Miter Sheet Translation ?

[Epicus07]

Sounds a little short and long for my tastes. Damn shame. Might have to just suck it up and order a new one.


Sent from my iPhone using Tapatalk

[donevwil]

NHAero and minutes to the rescue.

[NHAero]

I thought stack was the vertical dimension between BB center and the top of the HT along its centerline?

Why isn't stack of this frame not 448.5 (BB to bottom of HT along its centerline) plus 139.8 times sine of 72.5 degree HTA, which is 133.3, for a total stack of 581.8?

[NHAero]

Originally Posted by donevwil

Mark,

Provide me with a sanity check: If the listed HT and ST angles (72.3 & 73.0) are correct and we "assume" the ST-TT angle of 78 is correct (I did as well), then the HT-TT angle shown (102.3) is incorrect. Should be 102.7.

Minimal impact on stack and reach regardless.

HTA is 72.5 degrees, at least I read it as 72 degrees plus 30 minutes of arc.

[Mark McM]

Originally Posted by spoonrobot

Well don't do that the numbers Mark McM gave you are way wrong

Measuring in high resolution with Gimp I get

ETT 559
Stack 563
Reach 388

Please explain what is wrong with my formulas, and why measuring from a print of a photo of print (which may or may not have in correct proportion to begin with) is more exact.

I should mention one simplification in the formulas - the length dimension of the top tube is actually below the top of the seat tube and the top of the head tube, but it is the same 20.0mm distance below at both ends. If the head angle and seat tube able were identical, then the top tube length would be exactly the same as the distance between the top of the seat tube and the top of the head tube. But the head tube is actually 0.5 degrees shallower, which will result in a horizontal error of less than 0.2mm and the vertical error of less than 0.1mm.

[donevwil]

Originally Posted by NHAero

HTA is 72.5 degrees, at least I read it as 72 degrees plus 30 minutes of arc.

Doh! Thank you. Where's my slide rule (last time I used minutes).

[spoonrobot]

Originally Posted by Mark McM

Please explain what is wrong with my formulas, and why measuring from a print of a photo of print (which may or may not have in correct proportion to begin with) is more exact.

I should mention one simplification in the formulas - the length dimension of the top tube is actually below the top of the seat tube and the top of the head tube, but it is the same 20.0mm distance below at both ends. If the head angle and seat tube able were identical, then the top tube length would be exactly the same as the distance between the top of the seat tube and the top of the head tube. But the head tube is actually 0.5 degrees shallower, which will result in a horizontal error of less than 0.2mm and the vertical error of less than 0.1mm.

Your first post was wrong (see quote) and your second post was edited for additional information after my post. Don't take it personally, you just made a mistake.

Originally Posted by Mark McM

I get a Reach of 359.6mm and a Stack of 509.4mm (based on the assumption of a 10mm lower headset stack). Effective top tube length 515.3mm

But someone should double check my numbers.

Perhaps you should amend your first post (Post #3) to remove the incorrect information? Then I could amend my post calling attention to the incorrect information you posted.

[spoonrobot]

Mark McM information calculated in this thread, using formulas (apparently including top headset cup estimate).

Attempt #1:
ETT 515.3
Stack 509.4
Reach 359.6

Attempt #2:
ETT 558.0
Stack 577.0
Reach 389.7

My information measured in this thread, using scale drawing and Gimp pixel measure (using actual headtube measurement).

Attempt #1:
ETT 555
Stack 565
Reach 387

Attempt #2:
ETT 559
Stack 563
Reach 388

You're really going to call ME out here?

READ THE DRAWING correctly next time.

[spoonrobot]

Mark McM please explain how you confused these two dimensions.

[NHAero]

ETT = 547.5 x (sin 5 x tan 17 + cos 5) = 560

[Mark McM]

Originally Posted by spoonrobot

Mark McM information calculated in this thread, using formulas (apparently including top headset cup estimate).

Attempt #1:
ETT 515.3
Stack 509.4
Reach 359.6

Attempt #2:
ETT 558.0
Stack 577.0
Reach 389.7

My information measured in this thread, using scale drawing and Gimp pixel measure (using actual headtube measurement).

Attempt #1:
ETT 555
Stack 565
Reach 387

Attempt #2:
ETT 559
Stack 563
Reach 388

You're really going to call ME out here?

READ THE DRAWING correctly next time.

Yes, I made (multiple) mistakes in my first calculation attempt, and then in my next post I fully called them out (to have deleted or amended the first post would have been hiding my error, but I don't try to cover up my mistakes). I also included the formula I used in the 2nd post.

But speaking of dodging, you haven't answered my questions: What is wrong with my formula? Why is measuring a drawing (which may not be to scale) more accurate than calculating directly from the numbers?

[spoonrobot]

Originally Posted by Mark McM

Yes, I made (multiple) mistakes in my first calculation attempt, and then in my next post I fully called them out (to have deleted or amended the first post would have been hiding my error, but I don't try to cover up my mistakes). I also included the formula I used in the 2nd post.

But speaking of dodging, you haven't answered my questions: What is wrong with my formula? Why is measuring a drawing (which may not be to scale) more accurate than calculating directly from the numbers?

Look at the timestamps. I made my post before you added anything other than the corrected ETT. Your edited post, 8 minutes after my post provided a more correct stack and reach. The stack and reach you provided before my post was wildly incorrect.

It's more accurate because I used the right top tube measurement.

Stop ruining the thread. Get over yourself and fix your initial post where you based your calculations on the wrong dimension.

[NHAero]

Stack

[Mark McM]

Originally Posted by NHAero

I thought stack was the vertical dimension between BB center and the top of the HT along its centerline?

Why isn't stack of this frame not 448.5 (BB to bottom of HT along its centerline) plus 139.8 times sine of 72.5 degree HTA, which is 133.3, for a total stack of 581.8?

This is an excellent question. If you work out the stack by adding the vertical dimensions of the seat tube and top tube, you come out with number closer to the 557-559mm numbers Spoonrobot and I got. Something doesn't add up with the dimensions on the drawing.

[spoonrobot]

NHAero has the most correct stack, with his work shown. donevwil posted the correct stack first but didn't show his work.

I had thought the drawing was showing the headtube with estimates for headset cup thickness (20,15) but it's the actual tube dimensions given both measurements are customizable during the build process.

So the bare headtube is 139.8 which would be 581(.8) stack. My measurement was predicated on the assumption of bottom headset cup but not top headset cup (as is often done with other online geometry tools/calculators) so the "headtube" dimension I was using was 119.8 - incorrect. I have edited my initial post to highlight this error. Please excuse my hasty assumption.