[LDCad] Rubber band templates question

[N. W. Perry]

For band/belt templates in LDCad, the radius of a point is measured to the center of the path. I thought it would be handy to offset the path skin so that its inner edge follow the radius (i.e., the radius of the point is the same as the part it goes around).

I thought adjusting the alignment parameter was the way to do this, but it didn't work. It just breaks the path into segments with wide gaps (and they aren't noticeably offset from center).

Is there a simple way to adjust the template to do this? Or would I have to create a donor part with the origin shifted (and would that even work)?

[Roland Melkert]

For band/belt templates in LDCad, the radius of a point is measured to the center of the path. I thought it would be handy to offset the path skin so that its inner edge follow the radius (i.e., the radius of the point is the same as the part it goes around).

I thought adjusting the alignment parameter was the way to do this, but it didn't work. It just breaks the path into segments with wide gaps (and they aren't noticeably offset from center).

Is there a simple way to adjust the template to do this? Or would I have to create a donor part with the origin shifted (and would that even work)?

The alignment parameter acts only on the y axis (path direction).

Offsetting the donor would work but you must set the donor center to "Part origin" or it will correct for it automatically.

I could add a "Outer border" option to the donor center option list, to you do this without changing the donor.

[N. W. Perry]

The alignment parameter acts only on the y axis (path direction).

Ah, I thought that was what "offset" does. (Or are they basically the same operation, just done at different stages of the process?)

Offsetting the donor would work but you must set the donor center to "Part origin" or it will correct for it automatically.

Fair enough, I just wasn't sure if that would mess with the deformation process. Although, why would you give the option if it did… ;-)

I could add a "Outer border" option to the donor center option list, to you do this without changing the donor.

That might be useful at least for some use cases. Normally, it's no problem to just add half of the donor width to the radius of the bearing part, but I was working with some non-integer scaling factors (e.g., to get a skinnier rubber band) so then you have to type the radius manually.

[Roland Melkert]

Ah, I thought that was what "offset" does. (Or are they basically the same operation, just done at different stages of the process?)

Offset influences the origin of the donor.
Alignment influences how the donor is placed within a segment of the path.

[N. W. Perry]

Offset influences the origin of the donor.
Alignment influences how the donor is placed within a segment of the path.

I see. I haven't yet encountered a situation where I'd use either of these then, but that just speaks to the great power and flexibility of the templates.

Incidentally, I've worked out that for an exact fit of the square rubber band on the wedge belt wheel (4185), you need an x/z scale factor of .8125 for the path skin, and a radius of 29.125 (or a donor origin offset of 1.625). Just in case anyone happens to search this group for that info.