Radial vs radial

[rogerwilko]

Any advantages with the Wright cyclone 1820 over Pratt Whitney 1830? Seems the 1830 would be more complicated and expensive for similar horsepower.

 

[tomo pauk]

I'd say that it depends what application of a particular engine it is. If one want's a smallish well streamlined fighter, where the smaller frontal area matters, then better use the R-1830.
If the application is a multi-engined aircraft (bomber, transport), the R-1820 should be as good as the R-1830. For a single engined bomber (SBD class or similar), my guess is also that R-1830 has no advantage. Sensible choice (due to price) might dictate the R-1820 in these categories.

The R-1830 was also available in 2-stage supercharged variant from 1941, that is going to give notably more power above 16-17000 ft. OTOH, the R-1820 received, among other improvements, the water injection system, so it will be a better engine under ~12000 ft in late ww2.

 

[Shortround6]

It comes (at least somewhat) from company experience/philosophy. P&W had built two large 9 cylinder radials in the late 1920s

The Hornet A
Bore: 6 1⁄8 in (155.6 mm)
Stroke: 6 3⁄8 in (161.9 mm)
Displacement: 1,690.5 in³ (27.7 l)

And the Hornet B
Bore: 6.25 in. (158.8 mm)
Stroke: 6.75 in. (171.4 mm)
Displacement: 1864 cuin (30.54 L)

Early Cyclone 9 was
Bore: 6.00 in. (152.4mm)
Stroke: 6.875 in. (174.6 mm)
Displacement: 1750 cu in (28.7 L)

A 1/8in bore job brought it to
Bore: 6.125 in (155.6 mm)
Stroke: 6.875 in (174.6 mm)
Displacement: 1,823 in³ (29.88 L)

Pratt Whitney had some troubles with the large Hornet with burned pistons which were not occurring with the small Hornet and decided that smaller cylinders would be less trouble. NO production P&W engine used cylinders of the Hornet B size again. The R-2800, R-4360 and R-2180 (post war) ALL using Bore: 5.75 in. (146 mm) X Stroke: 6.00 in. (152 mm) cylinders.
Better fins and different piston design/materials might have helped but P&W decided that more smaller cylinders offered better cooling and a easier path to higher power.

Wright eventually got the R-1820 to much higher power levels than the R-1930 ever got to but these engines shared nothing except the bore and stroke of the older engines.

Old joke from the 1930s was that you could tell what kind of engines were in a DC-3 by looking at the pilot/s several hours after they landed. The pilots that flew Cyclone powered planes had arms that were still shaking

 

[rogerwilko]

Thanks chaps. And unit cost comparison?

 

[XBe02Drvr]

you could tell what kind of engines were in a DC-3 by looking at the pilot/s several hours after they landed. The pilots that flew Cyclone powered planes had arms that were still shaking

I've ridden in Wright DC-3s and Pratt DC-3s and the difference in smoothness is big. Like a 1981 Hog vs a 1981 Honda GL1100 Goldwing. Same is noticeable between a Wright B-17 and a Pratt B-24. I got to ride both in the same day in return for bailing the Collings people out of a fix they were in regarding parts.
Cheers,
Wes

 

[MIflyer]

The R-1820 was lighter , about 1330 lb versus around 1440 for the R-1830. The later R-1820's got up to 1350 hp while the R-1830 topped out at 1200 hp.

The R-1820 was larger in diameter than the R-1830 and therefore not as good for streamlining

The R-2000 was a slightly larger R-1820, designed to give the same HP as the the R-1830 when operating on lower octane fuel, such as the 73 octane that was normal before WWII. With the higher octane fuel it could give 1350 hp in the later versions. Presumably it was heaver than the R-1830. It was used only on the C-54/DC-4.

 

[Shortround6]

There were some late war R-1830s that made it to 1350hp. They used some trickle down from the R-2800 in the form of forged cylinder heads, better finning and a few other changes. Main use was on the Navy PB4Y Privateers.

73 octane fuel went away (except for light planes) in the very early 30s. The US had shifted to 80, then 87 and then 91 octane before going to the US 100 octane.
Late R-2000s were good for 1450hp but that is for take-off. Their power at altitude might be only about 100hp more than an R-1830.

Both the R-1820 and R-183 went through a lot of versions and both gained a lot of weight. The 1350hp R-1830s went more than 1500lbs and despite having a single stage supercharger weighed about the same as the Wildcat R-1830s with two stage superchargers.

 

[XBe02Drvr]

The R-1820 was larger in diameter than the R-1830 and therefore not as good for streamlining

We had an 1820 at mech school that we took apart, put together, and ran on a test stand with a club prop. Sounded and acted like it wanted to shake itself to pieces, especially at idle as the articulated counterweights on the crankshaft clanked back and forth. The caster wheeled test stand had to be tied down securely to padeyes in the ramp to keep it from jumping around, and had to be re-tightened after every run.
One day the school director's friend brought his Pratt powered DC-3 in for an engine inspection, and we got to turn it up. Smooth as a baby's behind. A two-throw crankshaft has it all over a single throw, even if it makes for a heavier, more expensive engine; the wear and tear from heavy vibration is huge with such things as engine mounts, cowlings, exhaust plumbing, and engine accessories.
Cheers,
Wes

 

[PWR4360-59B]

So all this sounds like if you wanted all the rivets and bolts plus other parts to stay on the plane, and not vibrate out the R-1830 was the best choice then?

 

[XBe02Drvr]

So all this sounds like if you wanted all the rivets and bolts plus other parts to stay on the plane, and not vibrate out the R-1830 was the best choice then?

Why do you think so many Wright powered C-47s and C-53s were converted after the war to Pratt powered "Super" DC-3s (poor man's version; not to be confused with the "real" new manufacture Super DC-3 with its uprated 1820s and its stretched cabin and enlarged tailfeathers).
The mods included Pratt engines, Ham Std props, streamlined cowlings, landing gear doors, and quieter exhaust plumbing. Those planes served northern New England and "north slope" New York state right up till 1966, when they were replaced by FH-227s. My first airline flight was on one of Northeast's "3s" to Boston the day after JFK was shot.
Cheers,
Wes

 

[PWR4360-59B]

The DC-3's are nice old planes, I spent alot of time around them in the day. And a few flights as well. I liked that you could manually pump up the hydraulic system. The windshield wipers were hydraulic. Some even had inertia starters, don't need no battery's to start them. And all in that fleet were all R-1830's.

 

[XBe02Drvr]

Some even had inertia starters, don't need no battery's to start them.

Hand crank inertia starters? Isn't there something in The Constitution about "cruel and unusual"?? Imagine a hot afternoon in Key West, and Air Sunshine's only flyable DC-3's third Miami turn of the day has just deplaned, fueled and loaded and is ready to start engines for its last turn. The asphalt ramp is soft in the heat, the cowlings you could fry eggs on, the start cart is inop, and the aircraft's tired battery won't crank vapor-locked #2 engine. Do you know how much prolonged gut-busting effort in the hot sun it takes to crank that flywheel up to speed to turn that engine? Some poor Cuban guy working for Air Sunshine died of heat stroke back in 1974 under those circumstances.
Condolences,
Wes

 

[PWR4360-59B]

Hand crank inertia starters? Isn't there something in The Constitution about "cruel and unusual"?? Imagine a hot afternoon in Key West, and Air Sunshine's only flyable DC-3's third Miami turn of the day has just deplaned, fueled and loaded and is ready to start engines for its last turn. The asphalt ramp is soft in the heat, the cowlings you could fry eggs on, the start cart is inop, and the aircraft's tired battery won't crank vapor-locked #2 engine. Do you know how much prolonged gut-busting effort in the hot sun it takes to crank that flywheel up to speed to turn that engine? Some poor Cuban guy working for Air Sunshine died of heat stroke back in 1974 under those circumstances.
Condolences,
Wes

I was a 150 some lb teenager at the time and had no problem winding up the inertia starter. It also had electric motors to do the same so all normal starts were with them from the cockpit. There was one time the pilot couldn't get the solenoid to engage it and I had to pull the engage handle after the wheel was wound up.

 

[XBe02Drvr]

I was a 150 some lb teenager at the time and had no problem winding up the inertia starter.

I'm glad I didn't meet you in a dark alley back then; you must have been a bodacious 150 lb teenager. I've only had one experience with a hand crank inertia starter, and it was an eye opener. After a night at the EM club at NAS Memphis a boot camp buddy who was a student in Aviation Machinist Mate School ("engine mechanics" to landlubbers) was ragging me about how "tweets" were a bunch of pussies. He challenged me to prove I wasn't by cranking over an 1820 they had on a stand outside the shop. Turns out they used this as a disciplinary tool instead of pushups or manual of arms. You worked off your "Delta Sierras" by cranking the inertia starter however many cycles you were ordered to. It rattled and screeched and sounded like it was chewing its bearings up and about gave me a hernia. The kid doing sentry duty was too amused to interfere in our shenanigans, and we bought him a beer next time we saw him in the EM club.
Cheers,
Wes

 

[PWR4360-59B]

Maybe something was wrong with that starter, they really are not all that bad to crank. Yeah slow at first, it did not take long to get it up to speed.

 

[soulezoo]

All this talk about hard to start reminds me of my C-141 days after the switch to JP-8 especially.

 

[XBe02Drvr]

All this talk about hard to start reminds me of my C-141 days after the switch to JP-8 especially.

Back in my day Naval Air was kind of schizophrenic about jet fuel, using JP-5 at sea and JP-4 ashore. So every time a squadron deployed, all the engine fuel controls and fuel management systems had to be recalibrated. Fortunately that was the ship's problem on the way out, but ours when they returned from the cruise. Since high power turnips were supposed to be done under "standard atmoshphere" conditions, or as close as possible, the coolest time of day in the Florida Keys was 0300-0400, which wasn't popular with the locals. (Nor with the inmates - my barracks was 200 yards from the alameda chocks.)
Cheers,
Wes

 

[davparlr]

All this talk about hard to start reminds me of my C-141 days after the switch to JP-8 especially.

When were you involved with the C-141? What did you do and when? I was a pilot based at McGuire AFB some forty odd years ago. I was impressed that the C-141 could pretty well burn anything you could put through a pipe, JP-4, 5, avgas, just had to note the limitations. Don't think we had any JP-8 .
I do have an engine start story however. We were getting ready to leave outta Elmendorf AFB, Alaska on a bitter cold day. The aircraft had set over night and there were heaters pumping air into the plane. I got one and two engines started, but when I engaged the starter for number three, nothing. Old head, many stripped flight engineer stated that the air valve was probably frozen and told the ground crew to get a rubber mallet and hit the valve to free it. He reported that he did and I tried a start. Nothing. The engineer got up and went out and then came on the intercom asked up to try again. Starter engaged and the engine started. He came back up, sat down and said the guy was beating on the generator!

 

[soulezoo]

When were you involved with the C-141? What did you do and when? I was a pilot based at McGuire AFB some forty odd years ago. I was impressed that the C-141 could pretty well burn anything you could put through a pipe, JP-4, 5, avgas, just had to note the limitations. Don't think we had any JP-8 .
I do have an engine start story however. We were getting ready to leave outta Elmendorf AFB, Alaska on a bitter cold day. The aircraft had set over night and there were heaters pumping air into the plane. I got one and two engines started, but when I engaged the starter for number three, nothing. Old head, many stripped flight engineer stated that the air valve was probably frozen and told the ground crew to get a rubber mallet and hit the valve to free it. He reported that he did and I tried a start. Nothing. The engineer got up and went out and then came on the intercom asked up to try again. Starter engaged and the engine started. He came back up, sat down and said the guy was beating on the generator!

I was with -141's '87-'97 at Travis as a FCC (Flying Crew Chief) and one of the very last to leave the squadron as they were retired. I spent a lot of time on Golden Bear (-088) which was the first -141 delivered to the AF and now on static display at Travis. The stuck starter valves is a common theme on start up along with the fuel control linear actuator. Many times as FCC I'd go out with the speed handle and rubber mallet to bang away on those things for engine start. And it wasn't just cold, they'd do it anytime. Once during Desert Shield in Al's Garage (Al Kharge, Saudi) it was over 120* and all 4 engines had this problem and I had to bang away on them just to get out of there. It was always entertaining when we had pax to see the look on their face when I'd have to go down with just the hammer and speed handle to "fix" the plane.

When the switch was made to JP-8, which was less volatile, the engines had a tough time igniting when cold. So during start up a lot of raw fuel would get dumped out the back while trying to light and when it did light it made for a hell of a wienie roast! No one knew -141's had afterburners... lol.

 

[XBe02Drvr]

All this talk about hard to start reminds me of my...

...days working as a fueler at NAS Key West after my EAOS. Key West was a favorite "weekend liberty port" for active, reserve, guard, Canadian and Latin American squadrons from all over North and Central America and the Caribbean, and on a Saturday morning the transient line could sometimes be a veritable museum of vintage and esoteric aircraft. It was not unusual for these visitors to need vintage ground support to go with their vintage machines. GSE maintained a variety of obsolete start carts, fire bottles, and oxygen servicing equipment, and we had to keep spare gravity nozzles and hoses on our JP trucks. Hard starts, overprimes, tailpipe fires, and fuel spills were frequent, and the CFR guys were on a hair trigger.
One day we got "raided" by the "friendly enemies" of the 158th Defense Systems Evaluation Squadron, VT ANG. Three EB-57s hopped over the mangroves that surrounded the perimeter and came right across the field so low they had to climb over the F-4s and KA-6 sitting on the hot pad. (And my fuel truck!) Total surprise; they totally foxed all the radars, and nobody saw them til they were over the field.
So after the shouting was over, and I had laboriously (gravity) fueled all three, it was time for them to leave. The flight leader (a full bird Col.) walked me and the line chief over to the CFR hangar for a prestart briefing with the firefighters. He pulled a black donut-shaped object about the size of a small Christmas wreath with a couple of wires on it from his pouch and said:"This is a starter cartridge. It's how we get our jets going. It's reliable and not dangerous, but it does make a formidable puff of smoke and a sound like a fuel fire lighting off. THIS IS NORMAL! It looks and sounds as if the jet is on fire, but IT'S NOT. When we start engines, you're welcome to stand alert in your trucks with engines running, as seems to be SOP around here, but stay here by your hangar and DO NOT APPROACH our aircraft UNLESS you get a radio call! Got it?"
So when they manned up, they left the crew chief/flight engineer/ECM operator of the junior aircraft outside to act as ramp control, and he walked out in front and stationed himself half way to the CFR hangar.
Turns out the Colonel was a wise old bird, as when the first cartridge went off with a pop and a flash and a whoosh and an impressive cloud of black smoke, sure enough, the siren went off and the fire trucks came charging across the ramp, silver suits on and foam turrets manned. The crew chief ran out in front of them and tried to flag them down, but they swerved to drive around him, causing him to grab the boarding ladder of the lead truck and pound on the driver's window. The driver said something to the effect of: "Buzz off, we've got a fire to put out!" About then the truck stopped and started to engage its pump drive, so the crew chief jumped down and pulled the emergency disconnect on the pump drive and closed the manifold distribution valve on the pump, then ran around and did the same to each of the other trucks as they rolled to a stop. By that time, the smoke cloud was clearing up to reveal an EB-57 with one engine running and a very pissed-off Colonel at the controls turning the air blue over the radio. Fortunately, no foam was sprayed and no engines were wrecked.
The Keystone Kops couldn't have played it better! Your defense dollars at work.
Cheers,
Wes