Vibration isolation mounts

[dougkeuneke]

Looking to design a vibration isolation mount for an electrical box on a piece of space hardware. Thinking of a 4 point connection using 3/8 shoulder bolts (NAS1160?) and rubber bushings (buna-n?). Box weight is approx 50 lbs with connection in primary shear. If I'm heading down the right track I need to find the bushings. Any ideas?

 

[btrueblood]

"a piece of space hardware" -for what agency or end user? What duration? Buna-N won't last long in LEO; do you care? Does the end user care if flakes of rubber and/or volatile materials (oil) are floating around inside his spacecraft, obscuring lenses, shorting exposed wires, and whatnot? What static g levels are your design requirements, and what random vibration spectrum are you trying to dampen? You can contact Lord Aerospace, they have a lot of experience designing space-rated (low outgassing, rad-hard) shock and vib isolation mounts.

 

[dougkeuneke]

The space hardware is the aft skirt of the Shuttle Solid Rocket Booster. This is an external application with debris being the only issue. I am not concerned with the loads/enviroments at this time....just looking for different ideas on mounts. Thanks for the contact...I'll check it out.

 

[WKTaylor]

DOUGKEUNEKE... btrueblood has a very important point... ignore it at your own peril.

You may be too young to remember the Challanger accident. The rubber O-rings on the booster "hardened" in the extreme cold of the January 1986 freeze and the presence of the the LOX tank. Subsequently, the damaged primary and back-up rings at one joint failed to hold pressure when the RH booster ignited... and began leaking hot-gasses immediately: ~77 seconds later the flight was "over".

Elastomer materials "stiffen" when temps fall... and "soften" as temps rise... resulting in highly variable mechanical properties... not-the-least being deformation/load and dampening characteristics... and all the other factors noted by btrueblood.

Have You looked at wire-rope springs/isolators?



Regards, Wil Taylor

 

[Heckler]

I'd like to second wktaylor & btrueblood. I remember January 28, 1986 that was my 20th birthday.

I worked a space program at a large US defense company and I remember they were extremely paranoid about using Elastomer material for any damping, shock or vib. The reason being they had a satellite that had solar array snubbers that had outgassed which prevented them from being deployed.

Here are a couple of links for Barry Controls. I've used some of their mechanical isolators for electronic equipment.

http://www.barrycontrols.com/

http://www.stopchoc.co.uk/offshore_avms.html

http://www.stopchoc.co.uk/anti_vibration_products.html

 

[HANDCALC]

DOUGKEUNEKE,

Two Sources for wire-rope isolation devices

Enindine and Aeroflex

http://www.enidine.com/Aerospace/Wiremain.html

http://www.aeroflex.com/products/datasheets-list.cfm?ProductType=Isolator Products

Ed