Warbird Information Exchange

I agree, Blasphemy!!!!

" You can fly a Pratt further than you can ship a Merlin "

Can't remember where I first heard that, but it's just as funny now as it was then.

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Expert:
Ex: Former.
Spurt: A drip under pressure.

I've got another question about the engines. Why is it that you can obtain drawings for the aircraft, but nothing fro the engines?

I seem to recall it is because most of the WWII era aircraft were designed and built under Gov. contract, therefore in the public domain. Most of the engines were designed and built by private concerns, and are (were) protected for proprietary reasons.

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Expert:
Ex: Former.
Spurt: A drip under pressure.

Just as true too! Another good one from a noted Mustang guru in FL, "The only thing better than having a Mustang in your shop for MX is watching it leave!"

Now if you could put an R-2800 on the front of a Mustang... Come to think of it, you'd probably have an FW 190!

John

"boom boom round round propeller go"

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S.

On the early Corsair the Throttle Quadrant had a 4th lever that was used to shift the Aux Blower.
Remember all the B series engines had a Supercharger in the power core (between the nosecase and the accessory case). The Accessory case on the R-2800-8 in the F4U-1 or FG-1D had an Aux Supercharger setup in addition located in the larger Accessory housing. IIRC the labels on the Throttle were Neutral, Low and High. In Neutral the Aux Blower was in idle and the main core supercharger was running. Low and high activated the Aux blower running it at different speeds.
The Carb on the -8 was upstream of the main blower but downstream of the Aux Blower. It would grab air from the inlets in the wing leading edge, Compress the air if running in Low or High Blower, duct that air to the intercoolers in the wing leading edge, then duct them to the carb so the carb could have pressurized air flowing through it, and then the air would run into the main supercharger where the fuel was introduced just prior to the supercharger wheel.

Transport Heads come in a couple different models. -500 series and the -620/720 series. This depends on the original type of engine they were installed on. 620 type has an enlarged front portion of each head so the valve covers of each type are not interchangable. Valve covers of -7 or -9 are interchangeable with the 500 type IIRC.

BE currently has -620 heads.

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Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

Rich,

I'm not sure the 500 heads are true transport heads per say but could be wrong. I've been told they were the heads built for/used on the Casa built airplanes that used the Merlin. If my memory serves...You remember correctly on the 500, -7, -9 cam covers. That said, among other things, the cam drive and rack is a slightly different arrangement than the -7 and -9...in my opinion, much less user friendly. We have the 500's on Red Tail right now but have two spare set's of -7's. When it comes time for H&B job next fall the 500's are getting traded out for a set of -7's. I'd rather standardize on one type than have mix and match.

John

Airplanes are built to be taken apart, and airframes are designed to be field repairable. To do the former, or rather to put them back together, you need accurate measurements for rigging and such. For the latter you need fairly detailed drawings to make parts to replace the damaged ones. You can build, or rebuild, most of any airframe with a surprisingly small number of tools and stock materials.

Engines are often replaced as units, and almost always are assembled from factory supplied parts. Engineering data for engines is usually provided in only it's exterior dimensions, and even at depot / MRO level engine internals are only described in clearances and specific dimensions.
Hacking a new crankshaft out of a billet, or casting a new crankshaft is a little involved.

Because of the differing needs for engine and airframe, airframe drawings in general are much more widely disseminated and easier to acquire, or to use as sources for new drawings. Complete engine drawings are not needed outside of the manufacturer and are closely held proprietary information.

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Lest Hero-worship raise it's head and cloud our vision, remember that World War II was fought and won by the same sort of twenty-something punks we wouldn't let our daughters date.

500 heads are a different generation from -7 heads. Seal on the cylinder liners is different IIRC. Casting thicknesses in the heads are thicker in the spots that caused problems. Exhaust studs are 3/8's rather than 5/16" on the -7 although the larger studs are often installed on the -7.
Personally I'd rather get the Roush treatment on a 500 head and return it to the engine rather than the -7 but each will do the job.
Casting molds for the 500 still exist and Roush might make new ones if the market will someday call for it.

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Rich Palmer

Remember an Injured Youth
benstear.org
#64- Stay Strong and Keep the Faith

BOOM BOOM, ROUND ROUND, PROPELLER GO

Don't Be A Dilbert!

Thanks T-28mike and shrike.

You ask a question, you get an answer.

Restoring-to-the-original is great, but if you're going to fly the airplane, you have to look at some things with an eye to being practical. For example you need a VHF radio and a transponder. And no one wants an actual WWII battery when modern ones work so much better. And no one is going to put WWII oil in a valuable old engine, and then actually go flying behind it. We all depart from true authenticity in some degree.

With the P-40 restoration that I oversaw, we elected to stay below 10,000' in flight. That meant we could do away with the complexity of the oxygen system. And that meant we didn't need the full-volume supercharger.

Refresher: a geared supercharger is just that, geared to the crankshaft. It's always linked. If the gear ratio is such that the impeller is designed to give maximum output at higher altitudes, then it would deliver too much to the engine at sea level if you pushed the throttle to the forward stop. You would exceed the intake manifold limits, and damage the engine. In other words, when down low where the air is thick you can't use everything such a supercharger can give you.

But it's still geared to the crankshaft, and the engine is still driving the impeller. Always. That robs power because the energy that is driving the impeller is not available to drive the propeller. It's gotta come from somewhere...

With our P-40, we have the correct engine for the "N", the V-1710-81. But ours has been modified to use a lower gear ratio, from 9.6-1 to 8.8-1. There was precedent for this in WWII. A number of P-40s that were being used Stateside in the role of advanced trainer were modified this way. They were "-81As". The advantage is the reduced supercharger output is still more than enough at low altitude. You can still get max rated performance at sea level (52"), which is where we need it for take-off and display aerobatics. But the rest of the time we're not powering up a high-volume supercharger flow that we can't use. This means better economy, and it's just easier on the engine as a whole. The extra energy that would have been consumed by driving the impeller to the higher speeds, is instead available to the crankshaft to drive the propeller.

Regarding high-altitude capability, I think many modern warbirds have made more or less the same choice, using whatever means are practical for that particular engine type.

Dave

I am consistently amazed by the well-thought out replies and the relative wealth of knowledge available on this forum. It makes perfect sense to me that due to the way most warbirds operate today that there would be some compromises to the original design. It also makes sense that many (most?) would be configured in such a way that they would be able to operate and perform safely while maximizing the time between costly overhauls, saving wear-and-tear, etc...Now I've been known to be guilty of a daydream or 2...but I still think if I had a Corsair, (or prob any other warbird for that matter...) at least once, I'd want to go on oxygen and take her up to altitude to see what kind of speed I could get out of her and pretend I was flying CAP! Haha! Anyway, enough said...thanks for the replies, all

Matt

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I'm looking for that buried Corsair(s) that I can dig up, pressure wash, and fly!

Where is the scale model? I bet my cousin who is curator for the Joe Martin Craftsmanship Museum would love to have this on display.

http://www.craftsmanshipmuseum.com/

Check out some of this work. No idea where they get the time.

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"There are old pilots and bold pilots but few old, bold pilots."