Merlin vs. DB601 (1 Viewer)

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In an inverted vee the prop shaft is shifted down relative to the crankshaft, which is at the top. In an upright vee the prop shaft is shifted up from the crankshaft, which is mounted at the bottom.

The annular radiator wouldn't know if it were an upright or an inverted V-12 behind it.

As regards to the Spitfire and Mustang, if they were to have an annular radiator the engine and thrust line would have to be moved down.

Moving the thrust line of a upright-vee engine enough to accommodate an annular radiator, in the way you're suggesting, means the entire airframe would have to be redesigned, all for very little gain in efficiency or performance. Plus, for the likes of the Spitfire, without an almost complete redesign of the airframe, the cg would move significantly. In practice, during wartime no manufacturer would risk such a radical redesign.
 
Moving the thrust line of a upright-vee engine enough to accommodate an annular radiator, in the way you're suggesting, means the entire airframe would have to be redesigned, all for very little gain in efficiency or performance. Plus, for the likes of the Spitfire, without an almost complete redesign of the airframe, the cg would move significantly. In practice, during wartime no manufacturer would risk such a radical redesign.

I never suggested it was wise or advantageous to do so.

Annular radiators worked best on aircraft, particularly fighters, which were designed to be used with radial engines. That was certainly the case for the Hawker Tempest - if you see the engine installation there is a lot of space around the engine.
 
Dreaming...it has been done.

flugwerk190.jpg


That is a V-1710 upright V-12 in an Fw 190D-9 replica with an annular radiator. The cowling is larger than the engine, but it is probably no larger than on the original.
 
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Who says the radiator has to be centered on the prop shaft?
 
Here's a good picture showing the radiator installation on a restored DB engine from the NASM's He 219.

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This type of annular radiator arrangement is the so called 'drum' installation as the radiators do not face the direction of flight, air is ducted to them. This is apparently more efficient.

I can't see why a system like this couldn't be fitted to a V-12 engine in any orientation. Maybe I'm missing something?

Cheers

Steve
 
The Jumo-213A in regular layout, and turned, by your's truly, upside down . Does not seem like the annular radiator would be an awkward thing on an upright V-12.

ann.JPG
 
Hey Wuzak,

That pic of the Allison in the Fw 190D will certainly tell you the nose case is not stock. The prop shaft is about 8 inches to a foot too low. As I recall, the prop reduction gear came from Ross Aero here in the States. Also as I recall, it doesn't fly much. And, if it WORKS, that is too bad. I'd love to see it in the air.

We heard about that one while I was at Joe's and also heard it was not done very well from an engineering standpoint, so I'd love to hear about any flight time that aircraft has on it. From what we heard, it is fixable, but the correct people aren't being asked to fix it.

That is heresay; I have no first hand information on it. I hope what we heard is wrong and i runs just fine, but have not seen or heard of airshow appearances or flights as yet. I could simply have not heard about it and hope that is the case.

Purests might skoff at an Allison in an Fw 190D replica, but the lines are supposed to be true to scale and I'd love to see it fly. Seeing a 100% full scale replica fly is second only to seeing a real Fw 190D fly.
 
Greg, I expect that to be used in an annular radiator situation you would need an extended nose case - certainly over the standard V-1710 and Merin nose cases. The Sabre with annular radiator certainly had a longer nose case.
 
For a Merlin with an annular radiator you may have to change a few accesories, to remove them from under the sump. ANd use a downdraft carby.

Something like the Merlin 130/131

RR-131.jpg
 
OK, I did a quick (OK, most of an afternoon and evening) spreadsheet of the parts in an F-series Allison.

Without taking into account all the little clamps and finishing items I get 6,828 parts.

Adding in clamps, hoses and small hose interconnects, levers to operate all the items, linkages between them, and washers, nuts, cotter pins and bolts for them will get use VERY close to 7,000 parts, maybe very slightly over. If so, not by much. Could be very slightly under.

Considering we came up very close to 7,000 at Joe's, this independent confirmation makes me a believer. If it doesn't you, get a manual and just DO it. Youll be a believer. Remember flat lock washers and cotter pins. They add up quickly.

Oh and, about working on something and not knowing how many parts, there is a BIG difference between working on , say, a lawn mower, and bulding them for a living. The people who do it for a living are very well aware of the number of parts. I bet any car manufacturer knows EXACTLY how many parts are in a particular engine since they make or buy them. Easy if you stock the parts and must account for them when it is assembled.

Somebody esle can do the Merlin.

Use a single stage engine, single or multi-speed ... doesn't matter much. In fact, even a 2-stage wouldn't change the part count much.
 
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A chart with power-to-altitude values for DB-601A and Merlin III.
Thin red graph is for power available with 87 oct fuel (and, of course, also with a fuel of better octane value), +6 lbs per sq in ('psi' from now on) of boost was available from take off until 4960 m. The thick red line shows power available with 100 oct fuel, +12 psi boost was available from SL until 2790 m. Between 2790 and 4960 m, the boost pressure was gradually decreased to +6 psi, and then further decreased with altitude - supercharger was been able to provide ever less of compressed air with ever greater altitude. Use of boost pressure above +6 psi was for 'short periods' (probably not more than 5 min?)
We can note how much the 100 oct fuel increased the power of the Merlin, it delivered 20-30% more power than DB-601A under 4 km (the dotted line was take off power, 1 min rating for the DB-601A), and still about 10% more above 5 km. Merlin XII offered slightly more power above, than Merlin III, slightly less under 3 km, but it was cleared to use +12 psi boost even for take off.

601A III.JPG
 
People will notice that, in the graph, I did not take into account the over-revving of the DB-601A (allowed in late 1940, to be used above full throttle height of 4.5 km) - that should yield more power than Merlin III was been able to do. Another thing to have in mind is that 'maximum climbing condition' for the Merlin III was listed as '2600 rpm, +6.25 psi' - perhaps people might drop a line or two about pilots adhering or not to this limit while in combat, as well as adding something more about over-revving the DBs (other than it's written on Kurfurst's site)?

The Merlin XII was actually allowed for +12.5 psi for take off (red dash at 1190 PS), not just for +12 psi. The 'maximum climbing condition' listed at '2850 RPm and +9 psi'.
In the following chart, red lines are for Merlin XI. Thicker lines are for boost pressures above +9 psi, the 'upward going' line is for +12 psi boost, ending at ~1300 PS. Thinner lines are for boosts under +9 psi, the 'upward going' line for +9 psi, max being ~ 1170 PS at 4.5 km.

The 'violet' coloured line is for Merlin 45, maximum boost represented as +9 psi (from SL to ~5.5 km). Again, I'd really love to know when increased boost levels were introduced for Merlin 45, at least the +12 psi boost should've been available by the time Spit V entered combat? The +12 psi was take off limit (here).
This document states boost of 54.5 in Hg (~ +12.5 psi?) as used until Jan 3rd of 1942, the 60.5 in Hg (+15.5 psi?) to be used from that date. With +16 lbs boost, the power was ~ 1530 PS at ~3.4 km.

601N XII 45.JPG
 

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