Updated Sierra Uprights

I used Sierra uprights with standard mushroom top hat adaptors. Using a medium Swing Arm radius (it’s going to be a daily driver) and a top arm closer to 2/3 the length of the bottom arm, I came up with :

image: No body roll

image: 5 degrees roll

image: Camber vs bump and droop

image: Roll Centre Vs Bump and Droop

image: The New Modified Design

Top Pivot Point
(from centerline or car)
Bottom Pivot Point
(from centerline or car)
Upper Control Arm
Angle & Length
Lower Control Arm
Angle & Length
581, 386 619, 186 4.75°, 309 0.9°, 420 –0.7 to –1°

I tried hundreds of combinations of upright heights, A–Arm lengths etc, but only confirmed what I had read in books. Some small changes had huge effects, others only marginal. Also, the phrase ‘Stealing from Peter to pay Paul’ came to mind. It is very easy to get dragged into perfecting one goal, only then to see that another goal has been utterly destroyed. Many of my goals would only be achievable on a super wide car, with zero ground clearance, long A–Arms and huge uprights (Formual 1 racer). Ride quality would be poor and driver involvement huge. My experiments also pointed out that for certain set-ups, give and play in bushes would potentially have huge effects on calculations. So I edged towards ‘middle of the road’ on every goal.

For goals, I decided :

  • Keep changes in Roll Centre height to a minimum.
  • Scrub in bounce and droop minimal.
  • Slightly increase the swing arm length.
  • Increase bottom arm length.

At the front, the McSorley 442 has a narrower bottom chassis than the standard Locost. This is a handy piece of design as the mounts can be placed reasonably easily.

At this point, I knew this setup would work ‘ok’, but the design was still trying to make good of parts essential designed for a larger family car.

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