Safe Release of Pendulum Bob

Arun jalali:

More specifics would be helpful.

What is the shape of the "pendulum bob"?

Is a crane of sufficient lifting capacity available, and you are asking only about a mechanism to release the "bob"?

By "6 mt" do you mean "6 meters"? and is that the height to ground or height to the top of the cab?

Lastly, will your mother-in-law be in the driver or passenger seat of the cab?

Pendulum bob shape :- It is flat plate 2.5m X 0.8m X 0.1 wt is abt 1.5 tonne

Pendulum arms: 2 arms , co- axial tubes for varying length wt of arms 0.7 tonne

Height of arms from ground is about 6 meters

Hoist to raise the pendulum is avbl (capacity 5 tonne )

For varying energy requirements the pendulum arms and angle has to be varied

a sudden release is essential to ensure no loss of energy in releasing the bob

At the time of front impact vehicle has no test dummies inside

Post crash a stipulated manikin ( without instrumentation ) will be used to access occupant survivability ( this manikin is simalar to Hybrid III dummy)

Electomagnetism from the mechanism attached to a purpose-designed vehicle for moving scrap metal sounds like the right sort of thing for the job - assuming the bob is made of a material that responds to magnetism.

Such a vehicle would also prove invaluable for removing the waste products from this experiment...

I am on the look out for a release mechanism, that can be manually activated by rope from a distance . optional can be hydraulic Magnet for lifting 2.5 tonne may be bit expensive ready off the shelf aggregate is desirable

On the TV show "Myth Busters" they keep using a mechanism like the one you describe to drop things. They seem to come in a variety of sizes but I don't know where they get them. Perhaps you could contact them or a local movie company and talk to their special effect/stunt department. Failing that you could devise your own mouse trap inspired mechanism. as I did years ago to allow a spring loaded fire damper to close.

Good luck,

Gordie.

Fabricate your own release. Look at design of cable operated automobile hood release. scale up to fit your application. They are a simple hook / trigger release mechanisms.

I may be missing some important point here, so my apologies up front if that is the case!

I assume that you are not dropping the weight ontop of the cab, I guess it swings in from the side and hits the cab on the front, as in a traffic accident....

If that is the case, may I suggest that a strong harness is used to hold the pendulum in place (at the top of its swing) I suspect with the arm parallel to the ground. This harness must not be attached to the Pendelum in anyway at all, just a loop of suitable material (very strong rope for example or a metal chain)that stays in place around the Pendelum and is connected to a suitable strong point wia a small length of extremely strong (and replaceable) rope. Use a flame to burn the rope, once the rope burns thru, the harness just drops away and lets the pendelum swing unencumbered at the target.

A slight refinement could be a short piece of Cordtex or similar firing cord (burns at a rate of several miles per second!) wrapped twice around the rope, with a suitable electrically fired detonator, to disintegrate the rope and free the pendelum.

In the Royal Navy, we used Cordtex and similar for many things, including cutting down trees, (two or three times around the trunk would cut down small to middle sized trees with no problem), or for warming up gun barrels before firing in Arctic conditions and springing off any ice that may have collected on the outside of the barrels. (A rubber Condom type of device was over the opening of the barrel to stop water/ice ingress, but allow us to shoot thru when needed!). The Cordtex would be fired immediately before the guns were fired. They came as a tight "net" in a size to fit different gunbarrels, with a detonator alread in position, it just needed to be plugged into a special electrical socket to fire the charge.

I know this thread is a bit old but just in case you are still looking, an American company called Eastern Rotorcraft make elctromagnetic cargo release hooks designed to drop underslung loads from helicoptors in an emergency. The release is instantaneous & all hooks have a manual release system built in. If I remember correctly they range from 1000lbs to 30 000lbs capacity.

...but "oldies" are also "goodies", so no problem for me, new info is always welcome. no matter from who or when!!!

can i get more details ( contact details) of the supplier

with kind regards

arun jalali

Arun, it seems that Eastern Rotorcraft has been bought by another company & now trades under the name of Breeze-Eastern. You can find them at http://breeze-eastern.com/, look for external cargo hooks. When I was involved in this industry I know that we sold a couple of the units to people outside the aviation business. One was a film company that needed to drop a car into a scene, the other was someone doing crash testing.

Its worth noting that whilst I was looking I found a cargo hook on eBay that had just sold for $350.

You could also look at using a Quick Release Coupling from http://www.drallim.com/pg001.asp?pid=9. Look for 'Cargo Aids', these have jaws that are designed to be released under load but would have to be operated by hand whilst standing right next to your pendulum.