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Remove the chassis parts from the fret and clean them up. Some chassis have the positions for hornguides marked by half etches. Where they do not, like these, the sides have to be marked and then cut out. The gap required for a Slaters hornguide is 10.7mm (27/64in). The background for the marking is a fat felt tip pen scribbled over the frame. You will note two sets of scribed lines. The inner ones just cut the etched hole at vertical tangents denoting the hole diameter. The outer lines are derived by a simple sum: Slater’s cut-out dimension minus the hole diameter, divided by 2. This gives the off-set dimension either side of the hole. The top edge of the chassis frame provides the datum for the square to rest on to scribe the lines; this must be free of etch tabs. The top of the cut-out is set by the hornguide. The bottom of the guide should be no higher than the bottom of the frame to allow the keeps to fit properly.

The arrangement of the frame spacers may be affected by the horn guides. Here you see the vertical leg of the front spacer needs to move forward. It was removed along the fold line and fitted to clear the horn guide

The same situation occurred at the rear of the chassis. Sometimes a frame spacer sits above a guide. Holes will have to be drilled in to access the ride height setting screw. Mark out and drill before assembly. Having reached this stage I prepare the plastic hornguides for assembly. The feed sprue attachments are removed. Although the holes are sized so that the 10 and 12 BA screws will self-tap into the plastic I prefer to run a tap into the holes to be certain the screws will easily enter the holes.

The coupling rods should be assembled next. It is essential that jointed rods are used with any form of suspension (except when there are only four driving wheels!). The ones in this kit are jointed on the centre crank pin. Other rods are more correctly jointed by a pin joint beside a crank pin. Whichever method is used ensure that the hinge point of the coupling rod is free to move.

A set of rods are essential to setting the position of the hornguides. You have the choice of a chassis building jig or simple jury axles positioned using the rods. I will express no preference.

The photos show how the hornguides and bearing are set up in both cases. The springs over the axles are useful for pressing the hornguide/axle assembly against the side of the frame whilst fixing; in this instance with slow setting superglue. Personal preference is for Slo-Zap. I introduce the glue behind the guide by first rotating the guide so that the two locating webs hold it off the surface of the frame. The glue is applied to the frame on the end of a cocktail stick; the guide is then rotated back so it drops into the slot. With the hornguides in position the remainder of the hornguide components can be assembled and the wheels and rods fitted.

Assembling the small parts can be tricky. I fit the keeps loosely, not fully screwed home. The small H-shaped etch that the spring sits on is fitted on top of the bearing. The 12BA screw is fitted with about 1mm showing above the bearing. Next the spring is added. I stab the spring in the side with a small screwdriver. The blade wedged between the coils, a bit of spit to hold on helps too. With a finger blocking the gap behind the guide introduce the spring and locate over the end of the screw. The other end will then slide into place over the etched seat. The keep screws can then be tightened and the ride height screw set. I usually allow the middle axle about 1mm of extra vertical movement relative to the outer axles.

As the axle centres are derived from the coupling rod centres the wheel should rotate without sticking. For best results ream the axle bushes to 4.8mm dia and the holes for the crank pins to 2.55mm to give good running clearances.

Further chassis details can now be added.

Note. Any axle hung motor/gearbox can be used, but it must be free to move with the axle, so some type of flexible restraint is needed on the motor.

Thanks to Jim McGeown, Connoisseur Models for providing the chassis fret.