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REMOTE CONTROL BY BOB YOUNG Modellers with dedication; Pt.3 This month, we continue the story of John and examine his involvement in model car racing. In doing so, we will look at the development of model car racing technology over the last 20 years or so, to the high-power models of today. When I first met John, he was building and driving full-size racing cars so I guess that the progression to model racing cars was fairly natural. As we have seen from last month’s story, John’s first love seems to be model railroading and when he takes on a job he does it with great flair and energy. One striking feature of John’s workshop is the sheer volume of model car equipment hung neatly in racks and from hooks on the wall. There are chassis of all types and descriptions that effec­tively present a full history of R/C car technology over the past 20 years. In this story, we will examine the development of this technology in some detail but first a little background on model R/C racing. The International Federation of Model Auto Racers (IFMAR) is the world governing body for R/C racing. This is divided into various divisions and John is the president of the One Eight Scale division. The Pacific region, in turn, is governed by the Far East Model Car Association (FEMCA). I will give you one guess who is the president of this erstwhile body – right again, our friend John. Under this umbrella shelters the Australian Associa­tion of R/C Model Car Clubs. As you can see then, model R/C racing is well organised and there are vast numbers of people who race or enjoy running R/C models of all types. John’s own collection of wheeled vehicles ranges from model tanks to high performance race cars, with racing trucks, electric cars, scale semi-trailers and mammoth scale racers all thrown in for good measure. John’s son Stewart is a world-class one-eighth scale car driver and the pair make up what can only be described as the ultimate dynamic duo. Their showcases are loaded with trophies from all over the world and it is interesting to speculate who dragged who into the business of R/C racing in the first place. However, I think it has now settled down to the usual arrange­ment: father builds the models and the son has all the fun driving them. Talking with Stewart is fascinating as he explains the technological explosion that has taken place in model cars, as it has in all fields of human endeavour. The series of photos in this article show the progression of that technology but they do not adequately capture the actual feel of that development. When you see all of the bodies lined up side by side, the first thing that strikes you is just how complicated the newer vehicles are. More than that however, the new models are so substantial in construction, yet weigh in at not much more than their fore­ bears. This is made possible by exotic new materials such as glass-filled Nylon, carbon fibre, etc. Motor size Photo 1: the first in a line of model race cars. This is fitted with an OS .15 engine capable of about 0.3 hp. It has a rigid front axle, small tyres, no gearbox, no diff & a simple centrifugal clutch. However, the most striking feature, to me at least, is the size of the motors. Admittedly, the car in photo 1 is only fitted with an OS .15 but in those days the OS .15 (2.5cc) was only fractionally smaller than the OS .21 (3.5cc) and externally both motors looked almost identical. Incidentally, the figures .15, .21, etc refer to the November 1994  83 Photo 2: this chassis is quite capable of absorbing the 1.4hp from the K & B .21 motor fitted to it. Here we see a flex chassis fitted with a simple differential, single disc brake & independent suspension but still fitted with a simple 2-wheel drive at the rear. Photo 3: here we see the first of the 4-wheel drive cars from around 1985. This car is a P.B. X-5 & features such advanced items as a progressive locking differential & rear wheel roll steer­ing which is adjustable to provide over or understeering when cornering. It has a 2-speed automatic gearbox & 4-wheel drive. swept volume of the motor in cubic inches. This is the American system of engine sizing. The English system uses cubic centimetres (cc) and the English sizes are given in brackets. These days, the American system is the most commonly used. Compare the size of the motor in photo 1 (circa 1972) with the size of that in photo 4 (1994). The 1994 motor is still only a .21 (the maximum 84  Silicon Chip allowed under the rules) but it looks substan­ tial enough to be a modern .49 aircraft motor. This increase in size has come about because of the requirements for more cooling and stress containment, due to the very high RPM these motors are pulling. Cooling problems Cooling in model cars has always been a major problem, particularly as the original motors were mainly designed for model aircraft, where copious quantities of cooling air were available. Thus, the cooling fins of the old model aircraft motors were grossly inadequate for motors intended to spend their life locked up inside a plastic body, away from a high-speed airflow. The original fix was a bolt-on heatsink and the car in photo 1 shows a primitive bent aluminium heatsink of this type. This type gradually gave way to the bolt-on finned heatsink which in turn gave way to the dedicated replacement cylinder head. This came with a very substantial extended heatsink and replaced the original cylinder head of the model aircraft motor. While all this was going on, the motor rework boys were beavering away at squeezing out every last drop of horsepower possible. The result has seen motor power skyrocket and thus the need for more and more substantial castings in the crankcases and more heatsinking again. Likewise, cylinders, pistons and conrods have all increased in size. The results of this development are shown quite clearly in the series of photos presented with this arti­cle. For example, the OS .15 (from memory) had a rating of about 0.3hp at about 10,000 RPM. These are approximate figures only as none of us can remember that far back. In those days, a good .60 would deliver about 1hp at 10,000-12,000 RPM. Compare this to the motor shown in photo 2 (circa 1980). David Hyde won the Austra­ lian one-eighth scale sports GT championship with this car. The motor (K & B .21) gives out 1.4 hp, a remarkable increase. Compare this then to the motor shown in photo 4 and here we are looking at a Rossi .21 which develops 2.3 to 2.4hp. The results of this phenomenal increase in power are cars that are capable of 125km/h on a 90-metre straight, with acceler­ ation of 0-100km/h in under three seconds! Incidentally, Stewart tells me that from about 1980 onwards, the model car fellows have been getting good results with the newer synthetic oils. Oil such as EDL and WB have been giving excellent results with mixtures containing as low as 8% synthetic oil, 2% castor oil, 20-30% nitromethane and the rest being methanol. Photo 4: this car exhibits the rampant technology of today. It has a motor fitted with a mini-tuned pipe giving out 2.4hp, an automatic gearbox, 4-wheel drive with changeable overdrive ratios bet­ween front & rear wheels, centrifugal clutches, Sprague clutch­es in the gearbox, front wheel drive & independent suspension. It is all made from exotic materials. Stewart tells me that the castor oil is to provide the smoke which acts as a guide for obtaining the correct running mixture. I suspect however that the castor oil also provides the upper cylinder lubricant required for the extremely high head temperatures encountered in model engines. Here I must add my usual warning that these are not my recommended figures and that you use synthetics other than those mentioned above at your own peril. Personally, I have never had any luck with synthetic oils, but I have also never used the above lubricants. I certainly intend to try some of Stewart’s fuel in the near future and I will keep you posted on the results. Chassis development Returning now to the actual car chassis, it is obvious that we are now faced with a very serious problem. How do you control or absorb this amount of power, especially into a chassis as primitive as that shown in photo 1? A quick look at it reveals the inadequacies: a rigid front axle, small tyres, no gearbox, no diff, and a simple centrifugal clutch which even then was inade­quate and broke on the second run. There is no way that this chassis could absorb 2hp or more. Photo 2 shows a chassis which has been developed to a large extent. This chassis is quite capable of absorbing the 1.4hp from the K & B .21 of that day. Here we see a flex chassis fitted with a simple differential, a single disc brake and independent suspension but still fitted with a simple 2-wheel drive at the rear. John and Stewart did extensive re-manufactur­ ing on this type of car to get the performance they required. The kit manufacturers had not yet caught up with the enthusiasts. Photo 3 shows a vastly superior car, circa 1985. Here we see the first of the 4-wheel drive cars and the kit manufacturers are starting to close the gap. This car is a P.B. X-5. Still heavily remanufactured, it nevertheless represents a quantum leap in chassis design. The technology in this chassis is staggering. This car features such advanced items as a progressive locking differential, rear wheel roll steering which is adjustable to provide over or understeering when cornering, a 2-speed automatic gearbox, and the very useful (some would say essential) 4-wheel drive. The 4-wheel drive is particularly clever and features Sprague clutches, or what are commonly known as one-way bearings. Thus, when the rear wheels slip or spin, the power is transferred to the front wheels via the Sprague clutches. Now we have a chassis capable of absorbing all of the power you can cram into it. By now it is starting to become obvious that tyres are starting to become an issue, just as in full size motoring. Space does not allow a detailed examination of this problem, which could fill a column of its own. Suffice to say that the real skill of the driver is in his ability to assess a track and fit the correct tyres for that day. This is particularly difficult when visiting strange tracks where you only have one or two days prior to the competition to prepare your car. The whole business of model car racing is an intricate and detailed science and it is easy to see how the enthusiasts become wrapped up in beating the problems presented by this very demanding sport. Photo 4 shows the latest in the line of development and here we see rampant technology: a motor fitted with a mini-tuned pipe giving out 2.4hp, an automatic gearbox, 4-wheel drive with changeable overdrive ratios between front and rear wheels, cen­ trifugal clutches, Sprague clutches in the gearbox, front wheel drive and independent suspension. And it is all made from exotic mate­rials. This is virtually a full kit with little remanufact­uring and the overall finish, design and construction of the kit is immaculate. So what is left to separate the men from the boys on the race track if it is possible now to just walk into a shop and buy kits such as this? The four scales featured in these photos tell part of this story. These are used for precise balancing of the cars. I am not going to reveal just how the balance is correctly set but suffice to say that the knowledge required to set up a car correctly is not easily come by. Finally, a few words about the radio systems. Stewart uses simple 2-channel radio sets with few bells and whis­tles but is very particular about the brand and even the model number of the receivers he uses. He runs the whole radio on 7.2V but finds only certain receivers will operate satisfactorily on this voltage, hence his choice of mainly older model receivers. He is also very fussy about servos and servo transit times. He feels that some of the new servos are too fast and has settled on transit times of about 0.36 seconds as being ideal. He raises a serious objection to modern servo savers, stating that they are no longer powerful enough to handle the torque from the modern servo and need to be SC doctored to do so. November 1994  85