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Home✈️Aircraft🚁HelicopterThunder TigerOther › Converting to 50v2 from 30v2 - Pinion gear question...
09-07-2006 07:28 PM  14 years ago
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Vendetta

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Miami, Florida 33173

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Converting to 50v2 from 30v2 - Pinion gear question...
The manual for some reason suggests keeping the 9.6:1 ratio vs the new pinion and main gear supplied for 8.5:1... Why? I'll be using a hyper 50 with the long boom and blades....
-- Gentlemen, we can rebuild it... We have the technology....Better…stronger…faster...--
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09-07-2006 07:49 PM  14 years ago
jschenck

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La Vista, NE.

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I'd run the 8.5 gears like the stock V2 with 600mm blades.

What manual suggests running the 9.6 gears with a 50?
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09-07-2006 08:06 PM  14 years ago
BarracudaHockey

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Jacksonville FL

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With the 30 gears you will be able to get into the power band of the hyper at a lower head speed, you might give it a shot and see how you like it.

The 8.5 gears IMO are a little high (or low?) and make you run the head @ 2000 to get good response from the engine. The Titans 8.7 optional gears should be better but there's lots of people that swear by the 30 gears in a 50.

Like I said, try it and see.
Andy
AMA 77227
http://www.jaxrc.com
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09-07-2006 09:16 PM  14 years ago
AirWolfRC

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42½ N, 83½ W

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If you want good performance (3D), you need higher head speed in a 50 and even more in a 30.

A 90 with 710 blades at 1800rpm has a tip speed of about 490fps.
A 50 with 600 blades at 2130rpm has a tip speed of about 490fps.
A 30 with 550 blades at 2300rpm has a tip speed of about 490fps.

To get the same lift per inch of blade diameter, you need to have the same blade velocity. Since the shorter blades have less inches of blade, even at the same blade velocity, the rotor disk will still be producing less lift for the same blade Angle of Attack.

To keep the head speed up, you need to use the 8.5 gears and even then you will only be close.

This is why a 90 at 1800rpm will ALWAYS outperform a 50 at 1800rpm.

Wolfgang
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09-07-2006 09:56 PM  14 years ago
BarracudaHockey

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Jacksonville FL

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Thats not true and there's plenty of pilots that will throw these things around at lower head speeds. Its not just the RPM and or tip speed that matters.Andy
AMA 77227
http://www.jaxrc.com
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09-07-2006 10:01 PM  14 years ago
AirWolfRC

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Oh ? The numbers don't lie, and if you think they do then you haven't looked close enough at the numbers or maybe missed a few.

For the same Angle of Attack, lift is a direct function of blade area and blade velocity (not rpm).

Wolfgang
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09-07-2006 10:16 PM  14 years ago
BarracudaHockey

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Jacksonville FL

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Have you flown a 50 with 30 gearing and a hyper?

There's more to performance than lift.
Andy
AMA 77227
http://www.jaxrc.com
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09-07-2006 10:18 PM  14 years ago
AirWolfRC

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There's more to performance than lift.
I agree . . . and without lift . . . there is no performance.

Wolfgang
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09-07-2006 10:39 PM  14 years ago
BarracudaHockey

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Jacksonville FL

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I'll take that as a no.

I respect your posts, you have a lot of good information, but dont dismiss something out of hand that you havent tried.
Andy
AMA 77227
http://www.jaxrc.com
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09-07-2006 10:58 PM  14 years ago
AirWolfRC

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I don't have a 50 Hyper. I don't plan on it either.

But keep in mind that if you have the grunt to push a blade through the air with a higher AoA, you will definitely produce more lift to let you do more responsive 3D, etc.

Also keep in mind that with a higher head speed, you need less blade pitch and you have more potential energy in the rotor disk to get you past those high drag "humps" in some maneuvers.

Everything else being equal, I like 2000rpm better than 1800rpm on a 50 with 8.5 gears.

Wolfgang
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09-07-2006 11:15 PM  14 years ago
Vendetta

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Miami, Florida 33173

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It was the 30 to 50 manual that suggests the 9.6:1 ratio. I'm going to 8.5:1.. thanks for the info folks ...-- Gentlemen, we can rebuild it... We have the technology....Better…stronger…faster...--
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09-08-2006 01:32 AM  14 years ago
BJames111

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San Diego, California

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I've been using the "titan" gear ratio, and it seems a little boggy compared to the stock 50 gears. I raised the rpm to 1950 and it still doesn't feel as snappy as the stock ratio.
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09-08-2006 02:50 PM  14 years ago
NORTHERNLIGHTS

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Riverview FL

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OK gotta pipe in here.......Unless you have tried it then don`t knock it....

Airwolf, with all said and done! Headspeed versus blade Angle, versus Blade stall. Now where in, does all this lye?

After looking at your profile and pictures I see that you don`t fly 50`s well thats great.

We people that do fly 50`s have been working on trying to get a 50 to perform like a 90. I have a 50 that performs like a 90 running a headspeed of 1900.ie 9.56 ratio. Yes it runs the 50 at 18164rpm. This is great considering your theory of disc loading, and unloading. Well when you load the disc it drops the 50 back into its working rated rpm of 17000 which is only 121 blade rpm.

The biggest problem is there is not the perfect gear offered in the "Raptor Setup" that would be ideal.

Also we are not working with the torque that the 90 size engine offers.

So the bottom line is I run the best gear that is available, so I use the most torque out of the engine for a predetermined blade rpm.

Now if you want to open another can of worms, and maybe you can answer this with all the graphs. What is the blade length versus rpm before you induce Tip Stall? Yes I know Tip Speed increases with blade length.

So given a 700mm blade what is the main rotor rpm before you induce tip stall? Are these the speeds I am in question of?

A 90 with 710 blades at 1800rpm has a tip speed of about 490fps.
A 50 with 600 blades at 2130rpm has a tip speed of about 490fps.
A 30 with 550 blades at 2300rpm has a tip speed of about 490fps

I look forward to your answer....
B.O.A.T. Break Out Another Thousand!
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09-08-2006 03:07 PM  14 years ago
AirWolfRC

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42½ N, 83½ W

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After looking at your profile and pictures I see that you don`t fly 50`s well thats great.
I see that you have failed to look at my home page.

One approach to setup is to run the engine above it's peak HP rpm and is putting out less power than it's maximum. That way, when the motor gets loaded up it will come down in rpm slightly, increasing it's power output for a basic kind of speed control. This rpm is listed for most motors. Depending on the 50 size motor, it's about 16,000 or 17,000 rpm.

The OS Hyper is rated at 1.9HP at 17,000 rpm.
The TT-50 is rated at 1.75HP at 17,000 rpm.
The OS 50 SX-H is rated at 1.8HP at 17,000 rpm.

These speeds used to be down at 16,000 rpm.
Marketing has pushed up the numbers.

Using this setup approach, running the Hyper at 18,000 rpm with 9.56 gears gives a head speed of 1884. This can work reasonably well. 8.5 gears needs a head speed of 2118. This may be why the manual says to use the 9.56 gears. The manufacturer doesn't like that high a head speed.

Fact is that even at 2118 rpm head speed, the tip speed and centrifugal force is still less than a 90 size with 710 blades at 1800 rpm. . . . So I don't see the problem.

As for tip stall . . . That does not apply here. Tip stall is when the blade AoA exceeds about 16º. This is very difficult to do.

Wolfgang
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09-08-2006 03:21 PM  14 years ago
NORTHERNLIGHTS

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Riverview FL

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Yes, I looked at your gallery not HPB.O.A.T. Break Out Another Thousand!
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09-08-2006 03:47 PM  14 years ago
NORTHERNLIGHTS

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Riverview FL

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Airwolf, It is not a problem. What you have said just reafirms what I have said about the 9.56 gear. The 90 has the torque to pull the higher blade angles. The 50 doesn`t with the 8.5 gear ratio unless you swing the blades around 2100. We all know that 2100 isn`t real good on the 50 size head. So I have been trying different gear ratios as many others have. My conclusions are a little different than others. 1900 to 2000 rpm with the higher gear ratio keeps the hyper singing, and longevity isn`t the best but it performs well.

PS I looked at the Homepage, and like the Gen setup on the 50
B.O.A.T. Break Out Another Thousand!
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