# Rear Bear Vs. The Russian Bear

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#### pie_row

##### Well-Known Member
If $is a concern for you then your project is never going to get off the ground, literally. Just on your basic assumptions, your engine will need to run consitantly in the 9,000-10,000k RPM range consistantly to maintian proper propeller effieciency. Your talking abount full complete overhauls every hour of flight time. Its not a practical vision by any means but if you have$ to burn by all means. I suppose you would need at lease \$2 million to burn on this to get a prototype in the air. And a considerable amount more to keep it going.....
I looked for the auction that sold TAG Porsche engines didn't find it. (It is listed in a prior page on this thread.) They were selling used engines that had won 4 and 5 races. Modern F1 engines are required to be used for 2 races. Porsche entered into the F1 turbo engine building business from an endurance racing background. They built 50 hr engines at 950 hp from 1.5L. They weren't built to cool that much power continuously but mechanically they made that much power for 50hrs before needing to be rebuilt. At a power density of 666hp/L it should be possible to make a 50hr TBO engine that is aircraft rated. That would be uprating the Tag Porsche for continuous output. It may be possible to build a 50hr air race engine that is rated at 1,000hp/L. That is my design point. Keeping the average piston speed down is critical for long engine life. That means a short stroke. Cooling and knock dictates a small bore. Getting enough bearing area into a small enough package dictates a two crankshaft arrangement. So the layout that I'm looking at is a twin V-16 42.5mm bore and 33mm stroke. At the average piston speed that NASCAR and F1 use it would make insane amounts of power. 2,100 hp for the twin engine combo. 1,400hp/L back it off to 1,400hp for both crankshafts together and should last a lot longer than at 2,100hp.

This calc shows the engine The calc has two self compensating math errors I haven't gone back and fixed them yet. But it does work.​
As far as the money goes ya it wouldn't be cheap but it would be fun and I mean fun.​

##### Well-Known Member
They weren't built to cool that much power continuously but mechanically they made that much power for 50hrs before needing to be rebuilt.
Well, lubrication, bearing heating, vibrations wear and mechanical wear also rises a bit more than linearly with rising RPM's...

#### pie_row

##### Well-Known Member
Well, lubrication, bearing heating, vibrations wear and mechanical wear also rises a bit more than linearly with rising RPM's...
Very true,

You need to reduce the bearing diameter to keep the rubbing velocity down. Mechanical wear is a function of the rubbing velocity as well as the pressure applied. So smaller pistons help with that....

#### macdonca

##### Active Member
I looked for the auction that sold TAG Porsche engines didn't find it. (It is listed in a prior page on this thread.)
I can show you auctions where complete R-3350's are selling for 5k. A running 3350 + homebuilt air racer is still going to cost 2-5 mils + upkeep.

Modern F1 engines are required to be used for 2 races.
An F1 race is only a little over an hour long.

Porsche entered into the F1 turbo engine building business from an endurance racing background. They built 50 hr engines at 950 hp from 1.5L. They weren't built to cool that much power continuously but mechanically they made that much power for 50hrs before needing to be rebuilt. At a power density of 666hp/L it should be possible to make a 50hr TBO engine that is aircraft rated. That would be uprating the Tag Porsche for continuous output. It may be possible to build a 50hr air race engine that is rated at 1,000hp/L. That is my design point. Keeping the average piston speed down is critical for long engine life. That means a short stroke. Cooling and knock dictates a small bore. Getting enough bearing area into a small enough package dictates a two crankshaft arrangement. So the layout that I'm looking at is a twin V-16 42.5mm bore and 33mm stroke. At the average piston speed that NASCAR and F1 use it would make insane amounts of power. 2,100 hp for the twin engine combo. 1,400hp/L back it off to 1,400hp for both crankshafts together and should last a lot longer than at 2,100hp.
Doubt it. The Pond Racers motors were seriously de-tuned and they still came apart. Remember, if it was that easy somebody would have done it already.
This calc shows the engine The calc has two self compensating math errors I haven't gone back and fixed them yet. But it does work.

I am an engineer by trade. Just because math calculations work on paper, does not mean they are practical or will work in "real life"
As far as the money goes ya it wouldn't be cheap but it would be fun and I mean fun.
I can think of a lot more fun ways to burn 5 million dollars. Why dont you just buy a T-6 and go racing? You can probably get the plane and all the required flight training for under 150k. Save yourself a couple of million and 10 to 20 years of frustration.

#### macdonca

##### Active Member
Too true, But the Tag Porsche engines as far as I am aware were used for practice qualifying and racing. Times 5 races that is pushing the number of hrs that they were run up there a bit and they never broke an F1 engine in competition. 100% reliable. They could have pushed the engine much harder if they were willing to brake them in races.
Is your 1-off PSRU that your going to have to machine yourself going to be as reliable as the motor?

#### macdonca

##### Active Member
You are very correct. How ever if you understand why the math works or doesn't then you may be able to make something work.
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And this is why your math does't work.

Your engine requires 14.5 grams of fuel per rev accourding to your model.

at 10k rpms thats 145,000 grams of fuel per minute

8,700,000 grams of fuel per hour. or 19180.2 lbs per hour

at 6 lbs per gal thats over 3,000 gal of fuel for an hour of consistant 10k RPM operation. Sounds thirsty.

All of your power to wieght quotes are flawed because they dont dont take into effect the PSRU, Radiator and Cooling equipment, and all that extra fuel you have to carry. At the end of the day, you are worse off than the tried and true equipment thats already in use.

#### macdonca

##### Active Member
Power to weight ratio is important. But for low transonic drag low cross sectional area is also important. Figure the fuel at 0.5lbs/hp. hr. 1,400hp= 700lbs/hp. hr.=116 2/3 gl/hr. Call it 60gl for a 30min at full power endurance (That matches the endurance of the Pond racer) flight.
ok we'll call it 120 gal/hr. And we'll assume your using 60 gal on board.

so were at 360 lbs in fuel

The picture of the lathe below shows one way to build a re-drive. A set of micro V belt pulleys between two bearings each. This looks to be the lightest way of transmitting the power.

WHAT?

The radiator would be sized for about 50% power with the excess cooling taken care of by water spray. The inter cooler and after cooler would be water spray cooled as well. I've got a 98% effective and very close to zero pressure loss inter cooler that is also small and light. Water needed would be about 200lbs for 30 min at full power half that for 15 min at full power with the rest of the time at 50% power or less.
25 gals of water or 200 lbs total liquid on board 85 gallons.

Where are you going to fit 85 gallons in a homebuilt the size of an AR-5? Regardless, the weight of your fuel and water (your figures) weigh more than the entire AR-5 did. All this weight pulled by a belt and pulley PSRU?

#### JimCovington

##### Well-Known Member
Where are you going to fit 85 gallons in a homebuilt the size of an AR-5? Regardless, the weight of your fuel and water (your figures) weigh more than the entire AR-5 did. All this weight pulled by a belt and pulley PSRU?
I'm pretty sure we've jumped the shark...err, I mean changed topic...once again, so the plane with the 1400hp engine is NOT the size of the AR-5.

And of course the belt+pulley arrangement will hold up to the stress - didya see the size of that lathe frame? :roll:

#### macdonca

##### Active Member
I'm pretty sure we've jumped the shark...err, I mean changed topic...once again, so the plane with the 1400hp engine is NOT the size of the AR-5.

And of course the belt+pulley arrangement will hold up to the stress - didya see the size of that lathe frame? :roll:
Yeah... Time to put this thread to bed. Its more comical then technical.