engine on head?

[autogyro]

Hi everybody
Is it a good or bad idea that install engine over head, at the top of mast?
It can make gyro more short, and easy get CLT,right?

Edward

[rwaltman]

Originally Posted by autogyro

Is it a good or bad idea that install engine over head, at the top of mast?

Terribly bad idea. Will increase the risk of power pushovers.
Search for power pushover accidents.

Roberto.

[Master Roda]

Maybe he means an engine for prerotation?

[Rehan K.Janjua]

I would say BAD.

Cause of prop on engine, thrust line center.

NO NO can not even imagine the design or the location.
Short coupled gyro are not very stable.

Or can have engine and prop up front of rotor and tails on the rear of
the rotor. Again many no nos.

[WHY]

Master Roda

I think your point is correct on what he is asking.

Tony

[WHY]

Remember one of the old Bensen pre-rotors with the little O&R 2 stroke on the head ??

Tony

[Early Bird Dave]

Several are flying if he means pre-rotator motors on mast.
Super Mike Hughes...chime in!

[phantom]

I built a gyro with a 60 hp outboard engine on the top of the mast and it had the lower unit/gearcase as a redrive and it worked fine in flight but was top heavy on the ground.

Norm

[autogyro]

Originally Posted by phantom

I built a gyro with a 60 hp outboard engine on the top of the mast and it had the lower unit/gearcase as a redrive and it worked fine in flight but was top heavy on the ground.

Norm

Thanks for above reply.

Hi Norm
do you have images?
do you think it is better or bad than conventional gyro?

Edward

[PW_Plack]

Edward, if you're talking about 60 HP, this is obviously not a prerotator, but the main powerplant. You may be misunderstanding "CLT." You don't achieve it by putting that much mass that high. A thrust line far below the center of gravity has its own set of issues.

Putting a large mass up at the very top also brings issues for blades, hub bars and rotorheads. Most simple gyroplanes depend on flexing of the mast to de-tune the fore-aft vibrations that occure twice per revolution of the rotor. If an engine is mounted where its inertia will resist the freedom of the mast to flex, you'd have to plan another way to accommodate that movement, such as a slider head, or risk cracking other parts.

Maneuverability also calls for getting the major masses as close together as possible to preserve a low moment of inertia. If you hold a pole horizontal with a 10 kG weight at the center, you'll be able to turn and change the direction you're facing fairly easily. Use two 5 kG weights at the tips instead of 10 in the middle, and turning it will take much longer for a given force. The same effect limits some of the maneuvers typically flown by gyro pilots.

Radical departures from the norm can sometimes be progress, but this may not be one of those times!

[Ronnie328]

i don't know about how it would effect maneuvers, but i think being top heavy on the ground would make it more trouble than it's worth. I don't have a gyro, but i'm sure i'd be pretty upset if i accidentally tipped mine over...

[Brent_Brown]

motorhead.....

[autogyro]

Originally Posted by PW_Plack

Edward, if you're talking about 60 HP, this is obviously not a prerotator, but the main powerplant. You may be misunderstanding "CLT." You don't achieve it by putting that much mass that high. A thrust line far below the center of gravity has its own set of issues.

Putting a large mass up at the very top also brings issues for blades, hub bars and rotorheads. Most simple gyroplanes depend on flexing of the mast to de-tune the fore-aft vibrations that occure twice per revolution of the rotor. If an engine is mounted where its inertia will resist the freedom of the mast to flex, you'd have to plan another way to accommodate that movement, such as a slider head, or risk cracking other parts.

Maneuverability also calls for getting the major masses as close together as possible to preserve a low moment of inertia. If you hold a pole horizontal with a 10 kG weight at the center, you'll be able to turn and change the direction you're facing fairly easily. Use two 5 kG weights at the tips instead of 10 in the middle, and turning it will take much longer for a given force. The same effect limits some of the maneuvers typically flown by gyro pilots.

Radical departures from the norm can sometimes be progress, but this may not be one of those times!

Thank you Paul, thank for eveybody who answered me !
I get more clear about it from your explain.
Edward