Anyone running a large scrub radius?

Hi all,

Having been looking recently at steering geometry for our latest project, I've been looking into running a 0° steering axis inclination (kingpin angle viewed from the front of the cast). It results in a scrub radius of ~85mm, but it does greatly simplify construction, reduce cost and takes up little space given that space for the steering mech is very limited

From what I can see the downsides of such a large scrub radius are possible brake steer if braking is unbalanced and kickback when going over bumps. I expect a damper can be used to alleviate the latter.

Status Quo has a SAI of 16° and scrub radius 15mm, and is easy for even our youngest drivers to handle. Have any other teams experience with running fast cars at large scrub radii? Most of the internet advice relates to road cars only.

Dan

Comments

  • Coyote MK1 had the same set-up as you describe but I think the scrub radius was more like 65mm - 70mm. I don't recall any drivers complaining of the steering being too heavy but it was definitely twitchy under braking.

    SG1 has a very easy to build steering hub.

    http://greenpowereasybuild.blogspot.co.uk/2016/05/construction-day13-steerings-hubs.html
  • Hmm, I think I will have to move the hub closer to the kingpin to reduce the scrub radius a little, as well as a slight positive SAI, even if just to ensure the tolerances in the manufacture don't cause it to drift, negative causing unstable straight line handline.

    Thanks for the link, very interesting to see what can be achieved with only the most basic of tools. I should hope that Greenpower will be including references to your work on SG1 in the new "How-To" guides. I'm not a huge fan of kit cars being the best way for a team to start out
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