System and Studless Techinc Standards Problem

[Tim Gould]

A while back I posted about a little curiosity I had spotted while modelling a new part. It was not much of an issue there, but today I discovered a part where the problem is much greater.

The problem is summarised as follows:

1) We model studless technic connections (eg. liftarms, pin connectors) at 18LDU wide, which is slightly too small for the real ones

2) We model technic holes at 10LDU from the top of a brick, which is slightly too low (9LDU is closer). This difference is actually large enough that connections from a system brick like 87087 to a technic brick like 6541 are forbidden in official models.

3) When studless technic connections are merged with bricks these two problems combine to make LDraw parts not match flush at the top, while real parts will be flush.

There are more parts appearing like 85943 and it might be worth coming up with a standard workaround for these parts.

In the case of 85943 it was modelled with 20LDU liftarms which I think is not ideal. Better, IMO, would be to slope down over about 5LDU at the join and then leave the rest at the 18LDU diameter.

Thoughts?

Tim

[Philippe Hurbain]

I agree that there is a problem for a few pieces such as this one, but I don't see a good solution avoiding rewriting all Technic parts...
For this specific part I don't see such a big problem with present solution but I wouldn't object if it was modelled with a sloped top on liftarm section to have the tip 18ldu wide.

2) We model technic holes at 10LDU from the top of a brick, which is slightly too low (9LDU is closer).

According to LDD models, it's exactly 9.5 ldu.

[Tim Gould]

I agree that there is a problem for a few pieces such as this one, but I don't see a good solution avoiding rewriting all Technic parts...

No of course not. This would be absolutely the worst solution.

For this specific part I don't see such a big problem with present solution but I wouldn't object if it was modelled with a sloped top on liftarm section to have the tip 18ldu wide.

It would be nice to have a general rule though. eg.
model liftarm tips at 18LDU diameter and slope in if necessary
or
in such cases model the part at 20LDU diameter

I think we'll be seeing more of these parts in the future as system model designers are encouraged to use studless technic to make bigger models with fewer parts. It's already happened twice in 2011.

2) We model technic holes at 10LDU from the top of a brick, which is slightly too low (9LDU is closer).

According to LDD models, it's exactly 9.5 ldu.

So probably liftarms should be closer to 19 LDU diameter.

[Steffen]

Not really an answer to your question, but while researching about this,
I found this (official ?) document for LEGO modelers. Maybe you don't know it yet,
but it was really worth reading for me, I found it terribly interesting:

Look here:
http://cache.lego.com/downloads/brickfes...stress.ppt

[Greg Teft]

Steffen - great find!!!

[Magnus Forsberg]

I have now adapted the liftarms.
I gave them a 10LDU long slope down to the liftarm. 5LDU looks bad, IMHO.
I also added some condlines to smooth the visual apperance.

Any more parts found, or opinions about this issue?

[Tim Gould]

I like it.

More generally I guess it's an issue we deal with on an ad hoc level. Sometimes a slope isn't really appropriate but for this type of part I agree it's the best solution.

Tim