I am building Long Arms for my Cherokee out of 2" DOM 1/4" Wall
My Question is this.
Should I use ACME or UNF Thread on these.

I am making my lowers fixed and just a heim on the uppers to set caster, much easier and stouter this way. You really don't need to adjust both anyway unless you plan on changing ride height again, even at that if your arms are long enough it should effect your WB that greatly.

On my rear wishbone I just recycled a Rubicon Express LCA to get the flex joint and threaded adjustment.

screws (http://www.efunda.com/designstandards/screws/screws_intro.cfm)

"The Acme thread form has a stronger thread which allows for use in translational applications such as those involving moving heavy machine loads as found on machine tools. Previously square threads with parallel sides were used for the same applications. The square thread form, while strong, is harder to manufacture. It also cannot be compensated for wear unlike an Acme thread."

I didnt correctly read your question earlier today :rolleyes: .

Since the ACME can not be compensated for ware, Id imagine you would get some good vibes from it over time.

Whats your plan for ACME threads in your tube?

The ACME has a plus of strength but will be harder to work with from what Iv read.

I plan to use 2" x 3/8" wall tube - I was going to just use NC threads, but where the threaded portion threads INTO the 2.5" OD ajustment end, I was going to use a very very strong spring to conteract some of the slop and motion.

Stokjeep,

you may want to re-think your tube-size choice. I am going to
use 1.75" x .375" tube for my lower links. maybe for the top ones
too just because I already bought 40 feet of it.

but let me tell you, that stuff is HEAVY.......... really heavy.

I cannot imagine having to requirement of needing 2.0" of the
same thickness......

the acme thread-depth for that size of diameter would be about
1/8" deep, leaving 1/4" thickness after cutting the acme (female)
threads...

you should be able to get away with using 1.75" od, or maybe even 1 5/8" OD.... if you still need that .375 thickness....

--Just a thought..........

--Sherpa

I would personnally use fine thread for the application. You have a lot more thread surface area contact. On my longarms (Clayton's Hardparts) they are made out of fine thread with a jam nut. I have been running this setup for about 4-5 months and they have yet to losen up. The custom longarms I had before, used course threads with Jam nuts, and they would loosen every couple of weeks of being driven daily. Just an observation from somebody who has run course and fine threaded longarms. I don't know how ACME threads would react. (ie. loosen up or stay tight)

ken

I thought about using smaller ID - but in talking to several local machine shops, they have 2" taps and dies - so easy access was part of it - the other side is I plan to have a slight bend put into the lower arms, so that the breakover just behind the front tires is no worse than my current short arm setup. I also am pretty sure I would be able to jack the rig up from the middle of the 2" OD arm. I plan to have 2 small tabs near the center for a bottle jack custom top bracket can seat against. I hate running the Hi-Lift out of travel before the wheel has left the ground.

ACME is stronger, but a helluva lot more expensive.

A hefty UNF will do just fine ... with a jam nut.

cmk

I wouldn't think a machine-shop would use taps and dies for
2" work.............. they would use a lathe...............

--I plan on turning my own threads to accept the 1.250" heims
I have for my links...

and, as for strength of being to jack-up your rig in the middle of

the link, you could do that with 3/16" thick material.....

I tend to way-overbuild everything I have ever made from steel.

but, at some point you need to study, "exactly how railroad-
engine proof" do I need to make this stuff.............

--Sherpa

still overbuilding....... just with a bit of guilt sometimes...

1.75x.375" Tubing, 3/4 shank heims. Both bent, the heims bent on the shanks, you can see in this pic. The bar got tweaked but i straightened it out.

Originally posted by CJ Lagos
1.75x.375" Tubing, 3/4 shank heims. Both bent, the heims bent on the shanks, you can see in this pic. The bar got tweaked but i straightened it out.

CJ, does that mean that you no longer recommend the small rod ends?

Originally posted by CJ Lagos
1.75x.375" Tubing, 3/4 shank heims. Both bent, the heims bent on the shanks, you can see in this pic. The bar got tweaked but i straightened it out.

All that beef and you used those small ends :confused: You getting some of those huge Poly Performance boogers now :D

Originally posted by CJ Lagos
1.75x.375" Tubing, 3/4 shank heims. Both bent, the heims bent on the shanks, you can see in this pic. The bar got tweaked but i straightened it out.

When you put your links that close to the axle center line there is alot more leverage on them.

I can't fault the heims. I was trying to get the back of the jeep up a steep ledge. The suspension would load up and the jeep would bounce up and then would land back down on that one control arm...I did that several times. I can't fault them for not holding up to that.

Look at how gouged and beat up the powdercoating on that arm is. These aren't "small heims" in my book.

CJ