SpudFiles

but how does QEV than works? (and how in combination with the blowgun???)
drawing

becauce words are difficult for me

Ok. Click HERE and look at the second animated diagram down the page.

Click the arrow to start it going.

A QEV is exactly like that - you pump air in through the QEV past a piston and when you use a blowgun to exhaust the air behind the piston in the QEV, the piston flies back, opening up a large passage for all the air in the chamber to quickly blast into the barrel.

hey

i really wanna make one like that what is the part at the end of the gun
called the silver part

hey thanks

so you pump the air via the blow gun in the chamber?

and when i make a gun is there somthing else to know?

like the C:B ratio ?

wat is the best C:B ratio to have

@Simo - it's called a quick exhaust valve (QEV)

@Squad-cog - no, there is actually a T with a air filling valve and a blowgun on each side - you fill the cannon with from one and fire it with the other.

Theres isn't actually a perfect C:B ratio for pneumatic cannons because it depends on the pressure you use and pneumatics can use a large range of pressures. The ratio on this cannon is 1.36:1.

(@Squad-cog - no, there is actually a T with a air filling valve and a blowgun on each side - you fill the cannon with from one and fire it with the other.)

@ Hotwired - but your gun has only a blow gun.
Or is that blow gun in this case also the filling valve?

and with the C:B is there a formula to calculate your perfect C:B

you can calculate the power with E= 1/2m X v^2

energy (in jules) is the half mass(of projectile in kg) times (the speed meter per second)times(the speed meter per second)

example mass is 50 gram and speed 200 meter per second

50 X 1/2= 25 gram= 0.025 kg

0.025 kg X 200m X 200m= 1000 J

so if you make some connections between some more formula than you can do it or not?

In the below picture the blowgun can be seen coming down but there is the filling valve after it. Thats because there is a T fitting in there.



Yes you can fiddle around with gas laws and energy equations but to be honest it's all a waste of time when what you're doing is just fitting together standard parts to lob potatos about.

If you want to know roughly how well a cannon will perform then shove the stats in the GGDT. Thats all I did before making mine.

Hotwired wrote:In the below picture the blowgun can be seen coming down but there is the filling valve after it. Thats because there is a T fitting in there.



Yes you can fiddle around with gas laws and energy equations but to be honest it's all a waste of time when what you're doing is just fitting together standard parts to lob potatos about.

If you want to know roughly how well a cannon will perform then shove the stats in the GGDT. Thats all I did before making mine.

like this???

yup thats it

oke thanks!!!

but than the next question

how did you make that white grip part?

Go to the UKSG site. It will tell you everything. Polymorph is the substance.

Whered uget the qev???

From Airlines Pneumatics.

Other places like Mcmaster sell qev valves too but no one's been able to find a supplier of the type I used in the US that will sell to the public.