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Hesketh 304 Policar gearbox conversion for Fly model

How to:
So, as ever you will need a donor car. There are several models available, I am doing the Alan Jones car.

This conversion is non-reversible for the Fly donor body.

1. Disassembly:
Disassemble the Fly car by removing all screws. Set aside the rear wing and screws.
The whole chassis and running gear is not required.


The top body requires further separation. Cut the solder joints to remove the gearbox top from the body, the air box from the gearbox and also the roll over bar.




You are left with the front body, the airbox, the screws and the rear wing as shown:


The underside of the car looks like this:


2. Assemble the other components:
This conversion requires the engine and gearbox detail from the Policar Lotus 72 as well as the Policar complete gearbox. It may prove more economic to use a complete Policar Lotus 72 as a donor for parts, especially as the detail comes ready painted.

A. You will need a complete Policar gearbox (wide type). This can be assembled from all the components or more economically bought as a single set (piece PCH03as-51z17).

B. Engine and gearbox detail parts required:

C. Rear wheels and tyres
The aluminium hubs available through Pendle Slot Racing, part PCS-321413 are a good option as the hub in this case does not get in the way or look too bad. They also have F22 compound tyres compatible with these wheels, ref. PCS-321413T.
The combination is slightly too large in diameter when assembled, presumably to allow them to be glued and trued.
I have also used Ostorero Lotus 79 wheels and tyres for these type of conversions.
The design parameters are that they should be about 21mm dia. and 14-16mm wide.

D. Front wheels and tyres
The chassis is designed to use the Policar F1 front wheels code PWH1218-Pl. These are plastic and push fit on a axle. If you are using a donor car the front wheels from the Lotus 72 are the same.
Use tyres ref: PT1088-C1.

E. Compatible Chassis available here:

Buy the Fly Hesketh conversion chassis.

F. Front axles x 1, or equivalent.

G. Guide, braid and wires. I recommend a thin wire, very thin braid and guide CH85 (screw in) although clip in CH66 will also fit.

3. Building the Policar engine and gearbox.
To assemble the detail parts if you are not using a donor Policar Lotus 72 see the instructions here:

I would recommend painting these parts before further assembly.

If using a donor engine/gearbox detail this can be cut off the back of the Lotus 72 behind the cockpit. In this conversion the forward facing tab is not required.

If not using a donor gearbox, cut off the forward facing tab as shown:


Now remove (or do not assemble) the air trumpets from the top of the engine detail. They should come away easily by pressing them together but otherwise cut them out from below and possibly from above.


The rear wing is removed by screwing out the long grub screw that holds it in.

The extremities of the radius rod detail should be removed to allow the rear wheels to fit close enough together.

Ensure you also set aside for re-use the rear exhaust ends that fit in the back of the gearbox to complete the look of the new model.

4. Preparing the new chassis:


Cut the mounting bridge from the main chassis by carefully cutting the thin sprue connections.

Once detached trim the sprue from both the chassis and the separated part.

5. Fitting the gearbox and engine detail to the new chassis:

Remove the front most mounting hole from the Policar gearbox as this is not needed for this build.
Screw on the gearbox to the chassis using one front screw and two rear screws.



Take the mounting bridge part and push the rear lower mounting pillar down through the top of the engine detail part.

Glue or solder this in from below as shown. Dry fit in place first to make sure the alignment is perfect.



Now dry fit and then glue the airbox through the 4 mounting holes in the top of the bridge plate.

Dry fit the bridge over the chassis/gearbox assembly. It should look like this:





Cut off the rear of the top gearbox detail part as shown.


Use a 6mm long M2 grub screw or other long screw to screw on the rear wing to the rear of the bottom gearbox.




6. Fitting the body to the chassis.

Cut out the bottom of the seat until it looks like this:


In doing so the driver will be released from his seat. He can be slipped downwards being careful not to break off the steering wheel. On my model the steering wheel was not glued in.

Remove the driver and cut him until he fits to the chassis / motor like this. It might take some trial fits to make sure he sits low enough down.




Cut the rear mounting posts off inside the body as shown:

7. Final Assembly

First fit the guide, braid and wires. Then assemble the front axle. Ensure the axle runs freely. If it is a little tight due to printing swarf run a 3/32 reamer through from side to side. The axle should spin freely without excessive movement. Grub screw adjustment holes have been provided but these are probably not necessary.

Assemble the body using the three screw holes from under the body.

The front one goes through the chassis, bridge and into the body. The two rear screws go through the chassis into the bridge.



8. Go and drive!

Thank you for your custom.


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