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Step 3Machining wheel sprockets
This part of the vehicle really depends on the sprockets your using. I worked out I needed a 5.2:1 ratio for my drivetrain. I had to achieve this ratio in just one step down. This wasn't possible due to the limited sprocket selection I had. So I ended up with an 8 tooth motor sprocket and a 40 tooth wheel sprocket. This is a 4.44:1 ratio but I thought that the motors would be able to handle the extra load so I went for it.
With my sprockets (mainly the wheel sprocket) I had to machine the bosses (the part of the sprocket that protrudes out). This requires:
- A centre lathe
- Measuring tools
- If possible Vernier Calipers (great for accurate measurements of diamters and bores)
The machining was needed because bolts were to be used for fixing to sprocket to the wheel and the boss was too large fit the bolt hole pattern in the wheel hub. You get me?
1. Mount sprocket into 3 jaw chuck in lathe
2. Turn the boss down to 40mm in diameter and 12.5mm in depth (was 25mm in depth and 60mm in diameter), keep checking the dimensions with the vernier calipers until you can make your final cut
3. Remember when facing off the face' of the sprocket the surface has got to be as smooth as possible.
For the motor sprockets it also depends on the sprockets your using, the motors and what sort of spindle the motor provides you.
On my motors their was a flattened egdge to it so I could use a grub screw and a thread in the sprocket hole to fix it to the spindle.
For this you need:
- Set of taps
- 10mm reaming tool
- Bench vice
- Drill bits
- Pillar drill
- Vice clamp for drill work
1. Tap the sprocket hole using the taps, firstly with the taper and then finish with plug (No pilot hole is required here
2. Then tap the hole for the grub screw (drill your pilot 1mm smaller than the tapped diameter)
Remember that clamping the motor sprockets are tricky and you should be able to use the teeth to hold the sprocket square in the clamp.
This is just what I did by the way. If you happen to make this yourself you might using keyed shafts, grub screws like mine, bolts, pins or anything else that lets you attach the sprockets.
I also had to make sleeve for the wheel bolts. These help space the wheel sprocket from the tyre to stop rubbing from the chain. These are simply round bar with a hole bored out from it. I cut the bar to length (8 in total, 50mm long) and then bored out the 8mm hole for the wheel bolts.
DRILLING HOLES FOR WHEEL BOLTS INTO WHEEL SPROCKETS:
You need a:
- pillar drill or a bench mounted hand drill
- 8mm drill bit (bolts for my wheels are that size)
- vice clamp for drilling
- scriber
- centre punch
1. Mark out the holes with the scriber (I cheated and took apart my wheels so that I had one half of the wheel hub in which I used the bolts for marking out on my sprockets
2. Securely mount the sprocket with the vice clamp and then drill pilot holes
3. Drill holes with final size drill bit
SORRY THERE'S PICTURE FOR THE SPROCKET HOLES BUT ITS FAIRLY SIMPLE
With my sprockets (mainly the wheel sprocket) I had to machine the bosses (the part of the sprocket that protrudes out). This requires:
- A centre lathe
- Measuring tools
- If possible Vernier Calipers (great for accurate measurements of diamters and bores)
The machining was needed because bolts were to be used for fixing to sprocket to the wheel and the boss was too large fit the bolt hole pattern in the wheel hub. You get me?
1. Mount sprocket into 3 jaw chuck in lathe
2. Turn the boss down to 40mm in diameter and 12.5mm in depth (was 25mm in depth and 60mm in diameter), keep checking the dimensions with the vernier calipers until you can make your final cut
3. Remember when facing off the face' of the sprocket the surface has got to be as smooth as possible.
For the motor sprockets it also depends on the sprockets your using, the motors and what sort of spindle the motor provides you.
On my motors their was a flattened egdge to it so I could use a grub screw and a thread in the sprocket hole to fix it to the spindle.
For this you need:
- Set of taps
- 10mm reaming tool
- Bench vice
- Drill bits
- Pillar drill
- Vice clamp for drill work
1. Tap the sprocket hole using the taps, firstly with the taper and then finish with plug (No pilot hole is required here
2. Then tap the hole for the grub screw (drill your pilot 1mm smaller than the tapped diameter)
Remember that clamping the motor sprockets are tricky and you should be able to use the teeth to hold the sprocket square in the clamp.
This is just what I did by the way. If you happen to make this yourself you might using keyed shafts, grub screws like mine, bolts, pins or anything else that lets you attach the sprockets.
I also had to make sleeve for the wheel bolts. These help space the wheel sprocket from the tyre to stop rubbing from the chain. These are simply round bar with a hole bored out from it. I cut the bar to length (8 in total, 50mm long) and then bored out the 8mm hole for the wheel bolts.
DRILLING HOLES FOR WHEEL BOLTS INTO WHEEL SPROCKETS:
You need a:
- pillar drill or a bench mounted hand drill
- 8mm drill bit (bolts for my wheels are that size)
- vice clamp for drilling
- scriber
- centre punch
1. Mark out the holes with the scriber (I cheated and took apart my wheels so that I had one half of the wheel hub in which I used the bolts for marking out on my sprockets
2. Securely mount the sprocket with the vice clamp and then drill pilot holes
3. Drill holes with final size drill bit
SORRY THERE'S PICTURE FOR THE SPROCKET HOLES BUT ITS FAIRLY SIMPLE
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