I recently acquired a pristine example of one of the "Early Birds" of the model helicopter world. A Kavan Jet Ranger.
Click any image for larger view !
The Jet Ranger without the links to the head, but otherwise as I collected it.
This heli had been hanging in the office of a friend of mine since it was completed in 1975. It was never flown, although it had been run at some time, and the fuel used to run it was castor oil based L
I've lusted after it for as long as I've known of its existence and having owned one in the past I felt I could now do it justice, seeing as I can now fly, whereas could barely hover when I owned my previous one. After mentioning my desire to own this machine, my friend offered it to me on two conditions that I readily agreed to. One, that I actually flew it and the other being that I kept it. No problem with either as I was more than happy to fly it and compare it to the modern machines of today, and it's such a good looking machine, I'd be happy to see it around for a long time. Maybe another 25 or more years J
Before I even considered flying it, I needed to do the usual thing of making sure it wouldn't fall apart after sitting doing nothing for 25 years. Age and glue don't mix well, particularly if the wood has come into contact with fuel and this helicopter, being a monocoque design, relies heavily (totally) on wooden formers glued into a fibreglass fuselage. Everything sits on wood, so everything had to be removed first.
View into the "firehole" showing the engine bearer plate and tail rotor/main rotor transmission gearbox. Also visible is the Super Tigre engine and the custom built aluminium box silencer, plus the bottom main shaft bearing
The heli, as expected, had suffered some ageing in the glue joints and a lot of discolouration in the metalwork, particularly the brass parts that are common to this machine. The tail rotor hub for example looked like a chunk of bronze instead of shiny brass, and the main rotor shaft was close to a natural rust colour, caused by the old castor oil residue. This was soon fixed with a little elbow grease though (and a tube of Autosol cleaner)
Tail rotor hub after cleaning, plus blades and blade holders. Very close in looks to the real thing
I stripped everything down to it's component parts, examined then cleaned and re-greased all the bearings, so I wasn't concerned about things not turning smoothly when the day dawned.
The rotor head has a total of 4 (yes FOUR) ball bearings, so lots of oil needs to be used on the other metal to metal surfaces to help control the wear and reduce the chances of radio "noise" These inclued the fly-bar cradle, the fly-bar feathering axis, the Bell/Hiller mixers and the scissor arm mixer. I have a fly-barless head for it too, which I intend fitting at a later stage, but for now I want the heli built close to its original configuration, although some things will be changed or added.. The changes I've made at present include an update in the radio department, where I've fitted a (still quite old) JR Apex 7 channel non-computer radio with standard Futaba 3001 servo's throughout apart from the collective servo which is a Futaba 9201 coreless motor, and a Hitech servo controlling the tail.
Fitting this radio has allowed me the flexibility of adjusting pitch and throttle independently much more quickly and easily than with the original mechanical mixers supplied by Kavan, plus having the ability to adjust the revo mix electronically. I've also fitted a gyro, in the form of a Futaba 153BB electro/mechanical and not a piezo. The control system is mechanical CCPM and is "almost" standard. I've now angled the CCPM servo's to allow the push rods to follow a better "line" which has allowed me to expand the pitch range slightly, without running into binding problems.
Underside view of cabin top showing the control layout and the massive main gear.
Side view of same cabin top showing routing of control push rods and the "kinked" servo tray giving a downwards slope to the servo's. The wires exiting the front of the servo tray are for gyro and battery connection. The Rx is buried inside the cabin top.
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