harrisonrick

what a minute here...you sound like you know a little about engineering stuff...

Brian A.

I have 800lbs front springs.

Chads996

I know of some racers using up to 1000# springs. Overkill, IMO. But, some are doing it. I would also assume a race car could exceed 1.25g.

Perhaps some discussions with the racers would be in order?

C.

vt951

Thanks for your feedback, guys.

I guess I could use 1000# springs and 1.5g cornering to be safe, but if that ends up causing me to make it too heavy I may dial it back. I will be using a safety factor in the design (not sure what factor to use yet). I have a feeling this design will be fatigue limited rather than static load.

I'll also try lower springs rates with the stiff sway bar, as that might cause even higher bending loads in the arms (I think looser springs will cause the higher sway bar forces).

Cory M

You are on the right track looking at the deflection. You will probably find that a design that satisfies deflection limits will also meet strength requirements. Don't forget to consider impact loads - potholes, kerbs, dropping it off the trailer, etc. You could probably use 3-5 g's as a basic check. Your highest steady state loads will occur on the outside wheel during combined cornering and braking due to weight transfer. I would start by modeling the existing part to figure out the best analysis methods and see how strong they are.

vt951

Cory: Thanks, impact loads... very good point. Hard cornering and hard braking and you hit a pot hole or curb at the same time... that sounds like the worst case load to me.

vt951

Chad, is anything coming about with your idea? Care to share with us yet?

Chads996

Yes. ....um, no.

C.

Chads996

Seriously...I am still working through the feasibility. I have an idea, and I have been talking to various shops about it. Done properly, this stuff takes time. I am not rushing through this.

C.

vt951

Yes, but since we are both working towards the same goal (less costly aftermarket control arms), I think the more we share with each other, the less redundant or wasted effort there will be. I don't think there is much risk of anyone stealing your idea and running with it... this isn't exactly a high volume or high profit product. When you're ready to show it, if I see that you have a good design and are serious about putting it into production and selling it for a reasonable price, then maybe I won't waste my time pursuing the same end.

38927

that would be sick if chad does this! *wink* chad do it! we need em!

smlporsche

I'm running 575# springs on a realtively light car (remember it's not just the spring rate but the ratio of car weight to spring rate that's critical) w/ MO30 sway and yes a fairly wide front tire (245's)
According to my traqmate my max G load was 1.4 right before I broke traction and went off... so these cars are capable of quite a bit of traction..

I routinely hit 1.2+ on a hot lap at VIR

vt951

Wow! 1.4 sounds really high. Was that on a banked turn or something? I'll go ahead and assume 1.5 g max.

2BWise

Buckling is going to be the most likely failure mode, so I would concentrate on sizing them for this. Impact loading and bending are likely but by calculating mainly for buckling you'll be likely to meet the constraints of the other criteria as well.

theedge

I must be weird, I dont consider $1k for the SFR arms overpriced at all

There are also Markus Blazack arms for less I think.

http://www.blaszakprecision.com/Control_Arms.html