Hello together,
here are the pics of the MG 42 chamber.
Best regards,
Alexander
MG42 Propane Gun Build
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AlexHH
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AlexHH
Hello guys a short explanation of the chamber...
In short, the inside of the chamber is a combination of the 18mm hole drilled for threading in the G ½“ (Withworth BSP) water pipe barrel and the 12,8 mm hole for the M14x1.25 spark plug. The trick is that the spark plug hole goes in off-center and lower and they overlap about 12mm to make a bigger inside area.
This gives room to drill the holes for the M5 pipe threads to take the compression fittings for the 4 mm copper tubing. I use to bring the gas in.
I set an angle that will bring the gas jet holes into the chamber and try to get them to come through as close to the sides if the inside chamber wall as possible. I mill a matching angle flat on each side of the top of the chamber block then drill through the gas inlet 4mm holes with a 2,5 mm drill and tap the outside wall for M3 screws. This plugs the hole as you guessed and the flat gives a good seal for the screw to seat against.
I drill the 2,5 hole all the way through and just start a hole on the other side of the 4 mm holes to drill with a 1,5 mm diameter that creates the gas “jetâ€. These come out in front of the spark plug and are offset by about 2,5 mm for better mixing.
That’s it….
I hope this gives an idea of the chamber.
Alexander
In short, the inside of the chamber is a combination of the 18mm hole drilled for threading in the G ½“ (Withworth BSP) water pipe barrel and the 12,8 mm hole for the M14x1.25 spark plug. The trick is that the spark plug hole goes in off-center and lower and they overlap about 12mm to make a bigger inside area.
This gives room to drill the holes for the M5 pipe threads to take the compression fittings for the 4 mm copper tubing. I use to bring the gas in.
I set an angle that will bring the gas jet holes into the chamber and try to get them to come through as close to the sides if the inside chamber wall as possible. I mill a matching angle flat on each side of the top of the chamber block then drill through the gas inlet 4mm holes with a 2,5 mm drill and tap the outside wall for M3 screws. This plugs the hole as you guessed and the flat gives a good seal for the screw to seat against.
I drill the 2,5 hole all the way through and just start a hole on the other side of the 4 mm holes to drill with a 1,5 mm diameter that creates the gas “jetâ€. These come out in front of the spark plug and are offset by about 2,5 mm for better mixing.
That’s it….
I hope this gives an idea of the chamber.
Alexander
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88comm
- Stabshauptmann
- Posts: 177
- Joined: Mon Jun 06, 2005 7:31 pm
- Location: South Central Pennsylvania
Interesting design and 100% feasible for the first shot. What is the plan for purging the chamber of exhaust gases?
My experience:
I have built a cannon that uses oxygen and acetylene. 8" diameter by 8' long. A touch hole at the breech, plastic bag over the muzzle while charging. Charge through the touch hole with the welding tip of the torch. #3 tip, 30 PSI on the gas, about 15 seconds. Then light the torch and sweep it over the touch hole. Impressive.
Anyway (my point) a second charge does not repeat the same as the first because the barrel has not been cleared of exhaust gases from the first time.
A few thoughts on this -
1. Have some way to open the breech to clear the exhaust after each shot. Manually doing this would defeat the "automatic" part of a dummy machine gun, unless you -
2. have some kind of flap/check valve at the breech that would do the job automatically.
Once the charge exploded, it must exit the muzzle of the barrel, if there was a way for the breech to open (metal flap valve) after the explosion, the gas moving toward the muzzle would pull fresh air in through the breech valve. Then it is ready for re-charge and repeat.
Would it work? Google search "pulse jet" and "V-1" to see how it works.
3. Another option would be to lengthen the charge time for the oxygen, having it purge the chamber before the introduction of the fuel. Same result, different method of getting there.
Chris
My experience:
I have built a cannon that uses oxygen and acetylene. 8" diameter by 8' long. A touch hole at the breech, plastic bag over the muzzle while charging. Charge through the touch hole with the welding tip of the torch. #3 tip, 30 PSI on the gas, about 15 seconds. Then light the torch and sweep it over the touch hole. Impressive.
Anyway (my point) a second charge does not repeat the same as the first because the barrel has not been cleared of exhaust gases from the first time.
A few thoughts on this -
1. Have some way to open the breech to clear the exhaust after each shot. Manually doing this would defeat the "automatic" part of a dummy machine gun, unless you -
2. have some kind of flap/check valve at the breech that would do the job automatically.
Once the charge exploded, it must exit the muzzle of the barrel, if there was a way for the breech to open (metal flap valve) after the explosion, the gas moving toward the muzzle would pull fresh air in through the breech valve. Then it is ready for re-charge and repeat.
Would it work? Google search "pulse jet" and "V-1" to see how it works.
3. Another option would be to lengthen the charge time for the oxygen, having it purge the chamber before the introduction of the fuel. Same result, different method of getting there.
Chris
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AlexHH
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88comm
- Stabshauptmann
- Posts: 177
- Joined: Mon Jun 06, 2005 7:31 pm
- Location: South Central Pennsylvania
Alex - you may indeed be right. On the scale of my cannon, an exhaust system is a requirement. A barrel that is 6mm in diameter is a different situation.
No hostility intended - I want you to educate me on this issue. Good chamber design, by the way.
Completely off topic - Alex, have you been to Des Duetsches Museum in Munchen?
An incredible place. Not to be missed.
Bis spater...
Chris
No hostility intended - I want you to educate me on this issue. Good chamber design, by the way.
Completely off topic - Alex, have you been to Des Duetsches Museum in Munchen?
An incredible place. Not to be missed.
Bis spater...
Chris
Exhaust-ports are not a requirement in a "Gas"/Propane-Gun. You are mixing "Oxygen" with the Propane....."fresh-air" introduced into the chamber is not a requirement (nor wanted) as it does change the mixture and the possibilities of the "flap" remaining open (safety) may result in a failure at a later date (?).
Basically, we are not looking at "Artillery" Howitzers nor "Guns"............some of which require a "Bore-Evacquator" so that the poisonous-gases from firing are re-directed out the muzzle so that the crew in a Self-Propelled-Howitzer with closed crew areas (such as the M109/M109A1 series) can breath during firing/operation of the Howitzer.
My suggestion at this point would be to go back over to the FJ Web-Page in Washington-State and re-read some of the things that they did....and then try to keep the "system" as simple as possible.
Problems to overcome and "questions" are:
1: Size of the tanks/containers for fuel and Oxygen....can they be bought/located in a smaller-design/shape (?).
2: "Propane" (if I remember correctly) will come in a liquid-form.....it needs time to "warm-up" a little to turn into a gas. This is one of the reasons (I beleive) that the photos over on their web-page shows insulation around the tanks. It is addressed as one of their comments also on either their web-page.....or during an e-mail conversation with the circuit-board/kit-guy (Steve ____(?))...that is if you adjust the firing too fast......the "systems" does not have enough "charge-time" and sounds weaker. This is also another reason that they went to a larger ID (Inside-Diameter) on the barrel....(Pipe) so that the sound would be better.
Question here would be was their larger "back-pack" propane-tank required for better evaporation at the RPMs that they wanted to fire (?).
3: Correct-mixture........for the RPMs that you want to fire. Charge-time is critical....as is the pressure/valve-adjustments.
4: Again, with the Propane coming in liquid-form.......Do the tanks require that they be oriented with the valve facing up (?)
5: Possibly "re-look" at the location of the "Spark-plug" vs. gas-ports on their working-design/chamber-area........this may shed some light on these questions. Possibly e-mail them and ask questions (?).
6: Has anyone located a source for the "circuit-boards" and other components (?) (POC/address (?).....Prices (?).
This is still a great "Thread" and badly needed for those reenactors that live in "Non-Class III" States.
Should it "warrent" its own section (?)....and could it be broken down into weapon-builds/systems.....with a partial area on suppliers, parts, adjustments, "builds".....and (?).
Regards, RichardS in MI.
Blanksguy2001@chartermi.net
Basically, we are not looking at "Artillery" Howitzers nor "Guns"............some of which require a "Bore-Evacquator" so that the poisonous-gases from firing are re-directed out the muzzle so that the crew in a Self-Propelled-Howitzer with closed crew areas (such as the M109/M109A1 series) can breath during firing/operation of the Howitzer.
My suggestion at this point would be to go back over to the FJ Web-Page in Washington-State and re-read some of the things that they did....and then try to keep the "system" as simple as possible.
Problems to overcome and "questions" are:
1: Size of the tanks/containers for fuel and Oxygen....can they be bought/located in a smaller-design/shape (?).
2: "Propane" (if I remember correctly) will come in a liquid-form.....it needs time to "warm-up" a little to turn into a gas. This is one of the reasons (I beleive) that the photos over on their web-page shows insulation around the tanks. It is addressed as one of their comments also on either their web-page.....or during an e-mail conversation with the circuit-board/kit-guy (Steve ____(?))...that is if you adjust the firing too fast......the "systems" does not have enough "charge-time" and sounds weaker. This is also another reason that they went to a larger ID (Inside-Diameter) on the barrel....(Pipe) so that the sound would be better.
Question here would be was their larger "back-pack" propane-tank required for better evaporation at the RPMs that they wanted to fire (?).
3: Correct-mixture........for the RPMs that you want to fire. Charge-time is critical....as is the pressure/valve-adjustments.
4: Again, with the Propane coming in liquid-form.......Do the tanks require that they be oriented with the valve facing up (?)
5: Possibly "re-look" at the location of the "Spark-plug" vs. gas-ports on their working-design/chamber-area........this may shed some light on these questions. Possibly e-mail them and ask questions (?).
6: Has anyone located a source for the "circuit-boards" and other components (?) (POC/address (?).....Prices (?).
This is still a great "Thread" and badly needed for those reenactors that live in "Non-Class III" States.
Should it "warrent" its own section (?)....and could it be broken down into weapon-builds/systems.....with a partial area on suppliers, parts, adjustments, "builds".....and (?).
Regards, RichardS in MI.
Blanksguy2001@chartermi.net
Richard,
You are 100% correct on all points.
I'd love to see a section on the propane builds, too. That way there would be more space for all of us to post our builds and designs and experiments with miniaturization.
I think I may have posted it before, but the address for the fellow who sells the circuit board controller (the ONLY person as far as I've been able to determine) is:
Steve L. Smith
P.O. Box 158
Barnhart, Mo. 63012 or steveleesmith@hotmail.com
Price is $160 plus shipping, and includes the controller w/adjustable rate of fire, two gas solenoids, assembly instructions, and a list of needed parts.
(By the way, Richard, thanks for responding about the blanks. I'll get off my lazy butt and check with the other guys to see if they need some, too, then get an order off to you. I found enough ammo for the next reenactment, so reordering hasn't been on the top of the list. It'll go to the Priority List when I'm out and need you get them to me with only 24 hours left before the next battle!!!!
)
Garry
You are 100% correct on all points.
I'd love to see a section on the propane builds, too. That way there would be more space for all of us to post our builds and designs and experiments with miniaturization.
I think I may have posted it before, but the address for the fellow who sells the circuit board controller (the ONLY person as far as I've been able to determine) is:
Steve L. Smith
P.O. Box 158
Barnhart, Mo. 63012 or steveleesmith@hotmail.com
Price is $160 plus shipping, and includes the controller w/adjustable rate of fire, two gas solenoids, assembly instructions, and a list of needed parts.
(By the way, Richard, thanks for responding about the blanks. I'll get off my lazy butt and check with the other guys to see if they need some, too, then get an order off to you. I found enough ammo for the next reenactment, so reordering hasn't been on the top of the list. It'll go to the Priority List when I'm out and need you get them to me with only 24 hours left before the next battle!!!!
)Garry
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bigsexy7882
- Obergefreiter
- Posts: 24
- Joined: Sun Mar 25, 2007 12:19 am
- Location: southern illinois,usa
heres a vid of a gas MG42, feed cover open and shows the guts. might be good for people trying to figure out how to lay things out.
http://www.youtube.com/watch?v=HfD1JaXnsgc
hope this can help someone.
http://www.youtube.com/watch?v=HfD1JaXnsgc
hope this can help someone.
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AlexHH
Hello Richard,
I think I have some answers to your questions:
Re. 1: A good size is a 2 litre O2 bottle and a 425g propane bottle if you simulate a lMG.
Re. 2: The insulation is not a insulation, it is only a foam which enables the gunner to carry around the bottels safely.
Re. 3: The details can you find within the documentation of Steve Smiths kit
Re. 4: The best you can do is to have the valves upright
Re. 5: The basics of chamber design are also within the documentation of Steve Smith
Re. 6: As far as I know, Steve is the only one who sells the electronic. There are different companies out ther who are selling gas gun complete packages with chamber, elcectronc, valves, solenoid valves etc - A kit cost (without gas bottles) arround 600 USD
Alexander
I think I have some answers to your questions:
Re. 1: A good size is a 2 litre O2 bottle and a 425g propane bottle if you simulate a lMG.
Re. 2: The insulation is not a insulation, it is only a foam which enables the gunner to carry around the bottels safely.
Re. 3: The details can you find within the documentation of Steve Smiths kit
Re. 4: The best you can do is to have the valves upright
Re. 5: The basics of chamber design are also within the documentation of Steve Smith
Re. 6: As far as I know, Steve is the only one who sells the electronic. There are different companies out ther who are selling gas gun complete packages with chamber, elcectronc, valves, solenoid valves etc - A kit cost (without gas bottles) arround 600 USD
Alexander
They use a couple of these at the WWI Reenactment that is held in Newvile, PA .
They set the Russian "Maxim" up with a different "electric-board" that fires at a slower rate to simulate the Maxim's 450-500 RPM.
If I remember correctly...."Steve" sells two different "Boards" that allow you some adjustment......but one to simulate slower-MGs such as the Maxims.......and one for faster MGs such as the MG42 or MG34.
I do know that they will fire for some time (I do not know the length of time as it would depend on "tank-size" and "fill-pressure" allowed for that tank I am guessing)......and that they were using those cheap (non-refillable) blue-propane bottles that you can pick up at most hardware-stores.
You can tell when they are empty.....the gun starts sounding like someone is blowing a "duck-call"....but shorter and faster.
If someone gets one of these from "Steve" (or e-mails him) ask if we can post the instruction-sheet that comes with his kit. It will get more individuals interested in building these on their own....and will help "Steve" to sell more of them.
Also, "invite" him over.....he has a lot of knowledge...and could help with detailed adjustments.
Regards, RichardS in MI.
Blanksguy2001@chartermi.net
They set the Russian "Maxim" up with a different "electric-board" that fires at a slower rate to simulate the Maxim's 450-500 RPM.
If I remember correctly...."Steve" sells two different "Boards" that allow you some adjustment......but one to simulate slower-MGs such as the Maxims.......and one for faster MGs such as the MG42 or MG34.
I do know that they will fire for some time (I do not know the length of time as it would depend on "tank-size" and "fill-pressure" allowed for that tank I am guessing)......and that they were using those cheap (non-refillable) blue-propane bottles that you can pick up at most hardware-stores.
You can tell when they are empty.....the gun starts sounding like someone is blowing a "duck-call"....but shorter and faster.
If someone gets one of these from "Steve" (or e-mails him) ask if we can post the instruction-sheet that comes with his kit. It will get more individuals interested in building these on their own....and will help "Steve" to sell more of them.
Also, "invite" him over.....he has a lot of knowledge...and could help with detailed adjustments.
Regards, RichardS in MI.
Blanksguy2001@chartermi.net
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AlexHH
Re: MG42 Propane Gun Build
My much-too-short summer with my grandkids is drawing to a close 
, and the only consolation is that the fire-control circuit board -- identical to the one pictured above -- came in the mail a couple of weeks ago. Now I can bring the propane gun project back on line.
This prototype belongs to my best friend, and we've decided to assemble it as a "standard" gun using all the standard and tried-and-true techniques that are hallmarks of most of the propane guns currently on the field. We've decided to go in this direction so that we can use this gun as a test mule for all the other upgrades and modifications we want to incorporate on the second gun.
We're in the process of finding a machinist to build the combustion chamber for us. Once that is done, I'll resume posting pics and text of the build and upcoming experiments in design.
GeeDeeEmm
, and the only consolation is that the fire-control circuit board -- identical to the one pictured above -- came in the mail a couple of weeks ago. Now I can bring the propane gun project back on line.This prototype belongs to my best friend, and we've decided to assemble it as a "standard" gun using all the standard and tried-and-true techniques that are hallmarks of most of the propane guns currently on the field. We've decided to go in this direction so that we can use this gun as a test mule for all the other upgrades and modifications we want to incorporate on the second gun.
We're in the process of finding a machinist to build the combustion chamber for us. Once that is done, I'll resume posting pics and text of the build and upcoming experiments in design.
GeeDeeEmm
" The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government . . . . When the people fear their government there is tyranny, when the government fear the people, there is liberty." Thomas Jefferson
Re: MG42 Propane Gun Build
Garry-sorry to hear the grandkids are leaving so soon-I know how much they mean to you! Glad to see you are back to work on the gas-gun.Keep us posted. 
---bil
---bil"I dream of a world where I can buy alcohol,tobacco and firearms from the same drive-up window,and use them all on the way home from work!" Dogbert
Re: MG42 Propane Gun Build
Odd . . . .
Last night I made a post here updating the gas gun project, today it's gone! Wierd.
To recap, we had our annual reenactment this weekend, which meant that I had to finish the gun in three days. No time for photos. Since the previous photos were all deleted with the site change, I've decided to just reconstruct the entire series when I start on another propane gun. (Soon as the new shop is finished.)
The gun works like a charm. LOUD!! Louder than any other propane gun I've heard, and with a much deeper tone. I gambled that enlarging the expansion chamber and using a thin-walled, 3/4" stainless pipe for a barrel would lower the tone and increase the dB level, and it did, to the max. My ears are still ringing. Got a ton of compliments.
Anyway, here's a photo of the finished result. Should have taken the shot while it rattled off a long burst -- the flame pattern is just awesome.
GeeDeeEmm
Last night I made a post here updating the gas gun project, today it's gone! Wierd.
To recap, we had our annual reenactment this weekend, which meant that I had to finish the gun in three days. No time for photos. Since the previous photos were all deleted with the site change, I've decided to just reconstruct the entire series when I start on another propane gun. (Soon as the new shop is finished.)
The gun works like a charm. LOUD!! Louder than any other propane gun I've heard, and with a much deeper tone. I gambled that enlarging the expansion chamber and using a thin-walled, 3/4" stainless pipe for a barrel would lower the tone and increase the dB level, and it did, to the max. My ears are still ringing. Got a ton of compliments.
Anyway, here's a photo of the finished result. Should have taken the shot while it rattled off a long burst -- the flame pattern is just awesome.
GeeDeeEmm
- Attachments
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" The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government . . . . When the people fear their government there is tyranny, when the government fear the people, there is liberty." Thomas Jefferson
Re: MG42 Propane Gun Build
Glad to hear it came out so good!Are you sure about the other post-memory is the second thing to go at our age!! ---bil
---bil"I dream of a world where I can buy alcohol,tobacco and firearms from the same drive-up window,and use them all on the way home from work!" Dogbert