I have been running some rough numbers on adiabatic compression of air. Interesting. What if we have a piston that adiabatically compresses one cubic inch of air? We want that air to contain a certain amount of energy. What pressure does it take to attain 5fpe/ci? What about 6fpe/ci? And 7fpe/ci?In reality, a piston gun is transferring energy from spring, to piston, to air, to pellet in an overlapping scheme so it is not as bad as it looks. But it shows why it may be very hard to push the air efficiency of a spring gun much over 6fpe/ci. Timing of the overlap becomes critical. At 5fpe/ci, the overlap can be very sloppy and still stay within an acceptable pressure limit.I'll verify the numbers and post them later. I won't do it right away, so I hope somebody else can beat me to it.
Probably with a loss at every transfer (spring to piston, piston to air) which could explain why pcp has an advantage not as much loss, just air to pellet....
instead of running the threads under power on the lathe you can make you a removable crank that attaches to the rear of the headstock so that when you want to thread you can just attach the crank handle set your compound and select the right gears for your thread.... then you just set your halfnut andstart cranking when you get to the end of your thread you back the compound off a tad reverse crank the handle till your carriadge is back to the beginning run the coupound back in and start cranking again...... basicaly everything you would do under power but your doing it manual and you NEVER disengage your half nuts so you never loose your index with the thread your cutting..... and no need for the threading dial..super simple to make a crank too... just get you some scrap roundstock (delrin alu steel doesnt matter) drill you a hole the length of it, then turn it to just under the size of your headstock bore, then cut the pipe at a angle in the middle.. Get you another peice of scrap round square whatever you got make you a crank arm and handle then take a long bolt and bolt the whole thing together with the tube angles mated together... slide the whole thing into the bore of the headstck tighten the long bolt down and the angled ends try to slide past each other and grip the inside of the bore(Kinda like an old gooseneck on a bike would stay down into the forks) .... you now have a removable crankkinda like this except they have a collet shown attached at awellhttp://homepage.mac.com/bhagenbuch/machine/pages/spindlecrank.htmljust remember to REMOVE the crank before ou power back up!!!!!
Scotchmo,Are you going to break down and machine a few Delrin pellets? Or is there anyway that we could stop you from doing it? You have identified a nice trend.Lloyd