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Full Version: Rotation & angle of universal joint?
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(2019-10-04, 7:23)Philippe Hurbain Wrote: [ -> ]Not a huge restriction, to use universal joint ends with stupid origin (3712 and 575) you only have to translate them by 30 ldu to place their origin at the right place, apply script, and re-translate them in opposite direction (using relative grid).

I indeed think there is something not addressed, configurations where one i/o axle needs to be rotated. If I am not utterly wrong, this occurs when input and output axle do not sit in parallel planes. See attached example.

That is because the input and output angle of universal joints are not (always) the same.

With the model I used in the YT clip the steering wheel was already rotated to compensate for this.

If that's not the case you should use (axle) snapping to work each joint from the previous one to account for the new rotation at each step.

As for the weird origins, for the final version I'll add information to the script so it recognize the joint parts in order to apply the corrections if needed.
(2019-10-04, 16:48)N. W. Perry Wrote: [ -> ]There is one tiny quibble with this solution: it doesn't allow placing the end parts tight together on the 2L link section, because that would require sliding the angled axle slightly downward, and we don't know that exact position. I can envision a new feature that would allow such a placement…but I'll post about that another time.  Wink
Yes, it would need a more specialized version of the script which does both joints in one go.

It should be possible by extending the steering wheel direction and finding the best intersection point on it instead of blindly using a point B.
Quote:With the model I used in the YT clip the steering wheel was already rotated to compensate for this.
And how do you know the needed rotation angle???


Quote:If that's not the case you should use (axle) snapping to work each joint from the previous one to account for the new rotation at each step.
Mmhhh... I tried that, but I can't seem to get the knuckles oriented right.
(2019-10-04, 18:09)Philippe Hurbain Wrote: [ -> ]And how do you know the needed rotation angle???
I think I applied the animation angles to the static model (right mouse menu in animation mode) at one point Smile

(2019-10-04, 18:09)Philippe Hurbain Wrote: [ -> ]Mmhhh... I tried that, but I can't seem to get the knuckles oriented right.
May try something like:

- Apply like above
- place the connecting axle, make sure it's snapped to the first joint (tmp hide the second one if needed)
- Select the center axle
- rel grid
- select the 2nd uni's first end
- ctrl+home
- rotate 90 deg to align with the axle again.
- reapply the script on the 2nd joint
- snap the steering wheel to the 2nd joint's 2nd end.
(2019-10-04, 17:46)Roland Melkert Wrote: [ -> ]Yes, it would need a more specialized version of the script which does both joints in one go.

It should be possible by extending the steering wheel direction and finding the best intersection point on it instead of blindly using a point B.

That's exactly what I'm thinking. I envision a feature I call "vector snapping"—it's similar to rotation snapping (as suggested here), but instead of finding the angle to snap to a nearby single part, it finds the intersection of two relative axes: that of the part/assembly being rotated, and that of another one nearby, allowing you to translate the second part/assembly along its own azimuth to intersect the one being rotated.

(I envision it as a snapping feature, but I suppose it doesn't have to be. You'd probably already know which second axis you want to align with, so you could just select the two axes and apply a function to find the intersection point.)
(2019-10-02, 11:33)Philippe Hurbain Wrote: [ -> ]Note that I haven't found the 853/956 Auto chassis on the OMR, but it's available on Eurobricks. Needed it for basic geometry... but the universal joints are slightly wrong there, the middle connections are badly placed.

Well, now that my model is finished, I'd be happy to submit it to the OMR. What do I need to do to make it compliant?
(2019-10-05, 1:53)N. W. Perry Wrote: [ -> ]Well, now that my model is finished, I'd be happy to submit it to the OMR. What do I need to do to make it compliant?

There's a tutorial on the wiki. It mostly involves using mpdcenter so if you haven't installed that that's a good first step.
(2019-10-05, 1:53)N. W. Perry Wrote: [ -> ]Well, now that my model is finished, I'd be happy to submit it to the OMR. What do I need to do to make it compliant?
I use LDCad for that. File -> cleanup. Here is the setup I apply...
(2019-10-04, 18:24)Roland Melkert Wrote: [ -> ]- Apply like above
- place the connecting axle, make sure it's snapped to the first joint (tmp hide the second one if needed)
- Select the center axle
- rel grid
- select the 2nd uni's first end
- ctrl+home
- rotate 90 deg to align with the axle again.
- reapply the script on the 2nd joint
- snap the steering wheel to the 2nd joint's 2nd end.
Sorry, I don't get it... Problem is that I need to rotate an end joint unit, and I can't figure the needed rotation. The script only places and rotates knuckles and inner joint (next to center axle) units, not the end joint units.
(2019-10-05, 11:58)Philippe Hurbain Wrote: [ -> ]Sorry, I don't get it... Problem is that I need to rotate an end joint unit, and I can't figure the needed rotation. The script only places and rotates knuckles and inner joint (next to center axle) units, not the end joint units.
You don't need an angle, just apply the same orientation the script applied to the second universal end (or the axle snapped to it).

This is what the ctrl+home combined with the relative grid does in my above sequence.
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