blockquote>Adrian_Thompson wrote:
... By the look of it this guy knows a hell of a lot more than mere mortals such as me so I'll shut up. Well no I wont. It looks like he's going to have a lot jounce movement but very little roll available. That would lead to effectively sudden infinite roll resistance which could prove very scary. I wonder how he's going to deal with that?
I wouldn't assume this guy knows more than mere mortals. I think he's good with CAD, CNC and welding, has a subscription to Racecar Engineering and likes to imitate things he sees in it. Look at his rear suspension for instance. Unless I'm missing something, he's probably got about 3 inches of suspension travel total, probably less.
Starting with the bellcrank on his horizontal shock design, he's got the long arm of the bellcrank attached to the shock and the short arm attached to the pushrod (thats what I'm calling the linkage that goes between wheel spindle and the bellcrank). That means that if the pushrod moves 1", the shock is going to more more, limiting the potential travel of the pushrod. If he had reversed it, the pushrod could have moved 2" while the shock only moved 1", for example. Next, it looks like the arm to the pushrod is only about 2" long, giving a 4" maximum theoretical movement of the pushrod. However, if he hits a bump and the bellcrank rotates 90 degrees, it will hit the crosspiece of the chassis and stop. The arm connected to the pushrod is mounted at about 45 degrees below horizontal, so it can only move down 45 degrees before bottoming out. But the pushrod is also at an angle (approx 25 deg) further limiting the amount the wheel can drop before motion stops (the motion will stop when the pushrod and the bellcrank arm make a straight line - any further pulling by the pushrod will not rotate the crank any more). So the bellcrank can rotate 90deg in one direction, and 20 degrees in the other. This limits the movement of the top of the pushrod from 4" down to about 3.2". Now, instead of mounting the pushrod to the suspension and using the lever effect to gain some wheel travel, he mounted it directly to the hub/spindle, so he has a 1:1 motion ratio. The 3.2" of pushrod travel limits the wheel to 3.2" of total travel. I'm going to assume he'll have it set up for 2" of compression and 1" of rebound. Is it just me or is that ridiculously short? Had he connected the pushrod halfway up his suspension control arm he could have doubled his suspension travel. Since he's using fancy coilover shocks, buying a spring with twice the spring rate would have been very easy and would have maintained the same wheel rate if he wanted too. Or he could have gone with something a little softer and still not worried about bottoming out. Maybe I've underestimated the length of his bellcrank arms, but still, even if they're 3 inches long, he's still only going to get about 4" of total travel.
Here's a link to the pic showing the bellcrank. I didn't want to hotlink it because it would make my oversized post even bigger. VW Suspension Pic<
Is this car meant to be driven in anger, or is it a show car?
Bob
