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Nick_Karatzides

1/18 scale Hafner Rotabuggy flying Jeep Willys RAF

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1/18 scale Hafner Rotabuggy flying Jeep Willys RAF

Solido diecast conversion & scratchbuild

 

The Hafner Rotabuggy (formally known as the Blitz Buggy or Malcolm Rotaplane) was an experimental aircraft that was essentially a jeep (actually a Willys MB) combined with an autogyro. It was designed by Austrian born British designer Raul Hafner of the AFEE - Airborne Forces Experimental Establishment after their development of the Hafner Rotachute enjoyed some success. The prototype was built by the M.L. Aviation Company at White Waltham in 1942.

 

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One of several failed concepts for the equipping airborne forces, the effort and risk in getting the Rotabuggy into battle would probably have outweighed its utility

 

Initial testing showed that a Willys MB could be dropped from heights up to 2.35 metres (7.7 ft) without damage to the vehicle. A 12.4 metres (40.7 ft) diameter rotor was attached, along with a tail fairing and fins, but no rudders. The design work was carried out by AFEE staff, while most of the construction was undertaken by R. Malcolm Ltd, with H. Morris & Sons assisting in the manufacture of the rubber hub. The serial numbers RD123 and RD127 were allotted for the two Malcolm Blitz Buggys, although they were never to be used. The basic Jeep was fitted with a pylon to support the two-bladed rotor and a fairing to carry the tail surfaces. The Hafner Rotabuggy, as it became known, was to carry a pilot and a small load, together with a complete tankage of fuel and spare wheel, spare tank, tools and snow chains. The pilot occupied the starboard front seat, but an alternative arrangement for a second pilot was made in the port seat with dual controls. The tail fairing was a plywood monocoque structure attached at four points to the rear of the Jeep and cabin. Because consideration loads were transmitted through the fairing in some conditions of flight and in heavy landing, the Jeep was strengthened locally at the points of attachment. The twin-spar tailplane had trimming flaps on either side which were adjustable on the ground by means of turnbuckles. Large endplate fins were set at a slight angle in plain view to give incidence relative to the local airflow. Replacing the standard Jeep windscreen was a streamlined sheet metal framework with perspex sheets. The remainder of the cabin was built of plywood. Access doors with large perspex panels were fitted both sides. A hole in the cabin roof accommodated the pylon, with allowances for movement owing to the elastic suspension. In the cockpit a special dashboard on the starboard side contained an airspeed indicator, a rotor speed indicator, a sensitive altimeter and a turnand- slip indicator. A standard telephone system via the towrope allowed the pilot to communicate with the tug pilot, the amplifier and batteries being located behind the starboard seat. The Hafner Rotabuggy, camouflaged, carrying RAF roundels and a prototype "P".

 

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To test the performance of the rotor, it was mounted on a pylon attached to a Diamond Τ lorry, which was heavy enough to resist overturning when acted upon by the lift of the rotor. To start the rotor the lorry was driven forward slowly into wind while a number of men pulled on the starting cable at the rear. About 60 rpm was obtained, after which the rotor speed could be varied by varying the lorry’s speed. The first trial, a ground run, took place at Sherburnin- Elmet, Yorkshire, England on 16th November 1943, using the same lorry with a maximum speed of 24 mph. Unfortunately the lorry lacked speed, so the test pilot Sqn Ldr I.M.D Little, was sent to London to buy a faster vehicle. He came back with a 4.5 litre Bentley, which had just enough power to do the job. After three more ground runs the front wheels did leave the ground and Little took the Rotabuggy into the air for the first time at a speed of 37mph on 27th November.

 

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The next flight on 8th December was made using a Armstrong Whitworth AW-38 Whitley bomber as the tug, but due to increased speeds, the Jeep began to vibrate at speeds of around 50mph. So the Bentley was brought back in on 12th January 1944. After two more trials the rotor broke a tail fin. A few days later two more flights were made, but the vibration was still unpleasant.

 

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Then after two more Bentley tows, another trial using the Whitley took place, and this time it flew at a speed of 35-40mph. Later that same day (now 30th January) it reached a speed of 45mph. In a Whitley tow in the 1st February a flying speed of 70mph was reached. Flight tests continued using both car and plane, until test number 30, when after being towed behind the Bentley, the Jeep landed normally, but then swung through a 170 degree to starboard. Both blades struck the ground and 3ft of each rotor broke away and caused the Jeep to shake violently. Little was unhurt, but his passenger, Mr Walker, suffered concussion and broken ribs. New blades were made by the 20th of March, and more tests were carried out, with several modifications being made. After almost 60 test flights, the big day came on 11th September 1944, when Little took to the wheel, towed behind the Whitley. A seven to ten minute full free flight was achieved and the Jeep reached a height of 400 feet, at a speed of 65mph and landed successfully ‘although precariously’. However, this day turned out to be its last flight for Hafner Rotabuggy.

 

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Although initial tests showed that the Rotabuggy was prone to severe vibration at speeds greater than 45 miles per hour (72 km/h), with improvements the Hafner Rotabuggy achieved a flight speed of 70 mph (113 km/h) on 1 February 1944. The last test flight occurred in September 1944, where the unit flew for 10 minutes at an altitude of 400 feet (121.9 m) and a speed of 65 mph (105 km/h), after being released by a Whitley bomber, and was described as "highly satisfactory" However, introduction of vehicle-carrying aircraft such as the Waco CG-4 Hadrian glider made the Rotabuggy superfluous and further development was cancelled. Unfortunately, none of the original Hafner Rotabuggy used in the tests survived until today. In 1981, the Wessex Aviation Society has developed a copy and housed at the museum Museum of Army Flying in Middle Wallop, Stocksbridge Hampshire.

 

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CHAPTER I - Basic airframe & tail construction

 

I found a dieast Solido scale model into a general toy store. It looks more than a toy than a detailed scale model, but it is a pretty good basis to support the attempted project.

 

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Using a screwdriver, I removed all the screws & support pins, breaking the car in parts. This process is necessary, since the model should be improved and start scratching parts from the begining. The reference used for this project are some 3view diagrams and plenty of pictures of the actual Hafner Rotabuggy replica built by Wessex Aviation Society, as placed today at the Museum of Army Flying.

 

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Several raised details on the model’s chassis should be cleared. The spare tire, shovel & axe tools, etc. were removed and stored in the spares box for future use. The windshield, the hood with the supporting structure, passenger & driver’s seats, the instruments panel, etc. were also removed to build from scratch.

 

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The gaps on the metal chassis of the model were filled with epoxy cream. I prefer to use epoxy putty (or polyester filler with fiberglass grains for special purposes) instead of normal scale modeling putty, to close gaps or build new items, because:

  • It becomes solid rock within only few minutes or seconds,,
  • It does not shrink and does not crack after months or years,
  • You can pour to any shape that you want but you need to work fast because as soon as you mix it with catalyst cream approx 5%, you have limited time before becoming solid rock,
  • You can also put additional layers of epoxy or polyester filler to build up,
  • You can sand it, you can drill it, you can use any type of scale modeling glue, any type of primer or enamel / acrylic paint on it with no problem,
  • It can be purchased at any good crafts store into 250ml, 500ml, 1lt (comes with a tube of catalyst hardener) or bigger canisters and if you can't find it, fear not and try your local decent hardware store and finally...
  • It is cheaper than dirt - estimated prices are £3 to £10 depending the canister size, the quality, if contains fiberglass grains for maximum strenght etc

Keep in mind that the chemical reaction after mixing the filler with the catalyst hardener, produces some heat that possibly effect on thin plastic parts, so test it first before try it on your scale model. I don’t think that the produced heat is more than Fahrenheit 110, but better watchout.

 

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Remember that epoxy materials are dangerous when breath or shallow and could result skin, eyes or lungs problems or even cancer when used for long period with no precaution measures. Always keep in mind, that a powerful vacuum system to suck away the epoxy dust should be used all time to keep the workbench area clean while sanding or milling epoxy or resin materials. Using an issued breathing mask and a pair of surgery latex gloves to prevent dust contact with lungs and fingers while sanding or milling epoxy, is also an important matter that you should seriously take care of! My recommendation is to also wear an overall working suit (as I do) to keep your clothes dust free while sanding epoxy. Some people might find it too much, but I wouldn't like to bring epoxy dust & grains from my work bench into living room and my beloved

 

Having already converted and print the 3view diagrams into 1/18 scale, I cut plastic styrene sheet as the tail base line. The plastic base glued onto the metal directly using cyanoacrylate which is necessary to solder non-like materials, such as plastic on metal. Along the glue, the point was reinforced by transverse plastic stick.

 

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As is visible on the pictures, a sparse metal net is placed inside the cabin to support the construction of plywood which is the cabin shell. Tail construction is supported by wooden rectangle shaped frames, arranged parallel to each other.

 

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Wow Nick !

 

What a fabulous and original project

 

I have seen this machine before in one of my Jeep books but I haven't really thought that I will ever see it in scale.

It is great that you prepared your workshop with historical background.

First workshop shots also look quite interesting.

 

Hope to see more soon

 

Best wishes and good luck

 

Kornik

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