Mandrel sources?

[Brian Barney]

hey does anybody here know where I could get a 2 1/8" aluminum tubing? I tried turning down a 2 1/4" tube down to size, but I got way bad harmonic vibrations even with a live center and a follower support. so I ruined a $40 tube. I want aluminum because I can freeze it so that it will contract to aid in releasing of the 54mm tube. I am working on a scratch built CF rocket. I am doing a little fiberglass/carbon fiber 22mm min diameter rocket for aerocons micro hybrid... got the tubes made and am working on the nosecone mold as I speak.
Thanks.

 

[Brian Barney]

I found a place... its a ham radio place...
https://www.texastowers.com/aluminum.htm

it has 29mm, 38mm, and 54mm tubing... they have a $25 minimum order, and shipping is $25, which I guess is reasonable for extra long orders. cheaper than screwing up afew tubes trying to make one on my own....

-Brian Barney
TRA #8896 L2

 

[Stymye]

Brian,thanks for posting it

 

[GL-P]

nice, thanks for posting it

I'm gonna be doing some CF tubes also in the 24mm range. Our 29mm mandrel will be a max. of 21 inches long to reduce vibrations. The 24mm mandrel will be some turned down Delrin cuz it is pretty slippery even without mold release. (Just don't wan't to mess up a mandrel!)

 

[edwardw]

Where was your tool when you were turning down the tube? Above, below or at center?

Also, 2" Schedule 80 T-6061 Aluminum Tube can be turned down to make 54mm motors.

Edward

 

[Brian Barney]

I had the cutting tool on the centerline of the project.. my machining teacher helped me with the setup. whats the method of finding the maximum length? I have only heard the unsupported length should be no more than 3 times the diameter of the rod.
Thanks for the input.

-Brian Barney

 

[edwardw]

When I run turning operations typically I go between .002 and .005 above center. This is because sometimes the tool can deflect downward under the stress and then the work tries to jump and it chatters. Next time maybe try setting it a little high on a scrap piece and trying it out.

Edward

 

[Micromeister]

Brian:
if you can't get the Alum tube to turn try 2.25" Delrin (Black) #8576K31 about 20.79per foot.
Turns really well with standard tools. Available in 1foot sections from McMaster-Carr. Wonderful for laying up FAI type model bodies and nosecones. No release agent required just throw the harded glassed combo in the freezer for a few minutes, body pop's right off

 

[GL-P]

if you can't get the Alum tube to turn try 2.25" Delrin (Black) #8576K31 about 20.79per foot.Turns really well with standard tools. Available in 1foot sections from McMaster-Carr. Wonderful for laying up FAI type model bodies and nosecones. No release agent required just throw the harded glassed combo in the freezer for a few minutes, body pop's right off

Seriously? We found some Delrin locally. I'll be making some 24mm*2ft sections.

Time for experimentation!!!