo the nut,just screw the stud back in before you fit the nut again.At least it's not causing distortion problems.
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post #12 of 16 (permalink) Old 11-30-2012, 05:46 AM Thread Starter
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Studs v Bolts

Quote:
Originally Posted by Mr.Pete View Post
No.The tapped holes are quite deep,and the thread length is longer on the turned down end of the stud.The 1/4" ball sets the stud to correct height.
The studs were designed to be used turned end down,but Triumph continued to tap the holes deeply as they did when previously using bolts (it was OK with bolts,but not studs).
Their fix was to fit the studs turned end up,but it's bad engineering.

If the stud comes loose when you undo the nut,just screw the stud back in before you fit the nut again.At least it's not causing distortion problems.
Now understand the difference between bolts & studs. Doing as above. Thanks again Pete.
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post #13 of 16 (permalink) Old 11-30-2012, 11:58 AM
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Great information
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post #14 of 16 (permalink) Old 11-30-2012, 07:09 PM
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Quote:
Originally Posted by Mr.Pete View Post
No.The tapped holes are quite deep,and the thread length is longer on the turned down end of the stud.The 1/4" ball sets the stud to correct height.
The studs were designed to be used turned end down,but Triumph continued to tap the holes deeply as they did when previously using bolts (it was OK with bolts,but not studs).
Their fix was to fit the studs turned end up,but it's bad engineering.

If the stud comes loose when you undo the nut,just screw the stud back in before you fit the nut again.At least it's not causing distortion problems.
Please forgive my slowness Pete, I think I'm beginning to understand but would like to just check with you: Are you saying that the way Triumph did things, the studs could screw right down into the barrel threads as far as the point where the stud threading ran out, therefore making it possible to tighten the studs too much and thereby distorting the iron between the barrels?

If that is what you're saying, I understand (obviously, if this isn't what you're saying I am hopelessly lost!). I'd really like to know because I have a spare set of virtually unused barrels & pistons that I could swap any time, and if I do I want to get it as right as possible...
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post #15 of 16 (permalink) Old 11-30-2012, 08:04 PM
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I think you've got the idea.Where the thread runs out and the shank is close against the surface,you get a powerful wedging action on the top threads of the tapped hole.Most of the load is concentrated at the top threads of the hole.

If the barrel face was flat and bores were round before the stud was fitted and tightened,they won't be so flat and round afterward.Metal gets forced upward around the hole (sometimes permanently),and you get elastic distortion of the cylinders from the wedging action.When you release and remove the stud,the cylinders are round again.You can easily file off any permanently raised metal around the stud holes.

Ideally when you bore a cylinder,you would at least hone it to finished size with headbolts/studs properly fitted and tensioned as tight as they get when the engine is hot.This can be done using a torque plate to replace the head during boring/honing.The cylinders will be more round when the engine is running.They won't be so round when the bolts/studs are loosened.
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post #16 of 16 (permalink) Old 11-30-2012, 08:49 PM
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Excellent! Now I see! Thanks Pete.

PS: Here's my afterthought: What you say makes perfect sense, but why on Earth didn't Triumph do as you suggest - it was somebody there's idea after all? It looks like they had everything ready to do things the right way, then for some inexplicable reason chose not to bother. Any ideas?

Last edited by JohnA; 11-30-2012 at 08:55 PM.
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