You were all wrong, hopped up a rock, spun hard right into a tree, hooked the tree between the body and the tire and worked myself loose, look what gave...... BTW it was not the bolt....

http://www.tpijeep.com/carnage_006.jpg

http://www.tpijeep.com/carnage_007.jpg

Notice the 3/4" thick steering arm twisted on both ends... The bolt is just fine and that is the cheap grade 8 with the substandard double shear..

Now I have to add to some beef to the arms.... and probably do the shear points right....

I can't say I told you so, cause I didn't, but I really don't like the elevation of the drag link. Causes a lot of leverage on that piece as you found out. I would probably do a "Crash" type setup now with a strong tab welded to the tie rod a few inches from the end for the drag link to attach to. That is if you are set on using that type of arm.

Bummer, aren't you glad you didn't use 7/8" bolts :P

WOW:eek: . I sure didn't see that coming!!! now whaddya gonna try????

Seems to me leverage is a multiplied factor. How about running the tie rod on the bottom and the drag link on top? You'd think that the tie-rod would act as a steady, not allowing the arm to bend. If it won't fit, bend the steering arm up where it leaves the knuckle and straighten it back out where you desire to mount the heims.

Originally posted by MR4WD
Seems to me leverage is a multiplied factor. How about running the tie rod on the bottom and the drag link on top? You'd think that the tie-rod would act as a steady, not allowing the arm to bend. If it won't fit, bend the steering arm up where it leaves the knuckle and straighten it back out where you desire to mount the heims.
I agree. I think that would take some strain off the plate. Downfall would be the lower claerence issue of the tierod. but you have to lose something to gain something.

Originally posted by TEAM X-TREME

I agree. I think that would take some strain off the plate. Downfall would be the lower claerence issue of the tierod. but you have to lose something to gain something.

whew!! Listen to the two engineer's go.......

Obviously the bolt is not the weak link in the system, the steering arm is.

Moving the tie rod below the axle would barely make any change in the moment (torque) on the steering arm, but distribute the shear load on the bolt to two locations instead of one. If you wanted to reduce stress on the bolt then moving the tie rod would help. The fix for this problem is to get the drag link closer to the steering arm.

If you look at the picture below, there are some real basic free body diagrams and static analysis.

http://www.foleydevelopments.com/IM000386.jpg

The top figure is the forces on the bolt. When you make a steering input, you are pushing the drag link with enough force to move both tires. The tie rod is pulling back with enough force to move the driver's tire. The shear stress between these two points is the max that the bolt will see.

The second figure is the moments on the existing steering arm.

D is the moment from the drag link. It is a muliplication of the force on the drag link the the distance from the center of the steering arm to the center of the top hiem, or about 3.5" by the look of it (distance Y in the top figure). E is the moment from the tie rod. It is the force on the tie rod muliplied by the distance from the center or the arm to the center of its' heim, or about 1.25" (X in the top fig). F is the internal moment on the steering arm.

Using some basic numbers lets say the force on the drag link is 2000lbs, and the force on the tie rod is 1000lbs. The moment from the drag link is gonna be 7000 in-lbs, and the moment from the tie rod is gonna be 1250 in-lbs. This makes the internal moment on the steering arm 5750 in-lbs. If you stacked the two heims directly on top of each other, the 3.5" of bolt would become about 1.75" or so. This would cut the 7000 in-lb moment from the drag link down to 3500 in lb, and reduce the moment on the steering arm to 2750 in-lb.

Now if you setup the tie rod under the steering arm, you would have the moments showin in the third figure. G would be the moment from the drag link, I would be the moment from the tie rod, and H would be the internal moment in the arm. The advantage you have here is that both heims could be mounted directly against the steering arm, making the distances they are exerting force over minimal, (X in the 4th figure) or about 1.25" each. The moment from the drag link in this case would be 1.25" * 2000 lb or 2500in-lb. The moment from the tie rod would be 1.25" * 1000 lb or 1250 in-lb. The difference is that now the moments are in the same direction (pushing on the top while pulling on the bottom) so they are added together, for an internal moment in the arm of 3750 in-lb, an increase of 1000 in-lb over just double stacking the heims without the spacer.

Now don't take any of this to mean that I think mounting rod ends in single shear is a good idea, I do not want that to be the point of this discussion, just that you need to think about how the part is loaded before you go off and tell some poor guy on here how to build it.

If your goal is to reduce stress on the arm, remove the spacer between the tie rod and drag link, and shape the arm differently. Your failure in the picture above looks like it was caused by the shape of the steering arm, and a built in stress riser in it. Check out the picture below:

http://www.foleydevelopments.com/IM000385.jpg

BTW, what material is that steering arm made out of? If it is a homemade job, and you made it from steel from your local steel yard, it is probly 1010 or 1012 hot rolled crap. You can get 1020 Cold Rolled plate from most of the "high end" steel yards (look for one where the counter guy has all his teeth), without any special ordering or anything. Stepping up from 1010 to 1020 will basically double the strength of the arm, without making any improvements in design.

If it is store bought it is probly already made out of 4140 or something, but the damage may be covered under warranty.

Darn Foley,

Thanks for the info, first time anybody spent the time to explain the stresses. I plan to use material better then plain mild steel plate and will now build the arms like the picture you drew. I also plan to make the arms out of 1" material and shape the end of the arm the same as the inside radius of a 2.5" x .250 or greater tubing, the heims will be incased inside a semi circle of this tubing and a the double shear will connect above the upper hiem. I need to leave the big spacer in there for clearance issues. It is my thinking that this will correct the downfalls. Plus having a 2" ram with a 1450psi pump pushing it tends to exert some force.

The drag link is already the top heim, all that force was applied from the lower heim, I doubt the steering box could bend that plate.

Needless to say I was shocked when I saw what happened, so regardless of what happens I think my puny little bolt will hold up....

Thanks guys.... :)

Originally posted by TPIJeep
Darn Foley,

need to leave the big spacer in there for clearance issues. It is my thinking that this will correct the downfalls. Plus having a 2" ram with a 1450psi pump pushing it tends to exert some force.

The drag link is already the top heim, all that force was applied from the lower heim, I doubt the steering box could bend that plate.


Thanks guys.... :)

I think the monday morning cobwebs had still not cleared and I mixed up tie rod and drag link, and now I am having word dyslexia and can't convince myself which is which!

When I said drag link I meant the doohicky that attaches the passenger's wheel to the steering box, and when I said tie rod I meant the thingamijig that attaches the driver's wheel to the passenger's wheel (not that axle shaft smartass, the part that connects the STEERING on the two wheels :D )