Another damper mount option

Credit to Dave F for pointing this out.

I may be able to get some better packaging options by using a second billet bulkhead to mount the damper to.


That may give me some much improved options for load paths, both through the bellcranks and into the bulkheads themselves. As an added bonus I might be able to shoe-horn in a damper with 3" of travel. At the moment I am using one with 2" of travel.

Why one damper length over another? There are some pros and cons related to overall motion ratio (inches of wheel travel to inches of damper travel). I'll get into that later if I haven't already. I have to sit down and think about that, figure out if a MR > 1 or < 1 is better in terms of minimizing the effect of damper friction.

In any event, there are some issues associated with putting a 2nd bulkhead back there. Namely, it might not be great for bringing in that front roll hoop bracing. May also make getting fasteners in there a bitch. We'll see.

Front rocker assembly

For those of you who have not had the joy of doing suspension design, particular on a tube-frame car, this crap is a mental challenge. Either that, or I'm mentally challenged, or both. The challenge is that ideally, everything needs to be co-planar so that the bell crank is loaded in 2-d shear. Once there is misalignment among the components you get ugly bending moments which dramatically reduces the stress limit factor of safety on the bell crank.


The following points need to all be (roughly) in the same plane:

1. Rocker pivot
   
2. Rocker - damper connection
   
3. Rocker - pushrod connection
4. Rocker - antiroll link connection
   
5. Damper mount / pivot
   
6. Pushrod / lower control arm connection
7. Antiroll link / antiroll bar connection

Given that 3 points define a plane, you're trying to design a really over-constrained system. Replacing one of the frame elements with that big billet aluminum piece should help a good deal with making sure everything's aligned. The '68 Lola T150 features something similar on the rear of the car, but not quite for the same purpose. The damper and rocker mounts are in single shear which isn't ideal, but you can live with it. The mounts are fairly stout, but still not heavy.

At the same time you're getting everything in plane, you have to attempt to..

1. Have good load paths
2. Meet your targeted installation ratio and progression
3. Make sure none of your components intersect the frame, control arms, driver, or other such things.
   

I haven't even taken a look at installation ratios yet. I'll have to see how terribly hosed those are and make adjustments. For now I wanted to have something where I knew I could physically locate the damn thing. All of this helps to locate the front anti-roll bar (FARB) assembly, among other things. In this case there will be another pickup point on the front end of the rocker, which will shoot a link forward to the FARB assembly. My intent is to have both the FARB and RARB adjustable from the cockpit.

Oh I hate this part of suspension design

Moreso than anything else, getting the push/pullrod, rocker, and damper oriented in a good way on a steel spaceframe is a total bitch.

Caster change a la Lola

Been quiet around here. Work has been intense lately! Also, I'm working on some 'big stuff' for this car which is kinda long term.

Anyway. Wound up taking apart, moving, and re-assembling a 1968 Lola Indy car with a couple guys. Pretty slick little car. Fit and finish wasn't all that great in some places, but it had some cool design features (including an aluminum monocoque and all wheel drive!) and modularity.

Hadn't thought of changing caster this way...



So I borrowed the idea...



There were a few other crafty design features I may borrow. Most of all I'm very keen on having everything from the main roll hoop back be modular and easy to service. One of the biggest pains in the ass of all of our FSAE cars was getting the engine and assorted drivetrain components in and out.

The challenge will be getting the rear end of the car to be modular and serviceable, while maintaining high axle-to-axle stiffness and keeping the engine semi-stressed.