Scalextric Mclaren M7C to Policar gearbox conversion

This is a how-to for converting a Scalextric Mclaren M7C into a Policar racer.

I have chosen to convert the Yellow Surtees car:

But these other liveries are all convertible:

This makes a really nice, smooth and quick handling car.

So this is how I did it and should form a clear guide to anyone wanting to do the same.

1. Parts you will need:
A. Policar:
Although it is possible to build this conversion by buying individual Policar parts:
Complete gearbox (without outrigger screw positions)
Narrow Screws to fix gearbox
Gearbox top and DFV engine parts
Rear wheels
Rear tyres
Front wheels
Front tyres
Front and rear wheel inserts
Front axle
Guide, wires, grub screws and pick ups

It is likely to be cheaper to use a donor Policar March 701 and, in addition all the parts will therefore be painted and decorated. A cheaper option, but requiring decoration, would be a white kit of the same March 701.

The March 701 comes with the narrow head screws part PCH 07 so these will not need to be purchased separately.

B. A donor Scalextric Mclaren M7C.

C. A compatible chassis bought from here:

https://www.shapeways.com/shops/arco_chassis

PLEASE NOTE THIS IS A NON REVERSIBLE PROCEDURE!

2. Preparation of the Policar parts:
Separate the body and remove the chassis from the gearbox by undoing all the screws.

Cut the bottom off the two soldered plugs that hold the DFV to the main body and separate the two.

Cut the link piece off the DFV to form a flat back. You can see the DFV in this photo:

For the rear wing you have two options:
a) if building a white kit I would suggest using the March rear wing (quite similar to the Mclaren) and the March water reservoir.
if converting a donor car or if you don't want to repaint the March rear wing then you will want to use the Scalextric rear wing.

Remove the March rear wing and water tank from the gearbox top. This has been screwed in with a grub screw so insert an allen key and extract it cleanly.

You now have a complete DFV / gearbox assembly.

How to fit the rear wing (if using the original Scalextric Mclaren one):

Simply leave the water reservoir and rear exhaust assembly on the back of the car and skip the next step.

Here you can see how similar the two wings are:

If you want to use the original wing and my conversion piece:

Remove the rear wing & reservoir from the March rear end:

Cut the new Mclaren water reservoir off the Shapeways chassis. You can see it laying on the chassis here:

Give it a paint in silver and black. I haven't done that so it stands out clearly in the photos.

Screw that onto the back of the gearbox using the grub screw previously extracted.

Drill two 1.2mm dia. holes 20.8mm apart and 1.5mm back from the front edge of the wing. Whilst they can poke through the top wing surface as mine do try to avoid them going straight through. This creates a restriction at their end, limiting slightly the upward travel of the posts through the wing and therefore making a stronger joint.

I found to get the wing sitting straight meant that one of the uprights poked through slightly more than the other.

You may need to slightly trim the front most wing posts until they sit on top of the brake disks and the wing has the right inclination:

Once everything is ready the wing should push down into the new water reservoir and straight onto the original March posts. I have glued this all solidly into place making a nice solid fixing.

The rear end is now ready.

3. Preparation of Scalextric Mclaren M7C donor:

Undo the screws and disassemble:

For this conversion I have chosen to leave the front wheels and tyres with the stock axle. Mine are relatively circular and correctly fitted. If you need (due to non centred wheels) replace with the front axle assembly from the Policar March using the small spacers attached to the top of the chassis:

Cut off the plastic soldered plugs holding the rear engine and gearbox detail to the main body including the backs of the radius arms and separate.

You will be left with this piece:

The rear suspension is sometimes glued and may need cutting or prising apart.

The front bodywork needs pulling up slightly forwards as the bulkhead behind the driver that forms part of the engine moulding has been designed to sit inside the back of the bodywork and sort of clips into place. This will need a small amount of force for it to spring out.

Ensure the roll over bar remains attached.

The engine part may stay attached. If so gently prise it off by breaking any glue around the tongue that also links the driver.

Driver removal and cutting.

Remove the driver from the engine assembly. He may need to be cut off but I found inserting a knife between him and the tongue and twisting separated him well. Trim him to shape, doing a few test fits to make sure you've cut enough off. I accidentally cut his lower arms off so had to glue them back on! This shouldn't be necessary if you are careful...…

Put the driver back holding the body upside down, ensuring he grips the steering wheel as before.

This is you donor body complete:

4. Assembly

Screw the motor pod to the rear DFV and gearbox assembly using the small screws part number: PCH 07 and the rear grub screw.

Take the 3D printed chassis. Cut off the two 'spacers' from the chassis using a craft knife if you haven't already done so. These sit either side of the screw point for the gearbox so you can't miss them. You won't be able to screw on the gearbox until you've cut them off underneath. Trim off any sprue remaining and set aside.

Screw the gearbox assembly to the 3D printed chassis.

Thread the wires between the axle guides and fit the slot guide. The chassis can be used with the guide from the donor Policar or a wood guide can be fitted.

Screw the body on top using two of the Scalextric donor screws.

If using the Policar front axle, assemble one side of the front Policar axle with a spacer inserted into the hub. Push that through the body hole. Check that it spins. If necessary slacken off the body screws and adjust body alignment to ensure smooth spinning.

Note that the Policar front tyres have a slightly smaller diameter than the Scalextric ones. This may mean they don't touch the track. If so cut the front screw posts on the Scalextric body down by around 0.5mm to ease the front of the car down. The area of material between the front axle guides on the 3d printed body may also need a little filing or cutting down so the axle spins freely in this case.

Go and have fun!