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Already got 16mm o.d and the i.d is 9mm so see how we go, maybe i will needs to get a new one or find someone to open it out. 3/8" is 9.52mm. I think alot of people list 3/8" as 9mm
Jackssmirkingrevenge - yoou mentio having two guages, the first on the main tank, I completely.understand, but the second one on the secondary tank, please excuse my noobness, but wouldn't that read empty after firing? I have never held, fired or.even seen one of these in the flesh. When firing them is it just a press of the buttun (in my design) or do you have to hold the button down, although for a very short time period?
please forgive my lack of knowledge, I am trying to learn and 3 weeks ago wouldn't even ha e though about an air cannon
Two gauges will give you an idea of the actual firing pressure for every shot, to give you a real value to compare with the theoretical value as explained by PM
You pull the slide valve, that's it. Most people but a spring or rubber band to reset the slide valve automatically
In the old country we used to say "The question is knowledge's sister"
Thanks for being such a great asset to me, but also the entire forum, nice to see people like you are out there.
Sorry when i said buttun I was thinking of my original design, so with a slide valve you just pop it open and it can be returned straight away, it doesn't require being in the open position for more than a blink of an eye?
Blink of an eye, the whole pilot venting-firing process happens in a fraction of a second.
You can practically wank you slide valve as I shamelessly do here:
Jacksmirkingrevnge - can you see from my poor drawing any theoretical reason why my gun wont work or anyway to improve its design? As it is very similar to your gun in the video except mine will use air stored in a cylinder and yours is to and airline. I did read that you. Had modified your qev with a small hole and light spring?
just one more question! As my gun will be using air solely from the small cylinder for each shot, does this mean I don't need that larger connection to the main tank? Currently the hole measures around 9mm and is threaded, I have tried a few fittings and bolts just to ensure it is a standard thread, it seems to be. I realize that this size will decrease significantly with a fitting and I may end up with about 4-6mm (i hope) hole, is this going to be large enough to refill my secondary tak within a sensible time?
Do you remember what diameter barrel and cylider volume you used or was it just a test?
thanks for your help.
No modifications to the QEV, your design should work well as drawn.
Flow from the main tank does not need to be as high, remember that it has to leak past the piston of the QEV to fill the firing chamber so with that bottleneck, it really doesn't matter.
From my other thread:
This is the sort of damage it did with plastic BBs:
Re: QEV trigger release
Thanks for the explanation and hell Jakesmirkingrevenge, you have once again been most helpful.
Just out of interest was that at really short range, the results are kind of awe inspiring if plastic bbs can do that.
Last edited by jrrdw on Tue May 06, 2014 5:32 pm, edited 1 time in total.
Reason: Double post.
It is exactly how I want/envisage my gun to look like, if it turns out half this good I will be pleased.
Easy to make using off-the-shelf parts, you should be able to replicate the result without too much trouble.
Good that's reassuring to know.
I saw a thread about asking if someone can run your figures through the program (can't for life of me remember its name) can someone either post me in the direction of this thread as I wish to follow any necessary protocol,, or if its just a case of asking nicely would anyone be able to run my figures as I had no access to a PC at the moment.
Just in case anyone would the details I intend on unless any improvements are suggested
Pressure - 150psi
Barrel bore - 8.5mm (0.335")
Barrel length - 600mm (24 inch)
Using a QEV and a slide valve to control air flow, I will have a main air storage tank of ~900-1000ml and then a secondary tank which will be the air for each shot, just need to know what the ideal should be?
Due to my intended magazine and loading system the barrel my be just under 24", maybe 23" where the ball bearing will enter, but I guess as the QEV is at the end of the barrel it doesn't have any effect? Or does it?
I am a newbe, but keen to learn and understand, I don't want people to think I am wanting them to do everything for me, just stuck without a PC to run the program, I am interested in ultimate power that I can get from my setup. Screwed up on my barrel size really as no cheap slingshot bearings come in this size, so once I have an up and working gun I may alter this so ammo will be cheaper.
With only 150psi and a 12mm (~1/2 inch just under) will the heavy ball bearing ammo exit so slowly and virtually just drop out the sky after a few meters/yards?
Here's a quick GGDT model:
With a firing chamber volume of just 35mL at 150 psi, you get 384 fps for a 2.5 gram ball bearing and are just above the UK legal limit. I also threm in a generous 5mL of "dead volume" - space between the QEV and the BB - to account for your reloading mechanism.
Most certainly not. A typical CO2 pistol will shoot steel BBs around the same speed and has a fairly decent reach, while here you are shooting a projectile that is over 6 times heavier.
Are you saying i will only get around 12lb/ft from my cannon, I am am very disappointed I could buy an air gun with that much power. What is the problem with my design? Do I need more pressure or heavier ammo? As a lot of peoples on here seem a lot more powerful?
Is the 35ml secondary chamber optimal for power or is that to keep it down to the legal limit?
Looking at your first simulation with the program you used an air volume of 10, so if I make my chamber 10 and replace the barrel with 1/2" that will get my power up, Some and then for any more power I'm need more pressure correct? Or have I got it all confused?
It is looking like I need a shock pump short term until I am able to source/setup a fridge compressor. I think I will increase my pressure, check the cannon is all fine using my 8.5mm ammo and the source a new barrel/ammo to get some proper power
Thanks to everyone for your help and especially Jackssmirkingrevenge for his time for all the answers and doing the simulation of how it will perform, greatly appreciated, I would be lost without the help you guys have given me, thanks
PS Worried I am going to be disappointed with the 8.5mm BBs so have ordered some 12mm BBs with the intention of measuring them and then purchasing a barrel(tube) for a nice fit.
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