SpudFiles

Has anyone ever tried this?
A qev is essentially a piston valve, and seeing how metal piston valves are such an effective alternative to a burst disk, I can't see why a qev wouldn't work.

The best part is they are already made to a high standard, so it would be an extremely good option to those who don't have access to a welder of some type.

Tell me what you think. I'm interested to see if this could be a "burst disk killer" idea. An idea to bring valved hybrids to the masses


Edit:You shouldn't even need to use a pop-off, actually. This will cause the valve to open at a higher pressure and increase overall preformance.

I suppose you intend to use a pop-off valve as the pilot?

windshrike wrote:I suppose you intend to use a pop-off valve as the pilot?

Oh, that's good. I wouldn't have thought of that

i think the rapid build up of the pressure would cause too much stress to the valve. Plus, a lot of QEV's are rated to 150 psi. In addition, a hybrid generates about 300 + psi in a few miliseconds. So you'd overpass the pressure rating by a factor of 2. However, i'm not familiar with QEV's, so i might not be a good advise.

Even a pop off valve would react too slowly i think. It would be cool if it was able to be done easily, but i doubt that it could be.
Burst discs are cool to use anyway, if i aint broke.....

CpTn_lAw wrote:i think the rapid build up of the pressure would cause too much stress to the valve. Plus, a lot of QEV's are rated to 150 psi. In addition, a hybrid generates about 300 + psi in a few miliseconds. So you'd overpass the pressure rating by a factor of 2. However, i'm not familiar with QEV's, so i might not be a good advise.

But he just needs the QEV to hold the pressurized air and fuel in until ignition. As soon as the pressure exceeds the pop-offs rating, the QEV will open, releasing the majority of the expanding gases.

The pop-off would open very quickly because of the pressure spike and the pilot would be very small.

I pondered this idea many times. I was always turned away by my fear of hybrids. Oh well.

But assuming you had a QEV that could handle the stress, and an extremely efficient pop-off to vent it, there is no reason why this shouldn't work.

I dont see why it wouldnt work. but the only QEV's i can get are diaphragm ones and im afraid it might burst the diaphragm, but if i could get my hands on a piston QEV i might try it.

All qev's are diaphram valves he is just saying it is very similar to a piston valve.

We are overlooking that if the valve misfires, you have potentially created a bomb.
I do not think this is the solution to the "Burst disk problem"

I know i shouldn't be asking this but in a hybrid, you use a mix of of a combustable fuel (propane) and air pressure. Then i thought it was actuated by usuing some kind of heat source, stun gun or bbq lighter, opening the burst disk and letting out the pressure, tell me if on wrong and what im wrong on.

I don't think you have created a bomb as long as all the chamber parts are rated for more pressure than the combustion can produce. The QEV could be damaged by the strain though.

Hybrids work by combusting a pressurised fuel-air mixture. When the pressure reaches the failure pressure of the disk, the disk bursts, releasing the pressure and firing the launcher.

There is a difference between the pressure generated, and the initial shock of the combustion. PVC is NOT rated for shock pressure, it is intended for use with static pressures.
The impulse from a hybrid in a closed PVC system would no doubt make a bomb.

don't QEVs have a rubber/plastic diaphragm, wouldn't the heat from the combustion eventually damage/melt it.

veginator wrote:All qev's are diaphram valves he is just saying it is very similar to a piston valve.

No there not, the QEV on Hotwired's copper head prime is a piston one.