DarZeelon

Brian,


HP is equal to torque (in Lb. -Ft.), times RPM, divided by 5252.1.
This, since 1 HP is equal to 33,000 lbs x Ft. per minute.

If you look at HP and torque graphs, shown on the same system of axes, they will always intersect at 5,252.1 RPM. This is the RPM at which the numerical value of torque and HP is identical

So HP is a linear function of both RPM and torque.

If torque is the same and RPM is doubled, HP is doubled as well.

If an engine gives half the torque at double the RPM, HP remains the same, and so on.


Most F1 pylon racing engines, MVVS GRRT/GRFT, Nelson, Jett, Profi, get their maximum performance between 28,000 and 35,000 RPM. There, they do get 3-3.6 HP.

If torque can be retained to 40K, HP would be around 4.1, I believe.

5.3 would to me seem not possible.
If I scale down the 4.1 HP to the .15 cid size, it would be 1.5375 HP. This I would consider the limit.

But since F1 engines must be run without a tuned-pipe, i.e. no boost and F2D engines have a tuned-pipe, the difference to 2 HP that you wrote about is made up.

Only if a full length pipe was allowed in F1 pylon and the engines were capable of and timed for 40,000 RPM, would these engines theoretically get to 5.3 HP...

Flyboy Dave

My Feedback: (21)

My OS .91 D/F engine could do that easily.

FBD.

downunder

And that's why I said HP is not scaleable because mechanical stresses (centrifugal forces, piston accelerations etc) increase at a far greater rate than the simply linear engine size. What should be understood about F2A engines though is that they're unlike any other engine because they're taken to the absolute limit and are terribly critical. It's because they're so critical that they can make that kind of HP. The 1.5HP you calculated for a .15 would make that a total beginner's engine but probably about right if it was only turning the 25K of that 4.1HP engine.

DarZeelon

Brian,


Still, about that 2.7 HP you stated for the winner... It is an overstatement...

The difference in that class, between champ and chump, is 10 RPM, not 0.7 HP...


...If 'chump' is getting 40,000; 'champ' would be doing 44,208 RPM, by your numbers...

downunder

*sigh*...I give up. You obviously know more than the guy who built the engine and set a world record.

jaka

Hi!
Dar......come on

Jan K

DarZeelon

Brian, Jan,


I call them as I see them.

Although I do like to argue a bit, the claim of 2.7 HP would to me seem exaggerated, unless it is backed with a realistic measurement.

I did come up to the claimed 2 HP, by adding the RPM advantage and the tuned-pipe boost of the smaller engines, over the .40 pylon engines, but the extra 35% has nowhere to come from.

These engines cannot have a VE that is larger than their competitors, nor do they have a 35% RPM advantage. I don't think there is any dynamometer that can handle over 40K RPM, or is small enough, to measure such an engine.
So to me it is only a claim, regardless of who the person who makes this claim this is.

If you can come up with the details that can corroborate the claim he is making, I may be more inclined to accepting this info.

That is over 1 HP per cc of displacement...

downunder

Then you'd better do some research on this and increase your knowledge data base. I know the correct search term so it only took a couple of minutes to find where using a dyno helped increase a Nova Rossi 21 from 2 HP to just over 3HP. Before that I found complete technical instructions on how to build your own for very little money. I'd read both of these some years ago so it's not like it's anything new.

DarZeelon

Brian,


I am not convinced!

Horsepower is not just a measurement, but a calculation of a force applied over a distance, per unit of time. Work output.


Going from 2 HP @ 40,000 RPM to 2.7 HP, requires any combination that would increase the torque and the RPM, by a combined 35%.
Since torque cannot be increased by very much (VE is maximized, as is pipe boost), it must mostly come from substantially increased RPM.

...And this is a problem, as RPM is a great strain on the moving parts.

I don't believe these claims and neither should you, Brian.


Even if torque graphs are shown, demonstrating an increase of 35% in torque from the same displacement, they are bogus.

There is no way, you could get better torque than from the most efficient pipe, without positive displacement supercharging.

DarZeelon

And Brian,


Using this 'identical prop load' example; this 10.5% increase in RPM, would still require over 22% increase in the torque, from an engine which is already close to being optimized, right out-of-the-box...

I refuse to believe this is possible, without a 'different' supercharging apparatus.

B.L.E.

I think that the main reason that pylon racing .40s are not tuned to be optimized at these rpms is not so much the mechanical limits of the engines but because of the exponential nature of prop load. At 44K, you would probably have to use a 1/2A size prop on a .40 and the reduced propulsion efficiency would likely cancel the gains of the extra power.
Big props turning low rpms tend to have higher propulsion efficiencys than tiny props at super high rpm, hence the popularity of gear reduction for electrics. With glow engines, the best prop is a tradeoff between engine power and propulsion efficiency.

downunder

I asked a speed flyer about this once and the answer I was given was that Pylon or marine or car engines operate under varying loads during a run so a pipe has to be able to give a certain amount of "grunt" lower in the rev range. Like a pylon model slowing slightly in hard turns and then having to accelerate back up again. Same deal with a boat that needs to do turns in a race.

A CL speed model isn't affected by any of this because as far as it's concerned it's flying in a straight line and only needs to be got up to top speed where it stays until the fuel is shut off. Because it's designed to run only at full speed the pipe can be made extremely critical.

Dar...I see you've picked up on what I said about stresses increasing at a rapid rate with revs and now you're using it as though you knew it all the time.
" ...And this is a problem, as RPM is a great strain on the moving parts."

NM2K

My Feedback: (14)

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I own several ST Blueheads. All of mine are ABC/ring with no baffle on the pistons. There are many variations out there in the world.

When the Bluehead gained its reputation in my neck of the woods, it was mostly used in the configuration that I own. I have never seen an ST Bluehead come stock from the factory with a baffled piston, although some folks claim that they have. I'll believe them. I have no reason not to, but none of mine are baffled piston engines.

While mine are not baffled piston engines, mine are not schneurle ported engines. This is where some of the confusion comes in, I suppose.

My Blueheads weigh very close to 20 ounces without a muffler or a header. By today's standards, that is really light for a .60. There are so many iterations of this engine that I would not consider my figures as being written in stone.

When hotrodding my Blueheads, I run 11x6 to 11x7 props and use an open front muffler (Mac's). Why? Because that is what came with the engines when I got them from a friend. He used to run them with tuned pipes and they howled pretty good. No, they were not as powerful as say an OS .61FSR or a Webra Speed .60, but the Bluehead was close.

If you already own either engine, I would use the one you own.

Sport_Pilot

Ed,
I have two Blue Heads, one with and one without the baffle. The one with will turn a 11-7 prop at about 12,000 RPM the one without will turn it at about 13,000. Don't remember which props or fuel. The one without the baffle is STS ported, the one with is without PDP which I think was also available on this engine. Both need an idle bar plug.

That ole Blue head came out in the early 70's and production stopped around the early 80's. At one time you could buy them in three flavors, plain loop ported, PDP, and ABC STS ported. Probably a few other changes in the decade or so they were made.