I need some help please

Welder

Newbie
Joined
Aug 11, 2019
Messages
33
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.
 

Brian Jackson

Platinum Member
Joined
Jul 17, 2004
Messages
2,906
Location
Hamburg, New Jersey USA
Aircraft
GyroBee Variant - Under Construction
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?
 

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,736
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
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.
 

Welder

Newbie
Joined
Aug 11, 2019
Messages
33
Location
Grand Rivers, Ky
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.
 

Welder

Newbie
Joined
Aug 11, 2019
Messages
33
Location
Grand Rivers, Ky
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.
 
Last edited:

Vance

Gyroplane CFI
Joined
Oct 30, 2003
Messages
15,736
Location
Nipomo,California
Aircraft
Givens Predator
Total Flight Time
2200+ in rotorcraft
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.
 

giro5

Senior Member
Joined
Mar 19, 2006
Messages
1,139
Location
Farmington, New Mexico
Aircraft
prev- citabria,AA1b, fun racer
Total Flight Time
400 GA, 50 trike
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
 
Top