Miter Sheet Translation ?

[Epicus07]

Looking at a custom BW and am torn about how it has a level bar drop with my usual saddle height and a short heat tube.

Can anyone generate a stack and reach based on this miter sheet ? I assume it’s to scale so CAD or something could accomplish this ?

[PortlyPuncheur]

I use bikegeocalc.com for these tasks.

[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.

[C40_guy]

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.

Are you sure about the TT length? Wouldn't that 54.75 get longer, not shorter with a horizontal bar?

[donevwil]

deleted, 448.5 dim is what I needed.

[spoonrobot]

If you print it out 100% portrait orientation it is almost exactly 1:100 scale. Incredible, or perhaps the program was designed as such. Either way I am impressed.

[spoonrobot]

ETT 555
Stack 565
Reach 387

This is to the top of the headtube and not the hypothetical headset cup

ETA: Please see post #30, the drawing displays only the bare headtube with no measurements for estimated headset cup thickness.

[Mark McM]

Originally Posted by C40_guy

Are you sure about the TT length? Wouldn't that 54.75 get longer, not shorter with a horizontal bar?

Oops! You're right, I was using the value 513.2mm (which is the top tube from miter to miter, not center to center). Using the 545.5 C-C top tube number, the effective top tube is 558.0mm.

Crap! I got Stack calculation wrong, too! (But the reach should be right)

Stack should be 547.5 x sine( 78 - 73 ) + 532.5mm x sine( 73 ) = 557.0mm
Reach should be 547.5mm x cosine ( 78 - 73 ) - 532.5mm x cosine( 73 ) = 389.7mm

[Epicus07]

Thanks everyone,

Maybe I’ll just average the results and hope for the best ? :0

Measurements from seller:

TT: 54.5cm (CTC)
ST: 51.5cm (but compact geo) CTC
Crank to Saddle: 728mm w/ estimated level bars
HT: 14cm
Stem spacers: 20mm + 2.5mm on top
Stem length: 90mm
Chainstay: 430mm

[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

[spoonrobot]

I only have my cheapie travel calipers but they seem to agree with the pixels. Please excuse the parallax.

[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.

[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.