Tube angles.

[Dromen]

Is there a fast sure way to measure tube angles?

[Nooch]

http://www.mathsisfun.com/geometry/images/protractor.gif

just having some fun :)

[Grant McLean]

iPhone compass app has an angle finder.

-g

[cmg]

tape a plum bob (weight on a string) from the center of the seat tube, tube top intersection, let it hang down. take the protractor line up the 90 with the plum bob, take another string tape it the same intersection (top tube seat tube) extend string to center of bottom bracket. read the angle.......make a right angle diagram of the numbers. or buy/get/use/sign up for/pay the fee for an iphone.

[Mark McM]

http://www.travers.com/Travers%20Images/Current%20eSales%20Images/300x300/57-020-267.jpg

About $10 at your local hardware store.

[Dromen]

Thanks Mark McM

[Mark McM]

When using the angle finder, it's best to take 4 measurements:

1 - Stand the bike upright, place the angle finder on the tube to be measured (V-groove helps center it on the axis of the tube).

2 - Flip the angle finder around (so it is oriented in the opposite direction on the tube), and measure again. If these two measurements are different, it means there is an offset in the angle finder, so averaging the two measurements should cancel the offset.

3 - Flip the bike around, so the front wheel contacts the ground where the rear wheel did, and the rear wheel contacts the ground where the front did. Measure the tube angle again, with the angle finder in the orientation of the first measurement.

4 - Finally, flip the angle finder around again (to the orientation of the 2nd measurement) and take one last measurement. Average the 3rd and 4the measurements again.

If the ground isn't level, the average of the 1st & 2nd measurements will be different from the average of the 3rd and 4th measurements. But averaging all 4 measurements will cancel out both the offset in the angle finder, and the angle of the ground the bike is standing on.

[Dromen]

Seems like you have measured a tube angle before. Thanks much.

[bikingshearer]

iPhone compass app has an angle finder.

-g

I had no idea the compass app had that. Tres cool. Many thanks.

Lot's of other good advise here, too. I use a digital angle finder from Harbor Freight. Works tolerably well, and you can zero it out on an angle without having to make sure your bike is level. Don't remember how much it was, but it was more than the $10 Mark McM paid for something as useful.

[David Kirk]

When using the angle finder, it's best to take 4 measurements:

1 - Stand the bike upright, place the angle finder on the tube to be measured (V-groove helps center it on the axis of the tube).

2 - Flip the angle finder around (so it is oriented in the opposite direction on the tube), and measure again. If these two measurements are different, it means there is an offset in the angle finder, so averaging the two measurements should cancel the offset.

3 - Flip the bike around, so the front wheel contacts the ground where the rear wheel did, and the rear wheel contacts the ground where the front did. Measure the tube angle again, with the angle finder in the orientation of the first measurement.

4 - Finally, flip the angle finder around again (to the orientation of the 2nd measurement) and take one last measurement. Average the 3rd and 4the measurements again.

If the ground isn't level, the average of the 1st & 2nd measurements will be different from the average of the 3rd and 4th measurements. But averaging all 4 measurements will cancel out both the offset in the angle finder, and the angle of the ground the bike is standing on.



Exactly what I would have said. If you want real numbers the bike needs to be flipped end to end.

dave

[Keith A]

iPhone compass app has an angle finder.

-gGot a recommendation for one?

[bikingshearer]

Got a recommendation for one?

My 4s came with a compass already loaded. It's in the "Utilities" button. When you pull it up, swipe right or press the little white button below the degree reading. Like most apps and like a Swiss Army knife, not the perfect tool for the job but it's the best tool for the job that you are likely to have with you.

[Keith A]

My 4s came with a compass already loaded. It's in the "Utilities" button. When you pull it up, swipe right or press the little white button below the degree reading. Like most apps and like a Swiss Army knife, not the perfect tool for the job but it's the best tool for the job that you are likely to have with you.Thanks...as they say, I'm glad it wasn't a snake :eek:

[Craig Ryan]

Clearcoat near graphics is thicker than one might think. This makes HT measurements difficult. Most of the simple tools would have a hard time differentiating <1°. The little digital blocks are a step up, but still questionable with their small footprint. Tubes bow, are not necessarily round, and have possible distortion because of the heat cycles. It may be better to use math. It's easy to get the ST, the HT is the hard one. Reversing direction as mentioned is smart.

[Peter P.]

Here's what I use:

http://www.bealltool.com/images/product_shots/tiltBoxII.jpg

[happycampyer]

Clearcoat near graphics is thicker than one might think. This makes HT measurements difficult. Most of the simple tools would have a hard time differentiating <1°. The little digital blocks are a step up, but still questionable with their small footprint. Tubes bow, are not necessarily round, and have possible distortion because of the heat cycles. It may be better to use math. It's easy to get the ST, the HT is the hard one. Reversing direction as mentioned is smart.These are excellent points. And headtube badges make it almost impossible to get a measurement off of the headtube. I'm not sure how accurate it is, but I sometimes find it easier to measure the headtube angle of a frame off of the exposed steerer of the fork above the top headset race.

Also, I think Dromen may be trying to measure the angles of a Serotta, and the swaged tubing makes that complicated as well (as does any tube manipulation). Measuring the seat tube angle off of an exposed seatpost would likely produce a more accurate measurement than off of the seat tube itself, since the seat tube tapers several mm over its length.

[Black Dog]

Here's what I use:

http://www.bealltool.com/images/product_shots/tiltBoxII.jpg

I use one of these professionally and I can say that they are very accurate.

[Peter B]

You can use the digital block (or iPhone app) w/ a 6"" steel rule laid along HS cups to get HTA. Unless you're 6'-7" and have one of those giraffe HTs.:eek::eek:

[8aaron8]

A beveled protractor may work well too, but many of the suggestions here will get you what you need.