Bolt sizing - Upright bottom balljoints

[Sausage Sandwich]

Hi Guys,

What size bolts do you guys use for your bottom balljoints on uprights?

Our uprights are probably going to be single shear 3/8th high tensile bolts, going through a 3/4 rose joint with an ali sleeve.

Just wanted to check this is sane!

http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

Will obviously be using high tensile bolts..

Regards,
Sausage.

[Jersey Tom]

Why single shear?

[Rob.C]

we have used 1/4 inch unf bolts through rose joints in double shear for as long as i can remember!!

why single shear?? it cant be that hard to put them in double!

[Sausage Sandwich]

We've been given some upright castings that are single shear...

No offence like, but there is a bit of an anal "single shear is the devil" theme that comes across on this site. Seems a bit over the top!

http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Chris Clarke]

We've ran 3/8" bolts in single shear on the lower outboard points for about the past 5 years without a problem.

We also had cast aluminum uprights, but put a steel insert in them to prevent ovalizing of the hole, which had happened in some old uprights after lots of use.

[Denny Trimble]

The Last Time We Talked About This... (http://fsae.com/eve/forums/a/tpc/f/125607348/m/87310573911/p/1)

Single shear is OK, perhaps better than double shear, if you're running your LBJ bolt in a vertical orientation like most teams do. Do the FEA yourself and look at stiffness vs. weight, and make your own decision.

Threading a bolt into an upright for your LBJ connection is dumb, the threads are in bending and the joint is constantly being convinced to loosen itself (high loads in changing directions plus turning movements).

You should have a welded stud protruding from the upright if you're going to do single shear there. This usually means steel uprights. But again, it was all discussed on four pages before. Check it out.

[Sausage Sandwich]

Thanks Chris. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Sausage Sandwich]

and Denny. Bolts will be lockwired or lock nutted to prevent loosening.

Will read those 4 pages!

[Kyle Jeffries]

Safety Wire can break...and when wheels come off they hurt. Ask the girl from Ryerson.

[Z]

Re: Single-shear vs double-shear.

As Angry Joe said on those last four pages "Rumour has it a few teams mount their wheels in single shear".

And it seems that every animal I've ever seen has its arms, legs, and head, mounted in single-shear. And all the branches on all the trees. Has nature really stuffed-up big time???!!! http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

[Matt Gignac]

But then again limbs dislocate like it's nobody's business. And they're more like ball joints or spherical bearings when you think about it anyways.

I think I'd be worried if I could crack my a-arm pivots like I can crack my fingers... plus my fingers are kinda crooked, they'd make lousy two-force members.

Matt Gignac
McGill Racing Team

[Z]

I wonder if Nature took an engineering course, would it build a tree as a proper fully-triangulated space-frame structure, instead of that ridiculous cantilevered-beams-in-bending, single-shear-everything arrangement it uses now??? http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

[jack]

Originally posted by Sausage Sandwich:
and Denny. Bolts will be lockwired or lock nutted to prevent loosening.

Will read those 4 pages!

i think you missed to the point denny was getting at. use a stud and nylock to avoid the small gaps between the threads creating a bending moment.

Z,
i think nature was going for ease and speed of manufacturing http://fsae.com/groupee_common/emoticons/icon_wink.gif

[Akos]

Returing to the original question. 3/8" bolt definately won't break.

On the FSAE cars I built we used to run 5/16" bolts for the lower a-arms in single shear. These hold up as long as you don't load the thread in bending (the shank of the bolt has to go far enough into the upright to prevent this).

3/4" spehrical is a bit oversized, you are not building a tractor here. Use the same size as your bolt, and just make up some misaligment spacers. I hope this is not a rod-end you are putting there.

Cheers

[Frank]

depends on the life you want from the bearing too

lots of people use the 5/16 sphericals outboard...

and 1/4 rod ends inboard (heat treated of coarse)