View Full Version : Jukka
05-11-2009, 02:50 PM
I do not know how many designer/builder types have seen this design (http://www.saunalahti.fi/jtki1/jtgyrovariations.html) concept, so I am posting links to stimulate ideas and discussion.
I am impressed with Jukka's knowledge as I am many of the old-timers here.
05-11-2009, 04:58 PM
He used to sell plans, but I do not see them offered on his web site anymore
05-11-2009, 05:14 PM
He is perhaps part of the success behind the Magni gyroplanes, as the rights to his JT-5 were sold for that purpose.
05-11-2009, 06:26 PM
The thrust line is the same, not matter where the engine is, it still needs to be close to CLT.
Cierva gyros were mostly CLT or close to it.
Weight in front needs to be balanced with weight behind not by a HS.
05-11-2009, 09:24 PM
I believe Cierva patented CLT.
Ahhhh here it is. Thanks to the guys who posted this before.
05-11-2009, 09:42 PM
Using a conventional airframe with a functioning HS, Cierva not only had the foundation for CLT, but the foundation for "positive stability" The HS could have or did in fact provide/d the down force necessary for positive stability, just as in any conventional design today.
05-11-2009, 09:45 PM
I believe Cierva patented CLT.
Indeed he did, Karl. Somewhere there's the patent drawing from way back then. (I'm sure C.Beaty has one)
It was no coincident. The man knew what he was doing!
05-11-2009, 10:58 PM
When CLT is discussed on the forum it sometimes appears to be a new discovery, but it has been around a long time. When Dr Bensen built his gyro he retained the CLT, or at least close enough for it to be stable. It was only when ppl wanted larger engines and consequently larger props that the thrust line started to move significantly above the CofG.
Sadly a lot of ppl died as a result of this forgotten history.
I often think that we also lost other safety features.
BTW. This is not an attack on the great Mr Bensen just an observation.
Early Gyro's had substantial undercarriage that would absorb landing forces making it more tolerant to misjudged landings. We are only just starting to see aircraft fitted with G-Force landing gear, and I suspect we are all amazed at its performance. Gyro's of course were capable of this feat many years ago.
Likewise early gyro's had a substantial fuselage structure making any accidents more survivable.
All early Gyro's had a large horizontal stab to provide damping and stability.
Early gyro's were very heavy compared to what we see today making them more resistant to turbulance and gusts.
I havn't worked it out yet but I think it possible that by using the teeter rotor to reduce complexity, we may also be losing some of the stabalising forces of a an articulated head.
Almost all of the information we need to build a safe gyro is readily available, all we have to do is learn from history then apply modern materials and standards.
05-12-2009, 12:00 AM
Possibly also due to the fact that in the early days most people had standard designs that had been carefully thought out.
With ultralight and the proliferation of shade tree builders, alterations made without sound aerodynamic knowledge has led to unforeseen problems in thrust line and c of g placement, unfortunate and dangerous flight characteristics.
If this is then compounded with a lack of available training the inevitable happens. Deaths and accident rates go up.
05-12-2009, 08:37 AM
There is a thread on a new spanish made tractor gyro that appeared a few days ago.
It's just a lot more work to build a tractor than most pushers unless you get into the larger, more exotic pushers like the Xenon ect. This is what a lot of builders found out when they started the Little Wing and ended up selling the project.
You are literally building a full aircraft fuselage rather than a skeleton open frame.
I have a set of Jukkas plans which is NOT for sale, but you can buy the plans here:
It is for a pusher, but many of the ideas and parts on the JT5 is used on the other models. (Example: The rotorhead is the same and is also the one found on the Magni.)
If you can get his plans, go for it!
05-13-2009, 04:49 PM
It looks like a nice design, but I would be concerned about the close to 50-50 distribution in front of and behind the rotor. Could make it prone to a flat spin in a steep climb. There is a thread about this somewhere. I'm no expert, just stating what I've read before on the forum.
05-28-2009, 10:03 AM
several people have built and flown his single person tractor, he has photos of one of them on his website.. I'm working with a local high school on building his 2 person tractor design..
06-01-2009, 12:27 AM
[QUOTE=JAL;292909]Why aren't there more tractors? It seems to me they would remove a lot of the thrust line issues. QUOTE]
The biggest difficulty I see for the design of my tractor is the masts and rods command of the rotor in front of the eyes. La Cierva was less concerned about the view and the fun that we are today.
06-01-2009, 01:23 PM
From a few things I have read there may be more drag with the fuselage in the prop wash. I think on a thrust test a pusher configuration will get more thrust than a tractor setup.
06-02-2009, 12:12 AM
I think the tractor is lowest in all aspects. Except visilité.
It allows a large propeller: better thrust.
It allows a better profiling of the rear fuselage: less drag.
The propeller is working in clean air: less noise.
It does not pick up lost: Safer.
The engine protects the driver in the crash.
The HS in the clean propwash can straighten flow: less effect of engine torque.
06-02-2009, 03:43 AM
An example which has been seen at the french "Bensen days" at the end of may.
ŕ Bois De La Pierre.
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