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MRRCMercedes W154 body conversion

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wixwacing
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MRRCMercedes W154 body conversion

Post by wixwacing »

Mercedes W154

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By Phil Wicks
World motor sport has its beginnings in the global endurance races with nearly all continents offering a ‘Grand Prix’ to the victors. For many years the main competitors were privateers and small companies. From the very early days Mercedes produced ‘customer’ engines and chassis for those with the money and they also took part themselves. This was before the days of dedicated motor racing circuits. Street and cross country racing was the norm and famous races such as the Paris-Peking and the Gordon Bennet races epitomised endurance. Circuit racing was to follow on such mammoth circuits as the Nurburgring tested marque and driver alike, and the Targa Florio introduced the concept of a ‘one’ lap race. Again, the privateer was the mainstay of these events with manufacturers making up an important part of the field.



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Two manufacturers that were at the forefront of post WW1 motor sport were the Benz Company of Mannheim and the Daimler Company of Stuttgart. These companies went head to head in the post war years on the street on the ocean and in the air. It was their developments and spin offs from the aero industry which was to transform their prowess on the track. With the invention and development of the supercharger, both companies were to produce cars that would be unapproachable in competition. It is interesting to note that in 1924 Daimler and Benz chose a period of co-operation in their business activities and two years later they amalgamated to form the now legendary Daimler Benz marque. It is also interesting to note that it was also about this time that one Alfred Neubauer was racing Daimler cars and it was also about this time that an engineer called Ferdinand Porsche took up the offer from Paul Daimler to work on his Grand Prix cars, and the rest, as they say, is history.



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Porsche went on to design the first Mercedes-Benz Grand Prix engines and Neubauer ended up as the legendary boss of the ‘Silberfeile’ (Silver Arrows) racing team. A third name, Caracciola, was to stamp the Mercedes hall mark on almost every important race from here on. The late thirties saw Mercedes Benz cars achieve success in most fields of motorsport with only the current land speed record being out of their reach. The W125 had vanquished all before it and Daimler-Benz were quite prepared to rest on their laurels. As the Nazi era was approaching its zenith in Germany, the need for markers of supremacy to the rest of the world caused the company to be dragged back to international motorsport harder and faster than ever. The Auto Union Company too was to be part of the propaganda.



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With new world governing body rules came some very different approaches and with restrictions on engine size and supercharging and minimum car weights the old models were dropped for the new season. Auto Union built their successful type ’D’ and Benz evolved the 154. Based on the 125 chassis but with the new 3 litre V12 engine it finally ended up with an output of 480 hp at over 7,000rpm with the use of a dual stage supercharger. 1938 and 1939 saw Auto Union and Mercedes Benz swap wins blow for blow and it was only world circumstances which brought an end to their dominance.



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Needless to say, much like the attraction to Porsches and Ferraris, the Silver Arrows have called to me from the past for many years and it is only natural that now, with extra time and skills to hand that I should start to indulge in their aura.



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Model of choice this time is the MRRC body as purchase from eBay. The model came as a two or four wheel drive kit using the Kay’s style motor. Unfortunately, these models now appear to be currency on the open market and this rules them out of my acceptable price range (until my lottery win come along). So for about twenty five dollars including freight I secured one from eBay. Remembering these moulds were made at a time pre CNC and CAD, we must expect some discrepancies in dimensions and in scale representation. But having said that, the model looks a pretty good likeness when comparing it to pictures on the net. The aim was to do the real thing justice or near abouts. And as always, the best approach is to have several projects on the go at the same time, this will minimise the risk of ‘stuffing up’ due to impatience!



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The first task is choice of components. I decided on a Wixwacing brass tube chassis as I find these most forgiving when looking for space under a model. Next choice was the NC 1 motor. This was important as I didn’t want this to be a pocket rocket, more a good drive in non competitive circumstances. Next, as I wanted to portray a cockpit and full length driver I would need to mount the motor up front. And lastly, something a bit different? this was to be front AND rear suspension, well if Ninco can do it, so can I?!



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The chassis was drawn out on a piece of three millimetre MDF. This is where the dimensions are finalised and the pieces of the chassis are cut to size. The pieces are then clamped to the drawing and soldered in position. I must stress here that before you solder anything, you must clean the parts to be soldered. This type of construction, with lots of soldered joints near each other, requires minimal heat to prevent adjacent joints from desoldering! I help the process my clipping miniature alligator clips either side of the joint in progress to act as heat sinks. This is very effective.



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The guide mount is the front cross brace and the prop shaft rear mount becomes the rear. After this the two cross braces which take the front and rear mounting screws can be soldered in place. The front and rear axles will be mounted in suspension. I have decided to use some thin brass strips as ‘leaf’ springs. The strips are shaped to the desired shape and the axle mounting tubes are soldered to the ends. These springs should be already cut to dimension but if there is some fine tuning of wheelbase to be made, it can be done quite easily by bending the short ninety degree bend at the chassis end of the front spring.



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Once all these items were in place, I offered the completed chassis into the as yet, untouched body. Untouched because from here on in, everything that goes on the model may well require the body to be altered accordingly. So, the front and rear axles are assembled and after transferring dimensions from the body, the motor is soldered into place on the chassis. I was aiming at having the chassis mounted flush with the bottom of the body rather than having anything hanging out. I had then to set the front and rear axle height to get a good ‘pose’ for the model. Once happy with this, I needed to mount the motor in line with the prop shaft hole. This required the motor to sit between the chassis rails. In achieving this I had to file the inside edges of the rails a bit to allow the motor to sit inside and inline with the rear end.



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The prop shaft consists of an SCX contrate, a Fly transmission spring (available two to a pack) and a 2.5 mm shaft of some sort. The easiest source for a prop shaft was one of the many SCX 4WD motors I have in my scrap box. It was a simple case of stripping a motor and cutting off the pre determined length of shaft. Later on in testing it proved that the springs weren’t tight enough on the shafts and after trying superglue and the like, I finally settled on tinning the motor shaft and prop shaft with solder and desoldering with desoldering wick. This left an even coat of solder on both parts which would hold the spring admirably.



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Wheels and tyres were to be a problem but as yet I don’t have the final solution fitted. I was building the model before I had the wheels and tyres to hand. My first thoughts were to buy an old 1/24th scale MG TC or similar. This would give me the correct size wheels and tyres could be sourced from the O-ring box of the local auto store. But as the model progressed I was having trouble locating a well priced MG!! The next short term solution which I am still using was to fit Ninco spoked wheels and fit Airfix Classic GP tyres to the rear and Airfix GP rears to the front. This looks and drives a lot better but is still a bit out of scale. The solution appeared to me whilst in Scalexworld in Adelaide. Whilst looking at the models in the display case I saw the Ferrari 375 Fangio model. Now, knowing how good the spares supply is here, I ordered a set of front and rear axles and tyres. As yet they haven’t arrived but I did buy another 375 some weeks later with the intention of using the wheels and tyres from that! But as yet I haven’t brought myself to ripping the wheels off this lovely model. So I still hold out hope of the spares arriving from Scalextric!



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Once the chassis was looking good in the body the tube which was to hold the guide was set, complete with guide, in the pre drilled front cross brace. The height was adjusted ’til the model weight was just taken on the front wheels. The tube was held in place with a spot of solder and was fixed securely after the guide was removed. The chassis was now approaching completion and one of the final stages before body decorating was the chassis mounting posts.



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Until now the chassis had been resting on some cut down mounting posts at the sides of the mouldings. I didn’t want to use these as they weren’t well placed so I made two new posts. I have some different diameter ‘telescoping’ plastic tube which I cut to regular lengths and a bit longer than I wanted. These tubes where then coated with liquid polystyrene cement and slid into each other. They were left to dry for several days and eventually were mounted in a cordless drill set on slow speed. Turning the tubes I was able to scrape the exposed end with a modelling knife blade. This resulted in a perfectly square finish on the end of the tube.



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Next I sourced the screws I would be using on the finished model and, after filing a couple of flats on a spare one, I screwed it in, much like a thread tap, using a one turn in, half a turn out motion until the screw was completely screwed home. This gave me an excellent thread without damaging the post. Both posts were then screwed to the completed chassis and offered into the body. I knew they were too long and the next operation was to cut them to length without over doing it. This was achieved by measuring and under trimming each post. And once closer to the final length, the posts were trimmed with the dremel until they were just short of the body.



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The body end of the posts (at this stage, detached from the chassis) were scored to form a key. The previously marked post positions inside the body were also cross hatched with the point of a modellers knife. The posts were re affixed to the chassis and an amount of slow curing super strength epoxy was mixed and applied to the post ends AND to the body. The chassis and posts were then fitted into the body and the whole was left to dry on its back. This ensures the slow drying epoxy doesn’t run down the posts away from the jointing area.



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Once cured (forty eight hours or more) I could then start the body. One of the disappointments of the body was the one piece moulded in driver. A bit bulky and not too revealing as far as a 3D cockpit was concerned. I had purchased a ‘Penelope Pitstop’ driver from Pendle’s but was very disappointed by the smallness of the skull capped driver’s head. The body was fine but then I don’t have a shortage of bodies, strange as it may sound. One of the best is the Airfix head from the Auto Union kit but again I had run out of those so the next decision was to create many hours work but worth it to me in the end. I sourced an old peaked helmet head from an early model and proceeded to cut, grind and Dremel it into a ‘skull capped’ head!!



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I painstakingly cut around the driver with a very sharp modeller’s knife. Then I painstakingly cut around the steering wheel too. After this, the driver had a pair of Fly lower body parts attached and glued in place. The rest of the driver had some of the half exposed voids filled with modellers putty and once dry, it was carefully and laboriously shaped into the missing part of the drivers limbs. Next was the steering wheel. Again the wheel was formed from the injection moulding and eventually the wheel had a piece of plastic glued behind it to represent the dash area. Next, the driver had the rest of his seat fabricated and a final application of body putty left only a bit more sculpting to do. When finished I hand painted a layer of flat grey acrylic over all the parts to show up the remaining imperfections. Action could then be taken and the remaining parts repainted.



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Next up were the exhausts. The kit comes with a couple of ‘straight through’ pipes which look a bit gangling once on the side of the model. They also required the mountings I had cut and covered with the chassis!! no matter. Extensive study of downloaded internet pictures showed the exhausts tucking under the car before the rear axle and emerging from under the body work at the rear. Some working parts of the chassis weren’t going to allow this so a compromise was reached and at least I didn’t have two exhausts pointing out into space!



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The next problem was that the exhausts have to pass UNDER the rear axle! This was the next headache and the solution was to fabricate the two pipes from brass and solder them to a couple of braces which located under the body screws. This way the exhaust could be taken off before the chassis was removed. So, the exhausts were bent to shape and a couple of plates made and drilled. I wanted the exhausts to look part of the model instead of add ons, so the front ends have a ‘turn in’ end which passes through a couple of holes drilled in the body. This looks quite effective and it is a simple matter to flex the exhausts out on their thin braces when fitting or removing, which hopefully won’t be that often once the model is finished.



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With the finishing post in site the easy bit was the paint and decal job. The model had already had a coat of grey primer and all the imperfections like moulding dimples etc had been fixed. A final light dusting showed the model to be ready for a top coat. So next was a coat of silver. Again, a coat of Tamiya acrylic silver. This is not a plain silver but has a bit of a metallic grain to it. Probably not correct for a polished aluminium body but it does lend itself to a nice even finish with a degree of depth. Hindsight dictates that I should have really used one of the proprietary spray on ‘Chrome’ paints available from the local auto store, as these have a lovely smooth sheen and look more convincing, but there we go. So a good coat of silver was applied and after a period of a couple of days, a coat of thinned clear was applied. Again a couple of days later the decals were applied to the clear coat. My decals are from Patto’s place and I have used them to do other Mercedes and Auto Union models, why, because the decals are red with the obligatory black silhouette line around them, often missing in other decals!



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The fuel filler caps were ‘Bare metal’ foiled and glued in place. Then the whole was given an unthinned coat of clear. This has a tendency to stay soft for several days so the model was put aside for a period before finishing. Last up was the flat or ‘matt’ detail. Obviously this can’t be done before the final clear coat so now when the model is safe to handle, the last details can be applied. The driver had his detail picked out and was given a set of white overalls. The steering wheel was painted and the head and skull cap also coated. One rule I use for fine detail is to do the fine detail first. Then, if you smudge or over do it, it is easier to cover with the overlapping colour. So the order for the drivers head was 1. skin 2. eyes 3. mouth 4.skull cap 5. skin again to size mouth and eyes and to define edge of skull cap and scarf. 6. goggles and strap 7. coat of clear on eyes to define lenses and 8. final skullcap to define edges of goggles strap.



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Next task was the radiator grill. This is also silver and I wasn’t going to recreate this from bare metal foil but because it is silver too, I needed a way to give it a bit of depth. The resultant fix was devised after an observation of paint I had applied on another model and m\y solution was to drop a spot of flat black paint into some paint thinners. This was then applied to the grille area with the body in a vertical position. As hoped, the pigment in the mix fell to the bottom of the solution and rested in the ‘valleys’ of the grille. Once dry it looked very effective and a light rub with a piece of linen brought the colour back to the high spots. Task completed!



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Next up was the track!! Mmmmmmmmm? how was this besprung model going to perform? The fronts weren’t a problem as I had tried and tested them on my type D Auto Union. But the rears? An unknown quantity. Well Mr Ninco could I do it! Alas, no! I had run the gears in for some while on my test bed at home and everything was A1 but I still wasn’t convinced that the spring travel was healthy. Excessive, yes but healthy, no! It proved that when accelerating and braking, the gears moved too far out of mesh and bound quite noticeably, causing all sorts of antics. Perseverance achieved nothing so some fresh ideas were needed. The problem was the rear springs were too long and had too much spring. They could have been thicker material but it was too late for that. They could have been shorter but it was too late for that too!! What was needed was an effective but not debilitating solution. One idea was to solder something in place half way down the spring to shorten its effective length. That may well have worked but again I wasn’t happy.



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As always, solutions come by discussing this with friends and fellow scratchbuilder. I took the model to a race night to test it on a shorter less speedy circuit and sure enough, the model was better behaved on a twisty technical circuit than when tearing down some long straight and braking at the far end! Between two or three of us we tossed the problem about until it was mentioned that maybe a ‘silicone’ shock absorber could be used!!?? Read on! Later in the week, a bead of silicone was carefully applied to the centre of the rear springs. This was to act as a flexible brace and damp the spring action. Sure enough, some days later at the ‘Red Team’s’ home circuit, the model was tested and there had been a marked improvement in the rear end hop. Once home again I extended the silicone further down the spring and subsequent testing has shown that in all but extreme braking cases the model now works fine. It accelerates smoothly and brakes well from speed. I’m not sure if the current level of suspension is beneficial but it does work and I’m happy!



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So what is it like, well it is an NC1 and therefore it drives respectably fast for the model it is depicting and like all NC 1’s it prefers about sixty ohms of controller to get round the tighter bends. Acceleration is good but I think the large Airfix tyres are still a little out of round. The over geared rear end extends its braking zone but then again that’s not a bad thing either. All in all a very pleasant drive and maybe one day it will get its proper wheels and an outing in a non magnet competition, but for now its a good drive between events,


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and even better between its stable mates!


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When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
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