Brand new question: Delrin bushing clearance

[parsonsj]

I'm making my own Delrin bushings for my swaybar, and I wondered if anybody had any thoughts on clearance between the bushing and the swaybar. I made it about .005", but I'm starting to think that might be too loose. It's got a grease fitting, so grease can take up some of the clearance.

Thoughts?

jp

[John Wright]

Did you make it in two halves?...I'm guessing that you did.

I don't think 5 thou is alot of play in a sway bar bushing...that is got to be better than the softer bushings that would squish a lot more than than.....and like you stated, the grease will eat up some of that clearance.

Will you be mass producing these or is this just for your personal ride?

[parsonsj]

No... just one piece. I couldn't come up with an easy way to keep the bushing from walking out out of housing, so I made 'em one piece with a shoulder. That and a shaft retainer on the sway bar will keep them where they are supposed to be.

These are custom pieces for II Much. I'm replacing the original bearings that had poor clearances and that I forgot to grease, so they had gotten real squeaky.

jp

[John Wright]

No... just one piece. I couldn't come up with an easy way to keep the bushing from walking out out of housing, so I made 'em one piece with a shoulder. That and a shaft retainer on the sway bar will keep them where they are supposed to be.



Short dowels? to keep the two halves interlocked as one piece?...just a wild thought

[CarlC]

Is the housing design such that it will crush the bushing at all? Is the diameter of the bar consistent across the load zone?

You may also want to consider putting is either a spiral or raidal bore groove to act as a grease reservoir.

[parsonsj]

The housing is a .002 interference fit with the bushing. It presses together by hand (6" vise). I did put a grease reservoir in. Spiral grooves are out of the question for my li'l workshop. :)

But you guys think .005 clearance is OK, eh?

jp

[silver69camaro]

Five would be OK since you are using grease to keep it lubed, and that will take up some slop. I'd shoot for .003 to .005.

[chicane67]

First of all... which composition of POM are we talking about ??

0.002" might be enough... and, it might not be enough. It depends on the required surface work hardness that you are looking for. I played around with some staybar frame bushings a few years ago and found that even a 0.001" change made a big difference. When it was too loose... it actually deformed the surface of the bar... and when it was within its window of happiness, both the bushing and the bar showed zero deformation. From there it was just making sure that it didnt get too hot so that creep and relaxation were not the next issue.

Here is a link that you may find helpful when selecting a product for specific mechanical properties: http://plastics.dupont.com/plastics/pdflit/americas/delrin/230323c.pdf

[parsonsj]

So here's the tech sheet from McMaster-Carr:

Material Acetal
Acetal Material Delrin
Backing Plain Back
Opaque Black
Operating Temperature Range -40° to +185° F
Performance Characteristic High Tensile Strength
Tensile Strength 10,000 psi
Impact Strength 2.3 ft.-lbs./in.
Tolerance Standard
Hardness Rockwell M: 94
UL Rating UL 94HB

I'll have a read at the link... thanks!

jp

[parsonsj]

It seems I'm using Delrin 100, 500, or 900.

Anyway, everything's put back together. Gone are the original squeaky (and rusty) bearings. The greased Delrin bushings feel awesome when actuating the sway bar by hand. The one downside is that the bushing housing alignment is crucial (the old bearings were spherical, so alignment wasn't that important). Good thing they are adjustable.

I need to re-scale the car since I was also messing with the end link lengths.

I'm looking forward to a squeak-free ride now!

jp

[parsonsj]

I just took the car for a long drive.

What a difference! The old squeak is gone, and the suspension response is so much smoother and quieter.

I should have done this a year ago.

jp

[John Wright]

What a difference! .....
I should have done this a year ago.

jp

Cool!...Sounds like a successful project!