Radial Engines
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.
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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
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
Last edited by Shaggy Sheep Driver; 14th Jan 2003 at 10:16.
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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
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
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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.
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
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.
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
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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??
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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.
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.
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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
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
Last edited by Feather #3; 4th Feb 2003 at 01:15.
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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.
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.
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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?
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?
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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 ?
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 ?
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Several answers.
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.
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.
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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.
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)
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.
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)
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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.
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.
Last edited by 411A; 5th Feb 2003 at 04:01.
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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.
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.
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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.
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.
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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
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
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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....
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....
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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!!!
G'day
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!!!
G'day