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HelicopterMain Discussion › Why does my Trex fly so effortlessly compared to my Raptor
09-06-2009 07:49 PM  8 years agoPost 1
GC1

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Manchester, UK

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Firslty this isn't a Raptor bashing thread. I've been flying helis for about two years, initially with a Raptor 30. I couldn't recommend this model highly enough for a learner. I then moved up to Raptor 50 Titans. Again very nice, smooth and stable, however I started to get the feeling the my Trex flying mates were performing neater rolls and bigger loops with less effort.

Last month I purchased a Trex 600 Pro to satisfy my curiosity and it flew just how I thought it would. The best way to describe how it feels is light on the sticks. Less power to leave the ground and climbs like it's on fire.

As the Raptors and Trex models at my club have either Redline or Hyper motors the power plants can be regarded as the same. My Raptor was running a -10/+10 pitch curve and the Trex is more like -11/+11.

Initially my club mates and I put this down to the Trex weighing much less, however we weighed a few Raptors and Trexs' today and were shocked thay they are very similar. Some of the Trexs' were heavier.

So why why does the Trex power out and perform moves like it's weightless by comparison? The best my clubmate came up with was that the Trex had 3 servos pushing the pitch but I'm not convinced with that one.

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09-06-2009 08:03 PM  8 years agoPost 2
Thomas Moore

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California

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I think it is partially the head design, although I could be wrong.

Thomas Moore Team Avant Team Edge

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09-06-2009 08:07 PM  8 years agoPost 3
Kjarman

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noblesville, IN

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My friends and I have talked about this as well.... take a look at your main gear pinion ratio.....it's like 170T main gear and a 20T pinion compared to your raptor that has a 85T main gear and a 10T pinion. Although they are both 8.5 gear ratio the Larger diamiter main gear and 20T pinion mean the the torque required to move the main gear is drastically reduced providing more available torque for the blade system.

Simple tearms.... it's super efficent. That's why it has the crazy whine to it as well.... The Oden 90 uses the same principle....I challenge someone to bog an Oden 90!!!!

I sold another one to Terrafirma...... wife wants to know where the money's at!!!!

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09-06-2009 08:11 PM  8 years agoPost 4
Thomas Moore

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California

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anybody can bog a heli.... doesn't matter what it is.

Thomas Moore Team Avant Team Edge

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09-06-2009 08:24 PM  8 years agoPost 5
xcell90

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Michigan

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Gear ratio is a gear ratio......

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09-06-2009 08:32 PM  8 years agoPost 6
Kjarman

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noblesville, IN

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"Gear ratio is gear ratio"..... hmm.... don't tell that to a physicist..... because it's not true. How you get to the ratio is just as important.

Have a flown an Oden??...... If not I challenge you!!!!

I sold another one to Terrafirma...... wife wants to know where the money's at!!!!

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09-06-2009 08:41 PM  8 years agoPost 7
Kjarman

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noblesville, IN

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Here.... maybe this will help... seeing as noone is going to take my word for it.

http://www.dynamicscience.com.au/te...echanicalad.htm

Mechanical advantage my friends....

All of these things must be taken into effect when calculating the effiecency of a gear system.

P => Power

E => Energy

W => Work

f => Force

t => torque

d => distance of translational motion

q => angle of rotational motion (in radians)

v => velocity of translational motion

w => angular speed (in radians per second)

d => change

Pd => Pitch diameter

n => number of teeth on a gear

nrev => number of revolutions

I sold another one to Terrafirma...... wife wants to know where the money's at!!!!

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09-06-2009 08:44 PM  8 years agoPost 8
xcell90

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Michigan

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Well I won't argue but a 8.5 gear ratio is a 8.5 gear ratio.
It's aparently your not an engineer. Inerta has no impact with these small light gears. The rotor head is the differance.

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09-06-2009 08:49 PM  8 years agoPost 9
Kjarman

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noblesville, IN

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Here let me post this again... read it carefully and take a physics course.

All of these things must be taken into effect when calculating the effiecency of a gear system.

P => Power

E => Energy

W => Work

f => Force

t => torque

d => distance of translational motion

q => angle of rotational motion (in radians)

v => velocity of translational motion

w => angular speed (in radians per second)

d => change

Pd => Pitch diameter

n => number of teeth on a gear

nrev => number of revolutions

Pay particular attention to the bottom two

I sold another one to Terrafirma...... wife wants to know where the money's at!!!!

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09-06-2009 08:59 PM  8 years agoPost 10
RCHSF

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NC

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Take your 10 speed, and put it on the smallest gear on the rear axil, and the larger gear in the front, and go up a steap hill, you'll see how effiecent your sweat becomes.

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09-06-2009 09:01 PM  8 years agoPost 11
A. Bundy

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Aurora,IL. 30W/SW of Chicago

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Where is Airwolf when you need him????

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09-06-2009 09:06 PM  8 years agoPost 12
colsy

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Cambridge, UK

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Although the 'science' quote above is correct.
This whole scenerio is based on 'FEEL'.
Ive had 7 raptor 50's, and 5 trex 600's.
There wasnt anything i liked about the trex's in any way.

I dont fly trex 600's anymore, other than a 600E. and none of my 600's outperformed my R50's in any 'logical' way whatsover.

In fact i will put my balls on the line and say categoricaly all my raptors were more predictable and stable than any 600 i ever flew or owned.

Period.

Col.

Only Quote From Experience.

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09-06-2009 09:20 PM  8 years agoPost 13
GC1

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Manchester, UK

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Col

As I said this isn't a Raptor bashing thread, however the Trexs' climb out in a different league. It's as though thy either way a lot less (not the case) or have a bigger motor (not the case).

Some of the gear ratio explainations sound like it may explain what I'm feeling through the sticks.

Just out of interest why did you by 5 Trexs' if you didn't like them in any way

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09-06-2009 09:20 PM  8 years agoPost 14
Kjarman

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noblesville, IN

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It's about lever effeciancy.... a larger diameter gear system will use less force to propel the same gear ratio because each tooth in the system is nothing more then a lever that must lift a given force. The shorter the pitch of the lever the less force is required to move the given system.

This is known as Gear Pitch and it makes a big difference in the effiecancy of a system. The Pitch of the T-Rex system is significally higher then that of the Raptor system.

Think about it... Align makes vacumes.. they have the whole gearing thing figured out... and they are laughing all the way to the bank when it comes to torque.

I sold another one to Terrafirma...... wife wants to know where the money's at!!!!

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09-06-2009 09:21 PM  8 years agoPost 15
Gearhead

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Vt

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heads do make some difference,, but so-more important is the CG,, my Compass Sport is a better 3D heli than my Raven, well it was until I mounted the Compass Head on my Raven, then I found the head really was not much better than my Century Head,,

it was the CG that was the biggest factor between the 2 helis !!

and what "Kjarman" said, right on, ask the guys that Race RC Cars, they will tell you the same thing..

Jim
Buzz Buzz Buzz

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09-06-2009 09:21 PM  8 years agoPost 16
QuantumPSI

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Atlanta, GA

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I'm going to have to agree with the others on this one. A gear ratio is a gear ratio. Yes the force on the smaller diameter gears are greater, but the total torque is the SAME! Though true the larger main gear lowers the necessary torque, but you forget that the larger pinion gear INCREASES that torque (this is actually an incorrect statement to be technical, but I don't how else to explain it :confused. In the end, the final torque/power to the rotorhead is roughly the same (same RPM, same blades, same pitch therefore same torque). The total torque to the head maybe SLIGHTLY different but this is due to the difference in the moment of inertias of the two heads. Given the small radius of the parts (compared to the blades), you may as well neglect this aspect. A big power concern though, is the tail rotor and how it's driven. I am not going to get into belt vs. torque tube, but just know that there is a difference. Is that difference enough to account for the difference in performance? A true analysis will have to be done to answer this question. The 600N gear train (ignoring the tail) has more inertia than the Raptor, actually leaving more available power to the blades (but this is a poor analysis since you can't neglect the tail (it consumes a LOT of available power)). It would SEEM to be that the belt drive is robbing the system of whatever advantage it had over the 600N. (A simple dynamic analysis will show that a significant amount of energy is lost to the belt, I won't explain why here though).

To answer the OP, my GUESS (meaning, this is just my GUESS and could very well be wrong) is the control system and head design. The Raptor head gets "soft" after several flights. Even with decent servos, the control response is not crisp. Again, without a true analysis, it's hard to say if the CCPM has more collective authority than the Raptor (have to look at moment arms and all that) but honestly, my intuition (which again, could very well be wrong) says that the 600N has more collective authority with the same servos. Having said that, despite the pitiful dampeners in the 600N, I have still found that the head is stiffer and responds to inputs much crisper. Although this has little to nothing to do with collective authority, the delta setting on the 600N makes it more aggressive to cyclic inputs than the Raptor. And the final part of my "guess" is that the parts in the 600N rotorhead are significantly larger than the Raptor. This means that, even if the same material is used, the 600N head will be stiffer (this has an upper limit of course, but for our models, it doesn't matter). So with all that said, that's my GUESS.

...now where was I, dh/dt = BS-dx/dt
I will fly you forever... till earth do us part

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09-06-2009 09:37 PM  8 years agoPost 17
Kjarman

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noblesville, IN

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the Wasp......

Exactly dude..... I raced RC Cars for 10 years... this was a common Saturday afternoon discussion in the pits during race day.

I sold another one to Terrafirma...... wife wants to know where the money's at!!!!

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09-06-2009 10:12 PM  8 years agoPost 18
Gearhead

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Vt

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yeeaa, I raced from 86 to 91, back when the big change in parts and kits came, he went from stock 32 pitch to 64 pitch to 48,, 64 pitch was most efficient and created the most power but were a real pain when setting back-lash, the 48 pitch was a good medium ..

Jim
Buzz Buzz Buzz

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09-06-2009 10:25 PM  8 years agoPost 19
Dwntyme

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U.S.A.

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I see that what is missing in this is engine RPM.
True 8.5 is 8.5 However an engine that works best in a given RPM range will provide the most Tq and power. the larger gears of the TREX600 take advantage of power.

Love a Twitchy Heli.... :) and Remmington Model 700

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09-06-2009 10:31 PM  8 years agoPost 20
30636086

rrKey Veteran

Tacoma, WA

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I dont suffer from mental iIlness, I actually enjoy mine!

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HelicopterMain Discussion › Why does my Trex fly so effortlessly compared to my Raptor
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