Miters for me are paper templates and files. If it's possible, I'd like to see the orientation of the top tube miter templates changed to match each other. If they were the same (as in center of the template being either the top or bottom of the tube), it would be much easier to use one center-line to keep miters in phase.
I find it far more difficult to orient the second template where the ends are referenced, and it usually ends up out just a touch out of phase as I'm sneaking up on the proper length. Unless I'm missing the reason for the current setup, I think it would be very helpful.
Currently, if you scribe a line along the top edge of your top tube, you'll need to align the line marked "top" on the front miter template with that scribed line. You'll also have to align the line marked "top" on the rear miter template with that same scribed line. As you've pointed out, the line marked top on the front template is in the middle of the template. Meanwhile, the line marked top on the rear template is on the edge of the template. I can see that it might be slightly easier to get things lined up if both top edge lines were in the middle of both the front and rear templates. Therefore, I will see if I can change this in a future update of BikeCAD Pro.
Having said that, I am concerned that the difficulty you are experiencing in getting the templates to line up might not have as much to do with the orientation of the lines on the templates as with the scale of the template. The length of the template should be exactly equal to the circumference of the tube. If it is not, be sure that when printing from your PDF reader, that you have disabled any options to scale the print. There's info about that here.
Thanks Brent. I printed the template with both the "fit to page" and auto rotate boxes unchecked, so it should be good.
I just tried it again as shown in your link, but I got the same result. The template is just a bit too small and the outside lines don't get close enough to overlap (which is the goal, correct?) My design calls for 28.6 top tube, and I just measured the tube with calipers to make sure it was sized correctly.
I hadn't considered measuring the template, so I checked it out. If I multiply 28.6 by Pi, I get 89.85. When I measured the template with the calipers it appears to be 89.31. Assuming my measurements are accurate, the template is ~.5mm undersized. Your thoughts?
Ideally the two outside lines would overlap, but only just barely. However, I would not be alarmed by such a slight disparity in size. If we really scrutinize the situation, we could also take into account the thickness of the paper we're printing our template onto.
If the circumference of a 28.6mm tube is 89.58mm, then the circumference of the outer face of the paper template wrapping that tube would be 90.46mm. (Here, I'm assuming a paper thickness of 0.09652mm) That's a difference in circumference of 0.6mm!
Because paper thickness is not accounted for when generating the templates, you could consider increasing the diameter of all tubes by two times the paper thickness.
However, this discussion began with the challenge of orienting two templates at either end of a tube that might be more than half a meter long. It sounds like all things considered, you've got things really dialed. I guess under these circumstances, I was wrong to assume some deeper problem. It seems you are just looking for a way to improve your already exacting tolerances. If changing the orientation of the top tube miters will help, then I will investigate ways to make that happen in a future update. Thanks for the suggestion.
I found this thread after searching the site. Adding twice the paper thickness to the diamater of my tube, as you suggest here, I'm now getting better results than ever before with the templates. On a 38 mm tube, that thickness really makes a difference. I wonder if you would consider adding this tidbit to the page with instructions for generating and using the paper templates. I think it could help folks like me who didn't realize why the paper wasn't quite making the full circumference. Thanks!
Thanks for the feedback. I've added a note about paper thickness at: bikecad.ca/miter_templates.
Right on - thanks, Brent!
Thanks, Brent. I just thought the miter templates being in-phase would help eliminate a variable while sneaking up on the proper top tube length. Just to play around with the idea of paper thickness, I plugged in 28.85 and that seems to be just about right for the template to touch ends. Don't get me wrong, I'm not complaining about anything. I just need to understand how it works. Your program was worth every penny.