Fast gun valve on time

I've been running an experiment on how long the valve needs to stay open for a reliable shot. As discussed in other threads, if the valve is closed as soon as possible, less gas would be used allowing smaller bottles or more margin in your CO2. The results of the experiment were interesting. I had figured that a time of 0.1 seconds or less would work, but I was surprised that it fired with an on time as low as 0.043 seconds. At this low time, there was a slight hesitation (with a moderate tweak) before the gun would fire, so I don't consider it an optimum time. I increased the time to 0.054 seconds and it fired reliably. I upped the on time to 0.065 seconds to give some additional margin and I'll get some operational testing done this weekend at our battle.
Test setup:
regulator set to 140 PSI
1/8 supply line, 1/16" line between valve and gun
Clippard MME-2PDS 12 volt solenoid
3S Lipo battery, 11.1 volts
Standard 50 round gun with coil magazine and 4" barrel
Adjustable firing board, on time selectable between 0 and 0.511 seconds, in 0.001 second intervals

 

Sounds reasonable to me, that is on the same order of magnitude that I saw doing a very similar test when I was building my gun testing setup.

 

The test started with a full magazine and proceeded to empty. I really didn't noice any difference as the magazine was emptied. I suspect if I dialed in the absolute lowest time when the magazine was full, that there might be some difference as the magazine empied. Last nights tests were quick and dirty to make sure it would work for this weekend. I'll run some more tests later.
In addition to the time needed to fill the volume of the gun, you need to account for the solenoid response time. Clippard just states the Maximatic time as "less than 20 milliseconds" and other Clippard solenoids have from 5 to 10 ms response times.

 

Any data on how long the typical cannon valve is on while firing it manually?

 

I did a lot of testing on this in 2009 and had re-worked a programmable LED board to do it. The end result I discovered is that fast(er) shooters like myself don't need timing as we fire with a cadence that requires fast release on the firing buttons and the (kip) valve kept up no problem. So for me it was a lot of labor and testing for diminished returns. I got better results by changing firing buttons than anything else and believe me my valves don't stay open longer than they need to.

When I used the older radio shack buttons that were hard to depress.. I shot slower and used more gas. The current set of buttons I can press as fast as I can humanly do it and the valves keep up.

So in the end, for me, it wasn't so much shutting off the valve as it was the 'action' of the push button. A slow shooter in my opinion, will use more gas as he takes more time in his shooting cadence.. and in that case it would help. It would be cheaper and faster to just replace the buttons on the radio. But out of 50 shots that you shave off 5ms or less airflow.. how much air are you saving for the extra cost/time/trouble?

If you use a stick then practicing and improving technique alone will speed things up and reduce gas flow.

Now my LED boards are on the shelf.. and I have been able to get 225 trigger pulls out of a 3.5oz bottle consistently. When I went to 3 guns .. it no longer mattered as I had 50 shots left over.

Bottom line - high speed switches and a very good fill on the bottle and you wont have a problem with wasting or running out of CO2.

Johnny Adams
MWCI-Region 4
SMS Baden

 

The idea is to save every little bit of gas by using the shortest dwell time as possible to get a reliable shot every trigger pull. As Mark is showing, very little solenoid open time is needed to actually fire a shot. Even if a short dwell time saves a tiny fraction of gas, those fractions add up quick.

Now apply the switch in an environment that does not use or have a fast rate of fire. Johnny hit it on the head in that the slower our rate of fire is the chance we waste more gas because we hold the button down longer. A switch like Marks will automatically close the solenoid in that situation resulting in significant gas savings.

As example, my Verite has a 3.5 oz bottle with 3 50rd cannons. In a normal fast gun battle, the ship has just enough gas to fire all 150 rounds without loosing power at the end. Now when I have used the ship in Treaty with a 2 rps rate of fire, the ship tends to get gas starved around 120 rounds with the last 30 firing weak. That is usually due to me holding the button down far longer than it needs to be held while using the button pushes as a cadence for firing 2 rounds per second.

This switch could really help out a destroyer that is trying to fire 50 rounds off a 12 gram cartridge by clipping off the solenoid open time by a fraction of a second for each shot. The tiny amount of gas saved will add up and extend the rounds fired from a 12 gram.

Mark, I have not tested the switch yet. I'm down with a nasty cold at the moment.

 

I don't think anyone has actually measured on time (aka dwell) of a solenoid when a cannon is fired. We do know that the fastest trigger guy can fire 11 rounds per second, giving a cycle time (a push on and release off the button) of 0.09 seconds. With that as an estimate and assuming half of that time the solenoid is on would give around 0.045 seconds of solenoid on time. Based on Marks testing above, that is pretty close to the limit for a reliable firing cannon.
Hmm ... just had a thought. Chris K once measured my rate of fire with a data logger. Chris, do you still have that data and does it show the on time?

 

The other option of course is to build more gas efficient guns. Most gas hog guns don't really need the power they have to poke holes in balsa, they do it more for the fear factor and BDMI.

Programming firing boards to only allow a set ROF is pretty simple, I have some that do that myself. Actually I wish fast gun would allow automatic fire with a limited ROF of say 6-8 rnd/sec, semi-auto cannons would still be allowed unlimited ROF. (Basically I'm afraid of getting old and slowing down ;-) )

I can measure ROF pretty easily, but I didn't save that data from when we were playing with it. I can't remember if it was about 50-50 or the dwell time was shorter than the recovery time. I tend to bring most of my "fancy" tech gear with me these days so chances are we can measure that again whenever we meet up. TO be sure remind me before and I'll be sure to bring it.

Oh and high ROF only helps if you're on target....

 

I ran some more experiments to see if I could quantify the response time of the direct acting MME solenoid. With the firing board at 15ms it would fire, but only once every 5-6 pulls. With it set for 18ms, it would fire every time. That's with 140psi and 11.1 volts. If I increased the voltage or decreased the pressure, I imagine that the response time would be less.
So about a 1/3 of the minimum on time is needed just to get the valve open.