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HomeAircraftHelicopterMain Discussion › X-spec - head speed & Gear ratio
10-17-2005 12:34 AM  12 years agoPost 1
enam100

rrApprentice

Harlan, KY, 40831

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Hello, what would be the proper head speed for x-spec with 7.91 gear ratio (i think), I run YS91 and seems like I am not getting the full power from the YS91 engine, Please advise whether I should change the gear ratio or need to increase the head speed. Right now it is at 1750.

Regards

With regards Enam

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10-17-2005 12:56 AM  12 years agoPost 2
ErichF

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Sutton, NH

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I know Pete Niotis is using a YS91 at 7.91, with good results. Up the head to 1800-1850. What blades?


Erich

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10-17-2005 12:58 AM  12 years agoPost 3
white chocolate

rrKey Veteran

Baltimore, Md.

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At 7.9 your way to low on the headspeed. You need to run 1900 at that ratio. It also depends on what muffler you are using.

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10-17-2005 01:28 AM  12 years agoPost 4
JitsuGuy

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Tulsa, Oklahoma

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Not to highjack the thread, but what head speed should I be running at a 8.45 ratio and a YS 91 with my Freya?

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10-17-2005 02:56 AM  12 years agoPost 5
enam100

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Harlan, KY, 40831

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I have SB16 with Maverick 680 baldes. So, 1900 would be fine then ??

With regards Enam

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10-17-2005 03:50 AM  12 years agoPost 6
pookie8

rrApprentice

austin,tx

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i have the ys in my x spec and run a mp2 with 7.91 1900 headspeed is good with that combo .. the evo with 8.45 is better at 1750 .

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10-17-2005 04:37 AM  12 years agoPost 7
JitsuGuy

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Tulsa, Oklahoma

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Let's talk head speeds let's talk (clap clap) let's talk head speeds let's talk (clap clap)!!!

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10-17-2005 06:53 AM  12 years agoPost 8
Jason WAI

rrVeteran

Hong Kong

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" YS will work best at the 8.4 to 1 ratio. The YS engines like to turn a higher RPM . "

as suggested by Curtis

http://www.curtisyoungblood.com/faq...=Engines::YS 91

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10-17-2005 09:21 AM  12 years agoPost 9
mrNoodles

rrProfessor

Borlänge, Sweden

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8.45
1750-1800rpm should work fine.

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10-17-2005 04:25 PM  12 years agoPost 10
JitsuGuy

rrKey Veteran

Tulsa, Oklahoma

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Crap, I was running it at about 1820 this weekend for 3d stuff... Anything else seemed a little dead to me. Is that too much for that engine/gearing combo?

J

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10-17-2005 07:47 PM  12 years agoPost 11
Chopper

rrKey Veteran

Stow,Oh- oops, I mean St Louis, nope Stow again,

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The YS will run all day at 1850 rpm and 8.45 ratio. That is the best ratio and speed for that engine for hard 3d. Sport flying can easily use a taller gear such as 8.08 to 1.

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10-17-2005 09:35 PM  12 years agoPost 12
JitsuGuy

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Tulsa, Oklahoma

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Awesome! I'm gonna crank it up then tonight! It really did seem like the sweet spot was higher then what a local pilot recommended to me. But being some what of a newb I didn't want to push it.

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10-18-2005 01:15 AM  12 years agoPost 13
white chocolate

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Baltimore, Md.

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If you keep it at 1750-1800 and fly it for awhile you will get used to it and realize that there is tons of power. I ran it there and didnt like at first but accidently kept it there!! Then after two weeks I realized I had been flying at that speed. Definatly had power!!

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10-18-2005 02:04 AM  12 years agoPost 14
Mike Wilson

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Toronto, Canada

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Running the YS at 8.45 with and 1850 headspeed is ok as long as the engine is kept a little on the rich side. You will also want to make sure you minimize the overspeeding with a governor. I have seen many a connecting rod break due to either overheating or overspeeding on the YS at those speeds. I fly my YS at 1850 with an 8.57 gear ratio in my Dyna-x and so far so good but I am very careful not to run it lean.

....led

Teambob00

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10-18-2005 02:21 AM  12 years agoPost 15
JitsuGuy

rrKey Veteran

Tulsa, Oklahoma

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Okay, cool... Thanks for the input fellers!

J

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10-18-2005 03:19 AM  12 years agoPost 16
nighttrain

rrApprentice

Louisville KY

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I fly my X Spec at 1980 rpm. YS 91, SB-16, 7.91 more FAI style. It's a very fast heli w / 700mm rotortechs.

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10-18-2005 12:50 PM  12 years agoPost 17
ErichF

rrElite Veteran

Sutton, NH

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1980??
Holy BALLS!

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10-18-2005 01:38 PM  12 years agoPost 18
mrNoodles

rrProfessor

Borlänge, Sweden

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No problems running 1950-2000rpm.
(7.92 ratio that is)

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05-24-2006 10:18 PM  12 years agoPost 19
THX1138

rrElite Veteran

Indianapolis, IN

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To re-cap...
If you use the stock gear ratio of 7.9, run a head speed of 1900 and all is well. Has anyone had any issues with running the head this high on a 90 sized bird?

What is necesary for the gear change if I want to go to 8.45? Just the 11t pinion?

Lou

Just give me five dudes and two flashbangs...

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05-24-2006 11:50 PM  12 years agoPost 20
TMoore

rrMaster

Cookeville, TN

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If you take the max RPM spec for a YS or an OS and multiply by .95 and then divide by the gear ratio this will reveal the headspeed to shoot for.

I've done this for years and it works.

For example an EVO 90 at 7.91 running a C-Spec should run comfortably at 15,200 rpm. This will result in a headspeed of 1921. In my mind any HS in the 1850-1900 range would be good for this machine. Especially if you are running TT 710's which weigh in around 208 grams. On Radix 710's or V-Blade 690's which weigh around 185 grams you should be even safer and not have to replace thrust bearings with any higher frequency than is normal.

On an 8.45 machine you could run 1800 and be ok with the OS. The YS could probably turn a little faster but either way both engines should make good power.

TM

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