Radial Engines

[Mr_Grubby]

I think I am right in saying that Radial Engines always had an odd number of cylinders.

If so, can somebody please explain why ?

Thanks,
Mr G.

[RatherBeFlying]

At the risk that fading brain cells have dropped some vital details, I recall that the firing order would be to the next cylinder after 180 degrees.

With an even number of cylinders, the engine might get confused as to which way to turn.

A firing order to adjacent cylinders would generate some interesting stresses on the mount:D

[PaperTiger]

The total number of cylinders in a radial could be even, by arranging them in separate rows. The Pratt & Whitney series (and probably others) indicated the number of cylinders by the designation - an R2800 had 28 (4 rows of 7 cyls), R3600 (4 x 9) and so on.

[Lu Zuckerman]

R XXXX does not indicate the number of cylinders. It designates the cubic displacement or close to it. The R-2800 has two rows of nine cylinders. The R-1830 has two rows of nine cylinders where the R-2600 has two rows of nine cylinders. The individual banks have an uneven number of cylinders as postulated in the first post.

All of this through the fog of time.

:cool:

[sycamore]

Paper Tiger
Sorry to disillusion you but US engines are designated by capacity and type
P& W R-985- is a Pratt&Whitney Radial of 985 cu.ins capacity. It is also a single - row 9 cylinder.
A Wright R3350 is an 18 cylinder Radial of 3350 cu.ins capacity.double -row(2 x 9).
A Packard V-1650 is a licence built Merlin.
A P&W R-4360 IS A 28 CYL, 4- row radial( 4x7).
The USA system for designating engines is based around capacity,whereas our system is more HP based,and capacity in litres.(conversion factor for cu.ins - ltrs = x16.38)
As a guess you can probably guesstimate the number of cylinders by dividing capacity by 110 for small engines and 140-155 for larger one s.
Lu Z will probably to put me straight if i`m talking bO*****S.

:) :)

[Synthetic]

I think it is to do with having two pistons changing direction at the same time. With an even number of cylinders, they do, which would produce a more severe vibration. With pistons as large as the ones they used, this would have been a significant factor. This is the principle behind five cylinder car engines (Volvo et. al.).

The direction of rotation is governed by the inlet and outlet valve and ignition timing, and the starter usually gives the engine a clue;)

[PaperTiger]

I should have figured it couldn't be that simple, sycamore.

[Tim Zukas]

Suppose you built a single-row eight-cylinder radial (a four-stroke-cycle radial, which I assume the well-known radials were). All the cylinders connect to the same crank-- right? So the #1 piston starts its downstroke, then the #2, then the #3... but as you go around the circle you'd like power strokes to alternate with intake strokes. So if #1 fires, then #2 does its intake, #3 fires, and so on around to #7 fires, #8 intakes... and then #1 is scheduled for an intake. So now what?

But with an odd number of cylinders that problem doesn't arise.

A typo in the previous post: the R-1830 has two rows of seven cylinders, of course.

[Lu Zuckerman]

I think it is to do with having two pistons changing direction at the same time. With an even number of cylinders, they do, which would produce a more severe vibration. With pistons as large as the ones they used, this would have been a significant factor. This is the principle behind five cylinder car engines (Volvo et. al.).

I’m straining my brain on this one. I attended mechanic school in 1949. What is quoted above is quite possibly the reason but the internal geometry of the engine may also come into play. On a radial engine the connecting rods are not quite the same as on a conventional internal combustion engine. On an auto engine the crank throw passes through a 360-degree path and the connecting rods pass through the same path. On a radial engine there is what is called a master rod and this is attached to the crankshaft which is similar to that of an auto engine. The center of the master rod passes through a 360-degree path. The other rods are called articulating rods and they are attached to the master rod at the periphery of the master rod and as such when the master rod passes through a circular path the articulating rods pass through an elliptical path. I believe this type of set-up can not accommodate an odd number of articulating rods. (The master and the articulating rods total up to an uneven number).

Because the articulating rods pass through an elliptical path the firing of the spark plugs must be altered so that when the engine passes through two revolutions all of the plugs fire at the same position of the piston. This is accomplished by the use of a compensated cam on the magnetos, which is profiled to cause the points on the mags to open at the correct time. The cam rings on the engine are profiled so that the valves open and close at the same time to compensate for the uneven movement of the pistons.

At least I think this is correct.

Check this out: http://www.howstuffworks.com/radial-engine2.htm


:D

[411A]

And then we have the most advanced radial of 'em all, the Curtis-Wright R3350- DA/EA series, eighteen fuel injected cylinders and three power recovery turbines pumping out (largest version) 3,400 HP. SFC 'round about 0.36 pounds fuel/HP/Hr.

However, in order for them to churn out all that HP, 115/145 fuel was required.

Worked good....provided you didn't run short of oil...1.5 gal/hr as I recall.:eek:

[pigboat]

Check out http://www.enginehistory.org/
It's the Aviation Engine Historical Society site. Great stuff. In the gallery section, one member has done some CAD images of the R3350TC, including the PRT's.
There's also an article on the development of the R2800, and the problems they encountered with crank shaft torsional flexing.

[Lu Zuckerman]

The R 3350 Turbo compound was the first A/C recip engine to develop more horsepower than its' cubic displacemnent. I remember long ago reading a US Navy publication that they had the first TC R-3350 to exceed 1000 hours installed on the wing. In that article it stated 3500 horsepower.

:cool:

[Chuck Ellsworth]

And of course they sound good. :D

Cat Driver

[GotTheTshirt]

I notice all the radials referred to are of US origin :p :p
Its like Mr P & W had a patent on them
Having worked many hours ( and nights ) on Mr Pratts fine products I'm afraid they could not hold a candle to the Bristol Beauties. :D :D

When we were getting between 800 and 1,000 hours on the wing from Pratt we were getting 2000 hours + on Centaurus.

We never changed a cylinder in anger on a Centaurus. Bit different from Pratts ! On the 1830 we got plenty of practice and you just hoped it wasn't a bottom cylinder on your shift.

Incidentally for the uninitiated the Bristols were sleeved valved
:p :p

[18-Wheeler]

(tongue firmly in cheek here)

The reason the English engines lasted longer is because they'd NEVER rust at all, not with the amount of oil that comes out of them! :)

The only radial I've had anything to do with is the Alvis Leonides, in the Twin Pioneer.

[GotTheTshirt]

18 wheeler,

Alvis are Ok but you cant beat a pair of Bristols;) ;)

[Jhieminga]

you cant beat a pair of Bristols

Hey, I've got that on a T-shirt!! :D

[Lu Zuckerman]

you cant beat a pair of Bristols

Are you referring to the engine or something else?

:D

[sycamore]

Lu
Seems like we on this side of the pond need to keep edificatin` you N.Americans.
Bristols-- large , round and firm,--- usually found on the front of girls. Depends upon age( of subject), but usually ,Jupiter,Mercury,Hercules, or Centaurus, in ascending order of capacity---- or size of hand for measuring..;) ;)

[Lu Zuckerman]

Bristols-- large , round and firm,--- usually found on the front of girls. Depends upon age( of subject), but usually ,Jupiter,Mercury,Hercules, or Centaurus, in ascending order of capacity---- or size of hand for measuring..

Thats what I was alluding to when I said engines or something else.

I believe it comes from Cockney rhyming slang.

:D

[DrSyn]

You are quite correct Lu.

The full cockney rhyming slang is Bristol City, plural . . .Cities. I am sure I don't need to elaborate.

To return to the topic, I was also very fond of the Bristol Hercules, as fitted to the Varsity on which I did my advance training.

[Lu Zuckerman]

I have maintained R-985s, R-1300s, R-1340s, R-1820s, R-1830s, R-2800s and R-2600s and I can’t for the life of me figure how the valve trains on British engines operate. Is there some source on the internet that explains it?

:confused: :confused: :confused: :confused: :confused: :confused:

[DrSyn]

Mr_Grubby's initial question has probably been answered by now, especially thanks to Lu's excellent link to the "howstuffworks" site - I shall enjoy browsing that!

However, I couldn't let pass GotTheTshirt's earlier comment about Beautiful Bristols and the predominance of PW, especially in view of Lu's latest post. I can't instantly recall how the valve drive worked (after 32 years!) but I am sure someone here can.

Meanwhile, here is a nice pic of the Bristol Hercules (http://www-g.eng.cam.ac.uk/125/achievements/ricardo/page39.htm) layout and a cylinder cutaway of its Sleeve Valve (http://www-g.eng.cam.ac.uk/125/achievements/ricardo/page41.htm). For Eng Hist buffs, this comes from a short bio of Sir Harry Ricardo FRS (http://www-g.eng.cam.ac.uk/125/achievements/ricardo/) who was the genious responsible for introducing this highly reliable valve design to British aero engines (courtesy of Cambridge University Eng Dept).

Through pigboat's link to the "enginehistory" site you can also find detailed colour pics of Brizzle aero engines at Midland Air Museum (http://www.enginehistory.org/coventry.htm), Coventry. Clicking on the cutaways will produce a hi-res detail of a sleeve-valve cylinder. Hope this is of interest.

Now, where did I store my course notes . . . . :(

[Wiley]

Speaking of Bristols, I remember the Bristol Freighter and those wonderful Bristol Hercules… Hard to imagine that the same engine had powered the Sea Fury.

On the subject of big round engines, is there anyone out there who could give a brief exposition on the workings of a rotary engine (not the 1970’s motor car version, but rotary engines as used in the Sopwith Camel and other WW1 fighters)?

I know that much of the engine (the cylinder block?) actually spun around, hence the name, but know little more than that about them. With all that spinning metal, the torque and gyroscopic precession must have been tremendous with large power changes and any rapid turns – I understand that it was faster to turn the Camel ‘the long way around’ in one direction (left or right? forget which), in what I imagine was a Derry Turn manoeuvre, making use of the precession to assist the turn, rather than in the ‘correct’ sense, where the pilot would be fighting against it. I understand that this was used to great effect in air to air tactics, where it not only got the aircraft to where the pilot wanted it faster, but foxed the opposition when the aircraft appeared to be turning in the opposite direction to the way it was actually turning.

I look forward to hearing all the accurate details from someone who knows.

[Bre901]

Wiley

there is an active thread on rotary engines in Tech Log

http://www.pprune.org/forums/showthread.php?s=&threadid=77079

[Lu Zuckerman]

OK, I looked at the pictures of the sleeve valve cutaway and the engine minus the inlet tubes and the exhaust pipes. Regarding the sleeve valve does it move up and down to align the correct port with the correct inlet/outlet (inlet tubes/exhaust pipes? Or, does it rotate to do the same thing?

On the engine picture you can see that some of the ports are blocked and others are open or, partially opened, which naturally suggests that it is a timed operation. The porting is similar to a two-stroke diesel engine but in this case the ports are fixed and the piston moves in relation to the ports. The porting on the Bristol engine is profiled which suggests that the inlet and exhaust are controlled to time the fuel air mixture inlet in relation to piston movement as is the exhaust port.

If there is relative movement between the sleeve valve and the cylinder is it lubricated?

:confused:

[Zipperhead]

Lu,

If you look again at the picture of the sleeve valve cylinder, down in the bottom left there are two gears visible. The upper one of these is the sleeve drive for the sectioned cylinder, and coming out of it on the right hand side is the crank which moves the sleeve on a balljoint. So, up and down and round and round.

Graham

[GotTheTshirt]

Wiley,
The Bristol Frightener and the Varsity, Valletta, Viking all had Hercs but the Sea Fury had Centaurus ( same as the Ambassador - 2,650 Hp!!)

Lu, I dont know if the web site shows it but the sleeve describes an ellipse. Its driven by a crank pin from a gear wheel. I suppose after a conventional P&W the system seems a bit more complicated but in the real world it was much less trouble. No valve to burn out , no tappits to adjust every 200 hours, no push rod oil leaks etc etc! When I first got involved I could not believe that the very small crank pin that drive the sleeve would not fail every 50 hours but in over 8 years of the beasts ( Herc and Centaurus) never saw a pin fail. Also on the Centaurus as I mentioned earlier never changed a cylinder and had 1 premature removal ( super charger drive shaft seal failed and pumped all the engine oil through the supercharger)
We did over 50,000 engine hours
:) :)

The Reno Sea Fury had the Centaurus and I think they managed to get well over 3,000 HP:D :D

[Shaggy Sheep Driver]

I loved flying behind the Vendeneyev M14P in the Yak 52. A superb piece of kit (9 cylinder supercahrged, geared, radial).

It only problem is the capability to get hydraulic locks in the lower cylindrs despite pulling through before start. You really need to drain the inlet pipes to be sure....

SSD

[Samuel]

The Alvis Leonides required turning manually through nine blades for best results on starting. Don't know how, or if, they did that on the Twin Pioneer with the same engine.

The Bristol Freighter was the last [only?] British aircraft with the same manufacturer of airframe and engine, Not a lot of people know that!

[sycamore]

Samuel,
All Twin-Pins carried a long pole fitted with a stiff rope loop on the end,to pull the props over b4 start to prevent "hydraulicing". Once saw a 209 crew start that way after they had run out of cartridges/ safety-discs/10c pieces in Borneo.
Another way was to get a long rope with a loop on one end, loop that over a blade,and wind the rope around the CSU dome.Then commandeer all the pax. to pull smartly on the rope as someone pulls the blade over with the "puller-over"!
Last-ditch as the Indians-sorry, Indons in this case were coming over the border!!;)

[Jhieminga]

From what I've gathered, both from personal experience and some discussions with others, there are two approaches to starting radials with respect to oil in the cylinders. On an R-2600 the engine needs to be pulled through 4 revolutions (I've done so myself many times!) to get rid of the oil in the cylinders. The reasoning behind this is that the flywheel in the starter will take no account of any hydraulic lock and will continue to try to turn the engine even with the hydraulic lock. On an engine with a directly driven starter (no flywheel/mesh system) you can pull the engine through several revolutions on the starter to clear the oil as in a hydraulic lock situation a shearpin in the starter system would break before the engine will (from what I've been told this is the situation on a DC-4 engine). I think that on a Yak-52 installation some similar system exists which disconnects the starter when it meets with too much resistance.

Anybody else with more info?

[Lu Zuckerman]

The description above alludes to getting rid of the oil in the cylinder in order to eliminate the possibility of a lock with this being done by pulling the prop through manually. This is not to say this could not be done. However when pulling the prop through and the prop won’t move beyond a certain point the only way to get rid of the oil is to pull the plugs and purge the oil out of the cylinder through the plug holes. It may be necessary to clean or replace the plugs.

In the method described above if an intake valve opens and the oil runs into the intake tube the next time that same valve opens the oil can run back into the cylinder. If there is sufficient oil present a hydraulic lock can occur when the engine is turned over by the starter. Depending on the energy imparted by the starter you can bend an articulating rod, damage a piston or blow the head off of the cylinder. In any case the engine is a candidate for heavy inspection and resultant tear down or complete overhaul and inspection.

:cool:

[GotTheTshirt]

Having been involved in operating a few dozen Daks over the years the hydraulicing bogey man was drilled into you from cradle.
I never saw an engine hydraulic (apart from a slight hesitation on rotation)and we never pulled an engine for hydraulic damage. I know that technically it can happen but I just never saw it. Lucky I guess.

We had both inertial and direct drive starters on our machines. The beauty of the inertial starters was that you has a hand start crank. This was an operation to behold. If we had a starter failure on depature we would dispatch the aircraft on pax flights with an erk and a starting handle to get it round the houses..
You put the handle in and wound the inertia wheel until it was rotating quite smartly then you could either mesh from the ground with a pull handle or if the mesh circuit was ok the crew could mesh from the cockpit. This relates much easier than reality believe me!!

We had oil dilution on the cold weather ones ( probably the same as the Canadian ones Lu).;)

On the Vikings there was a leather boot with a rope that went over one of the prop blades and the theory was that you could start the engine by pulling the blade round with a gang of blokes:D :D Fortunately I was never lucky enough to be one of the chosen few:rolleyes:

We had Cheetahs on our Anson's and of course they never had staters so all starts were done by winding a crank on the side of the engine.
This of course took took two guys but the old boys (old when I was a lad:p ) would start them on their own by giving them a good prime and pull them over by hand a few times then they set the engine with a piston right after TDC, get in the cockpit and press the booster coil button and voila off she go !!

Some of the later Ansons had starter motors and we had an Anson ready to go on an overseas job ( magnetometer dragging!) when the starter failed. They ordered a new starter AOG from the guy in Blackpool ( ANT - Whyatt ???) paid up front and sure enough a starter handle arrived at great expence !:D :D

[treadigraph]

Samuel, wouldn't the Britannia take the prize as last aircraft to have engines (Bristol Proteus) and airframe built by the same manufacturer? Not that I actually know when the last Britannia and last Freighter were resepctively built, but I'd assume the Britannia was later!

[Samuel]

Yes, you're correct! I had forgotten about the Britannia. It was built a long time after the last Freighter.

I believe an RNZAF Bristol Freighter Centaurus was once started by the lawn mower method of attaching a rope and pulling!

On the subject of the Leonides, as attached to the Pembroke, turning the props was the price one paid for going wherever the Station Flight aircraft was going at Eastleigh! Those flights were never dull ! That aircraft is still flying I believe.

[HectorusRex]

For Lu, the motion of the sleeves, as driven by the sleeve driving cranks, via the ball joint, is a combination of reciprocating and articulating, thus rotating the sleeve as it rises and falls.
Kidney shaped ports in the sleeves became aligned with the inlet and exhaust ports in the cylinders.
From memory there were 2 inlet, 2 exhaust, and 1 common port per sleeve, but only 4 cylinder ports.
The sleeves were lubricated but cleanliness was absolutely vital in the oil supply.:)

[Kolibear]

hydraulic locks

I'm a bit confused with hydraulic locks, I can understand how you can get a lock in the bottom cylinder and how you clear it by pulling the engine through, and the oil is dissipated as the valves open.

But what happens if the engine stops with the lowest cylinder on the compression stroke? All the valves will be closed so when you turn the engine over next time, surely you will pushing the piston into the accumulated oil, which has nowhere to go - hence the lock. :(

Do you then feel the resistance through the prop and whip a plug out to allow the oil to drain free?

An explanation of how it works in practical terms would be appreciated.

[Shaggy Sheep Driver]

I think that on a Yak-52 installation some similar system exists which disconnects the starter when it meets with too much resistance.

Not so. The Vendeneyef M14P in the Yak52 doesn't have an external starter motor. It starts by admitting compressed air into the cylinders via a pneumatic distributer to drive the engine round.

From the pilot's point of view, after priming you press the starter button with the mags off. There is a loud 'pop' as the air solenoid valve opens, followed by an asthmatic wheezing as the prop jerks slowly round. The button also activates the 'shower of sparks' magneto, so the engine eventually fires up on a couple of cylinders at least, wherupon amid clouds of smoke the mags are switched on and button is released. Vigourous pumping of the primer may be required before the engine becomes self-sustaining.

The particular problem with hydraulic locks is becuase the inlet pipes actually extend furher out from the engine than do the internal bores of the cylinders - they attach to the heads near the top of each head. So on the lower 3 cylinders the internal bore of the pipe is lower than the inside of the head, so oil can collect there. Because it is below the level of the heads, and therefore the exhaust valves, pulling through will not remove it. If the engine is started with oil in the pipes, the oil will be drawn into the cylindr and cause a destructive lock.

To overcome this, the inlet pipes of the 3 lower cylinders have drain plugs fitted at their lowest point. If the engine has not been run for a while, the cowlings should be removed and these plugs unscrewed to drain out any accumulated oil.

If a lock destroys a cylinder on start up, that is bad news. But far worse news is a 'partial lock' Here, there is a hydraukic lock which is just sufficient to bend the con rod. The engine will run OK for maybe many hours, but now contains a time bomb. At some point that con rod will fail, and may take the whole engine with it. That is *very* bad news, and is why, if you run an M14P, you must be very, very careful of hydraulic locks.

SSD

[Kolibear]

Thanks SSD, that makes sense.

[Jhieminga]

Thanks SSD! Regarding my original comment: I once stood fireguard on a starting Yak52 on which the prop when starting only went partially round and kicked back again (with suitable wheezing noises). The pilot then asked me to give the prop a shove in the right direction after which a normal start could be accomplished. After reading your post, am I right in assuming that this could be a case of a wrongly positioned prop? Does it feed air to all the cylinders at the same time (surely some will be on a compression stroke and won't benefit from it) or just several chosen ones? The aircraft had flown that morning just a couple of hours previous so there was no reason to pull the drain plugs I'm guessing.

[Shaggy Sheep Driver]

The compressed air is fed via the pneumatic distributer to whichever cylinders are on the power stroke - so the air drives the engine round as if it was under power, but very slowly.

Your experience of 'kick back' indicates the pilot was (incorrectly) starting with the mags on. The 'shower of sparks' mag operates after TDC so the engine will fire and rotate the correct way at the very low speeds of starting. The normal mags fire before TDC (standard ignition advance), so will cause the engine to 'kick back' if they fire the mixture at low cranking (start) speed. The engine should therefore only be started on the 'shower of sparks' mag.

If you emove a mag distributer cap on the M14P, you will see that the rotor arm has two 'fingers'. One is for normal operation, the other is the retarded one for distributing the 'shower of sparks'.


SSD

[polzin]

Wondering why so many Seafurys get converted to P&W's Is it availability?.

[Vfrpilotpb]

Polzin, yes purely supply, the big Bristols have nearly gone for ever,

Lu, I am lucky enough to own a very good Bristol Hercules(3 Hours, currently on loan to the Yorkshire Airmuseum), my father flew Beaufighters(in North Africa) which had the Herc fitted he told me that those engines used about 50 galls of oil per flight, but with the Carb feeding directly into the crankcase would this not be a two stroke engine, therby needing a lot of oil to mantain the lubricant on the facing between the cylinder wall and the actual sleeve valve and piston?
Peter R-B

[GotTheTshirt]

Polzin, VFR,

Yes its availabilty.
Also bcause of their commonality and lots of knowledge in the US the P&W is much more tweakable for the racing guys.

He is a wartime advert for the Bristol sleeve valve, showing the workings, and in my experience the blurb is very true. The differences they highlight about valves are very true.
We had to adjust valve clearances on the P&W (1830) every 500 hours. It needs several guys to do this and takes a while. Northing like this on a sleeve engine.
http://www.thunder-and-lightnings.co.uk/pprune/bristolsleeve.jpg

Re oil consumption of course the British radials did use more oil the the US ones ( In my experience) which prompted comments like " Fuel cooled oil burning engines"

However we never considered it a real problem and certainly our Herks and Centaurus went out and back on flights without a problem
In the DC4 and DC6 we had overload oil tanks built in to transfer oil to the engines in flight, so oil consumption affected them all:D :D

[Dale Harris]

I know this is going back a bit but, Lu, when you referred to the record setting HP/Capacity thing, you do mean that the 3350 was the first recip certified at that level, don't you? I would imagine the "craftsmen" at Rolls would argue that the Type R as fitted to the S.6 exceeded it's capacity in HP, by a substantial margin too I think. It just didn't do it for long......... Were there not also 1700/1800 HP merlins towards the end of production??

[Specnut727]

What a great thread. It's taken a while to get through all the comments, but here are a couple I'd like to add.

To 411A The Wright R-3350 is an amazing engine. Is anyone aware of another 'turbo compound' engine, where exhaust driven turbines put power into the crankshaft, as well as driving the compressors ?

Have you seen any literature on the Wright R-2160 Tornado ? 42 cylinders (6 rows of 7), liquid cooled, one overhead cam for each of the 7 banks etc. An amazing engine, but never got into production as piston engines were overtaken by turbo props. A work mate of mine has a book on the Tornado project. It's worth a look.

To Dale From my notes, the last of the Merlins (Model 133/134 as fitted to the last of the Mosquitos and Sea Hornets, had an output of 2,030 hp. This may be the best hp/cubic inch before the racers started to tweak them and the big P&W's.

[Feather #3]

Just to correct an oft made error, as quoted by S'nut727;

the Power Recovery Turbines [PRT's] on CW R-3350's only provide power to the crankshaft. They have nothing to do with the induction system of the engine, nor are connected to anything else on the a/c. ;)

G'day :D

[Specnut727]

G'day Feather. Thanks for pointing that out. I learn something every day.

I went looking for more info, and my questions were answered. I hadn't realised that the R-3350 has a 'conventional' centrifugal supercharger at the rear of the crank. Having a totally separate induction system explains how the PRT's could be an 'add on' to the later variants.

[Flash2001]

Were the engines in some B-17 aircraft not turbo-compound?

After an excellent landing you can use the airplane again!

[Lo 'n' Slo]

Regarding the Bristol Hercules engines, the RNZAF Freighters were fitted with the Hercules 735s producing 2000 hp each. The oil consumption was 1 imp gallon per hour per engine. From memory there was 11 useable gallons in each tank.

Fuel consumption however, was a different matter. With full tanks and frugal power settings, you had over 12 hours endurance. Effectively, the aircraft was oil-limited!

The sleeve valve construction was a marvel! Without the limitations of fragile conventional valves, the cylinder head was as robust as a ceramic convenience. "Overboosting" was just not a problem. The standard way of clearing a mag drop was to apply full boost and min RPM and read the paper for a few minutes. Whatever was fouling the plugs was burned off in short order and the drop disappeared.

On one occasion this didn't work and after taxying back into the line, a wise old engineer (bless his oil-stained heart) tried another trick proscribed to mere aircrew: Max boost, max RPM and a series of slam-cuts of the throttle. Seemed to have the desired effect.

I was given an audio casette of Bristol Freighters starting up, taxying, running-up, taking off, cruising and shutting down. It was recorded at Blenheim NZ, of SAFE Air freighters. Forget who recorded it and having long misplaced it would be grateful if somebody could tell me where to get another. No narrative, just the mellifluous melody of the "Ug". Not a great conversation starter with the ladies though - can't imagine why? ;)

[Specnut727]

G'day Flash.

I think the later B-17 models had Wright R-1820's at 1,200 hp each. I think they had GE built turbochargers in the nacelle behind the engine, feeding air to the crankshaft driven centrifugal supercharger. I can't recall if they had 1 or more turbos per engine. Hence 2 stage supercharging, rather than turbo-compound.

Does anyone know of other turbo-compound engines than the R-3350 and possibly Napier models as mentioned in an earlier post ?

[Lu Zuckerman]

1) I believe that power recovery turbines were first used on heavy-duty freight engines powered by steam. Instead of the steam being vented from the steam chest or through the funnel it was ducted to the turbines and converted to mechanical energy, which was tied into the driving system.

2) My statement about the 3350 turbo compound being the first reciprocating engine to develop more horsepower than its’ cubic displacement came from a US Navy publication. The article claimed 3500 HP.


:cool:

[GotTheTshirt]

Spec,
In 1945 some Merlins were giving 2,780 HP ( with Monomethyl aniline fuel additive. ) This was at 36 lbs boost.

The biggest RR engine was the Eagle which was rated at 3,500 HP

The Napier Sabre ( In Typhoons) gave over 3,000 HP .

Turbo compounded engines generally means that the engine is mechnically assisted by the turbine wheras turbocharging is using exhaust gases to increase the induction pressure.
Supercharging is an engine driven compressor which also increases the induction pressure.
An interesting engine was the Napier Nomad which was a diesel and gas turbine driving the same propeller shaft

Many of the superchargers were 2 speed ( high and low blower) and some were 2 stage ( one supercharger behind the other) and some Both 2 stage 2 speed.:D :D

The last P&W radial was the 4350 which went over 4,000HP and designed for the DC7. Douglas went for the Wright engine at 3,700 HP because it was lighter. ( and also Super Connie)

[411A]

Actually Tshirt, the Pratt&Whitney R4360 (Wasp Major) was specifically developed for the Consolidated-Vultee (Convair) B-36. The only civil type that used this engine was the Boeing 377 Stratocruiser.

The largest CurtisWright R3350 turbo-compound engine fitted to the DC-7 was rated at 3400 hp (DC-7C, R3350EA4). In addition, the P&W 4360 was never considered for the Douglas DC-7 series, at least according to the engineering project manager for the DC6/7. Knew him well.

[Specnut727]

I'm getting a little off the original Radial theme, but there is so much great info along the engine size/power topic.

G'day Tshirt, here are some more comments.

1. I didn't know they pushed Merlins so hard back then. 2,780 hp from 27 litres (1,650 cu.in) is pretty good.

2. Yes the Eagle (22) was BIG at about 46 litres (2,800 cu.in) but obviously a lot smaller than a R-3350 or R-4360. What a complex arrangement, H 24 and sleeve valves, but similar to the Napier Sabre. My info is that the Eagle 22 was only used in the prototype Westland Wyvern, and short lived as the Wyvern went to a turboprop.

3. Maybe RR's biggest 'production' engine was the Griffon at 36.7 litres (2,240 cu.in). I know of variants up to about 2,400 hp. What were the latest Griffons in Shackletons rated at ?

4. I think Napier Sabres went to about 3,350 hp in the Tempest. A LOT of power from 36.7 litres, but ran at 4,000 RPM to do it.

5. Thanks for your explanation of turbocharging and supercharging. I think some of the later Griffons had 3 speed 2 stage superchargers. Also, another variation was the variable speed supercharger drive in the Daimler Benz DB605 (fitted to Bf109).

6. There's a Super Connie flying in Aust (VH-EAG). I've had a close look at it with cowls open and the R-3350's look great. Sounds great too. Hope to get a flight in it someday.

7. In Bris there's a flying Sea Fury. The sound of the Centaurus with 5 blade prop is MAGIC !!!

8. I hadn't heard of the Napier Nomad, so I'll do some digging for more info.

[henry crun]

The Nomad was reckoned to be the most efficient piston engines ever designed.
A flat 12 supercharged (by an axial flow compressor) diesel of 41 litres producing 4100 hp.

For those of you wanting to know more about RR engines may I recommend Rolls Royce Piston Engines by A.A.Rubba, published by the RR Heritage Trust.

It covers the early engines through to the Exe and the Crecy.

There are photos, a wealth of detail on all the engines, and many cutaway drawings.

[Feather #3]

The HP debate between the R-4360 and the TC R-3350 I think ended up with a marginal win for the Pratt in normal ops [ie. not air racing.]

I believe the EC-121 Warning Stars in Vietnam had water injected R-3350's and they put out the 3,500HP+ mentioned. I'm doing some study at the moment for a spot of work next week and our charts only show 3,400HP with the 115/145 fuel [down to 2,880HP with 100 octane.]

What is great is that we can still see these leviathans of mechanical ingenuity operating in another century. If you happen to be at Avalon Friday week, don't miss the night show!!

G'day ;)

[411A]

Feather #3

For efficiency, the CurtisWright turbocompound engines were certainly much better with a specific fuel comsumption of (approximately) .36/pound fuel/HP/hour.
No other large piston engine could compare.
Reliable...well yes, IF operated properly.

Which generally meant...the pilot left it to the Flight Engineer.
After all, with many airlines, HE had to help fix it if it broke....:eek:

[Feather #3]

411A,

Absolutely!!

The major lesson airframe drivers of this ilk need to learn is that you can only do what the power the F/E can give you allows. Many praise the pilots for flying the a/c when, really, you almost do so at the whim of the F/E.

Having said that, when the DA engines were in vogue and being screwed into the ground in terms of efficiency with advanced spark and leaning, some of the pilots carried their own power setting tables which allegedly saved engines for little extra fuel burn. Fortunately, we have EA's which burn more fuel, but are infinitely more reliable!!!:p

G'day ;)

[GotTheTshirt]

411,

When Douglas designed the DC7 and were looking for an engine over 3,500 HP Pratt developed the 4360.

As I said Douglas went for the CW because of weight.
I find it strange that Douglas never even considered it because there was not exactly a plethora of 3,500 HP engines out there!:rolleyes:

The 4360 was also used used in the C119-C

[411A]

Got the T shirt

The 4360 design was started long before the DC7 was ever thought of...as I mentioned before, specifically for the B36.

When the 4360 was installed on the Stratocruiser, the rear row of cylinders (four rows of seven) ran very hot, simply because the 'twist' (ie; cylinder row offset) was the wrong way 'round, as the engine had been developed for a pusher design.

Sorry...never considered for the DC7...as I grew up less than a mile from where ALL of the DC7's were built, and knew many of the folks involved (engineering project manager a close relative), the 4360 was never on the designers table.

Flew 'em as well...nice aircraft, but noiser than the DC6 (except for the -7C)

Nice try tho....;)

[ChrisVJ]

Lots of info on the web about the Sabre.

Ran 3,500hp at 3,850 revs. Triple 2 stage supercharger used an enormous 400hp.

Finally tested to 4,000hp ( and this in 1942/4 no exact date.) Fascinating story about improved sleeves coming from the Bristol Taurus.)

Prototype Wyvern was lost when the Eagle quit and the prop would not feather for forced landing. Not Westland's greatest plane.

[Gog]

I visited the RNZAF museum at wigram last weekend on their open day and had a look at their sectioned Sabre.Quite complex but not as physically large as i would have thought for the output it achieved.
They also had a sleeve valve demonstrator there of the turn the handle type, A couple of turns while watching the sleeve do its stuff and its workings becomes crystal clear.Clever stuff.

[GotTheTshirt]

411,

[Sorry...never considered for the DC7...as I grew up less than a mile from where ALL of the DC7's were built, and knew many of the folks involved (engineering project manager a close relative), the 4360 was never on the designers table.]

The following is quoted from World Encyclopedia of Aero Engines by Bill Gunston

“The Mighty R-4360 had already passed its first test by June 1942 and later in the year was qualified at the unprecedented rating of 3,000 HP.
By VJ day it had been qualified at 3,500 HP.

The last throw was the R-4360 compound, which went beyond 4,000 HP. The vital application was the DC-7 and Wright won because the Turbo Compound was lighter and simpler. “

Of course this is a British Book, and Bill Gunston is a respected (but British)writer , I do live several thousand miles for where both the engine and DC7 were built and most of my relatives work on the buses
;) ;)


Isnt it strange how Pratt and Whitney got the twist the wrong way round. :confused: But then I suppose Douglas had already realised that
I guess this was before all the British designers emigrated there after the war.:p

[ChrisVJ]

For those of us brought up fooling around with auto engines the sleeve valve can be a bit of an enigma and what is interesting is how this apparent complexity can turn out, when done right, to be so reliable. It must be something to do with the lack of shock in the action and the relatively low acceleration of the parts.

It also has other advantages besides just the sheer size of the ports it allows, for instance the ability to renovate by just pulling and replacing the sleeve. Granted the high friction area between the sleeve and the block must make the power requirement for starting a bit of a nightmare.

Seems a bit surprising there is not at least one eccentric auto manufacturer out there building a sleeve valve engine instead of the four or even five valves per pot jobs that are around now.

[411A]

T shirt,

That's just the point, Pratt&Whitney designed it that way...the right way 'round, for the B36.
Used on the C124, B50 and some models of the P2V...was a basic military design engine. If you are ever in KSFO, take a ride down the 101 freeway to the Hiller Helicopter museum at the San Carlos airport.
There you can see a rotating cutaway of the 4360...lots of bits and pieces all flailing around in close formation....;)

[GotTheTshirt]

411A

Ok now I think I've got it !!

Pratt and Whitney, desperate to get into the radial engine business built an engine for the B36 which was a pusher engine.

Then to get more business they got it put into the C124, The C119 and the P2V but no one told them these engines were pullers rather than pushers.
Pratt thought that all they had to do was change the prop the other way round and bingo.

They then found out the hard way that the front cylinders were now in the back and it all went downhill from there.

Fortunately by then the all the jet engine people emigrating from Europe went to work for them and they got into the jet engine business and the rest as they say is history !:D :D

[Feather #3]

Ummm....

GGTs ,

P&W were in the radial business way before the R-4360!

The R-985/1340/1830/2000/2800 all spring immediately to mind [altho introduction of the R-2000 may be a bit out in this context?]

G'day ;)

[411A]

Tshirt,
Pratt&Whitney...desperate?

Ah, well no actually. The 4360 was used because it was available off the shelf, so to speak.

But on the other hand, the folks at General Electric (the American company) used their developmental talents with turbochargers, to lead the USA into the jet age. A rather joint British-American effort.
The Brits did indeed lead for awhile with turbo-shaft design.
The Dart and Tyne are two good examples.

But then Allison came along with the 501 series....superb.;)
Now there's history:cool:

[LowNSlow]

My dad always reckons that the Hercules sleeve valve design was most reliable and that the sleeve crank spindle, although small, rarely caused problems.

He only had 4 engine failures during his flying career and it was bits of German metal imposing themselves on good Bristol engineering that were to blame!

The poppet valve is not an elegant engineering solution is it. Functional yes, functional but requiring "constant" attention also yes. Unfortunately it's always the cheap and cheerful solutions that bean counters go for not the long term savings that good engineering can offer but cost a bit more in development. :rolleyes:

[Lu Zuckerman]

To: Feather #3

The R-985/1340/1830/2000/2800 all spring immediately to mind [altho introduction of the R-2000 may be a bit out in this context?]

Here is the complete listing of air cooled P&W Radial engines:

R-985
R-1340
R-1535
R-1830
R-2000
R-2180
R-2800
R-4360
R-1690
R-1860
R-2180A

Here is the complete listing of liquid cooled P&W reciprocating engines:

R-2060
H-2600
H-3130


:cool:

[Specnut727]

Lu, I think I've also seen references to R-1300, R-1590, and R-1820

Also an X-1800, but I think this may never have gone further than prototype stage, like the R-2060.

Did the H-2600 and H-3130 make it into production ?

[Feather #3]

Gee Lu, I did say immediately!

Thanks for the encylopediac listing. :D

Given that my list was of the more common types [plus, of course, the R-4360], would you mind giving some aircraft types to which the more esoteric [eg -1535: Hughes Racer?] models were applied, please?

G'day ;)

[Lu Zuckerman]

My source of information was the Aeronautical Vestpocket Handbook published by United Technologies Pratt & Whitney. Although there is reference to which turbojet engines were installed on which aircraft there is no reference to what airframes the more esoteric engines were installed on. I do not know if any of the lesser-known engines reached production. There were a lot of experimental aircraft that never reached production and I can only assume that those engines were designed for installation on those aircraft.

I would suggest you reference Janes as they once published a handbook on all the worlds reciprocating engines both production and experimental and they may have referenced the aircraft that the engines were installed on.

:O

[pigboat]

Here's a few of the scarcer types.

The P&W R1535 was a 14 cylinder Twin Wasp used on the Boeing 247 and the Bristol Bolingbroke.

The R1690 was a 9 cylinder single row that came as a direct drive or geared version. The direct drive version was used on the Bellanca C27 and the Sikorsky S4, and the geared version on the Martin B12, the FW 200 and the Lockheed 14.

The R2000 was of course used on the DC-4/C-54 and the DHC4 Caribou. I've also flown an executive DC-3 that had the R2000's installed. Great airplane. It gave you a gross weight increase from 26,200 to 26,900 lbs. for the passenger version, the same as the R1830-94 equipped version.

[Kasper]

Even numbers are possible - you just have to know where to look . . . at two stroke engines for example.

Koenig made a very nice little 4 cylinder radial two stroke for aircraft - admittedly only 28HP but it is still a radial and it is a lovely smooth engine to fly with.

The reason that four stroke radials have odd numbers isn't to do with the which way to turn but with the natural vibration modes built up and re-inforced by power pulses.
ALL horizontally opposed twin 4 strokes are really not nice and to get one to run smoothly you have to either run a balance shaft or live counter-wieghts on the crank.

When you tack two together as a flat four its a bit better but to really get it smooth go for a flat 6 as the power pulses are then 120 deg apart and cancel each other rather than re-inforce.

The two stroke can get away with flat twins and radial fours because the number of power pulses is doubled.

And you don't have many problems with valve gear and oil loss on a 2 stroke because there ususally isn't any and if it stops spitting oil that's when the trouble starts.

And finally, not all radials use master/slave con-rods with offset pins giving eccentric slave motion to the crank shaft. There are engines that use slider/slipping slave con-rods but they are in the minority and it is the offset pins that people remember.

TTFN

[atb1943]

If anyone is interested I would be happy to copy and mail the six pages I have found in Flight of 16 February, 1939 entitled 'Sleeve-Valve Development', the story of the successful work of the Bristol Company: Mr. A.H.R. Fedden's R.Ae.S and I.A.E. paper. Drop me an email to [email protected]

...and I might add the nine pages published a few weeks later 'Rise of the Radial'..!

[henry crun]

Even better is the chapter in "Fedden - The life of Sir Roy Fedden" by Bill Gunston, published by the RR Heritage trust.

The book is a worthy addition to the bookcase of anyone interested in sleeve valves and radial engines in general.

The RRHT have a web site which lists the books they publish:
in addition to those about cars there are plenty to interest the aviation engine enthusiast.

PS: ATB, not trying to steal the thunder from your very generous offer, only pointing out other options.

[atb1943]

No probs at all with that, Henry. I do feel, however, that original, unadulterated, magazine articles offer a certain charm in comparison to a book over which the author has perhaps had time to evaluate all the information and arguments available to date. Interestingly enough, Felden presented his paper to Rolls-Royce a few weeks later and was apparently inundated with questions.

cheers

Bluebottle

[Lu Zuckerman]

Many moons ago at Ft Eustis, Virginia the first H-34 AMOC (Aviation Maintenance Officers Course) had just completed a teardown and build-up of an R-1820 engine. The engine was installed on a test stand and a test club (a wooden prop that acted as an air brake on the engine) was mounted on the shaft. Although the club was to be mounted on an 1820 engine the engine was assumed to have a geared reduction. This engine did not and when they ran the engine up to 2100 RPM the test club was overstressed and it exploded the engine over reved and tore itself apart. The exploding club destroyed an adjacent APU and a piece of wood hit an observer several hundred feet away putting him in the hospital.

:eek:

[411A]

Lu,
Happens elsewhere as well.
Just three days ago watched with dismay as an R1820 was mounted on the number 4 position of a DC4 for a ground test run...with a DC4 prop installed (yes it fits, but not recommended).
Run up to takeoff power, the engine went bang....two cylinders separated from the case.
Expensive study....in what not to do.:rolleyes:

[HectorusRex]

Perhaps Lu, you could steer me in the direction of which dash# R1820 was direct drive, as I can find no mention of such a version in the material at my disposal.
Thanks, HectorusRex

[Lu Zuckerman]

To: HectorusRex

The R-1820 used in the H-34 (S-58) was direct drive. The gear reduction took place in the main transmission. I believe the R-1340 and R-1300 used in the S-55 were also direct drive.


:cool:

[nicholas_hosties]

Great info regarding British and US radials but has anyone had any dealings with the German Siemens 7 cyl radial with dual carbys and compressed air start. I think mainly used on Fockewulf Stietzler a/c.
Any hint or tips would be greatly appreciated.
I was once told by an old T6/Harvard driver that due to the large moment arm at the prop tip and turning the prop by hand it was possible to do more damage if you encounted a hyd lock than with the starter motor which had a resonably low set clutch, he was only a short arse and I assumed he just could'nt reach. R985 engine.

[pigboat]

According to the info I have, the R1820 F-50/60 DD was also used in the Curtiss Shrike A-12, F-11C, Helldiver SBC, the Grumman F-3F1, BF-2C, the Northrop Delta II, the Vultee V-11 and the Douglas P2D-1.

[LowNSlow]

nicholas_hosties the Siemens was also used in the Bucker Jungmeister. There's one being restored in Spanhoe with the original engine. Why is the valvegear open I ask myself? Is it to make sure that a sufficient amount of oil gets onto the airframe :confused:

[GotTheTshirt]

Nicolas.
The device used for tuning the engine by hand to break the hydraulic lock is called your fingers.
The prop blade is very sharp and believe me if there is any resisitance, torque slippage is caused by the level of pain that you can withstand.:D ;)

Lu,
mentioning the P&W Aeronautical Vest-pocket Book, I dragged mine out and there were the list of engines together with the font of aeonautical knowledge.
I notice mine was dated 1966 !!:eek:
Did they produce one later ??

Very nice ref source:D

[Lu Zuckerman]

To: GotTheTshirt

Mine is the twenty-first edition. First printing dated May 1990

:cool:

PS: If anyone is interested in getting one you will either have to finagle one from your local P&W rep or, you can buy one from P&W customer relations. The part number is P&W079500. They are fantastic and have a lot of engineering info.

[HectorusRex]

Thanks Lu.
Not enough lateral thinking on my part, as I had ignored such vehicles that have their wing surface travelling faster than the fuselage:O

Thanks Pigboat.
My source, Allied Aircraft Piston Engines of WWll, ISBN 1 85310 734 4, does not specify any dash F-50/60 DD, as the references make no mention of a "DD", and neither do they reference any rotary winged aircraft.
Many thanks for the 'heads up':O