What do you guys think of 3/4 cm heims

jeepzilla

Well-Known Member
Joined
Dec 25, 2008
Location
Draco
I am building a budget buggy. Do not know the weight, but two people can pick the tube frame off the jack stands.
Specs:
sbc 350
sm465/np205
dana 60 front with detroit
14 bolt rear with detroit
4:56
full hydro steering
some form of air shocks 2 inch 16 or 18 not sure yet
40 inch tire
weld on beadlocks
glo diff covers
4 linked front and rear
Question: I am using 3/4 CM heims with mis-alignment spacers and 5/8 bolts.
Used 1-1/4 JJ on last buggy w 9/16 bolt.
Weak point there was the 9/16 bolt.
With the 3/4 heims and the 5/8 bolt the math seems to work.
Not going to race and can feather the throttle.
What do you guys think about the heims?
 
They will start to rattle after just a few trail rides. The rebuildable joints can be tightened up to stop this.
Edit this also seems like it will be a heavy rig to use use 3/4 stuff too.
 
That is what I am using. Here is some addtional info.
sbc350 550 pds.
sm465/np205 360pds.
dana60 518pds.
14bolt 450pds.
tires 404pds. without steelie wheel and weld on beadlocks
tubing est. @ 600pds.
_______________________

2882 pds. will finish out less than 4000pds.

Stock cj5 weighs this.


Bolt Tensile Strength (Breaking Strength - pounds)

Grade 5 Grade 8
Coarse Fine Coarse Fine

9/16 21800 24400 27300 30400
5/8 27100 30700 33900 38400

3/4 x 3/4 Heims Rated over 14 tons
 
Appears you have made up your mind to use the 3/4 heim joints and and your just looking for someone to confirm you decision.
 
Not yet, have not set axles under rig. Have not welded my first link tab. I do have all my tabs from MudPro w/5/8 holes though. I have all the .25 wall 1inch ID tubing here in the shop.
 
snappy said:
They will start to rattle after just a few trail rides. The rebuildable joints can be tightened up to stop this.
Edit this also seems like it will be a heavy rig to use use 3/4 stuff too.
Click to expand...

That is what I have heard and seen too. Seems like most people who choose to use rod ends are going with 1.25" size nowadays. Sometimes smaller ones on the upper links.
 
In reality, should you not take into consideration the tensile strength of the heims that you are running on both ends of your link. Seems to me that decreases stress and increases the actual tensile strength. Please correct me if I am wrong.
 
the problem isnt the tensile strength of the heims, it's the shear strength of the shank and bolts, on your lowers... you should be fine with a 5/8" bolt in double shear, but you will break the body or shank when you drop it on a rock...
 
The force of the links dropping off on a rock will shear the heim. That is what will be hitting or dragging across. What is the shear strength roughly 60% of tensile strength.
That is still over 8 tons of shear strength on a 2 ton buggy. If I return the the heims and get 1-1/4 and new dom, that adds another grand to the budget buggy. Heck I don't know what to do. Thanks for all the input.
 
I have broken 2 3/4" shank heims on my last buggy, sheared the shank, it weighed 4200lbs with toy axles at the time. I went with ballastic fab joints this time with 2" .250 dom for my lowers and 1 3/4" x.120 for my uppers. We are not bashing your set up at all but alot have been there done that. Stan is the man at Branik but from the sounds of what you are wanting to build, it will be ALOT heavier than what they typically build. IMO return the heims u have for lowers, keep the uppers, and order 5/8" shank joints or 7/8" or 1" shank heims.... thats my .02. If you think it adds alot now think about having to buy them twice and replace what breaks when one fails(ie bent shock etc etc).
 
Your right. Breakage can cost more than the addtional cost of the bigger heims. Thanks!
 
jeepzilla said:
The force of the links dropping off on a rock will shear the heim. That is what will be hitting or dragging across. What is the shear strength roughly 60% of tensile strength.
That is still over 8 tons of shear strength on a 2 ton buggy. If I return the the heims and get 1-1/4 and new dom, that adds another grand to the budget buggy. Heck I don't know what to do. Thanks for all the input.
Click to expand...

you will be pushing it to get under 4k with those parts...

You are right, it might be hard to put 16k of force on the lower link to shear the heim, but if you land on a pointed rock, it is easy to put that much force as a point-load on a heim joint... you haveto calculate the force of the vehicle landing on a rock at any given rate, and that will be alot higher than 4k... Also you haveto think about fatigue over time and how that joint will just get weaker everytime it bashes or drags on a rock until it finally breaks...

You should be fine with 3/4s in the uppers and they are only in tension and compression on a proper link system.

I would trade the 3/4 & lower material/bungs for cartridge joints with 5/8 hole and 1" or 1.25" shank
 
The jury has decided. 3/4 going back 1-1/4 coming for upper and lower. Thanks guys!
 
I could possibly see running 3/4 heims on the uppers of a light rig but never on the lowers regardless of the weight. With your setup I wouldn't run anything less than a 1 1/4 heim/joint.
 
1 1/4 heim/joints on all 16 ends and then just hammer it. Thanks everyone and Merry Christmas!
 
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