Some small arms engineering questions

[IlikeSA]

For those of you who are professional physicists or engineers, just wanted your thoughts on this:

Would a hydraulic or air shock system, say for the front fork of a bike but scaled down and adjusted for recoil impulse be superior in longevity compared to the modern spring system used in small arms today? While I admit that springs utilize the KISS principle, they have to be replaced in 1911's every 2-3000 rounds.

 

[stevemis]

Your question is probably best posed on the Gunsmithing and Repairs forum.

Weight and size would be my initial concerns with your proposal.

 

[Whiskey11]

The nice thing about springs is that they build force in a decently linear way. Hydraulic shocks using air are not necessarily act in a linear fashion, take up more space and offer little durability. Not to mention it is easy to build a spring guide, not so much for a small air cylinder and the fact that it would have to be small and I'm not sure the air cylinder could correctly reduce the recoil of a firearm.

 

[essayons21]

No.

Seals would fail, just like they do on bike shocks. The tiny circumference would be difficult to properly seal in the first place, and with the additional heat, all but the most expensive materials would most likely quickly break down. Not to mention you wouldn't want to use petroleum based or penetrating oils.

However, an application for this concept does exist in the firearms industry.

http://www.nokick.com/Enidine_Shot_Shock_p/mesa tactical 92170.htm

ETA: Not an engineer, although I did make it through 2 years of it in college. Used to race mountain bikes and rebuilt a few forks.

 

[grizz13]

The biggest problem with this is that spring force is related to its compressed distance. so the farther you compress it the greater the force.
The air or fluid "shock absorbers" force is related to the velocity of the follower so the faster it moves the more force it exerts. These shock absorbers would slow the rearward movement of the slide but once it stopped it would not return the slide to the closed position.

 

[Maverick223]

Would a hydraulic or air shock system, say for the front fork of a bike but scaled down and adjusted for recoil impulse be superior in longevity compared to the modern spring system used in small arms today? While I admit that springs utilize the KISS principle, they have to be replaced in 1911's every 2-3000 rounds.

Hydraulics would be less than ideal due to a couple of deleterious design aspects. First they are somewhat heavy because they utilize a fluid (typically a medium weight petroleum derivative); secondly they are fairly slow (which would naturally slow the operation of the firearm). Pneumatics would be a slightly better choice, but still require a fairly lengthy area due to the stroke being less than half of the OAL. Though this can be overcome by designing them in such a way that they were in front of the bolt and expanded during recoil, retracting to return to battery. OTOH pneumatics also comes with its own problems. The tolerances of the seal must be much tighter than on the average hydraulics system because of the relatively small transmission fluid molecule size (ideally you would need a highly compressible inert gas; one that, to be quite honest, I doubt exists).

I can see it working, but maintenance concerns likely wouldn't improve and may even degrade. Most importantly cost would skyrocket due to the greater complexity, manufacturing, and design cost. Additionally field repairs would be made much more difficult for like reasons. In short, the problems are near insurmountable, and the gains (if any at all) will be modest at best.

These shock absorbers would slow the rearward movement of the slide but once it stopped it would not return the slide to the closed position.

This is incorrect; a sealed system would return the bolt/slide to battery just fine (though the length of stroke vs. the OAL of such a system would be a BIG problem).

 

[Justin]

I believe there's an outfit that makes a hydraulic replacement for the spring and buffer assembly that goes in an AR15.

I don't have any experience with them, but I believe they can be purchased from Brownell's or Midway.

 

[Langenator]

You're referring to the AR-Restor. I believe it supplements, rather than replaces, the existing buffer and spring system, to soften the recoil.

I've never used one, but from what I've heard they're not the most reliable things.

Regarding hyrdaulics: one thing I remember from watching Junkyard Wars - if one of the teams used hydraulics, they lost, because their machine always broke.

 

[merlinfire]

That recoil buffer looks pretty cool, the review a guy gave on that site is that it makes shooting slugs feel like shooting 8 shot.

 

[unspellable]

Some large artillery pieces use hydraulic buffering.

Consider the valve springs in your car. While cruising on the freeway they are cycled around 1500 times per minute. They are exposed to extreme temperatures. We expect them to last for 120,000 miles. Why the h**l are we talking about replacing recoil springs after 1500 rounds?

 

[Shear_stress]

A shock absorber would add weight and complexity to the system and will need a return spring anyway.

 

[IlikeSA]

Thanks for the comments. Sometimes I come up with odd ideas in adapting technology and it's good to have a forum to discuss it on. Heck, I am glad to have a good forum to discuss firearms on! You can learn something new everyday!

 

[BeerSleeper]

The simplest solution to replacing springs every 2k-3k rounds would be to buy better springs.

 

[Owen]

I'm with Beer Sleeper, you need to buy better springs. 1500 rounds is a ridiculously low interval.

 

[BBQLS1]

Replacing springs every 3K rounds is very conservative and is generally done just to make sure the gun works in the event you need a HD weapon to work. A fun gun could get away with way more than that.

IMO the problems with a hydraulic or air system like you described would be:

1. cost (springs are way way way cheaper)
2. potential for leaking seals (and failure)
3. additional weight added to the gun

Springs are simple and reliable, I see no reason to change from them.

 

[BeerSleeper]

There's a website where I guy put 15,000 rounds through his glock without cleaning it, as a test of it's reliability. I don't think he replaced any parts, either. Maybe whoever supplies glock their springs needs to make some for the 1911.


at the same time, I agree with one choosing excessive maintenance to keep a HD/SD/carry gun in tip-top condition. Springs are cheap, and a HD/SD/carry piece is a take no chances proposition IMO.

 

[MrCleanOK]

It's important to note that there is a difference between hydraulics and pneumatics. Hydraulics use liquids, which are incompressible. Hydraulic "shocks" use the hydraulic fluid as a damper, which resists motion in both directions (compression and return cycle). The hydraulic fluid is there to stop your car, bike, whatever from oscillating after you hit a bump.
Pneumatics use compressible fluids (gases), and can be used as air springs (which resist motion in one direction). There are many reasons you can't use air springs in firearms, a few that come to mind quickly-
Size & weight would be prohibitive
Seals would wear out quickly, and the air spring would have to be serviced constantly
Compressing gases generates heat (a lot of heat, in some cases), and due to losses some of it would stay in the system.

 

[ambidextrous1]

How about gas springs, as used on automotive hoods & trunk lids? I have seen gas springs small enough to mount in a rifle butt stock. I imagine smaller ones could be adapted to pistol use.

I don't know how many cycles a gas spring will typically perform before failure, but maybe some of the 'gear heads' on this forum can supply that information.

 

[benEzra]

From personal experience, I can vouch for the fact that gas springs aren't nearly as durable as metal springs. As the seals age, they leak down, and a cracked seal will result in a sudden and unpredictable failure. I've had to replace numerous gas struts on various cars I've owned over the years when they eventually "went flat" due to bad seals.

Good metal springs, on the other hand, will last for generations if not used too much, and if used a lot will weaken slightly in very predictable ways but will often still be usable.

 

[Maverick223]

Thanks for the comments. Sometimes I come up with odd ideas in adapting technology and it's good to have a forum to discuss it on.

While it may not be the best idea, I appreciate you sharing it with us. At the very least if gives me something to think about and, who knows, someone may come up with a useful product based upon your idea.

 

[Vern Humphrey]

Artillery pieces use hydraulic recoil mechanisms, and most use compressed gas recuperators to return the gun to battery. But artillery pieces are moved by motor vehicles, not carried in a holster or on a sling over your shoulder.

 

[Jim Watson]

Consider the valve springs in your car.

The difference is that valve lift in a car is a fraction of an inch, the springs are not compressed as deeply as the slide travel in a gun.

Maybe whoever supplies glock their springs needs to make some for the 1911.

ISMI makes flatwire springs for the Colt OACP and I think they will do one for the chronically undersprung 4" guns from Kimber and others.

I don't know if they sell one for a full size 1911 but if not, a Glock spring will fit if you make a skinny guide rod for it. It is a little larger than the usual roundwire spring and squeaks like a new pair of shoes, though.

 

[Owen]

The squeaking square wire spring is one of the reasons manufacturers have moved to plastic guide rods. The plastic guide rod doesn't squeak when the edges of the spring are dragged over it.

 

[RimfireChris]

There was, IIRC, something called the Harts Recoil Reducer. It didn't replace the spring, but the spring guide, with a tube filled with ball bearings and mercury, again IIRC, that used inertia to dampen recoil. Don't know if they're still made though.

 

[Maverick223]

Artillery pieces use hydraulic recoil mechanisms, and most use compressed gas recuperators to return the gun to battery. But artillery pieces are moved by motor vehicles, not carried in a holster or on a sling over your shoulder.

Not to mention that it isn't notably quick cycling. It doesn't make any difference when used for artillery that is loaded one shell at a time, but i'd want my SA firearms to return to battery a bit quicker.