woensdag 16 maart 2022

Maximum lateral G-force in a WAW

 I got a question from WAW554 owner H. Sj√∂berg, that I was never asked before. I thought it would be interesting to preserve the (lightly revised) conversation.

Q: What is the maximum lateral g-force on a WAW, before it is tipping over? (Typical for open trikes are 0,3-0,4 g).

A: Cornering ability of a trike is relatively high as the center of gravity can be moved considerably: you can hang into the corner. Much difference as well between, say, a VTX and an Adventure.

In a velomobile it would depend on the width of the rider versus the interior - how much wiggle room the rider has. The WAW is just wide enough for me but even then it matters a lot if I shift my weight actively into the inside of the corner, or not.

I just laid out the geometry on my WAW here - which happens to be a custom edition with narrower carbon side beams so I have more space at the shoulders.
If I consider the static center of gravity cG at my belly button, as is a conventional rule of thumb in HPV science, and lay it out on the triangle formed by the wheel base, then cG is around 30cm high and 20 cm away from the line formed by the contact points of a front wheel and the rear wheel. Looking at the vectors that would mean a maximal lateral acceleration of around 0.6 G.

However in real and extreme cornering circumstances, we can shift cG down and inward a lot. Intuitively I'd think a 45° vector (1G) would be the absolute maximum, with 0,8G a reasonable estimation for intense but practical use.

In my experience, cornering speed of the WAW, the Quattrovelo (wider but higher) and the MilanSL (narrower but lower) are similar.
Hans adds: 
a more complete table for a Clinometer:

Lateral g = Grades °
1.2 g = 50° < Limit for extreme sports cars
1.1 g = 48°
1.0 g = 45°
0.9 g = 42°
0.8 g = 39° < Limit for normal cars (typical)
0.7 g = 35°
0.6 g = 31° < Limit for WAW
0.5 g = 27°
0.4 g = 22° < Limit for trikes (typical)
0.3 g = 17°
0.2 g = 11°
0.1 g = 6°