Release under tension

A good martini will help release the tension.

There was such a device in Mythbusters episode, where they dropped a lift (elevator) in a similar setup.. Some ready-made device that drops a heavy load.. Elevator of death was the name of episode, I think..

Maybe replace the forklift's cylinder with a cylinder that has very large ports on the "exhaust side" and install a solenoid or air powered "dump valve" to bypass the regular return track of the air/fluid?

Dad made something similar 50 years ago or so. It was a hook mounted on a big iron hoop to which we attached the winch truck cable. Imagine a figure eight with the bottom hole cut open to the side. The open part of the hook received a clevis tying the chain around a levee roller spool, about 2 tons of concrete. At the top of the closed part of the hook, he welded a 3-4 ft. rod of 1" bar at a slight angle off vertical. A trip line was tied to that. The leverage was enough that it was relatively easy to rotate the hook so the open part was down and the clevis slipped out, dropping the spool.

Actually, it didn't work worth a damn, because the first thing he tried it on was an old International Travelall. Dropped it smack in the middle of the roof. It did just like stomping in the middle of a soda can so it sticks to your shoe, something we did as kids. That damned car wrapped around the spool and we played hell getting it off. We hooked up to the spool without the trip hook and picked up the whole car, spool and all. It took a lot of work with cutting torches and pry bars to get that car off the spool. Dropping it on the ends might have worked better.

I doubt OSHA would approve.

Pete Keillor

Sounds pretty dangerous for the forklift and slow.

My suggestion would be to make a shackle type setup with a hydraulically operated hardened pin. Connect the hydraulic cylinder operating the pin with a set of 1/4" twin hydraulic hoses to a control valve you can clamp in a convenient place on the forklift and connect to the forklift hydraulics with some quick connects. This gives you a 100% drop, not just fast lowering, you don't have the whole forklift mast crashing down potentially damaging the forklift and you get to install some handy auxiliary hydraulic ports on the forklift.

Maybe this is where Mythbusters got them:

There are good reasons this is generally done with a hydraulic ram, rather than by dropping things. A hydraulic ram does not bounce...and 3 tons bouncing tends to damage things other than what you are trying to crush.

On 10/9/2012 1:42 PM, Ignoramus22161 wrote: ...

...

OK, Iggy, time to find that electromagnet crane that's on the auction block... :) (Every scrap dealer needs one, anyway...)

It would have to be something that hangs on the forks. Not something that is plumbed into a forklift.

Yes, that's exactly what I said. You have a forklift lifting beam, do you not? All you need is a shackle setup to hang from that to hold the load. Something like a couple side plates of 1/2" steel with a top cross pin to hang from and a hydraulic cylinder on the side controlling a lower cross pin that goes through another steel plate that has a bottom hole for a regular shackle your load hangs from. Pull the pin with the hydraulics from the safety of the forklift and the load drops while the forklift mast stays put. Lower down safely, refit the hang plate, set the lock pin and repeat. Just a homemade version of the stunt shackles that have been linked. Those have hydraulic and pneumatic activation options as well. Perhaps find a good diagram of one of those and clone it more fully.

How do you get the tension back?

Christopher A. Young Learn more about Jesus

A good martini will help release the tension.

Tilt fork forklift. Just tip the forks to dump the weight. Or a hydraulic cyl to pull the pin out of a clevis on the cable holding the weight.

Ig, search for "Drop Test Clamp"

MikeB

Debate religion and/or guns.

First question to pop into mind: How thick is your floor, Ig? ;)

Use pulleys and lift the weight by pressing down with the forks, set a trip, then back up. Drop the weight when you trigger the release.

Wouldn't a nice plasma cutter work better and be more usable?

Yep, great description.

How high will this two/three ton weight be when you release it? I'm thinking that the sudden release will cause the carriage to catapult upwards possibly causing damage to aux hoses, maybe chain sheaves or even the chains themselvs. Is this the same forklift that had the worn works a while back?

jeff

Forklifts were never designed for this sort of dynamic loading and unloading.

You will destroy it inside of a month..and probably within weeks

Shrug

Gunner

"The best government is a benevolent tyranny tempered by an occasional assassination." --Voltaire

Google "3 ring release". If you don't mind doing some sewing you can DIY i t, it's cheap, scales to just about any size, and if the rings are sized ri ght it's dead reliable.

For another pennytech option, sounds like you have access to a good supply of scrap vehicles--use a truck axle, wheel, and brake (make sure that the a xle is rated for the load you're dropping). Secure the axle to your lift, rig hydraulics to apply the brake, wrap your lift cable around the wheel, h ook your load to the cable (or strap) set the brake, lift the whole shebang , and release the brake (make sure you have enough hose on the release valv e to get to a safe distance).