4 bar - how much thread to expose safely?

47convert · February 03, 2006, 12:13:57 AM

My Street rod parts supplier says you can go by this rule of thumb: the amount of thred inside the tube should be at least as much as the diameter of the threaded adjuster. So a typical 5/8" adjuster is safe with only 5/8" inside the tube. Does this sound good to you guys? My 4 links and front 4 bars are well beyond this, but my rear panhard bar is on the edge. Even though I've already powder coated this stuff, I'm thinkoing this supplier should give me a longer panhard bar. I'd like to know the opinions here?

enjenjo · February 03, 2006, 12:20:16 AM

His rule of thumb is correct. Anything beyond that is bonus.

47convert · February 03, 2006, 12:28:21 AM

Thanx Frank - Your help is always appreciated.

blksheep · February 03, 2006, 12:43:36 AM

47Vert...How bout a longer threaded shaft on the heim joint?

Thanks for the info, Frank. I also have wondered bout that.

blksheep...threaded up and shafted....in Charlotte

btrc · February 03, 2006, 06:22:39 AM

I have never gone by this but in one of my engineering classes long ago we were told 3 threads will take all the load of a bolt. I always go for at least the diameter of the bolt though. If you use a jam nut too then 1 diameter is probably OK.

Bob

C9 · February 03, 2006, 08:30:12 AM

I'll go along with the rule of thumb as well.

Somewhere along the line I read that the full strength of a bolt is attained if the threads covered are the same or in excess of bolt diameter.

IE: 1/2" bolt requires a 1/2" tall nut.

I'm thinking as well that the manufacturers realize tie rod ends may not be too far into the tie rod/drag link due to adjustment requirements and as long as tie rod ends are sufficiently large not a whole lot of threaded area need be within the tie rod/drag link.

The load on suspenion components such as tie rod ends, Heim joints and poly bushing ends is longitudinal in nature and they do not have a bending force applied to them.
Some twist is involved at times, but loading for the most part is longitudinal - or compression/tension which is a better way to say it.

Fwiw - my 32 has quite a few threads of a 3/4" OD front panhard bar exposed, but threads in the bar are longer than the diameter of the poly bushing ends threads.

As shown in the pic, 43,000 miles and still doing ok.

jaybee · February 03, 2006, 11:02:32 AM

What about tie rod ends using a split collar with clamp arrangement? Is there a rule of thumb for that?

enjenjo · February 03, 2006, 11:13:52 AM

Quote from: "jaybee"What about tie rod ends using a split collar with clamp arrangement? Is there a rule of thumb for that?

My rule of thumb there is twice the diameter. 5/8" thread, 1 1/4" in the tie rod.

PeterR · February 03, 2006, 07:04:04 PM

Quote from: "btrc"I have never gone by this but in one of my engineering classes long ago we were told 3 threads will take all the load of a bolt.
Bob

When you are I were young enough to be in class that was true. If you look at an ungraded fastener with a coarse thread the core cross section of the threaded portion can be as low as half that of the shank. Combined with the sloppy fit of an ungraded nut it is true the first three threads do just about all the work.

However when using fine-thread, high-strength fasteners with the bolt and nut made from similar material the guide of engagement thickness the same as thread diameter is a more practical approach.

If the male thread is in a softer material such as a head stud in an aluminium block, then more engagement is required to realise the full potential of the fastener.

Same situation with a split thread, and the 2:1 ratio is a good guide.