Workspace freezes when working with STEP hardware

[OTE_TheMissile]

So I'm working on a new motorcycle trailer hitch (not sure if I'm allowed to say for what model yet, the rest of the RIVCO crew were debuting the prototype at the Indianapolis dealers-only expo over the weekend) that basically consists of a flat plate that hangs under the back edge of the fender with arms that reach up to anchor it to the same chassis structure the rear shocks mount to, then there's a pair of tubes that sneak between the tire and the fender to bolt onto the plate. These tubes follow horizontally forward & anchor to a low point on the frame to triangulate the design.

Anyway, I've got these 1/4-20 screws that secure the tubes to the plate on each side of the tongue, and it dawns on me I could replace the 4 screws with 2 U-bolts to not only attach the tubes but give the bike's rider a great place to clip on the safety chains. I jump back on McMaster-Carr's site and download a STEP of the proper U-bolt, remove the 2 nuts the model comes with and save it as an AD_PRT. But when I go to add it to the Assembly, as soon as I Preview any constraint I'm about to place the two constraint references disappear and the constraint fails. I figure it's just a hiccup having to do with the imported STEP model, so I open the U-bolt model to add a couple of axis (axii? axuses? axies?) and planes. Thing is, soon as I click "OK" for the reference feature creation, the workspace locks up. Everything still works, I can still move and rotate the model, all the tools still work, it's just like somebody took a screenshot of the workspace, printed it out, and taped it to my screen. I did the "minimize and restore" bit and got the Grey Workspace treatment.

Restarted Alibre, still does it. Never really had a functional problem with McMaster's STEPs before (cosmetically, some of the rush jobs they do on 3D threads crack me up), any ideas?

If you want to play with the U-bolt yourself, the McMaster-Carr part number is 3043T12, http://www.mcmaster.com, otherwise see if you can get the model I'm using to Assemble to something. Use 1/4" holes spaced 1" apart center-to-center. There's a bit of a straight cylinder between the threads and the U-bend that I'd think you'd be able to Align to a pair of holes, and I'd just use either the reference plane or the ends to Mate to the surface of the material to be secured.

 

[cherkey]

Heya Missile,
No problems using the U bolt here...assembled with a dummy plate.
I usually don't have issues when I use McMaster - I'll import the step, and save the part as Alibre assembly. The individual parts are then created for the assembly. I'll then just use the individual part that I need. I don't know if that will make a difference or not - it just sounded to me like my usage procedure was a bit different.
I also usually 'remove' the threads with an Extrude Boss when using a model for fit and function. Again, don't know if it will help or not, it's just how I use 'em.

 

[OTE_TheMissile]

I'll try that, I just didn't need the nuts it came with so I got rid of them.

And yeah, I'll gloss over the threads too if need be, but I'd kinda like to have them in this case. If I covered them up then I'd have to keep measuring them over and over again to remember how far down they go.

Pop quiz: is that U-bolt model right-hand threaded or left? :lol:

 

[NateLiquidGravity]

If its a McMaster-Carr part then probably both. At least that's how I remember they modeled threads. Mirrored in half. :mrgreen:

 

[OTE_TheMissile]

:mrgreen:

The latest in hardware technology: the universal-handed thread! Brought to you by the same company that manufactures drill bits for making square holes.

I've only seen that with shoulder screws/bolts and now U-bolts. Kinda funny when you think about it, imagining a CAD tech getting the first helical sweep in and not immediately going "OK, that thread's done!"

BTW Cherkey, I re-imported it and opened just the bolt file instead of trying to discombobulate it from the STEP assembly, now it works just fine 8)

 

[cherkey]

Glad to hear all's working well

 

[DavidJ]

... Brought to you by the same company that manufactures drill bits for making square holes.
8)

These may not be common, but they do exist. It is perfectly possible to drill square holes (triangles too).

 

[NateLiquidGravity]

Wow! http://upper.us.edu/faculty/smith/reuleaux.htm Must have to really clamp that material down.

 

[BernardK]

Off topic really, but would it assist to insert the U bolt from above? If the nuts come off in use, the bolt won't fall out. Also easier to check tightness from below. Good idea to use a U bolt as it can't rotate when tightening.

 

[OTE_TheMissile]

No, that'd defeat the purpose. This is a "hidden" hitch, everything between the two "arms" that bend up from the sides of the plate gets tucked inside the rear fender, and the "arms" themselves sneak between the fender and the saddlebags, so if the customer isn't trailering with their motorcycle they can remove the hitch receiver/tongue piece, and unless you're really looking for it nobody's the wiser that the bike has been equipped with a trailer hitch. As for the nuts coming loose, that's what blue LocTite is for 8) . Assuming it doesn't rise the cost too much we could also use nylon insert locknuts to secure the tops of the U-bolts to the assembly. This is just an idea I had, haven't run it past the boss-man yet.

I'd post better pictures (or a screenshot that includes both the tire and the wheel instead of just the tire), but that'd give away which bike this hitch is being made for.

 

[OTE_TheMissile]

Here's an example of safety chains on an automotive trailer. I see a lot of people run the right chain to the right side of the hitch and left to left, but this is INCORRECT! They should be crossed so that if the hitch somehow comes loose, the trailer tongue will drop into the chains and give the driver enough control to pull over to the side of the road and recouple the hitch.

 

[OTE_TheMissile]

Boss-man canned the U-bolt idea, just wants to drill holes in the plate for safety chains.

Aw well, I tried. & thanks for the tips guys, even if this project turned out to be unneccesary I'm sure I'll run into something like this down the road and I'll know what to do 8)