Super charger

[raytoews]

Looking at the pics of the Bally Bomber, which is an amazing accomplishment, it looks like the unit between the prop and the engine might be a supercharger of some type.
Which got me thinking, Lycoming has that big flywheel on the front, turns 2700 rpm, replace it with a squirrel cage type fan, would it produce enough usable air to give a few inches of boost?
Relatively easy to build.
I remember reading way back when EAA was doing the mogas certification they had used an electric fan into the intake during ground runs and had seen "significant" increase in power.
I played with a Kcar with turbo many years ago and was impressed with the small amount of air pressure produced by the turbo which made a large difference in hp.
There was a discussion, I don't remember if it was here or on the Rvaitor about the ram air effect and it turned out to be not that big a deal.
I have an RV style carb heat and notice very little difference when I close off the ram air and draw air from under the cowling.
Turbo's are a small fast turning fan and we all know a big slow turning fan moves more air so maybe a 12 inch squirrel cage turning 2700 rpm might move enough air to make a difference?

[Sawdust]

Not quite the same thing, but....I read a story (with accompanying YouTube video) on a car forum about some guys who used four gas powered yard blowers to "supercharge" a little econobox car, and actually measured the resulting rear wheel power on a dyno. It really did measurably increase the power.

[eiclan]

just a quick reminder that horsepower costs,so driving a fan with the engine WILL incur a cost to the output.It is all about is the power in and out.This is why a turbo charger is more efficient than a supercharger as the supercharger uses engine power to drive it. Cheers Ross

[1600vw]

But nothing gives you that Hot Rod look better then a Supercharger...

https://www.youtube.com/watch?v=HRhDrt87ojY

[58boner]

Back in the 60's a dude named Smokey Yunick who also just happened to be a former B-17 Bomber pilot found himself to be a successful race car builder in the new burgeoning sport of NASCAR stock car racing. Having a dyno in his shop and an inquisitive mind he was known for his many...shall we say innovations that gave his cars an advantage on the track. He fashioned a supercharger that worked off of vanes he had welded to the spinning clutch assembly inside of the cars bell housing and recorded huge horsepower gains on the dyno but was unable to conceive a way to get the air to the air intake in such a manner that would elude detection of the tech inspectors. He did lots of stuff like that such as placing air pressure sensors in the wheel wells of test cars so he could collect actual data when he made changes to the wheel opening shapes on his race cars to reduce drag without visiting a wind tunnel.

[nrpetersen]

From basic physics, the name of the game with a fan type supercharger is how fast can you make the blades move. If you can get them to move 100 ft/sec say, then the maximum pressure gain per stage will be about 0.6 ft of water - or only about 0.25 psi (about 1/2 inch of mercury). At 2700 rpm your fan would have to be at least 8 inches in diameter (per stage) and you would be hard pressed to see the difference. But since the max pressure gain goes as the square of the velocity, the easiest thing to do is raise the RPM - a lot.

(I hope I did my estimates right........:confused:)

[58boner]

Ol' Smokey's model would have been an 11 inch clutch spinning in a bell housing say13 inches in diameter and he was looking for a gain around 7,000 RPM. That sounds like a pump that might move some air. He proved it on a dyno. the numbers went to the grave with him.

[nrpetersen]

Ol' Smokey's model would have been an 11 inch clutch spinning in a bell housing say13 inches in diameter and he was looking for a gain around 7,000 RPM. That sounds like a pump that might move some air. He proved it on a dyno. the numbers went to the grave with him.That could only be about 2 inches of Hg pressure gain - per stage.

[Cary]

The old Mooneys have a ram air valve, which when activated adds maybe 1 to 1 1/2" of manifold pressure--not a significant gain, but adds a little bit of power--and it's free.

Years ago, my pards and I were about to have our Skylane overhauled, and there was a manually operated turbo charger available at the time, from Rajay. It would have about doubled our overhaul costs, which was manageable, but our overhauler had a lot of misgivings, especially about the real possibility of pilot error causing massive over-boost and catastrophically destroying the engine. Ultimately we opted just to go with the overhaul, which was a wise move.

On the "there's no free lunch" side of the ledger, pretty typically maintenance costs increase with any kind of supercharging, largely because the extra stress that the engine incurs. TBOs are typically shorter, and few people have the fortune of going to TBO. For example, for a couple of years, I regularly flew a friend's Mooney 231, and one of the constant issues was red-lining the CHT, even at moderate power settings--it was necessary to run with the cowl flaps partially open at any higher altitude cruise. All that plumbing runs pretty hot.

Cary

[Skydriver]

( edit. . . ) This is why a turbo charger is more efficient than a supercharger as the supercharger uses engine power to drive it. Cheers Ross
A common misconception. It takes plenty of engine power to drive a turbo. Exhaust back pressure from the turbine restriction can easily be one atmosphere. 15psi back pressure on a 5" diameter piston is 294 lbs. of force pushing back on the piston. That is 145 HP at 2,600rpm. Yes, a centrifugal device is far more efficient than other designs but they all take gobs of HP to drive them. (numbers have rounding errors)

[1600vw]

Back in the 60's a dude named Smokey Yunick who also just happened to be a former B-17 Bomber pilot found himself to be a successful race car builder in the new burgeoning sport of NASCAR stock car racing. Having a dyno in his shop and an inquisitive mind he was known for his many...shall we say innovations that gave his cars an advantage on the track. He fashioned a supercharger that worked off of vanes he had welded to the spinning clutch assembly inside of the cars bell housing and recorded huge horsepower gains on the dyno but was unable to conceive a way to get the air to the air intake in such a manner that would elude detection of the tech inspectors. He did lots of stuff like that such as placing air pressure sensors in the wheel wells of test cars so he could collect actual data when he made changes to the wheel opening shapes on his race cars to reduce drag without visiting a wind tunnel.

As with anything if you want to do it right you better know what you are doing. So in building this truck I did a lot of research. Smokey did some great work with other parts of the engine like heads and intakes. I read a complete book just about him and what he did and did not do and why. Great reading.

Tony

[raytoews]

On closer examination the mechanism on the front of the engine on the Bally Bomber is an overuning clutch. It would need it because the props are fixed pitch and an engine failure would produce bag of drag so the prop has to windmill freely, thus the need for the clutch.
Vey clever.
I owned a Terra Terratorn for a while and it had the same clutch. It worked fine but I removed it because we were concerned it would fail.

[Bob Dingley]

On closer examination the mechanism on the front of the engine on the Bally Bomber is an overuning clutch. It would need it because the props are fixed pitch and an engine failure would produce bag of drag so the prop has to windmill freely, thus the need for the clutch.
Vey clever.
I owned a Terra Terratorn for a while and it had the same clutch. It worked fine but I removed it because we were concerned it would fail.
I'm confused. I find that an unfeathered, wind-milling propeller produces high levels of drag. I had read that if you are unable to feather it, the next best solution was to stop the rotation by slowing to near stall or hope the engine seizes. I heard some trivia that in some instances a brake was installed to stop windmilling. Anybody else heard of brakes?


Bob

[raytoews]

A wind milling prop that is attached to an engine is now driving an air compressor, a free turning prop will create very little drag. On twin or multi engine airplanes freeing the prop or holding down the exhaust valve would have almost the same effect as feathering. IMHO
A windmilling prop or a standing prop makes very little difference in drag, glide at your best speed and depending on the condition of your engine will determine if it stops or keeps windmilling.

[1600vw]

I have practiced stalls just like everyone. We all know the feeling of what it feels like to pull the power to idle and do this. But I have lost a prop in flight and I can tell you she will glide a lot farther without a prop acting like a brake or maybe I should say the glide is different without the prop.

You are flying along and pull the power, the prop is breaking the aircraft down to a certain speed and kinda holding it there. You would have to experience loosing a prop to understand. Without the prop you do not have that sudden slowing of the aircraft. You coast so to speak. If you could unhook the prop from the engine the second you reduced the throttle you would kinda get this feeling. Its like putting a car in neutral instead of just letting up off the gas. You coast easier, farther, and harder to stop.

I never want to go through this again....NEVER.....

Tony

[Cary]

The difference between a windmilling prop and a standing prop is in fact significant. Very few find that out, either accidentally or purposely, but I've done both.


If you choose to do it on purpose, do it at a high enough altitude that you have plenty of time to start the engine again. In my case, in my younger and foolisher years some 40 years ago, I was well within gliding distance of the Laramie airport at approximately 12,000' in a 172. I pulled the mixture, and the prop continued to windmill. So I raised the nose so that the airplane slowed down, and at some point (don't recall the airspeed indication), the prop stopped. I glided for some distance, noting how noisy the wind and creaking of the airframe was, but also that maintaining airspeed took much less of a descent angle. How much less, I couldn't tell--very basic instruments in the 172 of a 6 pack, single navcom, and transponder--just very noticeable. To restart, I pushed the mixture in and tried pointing it downhill, but the air across the prop couldn't overcome the compression, so I gave it a touch of starter to start it windmilling, then let it run for a bit at idle to get it slowly warmed up again, before adding throttle.
I did it accidentally almost 10 years ago when my engine threw a rod at low altitude and the engine shook to a stop. The stopped prop added materially to normal 172 glide, which under the circumstances was pretty beneficial. Actually, that the engine stopped was pretty beneficial otherwise, too, because the violent shaking, had it continued, might have done some severe damage to the engine mount and airframe.


Like Tony, I never want that second experience again, and because I've grown much more conservative over the last 4 decades, I'm not about to try the first one again. I've reached the "old pilot" status, so I have no need to try the "bold pilot" method now.

Cary

[Bob Dingley]

Cary, your research backs up my info.


A friend who was an airshow performer in his J-3 85 always shut down number one during the performance. Data that he provided me was: prop would windmill down to near stall speed. Required an a/s of 100mph plus to re-start windmilling. Many times he stepped out on the wheel and hand propped it. You had to see it. He said a dead stick noticebly reduced his sink rate.


I confirmed some of this in my Champ over a frozen lake in Maine. Remained in the cockpit however. Enough said.


I would never dare to try any of this in a Baron or Beech-50/U-8. I knew military pilots that did. Radial blue line or Vmc is a barrier for me. Rate of climb much improved after feather. An instructor told me to consider a windmilling prop the same as a plywood disc of the same diameter. Was he wrong?


The Cessna "Bamboo bomber" WW2 trainer had fixed pitch wood props. I once saw a variant of the Aeronca Champ with two engines and fixed props. These must have been real "pigs" on one engine.


Bob

[Greg Wilson]

Bob, The " Aeronca Champ with two engines " was likely an American Champion Lancer a twin version of the 7FC, quite an odd bird. They had a pair of O-200's and fixed props as you said. The one I was familiar with would sit down on the tail skid if you got in the back first and rock back onto the nose when the front seat was filled. It was to be an inexpensive twin trainer but found little favor as few were sold. I never flew in one but was told that it was good for training that you loose more than 1/2 the performance when an engine is lost,it would have a positive rate of descent with one shut down even when flown solo.

[crusty old aviator]

What is it you wish to do: get more power from your engine, thus overstressing it and shortening it's life, or just help it to breath better at altitude?

[Bil438]

It seems like a great idea to turbocharge an engine. A friend of mine has an Entrom chopper. IO-360 Lycoming rated at 240 hp. He does fly it extenively each summer.
However the Annual or 100 hour inspection sees most of the aircraft placed in an exact sequence but covering most of the hangar floor. The maintenance requirements are just brutal. It takes two mechanics the whole winter to complete the work. They might be putting in 10 or more real hours of work each for every hour flown. I work and build to fly. A Turbocharged engine means your hobby is building and maintaining.
At the very best Turbocharged engines go about one-half TBO and may be done at say 400 hours. Would you want to do that much extra work to fly a blown engine? Bill

[1600vw]

6-71 supercharger