They look great Jim - like authentic car parts.

Just remembered that I posted a drawing of the Gemini king pin, in case it’s useful… http://www.cyclekartsgb.com/build-journals/bugatti-type-37-build/msg1442/#msg1442

Perhaps these would help?

https://www.okeparts.com/products/complete-pair-diy-stub-axles-for-go-kart-drift-trike-trolley-toylander

If it's any comfort, (probably not because I don't know what I'm doing), I am also using 16 degree kingpin inclination, 6 degrees castor, and 8mm steering rods, so we are at least in the same boat!

[ Guests cannot view attachments ]

I think the geometry is close to what a lot of other karts are using, so there shouldn't be an issue there. With regards to the steering rods I just measured  those on my trike at 13mm, which is a Mk1 Escort rack. Given the difference in size and weight I don't yet see any need to worry about my decision to use 8mm, though time will tell, it shouldn't be too much trouble to upgrade to 10mm of there's any sign of bending or stress.

Peter

If it's any comfort, (probably not because I don't know what I'm doing), I am also using 16 degree kingpin inclination, 6 degrees castor, and 8mm steering rods, so we are at least in the same boat!

Can you swim?

Seriously though, thanks Peter. I'll stick with the plan.
Nice front axle by the way.

Beware of changes to caster that your spring set-up can introduce.  On an earlier version of the Bugatti, the caster decreased significantly as the springs were compressed.   So are the numbers right….it depends, but probably.

Difficult to say, partly because it depends on the length of the spring too.    There are other factors that influence the choice, such as the camber and the shackle angle changing the effective rate of the spring (the angle "softens" the spring).  Also, remember, many (most?) cyclekarts are rear biased in terms of weight distribution.

What length and camber springs are you thinking of?

I assume you're doing longitudinal springs (not transverse), so yes, the shackles that connect one end of the spring to the chassis and  allow for the change in length as the spring gets compressed.

It's also possible to use trunnions that allow the spring the slide through - see Nic's Bugatti or Marek's Delage.  If the original car has them, as in these two examples, then worth considering, but it's the more complicated approach.

Given stiffness is proportional to the cross sectional area 35x5 will be 25% stiffer than mine and 40x4 will be 20% softer than Graham's (springs!).  I suspect any of them will be fine.   I think it's easier to stiffen the set-up than to soften, so maybe err on that side.  Just my opinion.

Most are just a bit wider than the chassis rail so that shackles are an easy make item. I have softened spring in the past by cutting width down with the trusty 1 mm disc in the grinder.