Suspension pivot bolt loading

Blaine, give me a hint?
Where is this joint on the car? Is it the rear lower control arms?
What are you attaching to them?
We need to know the intended load on the bolts in pounds.
Depending on where the bolt is used you need to decide what you want to fail. If the bolt doesn't shear then the control arms will bend and fail.
If you load the component to that level then you are going to not be in a very good situation.
Do you have an ejection seat with a chute?

No ejection seat yet. I havent yet found a way to cut a hole big enough for the seat yet maintain structural rigidity. This joint is obviously nowhere in the stock suspension. I have fabricated a front suspension that is fully adjustable and utilizes stock style bushings instead of heim joints. Here is a photo. The joints I am concerned with are where the clevis attaches to the bushing carrier. It should be under the same loading as the main Pantera pivots. Thanks for the response.

Blaine

Those 4 little bolts in single shear holding in the ball joint are more likely to break than your other bolts. They are not likely to break but I think I would prefer 7/16 instead of 3/8. What I would worry about more is the tabs welded to the pivots. These little tabs could break off of the pivots if they are not thick enough and the welds are not good.

The tabs are pretty hefty. They are about 3/8 thick and have been beveled before welding for proper penetration. All in all considerably more meat than the stockers. The ball joint plates are from a reputable race car manufacturer so I trust them more than my own work. However, the plates would likely get a fair bit more abuse from road driving than racing. Didnt the old GM vehicles use bolt in ball joints in single shear though? Seems like if they could handle the load of those old tanks it should be able to handle the load of my car. Not to mention if those bolts were to break the suspension would not let loose entirely. If a pivot bolt were to break all hell would break loose with it. These are the things I want to work out though before doing any competitive driving ie. Silver State.

Blaine

Sorry I'm not going to be much help but what about the shear on the hiem joint on the ball joint plate?

Well, Whatever I decide to do about the other ones I will do to that one as well. It might however be a little trickier.

If it was me, I wouldn't replace the existing with a smaller size.
The existing are metric and are larger, as I recall, then 1/2".
I would also use as strong a bolt as available.
I would question the strength of the clevis.
Your design on paper may be superior but the factory unit has the benefit of+30 years of durabilaty testing and is a know entity.
Silver State? No offense intended but I wouldn't send a kid up in a crate like that.

No disrepect intended but what problem are you trying to overcome with the new design? And why are you doing a total custom when there are proven designs already out there that you could adapt?

Are you gonna have a clearance issue with the design?

Doug, I dont intend to replace the existing ones with a smaller size. The stock bolts will stay in place. I just want to reinforce the clevis joint. While the factory unit has years of durability testing it falls short on many items that a fully adjustable unit could eliminate. You never make any advances unless you step out of the box. This unit has full camber/caster adjustment that does not back off and can also have the arm geometry changed to eliminate bumpsteer issues. The clevis joints are the same size that most aftermarket suspension companies use in their adjustable setups. As for their durability, the clevis bolts should have equal strength to a rod end which many adjustable setups use.

Jeff, This is not a total custom piece. It is a design that I adapted from Hoerr Racing Products that has proven successful on many of their road race vehicles. http://www.hrpworld.com/HRPVersion2LowerAArm.cfm?form_p..._1417&action=product http://www.hrpworld.com/HRPVersion1AdjustableUppe.cfm?f..._1409&action=product
There are no clearance issues with these as they were built off of a jig made from the factory components.

Blaine

Blaine,
Good to see some advance thinking going on,
The parts your using appear to be strong but it never hurts to over built as long as it fits.
Being a machinist it's one of the things you do!

All metals, fastners have tensil strength, how much you can pull, shear strength, how much it takes to cut and ductility, how much they will stretch before failure. Every thing is only as good as the weakest link.
All this info can be found in machinist handbooks or you can go to websites such as
McMasterCarr- they have these parts with spec's
Mark

Thanks for the info Mark. I have been searching all over the internet for shear strength and tensile strengths of all sorts of fasteners and joints with some success. I had forgotten ,entirely about those little machinist handbooks. I also have some books from school which would go over a lot of that but would not even know where to start looking for them. That McMaster Carr site is excellent. It looks like I will need to add some beef to those pivots. After some calculations it looks like the 3/8 shoulder bolts will handle a shear of 9,277 lbs where as the 1/2 Grade 5 bolts that Jack Deryke reccomends for the main pivots will handle a shear of 14,730 lbs.

Blaine