Why so few single engine Hercules applications?

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Admiral Beez said:
Reliability is one thing, but what about oil burn or leaks?
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I`m posting information, not quite sure why you seem to be assuming I`m here to argue the case for adopting sleeves, as anyone who has read my book
will tell you, I dont think was wise.

Sleeve valves generally obtained a best of about 30% worse oil consumption than poppets.

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With regards to major leaks (i.e a failure of any part of the oil system, including seals), see below:

1614468399771.png
 
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pbehn said:
Oil burn? I think that is what you get with high performance piston engines in the 1930s.
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Indeed. They all burn oil. But do sleeve valves burn more? The Short Sunderland has PBY-like range and notably uses Bristol poppet-valve motors. I wonder if this was a choice driven by a concern that the Sunderland would run out of oil before it ran out of fuel.
 
To my uneducated eye a definite yes. When you see a sleeve valve engine working as in a cut away being rotated, it is basically an invention to introduce burned oil into the atmosphere. The combustion chamber and exhaust are made up of lubricated surfaces. This is also true of the stem on an exhaust valve but that is a much smaller and more precisely machined surface. Oil will always creep past piston rings but in a sleeve valve engine the cylinder wall is a liner that is moving in all directions and is never "bedded down". The engine I saw (at the Yorkshire museum) had massive scores in all directions, I am surprised it was only 30% more than a poppet valve TBH. I am not surprised that it had to be kept warm in winter (Sabre engines) the contact surface is huge.
 
They do remind me of two strokes with their total loss lubrication, though that's still a popular engine format.
 
Admiral Beez said:
They do remind me of two strokes with their total loss lubrication, though that's still a popular engine format.
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Very few two strokes now, they cant pass emission regs. When I was racing a friend of mine had a Yamaha RD 250 tuned by a specialist, took out the liner and introduced a new one with ports all over the place, it was slightly more powerful than what the guy already had (a race tuned road bike) But it didn't last more than a meeting which is about 20- 30 miles. The bigger you make the ports the more the piston and especially the rings want to go inside them.
 
The Junkers Jumo 205 two-stroke diesels were something. Is there something about diesels that make them more suitable for two strokes ? No plugs to foul for starters.
 
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pbehn said:
His silliness just used to make me laugh, I gave up reading his "output" when he started arguing the huge positives of half ton motorcycles.
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fastmongrel said:
Was that the Quasar bike. It had a wheezy Reliant engine, a tubular frame that looked like it was welded by a blind man on a trampoline, acres of wobbly crack prone glass fibre and a windscreen wiper that flew off at regular intervals.
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How about a motorcycle using a Cummins diesel out of a Peterbilt 18-wheeler?
OK, they quickly decided to make it a trike instead.
Trike Chopper From a Peterbilt Truck and Cummins Diesel Engine MUST SEE!
Monster Garage, Peterbilt 1972
Jesse James Peterbilt Discovery Channel Monster Garage Semi-Truck Chopper Trike



 
Admiral Beez said:
The Junkers Jumo 205 two-stroke diesels were something. Is there something about diesels that make them more suitable for two strokes ? No plugs to foul for starters.
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My father occasionally drove deltic locomotives, with those it was power to weight ratio and using diesel due to the fire risk with petrol on boats. 18 cylinders and 36 pistons, it wasn't simple. Napier Deltic - Wikipedia
 


The German Version of the Sleeve Valve was Felix Wankel's Rotary Engine. In many ways more attractive due to the almost complete absence of valves. Continentals Stratified Charge version should have run on jet fuel and of course Mazda fixed many of the issues with the seals, finally realising that two sliding seals were needed per apex.. They started as a compressor in Germany.
 
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The J-35 engine used on the YB-49 had a "total loss" oil system. At the final rear bearing for the engine the oil was allowed to just flow into the exhaust. Sounds absurd, but when you think about it, getting the oil to go through the last bearing and then get it back up to the oil tank was not all that easy. And of course in those days an engine that used oil was not all that unusual.

The oil being lost overboard was a major factor in the YB-49 having to make an emergency landing on the way back for its trip to DC. That, and the failure of a crewman to do his job and make sure the oil tanks were filled before flight. That crewman reported for sick call before the flight but the aircraft commander had him hauled back to to the airplane. That same crewman also reported for sick call on the morning the YB-49 was lost at Muroc.
 
So, did the Hercules offer any advantages over poppet valve engines in: materials, production, maintenance, spares, weight, size, power (across altitudes), TBOH, fuel efficiency, oil consumption/tightness (big sump?), available accessories (superchargers, etc.), etc?

If not, in a world where everyone else from P&W, Wright, Shvetsov, Fiat, Nakajima, Gnome-Rhône and BMW spent their 1930s developing poppet valve radial engines, what was Bristol thinking? Here are some Bristol advertisements for their earlier Perseus and Taurus sleeve valves, claiming high power and compact dimensions.





If you go to the 2nd page of the link you'll see Hercules ads, but they're very light on any competitive advantages.




Finally, here's Bristol making some competitive advantages (valve timing and lubrication?) in their ads.



This ad claims the Hercules cylinder barrel is easy to produce and handle, conducts heat and exhausts well. Presumably this is a claim intended to differentiate from poppet valve engines.

 
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Admiral Beez said:
The Junkers Jumo 205 two-stroke diesels were something. Is there something about diesels that make them more suitable for two strokes ? No plugs to foul for starters.
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Small gasoline 2 strokes use crankcase compression to force air through the cylinders. All 2 stroke diesels that I am aware of use superchargers to achieve the same effect. Note that pure turbochargers don't work as you can't start the engine. Detroit Diesels use a turbocharger in series with a mechanical supercharger. The big EMD engines use a combination unit that operates mechanically at low loads with a overriding clutch that lets the turbo take over when it has enough energy. All GM 2 strokes (DD and EMD and Cleveland Diesel) only have exhaust valves. The intake ports are uncovered by the pistons ( no sleeves). The opposed piston engines (Junkers, Fairbanks Morse, Deltic) take this a step further by eliminating valves all together. One piston controls the inlet while the opposite one controls the exhaust.
Diesels also have an advantage in that the scavenging air necessary for 2 strokes doesn't waste fuel as it does for a carburetor engine.
This is a long winded way of saying that Diesels dont have have total loss oil systems.
 
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An ad on this page actually mentions the sleeve itself
Classic British Aviation Industry Advertisements 1909 - 1990
 
In college I had a '67 Datsun PL411 4-door sedan. Looked the same coming and going. Paid $600 for it. Sort of brick red. Paint would rub off on your hands. A "POS", as we used to say. Known as the "Ricksha" I installed a really sweet aftermarket 8-track player. Manual choke. Very reliable. Got @ 30 mpg, didn't use any oil. Took it to Jackson Hole with a couple buddies for some New Year's skiing 1975. Got down to 25 below one night. The next morning, most of the big SUV's (didn't call them that then) Blazers, Broncos, Jeeps, etc wouldn't start. So the Ricksha jump started a few. My roommate totaled it for me the following spring. It didn't take much. The body metal had all the strength of an empty beer can. My first car.
 
Bristol Taurus XII, 1130HP, 1550 cu in, 1300 lb
Bristol Hercules I: 1290 HP, 2364 Cu In, 1680 lb
PWA R-1830, 825 - 1200 HP, 1830 Cu In, 1467 lb
PWA R-2800, 2000 - 2500 HP, 2800 Cu In, 2350 lb
CW R-2600, 1500 - 1800 HP, 2603 Cu In, 1950 lb

So the Bristol engines may have been lighter than their equivalents, but it seems that they were sized rather smaller, which may explain their lower popularity.
 
Bristol Sleeve Crank drive:

 
You have to remember that most (if not all) of the ads were comparing the Bristol sleeve valve engines to Bristol poppet valve radials.
Unfortunately, while Bristol poppet valve radials were slogging ever so slowly through the sands of time, other companies were actually making progress.

Some of the most obvious is that Bristol still hung the valve gear out in the breeze on the poppet valve engines even during WW II.
Most other makers of large radials had gone to inclosed valve gear in the early to mid 30s.
Bristol poppet valve engines soldiered on with valve gear lubricated by grease gun fittings in WW II, up to five fitting per head (?) or 45 fittings on a 9 cylinder engine.
P & W and Wright had converted to valve gear lubricated by the engine oil (with return galleries) by the start of WW II. (or 1937-38). Enclosed valve gear does not always mean gear lubricated by engine oil. In some cases there were felt or fabric pads in the rocker boxes to retain the oil.

Since P&W, Wright, G-R and most other makers of radials were only using 2 valves per cylinder instead of 4 they were already using a much smaller number of parts than Bristol Poppet valve engines.
 
Very interesting, thanks. Your description reminds me of the OHV motorcycle engines of the 1920s with open valve springs, sometimes clothespin type.

What of the Armstrong radials? I know they had their own failures.



 
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