Motion Link issue with Bevel Gear

[Drewpan]

Hi All,

After having delusions of grandeur about having enough knowledge to tackle an actual design of my own instead of doing a tutorial of someone else's, I decided to design a simple screw jack. So far I have imported Bevel Gears from the McM-C cattledog, designed a core for the screw and designed my own Universal Joint to drive the Bevel Gears. I have also put in the basic joints - my Lifting gear rotates around the Core and my Universal Joint works. What I am having trouble with is getting the Motion Link to work properly on the Driving Gear.

The animation seems to be saying it is working but I cannot drive the actual joint. I have the meshing correctly set up between the Drive and Lift Gears. I know that it will be something simple in Grounding components or something similar. I have been playing with these settings but cannot get it working. I also tried changing the rigid joints on the Universal Joint pins to Revolute joints in case this was locking up everything. I don't think the Rigid joint between the Universal and the Drive is doing it.

There is also a minor error with a couple of extrusions due to me making a change well after I created them to the Sketches and not picking up the error. I am not quite sure how to repair this either.

Any help would be appreciated.

Cheers

Andrew

[davebYYPCU · Accepted solution]

Origins, Origins, Origins,

Origins, are so important when using animations.

You moved the main gear off the Origin, I put it back.

The shaft profile sketch has nothing to refer to, so I broke all the Projection Links.

New sketch in the shaft to locate the Drive gear offset. 

Used this for the Small gear revolve, set up the motion link again.

Trick component is not required - gone.

You said your Uni works as expected, no changes there.

Yes, something has to be Grounded, the Main Shaft for the time being.

Capture Position before a Joint is deleted after making the joint.

Sorted....

Might help....

[Drewpan]

Thanks for the help.

I have done heaps of tutorials and this was the first one of my own design. Seems like I need a few more tutorials. The trick component came from a tutorial. I had seen it done another way that I tried first but it didn't work (or I couldn't make it work anyhow).

The advice I was given was to do the hard bit first and this was the hardest bit. I think I can manage the next bit of the actual lifting screw, then it is just the case to hold it all together. Thanks again.

Andrew

[davebYYPCU]

Yeah but the Base bottle case, not present, means you are working backwards.

Thrust bearing, acme thread, would lift the shaft so grounding it to get the other stuff stable had me thinking.....

Not sure why the trick Component was there, I deleted about 6 icons, compared to one sketch (point) would / does the same job.

You were right the Uni pins can be rigid (grouped,) saves some more time.

Avoid As Built Joints, Normal Joints and deleted Capture Positions are efficient.

Don’t be hard on yourself, you learn quicker with hands on tackling of these challenges.

[Drewpan]

Hi,

Thanks for all your help.

I have finally "finished" the design but I still have a couple of issues. I can't seem to get the Crown attached to the Base properly - I keep getting errors. Because the Crown is free to move I cannot test the full design to see if it actually works. There is a problem I know about with the Base Core and the Base not lining up but this is unrelated to the first issue.

I think I have the Jack Screw and the Lift Bevel Motion Link right but I still can't test it and I am not sure if I got the alignment right. There was no interference when I did it but I am still not sure.

There are a few interferences I have tried to fix that may be stopping the final thing working but I am just not sure how to fix them.

This project turned out to be a bit more challenging than I initially thought but it has been fun. I will probably never actually make one of these but it would be good to see it working in simulation.

If its not too much trouble, could you please have another look and put me back on the road.

Cheers

Andrew

[davebYYPCU]

I can’t get to your file, for a day or two, but, see if this list of operations help.

First do not use contact sets.  If you have them delete them.

Interference (depending on where) should not prevent overlapping movements, but alignment is critical.

my guess is that the crown gear and jack screw, are rigid jointed or one body.

The crown wheel revolves concentric to a centre pin, inside the bottle (or thrust bearing)

The base lifting column is internally threaded to match the jack screw.  Is held from rotating by the two key ways.  Might be easier to set up as Slider, and a motion link, for the crown wheel, one rev to thread pitch.

This would mean the current pinion Revolve would transfer to a port in the side of the bottle case, and not to our base shaft.

Might help.....

[TheCADWhisperer]

@Drewpan 

I do not see a Grounded component (or Rigid Joint with the top level Origin)?

I didn't look any further than that.

[TheCADWhisperer]

@Drewpan 

Bottom tapped holes (threads go all the way to bottom of the hole) are not liked by machinist as the chips from cutting the thread get trapped in the bottom and cause the threading tap to break.  Also, most holes (especially tiny holes like this have a 118° Angle Drill Point at the bottom.  Flat bottom holes are expensive to make (and nearly impossible for a hole this size and depth).  (So I did dig deeper.)

[TheCADWhisperer]

@Drewpan 

I do not see any clearance holes in your Crown for the fasteners?

Also keep in mind that all features have to have clearance for assembly.  We cannot manufacture perfect parts.

[Drewpan]

Hi

Thanks for your response.

I think part of the problem here is that the sketch was on the plane and to make it work I extruded in two directions. When I went to put the holes in I couldn't work out how to offset them to start from the top and go down so to make it work I started from the plane and reversed the direction and went up. Should I have created a new plane where I wanted to start the holes and projected the sketch instead?

I was also lazy and didn't change the flat holes because they were so deep that the bolt/screw would never go to the bottom anyway. I should have realised that you can Tap a "flat" hole but drilling one is much more difficult.

Cannot work out how I missed the holes on the top because I put the screws through them as a joint.

I sort of gave up and hadn't finished fixing all of the tolerances because I couldn't work out how to actually join the Crown to the Base together without getting an error. When @davebYYPCU helped me get the gears working the tolerances were ok except for the Base and Base Core were not lined up and I didn't want to move anything at the time so I didn't mess up the gears.

I also realised I should have used either the US Customary System when I selected the ACME Jack Screw OR the SI Trapezoidal Jack Screw metric equivalent instead I naively mixed systems. I do know the difference as I wrote a Report on comparing both as part of my studies and it wouldn't have made a difference for this project other than being a pain to actually manufacture and slightly different performance. Since this is a drawing exercise I have not actually calculated what the design limits really are, I just made a best guess at design requirements.

Thanks for having a look. As previously mentioned, this is my first real attempt at designing a "thing" after watching and doing several of your tutorials and a handful of others (including all of the Fusion 360 documentation and many Fusion 360 learning tutorials). I am not currently working as an Design Engineer as I have only really just finished my Qualification and I am older not fresh out of school. I am trying to do all of this stuff to build a bigger portfolio of work and get experience with different software. I don't actually have anyone looking over my shoulder, I am doing it all alone from home. I basically have a head full of knowledge and no real experience.

Cheers

Andrew

[davebYYPCU]

Not sure how far you want to go with the model, sent a PM, and still looking at the new parts.  Certainly raising my eyebrow at the moment.

Might help.....