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FM/DM threads Everything about FM/DM in CoD |
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#1
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Merlin XII - wrong temperature limits!
I have a copy of the Spitfire II pilots notes which clearly states that a rad. temperature of 135 C and an oil temp. of 105 C was allowed for 5 minutes. However, in CloD, the engine dies in a matter of seconds once you go above 120 C (rad.) or 95 C (oil).
This is wrong, isn't it? Although I have no data about the Spitfire MkI I assume that the limits were the same. Then again , I might be wrong, but the Spitfire MkII is wrong, that's for sure. |
#2
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Merlin III
Amendment List No. 4 from November 1940 of AP 1590B Merlin II and III Aero-Engines has the following limits: Oil Type ... Specification D.T.D.109 Inlet oil temperatures Minimum for opening up ... 15°C Maximum for continious cruising ... 90° C. Maximum for climbing or 30 minute emergency (1 engine stopped : multi-engined aeroplanes) ... 90° C. Emergency maximum (5 minute limit) ... 95° C. Coolant Type ... Treated ethylene glycol: Specification D.T.D.344 Outlet temperatures Minimum for opening up ... 60° C. Maximum for cruising ... 95° C. Maximum for climbing and level flight (5 minutes limit) ... 120° C. Maximum for 1/2 hour emergency* ... 120° C. * Though not stated, I assume this limit is for multi-engined aeroplanes with one engine stopped, because there is no 30 minute emergency for single-engined aeroplanes. The initial limits (without amendment) stated in AP 1590B Merlin II and III Aero-Engines (October 1938, reprint October 1939) are the same. However, IIRC the Pilot's Notes Spitfire I of the Collector's Edition state higher limits. Merlin XII The Merlin XII employs a mixture of ethylene glycol and water instead of pure ethylene glycol. The Pilot's Notes here: http://www.scribd.com/doc/4598146/Pi...lin-XII-Engine state 120° C and 95° C for emergency (last page). However I know that there are 2 different versions of Pilot's Notes Spitfire IIA circulating, for example this one: http://www.scribd.com/doc/46069063/1...e-II-Aeroplane which states the 135° C and 105° C. Conclusion There are obviously different limit depending on the date of the publication. My conclusion is that the limits for Merlin III and Merlin XII were changed over the time. We have to take a close look at the Amendment Lists for every publication. Last edited by 41Sqn_Banks; 04-27-2011 at 06:56 AM. |
#3
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Impressive, thanks for the info!
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#4
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Quote:
However, Appendix VIII of the same book notes the Merlin IV as the lowest Mark number of Merlin designed for pressurised water cooling, and describes the Merlin XII as Quote:
Merlin III is listed as glycol cooled, as is Merlin V. However, in yet another list which forms part of the same appendix, Merlin V is given as "converted Merlin III" and as either pressure or glycol cooled. So, what I think was actually going on is this:
Note however, that this is nothing more than informed speculation. It is possible that the temperature reduction was independent of the change in coolant. However, my best guess would be that the original intention was to retain the 135ºC limit, but that the pressurisation required to prevent the system from boiling over was such that leaks became a problem (indeed, coolant leaks were quite well documented in this period) and therefore the degree of pressurisation and thus the maximum safe temperature was reduced at some point in order to mitigate the problem. Obviously the arguments for standardisation are pretty strong, so I imagine that once the decision was made to convert the installed fleet to pressurised water cooling with a 120ºC limit this new limit was imposed across the board irrespective of the progress of the conversion programme, resulting in the strange combination of pure glycol cooling and a 120ºC limit in some sources. BTW, the Spitfire I notes in the CE state that the limit is 120ºC and the coolant is 70% water and 30% glycol; but they state the engine as Merlin II or III not Merlin V. |
#5
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Hi see here for manual download:
http://www.wargamespezia.org/downloa...ary-handbooks/ |
#6
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Quote:
Quote:
Operational Notes for Pilots on Merlin II and III. 2nd Edition January 1939 Quote:
2nd Edition October 1939, Reprinted 1939 Quote:
4th Edition, April 1940 Quote:
Quote:
Because it might be interesting, the Amendments to Air Publication 1590B Volume I states: Quote:
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#7
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Yes, and why in the simulation gauges boost max indicate +8Lb./Sq.in and the real Merlin XXII arrive to 12 Lb/Sq.in look here
http://www.spitfireperformance.com/spit1pn2-a.jpg |
#8
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Bye now I have understand, it is a wronf oh the game, and also the gauges in the cockpit is wrong, see pictures on internet...
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