Duke's'72 Carbed KA project

[S15DET]

Very nice! In a turn, the up or down force on this very link is obviously very high, and once the steering is off-center, the force of the bar will be translated to a turning force at the strut. But, will the two sides cancel? If so, this is a great solution, and it just may, I'll have to think about this one. I'm anxious to hear your evaluation after more miles. Mark the position of the clamp to see if it turns with use.

[duke]

My thinking is that the turning force is very minimal when compared to the other forces being transmitted back though the steering wheel that it is not noticeable. I am going to mark the mounts to see if they rotate any, but I think that they are pretty tightly clamped in there.

Here are some more detailed shots of the mounts, showing the pinch bolt and how the ride on the adjuster nut.

[JordanTr]

Great solution Duke. I really like where you went with this!

Glad to hear it seems to be working out for you so far. Have you done the math to figure out approximately how much stiffer the ARB is now due to the change?

Should be just the ratio of the radius of the arcs that the sway bar link travels methinks?

[duke]

The roll rate at the wheel increased by 30% with this change. I am aiming for a roll rate similar to the big bar Canadian setup (300# springs, 1.125 solid front bar mounted in the stock position) and with this set up (350# springs, 1" solid bar mounted to strut) I am about 38 lbs/in away.

On the topic of the sway bar influencing steering force while cornering, I made a free body diagram (haven't done one of those in like 8 years) and as far as I can tell the rotational force of the links on the struts oppose each other. This goes along with what I experienced while driving the car with this new arrangement.

There is an auto-x event this Saturday, I'm just hoping it will be dry so I can test out the new links in anger.

[Sleepys-14]

Wish you the best of luck. And you did a fantastic job on the swaybar/strut mounts. I love when people start thinking outside of the box when it comes to simple solutions. You sir, deserve a beer.

[duke]

Just got notice that the autocross tomorrow is cancelled due to the threat of rain. Well, I guess I'll have to wait another couple of weeks to see how the new mounts work with race tires.

[Sleepys-14]

You guys dont race in the rain? Even in my 510, its still fun. Its definitely slower, but its much more challenging.

[duke]

We do sometimes, but I guess not today. We had a wet event last year and I'm pretty sure I was sideways more often than not! I was good fun though.

[Byron510]

I did a trackday last fall that started with rain. Your right Sleepy, it does let you know any imbalances in the chassis at much lower speeds. In my case I kept having the front right brake lock up, it wa consistent, so I added a turn on the threaded collar to put a little more weigh on that wheel and it seamed to balance the braking up front side to side. That when the track dried up for the last session, the. Are felt better than ever. Something to be said for corner weight set up I guess.

Byron

[duke]

There was another auto-x event this past Saturday. To cut to the chase, the new modifications to the front sway bar mounts worked just as I had hoped. The car was much more controlled and neutral, and the inside rear wheel spin that I was experiencing earlier this year was totally gone. The course was very fast and flowing with a long slalom (which was also very fast, I was taking the whole slalom flat out and shifting into third in the middle). It the whole course was so fast that I only used the brakes once, instead choosing to try and carry as much momentum as possible. In the morning session I was able to set the second fastest time (the only car faster was a Van Diemen Formula Ford who was about 1 second faster than everybody though out the day). To say I was happy with this result would be an understatement. In the afternoon "fun run" session I continued tested a few different tire pressure setups as what I was using at the last event didn't feel good with the new car setup. It was very interesting to see the difference that 1-2 psi made in the feel of the car.
I am very happy with my current setup. It will be interesting to see how it works on a tighter course, but on a fast course like the one on Saturday, I don't really see much room for improvement.
Here are a few pictures from the event. If you compare the corning attitude of the car to the pictures from previous events, it is obvious how much the body roll has been reduced.









I'm hoping to corner weigh the car before the next event and I may also be replacing the engine in the near future because the one I am currently running is no longer holding very good oil pressure. The next event is in a month so hopefully I will have the time to get this all done by then.

[defdes]

Congrats on the improvement, that's looks as flat as flat can be. Once you scale the car it will only get that much better.

[bertvorgon]

Yah, that looks really good now!

Biking and car racing..."Momentum is your friend!"

If the car felt "neutral", that to me is the best you can do, given that if you need to, you can use the throttle to step the rear out.
I usually tried to tell my students, if you are getting too much understeer, slow down, you WILL be faster.

It's all in the roll control and weight transfer! good job.

[defdes]

Biking and car racing..."Momentum is your friend!"

Brakes just slow you down!

[bertvorgon]

BRAKES,,,what are brakes.........???

[Sleepys-14]

Glad to hear the front bar mods worked the way you wanted. I am thinkin of stepping up to a 325# or a 350# like you have. I currently have 300 in the front and seems just a bit on the soft side, as the front bottoms every once in a while on compression bumps mid corner.