Ocar Aston Martin DB3S

Ocar Aston Martin DB3S

Postby wixwacing » Thu 18 Mar, 2010 11:00 pm

Ocar
Aston Martin DB3S


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I reckon I’m just about getting the hang of this scratch building lark and hopefully one day I’ll get good at it. All the work required to get the model up to spec seems to be OK but to this point in time I still have minor disasters with the finishing. The paint jobs look great on camera, but up close I could be critical but then I’d be upset with every model and that is not the joy it has imparted to me! As mentioned elsewhere I look to improve on each model I do and aim at doing something new no matter how small, so that each model is a progression and not just a repeat of something earlier in a different colour!!

With this model I have focused a little more on the detail. Not the paint or the decals, but one or two things I can add to the model which take it just a little step further. With each model it gets harder and harder. On models to date I have built a steering assembly, I have made front motor models and filled out cockpit detail, there has been working front and rear suspension and even a set of exhaust extractors for the Lotus 38!! A work eighteen months in the making and a job very pleasing. I have made models capable of wining their class in full on competition while other cars were for pure driving pleasure, like the little Austin Healey, complete with a home made guide flag to ensure I could keep it out of sight under the model.



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What else?? Mmmmmm? Who’s seen the four wheel drive rear end of the Williams FW08 or the ‘Gulf’ paint job on the Ferrari 360!! Then there is the independently rotating ‘wixle’ front end, Or the PCB chassis which has become my favourite. It emulates the model chassis, and a couple of patent mounting posts sees it readily fitted under the vast majority of models. The full cockpit in the AC ‘Ace’ was my first serious attempt at a front motor / cockpit detail sports car. I have made a couple of GP cars but apart from a driver and a steering wheel they were fairly simple.. The Ace had neither a gear stick or a handbrake lever which are pretty much essential components in the real thing, so this model was going to have at least that!

First up as always was to get the basic body prepared and the chassis marked out and cut. These items need to match up before any thing else happens. You don’t need incomplete chassis dimensions when you are seriously trying to kit out a cockpit and place a motor. Likewise, the chassis dimensions rely fairly heavily on the body being finished as far as preparation and dimensions are concerned. And with both these things in mind I set firstly about the body. Weight was the first priority. The body shell weighs in at about 20 grams and once the drivers tray is installed it could be several grams heavier. Reasons I like to reduce the body weight are simple. Most of the weight for the body is up front, and with a front mounted motor it is going to take a lot of rear ballasting to bring the centre of gravity back behind the motor. This will be necessary to minimise ‘snowploughing’ where the front of the model seems to bog down and the rear slides and slithers trying to push it all along. So the body was initially dremelled into shape. Checking regularly by looking through the body over a bright light I took out as much resin as was safe from the inside, especially around the front of the model.



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The region behind the headlights and in the front wings is fairly thick and represents a small but significant amount of material. This also causes the C of G to travel forward several millimetres. If I was building a rear motor model I would not be worried about it as it would be useful weight over the guide, but, as this model is going to have a front motor I wanted the front of the model as light as possible without compromising strength too much. I eventually got the bare body down to 12.0 grams. Believe me when I say this was no mean feat and it probably took as long to remove the last ten percent of excess weight as it did to remove the previous ninety percent. I suspect some parts became eggshell thin in the process. These spots were reinforced with Tamiya body putty just to be safe.



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With the body weight at optimum, the chassis was marked and cut to fit the body. The chassis was finished around the edges in places with small hobby files and in places where the body was a little out of shape I took the dimensions out to the chassis once again with Tamiya putty. Next, the chassis needed to be mounted into the body, but before this I needed the axles and guides in place and set. The normal process was followed for these and some chassis mounting posts were made and mounted on the three mounting spots. The chassis posts were trimmed and the chassis was set so that the bottom edge of the chassis was flush with the bottom of the body.



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It was at this point I discovered the body may well have been too narrow in height. Whether it was a moulding problem or a trimming problem after leaving the mould, I don’t know, but I was convinced that the body was not deep enough, and this was going to present problems mounting the interior and it would make the model stand too far off the track! I decided to increase the body depth by just under three millimetres. This was done by epoxying three mill plastic sills to the bottom of the body. Once set the sills were curved under and the bottom of the door which had previously been covered over, was recut into the resin. I was much happier with this and once establishing the new side depth, which was about two mil deeper, I continued with the body and chassis preparation.



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A quick glance will show that the underbody profile is irregular, this is because the right hand front wing (guard, fender) is shaped to allow the exhaust system engine pipes to come through the wing and out and down along the side. This was achieved quite easily but it did start to cramp the locations for the remaining items i.e., the chassis posts had to be shaved to allow the motor to fit between them. As I had already set the chassis posts before fitting the new sills, I decided to leave the chassis recessed and extend the exhausts down and out past the inner wing panel.



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The motor position had already been calculated to allow the drivers tray to fit in, in spite of this, the back of the motor was still going to intrude into the tray a little, but this could be disguised as it sat behind the dash line anyway. So the tray was fashioned to fit the chassis and body. This time I just made one seat as the other would be invisible, but I did decide to make a gear stick and a handbrake lever; two essentials in any model. Not having any suitable steering wheel at all and with none being available on the internet I decided to make one for this model too. The last one being the Ace. This time having done one, I was more aware of what I was doing.



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The steering wheel circles were marked on some thin plastic sheet and two circles were cut out very close to the marks and glued together. The disc was then sanded and filed smooth around the outside and the spokes marked on the inside. Using a pin vice and a sixteenth drill, I drilled out the waste between the spokes. The rough holes were then trimmed to shape using a very sharp narrow modelling knife and finished with some modellers files, and the wheel itself was scraped lightly to give it a round section. The spokes were then shaved outside to in, giving a slight dishing effect. A sixteenth hole was drilled through the centre and some sixteenth brass tube was used as the column.



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A small disc of very thin card was glued over the wheel boss leaving painting the last job to do on it. This driver also had his shoulders part sawn through to allow the arms to be widened. Other work on and in the driver’s tray was the prop shaft tunnel to allow the very real propeller shaft to access the rear axle!! Once again, some round tube to the rescue and where the pinion and motor end intruded, the tunnel was widened to allow clearance. The handbrake was hand carved with a very sharp modellers knife and the gear lever was made from a round headed dress makers pin from ‘er indoors’ sewing box, shaft suitably bent and trimmed and painted.



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Once all the axle heights were fixed and the motor and axles were fitted I could set the axle width. More sanding and careful scraping of the inner wheel arches was required here and eventually I managed to get the wheels and tyres in a respectable position closer to the outside edge of the model. The guide tube was then fixed to allow the Ninco sprung guide a bit of vertical leeway. This would ensure the front wheels were somewhere near the track when sat on plastic tracks with raised conductor rails. A couple of last features for the body was a radiator simulated inside the front air intake and fed up with poor petrol filler caps I made one from plastic in the ‘Monza’ style which would have been current for the model.



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The body had been prepared with grey primer and all the imperfections like air holes (very few), dimples and blemishes showed up. These were then dealt with in the normal way and the body was then prepared for its first coat of green. British racing green? Well its Green and it’s on a British racing car so it must be!! You must know my thoughts on that by now!! The first coat was rubbed down with 1200 wet and dry and the second coat was applied. Once dry for a couple of days, the top coat had a very light sand to remove any dust and grit which may have settled in the drying stage, and the model was then dusted with its first coat of enamel clear and left to dry for a day.



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The enamel clear was applied direct from the Tamiya aerosol. I have been having a bit of trouble with colour specs coming from my spraygun when spraying clear so I decide to spray straight from the can. The can was stood in hot water for ten minutes and the body on its lolly stick was placed over the angle poise lamp to warm up. Finally, the first coat went on at a distance of about four hundred mm but I was leaving nothing to chance. No runny gloss coat while my back was turned!! Again this was left to dry and cure for a few days before I touched it again. Once again, with several projects on the go, it takes away the temptation to touch the model while it is still soft or tacky.



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Next up were the yellow crescents over the front wheel arches. Atypical of this model and part of the Le Mans livery no doubt. Tamiya six m.m. masking tape was split down the middle to improve its contouring ability and once the stripes were masked, the tape edge was brush painted with clear lacquer to seal its edge and prevent colour bleeding under the tape edge. Yet again a day or two later, the yellow was brush painted on and left to dry. Next were the silver parts and decals. The decals were applied in their respective positions and yet again, one side at a time. No rush! No smudge, no tears. It was about this time the bonnet buckles were coloured and the tiny piece of ‘bare metal foil’ was placed on the rear view mirror. The filler cap was painted and the model had its final once over before further coats of clear. Before the final clear coat was applied, the headlights and lenses were fitted to the front. These were held in by applying epoxy to the rear pin from inside the model. The area which the clear part sat on had already had a coat of silver painted on and once the lights were in place the front of the model looked very good. The last coat of clear was applied and a couple of days later it was time to make a windscreen!! Yes, make one! There is a perfectly good one which comes with the kit. It is a vacuum formed screen and my only criticism is that it is possibly a tad too thin. This model was going on the track and I felt a thicker screen may be better for those moments when your car is upside down across someone else’s lane and your heart is in your mouth. At this point the driver’s tray was fitted inside the model and some small spots of epoxy were placed on the outer edges of the tray front and rear. These fixed the tray to the body, and the chassis was inserted in place to hold the drivers tray in its correct position. Again, once set, the chassis was removed and a strip of epoxy was painted along the front and rear of the driver’s tray to fix it permanently in place.



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I cut out the supplied screen and placed a strip of masking tape onto the flat surface of a Ninco spares box. The cut out screen was carefully traced round on the tape and the new screen was then carefully cut out of the Ninco box with a short, sharp pair of scissors. Cut edges were sanded flat and smooth and the screen was then shaped to fit the cockpit. This was achieved by running the screen under the hot tap in water as hot as you can bear. The plastic is then wrapped around the handle of an Exacto knife or similar. The screen was offered up into place several times and fresh rolling carried out until the screen was an almost perfect fit. I used to use a hair drier for this stage, but if the clear plastic is overheated, it shrinks unevenly and you end up with a tatty looking screen which is not a particularly good fit!



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The screen was then carefully fitted. Using extra strength epoxy, I painted the lip which the screen was to fit inside with an even coat of epoxy. The curved front section was offered into the front edge and the rear side ends were discretely superglued into place inside the cockpit opening. Care needs to be taken here as superglue fumes will cloud the clear material, so, minimal super glue is applied and applied at least two millimetres away from the visible part of the screen. Almost immediately after I painted all around the base of the screen with epoxy. This also coated the cockpit rim and once dry, the screen was quite securely in place. Yet again, all was left to dry and cure.



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The body was looking just about finished with the exception of the exhaust. This would be the hardest bit but surprisingly it all fell into place quite quickly. The exhaust is made from brass rod and screwed to the underside of the model. Both parts were carefully shaped and made to fit together. The top ends were tacked together with solder and a thin strip of solder was applied to the underside of the horizontal pipes. There were a couple of tags with spacers soldered in place on the inside of the pipes. These would allow the pipes to sit in place under the right hand side and allow them to be removed when or if the chassis needed to be replaced. Once a good fit they were sprayed with a ‘bright chrome’ paint from the local auto store.

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This just about completed the model and I was very pleased with the end result. Once again, not a true scale replica of the original car but a lot closer than people can distinguish without pictures. The best thing is that the model drives well too. Most of my models have a ‘bare body’ test run when the chassis have been built and this was no exception. The model runs very well on the ‘Red Teams’ home track and if the AC Ace is anything to go buy it should be a fairly competitive pleasure to drive at the occasional race meeting. Chassis wise I decided on the Cartrix TX1 motor and I used a Fly transmission spring to drive the prop shaft. Rear gears are an SCX pinion and an SCX twenty seven tooth crown gear, run in with Tamiya fine polish.


World Classics (Ocar)



So that’s about it . Possibly another thirty hours plus spent on the model but very rewarding. I already knew the model drove well so all that’s left is to get it into a race somewhere. In this part of Queensland we like our classic cars to travel at classic speeds and the NC1 is the first choice for our classic and historic racers. I don’t know if the TX 1 is an NC1 in disguise but it is about the same speed. The model carries about ten grams of lead beneath the rear axle to improve the front / rear weight distribution and the front of the model rests on its wheels on board tracks. So, let’s go looking for a race somewhere!!


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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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wixwacing
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