3 row radials: pros cons

GregP · Mar 25, 2012

Hi Wuxak,

I didn't say the R-4360 had two crankshafts ... I said it was basically two crankshafts joined by a properly-designed main bearing mount that largely helped eliminate any coupling harmonics. It was a solid joining and became a single crankshaft, but the center exhibited almost no vibration at all except the same end harmonics as the 2-row unit. Altogether a neat design piece that never made the predicted power ... There weren't any 5,000 HP R-4360's as envisioned. They never made more than about 3,500 HP even in the developed versions, except for ONE engine that was tested at 4,500 HP. It never flew so, while I don't count it as a power output point, it DOES indicate potential that was never developed.

Today, the R-4360 is a powerhouse only becasue we stopped big-piston development for aircraft in 1945 ... and propellers are getting VERY scarce!

wuzak · Mar 25, 2012

GregP said:
Hi Wuxak,

I didn't say the R-4360 had two crankshafts ... I said it was basically two crankshafts joined by a properly-designed main bearing mount that largely helped eliminate any coupling harmonics. It was a solid joining and became a single crankshaft, but the center exhibited almost no vibration at all except the same end harmonics as the 2-row unit. Altogether a neat design piece that never made the predicted power ... There weren't any 5,000 HP R-4360's as envisioned. They never made more than about 3,500 HP even in the developed versions, except for ONE engine that was tested at 4,500 HP. It never flew so, while I don't count it as a power output point, it DOES indicate potential that was never developed.

Today, the R-4360 is a powerhouse only becasue we stopped big-piston development for aircraft in 1945 ... and propellers are getting VERY scarce!

Bear in mind that the R-4360 has 7 cylinders per row against the R-2800's 9, meaning that the angular spacing between pistons is different. Add to that the factthatthe stagger angle between rows is differnt because of having different numbers of cylinders per row and more rows to offset. For a 2 row it is simple - the second row can be offset half the angle between cylinders. On a 4 row the angle has to be 1/3 (IIRC) of the angle between cylinders.

So the crank throws will need to be at different angles for the R4360 compared to the R-2800. This will affect the balance of the system, and also the torsional vibrations - which is what P&W took their time figuring out with the R-2800.

wuzak · Mar 26, 2012

GregP said:
You might recall the current world speed record is held by ... a radial. Rare Bear and the mighty R-3350 went 528.31 mph in FAI supervised tests in 1989 and currently holds the world piston air speed record. No other radial or inline has come very close as yet. The fastest piston speed over a long range (1,000 km) is held by a Boeing B-29 at 410.43 mph in 1946. Please note both a powered by radials and both weer powered by the Wright R-3350. In WWII, they were right there but Spitfires, Fw 190's, Me 109's, etc. haven't been in the hunt for the world speed record for a LONG time.

Maybe the inlines aren't quite what you think they are? Although I DO like them, both engine varities have their places and uses. In the real world, Strega could probably take the world piston speed record right now, but the money is an obstacle. It probably costs about $350,000 or more to get a world speed record, and there is no payback.

I think it says something that you consider Strega capable of taking the world speed record from Rare Bear as it has much less horsepower (about 25% less and half the engine capacity).

You sure the 1000km record is held by a R-3350 powered B-29 and not an R-4360 powered B-50? I didn't think a B-29 could go that fast. An XB-39 could, but with less power than the B-50 could.

wuzak · Mar 26, 2012

GregP said:
You might recall the current world speed record is held by ... a radial. Rare Bear and the mighty R-3350 went 528.31 mph in FAI supervised tests in 1989 and currently holds the world piston air speed record. No other radial or inline has come very close as yet. The fastest piston speed over a long range (1,000 km) is held by a Boeing B-29 at 410.43 mph in 1946. Please note both a powered by radials and both weer powered by the Wright R-3350. In WWII, they were right there but Spitfires, Fw 190's, Me 109's, etc. haven't been in the hunt for the world speed record for a LONG time.

Maybe the inlines aren't quite what you think they are? Although I DO like them, both engine varities have their places and uses. In the real world, Strega could probably take the world piston speed record right now, but the money is an obstacle. It probably costs about $350,000 or more to get a world speed record, and there is no payback.

I think it says something that you consider Strega capable of taking the world speed record from Rare Bear as it has much less horsepower (about 25% less and half the engine capacity).

You sure the 1000km record is held by a R-3350 powered B-29 and not an R-4360 powered B-50? I didn't think a B-29 could go that fast. An XB-39 could, but with less power than the B-50 could.

wuzak · Mar 26, 2012

Greg, any of the big radials that would be considered to power the Spitfire would be almost twice as wide as the Spitfire fuselage....

GregP · Mar 26, 2012

Wuxak,

I think Strega could take the record because it can make 540 mph at sea level on a standard day. That beats 528 mph by 2+%.

The Japanese changed the Ki-61 from liquid-cooled V-12 to air-cooled radial of larger diameter very inventively and made what was probably the best Japanese fighter of the war in the Ki-100. The Spitifre could do it similarly. I don't advocate it, but it could be done if someone had the desire and the means. I'd rather see a reproduction Napier Heston do it ...

Also, I never said the R-4360 crankshaft was composed of two cranks from an engine with nine cylinders; I dnd't even imply it. It was composed of cranks from 7-cylinder engines with similar characteristics. They were interfaced with a proper center bearing race with a strong vibration-resisting mount structure.

wuzak · Mar 26, 2012

GregP said:
I think Strega could take the record because it can make 540 mph at sea level on a standard day. That beats 528 mph by 2+%.

Yes, I realise this. The point I am making is that it can do it with 3600-3800hp against Rare Bear needing around 5000hp.

GregP said:
The Japanese changed the Ki-61 from liquid-cooled V-12 to air-cooled radial of larger diameter very inventively and made what was probably the best Japanese fighter of the war in the Ki-100. The Spitifre could do it similarly. I don't advocate it, but it could be done if someone had the desire and the means.

The Japanese didn't have a very good time with liquid cooled engines.

There is no guarantee that a radial engine Spitfire woudl be any better. Probably the opposite in fact.

GregP said:
I'd rather see a reproduction Napier Heston do it ...

Me too.

Know any multi-millionaires willing to help us build a Napier Sabre or two?

GregP said:
Also, I never said the R-4360 crankshaft was composed of two cranks from an engine with nine cylinders; I dnd't even imply it. It was composed of cranks from 7-cylinder engines with similar characteristics. They were interfaced with a proper center bearing race with a strong vibration-resisting mount structure.

I thought you had implied it by discussing the trials and tribulations of the development of the R-2800 crankshaft.

Two row radials with 7 cylinders per row had different offsets, requiring different crank pin spacings.

In any case, looks like a single piece crankshaft to me.

http://www.enginehistory.org/P&W/R-4360/Image86.jpg

Readie · Mar 26, 2012

GregP said:
John,

You might recall the current world speed record is held by ... a radial. Rare Bear and the mighty R-3350 went 528.31 mph in FAI supervised tests in 1989 and currently holds the world piston air speed record. No other radial or inline has come very close as yet. The fastest piston speed over a long range (1,000 km) is held by a Boeing B-29 at 410.43 mph in 1946. Please note both a powered by radials and both weer powered by the Wright R-3350. In WWII, they were right there but Spitfires, Fw 190's, Me 109's, etc. haven't been in the hunt for the world speed record for a LONG time.

Maybe the inlines aren't quite what you think they are? Although I DO like them, both engine varities have their places and uses. In the real world, Strega could probably take the world piston speed record right now, but the money is an obstacle. It probably costs about $350,000 or more to get a world speed record, and there is no payback.

After WWII, rather sensibly I might add, the various government ceased piston development. Private people in the U.S.A kept at it and set world speed records. It seems people in Europe are less interested in that arena, and I understand that sentiment and reasoning. The money will never come back to you. But the speed records have all been set by Mustangs, Bearcats in the last 20+ years. It doeasn;t look like a change either as I'm told Rare Bear may go for a new record (won from itself) sometime in the next couple of years. I suppose we'll see, won't we?

Greg,
Your WSR pursuit is great achievement and 'Rare Bear' is a fantastic plane.

Its no so much that we are not interested in WSR's is just a money issue..or the lack of it.

But,we are in the race for the LSR 1000mph barrier.Mind you its a bloody great jet engine on wheels !!

The Mk19 Spitfire could do 460mph in standard RAF form. With the amount of money available now that Rare Bear has had spent on its motor I wonder how fast a Spitfire could have gone stripped of its guns armour?

We can but speculate.

There is a practical limit for the maximum piston engine aircraft speed anyway and, as you rightly say, the world went over to jets anyway.

John

Siegfried · Mar 26, 2012

tomo pauk said:
Apart from some (one?) experimental engines, such a development was as good as non-existent. I wonder if there were some/any plausible advantages vs. two-row 'classics', ditto for disadvantages

This shouldn't be a problem. I suggest a 3 row inline water cooled radial, technically a 'star' engine similar to the Jumo 222 to take care of any cooling issues on the rear cylinders.
A 3 row radial won't have the shaft problems of a 4 row engine (like the R-4360 or Jumo 222)

An air cooled radial shouldn't be too much of a problem either. Air cooled is a bit of a misnomer as around 50% of the heat is extracted via the oil cooler so the oil can be used to equalise the cooling on the rear cylinders with carefully balanced baffles to direct air to the rear cylinders.

GregP · Mar 26, 2012

Hi Readie,

You are corect in a lot of ways, but the Bearcat guys DID spend the money and DID get the record. No Spitfire guys did that post-WWII. I think that we should not be armchair quarterbacks. The record holder is the fastest until someone takes it away by going faster. Right now, officially ... the fastest piston-powered aircraft is a Grumman F8F Bearcat. C'mon all you Spitfire fans or Fw 190 fans ... build it and go get the record! Until you do, Rare Bear is the Big Dog until dethroned.

I think the fastest propeller-driven aircraft is the Soviet Bear bomber at about 575 mph ... but it is driven by four 14,500 shaft HP turboshafts and thus is not a piston aircraft at all. The acceleration is phenomenal, though. Probably has more propeller area than any iother aircraft ever built. the contra-props are HUGE and are supersonic probably over 40% of their span.

wuzak · Mar 26, 2012

Hey Greg, what are the chances of someone modifying a Spitfire for racing/world record setting today and not being castrated?

GregP · Mar 27, 2012

Excellent. All you need is a crashed example to start with. It isn't flying, so it's not cutting up a functioning warbird.

However, I don't think anyone will do it. if they thought they could beat a Bearcat, they would have done so by now. Since they haven't, they can't.

Today the Bearcat and Mustang are the fastest planes on earth powered by piston engines and propellers, regardless of things like the Do.335, Spitfire, Ta-152, etc.

Wishing it were different won't change that. The only thing that will is DOING it, and we have with the Bearcat and Mustang.

Maybe someone could dust off a Lancaster and beat the B-29 over 1000 km. I doubt it, seriously.

wuzak · Mar 27, 2012

GregP said:
Excellent. All you need is a crashed example to start with. It isn't flying, so it's not cutting up a functioning warbird.

Yes, but in most instances the owner will try to have it restored as a warbird.

GregP said:
However, I don't think anyone will do it. if they thought they could beat a Bearcat, they would have done so by now. Since they haven't, they can't.

Just because it hasn't neen done doesn't mean it can't be done.

Most of the race planes have been modified over many years. Not many warbirds have been modified for flying recently.

Plus, it takes a lot of cash to build such things. How much has been invested in Rare Bear over the years? Plenty no doubt.

GregP said:
Wishing it were different won't change that. The only thing that will is DOING it, and we have with the Bearcat and Mustang.

Yep, all I need to do is find a crashed Spitfire, restore it to working condition and modify it specifically for racing. Then get my hands on a Griffon (or Merlin) and get it raced tuned. And hire a pilot crazy enough to fly it.

GregP said:
Maybe someone could dust off a Lancaster and beat the B-29 over 1000 km. I doubt it, seriously.

I doubt anybody would consider a Lancaster could ever be fast enough.

However, we do know that the Spitfire wing has a higher critical mach number than the Mustang wing. At Reno speeds they must be getting close to those limits, so would that mean the Spitfire wing would make less drag at those speeds?

cimmex · Mar 27, 2012

Did a Spitfire ever had a race at Reno?
cimmex

wuzak · Mar 27, 2012

cimmex said:
Did a Spitfire ever had a race at Reno?
cimmex

Seems there wer a couple that appeared at the races, but didn't actually race, but one did race in a different race just after WW2.

Spitfire at Reno Air Races - Key Publishing Ltd Aviation Forums

wuzak · Mar 27, 2012

View: https://www.youtube.com/watch?v=4A2ZVhqJJKI

wuzak · Mar 27, 2012

So, what's more impressive?

Rare Bear at 528mph in 1989....

Rare Bear | Flickr - Photo Sharing!

Or the Macchi MC72 at 440mph in 1934?

Macchi Castoldi Mc 72 by amphalon, on Flickr

Readie · Mar 27, 2012

GregP said:
Hi Readie,

You are corect in a lot of ways, but the Bearcat guys DID spend the money and DID get the record. No Spitfire guys did that post-WWII. I think that we should not be armchair quarterbacks. The record holder is the fastest until someone takes it away by going faster. Right now, officially ... the fastest piston-powered aircraft is a Grumman F8F Bearcat. C'mon all you Spitfire fans or Fw 190 fans ... build it and go get the record! Until you do, Rare Bear is the Big Dog until dethroned.

I think the fastest propeller-driven aircraft is the Soviet Bear bomber at about 575 mph ... but it is driven by four 14,500 shaft HP turboshafts and thus is not a piston aircraft at all. The acceleration is phenomenal, though. Probably has more propeller area than any iother aircraft ever built. the contra-props are HUGE and are supersonic probably over 40% of their span.

Hello Greg,
The record holder is the Bearcat. I doubt that anyone will ever modify a genuine WW2 Spitfire to the extend that it could challenge Rare Bears record. To be honest, why would anyone want to?
The Mustang is almost as good as a Spitfire and has the same Merlin so, that could be a contender?
The British plane with a similar amount of sheer grunt to the BC would be the Sea Fury. But these are like rocking horse **** and I feel its a shame to over modified a classic plane.
Would you agree?
John

Readie · Mar 27, 2012

wuzak said:
So, what's more impressive?

Rare Bear at 528mph in 1989....

Rare Bear | Flickr - Photo Sharing!

Or the Macchi MC72 at 440mph in 1934?

Macchi Castoldi Mc 72 by amphalon, on Flickr

They both are...but, for different reasons.
How about the SB Schneider cup racers too?
John

wuzak · Mar 27, 2012

Readie said:
They both are...but, for different reasons.
How about the SB Schneider cup racers too?
John

Yes, the S6 and S6B had even bigger floats than the Machhi. One side was bigger than the other too.

Some basic calcs....

If we took the Macchi MC72 and gave it the same power as Rare Bear (c. 5000hp) we'd end up with a top speed of approximately 516mph.

If we reduce drag by 25% (and looking at the floats that should be possible) and use the same power (3100hp) as historically we are getting up to around 484mph. If we can reduce drag by 50% (which is probably a tall order) and used teh same hp we end up with an estimated 554mph.

Just a 10% reduction in drag allied with a 5000hp engine would give a Rare Bear beating 535mph.

Can we get 5000hp out of an AS6? Probably not, since there aren't any to fiddle with. However, the AS6 is basically two AS5 V12s joined together, each of these only being slightly smaller than a Merlin or a V-1710. Join a couple of Greg's boss's V-1710s together and 5000hp should be well within its capabilities. Actually, they claim 2900hp, so you would be talking 5800hp.

The only issue would be cooling. The floats on the MC72 (and the S6/S6B) had large areas of surface cooling. Maybe have to go for a total loss system for world record attempts.

3 row radials: pros cons

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