650 HP Rotary Time To Climb record attempt

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BJC

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With 650 HP, a decent propeller, and 1,200 lbs. gross weight, it should be capable of vertical flight at lower altitudes.


BJC
 

Will Aldridge

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I must also say I have been unceremoniously kicked-off Paul's site, but for the life of me I'm not sure why. Needless to say there are many who have suffered the same fate who wear it as a badge of honour - personally it doesn't worry me one way or another, but I still have many good friends from that period, some still on there for any possible developments/revelations.
I can say however as far as Aviation developments of the engine (for general Aviation use), my contacts seem to be well ahead of Paul attempts - but I wish him well for the record attempt.
I posted once disagreeing with something in his "How to Cool your Wankel book" and he never posted it just sent me a private email telling me I was wrong. I think he's a little overly proud of that book and thinks it's the only way to cool an engine. And of course he believes that the Wankel is the embodiment of mechanical perfection, and nothing can be said against it. There was one guy from a car magazine I think that had done a head to head test of an RX8 against a BMW and was citing all the figures about fuel efficiency he had from the test and Paul didn't have anything real to say against it he just kept telling the guy he was wrong. I had the mental picture of a little kid plugging his ears and shaking his head, yelling "nope, nope, nope".

Here is Peter Garrisons comments cut and pasted from his site:

The oddest thing about the airplane is that it has no cowling. The engine, with all of its plumbing, air and oil radiators and general clutter is left out in the breeze. The reasoning is that at 90 kias parasite drag will be a minor factor. Actually, this is not quite true; at best rate of climb speed, which is bound to be close to the best L/D speed, parasite drag is half the total drag. At any rate, I did some calculations, making various unfounded assumptions about the drag contribution of the engine, and found an impact of several hundred feet a minute. I did take into account the fact that a cowling would add weight at the same time as it reduced drag. The cooling drag, of course, would still be there.
Paul has been gushing about how effective the radiator is (it's 2 dodge truck rads combined in a cross counter flow arrangement) to the point that they might not need the spraybar water. Although I give him credit for the fact that it's doing well I've never seen one of his renderings of a rotary engine setup that allows any air to actually circulate around the engine, and if there were some, then that air had been preheated by a trip through a heat exchanger before it got to the engine block itself, and wouldn't be able to carry much heat away. His drawings usually show a duct running from the intake to the exchanger and the exchanger being vented directly out the side of the cowl.

Our own late great Orion said it was just about mandatory to have some air passing over the engine block. I'd bet a fair chunk of money that if you covered that engine in a cowling it would start running a lot hotter. In my own design I'm looking at the engine block as it's own heat exchanger and providing unheated air to flow around it, and directing a fair amount around the exhaust system as well. Right now both of those very hot objects are hanging out in the breeze and I'm sure that's contributing significantly to their better than expected cooling.

The way I see it, if the anticipated climb rate is 12,000 fpm, then he should calculate the parasitic drag at a speed higher than 90 kts because 12,000 fpm nearly 120 kts by itself. If the climb is anything less than vertical, the total airspeed will be even higher.
I don't have the emails any more but I'm pretty sure Paul said something about doing 120 kts straight up.

With 650 HP, a decent propeller, and 1,200 lbs. gross weight, it should be capable of vertical flight at lower altitudes.


BJC
Paul said something to that effect since I've been aware of the project and repeated it in the latest set of emails after the crow hops.
 

rv6ejguy

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Paul pretty much can't take anyone disagreeing with his way of doing things even after they show him in real life that their solution works just fine. I recall the "plugs up" controversy something like 15 years ago, anyone using anything other than a wedge diffuser on a rad was an idiot and so on. Even after overwhelmed with facts to the contrary, Paul would still insist he knew best, yet for years, he had almost zero practical experience or testing facts to back up his position on various subjects.

With more rad volume than a 1600hp Spitfire, he's doing nothing impressive with cooling 650hp here either. It's another inefficient, high drag solution but in this application, that may not matter.

No clearance air inside an aircraft cowling is a sure way to shorten the life of various components from alternators to exhaust systems to PSRUs.

In any case, this is an exciting project. Always nice to see anyone building something different to shatter the existing records. Will be very interested to see the results.
 

Will Aldridge

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The plane is now in at the location that they'll be attempting the record flights and they are working through their flight test program working up to full power.

With more rad volume than a 1600hp Spitfire, he's doing nothing impressive with cooling 650hp here either. It's another inefficient, high drag solution but in this application, that may not matter.
I've tried a few internet searches to find radiator areas on either the spitfire or the mustang since they both had the Merlin, could you supply a link to that info? I'm kinda interested in putting that in the discussion about the radiator since the topic keeps coming up and would like hard data before i do.
 
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Will Aldridge

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Apparently we were looking at the wrong dodge truck radiators. The ones he is using are 20 x 30 x .75 inches giving a total volume of 900 cu inches. Doing a little math here the Merlin 66 put out 1720 hp so that's .81 cu in of radiator capacity/ hp (assuming your 1400 cu in estimation is correct) and .72 cu in rad/ hp on the TTC project.

Mr Lamar was quite quick to point out neither the Mustang or the Spitfire would cool on the ground.
 

rv6ejguy

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I wrongly assumed from the photos you posted that the rad was the full thickness of the front tank (looked to be 3 to 3.5 inches thick).

I think it's too soon to tell if Paul's setup will cool as well as as a Spitfire until he flies it at the same altitudes at high power and encloses the engine inside a cowling. Secondly, the hp claims on this rotary are only estimates.

The Griffon Spitfires cooled very well on the ground actually (not the Merlin ones though as you say). The Griffon ones had deeper rads but also had over 2000hp.

The big difference in rad ducts like the Spitfire and Mustang have is that they produce far lower drag than Paul's setup in the cruise configuration due to the straight through design and the variable geometry exit doors. The momentum loss must be very high with the direction change and inlet/ outlet geometry ratios in Paul's setup.

As I've said many times before, cooling is easy, cooling with low drag is more challenging.

Sounds like the record attempts may be close at hand, will be interesting to see the results.
 

Vigilant1

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Doing a little math here the Merlin 66 put out 1720 hp so that's .81 cu in of radiator capacity/ hp (assuming your 1400 cu in estimation is correct) and .72 cu in rad/ hp on the TTC project.
That's something to think about. Imagine if you'd built a little 3 HP 4-stroke water-cooled engine. You'd taken steps to assure very little air cooling occurred at the cylinder head and block, but you had only a tiny water radiator of less than 3 cu inch volume (about 2/3 the volume of a deck of cards), and an even smaller radiator for the engine oil. It's amazing that there's enough surface area in there to provide the needed heat exchange for a 3HP engine running at full capacity. It would seem more plausible if the heat exchanger was 1mm thick and the LxW of a sheet of paper, but that's not the packing ratio used by the "big boys."
 

Will Aldridge

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A similar thought went through my head. If I use that ratio for 250 hp and use 2 rads in a cross counter flow arrangement like the TTC then I'd only need 2 8.25" x 8.25" x 1" thick rads. Instead of having them parallel with the airflow mounted under the engine like the TTC I could mount them perp to the airflow and not have the momentum loss Ross mentions. However as he mentioned we're assuming the TTC is actually 650 hp, and that the efficiency is a linear function. As you mention I doubt such a small rad for the 30 hp engine would work.
 

WonderousMountain

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I'm still subscribed to the rotary newsletter, but I block their messages. Best of both worlds :gig: I wish he would have gone with a three rotar, but such as it is I think they'll get a good attempt in. All aluminium is a good setup. Cooling is a big aspect of quality engines.
 

rv6ejguy

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We commonly use 1 cubic inch of rad volume per hp when sizing for aircraft with Vy speeds of at least 80 knots. Of course there are other factors here- core depth, pressure recovery ratio of the duct, Delta P, type of coolant used, core construction, ground cooling, average ambient temps, power at altitude etc.

There have been successful Experimentals using core volumes below .6 cubic inches per hp however this is not something you want to build over if cooling is inadequate. If you use an exit door, you can easily cut rad mass flow and drag in cruise while still having good climb cooling.

All WW2 aircraft had movable rad exit doors. Closing these resulted in speed increases of up to 30mph in level flight.
 

Will Aldridge

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Well they nearly burned the plane up along with the pilot. I guess a mechanic didn't reinstall a piece of safety wire on one of the injectors and it came loose and sprayed fuel on the engine. Given the lack of talk about damage I'm guessing they caught it pretty quick and damage is minimal. But Paul is talking about what a crappy job racing beat did of setting up the system and it sounds like maybe he'll be building a new fuel rail for it.
 

wsimpso1

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I'm not sure why a Bell 47 gearbox (280hp) would be so overbuilt to be able to handle 1000hp but it might handle 650hp for the few minutes needed here.
Ross has a really good point. Gearboxes are designed around torque and speed. I doubt the capable folks at Bell came up with a box grossly overbuilt for their engine just in case someone would want to do something hugely different 70 years later.

A couple ways this could be done, but I am pretty sure it would have questionable durability... Starting point is the Bell 47 gear box is a two stage 9:1. Engine was 260 hp at 3100 rpm, or about 440 ft-lb. 9:1 with 440 ft-lb and 7800 rpm would mean a 867 rpm at the prop. That would force a prop on the order of 105" diameter. So the power and prop might work. Trouble is, the box was originally designed for 3100 rpm input speed and 344 rpm output speed, and this would ask it run with 7800 rpm in and 867 rpm out. That is a lot of speed upgrade to find in the bearings and gears, and it has to do that after they find a suitable 105" prop...

Another way is they only use the second stage, which is capable of carrying that 440 ft-lbs times the gear reduction ratio of the first stage. If the first stage is 4.5:1, the input to the second stage would be around 2000 ft-lbs, but at 689 rpm. This fire-breathing 13B will be at 6000 to maybe 9000 rpm. Make parts designed for 689 rpm run at 10 or more times that? Good luck with that.

Now maybe they actually did get with some really good gearset and bearing guys, and upgraded the bearings and lube spray and other stuff to allow those rpms. We shall see if it was enough.

I am with Ross, skeptical.

Billski
 

wsimpso1

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Revising numbers 650 Hp at 8000 rpm and a 3.0:1 ratio gearbox. Yeah, they must be using only one stage. 650 hp at 8000 rpm is 427 ft-lb, they could use the first stage but they are still running 2.5 times faster than the thing was designed for. Hope they knew how to upgrade the pieces to run that fast.

Billski
 

rv6ejguy

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Well they nearly burned the plane up along with the pilot. I guess a mechanic didn't reinstall a piece of safety wire on one of the injectors and it came loose and sprayed fuel on the engine. Given the lack of talk about damage I'm guessing they caught it pretty quick and damage is minimal. But Paul is talking about what a crappy job racing beat did of setting up the system and it sounds like maybe he'll be building a new fuel rail for it.
Glad they are still in one piece.

Not sure what setup they have for mounting injectors but we never rely on safety wire to hold any of it together. First, the used turbo which was previously damaged, now this, blaming it on Racing Beat. They are the ones screwing this all together and Paul is an engineer. If something doesn't look sound, you change it before you fly and everything needs to be inspected before it goes on the plane, especially used turbos, fuel system components etc.

Hope they have some other experienced eyes go over the whole airplane before flying again. Fires are as scary as it gets.
 
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