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Resurrecting a 1975 Kavan Jet Ranger

Beavis 2000 

I recently acquired a pristine example of one of the "Early Birds" of the model helicopter world. A Kavan Jet Ranger.

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 I could barely hover when I owned my previous one. After mentioning my desire to owner 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 include the fly-bar cradle, the fly-bar feathering axis, the Bell/Hiller mixers and the scissor arm mixer. I have a flybarless 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.

The blades are the original blades supplied with the kit, as are the tail blades. All wood and all in perfect condition, so these are the blades that will be used for flying, with two small modifications. Buried in the roots of the main blades are two "tongues" designed to hold the blades in one position.

Original blades complete with the dreaded "Tongues of Death". These won't be fitted when the heli next flies

Remember this heli was designed in the days when it was considered essential that the blades were locked in their flying position, unlike today where "free-swinging" blades are the norm. The problem with leaving the tongues in place is that it's these tongues that hold the blades in place (in lead/lag), and the tongues also act as excellent "log-splitters" if the blades ever come into contact with a solid object (like the ground or a leg). I think it's probably best to remove the tongues

I'm also going to add some weight to the blades to compliment the newly incorporated autorotation unit (cannibalised from a Kalt Cyclone) Again, in the days when this helicopter was sold, autorotation's were a dream and not a reality, so no auto units were available. The latest (and last) of the Kavan line of helicopters DID have an auto unit, but that was confined to the Lockheed 286L. As far as I'm aware, there was never an auto unit included with the Jet Ranger. Not so with this one.

A close up of the newly incorporated Kalt Cyclone autorotation unit. A must with a helicopter where parts are hard to find

The engine department will be "painted" with fibre-glass resin to stop any oil/fuel from getting to the woodwork and the engine I'll be using is the original Super Tigre 61 coupled to a "Dustbin" type of silencer exiting from underneath. No tuned pipe for the time being. All standard stuff.

Another view into the "Firehole" showing the engine arrangement. The green wires seen in the top left corner are for the running/navigation lights that are fitted

The tail rotor gearbox on these machines is a little different to those seen these days as everything is "open". No closed box affair so any grease that's applied tends to get thrown off after a while, so not only do you need to keep an eye on the gears and bearings, but you also have to periodically clean the inside of the tail boom, as it gets sprayed with grease. Not a big problem, but it's mucky as hell. L

No ball raced pitch slider either, simply a brass tube running inside another brass tube, so oil is needed at each flying session if wear is to be kept under control.

Open gearbox and a very simple control run. No ball raced ANYTHING (other than the shafts in the g/box) and note the "oiling" hole in the pitch slider. To ignore it is to lose it!

The paintwork on the Jet Ranger is very well done, but unfortunately it's not fuel proof paint and at the moment it's a little "boring" to look at. I intend re-doing the scheme eventually, but I'll leave that 'til a later date. At present and from various angles, it looks like this:-

A very scale looking helicopter, not to mention a large and heavy one. Over 5 feet long and weighing in at 14lbs. Almost too nice to fly, but only almost :-)

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