topic Joint question in Fusion Support Forum

Joint question

Anonymous — Sun, 11 Aug 2019 19:53:17 GMT

Is there a way to be able to manually manipulate revolute joints separately? For example, on the attached screen shot, I would like to be able to rotate the rotating arm (smaller square tube) to an angle of (for example) 35 degrees by moving the rotating lever (L shaped lever) with my cursor, then just move my cursor to the leveling lever (straight lever) move it for and aft without moving the rotating arm. I'd like to be able to do this without having to ground anything other than receiver (larger square tube). Any help is appreciated.

Re: Joint question

davebYYPCU — Sun, 11 Aug 2019 21:25:00 GMT

Yes you can do that. Not the way you have it now.

You have something grounded, and 2 Rigid Joints, 1 Revolve, so only one joint allows movement. To move two parts independently, you need 2 Revolves, and 1 Rigid.

Might help...

Re: Joint question

Anonymous — Mon, 12 Aug 2019 10:48:42 GMT

I'm afraid that didn't work. I tried all the 2 revolute 1 rigid combinations
available. I guess I'll either have to relocate the leveling lever
(straight) back to the receiver (2 inch square tube) or go through the
process of grounding the rotating lever (L shape) each time I move it and
subsequently want to move the leveling lever. The first choice is not how I
want it built in the real world, and the second will be cumbersome for demo
purposes. The real part involves a latch that goes to an anchor post on the
receiver. The latch has a series of holes that must line up with a pin on
the post to secure the position of the leveling lever. Since the attach
point of the latch on the leveling lever moves in an arc, lining up the
latch holes with the pin requires a fair amount of trial/error which will be
complicated by having to ground/unground the leveling lever. I could
possibly resolve this by putting a slot instead of holes in the latch then
using a slider joint, but again, not the way I plan it in the real world. In
any event, thanks for taking the time to come up with a suggestion.

Re: Joint question

davebYYPCU — Mon, 12 Aug 2019 11:11:42 GMT

You have a hole through 2 sq tubes.

A pin in a straight bar, and bracket.

How many combinations can there be?

Happy to help, but not if I can’t understand the challenge.

Re: Joint question

Anonymous — Mon, 12 Aug 2019 13:06:08 GMT

Again, thanks for your willingness to help. The attached screenshots should
make it more clear what I'm trying to do. I want to be able to rotate the
attach arm (smaller square tube) using the main angle lever (L shaped) then
fix it in position, securing it by affixing one of the holes in the main
angle lever to latch connector (horizontal bar with holes) to a pin in the
latch arm (rearmost vertical bar). As currently drawn, once I do this, it
allows me to rotate the mockup angle lever (forward most vertical bar
affixed to the mockup angle lever bracket with a revolute joint) as
intended. The problem I am trying to solve is how to rotate the main angle
lever to latch connector (horizontal bar with holes) about its revolute
joint without first grounding the attach arm (smaller square tube). Having
to ground it each time makes it difficult to line up the holes to the pin.

Ultimately what I want to do in the simplest way is adjust the angle of the
attach arm up or down with the L shaped lever, then rotate the platform
mockup (forward most plate attached to shaft going through the rod ends)
using the main angle lever (which is to be attached to the platform mockup
with two revolute joints). For example, I rotate the attach arm up 35
degrees then rotate the platform mockup such that it remains 90 degrees to
horizontal.

Re: Joint question

Anonymous — Sat, 17 Aug 2019 11:33:18 GMT

I have the receiver (larger tube) grounded so that the smaller tube and anything attached to it will revolve. I've tried changing the two rigid joints affixing the bolt and nut to revolute but this doesn't work either. If I remove the bolt entirely or suppress it and just have the revolute joint at the bolt hole between the two tubes it also doesn't work once the hinge is attached to the plate. Very frustrating, especially because in early versions of this part there was no problem until I introduced the concept of a hinge. Thanks for your input.

Re: Joint question

davebYYPCU — Sat, 17 Aug 2019 12:06:28 GMT

So I think I am getting closer to the problem.

Receiver is grounded, you drag the locked lever, and that will cause, all to rotate around the hole in the receiver. When at an appropriate angle, the other lever is required to still be vertical.

Seems like Component Drag does work, (other thread)

When driving the Joints- all works as expected?

Disregard levers for now,

You say the first Revolve Joint is misbehaving if you add the detail of a Bolt (axle) and its nut.

Again no Joints are flagging errors, red icons in the Joint list.

I would normally ask for the file to interigate, but will not get to a desktop till Tuesday my time. So confirming Q and As will work till then.

Re: Joint question

Anonymous — Sat, 17 Aug 2019 12:49:10 GMT

So that I don't waste your time I'll send you the file, play with it this
weekend, and if I can't solve it look to hear from you next week. Sorry to
be ignorant, but I'm new. How do I send you the file?

Re: Joint question

Anonymous — Sat, 17 Aug 2019 18:26:25 GMT

I hope these files will work. The one title Attach Arm Experimental Manual basically works as I need it to. I have to add a slotted or drilled connector bar between the two vertical levers so I can, if necessary, manually adjust the angle of the very front plate, but since I have this working between the L shaped lever and the short vertical lever I don’t anticipate any issues (will probably require a second short vertical lever).

With regard to Attach Arm final, it occurred to me I need to provide a break away action for the front plates in the event the device they carry comes in contact with something. So I was going to introduce a third mounting plate hinged to the first (the solid one) mounting plate. These two plates would further be attached at the opposite end of the hinge with a breakable plastic strap providing the breakaway action in the event of contact. I added a second plate, hinge, breakaway strap, spacer between the plates, and a support ledge for the second plate to rest on. I had this all drawn up and when I went to manually activate the lever with the cursor to rotate the smaller tube and attached plate, but it would only move in tiny increments each time I tried to drag it with the cursor. It had worked fine up to the point of installing the first mounting plate. I started deleting stuff until finally, when I deleted the hinge, it worked again. For some reason, when you add the hinge (drawn or McMaster import) using a rigid joint to the plate, it stops the rotating function. If you suppress or delete this joint, it works again. I’ve tried a lot of different joint combinations and nothing has worked. Further, I can’t see how a rigid joint between two components completely unrelated to the revolute joint can have an effect. It hasn’t worked this way in other projects.

As always, thanks for any help.

Re: Joint question

Anonymous — Sat, 17 Aug 2019 20:29:24 GMT

FYI I was able to get the model to work correctly by installing a motion link between the revolute joint joining the tubes and the one joining the lever and bracket. I had tried this some time ago but couldn't get it to accept zero degrees. I finally set it up at 90 degrees/.1 degrees and it solved the problem. I just don't understand why I didn't have to do this in earlier versions of the same part. Thanks for the help.

Re: Joint question

davebYYPCU — Sat, 17 Aug 2019 22:09:04 GMT

Yes, a motion link would not work with one side using zero. Has to be a ratio.

Pleased your underway.