Re: Before it was Rare Bear
Quote:
Originally Posted by
knot4u
I'm not sure that the exhaust system in that photo is the version that was installed during the Bearcats glory days but I'd be happy to be corrected. The good exhaust was a nightmare to work on. I can recall questioning why anyone would put together a puzzle that cantankerous and being told it was "tuned", the pipe from each cylinder would join the pipe from a cylinder preceding in the timing order to help exhaust gas scavenging and contribute a small amount of thrust. The exhaust exits also worked as a venturi (exhaust augmenter), the exhaust actually helped to cool the engine (unless part of it failed) by motivating the air under the pressure cowl to exit. That system had gone through so many heat cycles that it was almost beyond repair and anytime it was disassembled it was a nightmare to reassemble because nothing fit, nothing would line up and you'd have to start taking it apart again. With all of that said, it should've been replicated not scrapped.
Lyle had flown on TWA trips with George Byard's brother. That is the initial way that Lyle got to meet George and start the most beneficial support that the Bearcat racing project would ever have. George Byard owned Aircraft Cylinder and Turbine a major player in the radial engine business in Southern California. The first rodent infested, trash covered engine that the team received came from AC&T and George Byard. They didn't have any exhaust, not did anyone else have exhaust for an R-3350 in a Bearcat QEC, however AC&T did have several crates of exhaust that had been removed from R-3350 engines for Constellation and DC-7 aircraft. Lyle bought a complete engine mount and exhaust from a Skyraider, those parts didn't even think about fitting on the Bearcat!
So one of the crates was brought down to the Compton hangar F8 (the first hangar Lyle had) and was used by Cliff Putnam to build the first somewhat crude but effective 2 into 1 exhaust set on the Bearcat. Over the years that exhaust that Cliff had built was maintained on ocassion as it would break often out of those parts that were in the crates of exhaust.
One of the things that Dave Cornell brought to the table was his history in motorcycle racing. Dave as he became more involved in the Bearcat decided that a complete revamping of the exhaust system was going to be necessary. Cliff's original system while designed to be two cylinders down to one exhaust pipe which was good didn't take into account pairing of the cylinders by firing order in order to maximize the scavenging effect of the cylinders paired to achieve two to one exhaust pipes. Dave went back to AC&T who still had crates of exhaust pipes for the Turbo Compound engines picked up more pipes and started over. He was having Rich Donahue take the pipes from the crates and by cutting and fitting the Dave and Rich fitted the pipes in the pairing of cylinders to provide the optimum effect of scavenging.
The next and most secret part was to optimize the back pressure to exhaust outlet velocity by machining rings that were shaped and sized in a manner that would make the best use of the pressure cowl design that Dave and Bill Prewitt were installing based on the DC-7 cowling. Bill was an excellent sheet metal fabricator and was able to bring to reality the design Dave envisioned.
The spinner off a Bristol Beverley was adapted to the four blade propeller and we were able to close down the gap between the spinner outside diameter and the cowlings inside diameter to a ridiculously small looking dimension. Without proper exhaust augmentation the engine simply would not have had enough air going through the cowling to cool the engine. A metal plate system was developed to increase the venturi effect between the higher velocity exhaust gasses and the slower cooling air. Ultimately flight tests showed that at speed the "flat plate" area between the gap of the cowling and spinner was negated to near net zero. The spinner afterbody that was fabricated by Prewitt under Cornell's direction shaped the airflow to get the maximum use of the air going through the cowling. To finish the package the baffles were installed using silicone sealer to control the airflow better. High temperature rubber pieces were installed to manage the airflow at the cylinder base gaps.
Torque meter readings showed that the augmented improved exhaust system was good for close to 300 horsepower, the engine cylinder head temperature was reduced and flight test numbers showed a significant speed increase due to the reduced drag.
So a really good system started by Cliff Putnam was perfected and included in a package of air/engine management thought up by Dave Cornell brought to life by the metal shaping magic of Bill Prewitt. Rich Donahue gets credit for training the exhaust pipes to fit as needed. Lief was correct, working on the exhaust was a Bearcat kinda deal.
Re: Before it was Rare Bear
Quote:
Originally Posted by
BellCobraIV
Lyle had flown on TWA trips with George Byard's brother. That is the initial way that Lyle got to meet George and start the most beneficial support that the Bearcat racing project would ever have. George Byard owned Aircraft Cylinder and Turbine a major player in the radial engine business in Southern California. The first rodent infested, trash covered engine that the team received came from AC&T and George Byard. They didn't have any exhaust, not did anyone else have exhaust for an R-3350 in a Bearcat QEC, however AC&T did have several crates of exhaust that had been removed from R-3350 engines for Constellation and DC-7 aircraft. Lyle bought a complete engine mount and exhaust from a Skyraider, those parts didn't even think about fitting on the Bearcat!
So one of the crates was brought down to the Compton hangar F8 (the first hangar Lyle had) and was used by Cliff Putnam to build the first somewhat crude but effective 2 into 1 exhaust set on the Bearcat. Over the years that exhaust that Cliff had built was maintained on ocassion as it would break often out of those parts that were in the crates of exhaust.
One of the things that Dave Cornell brought to the table was his history in motorcycle racing. Dave as he became more involved in the Bearcat decided that a complete revamping of the exhaust system was going to be necessary. Cliff's original system while designed to be two cylinders down to one exhaust pipe which was good didn't take into account pairing of the cylinders by firing order in order to maximize the scavenging effect of the cylinders paired to achieve two to one exhaust pipes. Dave went back to AC&T who still had crates of exhaust pipes for the Turbo Compound engines picked up more pipes and started over. He was having Rich Donahue take the pipes from the crates and by cutting and fitting the Dave and Rich fitted the pipes in the pairing of cylinders to provide the optimum effect of scavenging.
The next and most secret part was to optimize the back pressure to exhaust outlet velocity by machining rings that were shaped and sized in a manner that would make the best use of the pressure cowl design that Dave and Bill Prewitt were installing based on the DC-7 cowling. Bill was an excellent sheet metal fabricator and was able to bring to reality the design Dave envisioned.
The spinner off a Bristol Beverley was adapted to the four blade propeller and we were able to close down the gap between the spinner outside diameter and the cowlings inside diameter to a ridiculously small looking dimension. Without proper exhaust augmentation the engine simply would not have had enough air going through the cowling to cool the engine. A metal plate system was developed to increase the venturi effect between the higher velocity exhaust gasses and the slower cooling air. Ultimately flight tests showed that at speed the "flat plate" area between the gap of the cowling and spinner was negated to near net zero. The spinner afterbody that was fabricated by Prewitt under Cornell's direction shaped the airflow to get the maximum use of the air going through the cowling. To finish the package the baffles were installed using silicone sealer to control the airflow better. High temperature rubber pieces were installed to manage the airflow at the cylinder base gaps.
Torque meter readings showed that the augmented improved exhaust system was good for close to 300 horsepower, the engine cylinder head temperature was reduced and flight test numbers showed a significant speed increase due to the reduced drag.
So a really good system started by Cliff Putnam was perfected and included in a package of air/engine management thought up by Dave Cornell brought to life by the metal shaping magic of Bill Prewitt. Rich Donahue gets credit for training the exhaust pipes to fit as needed. Lief was correct, working on the exhaust was a Bearcat kinda deal.
Thanks for confirming my memories John, I hope I wasn't sharing too much. Now regarding my question about Juniors, have you given it any thought?
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Re: Before it was Rare Bear
So the story is even more complex than I thought. The end result did sound like to a large degree like Cornell thinking but I had no idea how complex the balancing of air coming in and air going out with the exhaust system could be. No wonder the Texas guys seemed to get lost in it all.
Here are a couple of shots from 2002 that show the developed system (or at least another stage in its evolution).
Re: Before it was Rare Bear
Quote:
Originally Posted by
wingman
In the meanwhile I'll post another Pete Behenna photo or two. So back in 1969 Lyle had an airplane shell, a remarkable crew coalescing, and parts coming in from around the country. He still needed an engine. According to Dell Rourk, Lyle went to see George Byard at Aircraft Cylinder and Turbine in Sun Valley, Ca.
AC&T had an old R3350 in the open out back of the shop -- it was scheduled for salvage and had been sitting back there in the weather with no plugs or stacks and rainwater in the cylinders. George donated the engine to Lyle's project. George Putman cleaned out the sticks, birdsnests, and other crap and with some help from the mechanics at AC&T managed to rebuild the motor.
John -- what was the timeline of all this? When did Lyle move the kit into the hangar? When was the fuselage more or less complete? When did Putnam get his hands on the engine and when was it actually hung on the airplane?
Neal
Neal,
I the second picture below in this thread some of the background pieces tell a lot of the story. On the floor straight behind the welding bottles is a surplus Skyraider engine mount. Hanging from the wall above the engine mount on the airplane is a brand new F8F engine mount, the shiny front nose bowl of a Bearcat cowling is hanging from the ceiling attached to the cowl framework. Those new Bearcat parts came from Palley's Surplus. Palley's Surplus was a business that had tons of brand new and salvaged warbird parts. Had a collector been more visionary than the scrapman that bought a lot of the inventory they would realize the treasure of the ages. But alas most of that was scrapped in the early eighties....sad.
Cliff was in the process of building the original exhaust which was a very good system, Cornell just put together and tuned the final package so we'll.
2 Attachment(s)
Re: Before it was Rare Bear
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Re: Before it was Rare Bear
There's also this one -- during the original buildup of the exhaust system?
Re: Before it was Rare Bear
Quote:
Originally Posted by
wingman
So the story is even more complex than I thought. The end result did sound like to a large degree like Cornell thinking but I had no idea how complex the balancing of air coming in and air going out with the exhaust system could be. No wonder the Texas guys seemed to get lost in it all.
Here are a couple of shots from 2002 that show the developed system (or at least another stage in its evolution).
I don't know how many times Fred, Gil and myself took that apart and reassembled it (after work, we all had full time jobs) in a t-hangar at Van Nuys (in the summer at night when it was still 100F, or when it was 30F in the winter, in the hangar). It was all inconel, and as John said fabricated from another application. I recall Greg Shaw brought in an oxy-acetylene setup to look for cracks, he'd take each piece (while it was disassembled) and heat all of the joints up looking for cracks, the cracks were apparent when the part was red hot and we'd send it out for repair. Every time we took it apart we always tried to remember how we'd done it, unfortunately most of the time half of the pieces would just fall out after we loosened a bunch of clamps. This was not uncommon, that airplane would fight you every inch of the way if you were working on it. So despite our best efforts and recent experience trying to reassemble it was always a challenge. Like I said, you'd think you were 1/2 to 3/4 of the way to the finish and nothing would fit and you'd have to almost have to start over. The key was to assemble everything loosely (Hang On Loosely, .38 Special, look it up) but some of the tubes would require tightening before they were made impossible to access by the rest of them, and then it wasn't just left and right because it was a round motor so eventually top, bottom and left and right had to join. And you better not pre-stress any of these pieces because they'd be sure to at least crack, or at worst fail at the worst possible moment and making sure none of them were rubbing each other the wrong way was always a challenge and another reason to start over. Like I said before it was a challenge (nightmare) but once it was installed it worked. It should have been replicated, not replaced.
https://m.youtube.com/watch?v=tFUi8Wa03hc
Re: Before it was Rare Bear
Quote:
Originally Posted by
wingman
There's also this one -- during the original buildup of the exhaust system?
That was the photo I was referring to in my last post, yes.
Re: Before it was Rare Bear
Quote:
Originally Posted by
wingman
So this photo?
That photo shows the brand new QEC sitting on the ground to the left of the plane.
Re: Before it was Rare Bear
