So I didn't get quite as far as I planned today. But still managed to get the rear bulkhead and dash hoop made up along with the belly pan frames. A fair bit of time was spent getting the tooling set up, which involved searching through boxes trying to find the right sized rollers for my rolling machine and dies for the mandrel bender. Was also the first time that I have used the rolling machine since purchasing it a year or so back for another project. So that was kinda cool.

I did forego making up templates in favour of 'eyeing-it'. This kind of behaviour can obviously go one of two ways lol. Fortunately the profiles came out okay. The trick is to make the bends up in sections and then chop them at the 'apex' before stitching them together, rather than trying to bend them up out of one continuous piece. You do need to plan your bends and also get a little bit of wastage, but steel is cheaper than time so it's a good tradeoff. There is so much variation between the actual full sized cars that a little 'artistic license' is not going to make a big difference. Plus to a degree I'm limited with the radius of the mandrel bender.

I still need to set the height of the bulkhead and dash hoop, but cannot really do that until the belly pan frames are installed. These need to be in place so that I can get judgement of the overall body height from the bottom of the pan to the top of the hood. Scaling from my overlay the dash hoop is supposed to be correct, but it looks a little too low, which I think is just an optical illusion with the belly pan frames missing.

The belly pan frames are simply small hoops that sit underneath the chassis rails to give the sills that rolled under look and drop the floor down below the chassis. I'll weld some 2mm steel plate to the bottom for the floor and extend the bodywork down to meet the floorpan.

Tomorrow I should get those parts stitched up and take a look at the grille hoop. I have a bit of an idea on how to make up the grille surround, but again I'm going to try and wing-it a little as I don't have the luxury of time to build a buck.

Fixed up the rear chassis section today and got the rear axle mounted up. Mocked up the engine mounting location and tried a couple of difference configurations for the torque converter. I can mount the engine forwards, in which case it would need to be higher to avoid clashing with the drive sprocket, or further back and lower down I'm leaning towards further back as the greater head clearance will make the tail easier to make.

Frustratingly I spent half the day just trying to find the parts that I had stashed. It's been so long since I looked at this project that I could not find everything. Still got some stuff to find.

Tomorrows task is to mount the engine and rear wheels and hopefully get the bulkhead and belly pan frames bent up

Spent a bit of time digging out the Cyclekart from the back of the workshop today to get it ready for The Bend event next weekend.

After taking check of everything I decided to go back to the drawing board with the rear chassis. The chassis had a bit of a twist in it. I'm guessing that it must have pulled when originally welded and I never noticed. So I've cut the rear section off and am going with a raised section with the axle underneath, rather than through the chassis rails.

Steering this week. We’ve decided to make sure it is possible to remove the steering column from the kart if required in the future. To do this, the bearing carriers were attached to plates which are bolted to mounting brackets in the kart. We set up the steering column with the bearings in place before welding the brackets to the kart. Establishing the correct length for the arm at the end of the steering column was a bit of a challenge, but we eventually found a length that works for the steering. A couple of adjustable limit bolts were added to ensure the steering doesn’t go past centre. The steering wheel as it is in the photos is the centre blank which has been machined from aluminium. The wheel will be finished off in time with some timber to form the outer grip. The wheel’s spokes will also be rounded a little to soften up the edges. We’ve decided to use a quick release hub for the steering wheel to facilitate getting in and out of the kart. The unit was found on eBay and has so far impressed us with its build quality and positive function. After assembling the steering some initial adjustment of the length of the control arms resulted in the kart steering quite well. During turns there isn’t any discernible scrubbing of the front tyres. If this style of steering proves to be too ‘fast’ resulting in a nervous ride, we might look at a more conventional steering rack.

Floor pan. The floor pan was build out of plywood with thin ply sides. The pan has about a 10cm tilt relative to the chassis. The pan has been dropped below the level of the chassis to lower the centre of gravity of the car. Two steel rails running crossways under the floor pan provide support. The rails are bolted on to allow the pan to be removed as required.

Steering arms. After getting the front axle into place, we looked at the steering arms. The goal was to get the steering components above the chassis rails to ensure clearance through the full suspension travel. Some CAD work resulted in patterns for the steering arms and their supporting struts. The location of the steering bolt is inline with the steering knuckle axis and the mid point of the rear axle to create Ackerman steering geometry. Some bending of steel and dubious welding and it’s done. A bit of grinding then painting should tidy up the arms. We have fitted a temporary rod between the steering arms to keep the front wheels under control until the steering is completed. There was no discernible scrubbing of the front tyres during testing of the steering.

Front beam axle. With the chassis sitting on its rear wheels and level, the front wheels were propped up so the steering hubs were at the right castor and camber angles for the build. We’ve selected a castor value on the high side of typically recommended values to bias the steering towards tracking stability. With the wheels set at the right angles, a pattern capturing the locations of the bottom of the springs and the steering knuckles was made using fibreboard and hot glue. With the pattern capturing the geometry the beam axle was built up from square steel tubing, steel plate cut to the shape of the curves up to the knuckles and steel strap top and bottom to tie everything together. After the beam was fabricated, we set the wheels up again to check the geometry was right then tacked the steering joints to the beam. With the wheels attached the kart could be rolled forwards despite the wheels not being tied together. We took that as a sign that the castor of the steering will work for us.

Steering knuckles. Axles machined out of mild steel rod and run through the steering knuckle itself. We adopted this approach to ensure there is plenty of support for the axles. Knuckles have nylon bushings top and bottom to provide a bearing surface for the retaining bolts. The angle of the axle looks extreme, but is in line with other builds seen online. Being first time builders, we’ve gone for strength over light weight.

Chassis start. The outline of the chassis was scaled up from photographs and drawn onto a large sheet of fibreboard with the locations of major components also drawn on to check that the build will be more or less compliant with the guidelines for Cyclekarts. The chassis rails are 75x25mm steel box section which where shaped by slicing segments out of the box section to allow the rails to bend and follow the outline drawn onto the fibreboard. The rails were then secured to the board and the segments TIG welded back up to fix the final shape. This approach was selected due to the lack of facilities to roll form the rails.
Second image shows the chassis from the rear with engine supports in place.

Mail call...

Found these springs from a Kawasaki Mule and thought they might work for a Cyclekart. Unfortunately the eye-to-eye distance is a little long at 750mm. Material is 6x50mm so also a little too heavy duty. They have three leaves, two of which are usable. I'm figuring that I can weld some mounting eyes to the second leaves which are 600mm long to make another pair of springs. The longer springs could be chopped down and used as 1/4 ellipticals on another build.

Was hoping that these could be a potential source of springs but alas the search continues.