Is there something wrong with axle holes?

[Roland Melkert]

Looking at the radius 4 parts (e.g antenna, tech flex axle endings)

In real life they fit the inside axle holes, but in our library the max radius to fit in axle holes is only 2.8284 LDU ( sqrt(2^2+2^2) ). This seems quite a big margin.

Is this on purpose or is ether the axle hole or the 4LDU bar stuff wrong but accepted over time?

Or I'm I missing something else?

[Michael Heidemann]

Hi Roland,
I do not have those parts on hand now to check the real dimension.

I guess that just in the beginning measurements are not very accurate.

Also keep in mind that all the parts we are producing are approximations.

But they should fit like in real.

Maybe you discovered an error that was there just from the beginning. Or maybe parts changed over the time and we can not in any case date a part that we have in our hands.

Anythink is possible - just my thoughts, but maybe there is a reason?

[Michael Heidemann]

Are you talking about building possibilities like shown in the attached file?

If yes, where is the problem?

[Max Martin Richter]

It's a quite simple reason.
When I take the axle primitive and inline it, is see that each side of the cross is 4 LDU wide. That means 1.6 mm IRL.
But when I measure a random choosen axle, I get 1.8 mm (4.5 LDU) for this wide.

Conclusion our axles and everything else concerning it is about 0.5 LDU too small.
What to do now?
Update all parts or let it as it is?

/Max

[Roland Melkert]

No, I would like to put e.g. a gear on that antenna.

[Max Martin Richter]

Mike, he is talking about this problem I think. (See attached file)

[Roland Melkert]

I don't want to cause such a big change, I don't think it's that big of a problem in daily use.

I just encountered this oddity while tweaking my part snapping code to accept antenna's etc on axle holes.

[Michael Heidemann]

In real life they fit the inside axle holes, but in our library the max radius to fit in axle holes is only 2.8284 LDU ( sqrt(2^2+2^2) ). This seems quite a big margin.

Ok - please define "axlehole". We have a lot of primitive to cover axleholes.
Please tell me a part no. of the part that should fit into that axlehole.

I need to have those data to determine where the problem is.

Forget this post, I just saw the other answer - now I know what you are talking about.

[Max Martin Richter]

I saw this some years ago, while building different models. The same problem occurs, when adding a flex hose into something.

[Tim Gould]

Gears on bars is a dangerous game, but certainly one the works in real life. If you use e.g. a 4l bar, there's a good chance it willl fuse onto the gear and become pretty much stuck forever.

So probably the minimum cross-diameter of the hole is a bit smaller than 8LDU, but definitely bigger than 5.7LDU.

Tim

[Roland Melkert]

I'm using 0.6666 of the (female) axle shaped radius +- 0.1ldu, for it to except at the moment.

I was mainly thinking about the rubber flexible axle/bars those are used inside axle holes alot in official models.

[Michael Heidemann]

rubber flexible

That parts may fit also in other smaller holes. They are in fact flexible because they are made from rubber.

But I agree, that - while talking about connectivity - this is a challange.

[Philippe Hurbain]

I noticed this issue long ago too - yes, a 3.2mm (=8 ldu) bar does fit rather well into axleholes!

When I take the axle primitive and inline it, is see that each side of the cross is 4 LDU wide. That means 1.6 mm IRL.
But when I measure a random choosen axle, I get 1.8 mm (4.5 LDU) for this wide.

I agree with your measurements... This means that we could have divided "axle circle" in exactly 4, this gives a very close value of 6*2*sin(22.5°)=4.5922 - this would have so much simplified life, and removed all those T-junctions around axleholes.
But axle arm thickness is not the only culprit, even with 4.59 thick arm, it fits a bar with a 6.5 ldu diameter (instead of 8)! This is easily explained because real life axlehole teeth are rather blunt! Actually this is the major contributor, as thickness increase adds only 0.85ldu diameter increase in center hole, while we need a 2.35 ldu increase.

Conclusion our axles and everything else concerning it is about 0.5 LDU too small.
What to do now?
Update all parts or let it as it is?

Updating all axle primitives to increased thickness would be feasible but would most probably leave LOTS of misfits here and there. Unsharpening teeth would be an easier route, I don't know how realistic it would look, but probably that could be done with minimal parts overhaul.