>> G'day Paul
>> I flew my RV7 Rensis for the first time today. All went well,
except
>> for
>> the heat radiating from the Tangential Muffler, more shielding
coming
>> up.
>> A question for the Propeller people.
>> Static full power run gives 5900 rpm with no cowls on and the
68"X86">> Prince P tip prop. However the max I can on take off is
5200 rpm.
>> Does this mean the prop. is stalled when static? Does a stalled
prop.>> spin faster than an unstalled one?
>> The other possibility is that the [carb] air intake under the
cowl
>> is
>> drawing in very hot air.
>>
>> Ian Beadle Western Australia.
>>
>> Great news Ian. Congratulations. You built that thing in
>> record time. My guess is.. it being your second rotary powered
>> RV really helped. I'll see if Robin and I can get over there
>> in the next year or two and go for another ride. Are you still
>> at the same airport and hangar?
>>
>> Don ought to hire you to help finish his Mustang II.
>> You now qualify as an expert rotary engine installer.
>>
>>
>> Well it depends on your definition of stalled.
>> I have heard of that condition before. Typically people refer
>> to that condition as the prop starting to "bite" when the airplane
>> starts moving. Do you have the 2.85:1 or the 2.17:1 gear ratio?
>>
>> Please send me some more pictures of your cowl opening and rad
>> configuration and I will try to figure out what is going one.
>>
>> In the mean time here are some old pictures of Ian's first airplane
>> and hanger for the realatively new guys.
>>
>> The last picture is Ian's new TB and intake air filter.
>> My guess is the intake runners are too short for 5900 RPM.
>> They need to be 22 to 24 inches long or there abouts for a
>> 2.17 gear box. Shorter for a 2.85:1 gear box. 18 inches or so.
>>
>> A 180 degree cold air ram air scoop coming up and out
>> of the top of the cowling will help. See the 3D. The last
>> thing you should change is the prop pitch.
>>
>> Paul Lamar ...No rotor no motor.
>>
>> The Rotary Engine NewsLetter. Powered by Linux.
>>
>
> Paul,
>
> I'm also building a similar type of intake manifold for my
Renesis, as
> previously posted. Target rpms are currently 6500 with the 2.17
drive> (and a short, 65" prop). This is prop rpm of 3,000, and a
tip speed of
> .74 mach (580 mph). This is fast, but is still a lot slower than
Warp
> Drive's recommended rpm for this size prop.
>
> You had mentioned before that a short intake manifold wouldn't
make any
> real difference in this rpm range on a Renesis. Should I not be
> pursing this type of intake manifold?
>
> Scott Gettings
>
> I don't recall saying a real difference at 6500 RPM. I was assuming
> 7500 RPM because you had an RX8 engine. I was also assuming bell
> mouths inside the short runners. Maybe I missed the fact you had
> a 2.17:1 GB.
>
>
> If I were all you guys I would forget the silly side ports.
> That goes double for Mistral that are casting their own side
> and rotor housings. It is much MUCH easier to cast end
> and center housings with out side ports. They would have a
> lot easier time selling their engines if they had 240 HP
> or more on the 2 rotor and 360 HP on the 3 rotor normally
> aspirated. Current ratings are 190 HP and 285 or so.
> Their intake manifolds would be cheaper to make
> in the bargain.
>
> Everette Hatch built P-port engines 20 years ago and Allan
> Tolle went 238 MPH in the Sun 100 race. We built a p-port engine
> and got 240 HP on the dyno at 6500 RPM with a carb no less. How
> much more evidence do you need?
>
> In your case Scott the 65 inch prop will help but I don't
> think you are going to see 3000 prop RPM.
>
> --
> Paul Lamar ...No rotor no motor.
>
>
Thanks, Paul. I can go up to 7500 rpm if necessary, but this would
give 3456 prop rpm -- very fast, but still lower than the recommended
3700 rpm for this short of a prop --- according to Warp Drive. In
worst case, I can always switch out the redrive to a low-ratio
version.
I have bellmouths inside the plenum, ported into the 1/4" base plate.
They have a minimum of 1/4" radius, as per your previous
recommendations.
Scott Gettings
Somebody is pulling your leg. A 65 inch dia. prop is not going to
go 3700 RPM.
I think you can still add longer runners. Here is a better 3D of what
I am talking about. You need a longer prop anyway to get the low speed
thrust you will need to get on the step and out of the water.
I would change the drive to 2.85:1 and add longer runners.
--
Paul Lamar ...No rotor no motor.
Thanks for the suggestions, Paul. My prop is limited to 65" because of
the aircraft structure. I would have to raise the engine above its
already-high CG to get a longer prop.
Regarding the intake my engine is already built by Bruce T., so it is a
little late to go to peripheral ports at this time. The cowling will
have to be a lot larger if longer vertical runners are used as per your
drawing, because of space restrictions in this area. They might work
going out the side using a totally custom manifold, because I have more
space in width than vertical. Or I can go back to long, over-the top
runners, but I see you don't like this because of the drag. Or I could
let the plenum chamber/intake reside outside the cowling.
Scott Gettings
Well going out the side would be an improvement.
One, the tubes would be straight and two, you could
use one larger tube for each end housing instead of two
for a total of four runners instead of six.
I can send you a pattern for a sheet metal transition
for the two RX8 ports in each end housing to round tubing.
The transitions can be longer than shown in this 3D for
a smoother conversion.
You can still do a little die grinding that area without getting
the powder in the engine. The ram air intake could then be out
side the cowling. You might even think of a slide throttle
for a little extra HP.
The largest improvement would be a 2.85:1 G.B.
What modifications did Bruce make?
Paul Lamar ...No rotor no motor.
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