How to pump up a large cannon in the field?

[jmccalip]

Hey, Technician1002.


I was just at Walmart, and they have that tiny pancake compressor for $52. It's so TINY.

The power meter does record peak, but not very well. Half of the time it's too slow to pick up the 1-2 second surge. It did say my 33 gallon 6HP compressor ran 15 amps constant and 18 amps start(I think the meter was either maxed out, or too slow).

[iknowmy3tables]

you even if you can invert that much current you risk burning out something like your car battery, I read up on the reviews for the tsunami and people warned that the car battery heats up a lot during use just imagine when you hook up any thing larger than that.

you might wanna try checking out your local pawn shop for some gas compressors you should find something $250 or under and you can use it for other compressor purposes

[jmccalip]

you even if you can invert that much current you risk burning out something like your car battery, I read up on the reviews for the tsunami and people warned that the car battery heats up a lot during use just imagine when you hook up any thing larger than that.

you might wanna try checking out your local pawn shop for some gas compressors you should find something $250 or under and you can use it for other compressor purposes

I am not running my compressor off an inverter.


Pawn shops? Not likely. I just stopped by EZ pawn today, and they had some nice 2HP twin tank 4 gallon compressors, but they wanted $219-250! $120 for a Porter Cable Pancake. Some of their stuff like battery chargers, I could get CHEAPER at Walmart.

[Technician1002]

Hey, Technician1002.


I was just at Walmart, and they have that tiny pancake compressor for $52. It's so TINY.

The power meter does record peak, but not very well. Half of the time it's too slow to pick up the 1-2 second surge. It did say my 33 gallon 6HP compressor ran 15 amps constant and 18 amps start(I think the meter was either maxed out, or too slow).

It is tiny. It is 1 a 1 gallon tank, the same volume as a milk jug. I am looking at the 3 gallon 1/3 HP unit at Harbor Freight someone pointed out to me.

Is that compressor 240 Volt? The current is fantastic for a 120 volt 6 HP. unit.

Bummer the power meter doesn't record the peaks. I may have to use a current transformer and the O Scope to see it.

you even if you can invert that much current you risk burning out something like your car battery, I read up on the reviews for the tsunami and people warned that the car battery heats up a lot during use just imagine when you hook up any thing larger than that.

The Prius has a very small 12 volt battery, much like a garden tractor. It wouldn't be used with just the battery. It would use the charging circuit. To provide the current, when parked, I'm not using the electric power steering, lights, A/C blower, power brakes air compressor (Prius has air brakes instead of vac assist), defroster, etc. The combined non driving capacity is about 1 KW which would be re-purposed for running external items. Already works and fully tested for an entire weekend power outage. Read the original posts. We are limiting the capacity of the compressor to one the car can handle. It's why I don't have a 2 KW inverter and am limiting the compressor to under 500 running watts and a 1800 starting watt surge.

I am not running my compressor off an inverter.

It's funny how people think nothing of using a 12 volt compressor of the same size won't use a 120 volt compressor. It's the same power draw.

I agree with you on the pawn shops. Many are no bargain and often marginal condition stuff is left and not claimed. Two words.. NO WARRANTY.

[jmccalip]

The compressor is 120v.

The meter kinda reads peaks, I don't know what to make of it. I tested the 4 gallon compressor again(at 0PSI this time), and it peaked at 10Amps then quickly settled at 6amps, and then gradually rose as the pressure built up.

I could put up a short video of what it shows when I start up both compressors.

[Technician1002]

The compressor is 120v.

The meter kinda reads peaks, I don't know what to make of it. I tested the 4 gallon compressor again(at 0PSI this time), and it peaked at 10Amps then quickly settled at 6amps, and then gradually rose as the pressure built up.

I could put up a short video of what it shows when I start up both compressors.

It is not showing the peak due to averaging. Notice how long the lights dim when it starts. May need a scope or Dranetz power analyzer to capture the surge.

http://www.drillspot.com/products/42520 ... Multimeter
They are not cheap.

I'll grab my scope to record the start current trace of a small fridge sometime next week.
The start current on capacitor start induction motors is several times the run current.

Good info is here in an easy to understand format.
http://www.faqs.org/faqs/woodworking/motors/

Starting current can be as much as ten times rated motor current.
This is usually not a problem for the circuit breaker feeding the
motor, because modern circuit breakers are typically rated to trip
instantaneously at about ten times breaker nameplate rating. For
currents less than the instantaneous value, the breaker trips due
to internal heater elements which mimic the heatup characteristics
of the wiring the breaker is supposed to protect. Since starting
currents last only a second or two (unless the motor is jammed),
motors usually will not trip circuit breakers on starting current if
the breaker is rated at higher current than the motor nameplate
current. This may not be true if you start the motor on a circuit
which is already loaded close to rating.

***Update***
I have picked up the 1/3 HP 2 EDIT 3 gallon compressor from Harbor Freight and did extensive testing this weekend. It works great. It is this one that was on sale for $59.95.
http://www.harborfreight.com/cpi/ctaf/D ... mber=97080

It has no problems re starting on the inverter at the cut in pressure. The delivery is just enough to keep up with the reload cycle of the marshmallow cannon. We had a ball with the 3 foot tennis ball barrel and emptied a bag of tennis balls out in the field in no time.

The large cannon was another story as the chamber is about 3 gallons and the compressor is only 2 gallon. Tag said 2 gallon, compressor clearly marked 3 gallon An initial fill to 40 PSI is quick, but then the compressor runs for a long time to bring up both the compressor and cannon's combined volume to 70-80 PSI. The wait isn't too bad, but the compressor runs constantly and we wait for the pressure to build on each shot. It is about as fast or faster than hand pumping it. It is well worth the money for the field launching.

Edit, after a weekend of shooting, here is the field power setup.
1 Prius
1 Trunk Mounted 1KW inverter
1 2 (3) gallon compressor 1/3 HP
1 Air Cannon
1 Light for night operations

Compressor takes 3 minutes to reach 100 PSI from empty. Pressure drops to 40 PSI on initial cannon fill and takes another 3 minutes to reach 70 PSI for a 3 minute cycle time for 60-70 PSI shots. Longer for higher pressure.

The marshmallow cannon is better. Compressor takes same 3 minutes to 100 PSI, but only drops to 80 on filling the marshmallow cannon. It's almost back to 100 and shut off by the time the next shot is ready for pretty much continuous shots. Did a Tennis Ball cycle of a dozen tennis balls with the 36 inch barrel and the compressor kept up, but didn't cycle off. The inverter and compressor held up well.

It is a little slow for the big cannon, but much better than the hand pump where most people petered out at 60 PSI or less. It was consistent at higher pressure and faster.


Compressor did not come with a hose. I just used the one I had on my hand pump seen elsewhere.