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2,051 Posts
Discussion Starter · #1 ·
I realise that after I released the Williams Fly dedicated chassis design And set up this shop I let the original conversion thread 'die' without reposting the old photobucket images....

However as a guide to how to use the Universal Chassis it is still a useful 'how-to', especially the parts that deal with the set up of the chassis itself.

So I thought i'd repost it here:

Williams FW08C Policar Conversion

So while everyone is waiting more or less patiently for the release of the first model I thought I would demonstrate how to use the forthcoming adjustable chassis and gearbox kits to convert some existing models to Policar set up.

I originally conceived this chassis for kit bash / scratchbuild resin bodies but once prototyped I realised it could also be used to convert some existing bodies, making conversion even easier and quicker.

We think this is interesting in order to provide a variety of cars to compete against one another once the first full cars hit the market later this year.

We looked at which models might be suitable for conversion and concluded that only models conceived as bodies mounted on chassis would work.

We are also conscious that many people will have bought a model and might not want to 'damage' it in the conversion process so that it can be reassembled, in its original form, once raced as a 'Policar'. As the project progressed however it became evident that this was always going to be difficult. I will point out in the text and photos where modifications are irreversible and what alternatives exist to ensure such modifications don't have to be made if the builder doesn't want to.

We began with the Williams FW08C for several reasons:
1. They are still commercially available at time of writing.
2. They are economical in price.
3. They allow simple conversion due to their geometry.

This did however cause certain difficulties:
1. Policar do not currently market suitable tyres (or wheels) to fit this period of cars.
2. The larger diameter front wheels used in the 1980's push the front axle height up, limiting the ability to keep the chassis as low as we would like since our chassis is designed for 1970's cars with much smaller front wheels. Some readers might prefer to ignore scale over performance and smaller diameter wheel and tyre combinations would allow this.

The Conversion:

Step 1.
Disassemble the donor car removing the three screws under the chassis.

Green Toy Aircraft Airplane Machine

Clip off the rear of the gearbox to reveal the screw that holds on the rear wing. Unscrew the rear wing and set aside. Remove the front tyres from the donor model.

Remove the gold coloured wheel insert disks. These are glued in and are quite delicate so take great care getting these out without damaging them. Alternatively make your own by cutting / drilling out the forms from plasticard of about 1mm thickness and paint / spray gold. I took mine out by inserting a pair of tweezers into a couple of the holes and gentling twisting / pulling. They came out well enough that I could then just superglue them into the new wheel hubs.

Green Product Blue Technology Plastic

None of the rest of the model will be used in the conversion.

Step 2.
Measure the wheelbase of the donor vehicle, or check what the wheelbase of the original car was.

Motor vehicle Automotive tire Asphalt Automotive wheel system Automotive design

I found that Fly had got it about right with 81mm wheelbase on this model.

The Policar adjustable chassis is designed to measure 71mm from rear axle centre to the front of the side pod as shown in the photo, so one needs to position the front part of the chassis so that the front axle centre line is 10mm ahead of the same side pod line thus:

Green Tire Automotive tire Office ruler Motor vehicle

Office ruler Font Road surface Rectangle Asphalt

Mark up one or more of the screw positions from underneath with a bradel. My chassis is 3D printed but once moulded these will be in black plastic.

Circuit component Electrical wiring Cable Gas Wood

Step 3.
Drill out at 2mm diameter the first hole and screw the chassis elements together from the top. Various screws can be used and depending what you have available ensure the diameter is right for you making a tight fit without splitting the plastic. Proceed slowly, working the screw back and forth if necessary to 'cut' the thread.

Wood Circuit component Line Engineering Gas

Once one is tightly fitted, drill out and screw home the other three screws to give a nice strong connection.

Step 4.
Now mark out the superfluous areas of front chassis that need to be cut out to allow the motor mount to be fitted.

I cut using a thin saw and scalpel.

All screwed together it now looks like this:

Calipers Cutting mat Wood Toy airplane Hand tool

Step 5.
Now the body and chassis can be brought together so we can start to see where the chassis needs to be cut to fit under the body.

Table Toy Aircraft Font Machine

These 1980's cars had thin noses and front wings so the whole front end can be cut off either side of the front axle support.

By holding the assembly in place I marked up the outline of the body onto the flat plate chassis.

Circuit component Electronic component Electronic engineering Cable Engineering

Before cutting I also marked up the position of the two fixing screw posts on the original body and drilled these. This helped me to accurately mark out the body cutting line. I inserted a couple of drills temporarily to hold things square while I marked out with a red pen.

Green Motor vehicle Wood Engineering Machine

This also revealed that the body will cut across the two motor mount screw positions designed into the chassis so I cut those off flush which helped further get everything flat.

The eagle eyed will notice that when cutting the chassis it shattered on one side. This is because the 3D printed material I use for prototyping is highly detailed but very brittle. This won't happen on the injection moulded plastic parts that will be available on the market.

To help strengthen my model I glued on a couple of thin plastic strips. Again you won't need to do this. Suffice to say that this whole set up is very 'modifyable' and I can imagine as many solutions as there are builds once people start building them.....

Step 6.
Once cut and filed flat around the edges the chassis slips up inside the body. A quick test fit before pushing on.

Step 7.
In order to fit up high enough I needed to cut out the bottom of the driver's seat. This then is the first non reversible modification. There are options:

1. If you wanted you could do this build with a very minor cut at the back of the seat thus retaining the screw position. To do this you would need to:
a) cut the front of the motor mount off and use it with a single screw mounting.
in turn this would render the motor mount to chassis fixing weak and I would suggest therefore securely gluing or fixing it together to prevent movement and potential breakage of the single screw fixing.

2. If you don't want the cut at the back of the seat at all you could move the whole body forward on the chassis by around 3mm and with the motor mount modification (above) this should then just clear the seat.

Step 8.
Once done the chassis should now sit so that it aligns nicely with the body sides.

The screw fixing pillars need to be raised. In the spirit of simplicity I cut two 10mm long cylinders from a bic biro and glued them to the body as spacers (see previous photo). You don't have to glue them if you don't want to modify the bodyshell.

Tire Wheel Automotive exterior Tread Bumper

Step 9.
When it comes to the rear wing by cutting off the bottom of the fixing a reasonably large flat area can be obtained. I drilled a hole in that and then worked one of the original models screws back and forth until it screwed snugly into the hole.

Wood Rectangle Wood stain Material property Flooring

Triangle Electric blue Rectangle Font Symbol

I drilled out the hole in the back of the motor mount as a pass size and simply screwed the wing on from underneath. This might twist so a bit of glue can be applied to prevent this.

This is clearly non reversible and the only alternative I could think up was an option to build yourself a new rear wing in plasticard and / or brass sheet. That would be quite a lot of work and only appeal to the modelmakers amongst you but it is an option.

Step 10.
Another test assembly with some larger front wheels onto which I have mounted the original tyres shows the model coming together.

Tire Wheel Vehicle Car Automotive tire

These wheel hubs are 15.8x8.2mm and as you can see accept well the original front tyres.

Step 11.

In order to fit the front axle and prevent it sliding sideways there are two solutions:
a) fit a front suspension movement restrictor
use grub screw collars between the chassis axle keepers

I chose a) in order to add a little detail and to keep weight to a minimum. I measured up and cut out a simple plastic form that mimicked in a simple way the suspension on this car and cut out of 1.5mm thick plasticard this form:

Road surface Asphalt Vehicle door Automotive exterior Flooring

This was glued to the top of the chassis:

Art Motor vehicle Machine Engineering Event

Once assembled it looks like this:

Tire Wheel Vehicle Automotive tire Automotive design

It might be nice to paint this item black but to keep this simple I have left it white.

On the rear I have used Ostorero Wheels and Tyres from their Lotus 79 kit. These are available separately if you approach Ostorero through their website or by telephone.

Other after market wheel and tyre combinations exist but I have found these tyres and wheels with their Goodyear printing offer the best compound.

Policar intend to release the appropriate sized wheels and tyres in due course when they make the forst of the Lotus 72s post 1972.

Once the wires, braid and guide are fitted the car is now complete and ready for the track.

Total conversion time about 3 hours.

The completed car:

Tire Wheel Vehicle Car Automotive tire

Tire Wheel Car Vehicle Automotive tire

Tire Wheel Vehicle Car Automotive tire

Thank you for reading,
Andrew Rowland


4,887 Posts

I've ordered several of the chassis today for the Fly Brabham BT44, the Scalextric 312 T2 and a universal chassis for a yet to be decided car.

On the website you don't show a 3D printed chassis like the prototype in this thread (with the large oblong area in front of the guide that could be trimmed to fit under a bluff nose) am I right to assume that this version never went into production?


1,801 Posts
The item is "scratchbuilt chassis generic F1" It's printed as one part which you have to separate. The resultant two parts then fit together- and it does have the piece in front of the guide.

4,887 Posts

I'm not quite sure what you mean but I will wait to see the chassis when it arrives and get back to you if necessary.


2,051 Posts
Discussion Starter · #6 ·
Hi David, I'm struggling to help more as I'm on the beach!
Basically the two parts have been joined as one to make printing efficient. Once they are cut apart (there are two short sprue that need cutting), the front piece is turned through 180deg. and then you will see that the front part of it is indeed wide.
I'd do a drawing but cannot right now.
Hope that is more clear?
Best wishes

4,887 Posts
Sorry to interrupt your paddling....

The bit I missed was answered by the caption in your drawing that says, "turn this part around", it now makes complete sense to me thanks.

Thank you and I'll let you get back to your bucket and spade.

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