how to attach high-stress fittings

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
User avatar
FishBoy
Corporal
Corporal
Posts: 575
Joined: Tue May 27, 2008 5:51 am

Sun Mar 22, 2009 6:23 pm

I want to attach a fitting to the 3/16" steel (Al?) rigid tubing which is the output on my fridge compressor so that it will have a 1/4" threaded end. It will most likely be used up to around 500 psi and I am not sure as to the best way to attach the fitting.

Ideas-

1. Score the tubing and JB-Weld the fitting on; I do not how strong JB-Weld actually is.

2. Weld it, pretty straightforward.

3. [Submit your possibly better suggestion here]
"You polish a turd, it's still a turd"

Remember DYI!!!
User avatar
jook13
Specialist 4
Specialist 4
Posts: 434
Joined: Mon Jan 21, 2008 10:39 pm
Location: Prescott Arizona

Sun Mar 22, 2009 7:21 pm

Man, my fridge had 3/16 or 1/8 copper output, which 1/4 inch copper just so conveniently fit nicley over, so I sodered it.
JB Weld (or other appropriate epoxy, I like marine epoxy) would work fine, just make sure to clean and roughen up the surfaces well and give it 24 hours to set up.
I like to play blackjack. I'm not addicted to gambling, I'm addicted to sitting in a semi-circle.
User avatar
psycix
Sergeant Major 4
Sergeant Major 4
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands

Donating Members

Sun Mar 22, 2009 7:21 pm

I used a compression fitting.
But instead of the metal ring, a piece of rubber bike pump hose.
Holds 30 bar without any problems when tightened down firmly.

I believe you can use a 1/4" threaded fitting with an endcap, but then with an hole drilled through the endcap.
Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
Gippeto
First Sergeant 3
First Sergeant 3
Venezuela
Posts: 2503
Joined: Sat Jan 19, 2008 10:14 am
Location: Soon to be socialist shit hole.
Has thanked: 2 times
Been thanked: 17 times

Donating Members

Sun Mar 22, 2009 9:50 pm

I'll second the recommendation for a compression fitting.

But;

Why would you replace the ferrule (olive to some) with a piece of rubber?

Compression fittings were designed to work with a ferrule, and they do. I routinely use compression fittings to thousands of psi.

Have a little faith in those engineers that were paid to design the thing.
"It could be that the purpose of your life is to serve as a warning to others" – unknown

Liberalism is a mental disorder, reality is it's cure.
User avatar
psycix
Sergeant Major 4
Sergeant Major 4
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands

Donating Members

Mon Mar 23, 2009 5:52 am

Because the ferrule only works on a perfectly round pipe with the right OD.
Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
POLAND_SPUD
Captain
Captain
Posts: 5402
Joined: Sat Oct 13, 2007 4:43 pm
Been thanked: 1 time

Mon Mar 23, 2009 10:43 am

@ psycix I agree with psycix that using rubber is a good idea..
on my fridge compressor I use a homemade compression fitting made from: two identical 1/2" male-female fitings with several rubber washers squeezed in between them...
washers had a small hole so I put the tube through the washers and then tighthened the fittings as much as I could... seems pretty simple doesn't it ?? suprisingly it has never leaked... not even at 500psi
Children are the future

unless we stop them now
User avatar
FishBoy
Corporal
Corporal
Posts: 575
Joined: Tue May 27, 2008 5:51 am

Mon Mar 23, 2009 2:53 pm

I am still unsure as to how a compression fitting works; how is it tightened?
"You polish a turd, it's still a turd"

Remember DYI!!!
jimmy101
Sergeant Major
Sergeant Major
United States of America
Posts: 3197
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Has thanked: 5 times
Been thanked: 15 times
Contact:

Mon Mar 23, 2009 3:41 pm

They are just assembled with a pair of wrenches. For one manufacturer's instructions see http://www.bulksrl.it/pdf/tube/ing/general_info_ing.pdf

Usually, compression fittings are rated to a higher pressure than is the pipe (or tube) it is designed to be used with.

IIRC, standard compression fittings for standard 1/4" copper pipe is rated to several thousand PSI.
Image
Post Reply