General Discussions
This is the place to discuss general issues related to the U-boat war or the war at sea in WWII.
Re: Information on G7a
Posted by:
Natter_not logged in
()
Date: March 21, 2013 10:46AM
Sorry for a late reply (there should be an option for getting an e-mail when new posts occur here...).
maxine Wrote:
-------------------------------------------------------
> Yes thank you I should have explained that I
> already got that far. After careful inspection
> internally, some cleaning and lubrication it
> turned over OK by hand. The air inlet, combustion
> pot and associated lines were thorouchly
> borescoped and look good as do the cylinders,
> valves etc. In fact so far there is little sign
> of any corrosion or damage anywhere internally.
Sounds good. I don't know the history of this engine, but we used the G7a (modified with wire-guidance, designated "T1 mod1") regulary until 1999 in the RNoN, and they performed perfectly mechanically up to the end. In fact, the only reason to finally phase out the torpedo was concerns about the air-tanks, which was showing increased sign of corrosion and as such deemed unsafe for use.
> So as a next step I machined an adapter so I could
> introduce air pressure into the combustion pot.
> The adapter was threaded in to the top of the
> combustion chamber where the igniter goes. I
> started with just 10 psi and it rolled over one
> piston stroke. With a little help on the output
> shaft it would roll over one stroke at a time. At
> 25 psi it turned over slowly hesitating for a few
> seconds at each piston stroke. At 45 psi it runs
> slowly but continuously.
This could vary from torpedo to torpedo, but the engine could be hard to get moving, and often required a little extra pressure (and a helpfull nod with a wooden beam to the propeller...). That was for engines being used regulary though - it seems your engine must be in a good state if you got it moving that easy :-)
When running the engine for maintenance-purposes, pressure was in fact applied to the combustion-chamber in a similar way (although via the water-compartment), so you have done it almost "by the book". I don't have the manuals at hand now, as I'm at work, but I think 45psi is a little lower then the pressure normally used for the maintenance-runs (I'll check). For 30kn running, the pressure would be much higher - above 300psi if I remember correctly (that's in to the combustion-chamber, before adding the steam).
I don't remember the values for 40-44kn, but probably around 500psi for the latter (I'll check).
> I thank you for the reminder about pressurized
> gasses. I should have stated that I am a Chemical
> Engineer with 40 years experience in petrochemical
> manufacturing and am well aware of pressurized gas
> dangers. In my job I deal with high pressure and
> highly volatile gasses of all sorts as well as
> superheated steam boilers and and turbines that
> generate/use steam up to 2500 psi.
Good, then you know what you're doing :-)
> We do indeed intend to fire the engine assuming
> everything checks out good in the end physically
> and assuming I can find enough technical detail to
> convince myself it is safe.
Well.. as I said: I wouldn't recommend it, but you should at least prepare properly. Important issues: Cooling for the engine if you're running it more than a minute. Lubrication. Physically securing (VERY important: I can assure you, it will not stand still! (we had a torpedo being started by accident (don't ask) before it was loaded into the tube once, and that was no joy, even though we got it shut off very quickly.
> So an example of the kind of information I would
> be looking for would be as follows: It appears
> that the high pressure air supply from the air
> flask attaches at the engine to a pressure
> regulating valve.
First, there is the starter-valve operated by the cock being pulled back by a lever in the tube, before the air passes the high-pressure regulator. A further two regulators are in play before the air is delivered to the combustion-chamber.
> The discharge from that
> regulating valve then feeds the combustion chamber
> at the burner. What pressure does the regulating
> system reduce the air pressure to as it goes to
> the burner. I have lots more technical questions
> like that example and was hoping to find a
> knowledgeable source.
I can provide more details of the pressures, drawings etc. if you get in touch by mail.
maxine Wrote:
-------------------------------------------------------
> Yes thank you I should have explained that I
> already got that far. After careful inspection
> internally, some cleaning and lubrication it
> turned over OK by hand. The air inlet, combustion
> pot and associated lines were thorouchly
> borescoped and look good as do the cylinders,
> valves etc. In fact so far there is little sign
> of any corrosion or damage anywhere internally.
Sounds good. I don't know the history of this engine, but we used the G7a (modified with wire-guidance, designated "T1 mod1") regulary until 1999 in the RNoN, and they performed perfectly mechanically up to the end. In fact, the only reason to finally phase out the torpedo was concerns about the air-tanks, which was showing increased sign of corrosion and as such deemed unsafe for use.
> So as a next step I machined an adapter so I could
> introduce air pressure into the combustion pot.
> The adapter was threaded in to the top of the
> combustion chamber where the igniter goes. I
> started with just 10 psi and it rolled over one
> piston stroke. With a little help on the output
> shaft it would roll over one stroke at a time. At
> 25 psi it turned over slowly hesitating for a few
> seconds at each piston stroke. At 45 psi it runs
> slowly but continuously.
This could vary from torpedo to torpedo, but the engine could be hard to get moving, and often required a little extra pressure (and a helpfull nod with a wooden beam to the propeller...). That was for engines being used regulary though - it seems your engine must be in a good state if you got it moving that easy :-)
When running the engine for maintenance-purposes, pressure was in fact applied to the combustion-chamber in a similar way (although via the water-compartment), so you have done it almost "by the book". I don't have the manuals at hand now, as I'm at work, but I think 45psi is a little lower then the pressure normally used for the maintenance-runs (I'll check). For 30kn running, the pressure would be much higher - above 300psi if I remember correctly (that's in to the combustion-chamber, before adding the steam).
I don't remember the values for 40-44kn, but probably around 500psi for the latter (I'll check).
> I thank you for the reminder about pressurized
> gasses. I should have stated that I am a Chemical
> Engineer with 40 years experience in petrochemical
> manufacturing and am well aware of pressurized gas
> dangers. In my job I deal with high pressure and
> highly volatile gasses of all sorts as well as
> superheated steam boilers and and turbines that
> generate/use steam up to 2500 psi.
Good, then you know what you're doing :-)
> We do indeed intend to fire the engine assuming
> everything checks out good in the end physically
> and assuming I can find enough technical detail to
> convince myself it is safe.
Well.. as I said: I wouldn't recommend it, but you should at least prepare properly. Important issues: Cooling for the engine if you're running it more than a minute. Lubrication. Physically securing (VERY important: I can assure you, it will not stand still! (we had a torpedo being started by accident (don't ask) before it was loaded into the tube once, and that was no joy, even though we got it shut off very quickly.
> So an example of the kind of information I would
> be looking for would be as follows: It appears
> that the high pressure air supply from the air
> flask attaches at the engine to a pressure
> regulating valve.
First, there is the starter-valve operated by the cock being pulled back by a lever in the tube, before the air passes the high-pressure regulator. A further two regulators are in play before the air is delivered to the combustion-chamber.
> The discharge from that
> regulating valve then feeds the combustion chamber
> at the burner. What pressure does the regulating
> system reduce the air pressure to as it goes to
> the burner. I have lots more technical questions
> like that example and was hoping to find a
> knowledgeable source.
I can provide more details of the pressures, drawings etc. if you get in touch by mail.
Subject | Written By | Posted |
---|---|---|
Information on G7a | maxine | 03/05/2013 06:18PM |
Re: Information on G7a | Natter | 03/05/2013 08:55PM |
Re: Information on G7a | maxine | 03/06/2013 01:56AM |
Re: Information on G7a | Natter_not logged in | 03/21/2013 10:46AM |