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theperfessor
10-12-2013, 12:00 AM
A diesel engine works by compressing air rapidly in a confined space, which raises the air temperature, then an injector squirts in a measured amount of fuel that vaporizes and ignites to create pressure against a piston.

Anybody ever apply this to a real weapon? I can remember putting 3-in-1 oil in a Daisy BB gun chamber and occasionally getting a much sharper crack out of the muzzle.

A diesel will run off of a lot of different fuels. How about shooting all afternoon with some cast bullets and a can of corn oil or leftover french fryer grease!

I would imagine that most air gun technology would apply.

SciFiJim
10-12-2013, 12:23 AM
Hmm, I would think the oil would have to be a booster fuel, with the primary force being compressed air.

Maybe something like a breach loader that after placing the boolit and oil in the chamber, a nozzle or nipple swings into and locks into place.

Compressed air could be supplied by a pumping lever on the gun or an external source like a scuba tank.

I am thinking something something like the large bore air guns available today only boosted.

waksupi
10-12-2013, 12:25 AM
Very interesting concept. I do hope it piques someone's curiosity enough for them to pursue an answer!

starmac
10-12-2013, 12:30 AM
Wear welding gloves, the compressed air has to be pretty hot to ignite diesel IIRC 500 degrees.

TXGunNut
10-12-2013, 12:31 AM
I can see this working better for a machine gun or a cannon, not for firing one well-aimed shot from a conventional shoulder-fired weapon. Getting combustion timed to a sear release would probably result in a very long "lock time" and compressing the gas would require a pretty stout spring...machinery to make all that work would be a bit complicated and possibly bulky but it sounds like fun.

xs11jack
10-12-2013, 12:39 AM
The more volatile the fuel, the easier it is to ignite. Oil would not be the best candidate. That is why hair spray is used in potato cannons. What about alcohol? Say 91 %?
Ole Jack

Bzcraig
10-12-2013, 12:40 AM
Ok, you guys have too much time on your hands! Get back to work!:bigsmyl2:

starmac
10-12-2013, 12:42 AM
Yea it would down right suck for your diesel to gell up while you had your sights on that trophy buck. lol

We used accetylene and oxygen in them potato guns. lol

GaryN
10-12-2013, 12:50 AM
I know I have had my spring piston air rifle diesel occasionally when I put too much oil on the piston. It said it would do that right in the instruction manual. I don't think it would be that hard for some engineer type to come up with something that would work.

Gray Fox
10-12-2013, 12:55 AM
DARPA has been working on liquid propellant for artillery guns for 20 years or so. I haven't read anything about possible success, though.

theperfessor
10-12-2013, 01:06 AM
I don't think it would be hard to make one work. I think it would be hard to make one that would be user friendly, ie make it light, simple, easy to use, etc. The possible performance could easily exceed a basic airgun.

Just Duke
10-12-2013, 01:08 AM
I worked on a project with a couple other engineers. Gas does not provide a steady and consistent pressure going out the barrel. It's basically a quick fhart. Powder continually provides pressure until the projectile leaves the barrel.

Bob in Revelstoke
10-12-2013, 02:29 AM
Probably 30 or 40 years ago Daisy came out with a rifle that fired a bullet with hot air the was produced by a spring powered piston forcing air through a venturi tube which then produce sufficient heat to ignite a solid propellant affixed to the rear of the bullet. The rifle was expensive for it time as was the ammunition. I can't recall its name but they are now collectors items. The same principal could possibly be used for a liquid fuel but metering would likely be a problem. I can recall putting 3 in 1 oil in a Red Ryder BB gun. It would "diesel" and produce erratic velocity and smoke, which was the main thing. Anything is possible, but would the expense be worth it?

Swamp Man
10-12-2013, 07:52 AM
Why bother when we have Big Bore PCP air guns already? Just build up on that type of platform by adding extra air chambers or higher air pressure.

Dan Cash
10-12-2013, 08:02 AM
Binary fuel/liquid propellant experimental weapons date back to at least WWII. Desireable as the propellant is non combustable/explosive until mixed in the weapon's chamber. Controlling the mixture and regulating the thrust has been the problem hindering the development.

JonB_in_Glencoe
10-12-2013, 08:05 AM
I worked on a project with a couple other engineers. Gas does not provide a steady and consistent pressure going out the barrel. It's basically a quick fhart. Powder continually provides pressure until the projectile leaves the barrel.
I am not an engineer, but this was my exact initial thought...getting consistancy would be nearly impossible...Varying factors in the makeup of the combustion air would be another big problem.

429421Cowboy
10-12-2013, 08:06 AM
Probably 30 or 40 years ago Daisy came out with a rifle that fired a bullet with hot air the was produced by a spring powered piston forcing air through a venturi tube which then produce sufficient heat to ignite a solid propellant affixed to the rear of the bullet. The rifle was expensive for it time as was the ammunition. I can't recall its name but they are now collectors items. The same principal could possibly be used for a liquid fuel but metering would likely be a problem. I can recall putting 3 in 1 oil in a Red Ryder BB gun. It would "diesel" and produce erratic velocity and smoke, which was the main thing. Anything is possible, but would the expense be worth it?

I believe that was the Daisy V/L Caseless ammo system, in my 1972 Herters catalog it is listed at $1.05 for 100 29 grain bullets and a non corrosive priming system. Seems like kind of a neat plan but must have went pretty much nowhere.

10x
10-12-2013, 10:48 AM
you may want to look at this
http://www.mekanizmalar.com/diesel_pile_driver.html

roysha
10-12-2013, 11:17 AM
One of the reasons the VL went nowhere was that Daisy was not a licensed firearms manufacturer and the gestapo (BATF) shut them down after about 18,000 rifles were made. I have one and a couple boxes of ammo. Needless to say, when the ammo is gone I will have a wall hanger.

Just a word about dieseling, or worse, detonation, when using a conventional springer; this practice can destroy seals in very little time. The reason the seal in the the VL (for the designer Von Langenhoven [sic]) was not damaged was because of a valving system that shut off the gasses to the seals. It is really quite ingenious and I am a bit surprised someone has not resurrected it in one form or another, especially as some type of repeater since there is no need for extractor or ejector. The propellent pellet is quite sturdy, at least my experiments indicate such, so the rounds would survive the feeding function

HARRYMPOPE
10-12-2013, 11:50 AM
I had a Hatsan that came from the factory with a compression chamber soaked with oil.the thing cracked like a 22 and flames came out the barrel.seal was gone in less than 100 shots.I took it apart and the seal just plain melted.

Multigunner
10-12-2013, 12:31 PM
It may not be necessary for the fuel to ignite in order to raise velocity.
When gases or vaporized liquids are heated they expand rapidly whether or not they ignite. Expansion of gases is what drives a bullet.

An easy example is the increased velocity from a CO2 gun on very hot days.

StratsMan
10-12-2013, 01:50 PM
If you have ignition and propellant gases are created, doesn't that make it a 'firearm' and no longer an Air Gun??? Hence, subject to NFA and all subsequent firearms laws???

W.R.Buchanan
10-12-2013, 02:31 PM
OK guys,,,, The German Company Weihrauch who makes a lot of the good Spring Piston air guns once produced a version of the HW35 in .22 cal. know as the Barakuda.

http://www.pyramydair.com/blog/2006/05/weihrauch-barakuda-el54-ether.html

It was a normal HW35 in .22 cal. with an attachment that dispensed a drop of ether behind the pellet just before you fired the gun.

It produced .22 LR velocities from a gun that normally had 580 fps velocities in .22 cal.

So the short answer to the OP's question is . It was done in the late 60's early 70's.

They used Ether as the propellant due to its low flash point. IE the compression of the piston in the gun easily ignited the ether.

On a side note: There are Diesel Model Airplane Engines that have been around from the beginning. In fact most European Model Airplane Engines are Diesels.

They run on a fuel made of 33% kerosene, 33% Ether, and 33% Castor oil.+ some traces of some additives I have forgotten.

These engines are compression ignition engines and the combustion chamber is adjustable to cope with ignition timing and actual compression. They end up running in the 9:1 Comp ratio regime due to the inclusion of Ether in the fuel which lowers the flash point of the fuel mixture.

These engines are about 1.5 times the horsepower of a similar displacement Alcohol/Nitro fueled Glow Ignition style engine common here in the US. This mainly due to the higher density of the Kerosene. The ether is in there to start the fire easier.

This is also the reason why diesel engines produce more power than gas motors. Normal gasoline is around 10,000 BTU's per pound. Diesel fuel is 18,000 BTU/LB. Kerosene is even higher and that's why they use it as Jet fuel.

It is easy to see this if you look at the structure of the individual molecules of fuel. Natural Gas is CH4 "Methane" that is one carbon atom with 4 hydrogen atoms surrounding it. Gasoline is 6,7,or8 carbons lined up IE: Sextane, Septane /Heptane, Octane, with 14, 16 or 18 H's around. Diesel is 12,13,14 carbons and 26,28,30 H's and kerosene is 20-40 C's in a row, with 42- 82 H's !

It is easier to see how these denser fuels have more poop. This is why 75% of the cars in Europe are diesel powered. VW Jetta wagons have a 2.0 L engine that produces 140HP and gets 42+ mpg. A new 2.8L BMW engine in the 3 series cars is 280HP and yields 45 mpg. Looking at one of those later today or tomorrow.

This is why I own diesel powered vehicles.

Randy

theperfessor
10-12-2013, 03:21 PM
Randy, thank you so much for a very helpful and informative post. It's obvious you know a lot about diesel technology and application. This seems like an area that might be worth exploring. When primers and powder are in short supply, having a weapon that works on kerosene/diesel fuel would seem like a reasonable back up/last resort.

How handy would a .25/20 equivalent that runs on K1 be?

MT Chambers
10-12-2013, 03:32 PM
The gun would not meet the emission requirements in Kalifornia, and then you have the lead pellet, think of the children!

HARRYMPOPE
10-12-2013, 07:26 PM
Why do the theory threads get more posts than ones with real "meat' ?

Blacksmith
10-12-2013, 07:42 PM
IIRC someone did some experiments with dieseling air rifles and had a write up in a gun magazine. He was trying different fuels I think. He was using standard lead pellets and had problems with blowing a hole through the pellet. He solved that by putting a drop of glue in the hollow of the pellet and letting it dry. I don't remember the name of the magazine and could have been 30 or 40 years ago.


JUst Google Diesel Air Rifles and you will have plenty of reading.

W.R.Buchanan
10-12-2013, 08:10 PM
Because there is more to talk about in theory.

Perffessor: a gun that worked this way could be made, but the starting point probably wouldn't be an existing gun. It could be a beefed up version of an existing gun, or something that worked like one.

When you start talking about a large caliber gun like in 38-45 cal. or even something that would shoot .25-.30 caliber boolits then propelling the boolit with a diesel explosion could be a viable way of powering it.

The problem would be how to ignite the fuel. A spark probably isn't going to do it due to the high flash point and low volatility of the fuel, and igniting it with compression would require some type of spring mechanism like a spring piston gun has. However this mechanism would have to be built specifically to handle the increased pressures(10-20,000 psi?) involved when the mixture goes off. This rules out using any existing gun, so you would have to start from scratch.

A propane powered "potato gun" that would fire with a spark might be a better way to go about it.

Imagine an M203 40MM grenade launcher with a sealed breach and a spark igniter in the center of the breach face. A projectile looking like a Large(40MM) Pellet is loaded into the barrel. There would be a 2 stage trigger that would release some propane into the area behind the pellet and then the final stage of the trigger pull would fire the gun. Or you could have a separate trigger that would release as much propane as you wanted by how long you depressed the valve, for close range or long range targets.

Load development would consist of figuring out how long to hold the gas valve open before you fired it.

I have had this one on the internal drawing board for along time, and since it is big bore,,, it would be more fun!

Looks kind of like this.

Randy

waksupi
10-13-2013, 01:38 AM
Why do the theory threads get more posts than ones with real "meat' ?

Where do you think product development comes from? Some one says, "Shazam! here it is"?

Pakprotector
10-13-2013, 09:10 AM
One of the reasons the VL went nowhere was that Daisy was not a licensed firearms manufacturer and the gestapo (BATF) shut them down after about 18,000 rifles were made.

Just a word about dieseling, or worse, detonation, when using a conventional springer; this practice can destroy seals in very little time. The reason the seal in the the VL (for the designer Von Langenhoven [sic]) was not damaged was because of a valving system that shut off the gasses to the seals. It is really quite ingenious and I am a bit surprised someone has not resurrected it in one form or another, especially as some type of repeater since there is no need for extractor or ejector. The propellent pellet is quite sturdy, at least my experiments indicate such, so the rounds would survive the feeding function

The springer seal will just have to be made from a material that will tolerate such use. First one that comes to mind is Teflon, but it creeps...so the seal design must be specialized. Second, you need a consistent burn. Consistent light off and measurable qty come to mind to solve that one. Perhaps pack the back of the pellet with graphite powder?

Now when I hear a knock at the door, and the announcement, 'Alcohol, Tobacco and Firearms' I want to see a salesman( or perhaps a team of them ).
cheers,
Douglas

Multigunner
10-13-2013, 01:03 PM
Now when I hear a knock at the door, and the announcement, 'Alcohol, Tobacco and Firearms' I want to see a salesman( or perhaps a team of them ).

Or better yet the neighborhood welcoming committee making sure you have all you need to enjoy your new home and participate in community events.

As for the piston.
I have a odd small piston I found long ago that may be a salesmans sample. It has a hole in the center of the top, I haven't figured out why. It has the grooves for the rings. It may not be for an engine, but rather for some sort of pump.
Also there are large diameter model airplane engine cylinders that could be adapted to an airgun.

The Crosman M1 Carbine sping piston gun used a valve that forced a probe forwards as pressure built up, the probe striping the bb from the feed trough. The air didn't come through till the pressure built past a certain level to open the valve against spring pressure. That would be a good addition to a diesel gun.
Some method of metering the amount of expanding hot gas would make shots most consistent, with excess gas bled off as from a short stroke gas piston on a autoloader.

deltaenterprizes
10-17-2013, 09:00 PM
Tippman makes a propane powered paintball gun that I think should be able to be modified or copied to propel pellets.

John Taylor
10-17-2013, 09:04 PM
I have had a few thoughts on this. First would be to use OX instead of air, faster cleaner burn. A spring/piston gun would need a check valve or it would push the piston back from the rise in pressure. A very small piston pump to act as an injector pump, think old steam water pump only a lot smaller. This small injector pump would run off the same pressure going to the barrel so the fuel would be injected at the same time as the pressure is rising behind the pellet/bullet. This system would also require a separate total discharge chamber with a valve between the main storage chamber. I have an old Crossman pump 22 pistol that uses this type of air chamber, just does not have a separate storage chamber. My problem is in the injector, I don't have drills small enough to make a hole small enough to atomize the fuel.
For propane to work there would need to be an air space, propane will not burn without the proper amount of air.

lreed
10-17-2013, 10:09 PM
Has anyone used the nail guns that use some sort of fuel-air mixture and battery ignition? They sure do drive nails and I would think a bullet if modified to do so. lreed

jmorris
10-18-2013, 09:34 AM
DON'T TRY THIS AT HOME OR ANYWHERE ELSE!!! but I have fired solid range golf balls over a 1/4 mile with Oxy/Act...

KCSO
10-18-2013, 09:43 AM
This was the Daisy VL rifle back in the late 70's. The hot air set off the caseless charge.

Multigunner
10-18-2013, 06:46 PM
The Russians once used an airgun that ran off an engine of some sort.
I forget most of the details but it fired large diameter steel balls through a curved tube to injure or kill any infantry who tried to climb onto a tank to set anti-tank charges or do other mischief.
They got the curved barrel idea from the Germans, who had used a curved attachment for the STG44 in the same manner.

W.R.Buchanan
10-23-2013, 03:36 AM
Potato guns use hairspray and a BBQ igniter. I have used Oxy/Acet to fire potato guns as well. To get the mixture you light the torch and adjust the flame until it is right then snuff the flame and stick the torch tip into a small hole in the gun barrel then touch it off with the re-lit torch.

You get more distance by how long you leave the torch in the bbl before you touch it off.

However these are all firearms.

The reason why the Germans had such good Air Guns is because they weren't allowed to manufacture Firearms after both wars. Air Guns still kept them in the gun business.

Randy

lksmith
10-26-2013, 11:38 AM
One of the reasons the VL went nowhere was that Daisy was not a licensed firearms manufacturer and the gestapo (BATF) shut them down after about 18,000 rifles were made. I have one and a couple boxes of ammo. Needless to say, when the ammo is gone I will have a wall hanger.

Just a word about dieseling, or worse, detonation, when using a conventional springer; this practice can destroy seals in very little time. The reason the seal in the the VL (for the designer Von Langenhoven [sic]) was not damaged was because of a valving system that shut off the gasses to the seals. It is really quite ingenious and I am a bit surprised someone has not resurrected it in one form or another, especially as some type of repeater since there is no need for extractor or ejector. The propellent pellet is quite sturdy, at least my experiments indicate such, so the rounds would survive the feeding function

Actually that has been tried. Anybody recall the Metal Storm weapons from a few years ago?

mikeym1a
10-26-2013, 11:44 AM
The more volatile the fuel, the easier it is to ignite. Oil would not be the best candidate. That is why hair spray is used in potato cannons. What about alcohol? Say 91 %?
Ole Jack

91% alcohol in a gun???!!?? That out to be in a glass!!!!!!!!!! :bigsmyl2:

Multigunner
10-26-2013, 06:10 PM
91% alcohol in a gun???!!?? That out to be in a glass!!!!!!!!!! :bigsmyl2:
Walgren's drug store sells 91% rubbing alcohol. It burns fairly good.

You can increase alcohol content by placing a bottle in a freezer for several days, water will settle out and freeze into a layer of ice at the bottom of the bottle, what you pour off the top will be nearly pure alcohol.
I've used a similar method to remove water from heating kerosene . I set a plastic container outside for several days in freezing weather till ice forms at the bottom. What rises to the top burns clean and bright in my oil lamps.

geargnasher
10-26-2013, 07:08 PM
The trick would be to make an impulse gun like was mentioned earlier, similar to a Paslode. Pure oxygen and propane make a heck of a propellant, stoichiometric proportions could be accumulated and stored if not pressurized (bladder system?) per torch method and the combustion chamber purged with the mix after the projectile is breech-seated. The only issue would be spontaneous ignition from contact with oil, lube, or grease. Air/propane mix, obviously, would be much safer, and might be useful in a bottleneck-style combustion chamber to give a little longer impulse time and keep barrel pressure up.

This would still be a firearm, but isn't it still legal to make one's own firearm provided it is never transferred or sold?

Gear

John Taylor
10-27-2013, 08:39 AM
.

This would still be a firearm, but isn't it still legal to make one's own firearm provided it is never transferred or sold?

Gear

Most laws say a firearm uses fixed ammo, a cartridge containing powder, bullet and primer. The wording in some states has been changed to include antiques that use fixed ammo so rifles made before 1899 are now called firearms. Seems this was done under the radar.

Garyshome
10-27-2013, 08:56 AM
I only have 150' of air hose, so I can use it in my yard but not much further.

grizzlyadams
11-04-2013, 01:43 PM
most of the more powerful springers already diesel to some extent. back in the day. HW made a gun that had an ether injector. the problem with dieseling all the time, is it eats the synthetic piston seals up really quick.

Silver Eagle
11-04-2013, 10:54 PM
Keeping the velocity consistent would be a significant hurdle. Also, combustion requires fuel, oxygen and heat. Heat in a diesel operations would be provided for by piston compression. Fuel could be added in via injector or manual source. Oxygen might be the problem as the chamber would need to be vented and refreshed with fresh air after every shot.
Wear and tear of parts (seals, springs, etc.) would also be a major stumbling block. A number of spring piston rifles have had the seals destroyed after one or two detonations. These can occur by using the wrong lube on the chamber or by dry firing.
Have no idea what the BATFE would consider such an arm as it would be considered a "fuel" burner by definition.

Driver man
11-04-2013, 11:05 PM
As a kid I used to put a squirt of ether in the dianna mk4 airpistol i had. Used to blow it open sometimes but wow. Learnt how to make leather piston seals,spring compressers and bandages.

fastfire
11-06-2013, 01:23 PM
Yea it would down right suck for your diesel to gell up while you had your sights on that trophy buck. lol

We used accetylene and oxygen in them potato guns. lol

Years ago I made a accetylene and oxygen cannon for golf balls.... Mother Mary did they go fast..........

Speedo66
11-07-2013, 09:32 PM
Those "Big Bang" cannons sold in comic books used a calcium carbide/acetylene charge for their bang (calcium carbide + water=acetylene). Was there a way you could fire a projectile from them?

LeftyDon
11-15-2013, 10:31 PM
Those "Big Bang" cannons sold in comic books used a calcium carbide/acetylene charge for their bang (calcium carbide + water=acetylene). Was there a way you could fire a projectile from them?

Heck yes, we used to fire small pine cones, before fully open, from ours.

Mondray
04-19-2019, 12:38 PM
You Gize need to think Outside The Box, on Diesel Powered Rifle, you need to use a Glow Plugs, plus a Mechanical Diesel Injector.

country gent
04-19-2019, 02:13 PM
I have a buddy who diesels his spring cocker air gun. he packs a pellets skirt with Vaseline and fires it the compression ignites the vaseleine or mix he uses and gains him another 200 fps or so. I have heard of lighter fluid being used also for this. All admit its hard or the air rifle and greatly lowers its life.

A rifle could be built to do this and some in the past have been close, caseless ammo is one that comes to mind. a simple chamber with throat for the bullet to be seated into to seal chamber. A known space for the desired liquid and amount ( diesel fuel, Vaseline, lighter fluid). Then the compressed air charge or piston to get the 25-1 or so compression to fire it. I would think ignition with some base materials would be iffy and lock time would be slow.

AllanD
04-19-2019, 02:24 PM
OK guys,,,, The German Company Weihrauch who makes a lot of the good Spring Piston air guns once produced a version of the HW35 in .22 cal. know as the Barakuda.

http://www.pyramydair.com/blog/2006/05/weihrauch-barakuda-el54-ether.html

It was a normal HW35 in .22 cal. with an attachment that dispensed a drop of ether behind the pellet just before you fired the gun.

It produced .22 LR velocities from a gun that normally had 580 fps velocities in .22 cal.

So the short answer to the OP's question is . It was done in the late 60's early 70's.

They used Ether as the propellant due to its low flash point. IE the compression of the piston in the gun easily ignited the ether.

On a side note: There are Diesel Model Airplane Engines that have been around from the beginning. In fact most European Model Airplane Engines are Diesels.

They run on a fuel made of 33% kerosene, 33% Ether, and 33% Castor oil.+ some traces of some additives I have forgotten.

These engines are compression ignition engines and the combustion chamber is adjustable to cope with ignition timing and actual compression. They end up running in the 9:1 Comp ratio regime due to the inclusion of Ether in the fuel which lowers the flash point of the fuel mixture.

These engines are about 1.5 times the horsepower of a similar displacement Alcohol/Nitro fueled Glow Ignition style engine common here in the US. This mainly due to the higher density of the Kerosene. The ether is in there to start the fire easier.

This is also the reason why diesel engines produce more power than gas motors. Normal gasoline is around 10,000 BTU's per pound. Diesel fuel is 18,000 BTU/LB. Kerosene is even higher and that's why they use it as Jet fuel.

It is easy to see this if you look at the structure of the individual molecules of fuel. Natural Gas is CH4 "Methane" that is one carbon atom with 4 hydrogen atoms surrounding it. Gasoline is 6,7,or8 carbons lined up IE: Sextane, Septane /Heptane, Octane, with 14, 16 or 18 H's around. Diesel is 12,13,14 carbons and 26,28,30 H's and kerosene is 20-40 C's in a row, with 42- 82 H's !

It is easier to see how these denser fuels have more poop. This is why 75% of the cars in Europe are diesel powered. VW Jetta wagons have a 2.0 L engine that produces 140HP and gets 42+ mpg. A new 2.8L BMW engine in the 3 series cars is 280HP and yields 45 mpg. Looking at one of those later today or tomorrow.

This is why I own diesel powered vehicles.

Randy


Actually alcohol free Gasoline is about 22,000BTU/lb.
the difference is that gasoline under compression burns much faster and less "progressively" than Diesel fuel, plus Diesel is added progressively to an already ingnited cylinder. Diesels make more torque than gasoline engines because of their longer Stroke, not because of any inherent characteristic of the fuel
Add to this discussion that the new crop of "Gasoline direct injected engines" are erasing the advantages of diesel engines.

The difference between gasoline and alcohol is rather profound Hydrocarbons such as Propane. Gasoline, Kerosene and Diesel all have near enough to 20,000BTU/Lb to not make a difference while alcohols have 10,000-12,000BTU/LB

NTW, diesels DO NOT MAKE MORE POWER than Gasoline engine, often for a given displacement that produce around 60% as much, but they do for a given displacement produce more torque, but you are "All wet" on your quotes of chemical energy contained in the fuel...

To get this back to firearms related do you know what the specific energy of our favorite propellants are? GOOD Black powder is about 300,000BTU/lb, and nitroglycerine is closer to 1,300,000BTU/lb, Nitrocellulose lies at about 700,000BTU/lb



BTW, what most people think of as "Ether" (Aerosol "Starting Fluid") isn't
Aerosol starting fluid is usually a mix of "Pentane" (the five carbon hydrocarbon) with a mix of Butane (Four carbon) and propane (Three carbon) as "propellant"

1066
04-19-2019, 10:38 PM
The old Webley Mk 2 air rifle from the 1930's used proper little bronze split piston rings - that would solve your seal burning problem. I would think a much smaller piston/cylinder would be better. Compare the swept volume of a modern spring airgun at around 6 cube inches to a model plane engine at about .3 cube.
Fuel induction could be like a two stroke engine, on the cocking stroke a loading tap opens ( as on older BSA Airsporter underlevers) this will create a vacuum as the piston is drawn back until it uncovers the fuel induction port. A simple model plane engine carburettor would meter the fuel.

john.k
04-20-2019, 03:29 AM
My can of starter fluid states it contains 25% ether ,rest as petroleum fractions...........anyhoo,you might be better off with something like nitrobenzine ,which is available for model planes .....another used is isopropyl nitrate ,used in diesel fuel at sub zero temperatures.(jet kero actually,diesel is solid at sub zero temps).

john.k
04-20-2019, 03:31 AM
if you want see something like a diesel airgun.a diesel piledriver works similarly,but weighs many tons,so the size of components isnt a problem.

RED BEAR
04-20-2019, 09:26 AM
I have seen and read things on both sides so not sure who is right. Some say the increase in performance is astounding others say it is next to nothing. Heard it will destroy seals others say its not a problem. every one i say used something along the line of Vaseline. I would love for someone who actually does it to post results velocity increase what caliber and gun ect.

GhostHawk
04-20-2019, 09:43 AM
IMO silvereagle nailed it. Trouble is consistency. Getting the exact same pressure, fuel, temp the same every time is going to be tough. Change any variable by any significant amount and you could be changing your trajectory.

Powder is easier.

1066
04-20-2019, 10:49 AM
I have seen and read things on both sides so not sure who is right. Some say the increase in performance is astounding others say it is next to nothing. Heard it will destroy seals others say its not a problem. every one i say used something along the line of Vaseline. I would love for someone who actually does it to post results velocity increase what caliber and gun ect.

Personally I don't think there's any future in it - other than an interesting and challenging project. - What exactly would be the aim?
More power? Modern spring air guns are quite commonly available in the 15-20ftlb range, PCP's anything from 6 to 100ftlb where you are firmly into .22lr territory.

You certainly won't gain any accuracy - modern air rifles are just so consistent in power, a spread of 5fps is not unusual.

The concept would fall into various restrictions - seen as a firearm in many places, if not currently it's coming.

If you're looking for something to bridge the gap between a standard air rifle and a .22 short you could very easily convert a fairly low powered air rifle to shoot .22 button blanks which will drive a heavy
pellet up to 20 ftlbs.

That's no to say it's not an interesting project for it's own sake.

longbow
04-20-2019, 11:52 AM
Hah! I missed this thread when it started way back!

I too used to put a drop or two of light oil in my old spring cocker and got fairly dependable dieseling. I'm sure velocities weren't consistent but when it went there was a sharper crack and much more impact evident.

There was a commercial version of a diesel gun I saw and almost bought back in the 70's. ! don't recall the manufacturer but thinking Diana or Weihrauch... or at least European. It was a modified spring gun with a manual ether injector on it. It had a small cylinder on the right side that you put ether into and a little manual piston put a bit of ether into the compression chamber when operated. Seemed like an interesting idea but more trouble than it was worth. And as said, modern air guns are miles ahead of air guns then so little point now I think.

Hah! There we go: https://www.pyramydair.com/blog/2006/05/weihrauch-barakuda-el54-ether-injection-air-rifle/ my memory isn't as bad as I thought! These were apparently in production for quite some time.

Longbow

john.k
04-21-2019, 10:35 PM
The error in using any kind of spring gun is that an increase of pressure acts against the pellet and the piston to retard ,or actually drive back the piston......thereby acting as a sort of safety valve..................so ,for the system to work ,at least you would need some kind of double diameter piston setup,so that the increased pressure due to fuel ignition did not act on the full area of the main piston,but on a reduced area of the smaller piston.....and as mentioned this makes the gun a firearm,and restricts sales ,whereas airguns can be sold freely in most parts of the world............If firearms are OK,then why not a much cheaper .22 rimfire.

Multigunner
04-22-2019, 01:43 AM
There was a German diesel airgun marketed decades ago that used glass ampules of veterinarian grade ether, which apparently was easy to buy in Europe, probably from a farmers co-op.
I think they loaded the ampule into a chamber and it broke as the lid was screwed down tight. Each ampule held enough for several shots.

If a fuel is used that may not fire off easily in cold weather, or gave inconsistent velocities when dieseling, I would suggest a piezo electric ignition that tripped as the piston moved forwards.
It would also allow firing at a lower compression ratio, thus lighter spring loading.
A balance might then be achieved where the piston was blown back to self cock with each shot.

W.R.Buchanan
04-26-2019, 09:37 PM
LB: that little Barakuda attachment on the side of the HW35 is worth more than the gun itself now. highly sought after by Airgun Collectors.

The seals that blow out on these guns are not the piston seals. The guns in question including both my 1978 guns are leather.

The seal that blows out is the breech seal,which is essentially a Teflon O ring. I have a drawing somewhere and have made them while waiting for replacements. Not hard to make. I have also used Delrin.

Randy

Ozark mike
04-26-2019, 10:00 PM
Potato gun well kinda runs on ether or any flammable vapor I guess we'll call it the Otto gun haha or maybe a nuclear powered rail gun. I guess anything is possible

AllanD
06-13-2019, 03:03 AM
Walgren's drug store sells 91% rubbing alcohol. It burns fairly good.

You can increase alcohol content by placing a bottle in a freezer for several days, water will settle out and freeze into a layer of ice at the bottom of the bottle, what you pour off the top will be nearly pure alcohol.
I've used a similar method to remove water from heating kerosene . I set a plastic container outside for several days in freezing weather till ice forms at the bottom. What rises to the top burns clean and bright in my oil lamps.


It would be much easier to buy dry gas at the auto parts

I have tried experimenting with adding a tiny amount of Kerosene to the back of the pellet with an insulin syringe (my father's), but I quickly switched to applying lighter fluid and using a Q-tip to apply the correct amount....

Too much creates a soot fouled barrel the exact right amount produces a sonic crack and some barrel leading, but as my RWS45 177 rifle would already penetrate a squirrel diagonally with Beeman Magnum pellets out past 50 yards and the fact that about half the pellets had their skirts turned inside out or otherwise disintegrate at the muzzle, I really didn't see the point in continuing..

Because a skirt-less pellet rarely flies true.