How to make telescoping RHS vertical steel?

[gregh]

How would one actually make a vertically extendable/telescoping using a winder? So this might be say a vertical piece of 50x50 RHS for the bottom section, and then a smaller piece that fits within this that would telescope up to be higher? Specifically:

a) how to get the inner RHS running smoothly within the 50x50 (e.g. buying skate board bears and bolt them on the inner RHS piece to use?)

b) ideas for the extension mechanism? (e.g. just stainless steel wire with pully/winder is one way)​

Here's an example. I definitely do NOT want something that large (but it gives the idea). Wonder how they get the telescoping pieces to run smoothly up and down?

 

[angellonewolf]

plastic inserts greased ?

the nearer the top the more it will tend to lean over making it harder to make it go up ?

 

[gregh]

I think in my case the force will be not perfectly down, so I was hoping to avoid plastic inserts & trying to work out how to somehow put some runners/bearing/other into the design...

 

[Rig Pig]

plastic inserts greased ?

the nearer the top the more it will tend to lean over making it harder to make it go up ?

That's what's fitted into Hiab telescopic booms, glide pads.

 

[gregh]

ok - maybe I need to look at these again then, I kind of just assumed with a bit of sideways force they might not be too good - would be a lot easier than trying to setup runners I guess

 

[gregh]

so this is what you're talking about I guess right: https://hubproducts.com/collections/size-guide

 

[Welderpaul]

We have got a Roustabout, same as the photo - there are nylon strips/inserts bolted in between RHS sections - they don't touch each other.

 

[Shox Dr]

As others have said, you need some sort of packer/glide as the ERW process leaves a ridge in the middle of one side [inside]

 

[gregh]

ok - thanks guys

 

[Anguz]

dirty way is a spacer at the top from plastice, and a bit of studding running corner to corner at 45 degrees inside the larger section
used to make crank up antenna masts this way

 

[Gareth J]

Some stuff fits inside one another pretty well without bushings. And some tube slides quite nicely inside box. Worth asking a fabricator, the sizes I've messed around with are smaller than 50x50.

Depends on how smooth you really need it, how much you will use it and how much load it takes.