I think your math is off (or mine).
A 4' equilateral triangle has a base of 4', and a height of 2 sqrt 3. bh/2 is 4 sq rt 3 is 6.9 sq ft not 24. But, I still get 430 pounds per foot of thickness.
How much weight can those tripods that they use to lower people into caves hold up? Put skis on the feet, and you could ratchet the block up and then pull it forward with the truck on the skis. Then the truck isn't subjected to any torsional force.
Here's one that can lift 1600 pounds just as an example:
Okay, probably a dumb question (no need to agree with my opinion though), but where is the 12 volt winch getting its power from? A motor/generator on the bed of the truck? A motor/generator on the ice to the side of the truck? I'm sure it can't power itself.
Unless your car has a hand crank to start it, there is a 12V battery in it.
Hi John!
In Rigid Hitch's Catalogue the biggest, baddest Class 5 reciever hitch is rated for a Max. of 15,000 tow weight and a Max. of 1500 tongue weight in a 2.5" square reciever tube, not 2". But I agree the torsional concerns, when the block sways to the side to side, (the trucks bumper should keep it from swaying too much front to back) might be real hard on the vehicles framework and the bracketing on the hitch itself.
I'm wondering if a, "tripod on skis" (not attached to either the truck or the block) might be a better idea, where a line goes over the top of the tripod attaching to the screws, and back to the hitch, as the "test driver" :-\ gives it the gas, would the block not start to rise the same way we 4-5 guys pulled it last weekend, ( I mean it couldn't of pulled too hard, one of the guys was Dave Torry, after all, :-\) once clear or close to clear of the hole would the whole rig not go forward, either pushed as the block hits the "tripod on skis" or the whole rig, block and tripod starts to move forward from the pull of the truck. Go ahead everyone and take shots,,,,, ( I think that would be something,,,, new and different) at my idea of removing an ice block while I enjoy the 89 degrees here in this open ocean view bar in the Carib. I actually tried it with a piece of fishing line tied around my bottle of Guiness hung over the edge of the bar, with my passport as the tripod, and my left hand as the truck,,,, and the passport buckled, so I drank the rest of the Guiness ( to lighten the block) and tried it again, and damn, the passport buckled again, so I took three empty Guiness bottles taped (with a left over roll of 33 electrical tape from my pocket) together as the tripod and it worked DANDY! I was pretty excited and even showed the bartender how cool it worked,,,,,, and all he said was, "Terry,,,,,ahhhh, thats all for you".
THANKS MATT! I didn't know car batteries were 12V :
LOL!!! [URL=http://www.smileyvault.com/][/URL]
The drunken Terry way might have a toppling problem. With the truck pulling forward from the winch point, it might pull it over instead of forward if there is too much friction on the skis. It would be safer to winch it up and then pull the skis forward with an attachment point to the truck near the ground.
A while ago I thought of using a 10' high tri-pod with chains across the bottom to keep the legs from spreading and spiked feet to anchor the feet to the ice. A come-a-long would hoist the block straight up about 3' high. Then a static line from the top of the tripod to the ball hitch on a truck would topple (on purpose) the tripod toward the truck. As the tripod is toppling, the radius of this swing would pivot on two of the three legs, lifting the block slightly and then landing it on the surface of the ice next to the hole. A loop around the block could be used to drag it onto the snow to keep it from freezing down. Simple machines are sometimes better than complex ones.
I haven't done any calcs on the 2" tube yet. I would guess the tension on both straps together would be half or a little less than half of the intended load. +or- 1/4 of the intended load on each of the ratchet straps. Looking at it now it does look a little weak on the main mast just below the bottom of the 45 degree brace. Making the brace longer so that the bottom of it makes contact right at the receiver would take care of this weak spot, but it would make me need to lengthen the top 2'-3" boom to about 3' long to clear the ice block which complicates things... The shorter lever in this case is better I think.
I could add an eye under the end of the boom tip that would make using a snatch block easy. This would double the capacity of the winch (but would not do anything for the capacity of the structure).
I used this snatch block theory on the elevator in my barn. It is a 12' wide by 8' deep flatbed elevator that I use to pull snowmobiles to the second floor. I use a 4000 pound capacity Warn 120 volt winch and have a snatch block to "double" the capacity/safety factor. It is slow but it lifts two Polaris 500's (at the same time) 13' from one floor to the other in 2 1/2 minutes.
For all of you Elevator inspectors out there it is not really an elevator. I call it "a vertical reciprocating conveyor".
I re-drew the ice removal device. It now has a screw type hitch jack to give it adjustability and to reduce rotational torque. Also I drew in two ice screws at 18" on center. I lengthened the diagonal brace and added two struts to the brace. I eliminated the option of cutting the block into thirds as I am fairly confident that this will hoist the 1500 pound block out of the hole and precicely set this same block in the same hole. Here are the newest drawings on the contraption: