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  #1  
Old 02-26-2016, 04:28 PM
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Mucci Mucci is offline
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Question Tricks to finding Top Dead Center of frame tubing?

I need to weld a bung to the left and right side of a motorcycle frame backbone to mount the subframe. If I can find TDC of the frame tube I can measure from there to find the left and right center lines.

Does anyone have any tricks on how to find TDC or the left and right centerline?

Here's the frame in question. The mounting location is above the carb in the straight section.



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Old 02-26-2016, 05:10 PM
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joanne joanne is offline
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Google "center finder". You'll get lots of hits but this one looked like the right solution. A bit pricey but you might be able to whip one up yourself. Just make certain the frame is perfectly vertical.



Joanne
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Old 02-26-2016, 07:18 PM
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JaysinSpaceman JaysinSpaceman is offline
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Nice find Joanne. It looks like that would do the trick of finding TDC as long as the frame has been leveled. I might just have to purchase one of those.

Thanx,
Jaysin

P.S. Nice original Air Head in the background.
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Old 02-26-2016, 11:01 PM
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ScooteK ScooteK is offline
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POB, dial level.
Piece of angle iron and a digital level.
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  #5  
Old 02-27-2016, 01:09 AM
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deaner deaner is offline
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Muffler clamp and a level.Mark the center of the clamp before mounting it level.
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Old 02-27-2016, 10:37 AM
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bullnerd bullnerd is offline
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Ive doe something similar with paper.
Caliper the tube so you know the actual diameter.
Calculate the circumference.
Layout three marks on a strip of paper and wrap around the tube.
You still have to have a reference for one of the marks, but the two on the sides will be directly in line with each other.
If you can find the top center, you'd be good and don't need any special tools.

V-block and a level?
Combo square?
Eyeball!
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Old 02-27-2016, 01:34 PM
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cbrogers cbrogers is offline
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Level the frame across the bottom so that the top tube is vertical.

Rub some pencil led across the top of the frame where you want a mark.

Take a 2 or 4' level and set it across the top of the tube and angle so only a leading edge is in contact and draw back along the length of the tube leaving a mark on the top of the tube.

Us a sharpie to highlight the area of the tube where the graphite is missing and now you have the highest point on the tube.


You could also just level the frame and then use a level to sit on top of the tube and mark a single point by hand.


Carl
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