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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › Running my 91HZ-R a few hundred rpms over, will it hurt motor
09-08-2013 01:34 AM  4 years agoPost 1
shinysideUP

rrApprentice

USA NJ, NY

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I wanted to up my head speed 50-100 more, I am currently at 16k on the engine.
Will going to 16,400rpm or 16,800 have adverse effect on the motor, running on 15% with .1mm/004" shim?

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09-08-2013 06:33 AM  4 years agoPost 2
McKrackin

rrProfessor

Lucasville,Ohio

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What head speed is that?

16,000 RPM is close to leaving the power band on the upper side.
You lose power at lower RPM but you also lose power at higher RPM.

15,500 is a nice target speed.

Look into different gearing for higher head speed but really,2000 RPM on the head is about right.

I run 1950 RPM with my OS105.

I literally never use the word literally right.

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09-08-2013 06:49 AM  4 years agoPost 3
shinysideUP

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USA NJ, NY

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I'm geared at 8.0:1, 16000 max on engine from OS,
With 2000HS govd. I am at engine max, I believe it drops back into the peek power band during SOME 3D maneuvers. Want to raise HS to 2050-2100 to keep momentum of drive train a little longer and also make the heli faster.
I have a friend that has the same motor on simlar heli same FBL Gov. but his ratio is 8.2, running 2150HS on ID 2 with 15%. Tic Tocking like beast, havent heard of him having trouble yet.

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09-08-2013 07:35 AM  4 years agoPost 4
McKrackin

rrProfessor

Lucasville,Ohio

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8.2 is a lower gear ratio than 8.1...Just in case you didn't realize it.

The ratio means the rotor head turns one revolution for every 8.1 or 8.2 turns of the motor.

Your buddy is revving higher than you.

More than I would but hey...lol....if it works.

I literally never use the word literally right.

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09-08-2013 03:44 PM  4 years agoPost 5
Zaneman007

rrElite Veteran

Texas - USA

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Deleted

Old Guys Rule!

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10-25-2013 10:07 AM  4 years agoPost 6
shinysideUP

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USA NJ, NY

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can I run my 91HZ-R at 17000rpm without blowing it up?

Fly hard, fly low, fly till she leaves and never comes back.

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10-25-2013 04:38 PM  4 years agoPost 7
McKrackin

rrProfessor

Lucasville,Ohio

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I doubt it.
17,000 RPM spikes might not kill it but any long runs would.

They are meant to run 15,500 and 16,000 is supposed to be the upper limit of normal use.

I literally never use the word literally right.

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10-25-2013 07:17 PM  4 years agoPost 8
ticedoff8

rrKey Veteran

Morgan Hill, CA. USA

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Stock Numbers:
OSMG1981
OSMG1982 w/Pipe
Displacement: 0.91 cu in (14.9 cc)
Bore: 1.09 in (27.7 mm)
Stroke: 0.98 in (24.8 mm)
Practical rpm: 2,000-16,500
Output: 3.55 hp @ 15,500 rpm
Weight w/o muffler: 21.3 oz (603 g)
Weight w/pipe (OSMG1982): 29.1 oz (826 g)
http://www.osengines.com/engines-he...1981/index.html

That means 17k is not good.
You are asking US if 17k is okay, but the manufactures says "No".
Good luck.

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10-25-2013 09:20 PM  4 years agoPost 9
Kristian M

rrNovice

Norway

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Scott Gray runs 17600 rpm
For F3C, Scott Gray run his OS at 17600 rpm. His model was FAST!

http://www.scottgrayrc.com/sylphide2009.html

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10-25-2013 09:49 PM  4 years agoPost 10
ticedoff8

rrKey Veteran

Morgan Hill, CA. USA

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And, he gets his motors for free (lol), so he can do whatever he wants.
Us mere mortals? We have to pay for our mistakes.
Having said that...
Run it as fast as you want - let us know how it works out.

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10-25-2013 09:53 PM  4 years agoPost 11
dchekas

rrKey Veteran

Farmington, CT

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I would not run much over 16,000 RPMs.

I am currently running my OS 1.05HZ-R at 1980 with an 8.2 gear ratio. The engine is turning around 16240. No need to go higher.

I've played with the 8.0 ratio, but prefer the added torque the 8.2 ratio gives.

Team Align, Team Futaba, Team Byron Fuels, Team Thunder Power

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10-25-2013 11:14 PM  4 years agoPost 12
McKrackin

rrProfessor

Lucasville,Ohio

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For F3C, Scott Gray run his OS at 17600 rpm. His model was FAST!
It also has an after market custom head with a little lower compression and dual glow plugs to make up for it in mid range RPM.

I literally never use the word literally right.

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10-26-2013 01:23 AM  4 years agoPost 13
devin120

rrVeteran

Canada

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100 rpm on the head is about 700 on the motor. Youll be leaving the powerband. Increase pitch if you want more pop?

And its yoru fbl controller which will determine your roll rates in this age of technology. I would work on cyclic agility on your fbl system, pop with pitch and run 30%. Its quite a difference.

100 on the head is not an efficient way to obtain the results you want.

My two cents.

Miniature Aircraft - OS power - Futaba electronics

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10-29-2013 12:31 AM  4 years agoPost 14
airdodger

rrElite Veteran

Johnston USA

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Many factors are involved, how you load the engine, meaning head speed,gearing,(blade profile,weight,length). Muffler choice,fuel nitro percentage, weight of the heli. Oxygen in the air, altitude changes,also temperature. No two engines are identical, yours may be a power house another just ok,. These engine figures are usually given without exhaust restrictions, makes it hard to compare with mufflers. Tuned pipes can give as much as a 20-30 percent increase in power, how many people have you seen use a pipe recently? Want more power just increase the nitro, if you don't load a nitro engine enough you will not get the power you expect. How you Load the engine changes the timing. Too much load restricting the piston stroke can hole a piston, too little load will never generate the max push. Not as simple as picking an rpm. If the torque only drops a little more rpm means more fuel consumed in a given time equates to more power. A few hundred rpm or even a thousand should not be a problem. If you go through bearings, back off a little.

Chris

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10-29-2013 12:46 AM  4 years agoPost 15
ICUR1-2

rrElite Veteran

Ottawa, Ontario

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already posted
Practical rpm: 2,000-16,500
Output: 3.55 hp @ 15,500 rpm

16,500 would be the max recommended
15,500 is the end of the power band

depending on how heavy it flies 16000 would be my target

I wouldn't worry about HS so much as the engine. Maybe try different size blades they can make a huge difference

spending time, paying attention

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10-29-2013 05:09 AM  4 years agoPost 16
shinysideUP

rrApprentice

USA NJ, NY

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Thanks for the input guys, however I must add that I have an HZ-R non speed version.

Fly hard, fly low, fly till she leaves and never comes back.

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10-29-2013 07:18 AM  4 years agoPost 17
Zbawer

rrApprentice

Singapore

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for the non-speed version the specs are the following ones :
Practical rpm: 2,000-16,000
Output: 3.35 hp @ 15,000 rpm
So I think 15,500 RPM, translating to 1,937 HS on your setup, would be a suitable target.

Then what about YS engines ? I hear 91 SRs will output their max power at higher RPMs ?
They don't give much info on the website, only that PRACTICAL RPM is 2000~17,000

If you have extra bucks to spend I'd say you should upgrade to OS 105 and get a 1 tooth bigger pinion so you can optimize the extra power / torque and therefore sustain higher HS.
I plan to do that someday for my beloved Kasama Srimok.

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10-31-2013 12:03 AM  4 years agoPost 18
gouki

rrVeteran

philippines

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you're using 15%? try 30% and see if there's any improvement on the performance you want without increasing headspeed

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10-31-2013 12:37 AM  4 years agoPost 19
shinysideUP

rrApprentice

USA NJ, NY

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Already at .2mm shim on 30%.

Fly hard, fly low, fly till she leaves and never comes back.

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11-02-2013 11:10 PM  4 years agoPost 20
shinysideUP

rrApprentice

USA NJ, NY

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Update, tried 8:4 up from 8:0, lol its not good flying spirited at 1920, I need more.

Fly hard, fly low, fly till she leaves and never comes back.

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HomeAircraftHelicopterEngines Plugs Mufflers Fuel › Running my 91HZ-R a few hundred rpms over, will it hurt motor
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