Rotary Engine life vs Radial Engine

[camelpilot]

Does anyone here know what the service life was of an average Rotary engine is? Say for a LeRhone or Clerget. I've googled but finding nothing.

Also, what is a rough service life of an equivalent sized radial engine before need for overhaul?

Any help would be appreciated.

Thanks.

[RAF56_Ball]

It woulddepend of a number of factors, including but not limited to:

1. the age of the rotary and condition of parts to start with, as well as the amount of previous use of the parts (there is a group making them new - at a price).
2. particular model of radial
3. how often it is used
4. Storage condition prior to you receiving it,
5. How you store it (most do not use them during winter months, or not as much)
6. frequency of use (in thsi case, more can be better)
7. oh, lots of fiddley-bits,
but generally I would expect a new buit rotary to last not as long as an equivalently sized radial built to similar relative tolerances and quality/materials as there are more forces and more difficulty in lubrication with radials. Taht doesn't mean don't use a rotary, just expect a heckuva lot more maintenance, and if it does well, you'll be happier.

just to throw a hand-greanade in the trenches, I'll bet WW-I pilots would have taken a reliable radial over their contemporary rotaries, because nostalgic undependability at best leads to death or capture. Reliability and efficiency brings you home. That from pireps and personal experience.

I would stil nostalgically love to have the chance to fly a rotary. Having said that, gonna put a Rotec in my Pup/Bristol Scout (conversion) of a Baslee kit. I know, it's not the real thing, but hey, I can build 8-10 of these for one original. And I bet it flies as well, and will fly more often (Okay so I'd almost kill for an SE-5, and I plan to build that one according to plans minus the 'Hisso'. But I don't plan on it being airborn anytime soon, either ).

[Romani]

Hello, I don't have it at hand right now, but the book "Gunning for the Red Baron" address the problem of carbon buildup from burnt castor oil and the degradation of performance and blames this as the cause of Lanoe Hawker demise in his duel with MvR.

The most extreme case is the Siemens Halke engine fitted to SSW DIII fighters used by JG II in May 1917. Due to the synthetic lubricant used the engines failed after only 7 to 10 hours of use.

To put things in perspective, the endurance of a SSW DIII was 2 hours, so it meant the engine failed after just 3 or 5 sorties.

I saved a thread from 17 October 2002 wich answered your question, but I can't find it in the archive, so I will copy paste the relevant info here:

2.) What was the time between overhauls for rotary engines? Did it vary greatly between types?
Were some better than others? It seems i read on average overhauls had to be done between the 10 and 15 hour mark, but I suppose it varied widely between types.


Answer by baldeagle:

As for the overhaul times, I wonder what they meant by "overhaul" in WW1. They may have just disassembled, cleaned, and reassembled the engines every 15 hours. I seem to remember Cole Palen saying that he had a rotary that had 150 hours on it without being taken apart. Perhaps also the modern castor oil is better quality than the 1918 stuff, that would play a part.

Hope this helps.

[Maxim08]

Well, I visited a friend a few weeks ago with 13 rotaries in his shop and we discussed maintenance. I was asking specifically about the 110 leRhone. Short answer, apart and checking everything at 50 hours. Expect a bill of 5 to 8K usd.
Our museum's radials are overhauled when first installed and, with only about 30+hours/year, last longer than the pilots ie hundreds of hours and even then it is preventative maintenance based on years in service opposed to necessity based on wear.
In short (using our 30 hr standard), expect a rotary overhaul once a year and a radial once a decade.
Regards,
John

[YavorD]

Le Rhône type C (80 hp) was reported as very reliable engine with good service record. There was a requirement for disassembly and elaborate cleaning at short intervals. Time between major overhauls was, probably, about 50 hours.
Similar service life was reported for Le Rhône type J (110 hp) and Gnome Monosoupape (100 hp).
The only radial used in significant numbers was water-cooled Salmson (Canton-Unné). Salmson 9Za engine of Salmson 2A2 was reported as quite reliable. No TBO figures known to me.
Regards,
Yavor

[Bletchley]

Hello Camelpilot,

I asked a similar question a few months ago, and there is a thread on it here somewhere with the title "reliability" or some such, with information that may be useful to you. Early war rotary engines had a TBO for a complete overhaul of around 10-20 hours, the mid-war types (Le Rhone, Oberursel, Clerget) of around 30-50 hours (but less, if synthetic castor oil was used), and the late war types (Bentley BR1, BR2) 40-50 hours (W.O. Bentley claimed 50 hours plus). This is compared to stationary engines that had a TBO for a complete overhaul of between 60 hours (Hispano-Suiza) to 100 hours plus (Rolls Royce Eagle), but a general average of about 80 hours. The later radials, in the immediate post-war period, about 100-150 hours (the 1922 manual for the Bristol Jupiter quotes 150 hours TBO for a complete overhaul), but then a considerably longer TBO from the mid-1920s onwards (up to 226 hours for the Jupiter VI in the mid 1920s, and 555 hours by 1931). There were, of course, several partial overhaul stages between each complete overhaul, and WWI rotaries were noted for their ease of access and maintenance in the field as compared to stationary engines (the Rolls Royce, an extreme case, had to be returned to the manufacturer for a complete overhaul at the end of its TBO interval).

Although there appears to be some relationship between reliability and TBO interval for a complete overhaul, a short TBO interval is not necessarily an accurate guide to unreliability. From the evidence that I have seen a properly maintained rotary can be as reliable as a well maintained radial or stationary engine of the same period - just with a shorter TBO interval to keep it that way.

Bletchley

[camelpilot]

Appreciate all the replies. Thank you all. You guys really are a great bunch.

Tally Ho.

[m9a3r5i7o2n]

CAMELPILOT:
I notice that no one has mentioned the Hispano-Suiza 200-220 engine which made by various manufacturers did not have a very good serviceable life span and the infamous lack of the Oil Pressure Control Valve made it even worse. In that case I would say almost any engine in the cold of winter was better, especially the Rotary Radials. The failure of Birkigt to install one was a crime to the French, British and the Americans but nothing was done!

Yours, M.L. Anderson

[Leatherhead]

Fred Murrin told me once the overhaul period for a Le Rhone is about 200 hours. Since he is the number one guy concerning these engines, I take his word for it. That being said, you're only going to fly your WWI aircraft for 15 minutes at a time, so it will take 800 flights to reach the overhaul period. That many, many years.........

This is all general, of course, but I trust Fred on this one. Compare this to a modern radial with overhaul periods of 1000 hrs.

This is all in modern times. If you want to know the overhaul times for back in 1914-1918, then I believe what others have posted above.

[Raoul Lubliner]

Hey that's all great stuff. So where do I buy a slightly used US&S built Le Rhone 9C?