Original plan for driving the trike was with a rear mounted engine and a swing arm. (Simple)
In order to fit it into the available space, I was planning to extend the motor drive past the front of the wheel and put the Torque Converter on the other side of the wheel. This was not going to be a problem as one of my 'donor' engines is from a portable generator. These have a tapered drive into the alternator rotor, press the rotor apart and away we go, extended shaft, (Simple). Next step was a short swing-arm pivoting in-line with the output sprocket of the TC. (Simple... sketch attached). For proper alignment with the wheel sprocket, I would need to place the drive sprocket on the inside end of the TC. (Simple) Apparently, this is possible with a genuine Comet TC. My Chinese clone, TAV20, on the other hand, has a 5/8" shaft through the rear pulley and drive sprocket, expanding to 17mm through the alloy bearing support. (Not so simple??) New Plan in development.

Unfortunately yesterday was raining pretty hard so we spent some time drafting up the adaptors for the wheel hubs and cutting out some parts on the CNC plasma cutter, which kept us in the workshop. Two new skills unlocked lol. Unfortunately there just wasn't enough room to lay the chassis out inside so we decided to put that off until today.

The rain held off today so spent some time today getting the chassis welded up. We decided on the chassis width based on the width of the rear axle, my CK and the width of the front spring. It is 50mm wider than my CK. After we levelled up the trestles, Locke checked the chassis for square and tacked it up. We added some gussets to the front corners to help improve the strength, as there will be a lot of twisting force from the transverse front spring.

Also took some measurements for the front spring hanger ready for a trip to the steel shop tomorrow for supplies. We also need to procure the parts to make up the front beam and vertical links.

So this is the progress so far....All work done by Locke with a little guidance of course...

He marked out a basic chassis design. It has a large dogleg at the rear to allow the axle to sit underneath. This puts the chassis rail about 100mm above the ground which keeps the C of G nice and low. The front will have a spring hanger welded to the cross member for the transverse spring. The spring itself will be inverted, a common modification on Austin 7's to lower the chassis height, so he will be mimicking this with his build.

He stripped the tyres off of the rim, stripped out the hubs and marked out the chassis, which he the cut out in the workshop. Then we laid out the chassis rails and he welded them together. Definitely a natural, his welding is far better than my very first attempts. He also reoriented the torque converter on the engine.

Skills so far - Design. Marking out. Cutting. Deburring. Tyre removal. Hub disassembly. Torque converter assembly. Welding, and of course standing back and admiring your work. lol

Sliding Hub Suspension - Part 2

Previously, I described how the pillar doesn’t need to be inclined rearward to produce caster.
This time, I will try to explain the ‘drawback’ of pillars that are inclined to the centreline of the trike. (below is a pic of recommendations for a 4 wheeler.)

The hubs slide up the pillars. If the pillars are narrower at the top than the bottom this will produce Toe-in on bump and Toe-out on rebound, (assume steering arms at the rear). Bad enough for stability in a straight line, now consider the Bump Steer produced by only one wheel compressing on a bump. Even worse, the strange alignment caused by the trike rolling in a sharp or high-speed turn. Outside wheel compresses causing Toe-in, inside wheel extends and Toes-out. Even if they somehow manage to ‘balance each other out’ your Ackerman is shot and the vehicle is no longer pointing in the same direction as your input at the steering wheel.

But! But! What about the Scrub Radius?
Scrub Radius is the distance between the steering axis and the centre of the tyre contact patch. It can be +ve , -ve or zero.

Scrub ‘sounds’ Bad… so zero must be Best!!???
If you manage to produce zero, don’t cheer yet. You have now got SQUIRM.
As the tyre tries to turn around the centre point, one half of the contact patch is scrubbing forward and the other half is scrubbing backward. Tyre wear and instability result.

Negative is less than zero….. so -ve must be Best!!??
-ve has some advantages for modern cars, but not so much for Cyclekarts. In FWD cars -ve scrub is less affected by torque steer. Also brake inputs, helpful with ABS and failures in split systems or in the case of a flat front tyre.

So...+ve? Older cars had +ve scrub. It helped parking without power steering because the wheel could roll as it was steered. +ve scrub provides more “feel” to steering inputs because of leverage caused by the radius.

Conclusions: For me, Vertical pillars and some Positive scrub radius.
We have skinny motorcycle tyres, minimal weight, and no front brake issues to consider.
If I want to (or need to) reduce the scrub, I have another option. I can use stub axles that are not perpendicular to the pillars to create positive camber, this will bring the bottom of the wheels closer to the bottom of the pillars. It is a classic Morgan trike look and I might do it just for that!

Cheers, Daryl.