Sizes for Nesting Tubing?

[minuteman62-64]

I'm planning a hitch mounted "T" rack for my truck. Planning on using round tubing, two sizes, so one nests/slides/rotates inside the other. Wondering what gap between the ID of the outside tubing and OD of the inside tubing I should be looking for to insure free movement without binding, yet as much stability as possible.

Any thoughts?

 

[Scott Danforth]

if you want to insure no binding, you need to have a bushing of some kind.

 

[Harritwo]

We build handrails for tooling where we use 2" Sch 80 pipe with 1-1/2" Sch 40 for the inside piece. These are made to be removable and 90% of the time we have no issues.

 

[minuteman62-64]

if you want to insure no binding, you need to have a bushing of some kind.

I have a lathe so could actually make a pretty good bushing arrangement. However, what I'd gain in rotation and stability I think I'd lose in the ability to easily telescope up and down. In any event, it would be way over-kill for the simple little device I'm contemplating.

 

[minuteman62-64]

We build handrails for tooling where we use 2" Sch 80 pipe with 1-1/2" Sch 40 for the inside piece. These are made to be removable and 90% of the time we have no issues.

That might be a good model. Any idea what the 2" Sch. 80 ID and 1-1/2" Sch. 40 OD measurements are? If not, I can probably find an on-line reference.

I took a look at a local metals supply outfit's inventory. They sell nesting square tubing - where the difference between the inner and outer nesting pieces is about 3/16". That may be a target for my application.

 

[minuteman62-64]

That might be a good model. Any idea what the 2" Sch. 80 ID and 1-1/2" Sch. 40 OD measurements are? If not, I can probably find an on-line reference.

I took a look at a local metals supply outfit's inventory. They sell nesting square tubing - where the difference between the inner and outer nesting pieces is about 3/16". That may be a target for my application.

OK, that was easy - looks like the difference between the 2" ID and 1-1/2" OD is a bit over 1/32".

 

[Scott Danforth]

I have a lathe so could actually make a pretty good bushing arrangement. However, what I'd gain in rotation and stability I think I'd lose in the ability to easily telescope up and down. In any event, it would be way over-kill for the simple little device I'm contemplating.

if your simply telescoping and could live with rattling noise. they make pre-perforated tubing in both square and round for that reason.

https://www.mcmaster.com/#square-tubing/=1drq0ny

if you plan any rotation while loaded, round its the way to go and a couple of delrin bearings makes life easy to prevent binding. if you were building a small crane, that is what I would do.