I need some help please

Welder

Active Member
Joined
Aug 11, 2019
Messages
100
Location
Grand Rivers, Ky
I have been looking at the JT-9 Autogyro and would really like to build one. Jukka has the design powered by a HKS700. I would like to use a different engine. I want to build it like it was designed HP wise. (64hp).
So I found a couple of engines but are heavier than the HKS. Center of Gravity is my concern.
How can I build this tractor style gyro, and have it fly safely?
I don't have a firm grasp on the CofG.
Thank you in advance for any response or suggested study on the matter.
 
I have the JT-5 plans from the PRA site (members area I believe). Though I haven't seen the JT-9, if they're drawn similar to the 5, the COG is shown as a target symbol in the first sheet side view. There's no dimension given, however I can pull the PDF into Rhino as vector geometry to scale and take a measurement in the CAD file. Assuming it is shown in the designed nominal location. Could I be of any help to you that way?
 
In my opinion it is easy to adjust for a different horizontal center of gravity in a gyroplane by moving the rotor head and landing gear to compensate.

I feel a different vertical cg is more of a challenge to adjust for.

Weight is the enemy of flight so in my opinion any increased weight should have a tangible benefit.
 
Thanks guys,
I will Email Jukka, and inquire about the desired CofG target for the JT-9 and the JT-9T. He has 3 view drawings on his website, under the virtual aircraft heading. Jukka has been faithful to respond to my earlier questions about the JT-5.
I am looking at the Toyota 1KR and Mercedes smart for two, both 3 cyl gas engines, both of which have been successfully converted for fixed wing use.
I will get back to this post after Jukka weighs in.
 
Jukka responded. His designs should hang fully loaded 5 to 10 deg. nose down when fully loaded (pilot and fuel). Knowing this fact will allow me to perform a final weight and balance before flight, but not really help in the choice of engines. I will give it some thought.
Vance, the HKS700 costs too much for my wife pocketbook, I believe I could come out cheaper with one of the 3cyl. I am considering. Maybe the Trainer JT-9T would be a better choice.
Brian, no target given for the JT-9 or JT-9T, so all I have to go by is the dimensioned 3 view.
 
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Vance, the HKS700 costs too much for my wife pocketbook, I believe I could come out cheaper with one of the 3cyl. I am considering. Maybe the Trainer JT-9T would be a better choice.

I have yet to see a conversion engine work without a lot of debugging.

In my experience by the time I got the bugs worked out; an auto conversion is nearly as expensive as a used engine designed to power an aircraft.

Most of the experimental amateur built aircraft I have inspected are weak on wiring.

Most conversion engines are battery dependent.

In my opinion if an engine won’t run without the battery it doesn’t belong on an aircraft.

My first engine out at night was a Subaru EJ25 powered Gyroplane.

As good as gyroplanes are with an engine landing out compared to fixed wing aircraft in my opinion a successful engine out landing in a gyroplane has a lot of luck involved.

It is my observation an aircraft engine will increase the resale value.
 
I kinda agree with Vance in that an aircraft engine is a good choice but these links have another option.
I can't find it now but the Great Plains site used to have a paragraph that indicated with the 1.6 reduction and a 72 in prop you could get about 300 lbs of thrust. with the 2.0 reduction with a 74 in prop they indicated you could get about 400 lbs of thrust. you can get an assembled engine from hummel for about the same price as a kit from Great Plains.


http://www.greatplainsas.com/reduction.html

https://www.hummelengines.com/price-list
 
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