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Midland Helicopters . HeliProz . Ron’s HeliProz South

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Thunder Tiger Raptors 30-90 - Imperio > New gear ratio on Rappy 50 rocks
 
 
NORTHERNLIGHTS
Veteran
Location: Riverview FL

My Posts This: Topic  Forum

I`m thinking I will try the 2200 when I get home. The Kasama Head looks like it will take it. Its more a question of whether the spindle will take it and the tail rpm which has been a question. I have upgraded the tails on both helis with thrust bearings. I might go back to 92 tail blades and reduce the centrifugal force. Next thing is fooling the govenor! It only goes to 2100 on the 12Z...LOL

B.O.A.T. Break Out Another Thousand!
10-17-2006 03:46 AM
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AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

My Posts This: Topic  Forum		You may have to lie to it by telling it a different gear ratio.

Wolfgang
10-17-2006 03:52 AM
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NORTHERNLIGHTS
Veteran
Location: Riverview FL

My Posts This: Topic  Forum		That is the plan lie to it! Lie to myself at the same time. I am not doing this! I am not doing this.......

B.O.A.T. Break Out Another Thousand!
10-17-2006 04:02 AM
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arceye
Veteran
Location: UK

My Posts This: Topic  Forum		AirWolfRC:

710 blades running at 1800 would not scare me so much because they are rated to handle that speed and usually are held to a stronger head with stronger bolts. I don't ever remember seeing a set of 600mm blades with a rating of 2000 on the box, in fact I have only ever seen one brand of carbon blades that had a RPM rating on the box and that was 1800 ( unfortunately I don't remember which brand it was )

Running the numbers is fine and it gives a theory of what should happen but the theory is nothing more than a theory, in the real world its a totally different experience. Run the numbers all you like I used to do the same but then you will see how wrong they are if you actually try the gears. I know you can't see where the extra performance is coming from by the numbers but the fact still remains it makes a huge difference. Try driving your car up a steep hill in high gear then do the same again in a lower gear and see which gear climbs the hill better ( meaning which gear bogs the engine down less ).
A great example of how wrong theories are is take your car engine running at its max power RPM then calculate through the gearing to the wheels then calculate how fast the wheels SHOULD spin, add in the diameter of the wheels/tyres this will give a theoretical speed of the car, will that car ever reach that speed ? Not a chance.

Sorry Patriot21, for hijacking the thead but Sometimes things just can't be calculated and have to be experienced to be appreciated.


Andy


Kasama Head :(
The Blingiest DOWNGRADE a Raptor can have
10-17-2006 02:35 PM
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AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

My Posts This: Topic  Forum		arceye,
Remember one thing, figures don't lie but liars figure.
By that I mean a lot pf people don't know how to properly apply numbers.

Take your example "take your car engine running at its max power RPM". That is an engine rating. It is not a number guaranteed achievable for wheel spin after a certain gear ratio. That will depend on the load on the drive train.

It's all in the details.
If you don't have the details, you don't have the whole picture.

Wolfgang
10-17-2006 03:03 PM
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Zman
Veteran
Location: Florida

My Posts This: Topic  Forum		Starting to regret posting on this thread after it layed still for a few days .

I am not a mechanical engineer or a rocket scientist but all I can say is the new gears made a positive difference for me. Whether it helped find a sweet spot on motor or is masking my poor collective and cyclic manuevers, I really dont care. I simply posted to let everyone know I experienced the same results patriot did. Once again, thanks to him, this has been the best upgrade on my titan so far!!!

A true story from a few years ago. I work with a few mechanical engineers and we were discussing upcoming maintenance on some rail road tracks at one of our plants. I happened to mention that the tracks have a downhill grade. Well the engineer insisted they were level and then and went and got the blue prints showing they were level. I then took him out to the train and told our operator to put the engine in neutral and release the brakes. After rolling for 20-30 yards, the engineer said nevermind. What is on paper isnt always what works in real life.

Z
10-17-2006 05:04 PM
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DS 8717
rrProfessor
Location: Here wishing i was somewhere else

My Posts This: Topic  Forum		Zman, you are correct. It is pretty well know that the 8.5 ratio is really the correct ratio for the 50,it ismore crtical for the smaller engines than the larger 90 size. I have a heli with 8.63 and one with 8.7 and the 8.63 is even a bit to high. DOUG

No Es Mi Culpa
10-17-2006 06:06 PM
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patriot21
Key Veteran
Location: Eagle Lake,MN

My Posts This: Topic  Forum		Sometimes we should just forget about theory...numbers...etc.....and just try it...
That is just part of testing something..... like mentioned before... anything can look good on paper...but... bottom line... real world experience will tell all...

My rappy 50 feels great in flight..... Sure if i want I can pull the head down all day long but...with the new gear ratio...the motor recovers alot quicker..

My Sponsor:VISA
10-17-2006 06:13 PM
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Mark C
Key Veteran
Location: Houston, TX - USA

My Posts This: Topic  Forum
Quote 
Sometimes we should just forget about theory...numbers...etc.....and just try it...
That is just part of testing something..... like mentioned before... anything can look good on paper...but... bottom line... real world experience will tell all...


And this could be quite true because we take alot of numbers thrown at us such as "Peak Horsepower at 17,000" like they are biblical in origin.

Truth is... 17,000 looks like a pretty rounded number to me. You can be certain that your peak horsepower RPM varies with MANY factors such as:

The peak tuning the exhaust system is designed for
The type of fuel mixture your are using - how much nitro
The efficiency of your cooling system
Ambient air temperature
Your altitude above sea level
The rigidity of the motor mounting system

Not to mention blades, gearing, pitch, etc. etc.....

So the bottom line is try out all the gearing options available and stick with what serves you best.

If you are really anal about "why" it's best good luck. The truth may lie in some combination of factors listed above or others I haven't even thought of. If that's where you want to spend your time so be it. I think I will go burn some fuel now.

Mark C.
10-17-2006 06:46 PM
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Zman
Veteran
Location: Florida

My Posts This: Topic  Forum		Well said Mark and Patriot.

Lets go burn some fuel!!!

Z
10-17-2006 07:35 PM
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AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

My Posts This: Topic  Forum		Will someone please tell me why certain people are so against identifying why and how certain things happen the way they do ?

If you don't know, don't knock those of us who keep asking and looking for answers.

Wolfgang
10-17-2006 08:03 PM
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patriot21
Key Veteran
Location: Eagle Lake,MN

My Posts This: Topic  Forum		Airwwolf.....
I like your persistance!!!
I understand where you are coming from.... but... will you do me or yourself a favor.....
JUST TRY THE DARN GEARS OUT!!!
if you don;t like them.... toss them...

On the same note....I am not a numbers/theory man....
I tend to fly and adjust on how the bird feels in the air...

I am not knocking you airwolf...for trying to find the answers/reasons..etc....

My Sponsor:VISA
10-17-2006 08:19 PM
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MJWS
Key Veteran
Location: Airdrie, AB - Canada

My Posts This: Topic  Forum		It's all magic Airwolf. Increase torque by 2.5% get a 10x increase in performance. Quit asking questions and just drink the koolaid already.

That said I will buy that 8.5 (50) is a little tall and 9.5 (30) is a little weak. But frankly it looks to me like TT decided to keep tipspeed and engine rpm equal on 620's. Thus the tiny incremental change. If they wanted flexibility why not hit it in the middle somewhere around 9.0

The best gearing will always depend on flight styles. We can hit max power easily on all ratios. Shifting from 4th gear to 3rd gear doesn't give you more power but it might help you accellerate up a hill. 5th going down the hill will give you a whole lot more inertia going into the next hill, but will recover slowly if the hill is too big. If you are good at energy management you can get away with a nice tall ratio... and/or less overall power. i.e Szabo on a 30. I think for the proponents, they are enjoying the slightly quicker recovery. Just think how amazing 9.5 must be if 8.7 is so good.

It ain't magic. I think Dougs point about gear ratio being more critical on small engines is a good one as the torque curve is peaky especially on a pipe. The guys that think the theory doesn't match reality are just wrong. The explanation may be incomplete that's why we discuss it and tweak it.

Mike
10-17-2006 08:42 PM
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Mark C
Key Veteran
Location: Houston, TX - USA

My Posts This: Topic  Forum
Quote 
Will someone please tell me why certain people are so against identifying why and how certain things happen the way they do ?


Hell I'm not against it but I think it's pretty futile. As you said "it's only a difference of 2 and a half percent or so on gear ratio". Yet everybody is basing everything on the "17,000 RPM peak horsepower" rating which you can be pretty sure is a ballpark figure with damn well more that 2.5% error.

The first thing you would have to do to evaluate everything by the numbers is to put your engine on a dyno with all the same variables of load, cooling, mounting, fuel feed, exhaust system, altitude, ambient temperature yada, yada, yada, yada, yada, yada and get the real "Peak Horsepower RPM" rating to work off of. Then you can go do your number crunching.

And those numbers may show that with your fuel and your altitude and your yada, yada, yada that that gearing may not be optimal FOR YOU. But of course it may be optimal for the next guy. And that could even be determined by the type of flying he/she is going to do.

Mark C.
10-17-2006 08:46 PM
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AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

My Posts This: Topic  Forum		Some may consider the quest for knowledge "futile" but I'm not one of them. So please don't add to the trouble of finding answers by trying to get me to be as easily satisfied as some of you are.

Wolfgang
10-17-2006 09:31 PM
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Mark C
Key Veteran
Location: Houston, TX - USA

My Posts This: Topic  Forum
Quote 
Some may consider the quest for knowledge "futile" but I'm not one of them. So please don't add to the trouble of finding answers by trying to get me to be as easily satisfied as some of you are


No problem here. Let us know what you find out from the dyno tests. I'll even crunch the numbers with ya. I got to go burn some more fuel.

Mark C.
10-17-2006 09:37 PM
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patriot21
Key Veteran
Location: Eagle Lake,MN

My Posts This: Topic  Forum		Airwolf....
You keep trying to find the answer and I will keep flying

My Sponsor:VISA
10-17-2006 09:50 PM
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Zman
Veteran
Location: Florida

My Posts This: Topic  Forum
Quote 
Some may consider the quest for knowledge "futile" but I'm not one of them. So please don't add to the trouble of finding answers by trying to get me to be as easily satisfied as some of you are.

Wolfgang


I think the difference is this is a hobby for me. What satifies me is throwing on a gear and noticing a positive change, good enough. I am also satisfied burning fuel and pushing myself to fly better. Why this gear change made a positive effect for me and several others? Dont know for sure but am not going to spend an entire week trying to figure it out, fact is it did for me, good enough. This is a 20 something dollar dang gear, if you dont see a change sell it on ebay for 20 something dollars or hang it up on wall.

Time to go burn a tank or two before dark.

Z out
10-17-2006 10:25 PM
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AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

My Posts This: Topic  Forum		You forget, the people who made the gear spent a lot more than $20.

You go right along and keep thinking like a user.
I'll go right along and keep thinking like a developer.

Wolfgang
10-17-2006 10:44 PM
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MJWS
Key Veteran
Location: Airdrie, AB - Canada

My Posts This: Topic  Forum		If I had to guess, Wolfgang. I would say they probably did it so we wouldn't have to take 620's up to 2100 to drop them into the torque. I'm suprised actually that they didn't go a little further if their intent was to change the feeling of the power curve or performance up.

This is an incremental change so the 620's don't feel sluggish, imho. It's easier to load the big blades up. I don't doubt they feel slightly different. 1/8th turn on the top needle feels different as well.

Another reason I could see is that it gets the less aggressive user Say 1900-2000 a little closer to the peak power without screwing too badly with their fuel economy, or revving the piss out of their motor.

The other thing is it may well hit the sweet spot on one of the electric set ups they've tried that needed just a shade more headroom to keep joe average from burning something up.

Not a bad discussion, imho. LMAO at the user/developer analogy.

Mike
10-17-2006 11:44 PM
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Thunder Tiger Raptors 30-90 - Imperio > New gear ratio on Rappy 50 rocks
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