I fully understand the need and reason to use taper offset spacing when doing closed crosswraps. However, a small thing I don't understand is if I wanted an even number of patterns on the 0* axis, seems easier to figure with an odd number of repetitions. How do you account for this?

Here's what I've come up with if I used measurements of a butt of 53mm, mid of 50mm, and tip of 47mm:

5 repetitions of the pattern:
0* axis |------47-----|----48.5--|----50----|---51.5--|----53---------|
180* axis |-23.5-|-47.75-|----49.25--|--50.75--|--52.25--|--26.5--|

6 repetitions of the pattern:
0* axis |----47-----|----48.5---|----50----|----50----|----51.5----|-----53------|
180* axis |-23.5-|-47.75-|----49.25--|---50----|--50.75--|--52.25---|--26.5--|

Is this right for the 6 repetitions? If I was concerned about maintaining the length of the wrap could I just rotate the 5 repetition taper offsets and go from there? But then it would leave me with a short area to do the finish wrap, no?


Sean

Sean, the 26.5 you're ending up with on the 180* is just a half pattern that will be even with the last mark on the 0*. Your wraps won't cross those 26.5 marks on the 180*. I have an Excel spreadsheet for calculating these in both squared patterns with variable length and stretch to fit a fixed number of patterns over a fixed length. I can email you a copy if you want but your email address is hidden.

Length to Mark on 0 Axis:
1 2 3 4 5 6
47.0 48.2 49.4 50.6 51.8 53.0
47.0 95.2 144.6 195.2 247.0 300.0

Length to Mark on 180 Axis:
1 2 3 4 5 6
23.5 47.6 48.8 50.0 51.2 52.4
23.5 71.1 119.9 169.9 221.1 273.5

Understand about the placement of the half patterns. I read it is too hard to use anything other than 1/2 mm on the spacings and it won't really be noticed, is this true? Also, what are you using to measure you offset with to be able to be that detailed? Could you round up or down where needed to the closest 1/2mm? I used a formula from one book on a rod and came up with some really wild numbers and put it on the back burner. Revisiting it now...

My email address is sdoran@caci.com Thank you in advance for the spreadsheet!


Sean

Sent

"too hard to use anything other than 1/2 mm "
The professional wrappers on this board could answer your question with more authority than I could, but... The ruler I use is only marked in single mm's so I eyeball the fractions as close as my fat marker can get. I find that any slop can easily be accomodated during packing but the closer I can get the threads the less I have to accomodate.

James sent me his utility and it's now up on the Rodbuilder's Library website
on the Threadwork page.

Thanks James!

Raymond Adams
Eventually, all things merge, and a river runs through it..