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Evaluating frame angles....both damaged and undamaged.

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Evaluating frame angles....both damaged and undamaged.

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Old 02-13-10, 04:59 PM
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miamijim
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Evaluating frame angles....both damaged and undamaged.

Have you ever wondered what the seat tube and head tube angles are on your vintage bike? Is the head tube angle off after that frontal impact?

Here are 2 quick, easy and cheap* ways to measure a frame.

* = cheap = ~$15 for the digital gauge from Harbor Frieght and $3 for the iphone app....assuming you already have the iphone.

Method 1 is using a digital angle gauge from Harbor Freight. Zero it on a level surface then place it on the frame tubes. The bike I'm measuring in the pics suffered a frontal impact and has rippled top and down tubes. As you can see the head tube is within reason. Because the frameset is in my workstand the actual number isnt relevant, whats relevant is the relationship between the numbers. If the head tube was more steep it would tell me its out of spec.



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Method 2 is using my iphone with an app store app. Idealy the face of the iphone should be agianst the tube as the backside has a slight curve....but you get the idea. For the iphone to be most accurate the 'Y' axis needs to be centered, as you can see I'm slightly off.


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Old 02-13-10, 05:19 PM
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That's assuming seattube and headtube are parallel, such as 73/73. 73/74 won't read right with that method.

-Kurt
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Old 02-13-10, 05:27 PM
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Originally Posted by cudak888 View Post
That's assuming seattube and headtube are parallel, such as 73/73. 73/74 won't read right with that method.

-Kurt
If I knew it was 73/74 it would!!! But it does give you an idea of where your at. If the head tube measured 78 degrees I'd know it was toast but its within a degree of the seatube....no big deal.
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Old 02-13-10, 05:30 PM
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Originally Posted by miamijim View Post
If I knew it was 73/74 it would!!! But it does give you an idea of where your at. If the head tube measured 78 degrees I'd know it was toast but its within a degree of the seatube....no big deal.
Yep - though I dare say this method is even better used on a suspected crashed frame of which the original frame angle specs are available (for instance, the Caleb Paramount track bike).

-Kurt
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Old 02-13-10, 05:33 PM
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Originally Posted by cudak888 View Post
Yep - though I dare say this method is even better used on a suspected crashed frame of which the original frame angle specs are available (for instance, the Caleb Paramount track bike).

-Kurt
Absolutely!!! The frame I'm measuring is the crashed Panasonic DX5000 from my other thread.
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Old 02-14-10, 12:21 AM
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you could always skip the leveling step and just measure the tt angle and add/subtract from the other tube's angle.
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