Jumo 213 vs. Napier Sabre

[Engineman]

You yourself said in a previous post that dropping down to 18 lbs boost vs 25 lbs should've cost up to 500 bhp (I'm willing to account that it's a typo). On various sources, from Wikipedia to info in the two Hornet books I've referenced don't note that much of a discrepancy. They also don't note when or why the changes happened. You have to remember that the Hornet/Sea Hornet were the only aircraft to use the 130 series engines.

The 2070 hp for the 130/131 and 2030 for the 134/135 have been quoted forever in most sources I've read, be it internet or print. But then again, those sources also quoted incorrect overall lengths for the Hornet (37" 9" tail up for F1, 38" 3" for subsequent versions is the accurate figure) until the book Hornet & Sea Hornet: de Havilland's Ultimate Piston Engine Fighter came out about a decade ago (plans were found during he book's writing that were actual DH plans for the Hornet that had the correct info), and that the Sea Hornet NF21 had a top speed of 430 mph, instead of the correct 461 mph. I think that it's safe to assume that the newer info based on what are supposed to be more accurate sources should be correct or at least more accurate.

But even the newer sources quote the differing supercharger boost and power differences between the engines.

Yes, 2090-1670=420hp, I should have been more accurate in that difference between T/O 18lb and low alt Combat 25lb.

Looking at the different tables in the sources, there are differences. This will be due to many reasons, even the Rolls-Royce data changes around. I can see that the RRHT data
differs considerably in the Merlin 100 book in the "Leading Particulars" tables, which look to possibly be from an RAF A.P. on p.194, 195 and 196, where there are International ratings and Combat ratings, only some of which match the Engines of the World table.
It would also seem that there were some censored details at the end of WW2, certainly in the free press.
The Rolls-Royce data presented in graphical form is possibly more useful. Careful reading of the RM14SM Rating graph on p.141 possibly shows the small differences that are sometimes quoted at T/O and low altitude. The T/O 3000, +18lb shows 1650hp rising to about 1670hp @ 1000'. The low gear Combat 3000, +25lb shows 2050hp rising to 2090hp at about 2000',
so there are those differences.
Another detail is that the high boost fuels were changing, the RRHT book often refers to 100/130 fuel and 100/150. There is also mention of 115/150. There are others.

Eng

 

[BarnOwlLover]

I even looked up the R-R Griffon on the World War II Aircraft Performance site, and some details of some engines (namely power ratings) weren't fully quoted or censored. For example the Griffon 65, while the Griffon 69 (which I believe is for the most part identical to the 65) had full figures quoted. IMO, sort of weird what was censored/not quoted vs what was. Even the Griffon 130 had full power specs quoted, though you'd think that would've been restricted info, aside from the fact that the Griffon 130 may've been intended to be a civil engine (though it's most well known application was the Spiteful 16).

 

[Steve Hnz]

There was a Rolls Royce version of the Sabre type engine Rolls-Royce Eagle (1944) - Wikipedia

Sorry for taking this back, but was expecting some one to comment on this & didn't see it as I read through the next 3 pages. The Eagle had little in common with the Sabre other than the broad principle of being a sleeve valve H-24 unit, it was quite a lot bigger in swept volumes (46 litres as opposed to 36.6 for the Sabre) & had a RR developed sleeve actuation system of less complexity, apparently, than the Napier unit, so to describe it as a version of the Sabre type engine, is hardly accurate imho.

 

[pbehn]

Sorry for taking this back, but was expecting some one to comment on this & didn't see it as I read through the next 3 pages. The Eagle had little in common with the Sabre other than the broad principle of being a sleeve valve H-24 unit, it was quite a lot bigger in swept volumes (46 litres as opposed to 36.6 for the Sabre) & had a RR developed sleeve actuation system of less complexity, apparently, than the Napier unit, so to describe it as a version of the Sabre is hardly accurate.

Sorry, I didnt mean it was a version of the Sabre, but that it was as you say a H format sleeve valve, posted in answer to the original post which said of the Jumo 213 and Napier Sabre "Being the peak engine developments of their specific countries which one was more modern, had more potential, was more efficient, more powerful, overall better?" Since the Eagle was developed later and RR will have known of problems with the Sabre to my mind it is logical that the Eagle would be more "advanced".

 

[Snowygrouch]

Sorry, I didnt mean it was a version of the Sabre, but that it was as you say a H format sleeve valve, posted in answer to the original post which said of the Jumo 213 and Napier Sabre "Being the peak engine developments of their specific countries which one was more modern, had more potential, was more efficient, more powerful, overall better?" Since the Eagle was developed later and RR will have known of problems with the Sabre to my mind it is logical that the Eagle would be more "advanced".

Rolls-Royce Heritage Trust told me that the Eagle suffered from all the same major problems that the Sabre did, namely, at very high boost the oscillating liners distort and create all manner of horrors. Nobody solved the problem, you can make the liner very thick so it wont warp, but then it weighs too much and has too low thermal conductivity and the piston temps rise and rings gum up and ... and.... and

 

[Shortround6]

Sleeve valve.....................A good solution.....................................
If you are stuck with 87 octane fuel
If your valve springs keep breaking
If you never discovered sodium cooling for exhaust valves
If you never discovered stellite ( cobalt-chromium alloys) for valve seats and valve facings.

 

[pbehn]

Rolls-Royce Heritage Trust told me that the Eagle suffered from all the same major problems that the Sabre did, namely, at very high boost the oscillating liners distort and create all manner of horrors. Nobody solved the problem, you can make the liner very thick so it wont warp, but then it weighs too much and has too low thermal conductivity and the piston temps rise and rings gum up and ... and.... and

I sort of gathered that just from the Wiki pages on the Eagle and Wyvern. Long before I read of the specific problems with sleeve valve engines I saw a powered cutaway Hercules in a museum. It just looks WRONG in a way that cutaway poppet valve engines. You could see the exhaust port being uncovered, and briefly both sides of a small part of the liner have the exhaust gases on both sides while the exhaust gases are also in contact with the cylinder outside of the liner. The whole thing looked like something designed to wear itself out.

 

[Simon Thomas]

And yet the maintenance manual of the Hercules 763/773 does not require any maintenance on the sleeves at all.
Poppet valves require considerable maintenance. I understand that the Merlin valves need to be checked every 25 hours.

It is worth remembering that the Hercules stayed in operation for decades. If the sleeves really were that bad, they would have been swapped out for Double Wasps way earlier. They weigh about the same and have about the same max continuous power.

 

[BarnOwlLover]

It does help to remember that the Sabre was high revving and R-R probably tried to use Merlin or Griffon levels of supercharger boost in the Eagle (I know of the engine and it's basic details, but little about it's development)--it seems from what was said above that sleeve valves don't like huge amounts of boost. And though higher rpms was the reasoning behind the Sabre using sleeve valves, that also may've been part of the problem itself. The Hercules and Centaurus were both fairly large, low revving, low boosted engines, and hence the sleeve valves were probably more reliable in those applications.

It should also be noted that it seems that no production Sabres, Hercules or Centaurus engines ran two-stage superchargers, either.

As mentioned above, sleeve valves could've been a viable solution to the engine power problem if stuff like 100+ octane fuel, better poppet valve designs (better metals, sodium cooled valves, hard Stellite chrome--the same stuff used in firearms barrels, especially machine guns--being used in valve seats, improvement in OHC designs for inline engines and even improvements in pushrod designs for OHV radial engines) didn't make the reasoning behind them obsolescent or obsolete.

I know that they seemed like a good idea at the time (a lot of things in terms of aviation and automotive technology was trial and error), but in hindsight, sleeve valves were sort of a solution looking for a problem, and, sometimes, caused just as many problems as they solved.