Search found 13 matches

by Spooky
Wed Jun 29, 2011 9:26 am
Forum: General How-To & Discussion
Topic: Short question topic
Replies: 1488
Views: 100872

I doubt you will notice any power gain/lose but better of going with the tee if you can get a peace of all thread that way the chamber will be closer too the barrel. Yeah, after the join in question I'm going to use two angled 45 degree fittings to bring the chamber directly under the barrel so tha...
by Spooky
Wed Jun 29, 2011 7:59 am
Forum: General How-To & Discussion
Topic: Short question topic
Replies: 1488
Views: 100872

I'm not sure how much of a difference this will make but what chamber design would be more efficent. Using a right right angle end fitting, with slightly less flow. ___________ | QEV Or a T fitting with one end capped. ______________ | QEV The T fittting due to its shape is slightly more open and so...
by Spooky
Mon Feb 15, 2010 4:02 pm
Forum: Pneumatic Cannons
Topic: Small Caliber
Replies: 14
Views: 1354

That's the higher value suggested here when moddeling the QEV, and as I need a some space for breach loading I thought this was a realistic. Reducing the value to zero only increases the power to 20J.
by Spooky
Mon Feb 15, 2010 3:22 pm
Forum: Pneumatic Cannons
Topic: Small Caliber
Replies: 14
Views: 1354

This is GGDT's prediction, modeling a 1/2" QEV and the heaviest pellet I could find at 400 PSI. http://img713.imageshack.us/img713/3179/ggdtiib.jpg 14J = slightly over 10ft/lbs. GGDT gives the best muzzle energy with the heavy pellet. I know that enegry will dissipate very quickly and a lighter pell...
by Spooky
Sun Feb 14, 2010 4:11 pm
Forum: Pneumatic Cannons
Topic: Small Caliber
Replies: 14
Views: 1354

Small Caliber

So, I've got my hands on an old .22 air rifle barrel and was looking at making my own rifle. I know with compressed air it's hard to get high power with a small caliber and the reasons behind that. However, after a few simulations with GGDT I'm getting some pretty poor results power wise. When I loo...
by Spooky
Tue Dec 01, 2009 6:10 pm
Forum: Pneumatic Cannons
Topic: Ball Valves
Replies: 6
Views: 726

Thanks for the feedback. The PN** rating was something I wasn't aware of. I've already used a 15mm version of the same BV in another cannon, looking at it now I can see a previously meaningless PN32 marking on it :) I was hoping to take this cannon up to 400PSI to make up for the short barrel and ch...
by Spooky
Mon Nov 30, 2009 4:40 pm
Forum: Pneumatic Cannons
Topic: Ball Valves
Replies: 6
Views: 726

Ball Valves

Hi guys, after seeing all of the wonderful large bore sawed off style pneumatics about recently I thought I'd give one a go myself. Looking at a ball valve to pilot this is cheap and there's a screwfix 5 minutes drive from me. Now, there's no pressure rating with it so I was wondering how high I cou...
by Spooky
Mon Oct 26, 2009 11:17 am
Forum: General How-To & Discussion
Topic: if you love watching slomo, watch this video !!
Replies: 25
Views: 1501

Thanks a lot for this, without a doubt the best high speed video I've seen.

At around the 5:06 mark it looks like a tumbling bullet impacting sideways. How did they do that?
by Spooky
Thu Sep 03, 2009 4:59 am
Forum: Ammo & Parts
Topic: Source of copper pipe
Replies: 8
Views: 620

Source of copper pipe

I'm building a what I aim to be a compact coaxial and after some planning and mucking around with GGDT I decided to use a 10mm barrel. I ordered from eBay (oops) what claimed to be a "straight 1000mm length" of 10mm copper pipe. When it arrived it was anything but. I'm not sure if it was really a le...
by Spooky
Sun Aug 23, 2009 6:30 am
Forum: Pneumatic Cannons
Topic: Piston Valves Explained Visually
Replies: 175
Views: 130637

I'm working on a coaxial at the moment, just successfully cast my epoxy piston. The problem I'm having is that my copper barrel is sagging inside inside the chamber. This will obviously cause sealing problems as it wont line up correctly with the piston. Thought about sleeving the barrel with someth...
by Spooky
Wed Aug 19, 2009 4:14 pm
Forum: Pneumatic Cannons
Topic: Shorty (First cannon)
Replies: 8
Views: 2200

The barrel is about 2ft longer than the chamber, I know while the chamber/barrel ratio is far from perfect, it is a little better than the pictures make out. That was all the pipe I had and rather cut off a relativity small piece I decided to leave it be. Again, the pilot hangs out that far to make ...
by Spooky
Tue Aug 18, 2009 3:13 pm
Forum: Pneumatic Cannons
Topic: Shorty (First cannon)
Replies: 8
Views: 2200

Shorty (First cannon)

This is my first spud gun of any kind so forgive me if it seems very "ghetto".. or ugly. I built it mainly to be a learning experience, and hope to use what I have learned on this build to make a much prettier cannon next time. So, here she is: http://img34.imageshack.us/img34/2893/dsc00023utp.jpg A...
by Spooky
Tue Aug 11, 2009 5:00 pm
Forum: Pneumatic Cannons
Topic: QEV valves.
Replies: 14
Views: 673

Hi all, I recently decided on and bought the pieces for my first pneumatic based on what I've learned from lurking here on this great forum. I have a question about my QEV. I'm hoping that it will be simple for many of you and someone will take the time to help me out. I don't mean to hijack the ori...