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scottessex
03-06-2008, 11:59 AM
Does anyone fly the Jukka Tervamaki tractor designs?
I found a picture of this one, but that is about it.
joe nelson
03-07-2008, 10:17 AM
Scott,

I've always thought that these where cool looking and never understood why they never were successful. Some of them reminded me of early Pitcairn's with the engine mounted in the aft part of the airframe with a drive shaft forward to the prop mounted in front. Maybe, their complexity in construction did them in.
scottessex
03-07-2008, 10:41 AM
I don't think he sells plans is the biggest problem, A really neat tricycle design. I would love to see one.
glider
03-10-2008, 02:57 AM
Scott,

I've always thought that these where cool looking and never understood why they never were successful. Some of them reminded me of early Kellets with the engine mounted in the aft part of the airframe with a drive shaft forward to the prop mounted in front. Maybe, their complexity in construction did them in.


Hello, we are just building a very similar one, but with rear engine and tractor propeller.
Ciao
Pierre
joe nelson
03-11-2008, 11:45 AM
Ciao Pierre,

Can you tell us about it? The early Pitcairn AC-35 is my favorite with the rear engine and tractor prop. It had jump take off ability which many of the pilots here would like to have. The JT's look like they would be great performers but you don't see them here in the US.

I think the welded airframes is too involved for the average gyro builder here. They would prefer to bolt it together and go fly. Addio amico!
DanielM
03-11-2008, 12:06 PM
Scott,
Maybe, their complexity in construction did them in.

We are a lazy bunch aren't we.:D
NoWingsAttached
03-11-2008, 01:00 PM
Whoa, now THAT's a cool concept...rear engine, front prop!!!
NoWingsAttached
03-11-2008, 01:09 PM
Hey, Danny boy, you coming to Bensen Days? And if you are, are you gonna bring that Bee?
Passin' Thru
03-11-2008, 01:37 PM
Whoa, now THAT's a cool concept...rear engine, front prop!!!

Check this!
scottessex
03-11-2008, 02:00 PM
Could you use an aluminum car driveshaft? What about the resonance?

I think all of Jukka's designs are great.
joe nelson
03-11-2008, 05:04 PM
Scott,

I think it might work but you might add some pillar block bearings to reduce the shaft from moving around. Some off-road shops will build drive shafts for you if you have the dimentions....a little pricey though. My only concern is the additional weight from the pru/pru mounts and drive shaft in addition to the engine weight.

Pitcairn built a few aircraft in this configuation in the late'30's and early '40's. They were able to do JTO's and were probably the most advanced of the time before helicopters "BC" (before copters).

A JT-9 with a big Rotax might do the trick! It would be a great way to spend a weekend boring holes though the air!
WHY
03-11-2008, 06:27 PM
Molt Taylor (of EAA fame) used this concept on the "Teal" and had pure hell with torsional resonance in the shaft that went from the engine to the propellor, also this concept was tried in the BD-5 with results likewise. For those not familiar with these craft , they were both pusher style fixed wing, with the BD-5 using a reduction unit on the engine.

This is a great idea but apparently with a lot of gremlins to be fixed.

Tony

Tony
dinoa
03-12-2008, 12:47 AM
Look at Jukka's considerations regarding torsional resonance

http://www.icon.fi/~jtki/jt11virtual.html

about half way down the page "JT-11 Power Train"


Dino
Athens, Greece
joe nelson
03-12-2008, 06:01 AM
Here's Joe's guess on a fix for the resonnance. The rear engine driving a hydraulic pump/pumps fed by pipes to a hydraulic motor mounted to the forward firewall. The motor would drive the prop with torque only from the engine and prop with no drive shaft. This system could also drive a prerotator with some modification.
scottessex
03-12-2008, 06:42 AM
Good idae, except for the weight, A hyd pump and hyd motor to drive the prop, would probably weigh what the engine does.

How about a clutch disc on the flywheel, Belt reduction, and a couple of U-joints just like a car, that way you would allow for airframe flex etc.

Or would it be better to just hang the engine on the front, and be done with it?
WHY
03-12-2008, 09:21 AM
Hi Dino

The Flexidyne coupler is exactlly what Molt found to do the most good on his arrangement, reading the rest of Jukka's comment on resonance sounds like he has figured it out to satidfaction.

Met Jukka at the Hofstra University conference on the Autigiro, held in New York some years ago. The man is a absolutely amazing genius.

Tony
WHY
03-12-2008, 09:26 AM
BTW, looking at the one flying in the picture, looks like it has a small two stroke mounted in front. Still a great looking machine.

Tony
WHY
03-12-2008, 09:31 AM
Can you see this in a molded composite fuselage kit, with hard points for the landing gear, motor mount and rotor pylon, it would be a "just add water and stir" and POOF! you have a gyro.

Tony
dinoa
03-12-2008, 11:30 AM
Tony,

My interest was sparked with Jukka's link to the Stemme S-10 powertrain

http://www.icon.fi/~jtki/jt11/Stemme.jpg

A motorglider that is more complex than many helicopters.

Dino
glider
03-13-2008, 05:44 AM
Ciao Pierre,

Can you tell us about it? The early Pitcairn AC-35 is my favorite with the rear engine and tractor prop. It had jump take off ability which many of the pilots here would like to have. The JT's look like they would be great performers but you don't see them here in the US.

I think the welded airframes is too involved for the average gyro builder here. They would prefer to bolt it together and go fly. Addio amico!


Hello,
Our design on first was made for a two seater side by side rear-engine front-prop architecture but, before starting to build, we did prefer riduce the risk of new concept and so we did convert it to a monoplace with same characteristics.
After tests, if positive, we will begin the second design. Soon will follow pictures.
Ciao
Pierre