RPM are cool on youtube; Horsepower is cooler in the air

When engine can get good rpm's and runs steady flying becomes better. Small combat planes work best when they are flying fast. They are designed that way. The lil Satan is small for 1/2A combat plane but they do fly. Modern Russian imported wings are 250Sq. " wings if not bigger. Anyway Rusty sounds like you are hitting better performance. Best to you.
Dan

"The proof is in the pudding" or "where the rubber hits the road"

Yep, that's where it counts in the air! Glad your hard work payed off Rusty! Give yourself a pat on the back. Good Job!

Would love to see a vid of the l'il Satan in action with the new/old powerplant.

Rusty is right, higher compression, BMEP we call it here, brake,mean,effective pressure
gives more horse power at the same RPM. But at this point I am getting out of my
depth and need Puffie the young mechanical engineer who just introduced himself
to come in and explain it all to me.
I never tire of Rusty's adventures. John

Sounds like you had some good air and a perfect needle that day Rusty.

You get some thick air and it is a whole different machine.

PV Pilot wrote:Sounds like you had some good air and a perfect needle that day Rusty.

You get some thick air and it is a whole different machine.

Thick meaning dense, as in high barometric pressure on a cold day?

RknRusty wrote:

PV Pilot wrote:Sounds like you had some good air and a perfect needle that day Rusty.

You get some thick air and it is a whole different machine.

Thick meaning dense, as in high barometric pressure on a cold day?

Yes sir.

Just one thing to adfd.
Rusty you say when you point it up to loop the engine slows.
If the engine slows or cuts when you point it up that means it is too lean.

On a non pressure system you get that leanout when the tank gets low and you tip up and your needle is off a bit for the tank fuel level. Always tune for the bottom 1/2 of the tank.

It increases expotential when you are high compression and you have thick cold dense air. The air/fuel ratio tuning window also get really narrow. One of the reasons for a fine thread NV assembly.

Not really but richer it maybe 1/4 or 1/2 a turn and see if it still bogs down.

As soon as it leaps in the air,,you heard the pitch change,,as the tank ran out, it picked up even more.

Maybe just a touch lean for the bottom 1/2 of the tank.

It didnt pop the plug and it didnt surge,,so you are right there. Maybe a couple clicks richer next time.

You can afford to go a tick richer,, it's still going to pull good it would seem.

proctor wrote:Rusty is right, higher compression, BMEP we call it here, brake,mean,effective pressure
gives more horse power at the same RPM. But at this point I am getting out of my
depth and need Puffie the young mechanical engineer who just introduced himself
to come in and explain it all to me.
I never tire of Rusty's adventures. John

Sorry, this has been bugging me for a couple days now, I've always been inquisitive and I'm wondering if I'm missing something here...How can the same engine, at the same RPM, with the same load develop different amount of (HP) power? I'm sure the Black Widow with 1702 (hicomp) head is going to produce more HP, but isn't that because its going to turn a given, useful load at more RPM?

Yes, of course it is...
For a given prop (preferably a load calibrated one) the developed HP can be directly calculated from the obtained rpm.

The title of the thread seems misleading, but an engine may perform well on the bench while not delivering in terms of starting ease and a broad needle setting etc.

I also got a chuckle when I first read Rusty’s statement “Same RPM with higher horsepower makes a huge difference” because taken out of context, it could be technically challanged.
But I thought it was obvious that he meant “Same RPM (on the ground) with higher horsepower makes a huge difference (in the air).”
No contest.
Cheers,
al

Very Cool Rusty, one hot Bird that LIL Satan, looks like fun, back in 78/79 I built that same plane and originally put the a TEE DEE .049 on it using a 51/4 x 4 prop, that thing was so fast there wasn't enough elevator to get the plane to hardly stunt, big circles with gradual movement was all it would do at a million miles an hour, that's one time I was hoping it would run out of fuel quick, so I ended up doubling the size of the elevator but never did fly it again with the TEE DEE, bought a Black Widow for it, mounted it and its still hanging in my gargage today, never flown again, Maybe I should give it a whirl again, but at 51 I think it's time for RC planes?

Thanks for the cool post luv'd it, keep fly'n

RknRusty wrote:
Thick meaning dense, as in high barometric pressure on a cold day?

Hmmm, sorry. Dense (cool, moist) most definitely doesn't mean "high barometric pressure". The two are mutually exclusive.

I take dense to mean more molecules of air gasses per cubic inch(or your preferred volumetric measurement). Air is more compressed at high pressure than low pressure, meaning a higher density of available combustion gasses, mainly oxygen. And cold air has more molecules per square inch. The molecules of any substance are more dense when cold. Everything from air to steel expands with heat, and contracts in the absence of heat.

I guess my title was confusing. I'll try to address that later, I'm on the run now.

proctor wrote:Rusty is right, higher compression, BMEP we call it here, brake,mean,effective pressure
gives more horse power at the same RPM. But at this point I am getting out of my
depth and need Puffie the young mechanical engineer who just introduced himself
to come in and explain it all to me.
I never tire of Rusty's adventures. John

What I was trying to say was that the indicated horse power = PLAN/33,000
Where P= pressure or bmep, L = stroke, A = area of cyl bore, and N = RPM
So that increasing any one of the variables will increase the power, in Rusty's
case increasing P.
John

I was referring to my un-scientific observation in the field, using only my ears as a tach. I had run this engine with a standard head and it performed as seen in the video I posted earlier in this thread, slowing a lot when under the load of a climb and speeding up in a dive. Later I added compression with a new head and plug insert. I added shims, so it only had a little more compression than the regular head, and there was no noticeable increase in RPM during flat laps. Like I said, I did not use a tach, but I'm pretty sure it ran at about the same speed. When I flew it through my usual routine of loops and 8s, it powered through without slowing. It obviously had more power because the resistance of the air did not affect the prop speed as it does with the stock head. I have a video of it from the day before I started the mouse racer rebuild.

Same plane and engine with high compression head.
Forward to 3:15 and listen. It's only one loop pasted several times because the camera quit recording the flight.


In this second movie, it powers through the whole loop with no drop in engine speed. Compare the sound of this to the first video. In that one, it only peaks when I'm doing flat laps. I only flatten out a couple of times, so you have to watch and listen until I level off long enough for it to rev all the way up. Maybe my ear is cheating me. Even if the high compression head is peaking a little faster, it still has zero bog as compared to the first. A huge difference in power with little difference in RPM.

Can you calculate power from RPM, as was suggested? What if I screw a prop to my Chevy flywheel and spin it up to 9 grand. Same prop on my .049 and throttle it down to 9 grand... which one would you rather stick your finger in.

If I'm all wrong about this, at least we had something worth thinking about.


EDIT: Aw hell, I can't tell. Maybe it was a little faster with the new head.

Hello Rusty,

What are you running for fuel, All I can find around here, is1 Litre container 30% Nitro Heli Fuel which I got from Great Hobbies, then dropped 100ml Castor Oil in it

Jobe_Pro wrote:Hello Rusty,

What are you running for fuel, All I can find around here, is1 Litre container 30% Nitro Heli Fuel which I got from Great Hobbies, then dropped 100ml Castor Oil in it

For my Reed valve engines, I use GlowPlugBoy Rocket 24 All Castor: http://www.gcbmrc.com/GlowPlugBoy_prices.htm
He takes PayPal and has an eBay store too. $10 per quart and $10 shipping. I add 1.3oz of Rexall castor oil to bring it up to 20% oil. I buy castor oil at Dollar General in 2oz bottles. My engines run smoother on this than any other fuel I have tried.

For my higher speed Tee Dees and Medallions, I use SIGCF016, SIG CHAMPION FUEL 25%, $8.39/qt. or SIGCF007, SIG CHAMPION FUEL 35%, $9.99/qt. It has 10% castor and 10% synthetic. It makes a slippery mess, but I think it lubricates extremely well.
Go to sigmfg.com and click on Field Equipment>Fuel>Fuel-Airplane, then click on the picture for the list.
Both vendors sell gallons too.

RknRusty wrote:

Jobe_Pro wrote:Hello Rusty,

What are you running for fuel, All I can find around here, is1 Litre container 30% Nitro Heli Fuel which I got from Great Hobbies, then dropped 100ml Castor Oil in it

For my Reed valve engines, I use GlowPlugBoy Rocket 24 All Castor: http://www.gcbmrc.com/GlowPlugBoy_prices.htm
He takes PayPal and has an eBay store too. $10 per quart and $10 shipping. I add 1.3oz of Rexall castor oil to bring it up to 20% oil. I buy castor oil at Dollar General in 2oz bottles. My engines run smoother on this than any other fuel I have tried.

For my higher speed Tee Dees and Medallions, I use SIGCF016, SIG CHAMPION FUEL 25%, $8.39/qt. or SIGCF007, SIG CHAMPION FUEL 35%, $9.99/qt. It has 10% castor and 10% synthetic. It makes a slippery mess, but I think it lubricates extremely well.
Go to sigmfg.com and click on Field Equipment>Fuel>Fuel-Airplane, then click on the picture for the list.
Both vendors sell gallons too.

I went to the SIG site a week ago and they too wanted an asinine amount for shipping. Nobody carries 1/2A fuel around here I am tempted to buy some heli fuel or some high nitro content fuel and add Castor like yourself.

I wanted to snatch up some GPB fuel but, refuse to pay the same for shipping as for the price of the fuel. And they are only like 2hrs away from me in Texas!

cribbs74 wrote:I wanted to snatch up some GPB fuel but, refuse to pay the same for shipping as for the price of the fuel. And they are only like 2hrs away from me in Texas!

Buy 2 quarts, the shipping is still $10 bucks.