Due to variation in supplier your kit may come with either a white injection moulded drive gear or a black profiled gear. If supplied with the black gear then you do not need the 3mm spacer plate but use 1 no. 5mm washer on every bolt between the gear and the back of the wheel.

• The wheel and nylon gear need to be fixed together. This can be achieved through several ways but for strength and ease of disassembly, (in case it needs to be replaced) we recommend bolting it to the wheel.

• The nylon gear is now supplied with three 5mm holes pre drilled. The holes correspond to three centre marks on two of the wheels.

	Above - mould mark on the nylon wheel. This face goes towards the wheel/spacer	Above - nylon gear and 3mm spacer

• Now drill 3no holes on two of the wheels to take 5mm tap (4.2mm). Drill straight through the wheel. If you are confident at tapping threads then you may not want to drill straight through the wheel but for most of us it is easier to tap a thread in an open hole. The hole in the outer face of the wheel can be filled later before painting.

• Using a 5mm tap bit thread the three holes in the wheel.

• To stop the fixing bolts distorting the nylon gear, insert the 3mm spacer disk between the wheel and the nylon gear. The centre of the disk may need to be lightly filed to fit onto the nylon gear. There is a mould mark on one face of the gear (see picture above) this face goes towards the wheel. The reason for this is that the centre hub on the other side is always constant. The hub on the disk side varies and could affect the motor mount spacing.

• Assemble the wheel and gear on to the axle. Applying thread lock to the three 20mm x 5mm bolts, then bolt the gear to the back of the wheel.

• Remove the axle after tightening the last bolt to avoid it getting stuck by any stray thread lock.
  

FIXING THE WHEELS TO THE AXLE

Thread loc is a wonderful product and in theory is strong enough to hold the wheels on the axle without any other type of fixing. In practice we have seen wheels break loose and spin on the axle. We therefore suggest one of two methods

1. Press on the wheels

2. Key in the wheels

Method number one is preferable as it allows the wheel set to be disassembled by simply pressing off the wheel. The disadvantage is that you require a good press with a large throat .

One of the supply options it to supply the wheel set pre assembled - see price list for current price.

Pressing on the wheels

Before pressing on the drive wheel, slightly loosen the three bolts on the nylon gear. This allows the gear to centre on the axle rather than the bolts. Apply bearing fit to the inside of the wheel and the axle shaft. Only press the driving wheel on at this stage as you need to build the motor assembly on the axle.

When pressing on the wheel place the wheel on the base plate of the press and press the axle down. Do not push the axle in in one go but release the pressure after the first few milimetres. This makes sure that the axle is going in straight.

Keying in the wheel

While some manufacturers don't key their wheels on we would thoroughly recommend it, especially given the amount of power going through the wheel sets. To achieve this you will need to file a flat spot in the wheel centre and a corresponding flat spot on the axle. The flat on the axle needs to extend past the wheel so a wedge can be driven in. See picture on the right.
	Using a piece of 1mm steel strip cut a 15mm long piece and file one end down. Continue to file until it fits tightly in the slot between the axle and wheel and lock the two together. Now take the wheel off the axle, clean the all the surfaces with a grease free cloth and apply thread lock to the axle and wheel. Assemble and align the slots. Apply a small amount of thread lock to the slot then drive the wedge into the slot. NB the threadloc may be oil tolerant, but a clean surface will give a much stronger bond.

One of the problems is how to strike the top of the wedge. For the first 3 wheels you can use the fourth wheel as a hammer. Use a pair of fine nose pliers to stop the wedge from bending (rather slow it down, as it wil bend). For the last wheel follow the instructions below.

The above procedure is repeated for the other wheel once the motor assemble has been slid on to the axle.

Before fitting the other wheel make sure the bronze bushes are well oiled before applying threadloc to the wheel. This should stop any stray threadloc from sticking the motor mount bush to the axle.