Why not?

[KevinS]

Okay.. this may be a really dumb question. but.
Why couldn't a small internal combustion engine be spun with a second one ( or electric motor) to create vacuum? just plumb to the carb manifold. what am I not considering?
I have old engines laying around and not lot of funds to put into vacuuming all the deer devastated saplings I planted.

[wdchuck]

Might work......might not......Why not do the same thing with a compressor?- that was designed to move air and would turn easier.

[markct]

Certainly could be done, altho likely not real efficient. How many taps you looking at on vac? Small elec vac pumps can be found on ebay or some guys have even used the cheap harbor freight ac vac pumps. The pump is cheap part its the releaser or zero tank that gets expensive!

[jrgagne99]

From a thermodynamics standpoint, there is no net gain in effficiency. Plus the downsides are that you need zero-vessel to do the "boiling" in. Very expensive, and how do you draw off to test? If you open a "draw-off" valve, air would just get sucked into your tank!

[325abn]

Think he is talking about vac on the trees not boiling under vac. I recently read in a 1960s maple manual about boiling in a vacuum.

[arcticmaple8]

I thought the same thing so I took carb off of a cheap 6.5hp harbor freight motor and made a adapter to pipe thread put on a vac gauge and spun it with electric motor. It didn't work that well, gauge would bounce between 5" and 10" probably because its a single cylinder. I think the problem is that a 4 stroke has a dead stroke where no valves are opening. I thought about trying a 2 stroke but now your back to oil injection which I didn't want to deal with.

[markct]

I thought the same thing so I took carb off of a cheap 6.5hp harbor freight motor and made a adapter to pipe thread put on a vac gauge and spun it with electric motor. It didn't work that well, gauge would bounce between 5" and 10" probably because its a single cylinder. I think the problem is that a 4 stroke has a dead stroke where no valves are opening. I thought about trying a 2 stroke but now your back to oil injection which I didn't want to deal with.

I think if it would work the best way would be eliminate the drivetrain and put a light spring on intake valve and a check valve in spark plug hole.

[jrgagne99]

Think he is talking about vac on the trees not boiling under vac. I recently read in a 1960s maple manual about boiling in a vacuum.

Oops, you're right.

[arcticmaple8]

I think if it would work the best way would be eliminate the drivetrain and put a light spring on intake valve and a check valve in spark plug hole.

I agree. The idea just didn't seem cost effective, your basically making an air compressor so that's the road I headed down. wdchuck is right, an air compressor is an air pump that's made to dissipate heat well. I made two for a friend who has 2 400 tap setups and so far they are working great but we'll see how it goes this season. We are using a 7.5hp 35cfm single stage compressor and running it with 3hp. Pulls 25" deadheaded and we have been getting 23-25 in the woods. Im sure its not a 35cfm pump but who knows how it compares to all these other pumps that claim high cfms on their stickers. We haven't had a hard run yet so we'll see how these pumps do when the trees really start pumping.