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HomeAircraftHelicopterMain Discussion › why do people not use 4 strokes on helis?
03-06-2008 05:06 PM  10 years agoPost 1
Wingman77

rrProfessor

Pulaski Tennessee

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I have put a saito 4stroke engine on a plank I have and it has wicked power and reliability, and it sounds good to. so why do people not use 4 strokes in helis?

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03-06-2008 05:10 PM  10 years agoPost 2
dannyh5

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England

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They used to but 2 stoke has a better power to weight radtio. A friend of mine had a Baron 30 with a 4 stroke.

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03-06-2008 05:12 PM  10 years agoPost 3
JRjoe

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Jonesville , IN USA #1

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I had a 4 stroker heli once. It didn't have a lot of power. Flew ok and sounded cool but that was about all.


JRjoe.....
Indoor plumbing??? No, we don't need that!!!

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03-06-2008 05:12 PM  10 years agoPost 4
Wingman77

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Pulaski Tennessee

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have people not tried the new 4 strokes? maybe you do get better power out of a os 50 hyper or somthing but it seems a saito would hold its own.

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03-06-2008 05:20 PM  10 years agoPost 5
GimbalFan (RIP)

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Big Coppitt Key, FL

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RC 4-strokes will always have less power than a 2-stroke of equal weight.

According to OS, a 2-stroke Hyper50 outputs 1.9 hp and weighs just under 1 lb. Their FS-52H Surpass 4-stroke heli engine weighs slightly more but outputs less than half the power.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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03-06-2008 05:21 PM  10 years agoPost 6
Ed1955

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Pocono Mountains, PA USA

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Two Strokes.....
Twice the power, half the weight and not to mention instantanenous power when you need it!
Ed

Progression of Addiction, CX2, T-Rex 450's (2) & finally a T-Rex 600E, Electric Bliss!

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03-06-2008 05:22 PM  10 years agoPost 7
BarracudaHockey

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Jacksonville FL

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Plus most are geared for the high rpm output of the 2 strokes.

I can be done but its more of a curiosity due to the lower rpm band and the increased weight and complexity.

Andy
AMA 77227
http://www.jaxrc.com

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03-06-2008 05:23 PM  10 years agoPost 8
Wingman77

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Pulaski Tennessee

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ok ok... but in that case why do 4 strokes more popular on high performance planks?

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03-06-2008 05:24 PM  10 years agoPost 9
Wingman77

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Pulaski Tennessee

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yea I guess 2 strokes do normaly turn more rpms.

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03-06-2008 05:26 PM  10 years agoPost 10
BarracudaHockey

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Jacksonville FL

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Depends on what you consider "high performance"

Straight away speed I'd take a 2s any day. Lower rpm high torque, big prop I'd go 4 stroke. All depends on what you're after.

Andy
AMA 77227
http://www.jaxrc.com

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03-06-2008 05:26 PM  10 years agoPost 11
GimbalFan (RIP)

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Big Coppitt Key, FL

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why do 4 strokes more popular on high performance planks?
Hp/wt isn't as critical for performance with planks as it is with helis, especially large planks -- plus the fuel economy is better.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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03-06-2008 06:07 PM  10 years agoPost 12
Furious Predator

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Kitchener, Ontario, Canada

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Twice the power, half the weight and not to mention instantanenous power when you need it
not really twice the power. i remember reading a book on 2 stroke and four stroke engines when i was starting out the hobby. they said that 4 strokes generally produce about 70% of the power of an equivelant 2 stroke. they said it was due to the fact that the cylinder has an extra stroke to get rid of its burnt gases for a more complete combustion when it does ignight.

Shawn
Team Leisure-Tech
Team HelixRC

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03-06-2008 06:48 PM  10 years agoPost 13
Four Stroker

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Atlanta

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Some of us human oddities are still flying 4 strokes. See the gallery ! Many still have an old XCell 4-stroke with the YS90.

The YS63S puts out about 1.6 HP which is short of 1.9 HP but about the same as the old OS46H.

Four Strokes are an amusement, not really practical, like turbines.

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03-06-2008 08:39 PM  10 years agoPost 14
Mark C

rrKey Veteran

Houston, TX - USA

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These are becoming regulars at our field
This is a Vario Boker 4-Takt (4-Stroke). Notice the twin mufflers.

They play the note of the 1.80 twin O.S. engine

The heli beside it here is a Vario SkyFox 4-stroke powered by an O.S. 91.

Both models belong to Mr. Spies here.

I have flown the SkyFox. It flies with incredible smoothness and performs well. It is no 3D machine but it flies with good power and is just plain clean fun to purr around the sky with.

Once Mr. Spies gets all of the kinks worked out of the Boxer maybe I'll get a chance to fly it as well

These machines are designed and geared from the start as 4-stroke machines. They are not intended for 3D. They are targeted towards sport flying and possibly scale. They have proper cooling cowlings and all the correct gearing to accomodate the 4-stroke power plants. From what I can tell so far they are excellent quality machines. If the Boxer performs with twice the power of the SkyFox it will indeed be a handfull!

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03-06-2008 08:55 PM  10 years agoPost 15
AirWolfRC

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42½ N, 83½ W

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For some reason, the lower frequency sound of a 4 stroke seems more desirable. For the fuel used, it's more efficient. But that's where the efficiency stops. 2 stroke wins when you talk power to weight ratios.

If you want "kool" sound, get a 4 stroke.
If you want power, go 2 stroke.

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03-06-2008 09:09 PM  10 years agoPost 16
joeycoates

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Dallas, Texas

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The OS Hyper weighs 14.3oz with no pipe and makes 1.9hp, the Saito 82 weighs 17.6 with pipe and makes 1.5hp. I would bet that the Hyper with a MPII weighs very close to what the 82 weighs, and while the 82 has less HP I would bet some money that it spanks the OS in torque.

I understand that the old 4 strokes did not have much in the way of balls, but the new ones do. If a helicopter were designed and geared for the 82 I bet that a lot of people would be suprised.

Oh, a 4 stoke has much quicker throttle responce then a 2 stroke, this is why htey are so common on 3D style airplanes, you need the instant and very linear power that a 4 produces. This is not to say that a 2 stroke cannot be used for 3D airplanes as I have a Reactor with an OS55ax and a Katana KL with an OS 1.60fx and both do just fine, but I also have a YS91ac and niether 2 stroke can hold a candle to the way the ys can spool up from ANYWHERE in its operating range be it idel or mid throttle, that YS is rediculously quick.

I am sure that many on here may argue with what I have said, but I fly both the 2's and 4's, have for 22+ years. The 4's spool quicker and make A LOT more power then they did in the days of the old Saito 65's.

Here is another comparisson of two engines that are regaurded as being roughly equal in the 3D airplane arena...

OS55ax 17.1 oz w/muffler 1.75hp
Saito 82a 17.6 oz w/muffler 1.5hp

The HP points towards advantage OS, but by and large the 82 will outpull the OS. And the Saito spools up quicker with a bigger prop, ask me how I know.

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03-06-2008 09:48 PM  10 years agoPost 17
GimbalFan (RIP)

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Big Coppitt Key, FL

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Interesting.

op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t

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03-06-2008 09:58 PM  10 years agoPost 18
kcordell

rrElite Veteran

O Fallon, MO

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I used to fly an Xcell with a YS90 four stroke motor. Power is down a little, but torque is much higher. It was a great drag race model, just get it wound up and it would jump. I could pull tons of pitch. There were some minor modifications that were made to the barrel to get better fuel flow. Also, when you hit idle up, you had to wait a second or two for the motor to wind up. Otherwise it would conk out or choke up pretty bad. The sound was GREAT! The model was fine for competition, plus it used less fuel. I could actually use a smaller fuel tank, save on a little weight. Trouble was wedging all that motor in between the frames. All of the models are designed for two strokes so it took a little work.

Team Futaba, Team Synergy/Rail, Team Scorpion, Team Castle Creations, YS Engines, VelTye

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03-06-2008 10:00 PM  10 years agoPost 19
bigdad390

rrVeteran

East. Liverpool, Ohio

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not really twice the power. i remember reading a book on 2 stroke and four stroke engines when i was starting out the hobby. they said that 4 strokes generally produce about 70% of the power of an equivelant 2 stroke. they said it was due to the fact that the cylinder has an extra stroke to get rid of its burnt gases for a more complete combustion when it does ignight.
Yes, that is true of the engine, but most 2 stroke cycle engines use a tuned exhaust which can cramm up to 20% more air and fuel into the cylinder for more power out of the shorter power stroke as well as help scavange the exhuast gasses out.

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03-07-2008 01:59 AM  10 years agoPost 20
ellio

rrNovice

Marysville CA

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Kyosho used to market a 4-stroke helicopter. If my memory serves me correctly, I believe it was called the "Virago." Can't comment on it though because I never owned one. I always thought it would be kind of cool to own one.

Thelma, get your butt home!

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HomeAircraftHelicopterMain Discussion › why do people not use 4 strokes on helis?
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