Can you make bearing pipes more rigid with pressure?

[trilect]

Might be a silly idea but I have to ask anyway. If you use gas pipe for a linear bearing surface would sealing 250 psi or so in the pipe help with pipe flex?

[ChrisJ]

I would have to say no it won't.

How about filling the pipe with an epoxy grout?

Chris

[murphy625]

To get rid of the amount of flex your talking about, whatever you put in the pipe must be a solid (non-flexible) material itself or it wont do any good for the small amount your talking about..

As the post above suggested, an epoxy might help... If your flexing over an 8 foot length or something like that, maybe you could slow it down a bit by shoving a threaded rod threw the pipe if you can find one that fits snug inside the ID of your rails.

The best solution would be a larger pipe.. But even that would depend on your machine.

Murphy

[joecnc2006]

Would'nt square steel tubing placed at a 45 deg angle instead of a round pipe yield better results than filling the pipe.

[keithorr]

Can't say as to whether square tubing is stronger than filled round pipe. When comparing a square tube and a round tube, both with the same cross section area and wall thickness; the square tube is stronger.

[ignatz]

Why not use cement to fill the pipe? The Multimachine suggested its use.

[ChrisJ]

Cement could/would ultimately crack under the vibration. The epoxy grout has a great tensile strength, compressive strength and a very good bond strength.

Chris

[2muchstuff]

Rectangular tubing would be more rigid still, stood on edge. Filling your tubing with concrete would not be adventagous due to cracking even if you used a latex fortifier. The added weight of the concrete would allow even more flexing. Epoxy and polyester resin would be too flexible to be of any use. The only real benifit of filling tubing is adding mass, making it more sound.

Putting your tubing in compression would allow for even more flexing than if you had left it alone. What you want to do is put your tubing in tension (pull). An extreme amount of pull would be needed, therefore your frame would have to be VERY rigid and oversize.

You can still use round tubing but for any long lengths I would use the 3(6) bearing arrangement (three bearings arranged 120 degrees apart with one on the top). Using an 1/8" thick angle bracket, cut and fit so that when it is screwed to the table it will just touch the bottom of the pipe. Then weld or braze it to the pipe. This creates a stand-off for the pipe that does not interfere with the bearing carriage.

[H500]

The best strength/price ratio actually comes from a round tube. It has the smallest circumference for a tube of a given strength. The circumference is where the steel is. The steel is what cost money. Of course the acutal price often depend on other factors...

[solarchimesam]

Originally Posted by trilect Might be a silly idea but I have to ask anyway. If you use gas pipe for a linear bearing surface would sealing 250 psi or so in the pipe help with pipe flex?

A fella I talked to said if you could get a section of "rebarb" and some how fill the gas pipe (rebarb inside) with epoxy or suitable compound that this rebarb would really make the pipe strong...I am going to try it myself. It will be much heavier after that by the way.

JEFF

[ChrisJ]

2muchstuff,

You mentioned that the epoxy would be flexible.

A product I had in mind was something like this:
http://www.fox-ind.com/pdfs/foxpack-1200.pdf

I believe this will cure rock hard and will not be flexible, but I could be mistakened.

Regarding the idea of putting a piece of rebar and grouting the space between. I agree. The more surface area that the epoxy grout comes in contact with, the stronger the bond and the more rigid it should become.

Chris

[Fred in NC]

Sorry to butt into this conversation, but I would like to point out that in building construction they use I beams. It is the top and bottom that make it rigid to support vertical loads.

A solid rod does not have any more resistance to bending than a tube with proportionate walls.

A central support seems to be the best solution. I would make it adjustable. It could be a piece of threaded rod and nuts.

Again, sorry to butt in. I just hope to stir some thinking.