Rotary Engines

Has anyone have any WW1 rotary engined spark plugs. I have recently been to the Shuttleworth collection, but their rotaries it seems have not the correct plugs in them as they are so scarce.
Any photos woulld be welcome, as I have been offered, 2 supposidly WW1 rotary spark plugs, but the seller is not 100% certain.
I cannot find anything relating to these engines either.(Not enough depth in Google).
Jim.
Lincoln .7

I’m not sure if your still looking for one, and I’m not sure this one really is still available, but I found this for sale online:

http://www.hydroponicsonline.com/store/Unusual-RFC-Royal-Flying-Corps-Rotary-Engine-Spark-Plug_190560552258.html

Unusual RFC Royal Flying Corps Rotary Engine Spark Plug:
$78

Original very rare WW1 vintage aircraft engine spark plug in good condition. Constructed of steel, brass and ceramic, this has got to be one of the most attractive spark plugs ever made! There are no markings on the plug but an identical one I have says Joly, a French maker. An exceptionally rare plug which would without doubt have been made for use with early WW1 rotary engines. Measures 65mm in height and is in good overall condition.
International buyers Welcome!
Payment by Paypal preferred.
Shipping in UK by 1st class recorded at £4 and International by Signed For at £10

Regards

Mark Pilkington

Hi Jim
More a case of needing the money for other things that I could use. I would have liked a collection of plugs from early aeroengines, but needed to focus my limited funds on what I was working on at the time :).
Bob T.

There are some photos in the thread you started in August:

http://forum.keypublishing.com/showthread.php?t=111274

Posts 5, 13 and 18

Richard

I wonder if The Vintage Aviator are making new ones?

Bob. Thanks for the info, you wouldn’t happen to have any photos of any plugs would you, Were the LeRhone, Gnome, and Clerget engines likely to have used the same plugs in those days?.
Jim.

Lincoln .7

I wouldn’t know one if it bit me but Google might be more help if you spelt rotary correctly…

I think you will confuse the issue here.

The Wankel engine or technology is not another name for the Rotary engine of the WWI period.

The rotary of WWI is a piston engine where the cylinders revolve around a fixed shaft.

Dr Wankel’s engine does not have pistons and cylinders/liners but a compression system using a triangular lobed rotor in a chamber.

Mark

Another name for a rotary engine is a Wankel engine. Not quite the same thing, I understand, but…

This chap seems to know a bit about them.

OS even make one for use in model aircraft! The 31600

I agree gbwez1, I read it some years ago and it helped a lot with my understanding of said engines.

If you can’t get it in the shops, most second hand aviation booksellers will put you on their wants list for a copy.

There was a really good little book on the subject done by Andrew Nahum at the Science Museum a few years back if you want to know more.

Well what can I say? Thank you for 3 very excellent answers, I have wondered how they worked and now I know:)

Thanks again.

The following is a description of flying the LeRhone in the Shuttleworth Collection’s Sopwith Pup, taken from an article written for a comopetitor magazine……..

…….The LeRhone in the Pup is a nine-cylinder four-stroke motor aspirated by two valves in each cylinder head that are controlled by a single push/pull rod. The associated rocker has an exhaust valve at one end and an inlet at the other. The advantage of the single push rod system is lightness, which is essential for the rotary. The disadvantage is that it is impossible to overlap the exhaust and inlet valve timing, so performance is limited. Nevertheless, it does provide more than adequate power for the Pup.

All rotary engines are characterised by a hollow crankshaft which is attached to the airframe. Around it rotate the cylinders and crankcase, the propeller being attached to the latter. The result is a light weight power plant that does not require liquid cooling. But it can overheat on the ground with prolonged running and the gyroscopic precession of the rotating mass causes some not-insignificant problems for the pilot. The handling of the engine is also specific, any pilot errors in this area can quickly lead to power plant failure.

Fuel is transferred to the engine by air pressure generated by a cockpit hand pump and/or a Rotherham propeller pump. The latter is fitted in the main propeller slipstream on the port forward wing strut and the former is fixed on the right side of the cockpit. At the base of the cockpit hand pump is a small tap. Setting it perpendicular to the feed pipe isolates the pump, turning it parallel with the pipe allows the tank to be pressurised by the pilot, finding the correct position at about 45 degrees to the pipe vents the air system to atmosphere. The various positions of the tap can be used in flight to control tank over pressure, tank under pressure and to cure an air leak. After flight the tap is used to equalise tank pressure with ambient. There is also an air pressure gauge to monitor the fuel tank pressure – the maximum is 2.5 psi – and a Jones valve, which acts as an engineer adjustable pressure relief valve.

Oil flow to the engine is total loss; an on/off tap, which is inaccessible to the pilot, is fitted in the line under the tank. Oil flow is confirmed by an oil pulsator fitted to the starboard wall of the pilot’s cockpit. The oil meniscus moves slowly up and down in sympathy with engine rpm when the engine is running, thus confirming that oil flows. However, given the blue mist that can be readily seen emitting from the engine and the pleasant odour of castor oil in the cockpit, the pilot is in no doubt as to whether or not oil flows to his rotary! Nevertheless, the pulsator may have one use. Engine rpm can be checked by timing the rate of pulsation’s and comparing the result to a calibration chart. But, as with the oil flow, in practice, the pilot’s perception is as good an indication of engine rpm as any – in this case it is achieved by ear and airframe feel.

A fuel on/off tap is located in the fuel line forward on the lower left side of the cockpit. Fuel flow to the engine is pilot controlled by two coaxial levers fitted in a quadrant marked from 1 to 10 on the left cockpit wall. The larger, outboard lever, referred to as the blocktube or fuel/air lever, is directly connected to a blocktube carburettor, which, in turn is located on the pilot end of the extended hollow crankshaft. It controls airflow to the engine and to a certain extent fuel flow. The inboard, smaller lever, referred to as either the petrol lever, the fine adjustment lever or the tampier filter tap lever, directly controls fuel flow into the blocktube.

Contrary to popular opinion, rotary engines of the two lever type, such as fitted to the Pup, can be modulated over a range of rpm. In practice, this is about 700 to 1150 rpm on the ground, noted on the cockpit rpm gauge, which equates to about 50 to 100% available power respectively. The approximate lever positions for 700 rpm are 3.0 on the blocktube lever and 2.5 to 3.0 on the petrol lever. For 1150 rpm the approximate positions are 7.0 and 3.5 to 4.0 respectively. For a given blocktube position, if the petrol lever is set too far forward (too rich), or too far back (too lean) the engine will cut. A rich cut should clear in about 30 seconds, which is disastrous in low level flight; a lean cut can be cured in about 5 seconds. The trick for safe operation of a rotary is to know when the engine is running rich or weak and what to do about it if it is.

Finally, the engine suite is completed by a single ignition system with magneto on/off switch on the port cockpit wall and a ‘blip’ button on the control column, which cuts the ignition when depressed. Although the engine can be modulated by judicious use of the blip switch, it is not recommended as a primary engine control. The engine is ‘shock’ loaded every time the blip switch is pressed and continuous flight with the ignition switched off leads to oiled and fuel fouled plugs. Better to use the petrol lever to modulate the engine over it’s limited range, or if even less thrust is required, to shut the engine down completely by selecting the petrol lever to the fuel off position.

Now, lets apply the above briefing on operating a rotary engine to a sortie in the Pup.

Rotary engine time is a precious commodity and time between overhauls is measured in a few tens of hours. So, given the propensity to overheat on the ground and the wish not to waste the precious engine time, the Collection parks the rotary engined aircraft at the marshalling point of the runway in use prior to flight. Following strap in the pilot immediately carries out normal pre-take off vital actions as his hands will be full once the engine is running. The harness is secured, the flight controls checked and goggles are positioned and secured – the cockpit environment of the Pup is windy.

When settled and prepared, the pilot calls ready to start to the ground crew. The fuel is confirmed on, the ignition off and the engine levers are set closed. The groundcrew turn the engine oil on and confirm the same with the pilot. Each engine cylinder is then primed in turn by depressing the respective exhaust valve and injecting a measured amount of petrol by syringe. Meanwhile, the pilot pumps the fuel tank to a pressure of 2 to 2.5 psi and checks that the pressure is maintained. The groundcrew turn the engine over several revolutions to distribute and mix the fuel.

When the groundcrew call ready, the pilot sets the blocktube to about 3.0, rechecks fuel tank pressure, holds the control column fully back, calls ‘Contact’ and sets the ignition ON. The groundcrew confirm that there is one of their number holding the tail down and that chocks are in position.

The propeller is swung. If all has been set and primed properly, the engine bursts into life with it’s characteristic staccato crackle, the airframe twists in opposition to the torque and a cloud of blue smoke is carried quickly away in the slipstream. The pilot waits for the prime to burn off, then as the engine dies, he advances the petrol lever slowly towards the expected running position. This will vary according to ambient conditions, but will never be more than about 0.5 of a division from position 3.0. The engine is warmed at about 700 to 800 rpm for about 50 seconds as the lever positions for smooth running are essayed.

The engine will go from rich to lean and visa versa with a petrol lever movement of between one eighth to one quarter of an inch around position 3.0. A lean engine exhaust sounds light but rough, a rich exhaust note is harsh and heavy. With practice, the two states can be heard and felt through the airframe and if the pilot is diligent, they can be noted as a slight drop in rpm as the over rich or overlean state is reached. A rich cut is cured by closing the fuel lever and awaiting engine pick up – it should pickup within 30 seconds in the air, but it will stop and remain stopped on the ground. A lean cut is remedied by slightly advancing the petrol lever and the engine should pick up within a few seconds both on the ground and in the air.

At this point the pilot cannot fail to be impressed by the smoothness of the rotary when compared to radial engines. This is probably due to the big end, the largest mass in the engine, being stationary in the rotary engine, whereas it rotates in the radial.

After a 50 second warm-up, full power is tested. The blocktube lever is advanced to about position 7.0. As there is not enough fuel flow to maintain running, the engine lean cuts. The petrol lever is then advanced slowly until the engine ‘picks up’ and the lever position will be between 3.5 and 4.0. Again, the rich and lean positions are noted and this time the lever spread is about a quarter to a half an inch. The maximum rpm is noted, normally about 1050 rpm, but provided it is above 1000 rpm, the flight can go ahead. Time at high power is minimised, about 30 seconds is reasonable. Power is then reduced to minimum by first retarding the petrol lever to cause a lean cut, then resetting the blocktube to the slow running position, then resetting the petrol lever as appropriate.

Following a quick cockpit check and a confirmation that the fuel tank air pressure is sufficient to commit to flight, the chocks are waved away. The blip button is now used for the first time. As the low power setting of 700 rpm provides about 50% of maximum thrust and given that the machine has no brakes, when the chocks are removed, if engine power is not killed, the machine will jump forward and strike the ground crew. This is not an action which is conducive to good ground crew relations.

When the ground crew are clear the blip button is released and the blocktube advanced, followed by the same with the petrol lever, both being set to the positions for high power noted during the ground run. The aircraft accelerates briskly and the pilot must guide the machine between two limiting handling areas. If the tail is raised too quickly, even with full right rudder applied, gyroscopic precession will cause the machine to yaw about 30 degrees to the left. Following that, if right yaw is rapidly applied to control the situation, a ground propeller strike will certainly occur. Conversely, if the tail is kept on the ground too long, the aircraft will take to the air close to the stall with all the associated dangers. The tail must be lifted slowly and progressively as the aircraft accelerates.

Now, back to the engine. As airspeed increases, the propeller unloads and the engine rpm increases. Fuel arrives at the engine via the hollow crankshaft and is fed to the engine via tubes running along the sides of the cylinders. The increased centrifugal force produced by the accelerating engine will enrichen the mixture. Therefore, if the petrol lever is not retarded slightly on take off, the engine will suffer a rich cut and the pilot will be given immediate practice of an EFATO……………………….

That’s enough for one post; does that help you sayers02?

A.

To add the last bit to Christer’s excellent answer, you can probably guess that “power take-off” would be a fancy description for bolting the propellor to the crankcase.

Hi Steve!

I remembered having answered that question before on the “old forum” and I found that the old thread had been transfered and did a copy/paste:

I was borne in the swedish town where Enoch Thulin had his aeroplane factory in the early twentieth century. It so happens that, in our club house at the flying club, we have a LeRhône rotary engine and this is what I know about it.

First of all, engines are stupid. They don´t know if the crankshaft or the crankcase is supposed to turn. It really doesn´t matter and if you start any engine and let it loose on the floor the crankcase will rotate in the opposite direction of the crankshaft.
So if you fix the crankshaft to the airframe the crankcase will rotate.

The crankshaft was hollow to allow the air/fuel/lubricant mixture into the crankcase.
The principle was four stroke with two valves. The exhaust valve is in the top of the cylinder with an outside actuating rod. The inlet valve is an automatic valve in the top of the piston. At the top of the exhaust stroke the exhaust valve closes, when the piston travel down the cylinder an underpressure is created which opens the automatic inlet valve and the mixture is sucked into the cylinder.

This wasn´t very efficient so, soon the inlet valve was moved to the top of the cylinder as well and it too was controlled by an actuating rod. On these engines there were tubes running along the cylinders connecting the crank case with the inlet valve becuse the mixture was still ingested through the crankshaft.

Neither this arrangement was efficient and to allow further developement in terms of HP the rotary design was abandoned.

Hope this helps,
Christer