We'll definitely have to settle the weight issue soon. I know that Erik & Mike are most definitely on this. We want to improve the situation for the bigger guys while not making drivers (like my wife) drive around with a 180 pound stack of plates on bolts. A ballast containment system is being considered.

A while back I sent Erik a private email about this issue. Now that it is a more public issue I think it is worth pointing out that if we need to add mass to the car. Lighter drivers should be permitted to add the mass the same location the heavier guys get to place it, in the CENTER of the car.

If we are trying to equalize performance, then requiring the mass to be added outside the centerline of the car serves to increase the polar moment of inertia which would cause the car to want to continue to rotate while cornering and cause the car to roll more about the centroid axis. So those drivers that must add mass are put at a disadvantage.

Maybe a minor point but everyone is trying to be "fair"....then be as fair as possible. Allow me to put the plates under the seat along the center axis of the car the same location where the heavy guys get to park theirs.

I still believe everything I wrote eariler, but if this is coming then this issue should be considered in the sense of fairness as well.

It still makes no sense to me to have spent all this time and money developing a better car to just throw it away for a few larger than average people. If I was Mike I would be thinking WTF? But thinking like that and not keeping my mouth shut is what cost me my job awhile back! (Those that know me understand)

The good news is I love Ice Cream, See you at Dariy Queen Hal

PS It's killing me to not draw parallels between this mass issue and socialist issues like Obamacare but if I do my wife will come take my keyborad away and send me to my room! (sic)

Lee Spuhler wrote:A while back I sent Erik a private email about this issue. Now that it is a more public issue I think it is worth pointing out that if we need to add mass to the car. Lighter drivers should be permitted to add the mass the same location the heavier guys get to place it, in the CENTER of the car.

If we are trying to equalize performance, then requiring the mass to be added outside the centerline of the car serves to increase the polar moment of inertia which would cause the car to want to continue to rotate while cornering and cause the car to roll more about the centroid axis. So those drivers that must add mass are put at a disadvantage.

Maybe a minor point but everyone is trying to be "fair"....then be as fair as possible. Allow me to put the plates under the seat along the center axis of the car the same location where the heavy guys get to park theirs.

I still believe everything I wrote eariler, but if this is coming then this issue should be considered in the sense of fairness as well.

It still makes no sense to me to have spent all this time and money developing a better car to just throw it away for a few larger than average people. If I was Mike I would be thinking WTF? But thinking like that and not keeping my mouth shut is what cost me my job awhile back! (Those that know me understand)

The good news is I love Ice Cream, See you at Dariy Queen Hal

PS It's killing me to not draw parallels between this mass issue and socialist issues like Obamacare but if I do my wife will come take my keyborad away and send me to my room! (sic)

Lee,

It's actually worse for the heavier guys, even with the weight being equal overall, because the extra weight for a heavier guy is mostly up high in the torso, raising the cg of the car. Lighter drivers add weight down low, essentially on the floor pan, lowering the cg. Most tracks are run clockwise too, so the lighter drivers can add weight to the right side of the car, or to the left if the track happens to run cc, thereby adding grip on the majority of corners. As far as the car rotating in corners... if the weights are added at the standard mounting points, which are near the fore/aft cg of the car, they add no significant additional moment. Of course, the lightest among us may end up adding weight to the nose and tail, up to the maximum allowed of course. That would indeed increase the moment of inertia.

What Steve mentioned about coming up with a better mounting system makes sense.

Jeff

(PS...I share your Obamacare concerns...)

Jeff,

I respectully disagree. The physics of rotational inertia is a cruel mistress. Do an experiment. Take 2 one gallon containers and place them at the end of a 1' stick hold it in the air and rotate it at one rotation per 10 seconds, then using your wrist stop the rotation. Now place them on a 10' stick and rotate them at the same rate. Be prepared to let go or break your wrist.

That is polar moment of inertia. The kinentic energy contained in rotating objects at any given rate of rotation is multiplied by the radius around which they are being rotated. It is a huge effect. in this experiment the rotational inertia is 10 times greater. That is why the new engine accelerates so quickly with a lighter fly wheel and why lighter wheels have such a effect on acceleration.

By placing the mass outside the centerline of the car, the driver that has to add excessive mass is facing the effect of the car contiuning to rotate around the CG at every corner. The CG is a point, any mass placed outside of the cg tends to roatate when acted on by an outside force. Just because those masses line up with the CG of the car they are still laterally displaced from the actual point! Therefore the masses will gain rotational inertia when you place a rotational force on them by turning the car! Your comments about the mass of the nose and tail of the car also apply here. Going through the esses at COTA I believe this would have noticeable effect for the faster guys, trying to stop that rotation then getting it started back the other direction. Roll rate is nothing more than polar moment of inertia perpendicular to the center axis of the car acting through the CG. Again the farther outboard you place the weight the more the car is going to tend to rollover in the corner and continue to roll as you accelerate that mass. In the case of the esses just described, the car rolls farther to one side then that rotational inertia has to be reversed and rolled back the other direction. A quick guy like you would feel that easily and it would be a performance disadvantage.

Your comments about the CG of the body are true, but no where near as important as the effect I am describing. If you are a little guy and have to place 100# plus 2' or more outboard of the centerline of the car, the effect is far greater than raising or lowering the CG a few inches along the center line as you correctly described would happen.

PS I would look up the exact equations but my physics books are buried under the pile of beer cans I am collecting in an attempt to make a down payment on the new engine. OH LOOK here is another empty one. I'm .1 of a penny closer

Sorry, just catching up! Mike is taking everything into consideration: getting the most performance improvement out of the GEN3 upgrade, fairness to as wide of a cross section of humanity as we can, weight / ballast safety etc. Like always, his final decision will be rock solid and 100% supported by all of us. He has all of the input, mine included, and all he needs now are the weights of the 14 GEN3's that exist or will soon exist as our R&D fleet (and first new car). That representative cross section will be the most meaningful data to decide on the minimum weight drop that the GEN3 / SRF3 class will have.

I'd like to add my $.02 to this debate, but I have to keep all of my loose change in my driver suit pockets.

H.(uses xenon in his tires)B.

I’ll add $.02 to mine for Hal. My $.04 cents says if you can’t win a race being 20 to 30 pounds over the minimum in SRF, then you aren’t driving hard enough.

Richard,
That comment is worth at least $.05...I think I'll send Hal 5 pennies for him to carry in his pockets. In fact, we should all take up a collection for Hal. If everyone could send him 5 pennies each we just might get him up to minimum weight. Of course, he just might try to pull a fast one and buy a new tire or something silly like that....

Erik,
I'm certain that we all trust in Mike's judgment. The whole project is very well thought out.

Lee,
I understand what you're saying and your example sounds very convincing, but the forces around a race car are very dynamic. The dynamic center of rotation is always changing in a corner and is typically somewhere away from the static location, and depends on slip angles, oversteer/understeer, etc. I believe you're generally correct, but I also believe the effect of 20 lbs. placed a couple feet to the side from the center of rotation is not very significant. In fact, on fast, open corners it can actually be preferable to spread out the mass slightly. Look at what they do in NASCAR where the left side of the car might be many hundreds of pounds heavier than the right because the benefit of the extra weight on the inside tires far outweighs the detriment caused by the additional moment. They've even been using tungsten so more mass could be concentrated in the left rocker panel. Conversely, having to accelerate additional mass in any direction is always detrimental.

Anyway, I've spent all of my time in Spec Racer at least 20 lbs. over minimum, and more typically 30-40...even 50 over. In FC I was more like 85 lbs. over. I'd be happy if the Gen3 would accommodate a 220 lb. driver.

Jeff

Hey Guys...this is great..!
I didn't want to add this, but way back in the day most of us went faster when they raised the SR weight from 1525 to 1540. (Those #’s could be wrong, but they did raise the weight) I did anyways! On the same Goodyear tires. I needed around 50 / 60 lbs. in those days.
So this is what we need...people talking about the stuff that means something to them.
It's going to be a group decision…as Erik said; when we have the weight of the R&D kits…we will have a point of aim…lol!
Even then it’s not going to be welded down, but it’s not going to be something that gets changed every year either.
In general all of the R&D kits have shipped, not every car runs yet…but they have shipped. Erik also mentioned we will have a R&D conference call monthly, so we keep updated on the progress good and bad.
Everything looks good; I have another firmware update for the ECU and 2 cars to test with at the Turkey Trot. I could have 4 cars to test, in a couple more weeks at the same time. Yippee Life is good!

Happy Thanksgiving

Beck wrote:Anyway, I've spent all of my time in Spec Racer at least 20 lbs. over minimum, and more typically 30-40...even 50 over. In FC I was more like 85 lbs. over. I'd be happy if the Gen3 would accommodate a 220 lb. driver.

Jeff

Yup. I ran my best laps last season as "co-driver" of a friend's SRF, running 60 lbs. overweight. So weight may be a factor, but it's not that big a factor. Better to be 20+ in case you run into a wonky scale.