Pre-Rotator on the Dom

[gyro-3xio]

I just read a very interesting article on the Dominator that was written by Ken Armstrong.

He went to RFD to meet with Mr. Boyette for this article.

What I am curious about is the pre-rotator on the Dom.
It is apparently hydraulicly driven from the engine vs other gyros that use a flex cable.

Is this a more efficient way to go? I.e. less parts, or less weight over all to the machine? Less maintenance?

Can you get better RRPM out of this type of system vs a flex shaft when spooling up?

Thank-you in advance.

Jim.

PS. A Soob on a Dominator? This is starting to sound interesting!!!!

[MikeBoyette]

Jim,
The main reason for a hydraulic unit is it's abilty to make it fit the application. You can't make a cable drive go around corners. The hydro unit weighs more and is used on anything bigger than a 582. The RRPM you get out of it depends on the size disk and engine. He used to have a 618 powered single place with24' blades and a hyro unit and he could get them up to 300 rpm's. A two place with 27's you could probably get 240 to 250.

[13brv3]

Can't wait to find out what a 582 with 23' blades will get with the hydraulic unit :D

Rusty

[MikeBoyette]

Rusty,
The key to good performance is keeping the belt free from any oil. It is also important to use corn starch on the drum and belt when first breaking the belt in.

[Timchick]

Jim,
What magazine was the article in?

[scottessex]

Can't wait to find out what a 582 with 23' blades will get with the hydraulic unit

About 230 RRPM , but it wears the wheel out faster, about 180-190 is plenty for short field takeoff. :)

At least that is what I have seen with my 582 dom with the flex cable.

[13brv3]

Hey Scott,

What wheel are you talking about? Do you have the mechanical pre-rotator? I've got the hydraulic unit, so hopefully it will do better than 230 :)

Mike,

I'll make sure and pick up (steal from the kitchen) some cornstarch for the belt. BTW, does the belt need to be tight when engaged, or just snug?

Thanks,
Rusty

[gyro-3xio]

Hi Tim,

It was in the January 2007 issue of COPA.
(Our version of AOPA.)

Did you get lots of good pics and video from BD this year?
I'm looking for another DVD if you are close to releasing another one.

Back to the hydraulic pre-rotator,
From the article, I am under the impression this unit was mounted on a Subaru.
How much hp would one need to get it up to 400 rpm?
Why?
Just thinking of the other thread re: JTO.

I am also guessing this unit is fairly low maintenance. Would that be correct? (Well less maintenance than a flex shaft.)

Jim.

[Fl90]

If your trying to prerotate DW's of any length to 400rrpm, you'd better be building a heli.

Phil.

[StanFoster]

Mike: What will the hydro unit spin up 30 foot Sportcopters to? Just curious....


Stan

[GyroRon]

Hey Scott,

What wheel are you talking about? Do you have the mechanical pre-rotator? I've got the hydraulic unit, so hopefully it will do better than 230 :)

Mike,

I'll make sure and pick up (steal from the kitchen) some cornstarch for the belt. BTW, does the belt need to be tight when engaged, or just snug?

Thanks,
Rusty


It won't. You will get about the same, and that is somewhat pushing it to get 230.... I have seen the highest RRPM's with the cable drive prerotators Ernie uses on the Ultrawhite dominators - 260 to 270 max.

[MikeBoyette]

Mike: What will the hydro unit spin up 30 foot Sportcopters to? Just curious....


Stan
Stan,
I am not sure. I don't think he's ever used it on anything bigger than 28' DW's. I'll ask though. As for obtaining 400 rpm's there is only one system I know that can do that and it is a Dick DeGraw design.

[TomCarlisle]

The limiting factor is primarily the brakes. If you could shift the prop to 0 pitch you could probably get 400 rrpm. I stop at 200 because the hydralic oil gets hot if you keep it engaged too long and 200 is plenty to prevent flapping. My Doms nose comes up at 263 rrpm and lift off is around 300. Lower the nose and it goes to flight rrpm too quickly to count. Stay about 3 feet altitude until 60 mph indicated and then climb out at 60. Works for me at Gallup where altitude of the airport is 6510 MSL and density altitudes get as high as 10,000. My Dom flies very well with the 65HP Hirth.