BMW 802 developed in 1936 instead?

[Piper106]

I also have wondered why BMW didn't grow from the BMW 801 a 'carbon copy' 18 cylinder version.

People will say, even with their experience developing the R-1820, it took Wright a long time to get the R-3350 developed. I will NOT argue with that, but... with the R-3350 months or even years went by getting the fuel mixture from the carburetor evenly distributed among the cylinders. In fact it wasn't until Wright went to direct fuel injection that the mixture distribution problems were finally solved. Second, on the B-29, there was a LOT of development time spent trying to get the engine to cool, and not melt down. A scaled up BMW 801 surely would have been direct fuel injection and fan cooled right from the initial sketches. Not to say that would have made development 'a walk in the park', but direct fuel injection and fan cooling likely would have bypassed the two items that consumed so much of Wright's time developing the R-3350.

The multi-stage intercooled supercharging arrangement integrated into the historic BMW 802 was in my mind 'a bridge too far'. There was far too much crammed into that one project to take on. An 18 cylinder radial with basic single stage supercharging should have been one project. I would have made the two stage intercooled supercharger for the basic 18 cylinder engine a totally separate project.

As far as uses for a basic single stage supercharged 18 cylinder 2200+ HP radial; The later Ju 88 versions that bombed and strafed in support of the front line troops cried out for more power, not to mention the night fighter Ju 88s going after the RAF at 15000 to 25000 feet. Maritime patrol aircraft such as the Ju 290 and Ju 390. As others have said transport aircraft. Likely more, just cannot think of them at this time.

That is all I think I know.

 

[Shortround6]

So this begs the question, Shortround; why did you post a picture of the Napier Cub in a thread about German engine development?

To show, kind of, that the Germans weren't that far behind the rest of the world in the mid 30s. The number of 1000hp engines aircraft engines in the world between the Cub in 1922 and Merlin in the 30s can be counted on the fingers of one hand with left over fingers. And none of them had any real success. The Airframe makers weren't ready to build aircraft requiring such engines so there was no market.

 

[Shortround6]

I also have wondered why BMW didn't grow from the BMW 801 a 'carbon copy' 18 cylinder version.

People will say, even with their experience developing the R-1820, it took Wright a long time to get the R-3350 developed. I will NOT argue with that, but... with the R-3350 months or even years went by getting the fuel mixture from the carburetor evenly distributed among the cylinders. In fact it wasn't until Wright went to direct fuel injection that the mixture distribution problems were finally solved. Second, on the B-29, there was a LOT of development time spent trying to get the engine to cool, and not melt down. A scaled up BMW 801 surely would have been direct fuel injection and fan cooled right from the initial sketches. Not to say that would have made development 'a walk in the park', but direct fuel injection and fan cooling likely would have bypassed the two items that consumed so much of Wright's time developing the R-3350.

To look at it another way, the Wright R-3350 was "just" a Wright R-2600 with two extra cylinders on each row. Same bore and stroke, I am not sure if any parts, like valves or Pistons were same or 'started' the same ( initial castings or forgings). There was about a two year pause in R-3350 development and when they went back to it they redid a bunch of things based on what they had learned developing the R-2600 in the mean time.

 

[DonL]

What is to me very curious, is this much criticism on the BMW 801.
It was a 41,8 Liter 14 cylinder two row engine that can be compared to the Bristol Hercules, Wright R-2600 and Pratt Whitney R-2800, all three had near the same displacement. The Wright R-2600 ( 42,7 Liter) and Pratt Whitney R-2800 (45,9 Liter) had the biggest displacement and the Pratt Whitney R-2800 was an 18 cylinder two row engine.
And to my opinion I think the BMW was a good engine if we also look at the other engines at this displacement class. Also I have written a lot of things in this forum about BMW and the problems of good production tools and always be number three at the RLM. The Pratt Whitney R-2800 was clearly better, but also bigger and had 18 cylinder, compared to the Wright and Herkules, to my opinion the BMW 801 was the better (morer performance) engine.
The latest BMW 801 development which flew in the air BMW 801S 2200PS with MW 50, I think the engine could hold against it's counterparts, also the BMW 801 F was in develpment with 2400PS.

So I can't understand this always brought up criticism on the BMW 801.

 

[Shortround6]

To my mind the ONLY real criticisms of the BMW 801 from the German aircraft program perspective is that it wasn't big enough AND that it lacked a high altitude Supercharger for much of it's life. If the US or Britain had tried to use the R-2600 and Hercules respectively for similar aircraft/missions that the Germans used the BMW 801 for they would get similar ( if not worse) criticism. The R-2800 was not only larger but had two different high altitude supercharger systems that eliminated one criticism. Wide spread use of 100/130 fuel also allowed R-2800s even in their simpler forms to give 2000hp for take-off which was 18% more than the 801, of course since almost 10% of that can be attributed to the extra displacement it means the difference in power per unit of displacement wasn't all that great.

Late war (or immediately post war) R-2800s with water injection also showed some rather high performance figures.

Basically, trying to power high performance multi seat aircraft (bombers/night fighters)with a pair 42 liter air-cooled engines with single stage superchargers was asking a bit too much.
Same with the FW 190 in 1944. The British were moving to 36.7liter Liquid cooled engines, the P-47 had the Turbo R-2800 with water injection. P-38 used two 27 liter liquid cooled engines and turbos and water injection.

 

[nuuumannn]

The Airframe makers weren't ready to build aircraft requiring such engines so there was no market.

Aaah, got ya.

 

[davebender]

Most of which belonged to Flak units and the proportion still held true in 1939 when Britain and France declared war.

 

[davebender]

Timing is the problem. BMW801 would be a fine engine if it had been in mass production @ 1,600 hp during 1940 (i.e. same time as contemporary R2600 engine).

Why did BMW wait so long to start development of their next generation radial engine?

 

[DonL]

Timing is the problem. BMW801 would be a fine engine if it had been in mass production @ 1,600 hp during 1940 (i.e. same time as contemporary R2600 engine).

Why did BMW wait so long to start development of their next generation radial engine?

http://www.ww2aircraft.net/forum/av...fw190-entered-combat-33974-3.html#post1019711

Also keep in mind, that BMW and Bramo were the absolut biggest provider of german military and civilian engines between 1932-1938!

All Do-17 and Ju 52 and FW 200 and numerous Arado and Heinkel were all flying with the BMW 132 and Bramo 323, so at that timeline at both company the main attention of development was to upgrade the production process and the performance of the BMW 132 and Bramo 323.

Junkers and DB were at that time very smal providers and could realy concentrate on the development of new engines.

The irony is, that without the Bristol Jupiter and the Pratt Whitney R-1690 Hornet no war would be possible at 1939 for the german LW.

 

[Shortround6]

Most of which belonged to Flak units and the proportion still held true in 1939 when Britain and France declared war.

Doesn't explain the 1,888 aircraft, or the aircrew needed needed for that number of aircraft let alone the ground crew needed for 1,188 aircraft.

Now do you want to tell us how many AA guns these "20,000 officers and men" were manning so we can compare to the 1,188 aircraft.

I do like the bit about Britain and France declaring war like the German invasion of Poland had nothing to do with the start of the war.

 

[nuuumannn]

Most of which belonged to Flak units and the proportion still held true in 1939 when Britain and France declared war.

This is true, but you are manipulating the figures a bit, Dave. By the time Britain and France declared war - Germany had decided not to declare war when it invaded Poland; not very courteous, if you ask me - manpower in the Luftwaffe had increased to 1 and a half million men, of which nearly two thirds were flak personnel.

 

[DonL]

Why didn't you ignore him with this absurd claims?

This issue was discussed several times in this forum!

 

[nuuumannn]

Why didn't you ignore him with this absurd claims?

Tried that; doesn't seem to work. Besides, on a public forum like this you need to make corrections to the inaccuracies and absurdities in case someone gullible or foolish enough actually believes it. Its the old adage, if something is written enough times it becomes fact.

 

[Piper106]

To my mind the ONLY real criticisms of the BMW 801 from the German aircraft program perspective is that it wasn't big enough AND that it lacked a high altitude Supercharger for much of it's life.

I agree the BMW 801 was fine engine, in fact likely the best in the (nominal) 42 liter class. It had the Bristol Hercules, the ASh-82, the Wright R-2600, and the Mitsubishi Kasei all beat on horsepower, without any reliability problems. But by late 1943 or early 1944, there needed to be a larger (about 55 liter) follow-on starting into production. A scale up of the 801 to 18 cylinders would have done the trick.

 

[tomo pauk]

I agree the BMW 801 was fine engine, in fact likely the best in the (nominal) 42 liter class. It had the Bristol Hercules, the ASh-82, the Wright R-2600, and the Mitsubishi Kasei all beat on horsepower, without any reliability problems. But by late 1943 or early 1944, there needed to be a larger (about 55 liter) follow-on starting into production. A scale up of the 801 to 18 cylinders would have done the trick.

BMW-801 was plagued with reliability problems, that were solved in late 1942.

 

[Denniss]

The 801 always had room for improvements but not much was tried on the basic 801 until it was too late.
1) Improving the supercharger for more boost and/or better alt performance
2) Using external air intakes instead of the internal ones to get more ram effect (probably for fighters only)
3) switching to a 4-valve design so more efficiency at higher rpm

 

[Shortround6]

The P&W and Wright engines didn't use 4 valves.

4 valve heads are going to be be bigger and heavier than 2 valve heads and how do you arrange them?

With the V-12s you could put short intake ports on the inside of the V and short exhaust ports on the outside. Radial engines usually have one valve ( and usually a widely splayed valves.) on each side of the head with an inlet on one side and exhaust on the other with both ports facing the rear. Putting in two valves presents more of porting problem. It also presents a cooling problem, more valve stems and valve springs reduce the area for cooling fins.

https://sobchak.wordpress.com/2009/01/05/cutaway-bmw-801-piston-radial-aircraft-engine/

Arranging pushrods and rockers is also a pain and the rockers cut into cooling fin area.

Without resorting to such things as the exhaust going out the front ( and do you want the exhaust pipes, valves, cylinder port areas pre-heating the cooling air before it gets to teh rest of the engine?) used by early radials and given up what do you do?
Bristol used 4 valve heads;

bristol jupiter | roy fedden | de havilland | 1936 | 0907 | Flight Archive

But the arrangement is a bit strange. I guess you could call it a pent roof chamber but instead of the intake and exhaust valves being paired on each "side" of the angled head, Bristol has one valve of each type on each side of the angle. The pictures also show the forward facing exhaust which might be a challenge with a two row radial. You could use one port for both valves but then are you getting the full benefit of the 4 valves?

I don't know if 4 valves are impossible but you might have more problems implementing them than on a V-12 and with some of the trade-offs you might not come out very far ahead.

I would also note that as materials and knowledge changed designs changed. Bristol went to 4 valves when power was low but valves were NOT salt cooled and big valves suffered from overheating and warping. Valve springs were none too good and even a few hundred hours operation without a broken valve spring was cause for celebration. The ability to make heads with closely spaced long fins changes with casting and forging techniques and the US resorted to machining the fins using ganged slitting saws.
The more complicated you make the heads the harder they are to make and the higher the scrap rate.

4 valve heads will make more power, but looking at the entire picture are they really the way to go?

 

[wuzak]

Perhaps having the rows in-line, like the Deerhound, would be the best way to get the 4V solution.

The trick then is the cooling - but that can be solved with forced cooling and baffling (the reason for success of the R-4360, and even the R-2800).

Armstrong Siddeley - Deerhound Mark II pictures