Oh boy, I think I'm gonna blow my cannon apart!

[jmccalip]

1lb 11oz aluminum piston! :confused2:

That's what I get for being an impulse buyer and not calculating the weight before hand...


I left the grooves like that in the back for a giant spring to use as a bumper. Disregard the horrid finish of the middle of the piston, I was lazy and using a dull insert and not overlapping, ect. That part doesn't matter anyways.







Anyone want to buy it for a steel cannon? lol

[Gippeto]

No thanks.

I like the shape though.

Welcome to Spudfiles.

[c11man]

to cut down on the weight you could make it more hollow and reduce the diameter of thecenter section

[jackssmirkingrevenge]

Weight watchers indeed

Remember, you don't need you piston to travel more than 1/4 of the barrel diameter for maximum theoretical performance, don't give it space to accelerate too much

[Technician1002]

to cut down on the weight you could make it more hollow and reduce the diameter of thecenter section

To cut down on weight I use HDPE. Gippeto used Nylon. The density is less than 1/2 that of Aluminum.

[jmccalip]

So, with one inch of travel, would ya'll think it's safe at say 50PSI? It couldn't gain that much momentum in one inch, could it? I need to find a good bumper in the mean time...

The only thing that worries me is if the tee breaks. All the fittings are glued to that and have a combined cost of $20.

[rna_duelers]

Well make sure you have a bumper stop that's upto the challenge and I'm calling it a challenge for a reason.

I'm with Technician on this one,get yourself some HDPE and get lathing,half the weight and it's got a very low friction.

[sniper hero]

WOW
this is like pilot............................................fire

[psycix]

You should definitely take off some weight there!

Remember, you don't need you piston to travel more than 1/4 of the barrel diameter for maximum theoretical performance, don't give it space to accelerate too much

Not in a barrel sealer built inside a T and the porting being not very far into the T, especially with a larger seat diameter compared to piston diameter.

[Technician1002]

You should definitely take off some weight there!

Remember, you don't need you piston to travel more than 1/4 of the barrel diameter for maximum theoretical performance, don't give it space to accelerate too much

Not in a barrel sealer built inside a T and the porting being not very far into the T, especially with a larger seat diameter compared to piston diameter.

I try to have the piston free to travel that distance at least before hitting the bumper and slowing. I tend to design so the full piston stroke is about 2/3 the valve seat diameter by the time it stops in the bumper and begins the recoil.

[jmccalip]

Ok, I made a bumper out of an 5" 80lb compression spring.


But then I did some calculations and the surface area of the end of the piston is approx 7". This at 50psi equals 350lbs of force. I don't know how the weight of the piston itself affects things...


Will the spring pancake?

[rcman50166]

Well I can only calculate it if I know how long 350lbs of force would be acting on the piston, if it is a continuous pressure I can do that now though....350>80 so...yes it would

[jmccalip]

Well I can only calculate it if I know how long 350lbs of force would be acting on the piston, if it is a continuous pressure I can do that now though....350>80 so...yes it would

Why does time matter. Wouldn't the force still hit a maximum of 350lbs(for example) no matter what, constant or split second?

Here's a pic BTW.

[Technician1002]

Well I can only calculate it if I know how long 350lbs of force would be acting on the piston, if it is a continuous pressure I can do that now though....350>80 so...yes it would

Why does time matter. Wouldn't the force still hit a maximum of 350lbs(for example) no matter what, constant or split second?

Here's a pic BTW.



How long the pressure is present affects the duration of the pulse accellerating the piston. In my t shirt cannon, the recoil is fairly mild unless I launch a full Gaterad bottle, then it leaves bruises.

Nice pics. It would be a good idea to fill the end cap with someting not comperessable. If the bumper materal compresses enough so the piston hits the male plug, it may shatter the female adaptor. I learned this the hard way with my apple cannon. It had a PVC adaptor, but I had to change it after it was shattered once. Stay clear of the breech. Sometimes they do blow out.

[Carlman]

isnt that a dwv T?