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Thinking about Berzerker
Feb. 2nd, 2008 06:44 pmLast time was a good first attempt at the trebuchet. Our biggest problem was pulldown. We did a lot of fooling around with various tackle and wasted a lot of time, eventually coming up with something vaguely workable. A couple of pulleys allowed the hank-cranked winch to be mounted out of the danger zone but still pull down. Problem is, it was needlessly complex, required some pretty good pulleys (which we did not have, we had junky pulleys and they scared me, luckily breaking without hurting anyone) and it still put someone in the danger zone for a few seconds while the pulleys were changed halfway through the pulldown (though we did put on safety ropes before getting in there).
This time I'm completely eliminating the tackle. An electric winch will be mounted at the primary pulldown position, no pulleys will be used. Since it's remote operated the winch can be directly in the danger zone without problems. At the beginning of the pull, the cable will be parallel to the beam so tension would normally be quite high, so we will prop a stick in there to divert the force to the side. I think it will have outriggers in case there is a tendency for it to rotate away from the center.
Harbor Freight had this on sale so I picked one up today. 2000 pound capacity, so it should do the trick.
OK folks, I'm just throwing bowling balls. Think of other stuff you want to throw. I should think anything up to about 30 pounds would be easy, up to 60 should be doable with less range. I suppose one good experiment would be to see how much we can throw.
I bought 300 feet of yellow "caution" tape so we can keep vehicles out of the backthrow area this year.
Also, I picked up an ignition coil to use for the shower heater ignitor at Murrays today. I think I broke the parts guy's brain; I went up and said "I need an ignition coil." "For what car?" "No car, I just need a coil. Just any old plain cylindrical ignition coil." He had no idea how to find an ignition coil unless I gave him a make and model. So I said "OK, fine... uh, 1973 Chevy Suburban." There were about a dozen, two of which were in stock, one of which was $20, so that's my choice. A quick check here shows that ignition coil fits about 1000 models, probably anything with a spark plug and a distributor made at least up through 1980.
I probably could have gotten one for $5 from a junkyard, but it would have taken an hour to save $15, and I probably would have gotten my jacket pretty dirty. I just need to figure out whether I actually need to use a ballast resistor for my application (it is stamped "external resistor required").
The other major part, a 10-amp NPN driver transistor, was liberated from an old 250 watt AT power supply last night while watching Good Eats. I was hoping for an N-channel MOSFET, but whatever. A 555 driver and I should be good to go. I guess it should be well isolated and waterproofed (though the part in the shower will be 12v only, the ignition part will be right on the burner).
This time I'm completely eliminating the tackle. An electric winch will be mounted at the primary pulldown position, no pulleys will be used. Since it's remote operated the winch can be directly in the danger zone without problems. At the beginning of the pull, the cable will be parallel to the beam so tension would normally be quite high, so we will prop a stick in there to divert the force to the side. I think it will have outriggers in case there is a tendency for it to rotate away from the center.
Harbor Freight had this on sale so I picked one up today. 2000 pound capacity, so it should do the trick.
OK folks, I'm just throwing bowling balls. Think of other stuff you want to throw. I should think anything up to about 30 pounds would be easy, up to 60 should be doable with less range. I suppose one good experiment would be to see how much we can throw.
I bought 300 feet of yellow "caution" tape so we can keep vehicles out of the backthrow area this year.
Also, I picked up an ignition coil to use for the shower heater ignitor at Murrays today. I think I broke the parts guy's brain; I went up and said "I need an ignition coil." "For what car?" "No car, I just need a coil. Just any old plain cylindrical ignition coil." He had no idea how to find an ignition coil unless I gave him a make and model. So I said "OK, fine... uh, 1973 Chevy Suburban." There were about a dozen, two of which were in stock, one of which was $20, so that's my choice. A quick check here shows that ignition coil fits about 1000 models, probably anything with a spark plug and a distributor made at least up through 1980.
I probably could have gotten one for $5 from a junkyard, but it would have taken an hour to save $15, and I probably would have gotten my jacket pretty dirty. I just need to figure out whether I actually need to use a ballast resistor for my application (it is stamped "external resistor required").
The other major part, a 10-amp NPN driver transistor, was liberated from an old 250 watt AT power supply last night while watching Good Eats. I was hoping for an N-channel MOSFET, but whatever. A 555 driver and I should be good to go. I guess it should be well isolated and waterproofed (though the part in the shower will be 12v only, the ignition part will be right on the burner).
