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HelicopterMain Discussion › Pulling into the power band
10-25-2009 03:52 AM  8 years agoPost 1
tarzan_eb

rrApprentice

Central Illinois USA

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I guess I don't understand. How if the 91 cspecs powerband is 15,000
can you run your engine at 14.400 to 14.600 can you be pulling into the powerband of the engine.Can anyone explain this to me?

Fly it ! Crash it ! Rebuild it ! Repeat as needed !! Everett

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10-25-2009 04:06 AM  8 years agoPost 2
tarzan_eb

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Central Illinois USA

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I would think

If the cspec powerband is at 15.000 you would need to run 15.500 to pull into the powerband is my thinking correct?
Why have I read to run it at 14.400 to 14.600

Fly it ! Crash it ! Rebuild it ! Repeat as needed !! Everett

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10-25-2009 05:15 AM  8 years agoPost 3
jjvwg

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Vail/Boulder, CO

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I have no experience with 90 engines (only 50's) but typically people run a headspeed that will put them a few hundred rpm above the max output rpms, that way if they bog, they bog down into that rpm range where max power is made.

Jeff

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10-25-2009 01:12 PM  8 years agoPost 4
tarzan_eb

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Central Illinois USA

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Can somebody straighten me out ? my brain is smokein

Thats what i thought. But I have read several things that have stated just the oppisite.
I even read on here that Curtis runs his cspec at 14,400. I also read it on Curtis youngblood site and don't understand it I guess because it doesn't make sense to me How you can even reach the powerband of 15,000 running 14,400.

Fly it ! Crash it ! Rebuild it ! Repeat as needed !! Everett

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10-25-2009 02:06 PM  8 years agoPost 5
GMPheli

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W. Bridgewater, MA USA

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So how do you know that the engine makes the most power at 15K?

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10-25-2009 02:34 PM  8 years agoPost 6
tarzan_eb

rrApprentice

Central Illinois USA

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Thats what I read

OS specs say 3,0 Hp at 15.000 rpm.I read several post that stated the same thing that 15.000 is the sweet spot the motor produces the most power.Thats why I don't understand why anyone would run under the the 15.000 suggested rpm. Can anybody chime in and clairify this any for me.Pleeeeease

Fly it ! Crash it ! Rebuild it ! Repeat as needed !! Everett

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10-25-2009 02:55 PM  8 years agoPost 7
nivlek

rrProfessor

Norfolk England

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Maximum torque occurs at lower rpm than maximum bhp .

At the end of the day , it gets dark .

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10-25-2009 03:08 PM  8 years agoPost 8
tarzan_eb

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Central Illinois USA

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How

How? if you are out of the powerband of engine.yes i would say if you are in the band but if you are on the front edge of it bogs any you are below where the engine makes the power. then you will have less torque than if you are above and bog into it.
mabey i'm not understanding. mabey its powerband is 14.000 to 15.000 on the 91cspec but i wiuld still think you would want to be on the high end of the band not the low end.

Fly it ! Crash it ! Rebuild it ! Repeat as needed !! Everett

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10-25-2009 03:30 PM  8 years agoPost 9
cudaboy_71

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sacramento, ca, u.s.

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here's a decent layman's read on how horsepower and torque relate to one another (and, why torque occurs at lower RPMs than peak HP).

http://www.autoshoppingcenter.com/RPM/Torques.html

if it ain't broke, break it.

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10-25-2009 03:44 PM  8 years agoPost 10
tarzan_eb

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Central Illinois USA

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I C said the blind man

Thanks that helps clear it up for me. cudos to cudaboy

Fly it ! Crash it ! Rebuild it ! Repeat as needed !! Everett

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10-25-2009 03:52 PM  8 years agoPost 11
nivlek

rrProfessor

Norfolk England

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Years ago , engine reviews in the model mags used to give bhp and torque curves , often with different nitromethane content fuel and different exhaust systems . I don't buy the magazines often now , but I haven't seen a review done like those for a long time .

At the end of the day , it gets dark .

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10-25-2009 10:26 PM  8 years agoPost 12
nitronoxious

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Laguna Niguel, CA

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You can set your headspeed such that your ENGINE spins around 1,000 to 500 RPM less than max power. Therefore, when you load the head you have some room "remaining" from peak power. At peak power the ports (air flow) and glow plug (timing) are no longer tuned for that range and therefore power falls off rapidly, much more so than running 500 RPM below peak power. I have tried it both ways on the .50 (2250 headspeed vs 2150) and setting the governor 500 to 1,000 under peak produced substantially more stable head speeds. More than one guy at my field put me onto this and I think they are right. With the head right at or above peak power, each time I marginally loaded the head RPM would rapidly decay.

What the manufacturer doesn't tell you is that power may be flat the last 1,000 RPM. They are just listing the maximum rated engine speed and peak power. Heli engines are designed to perform in a specific RPM range instead of across a powerband and therefore they are more finitely tuned in that peak range. Look at the peak power of an OS-50 Hyper vs. an airplane .50. I know, it's apples vs. oranges and they are designed to create power in two entirely different means (fixed RPM w/ variable pitch vs. variable RPM w/ fixed pitch)

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10-25-2009 10:32 PM  8 years agoPost 13
Richardmid1

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Leeds, England

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Imagine a car with a turbo approaching a hill at an engine rpm just below where the turbo kicks in, then you open the throttle on the hill the car will power up the hill. You could also go up the hill already in the turbo, both will get you up the hill with plenty of power.

Going above the power band just gives you more head speed unloaded but will drop off slightly through prolonged manuevers i.e. fast tick tocks.

Going slightly below the engines power band will give you a lower headspeed but a more consistant headspeed.

60% of the time, it works every time!

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10-26-2009 12:55 AM  8 years agoPost 14
Gearhead

rrMaster

Vt

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but Mufflers types come into play too !!

the best power I ever got from an OS 50 was from my old OS Silver Head 50 with a 60B carb and a Weston Mini Pipe burning 17% fuel (1 gallon Magnum 30 mixed with 2 gallons Magnum 12%),
I was turning a Head Speed around 2100 with a Gear Ratio of 9.065, that gave me an Engine RPM Speed around 19,000,, with 12 Degrees of Collective that engine would take the Throttle Stick as fast as I could pump it,,
YES with no Governor and 12 degrees of Collective I could hear the engine RPMs drop a bit as I pumped the throttle quickly, but I could also feel the engine pulling good and hard, yet at 11&1/2 Degrees of Collective the RPMs would not drop as I pumped the Throttle,,

that setup pulled harder from the bottom/and gave me more Top Speed than my Hyper 50 on 30% today with an MP2 with an 8.736 Gear Ratio at 11&1/2 Degrees of Collective,

no matter what HS you run these engines need to be loaded when the Throttle is Pumped, if your engine is not loaded it's like driving a truck down the road at full Throttle in First Gear "no acceleration",,
I have help more than a few guys having Tuning trouble with their smaller Glow Planes, their Plane Engine would not run correctly simply because they were turning to small a Prop with to small a Pitch, simply put their engines were not loaded,, once they went with more Pitch or a larger Diameter there Problems were gone instantly !!

http://www.allpar.com/eek/hp-vs-torque.htm

http://search.aol.com/aol/search?q=...e&s_it=spelling

Jim
Buzz Buzz Buzz

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HelicopterMain Discussion › Pulling into the power band
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