....Your solution sounds quite robust. Since no people will be on the lift, I assume I can get away with a smaller motor, say around 1 - 1.5hp?
I am a little confused with the pnuematic clamp pins as I have not seen a pair. I assume when the
trap was "up" that the pins locked it in place by clamping them to something??
It was quite "robust" as it had to lift a 4x8 steel frame
deck with an actual dentists chair on it for the Dentist scene in "Little Shop..." The size of your motor has nothing to do with the number of people on it except while it is moving. If all you are moving is a bench and a small wood
deck under it, perhaps a 1/2 hp would do. The motor size is dependent on the total weight to be lifted, the distance and the time. In fact, that is how a "Horse
Power" is defined. In an effort to determine how much force early steam engines could produce, ( for pumping out mine water in the early 1700's, steam boats and locomotives were still 100 years in the future) they were compared to draft horses. Later, James
Watt determined that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute). The wheel was 12 feet in radius; therefore, the horse traveled 2.4 × 2 pi × 12 feet
in one minute.
Watt judged that the horse could pull with a force of 180 pounds. So:
power = work/time = force x distance/time = (180 ft-lbs)(2.4 x 2 pi x 12ft) / (1 minute) = 32,572 ft-lbs per min. This was rounded to an even 33,000 ft·lbf/min.
One HP will lift 33,000 pounds, one
foot in one minute.
Today we have electricity to produce precisely measured units of
power and Horsepower (HP) is the name of several units of measurement of
power. The most common definitions equal between 735.5 and 750 watts.[1] Horsepower was originally defined to compare the output of steam engines with the
power of draft horses. The
unit was widely adopted to measure the output of piston engines, turbines,
electric motors, and other machinery. The definition of the
unit varied between geographical regions. Most countries now use the SI
unit watt for measurement of
power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is only permitted as supplementary
unit. The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.
So, (now that I've bored you out of your mind) the size of your motor depends on how much, how far, how fast.
The Pneumatic "pins were actually two types, both De Staco brand. The first was a cam-over straight
line piston clamp.
Item No: TC-850 [De-Sta-Co Pneumatic Straight-Line Action Clamp, Large, 16,000 lbs. holding cap.]
Two of these raised and lowered the frame the
drop and slide door rode in. In the up position they "camed over". Like a fail safe brake or similar device, they relied on the presence of
power (air pressure) to
release. They would hold up to 16,000 pounds each, in the locked position, they would lift or push 2,000 pounds each in motion.
The locking pins that engaged when the lift was in the up position were De Staco
Item No: TC-8031 [De-Sta-Co Pneumatic Straight-Line Action Clamp, Fully Enclosed, 2,000 lbs. holding cap.]
3/4" diameter cold rolled pins were pushed through mating holes in the lift frame and the
deck frame.
The operation was controlled by a
PLC so things could only happen in a specific order. When the door frame had dropped it allowed the door to slide, when the door finished sliding the motor could lift the
deck, and so on.
If your school has a science class that works on robot wars or similar, you have the engineering available for the control. Getting the mechanical part designed might be a
bit more of a problem.
I'm afraid I do not have drawings or pictures as this was all a few years and a couple of jobs ago. There are simpler ways of engineering the
gag. The
drop and slide door has been known since Roman times and they didn't have pneumatics or motors, course if a gladiator or lion got pinched or caught, they really didn't care that much.... so I've heard?
