T-Rex 450 5 Blade Rotor vs Motor/ESC ? ...

[RChristopher]

I am thinking of adding another 450SE nV2 to my fleet, as the core of a scale project. In this I am considering a 5 blade rotor and Helitronix Mixing system. As I ponder the details, questions regarding the main blades come up. It appears that most are using the same size blade for a 5 blade head as on a 2 blade head. Is this correct? If so, is a more powerful motor/ESC required? Special blades ... ? What is the best way to approach this to make sure I am not overloading the motor/ESC?

Regards

Bob C.

[crazyerick]

I'm interested in this one too but more for how to make it work? Many say you will need another gyro or two for stability but I can't seem to find any documentation where to start a project like this.

[rgallant]

They are way fun, and no there is very little good info on these.

I am working in a Lightning 4 blade head for my Blackhawk and I can give you a few tips and will update this as I go along.

1st and foremost your heli should fly well with a 2 blade setup.

My birds specs


TX Airtronics RD8000
RX Hitec Electron 6
Phoenix 35 ESC
Align 430 BL
Align 325 Pro Blades x 4
Thunder power 2020mah battery
401 gyro and Futaba 9650 gyro.
T-Rex 450 SE


Note I am avoiding extra gyros and mixers.

There are basically 3 ways to setup multi blade heads

1) Use a 4 blade head with a mechanical phasing block for adjustment

2) Use an electronic mixer, or mix via TX settings if possible

3) Use a combination of 1 or 2 from above and gyros on the main rotor.

With any of these solution your heli WILL fly differently from a flybar based head. The reason as far as I can make out from the 40 or sites I have have gone to, is that when you apply input to a flybar based head system a portion of the input goes to main blades and a portion goes to the flybar. This helps to dampen the control inputs as I understand it. (please feel free to correct me if I am wrong here).

When you take out the dampening you get much more responsive (twitchy) cyclic. For this reason a lot of people who fly multi blade heads seem to crank up the expo, over 40% in come cases. As you are going to fly scale this is not too bad.

On to the fun bits.

Warning, if you are new to Heli's stay far away from this item, it is cool and looks nice, but is very difficult to setup. It comes with exactly zero documentation, so a lot of internet research is required.

Ok that dispenses with the warning. Mine as it came out of the packaging appears be setup for counterclockwise rotation with the balls on the blade grips leading. A quick bit of monkeying got things more or less setup, this includes:


Re-leveling the Swashplate
Note that the only way to adjust pitch is to adjust the whole swashplate for large amounts, the links connecting the head to the swash have some adjustment but use them to fine tune.
Insuring that the phasing block moves freely through the entire range on swashplate movement.
Checking that with one set of blades set for and aft, they do not move during elevator movements this is very important
Make sure all the blades have the same amount of pitch.


Now for the pics

As is was delivered the entire contents.

http://www.gallantent.com/helo/blackhawk/4blade001.jpg

If your pitch links look like this your phasing block is setup very wrong.

http://www.gallantent.com/helo/blackhawk/4blade004.jpg

Installed on the bird, and ready for testing.

http://www.gallantent.com/helo/blackhawk/4blade008.jpg


Ok, this 1st image show 2 things of importance, the angle of the links connecting the blade grips to the swashplate, and the the phasing block. The phasing block is the piece attached to the main shaft, and is in line with the rear servo link and anti-rotation guide.(in the second image) It is critical that the phasing block have that 90 degree angle at mid stick. If it does not, it will bind and you can and will destroy servos.

http://www.gallantent.com/helo/4blade/4blade009.jpg

This is how I set my head up to remove the movement in the blades when they are fore and aft. Notice the difference from image one. The links are almost 90 degrees rather than 45. According to all my research there should be no movement in the rotor blades that are in line with the nose and boom when applying forward cyclic. The video below shows the movement. This is not ideal and I have to do some more testing yet.

http://www.gallantent.com/helo/4blade/4blade011.jpg

Video - the very short video below shows the movement in the both sets of blades. The 1st part of the video shows the movement when the I apply forward cyclic, watch the blades that are in line with the tail and nose. The second half shows the effect when I apply left and right cyclic.

Here is a direct download link, please right click and save as it is about 35 MB

Rotor blade Movement (http://www.gallantent.com/helo/4blade/4blade010.avi)

And the YouTube option

http://www.youtube.com/watch?v=zgTc0bFBTeA

Flight performance with the head setup in image 2 is very exciting, the heli has a pronounced tendency to roll left as she gets light on the skids. Thankfully I have moss in the front yard and only about 55% throttle as she tries to lift. (saved my blades) I will post video before I make any adjustments. The other interesting thing is I need to apply left stick, yes left, to correct the problem. Which leads me to believe that my phasing is incorrect. I did get in the air if 1 foot counts and get back down in 1 piece but it was interesting.

With a few tweaks I got a whole 3 feet up in the air and more less stable, there is still a pronounced tendency to roll left until I am up in the air and as I spool down to land. I am working on tweaking this out. With the bad weather on the West coast, I am working on a test rig to let me test things with breaking things (and tearing up carpet).

Back to ground testing while I figure this out, I will post more video and images as I go along. This is an interesting head but very odd to setup.

[rgallant]

Just a quick note, as I thought I had the phasing going the wrong way, simple test to tell up to speed at 0 degrees pitch. Watch the rotor disk and give a tiny bit of forward stick, if the rotor disk tilts backward you have the wrong phasing going the wrong way.

Only cost me a bent pitch link to figure it out.

[Rodan]

I have the above 'Lightning Heli' four-blader as well....

From what I have been able to learn, both of your photos above have incorrect phasing. The input should lead the blade by 90 degrees. Assuming you are using the stock rotation (clockwise viewed from above) on the TRex, in the first image your input is at 0 degrees, and in the second image at 45 degrees. Remember that the pitch link is already leading the blade by 45 degrees.

Try advancing the swash another 45 degrees, and I think you will find it flies a lot better.

The biggest problem I had with this head is that the swash follower that comes with it binds, and won't allow enough positive pitch. I was only able to get around 8 degrees positive pitch. The only way to solve it I could see was lengthening the already very long pitch links. Instead, I pulled the swash follower off the Lightning 3 blade head I was playing with before getting the four blader. It fits, and allows full positive pitch.

The multis also seem to like a slower headspeed (more mass), but you will run into a problem with tail authority below 2k headspeed, where the tail can't counter the torque with the heavier disc. I have been looking for one of the older tail driven gears to speed up the tail, but haven't found the right part yet...

They are definitely more squirelly than the flybar head. I'm currently flying mine without any additional gyros or mixers. I tried expo, but didn't like that, either.

[rgallant]

Hi,

Thanks for the input Rodan, I found that if I got the follower to exactly 90 at 50% throttle the binding went away. It is nice to have someone confirm what I figured out the hard way, but that is the thing about new toys you are going to have some issues.

I just need to get everything feeling right, I have read the notes about the headspeed, slower would be better. Maybe when I get the 4 blade tail sorted that will help.

[Rodan]

Here's a couple of shots of mine. This phasing flies pretty well, and cyclic inputs result in the correct motion...

[rex-n-effect]

I have been looking for one of the older tail driven gears to speed up the tail, but haven't found the right part yet...


What parts do need?

[Rodan]

I have heard that the older TRex 450s had a different gear ratio for the tail, and the newer ones slow the tail down so it doesn't self destruct with the higher headspeeds being run these days. I have yet to find a part that has a different number of teeth on the gear than the current parts...??

[Ginvent]

How are the autorotative tendencys with more blades. I would assumes autos are easier

[slider46]

You need to look for the white gear sets and tail gear set from the 450XL and very early 450SE.. They were Faster tails... Any of the light blue or dark blue gear sets will be for slowing the tail down with higher headspeed. I am very interested in how this goes as I want to put a 5 blade head on my 500E this winter... That should be interesting...