FLYMIKE

At the park today someone said I must have been 90 miles an hour. For the size of these things it really looks like its going faster than it really is. I was wondering if anyone has clocked air speed. Or how can that be done. Mike

jet22b

Good question, Mike!!
I have a frend who is a local cop. The next time I go to fly my 450SE, I am going to ask if he could meet me at the park with his speed gun and see if he can clock the helicopter. Today I was out flying the 450SE and was shock how fast it is. Took-off, had it in a 2 foot hover, add a little forward stick and I was across the park before I knew it!!! WOW!!! I will let you know the outcome od the speed test!!

Sonny

FLYMIKE

Yah, mines pretty fast too. I started a topic on this at helifreak too and someone said it cant go any faster than 35 on a down line. Let me know what happens. Mike

BarracudaHockey

My Feedback: (11)

Its not 90 mph I can promise you that. I was running a radar gun at a fun fly and a delta plane built for speed coming out of a dive was doing 120 ish, the 90 mph passes looked MUCH faster than even my 90 nitro does.

If you have a small gps tie wrap it on and set the trip computer to show fastest speed, thats what we do with the nitros when people start talking smack and the radar gun isn't around.

emosolo

Morning,

I did an experiment in reflex xtr, the fastest I could make the chopper go was around 70KM/H, but that was a Raptor 50. I thought it would be alot quicker than that, but I think the idea using the GPS is a very clever idea... I've got one that is pretty small and attaches to my bicycle... Gonna check the speed out n let you guys know...

Regards,
Solo.

joe tower

The GPS works great.....When attached to a on road nitro car it stops the "it's doing 90 mph" conversations quickly. Just be sure to balance the CG.

FLYMIKE

Someone on another sight states that he was up to 48mhp with his trex , clocked with radar gun.

BarracudaHockey

My Feedback: (11)

48 I can believe.

jet22b

Okay the numbers are in. I met with my friend today and he had one of his friend that work for the state. The first pass was on the line of sight. Hand held radar gun. Clock at 48 mph. The next pass, line of sight hand held Laser gun. Clock at 49 mph. The winds was out of the north at 1 mph. Both pass was in the wind.

Sonny

Crash Bandicoot

I heard a TRex600 won this years heli drag racing event beating out a super light weight modded Raptor 90SE with pumped OS91 engine.
No other heli at the event could beat the TRex600. Stock motor, Stock gears.........BAD A**

I guess life begins at +14 -14 blade pitch

drtmind01

make can do 7 miles per hour,,, with no stick input lol, i havent flown really fast but i could and the amximun i have flown is 20 mph but i could go way faster.

endeavor_635650

A few months back, AMA's model aviation had a little article on the speed record for an rc heli. I believe it was just shy of 75 mph. So definately no more "its doing 90" stories can be believed!

chopperdudes

check this out... http://www.littlerotors.com/articles...802/index.aspx... wonder if this is true...

kayabaliki

This is my first posting and I appologise if I sound like "Mr.who knows everything".
I am not and my whole purpose is to join the discussion, contribute all I can and learn from you and your experiences.

I would like to share something that I found out due to my interest on helicopters rather than rc helis.

There is a limit called max.safe speed for rotary wing aircraft. I will try to explain it as far as I can and I think it will help a little to the discussion here and maybe add some dissappointment.

The propeller, the main rotor in a heli, creates propulsion with its wings travelling a distance.
In hover state, the distance which the tip of the main rotor travels an hour can be calculated by

rpm(of the rotor = 2000) X 2 X Phi(phissagor = 3.14) X rotor raddius(= 32.25 cm) X 60(60 min = an hour) = roughly 243km/h = 135 mph

from head to tail, rotor travel half distance so 67.5mph.

When you start moving your heli ahead with 10 mph, assuming your heli's rotor rotates cw, the tip of the rotor travels 67.5 + 10 = 77.5 mph when it travels from tail to head(left side of your heli) and 67.5 - 10 = 57.5mph on the other side.

This creates extra lift on the left and less on the right so you have to compansate by puttingthe ail a bit to the left.

When you reach somewhere around 30 mph the lift difference between left side and right reaches to a level that you can not anymore compansate by the left ail.

Let's assume you trimmed the heli that you can still compansate. Even in that case there is no way you can speed further than your heli's half rotary speed. In my case it is 67.5 mph. I believe my limit is far less than that, something like 30 mph.

Now you have the formula. The bigger the rotor(the blade), the higher the rpm equals higher half rotary speed, which means higher theoratical speed limit. But please don't forget that heli is allot more complicated than that.

Anyways, I also made the same calculation for the "trex 450 xl-sp" simulation model that I use for reflex xtr simulator.

Its rotor is 1.35 m long , its rotor rpm is 1500 and I end up with 106 mph half rotary speed.

I believe It can not safely and properly fly above 50 mph, since the difference of rotary speed between left and right would be more than 100 mph.

But this is my opinion and I must say that I am used to be surprised with what I can not imagine.

Please feel free to comment or critisize.

Thanks in advance..

Karyn

Those formulae almost hold true for full size helis when the fuse is kept relatively level for pilot/passenger comfort. However the scale strength of model heli blades, and the fact that there are no living occupants inside to scare the S*&% out of, means that forward speed can be increased by pointing the heli nose straight down and using nearly all the thrust to push the heli forwards.

The limiting factor then becomes the same as a fixed wing aircraft propellor, ie, how much air can you force through the rotor disk. You will always loose out to an equivalent fixed wing craft as you must use some of the thrust to maintain altitude. Stub wings don't really help us as pointing the nose down negates their effect and they would simply be another source of drag.


The problem for full size helis though is not increased lift on the leading blade, zero pitch is easy. The problem is with the trailing blade stalling as the airspeed over it decreases.

NVSFlyer

Your both correct in different ways...On a real helicopter what has been done over the years is to slow down the rotor IE going from the UH-1 to the AH-64 the rotor speed is down 30 RPM's at around 292 rpms. The retreating blade stalling is the main problem with going any faster due to the requirment to produce equal lift as the other side. In saying this as you said Karyn if you zero out the leading blade you loose air speed. As you pointed out Karyn you can put the heli on edge but you change the angle of attack on the rotor system and stall them once again because of you have to large of an amount of pitch. You turn it into an egg beater rather then a lift producing system, this is what happens when you do full pitch climb outs you bog the motor (Real life we call it Rotor Droop). I'm not a guru by any means but I've been working on Helicopters for over 16 years now and it sure is fun getting school'd by some of the engineers. As one of the guys just said that the reason why our RC Heli doesn't go faster is because of the lack of a horizontal stab. If we were able to keep the tail down and make the rotors pull the aircraft forward rather then put it on edge it would go faster.