Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 51 users online :: 7 registered, 0 hidden and 44 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Baldyforks, Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Reducing recoil energy

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Reducing recoil energy

Unread postAuthor: SpudBlaster15 » Sat Dec 22, 2007 3:37 pm

Suppose one wanted to build a hand held, shoulder fired cannon with a total weight of about 15lbs, that was capable of 3300ft/lbs of muzzle energy with a 55 gram round. What measures would you suggest for absorbing the ~70ft/lbs of recoil energy (An average hunting rifle produces ~30ft/lbs of recoil energy)? A large recoil pad would likely be a must, and perhaps the builder of said cannon would want to add additional weight.
  • 0

People should not be afraid of their governments. Governments should be afraid of their people.
User avatar
SpudBlaster15
Major General
Major General
 
Posts: 2385
Joined: Wed Oct 18, 2006 11:12 pm
Location: Canada
Country: Poland (pl)
Reputation: 3

Unread postAuthor: Fnord » Sat Dec 22, 2007 3:45 pm

Hybrid I assume?

A padded, spring loaded stock will give the most recoil reduction without adding extra weight.
I believe .50 cal rifles use springs to reduce recoil, and it apparently works quite well (given they produce upwards of 10k ft-lbs).

Edit: ack! I've been sigged! :)
  • 0

Last edited by Fnord on Sat Dec 22, 2007 4:03 pm, edited 1 time in total.
Image
User avatar
Fnord
Major General
Major General
 
Posts: 2244
Joined: Tue Feb 13, 2007 9:20 pm
Location: Pripyat
Reputation: 7

Unread postAuthor: SpudBlaster15 » Sat Dec 22, 2007 3:59 pm

The plan was for it to be a hybrid, as it is the only means of obtaining the required chamber pressure (~800psi when the gas temp is 2500K) without investing in a large high pressure nitrogen or helium tank, which would severely cripple portability.

I like the idea of a spring loaded stock. I will most likely incorporate that into the design when I decide to build the launcher, which will likely be sometime next summer.

Thanks Fnord.
  • 0

People should not be afraid of their governments. Governments should be afraid of their people.
User avatar
SpudBlaster15
Major General
Major General
 
Posts: 2385
Joined: Wed Oct 18, 2006 11:12 pm
Location: Canada
Country: Poland (pl)
Reputation: 3

Unread postAuthor: Ragnarok » Sat Dec 22, 2007 4:03 pm

Does that calculation include an estimation for the momentum of the gas?
Well, obviously a good start is a well built muzzle brake, but that's obvious, so you've probably considered that idea.

More weight would also help, but you'd need twice the weight to halve the energy, and a 30 pound cannon would be insanely heavy, and 35 ft/lbs of recoil is still a lot.

Recoil pads and springs don't reduce recoil energy, but they will reduce recoil force (important difference). You'll still have to absorb all that energy, but it won't feel as much like being hit by a train, and it might also reduce recoil distance a little, as your body would have more time to react and start to counter the cannon's movement.

In short, a muzzle brake, and a good recoil stock are a good start.

@Fnord: Well, a .50 BMG round is about that weight, but roughly 4 times the energy (thus, twice the velocity and twice the momentum). But you will notice that something like the Barrett M82 has a muzzle brake as well, is typically fired with a bipod (often from prone), weighs closer to 30 lbs, etc... all of which makes more difference than just a recoil spring.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: BC Pneumatics » Sat Dec 22, 2007 4:10 pm

Springs and shocks would be a good candidate for absorbing some of that energy, as well as a proper muzzle break.
From what Mark tells me, his Mauler produced somewhere in the range of 75lb/ft of recoil energy, and was shoulder fired with no recoil absorption system at all, though not more than a few times a day.
  • 0

<a href="http://www.bcarms.com/"><img src="http://www.bcarms.com/images/store_logo.png" border="0"> </a>
User avatar
BC Pneumatics
Donating Member
Donating Member
 
Posts: 1089
Joined: Tue Jan 18, 2005 6:55 pm
Location: Fresno, CA
Reputation: 0

Unread postAuthor: VH_man » Sat Dec 22, 2007 4:49 pm

if i were you i would look into some kind of backflow system, like a large-volume pneumatic that fires the opposite direction. mabey like a Coaxial with an electronic pilot.
  • 0

User avatar
VH_man
Major General
Major General
 
Posts: 1827
Joined: Sat Dec 09, 2006 6:00 pm
Location: New Hampshire
Reputation: 1

Unread postAuthor: mopherman » Sat Dec 22, 2007 5:10 pm

What about a compressed air shock absorber? If you have the facilities, you could easily incorporate two into a stock.
  • 0

searching for a modern day savior from another place,inclined toward charity,everyone's begging for an answer,without regard to validity,the searching never ends,it goes on and on for eternity
-Bad religion
User avatar
mopherman
Brigadier General
Brigadier General
 
Posts: 788
Joined: Sat Feb 03, 2007 8:20 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: bluerussetboy » Sat Dec 22, 2007 7:02 pm

55 grams = 848.78 grains
most guys shooting the .50BMG are shooting 647grain FMJ/~175grain charge @2710fps.
this is what produces the ~70 ft-lbs of free recoil energy on a 30 lb. rifle(12.3 fps recoil velocity).
a larger projectile would create even more free recoil energy.
if you could keep that same charge and same velocity but use your 55 gram/848.78grain projectile the free recoil energy would jump to ~103 ft-lbs(14.9 fps recoil velocity).
unfortunately the charge has to be increased to maintain the given velocity, once the charge is increased so is the free recoil energy.


that being said,
even the best muzzle brakes only offer a 45%ish reduction at best. this would knock it down to 38 ft-lbs of free recoil energy.
my .338 Winchester Magnum shoots @ 33 ft-lbs. w/o a brake
my .44 Remington Magnum @ 11 ft-lbs.

the average persons comfort zone is below 10 ft-lbs of free recoil energy.
if you weigh less than 150 lbs be prepared to get hurt



on another note: what is the formula you are using to calculate your free recoil energy?

i've always used a formula from the Lyman Reloading Handbook, 43rd Edition.

E = 1/2 (Wr / 32) ((Wb x MV + 4700 x Wp) / 7000 x Wr)2

E = recoil Energy in ft. lbs.
Wr = Weight of rifle in pounds
Wb = Weight of bullet in grains
MV = Muzzle Velocity of bullet in feet-per-second
Wp = Weight of powder in grains.

(this only works with powder)

Edit: thanks ragnarok for straightening out the formula
  • 0

Last edited by bluerussetboy on Sat Dec 22, 2007 8:07 pm, edited 1 time in total.

bluerussetboy
1st Lieutenant
1st Lieutenant
 
Posts: 265
Joined: Fri Nov 02, 2007 12:25 pm
Reputation: 0

Unread postAuthor: ALIHISGREAT » Sat Dec 22, 2007 7:28 pm

you could use a system like on the rt-20 which directs the hot gases back through a fat tube on the top http://world.guns.ru/sniper/sn56-e.htm
  • 0

User avatar
ALIHISGREAT
Major General
Major General
 
Posts: 1779
Joined: Sat Aug 25, 2007 6:47 pm
Location: UK
Reputation: 0

Unread postAuthor: mopherman » Sat Dec 22, 2007 7:33 pm

ALIHISGREAT wrote:you could use a system like on the rt-20 which directs the hot gases back through a fat tube on the top http://world.guns.ru/sniper/sn56-e.htm

I wouldn't attempt this unless you want hot hybrid gas in your face. This would also be wasteful with the limited gases on tap.
  • 0

searching for a modern day savior from another place,inclined toward charity,everyone's begging for an answer,without regard to validity,the searching never ends,it goes on and on for eternity
-Bad religion
User avatar
mopherman
Brigadier General
Brigadier General
 
Posts: 788
Joined: Sat Feb 03, 2007 8:20 pm
Reputation: 0

Unread postAuthor: ALIHISGREAT » Sat Dec 22, 2007 7:48 pm

I wouldn't attempt this unless you want hot hybrid gas in your face. This would also be wasteful with the limited gases on tap.


but the tube would either be on the side of the barrel or the sight would be on the side of the barrel like on the rt-20 and i think it would be worthwhile doing because it would reduce the recoil massivly.

Another alternative is to add a big silencer near the muzzle and then have a muzzle brake aswell to further reduce the recoil, this combined with a recoil absorbing stock and a bipod should make the recoil perfectly manegable :)
  • 0

User avatar
ALIHISGREAT
Major General
Major General
 
Posts: 1779
Joined: Sat Aug 25, 2007 6:47 pm
Location: UK
Reputation: 0

Unread postAuthor: Ragnarok » Sat Dec 22, 2007 7:53 pm

@BluerussetboyThat formula seems to be missing a set of brackets:
E = 1/2 (Wr / 32) ((Wb x MV + 4700 x Wp) / 7000 x Wr)<sup>2</sup>


Talking about recoil, I only weigh about 160-170 lbs (never sure exactly how much), and I've fired rounds from HEAL that reach about 12 ft-lbs free recoil energy - and I'm fine with that. I even welcome a moderate kick, it adds nicely to the experience of shooting my launchers, and there's a nice feeling that adds to the cool of making a vegetable cross your garden at half the speed of sound.

I wouldn't routinely shoot something with a recoil over maybe two or three times that because then you start to risk developing a flinch, but I have few projectiles that can generate that sort of recoil, so I should be all right there - at least until I get another craving for more pressure.

@ALIH... etc: That wouldn't be that much different to a muzzle brake in terms of recoil reduction, but it would certainly cut performance big time.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Unread postAuthor: ALIHISGREAT » Sat Dec 22, 2007 8:01 pm

But if you put the vent in the barrel to feed the tube very close to the end of the barrel? and after further thought would a supressor attachent before a brake actually increase the felt recoil because it would reduce the effectiveness of the brake?
  • 0

User avatar
ALIHISGREAT
Major General
Major General
 
Posts: 1779
Joined: Sat Aug 25, 2007 6:47 pm
Location: UK
Reputation: 0

Unread postAuthor: bluerussetboy » Sat Dec 22, 2007 8:04 pm

Ragnarok wrote:@BluerussetboyThat formula seems to be missing a set of brackets:
E = 1/2 (Wr / 32) ((Wb x MV + 4700 x Wp) / 7000 x Wr)<sup>2</sup>




guilty of c/p. i wasn't sure of how to post/format the formula online. plus there was a couple of IPAs involved.

thank you
  • 0


bluerussetboy
1st Lieutenant
1st Lieutenant
 
Posts: 265
Joined: Fri Nov 02, 2007 12:25 pm
Reputation: 0

Unread postAuthor: Ragnarok » Sat Dec 22, 2007 8:28 pm

Don't worry about it, it was no problem at all.
  • 0

Does that thing kinda look like a big cat to you?
User avatar
Ragnarok
Chief of Staff
Chief of Staff
 
Posts: 5339
Joined: Tue Dec 19, 2006 8:23 am
Location: The UK
Reputation: 8

Next

Return to General Spud Cannon Related

Who is online

Registered users: Baldyforks, Bing [Bot], Exabot [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'