joints and motion

[dieselguy65]

this mechanism has been haunting me for some time now.

trying to get the design finished before the end of this month

this is a very simplified and scaled down version, of the motion i am trying to achieve.

i can get this far, but that last joint i cannot get to work

the real model has a mirror image of this mechanism facing it, with soild bars running between to tie them together

i have been succesfull, just getting a joint to work for the upper wheel, using contact sets by itself.

but not once i have it part of this entire piece.

this seems very simple. i am sure i am missing something

anyone know how to do this?

thanks, Brian

[Anonymous]

Hello @dieselguy65 

I am trying to understand your model mechanism 🙂 

what I  understood that you have problem with the green body you want to create revolved joint between the wheel and bar ,is this what you need ???

If not please attach more pic Explaining more details and I hope I will help you

[etfrench]

How is it supposed to work?

[TrippyLighting]

The only way I know how to make that work in Fusion 360 is with a contact set between the "box" and the "upper wheel". YEOu'l have to make the upper wheel slightly smaller in diameter than the slot it moves in.

HOWEVER, I would like to advise against using contact sets in anything real outside of this simple assembly. They eat a lot of performance and in a more complex assembly normal joint can start behaving odd and outright dysfunctional.

[dieselguy65]

Sorry, i didn't explain. Kind of figured was obvious. The l shape piece
starts out with the long leg in line with the straight slot. Both rollers
in their respective slots. As the l shape piece moves, the roller along
its long side travels up the slot. It rotates in the l piece. The other
roller needs to follow the slot it is in. There's the problem, i can't
get a joint to do that, as it follows it, the l shape piece transition
from the original position, to a position at an angle, that is regulated
by the slot thr upper wheel is in. I been working on the big project alot
of hours. Just drew this simple example because i can't share the full
project publicly.

[etfrench]

How is it going to follow the slots when there isn't enough distance between the wheels?

[dieselguy65]

What do you mean? There's plenty of distance between the wheels. I can
move it into both ends of thr positions now. There's just no joint
movement that allows the multi axis slot to work in conjunction with the
linkage that i can find.

[dieselguy65]

When i get back in thr office, i will upload image of it at both ends of
thr travel. Sorry i really thought it was easy to see how it moves. It's
a very simplified model, i didn't put in any clearances between the wheels
and the wall faces, in the real model they have clearance (obviously a
2inch wheel in a 2 inch slot won't work very well at all)

[TrippyLighting]

Did you read my post ?

[jasonhomrighaus]

It works fine in contacts but the lockup happens because somewhere you have an interference or a misalignment that is not allowing the contact set to move. If you wanted to send me your main model I could help you locate it, easiest way to sort out is to progressively attach the parts till things lock up.

[dieselguy65]

I'm out in the field now. Which post? I'll check on computer when I'm
back invite the office.
Thanks, Brian

[etfrench]

Perhaps you're using a different model.  Here's what I see from your posted model:

[dieselguy65]

yes, contact set is the only way i found. however, the real model is big enough fusion locks up as soon as i enable contact sets.

[dieselguy65]

not sure what you are trying there, but the model will travel until the long leg of the L is parallel to the long slot

[dieselguy65]

yes, thats it, minus the l shape piece.

i am missing what you are trying to say about distance.

the lower wheel does not and does not need to travel to the bottom of the slot. in the real model, the mechanism that pushes the wheel up reside in that space.

i didnt model it, as it isnt necessary to get the joint working. the upper wheel does not need to travel to the end of the slot, theres another device in that space.

[dieselguy65]

here, i edited the model. to give more range of motion so the path is clearer i hope.

i also enable contact sets.

now you can see how it moves.

what the movement does now is what i need it to do.

but without using contact sets.

as Trippy said, i do not believe its possible.

it seems like a simple movement, that i have been a year now trying to find a work around, it works on this model, which is similiar enough to the real one to be used as proof of concept.

but it locks up on the real model.

honestly, this is the deciding factor between me sticking with fusion, or moving on. i feel this is very simple to make work.

i dont want to learn Inventor or Solidworks just to do this. but i may have to,

there will be many more models of the movement coming thru in the future. only varying in dimensions but the same principle.

i have to be able to provide customers a working 3d model of the design. otherwise, i am down the drain before getting off the ground with this new business venture.

i am completing the final stages of the first unit in the field. but all the work on that 3 angled slot was done old fashioned way by hand calculations. no fun at all when there is a software as powerful as this on the market.

fusion has done everey task i have needed, other than this one. which is a real downfall

[dieselguy65]

edited to be more clear.

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