200 Lap Enduro Sunday Oct 29

[Rick]

Who's racing in the 200 Lap Enduro?

[David Mickelson]

I'm racing in it. :4:

[Greg Shebert]

effort one will be there!

-G

[Rick]

Great race everyone! Congratulations to P320x0209309fds0s09a13241 (Matthew Bigos and Jr racer) for winning the lightweight division by 6.7 seconds over Stefan Sajic.

Dave and I had a good competition with Peter and Greg in the Heavyweight division. We were fortunate enough to pull out the win and come in 3rd overall. Martin and Tony came in 2nd. Peter and Greg got screwed by the 2nd red flag and came in 3rd.

I have a new respect for Peter after driving around with an extra 40lbs. I don't care what anyone says, 40lbs makes a difference . It might not make a large difference in lap time on a hot flying lap. But it does makes a difference in acceleration, braking, and turn in. I did enjoy having more grip coming out of the back S turns onto the back straight though. But that was about the only thing I enjoyed about the extra 40lbs. I miss having my "power to pass" button. :yes:

[rct25]

I have a new respect for Peter after driving around with an extra 40lbs. I don't care what anyone says, 40lbs makes a difference . It might not make a large difference in lap time on a hot flying lap. But it does makes a difference in acceleration, braking, and turn in.

Rick:

I am glad to hear that!
Even 10 lbs. will make a difference in acceleration, no doubt about it.

Roberto

[Adam Andrea]

Originally posted by rick@Oct 30 2006, 10:30 AM
I have a new respect for Peter after driving around with an extra 40lbs. I don't care what anyone says, 40lbs makes a difference . It might not make a large difference in lap time on a hot flying lap. But it does makes a difference in acceleration, braking, and turn in. I did enjoy having more grip coming out of the back S turns onto the back straight though. But that was about the only thing I enjoyed about the extra 40lbs. I miss having my "power to pass" button.* :yes:
2385

I tried those weights out on the old track1 configuration. Once I got my lap times consistent (you definitely do have to change your driving style a little bit), it came out to an increase of 0.1 seconds in the counter-clockwise direction, and 0.2 seconds clockwise.

[Rick]

Originally posted by Adam Andrea@Oct 30 2006, 11:11 AM
I tried those weights out on the old track1 configuration.* Once I got my lap times consistent (you definitely do have to change your driving style a little bit), it came out to an increase of 0.1 seconds in the counter-clockwise direction, and 0.2 seconds clockwise.
2388


Did you ever try racing with that weight? I think that weight has a larger effect on racing than it does on hot laps. This is especially true if there is a large differential in speeds between all the karts. The more you are required to decelerate and accelerate (to avoid slower karts), the more of an disadvantage it is to be heavier. And last night there was definitely a large difference in speeds!

[Rick]

Originally posted by rct25@Oct 30 2006, 11:02 AM
Rick:

I am glad to hear that!
Even 10 lbs. will make a difference in acceleration, no doubt about it.

Roberto
2387


I'm going on a diet. :glare:

[Adam Andrea]

Originally posted by rick@Oct 30 2006, 12:00 PM
Did you ever try racing with that weight? ...2389

No, I only did testing, but I agree with you that they would have an even greater effect in an actual race. The more accelerating (front, back, and sideways) that you have to do, the more your power to weight ratio is going to come into play.

The exact effect of different power to weight ratios on lap times is pretty complex, when you think about it. Both directions on track 1 have approximately the same lap times, yet adding 40 lbs has twice the effect clockwise compared to counter-clockwise. The line actually changes, as well. The slower your acceleration is, the more you want to round a corner (take it at a constant radius) instead of the later apexing "slow in, fast out" method.

[Rick]

Originally posted by Adam Andrea@Oct 31 2006, 04:14 PM
No, I only did testing, but I agree with you that they would have an even greater effect in an actual race.* The more accelerating (front, back, and sideways) that you have to do, the more your power to weight ratio is going to come into play.*

The exact effect of different power to weight ratios on lap times is pretty complex, when you think about it.* Both directions on track 1 have approximately the same lap times, yet adding 40 lbs has twice the effect clockwise compared to counter-clockwise.* The line actually changes, as well.* The slower your acceleration is, the more you want to round a corner (take it at a constant radius) instead of the later apexing "slow in, fast out" method.
2401


That's an interesting observation. Do you think that also holds true in Autocross? Should I make a more constant radius turn in my E46M3 (big fat understeering car) to get faster times?

[Adam Andrea]

Originally posted by rick@Oct 31 2006, 04:48 PM
That's an interesting observation. Do you think that also holds true in Autocross? Should I make a more constant radius turn in my E46M3 (big fat understeering car) to get faster times?
2402

I think its more dependent on power/weight than just overall weight.

There's a theory that the normal racing line breaks down for tight autocross style corners. On some corners, it seems that taking the wide entrance and late apexing is inferior to throwing the car into the corner and getting some rotation on it. My hypothesis is that when the car's width is relatively large compared to the track width, the shortcut that the rear wheels take when following the front wheels through a turn is exaggerated.

[MPIGP - Phillip Gordon]

[My hypothesis is that when the car's width is relatively large compared to the track width, the shortcut that the rear wheels take when following the front wheels through a turn is exaggerated.]

:headscratch:

[Adam Andrea]

Originally posted by CoolBreezeRacer@Nov 2 2006, 10:41 PM
[My hypothesis is that when the car's width is relatively large compared to the track width, the shortcut that the rear wheels take when following the front wheels through a turn is exaggerated.]

:headscratch:
2462

I was going to draw a diagram, but I was at work.
:P

[MPIGP - Phillip Gordon]

:lol1:

[Rick]

There's a theory that the normal racing line breaks down for tight autocross style corners. On some corners, it seems that taking the wide entrance and late apexing is inferior to throwing the car into the corner and getting some rotation on it.

So something more along the lines of a gymkhana style? That would be kinda fun to try!

[Adam Andrea]

OK, here's your diagram:
[attachmentid=106]
Dimensions are in feet, and this is based on a 6' wide car. This isn't exact, because I didn't take things like slip angle or car rotation into account (as if I could... :headscratch: ). The car is traveling clockwise around the circle. The green is the front wheel path, and the blue represents the rear wheel path.

As you can see, the tighter the turn, the larger the rear wheels' "shortcut". If your car could turn its wheels entirely sideways (90 degrees), the inside rear wheel would literally just be rotating in place! Also, the longer the car, the more the rear wheels shortcut the front wheel path. Even in something with a short wheelbase, like the go karts, this is a noticeable effect. You've probably noticed that on particularly sharp corners, if even if the front of the kart clears the wall at the apex, the back can still clip it. This usually doesn't matter, but there are some particularly nasty corners on track 2 where the barriers have no give whatsoever.

Now, you can counteract this by adding a little bit of rotation (oversteer) to the car through the corner. Ideally, you can swing the back end out just enough so the rear wheels are following the same path as the front. This way, you can take back the small amount of track that you were losing due to those sneaky rear wheels. Now you can see why this could be so important through very tight autocross turns.

[MPIGP - Phillip Gordon]

If I understand your diagram, it looks like the wheelbase has more to do with the rear wheels 'short cutting' the turn than the width of the car.

[Martin Lenick]

Adam, I wish you hadn't rounded it off to so few decimal places.

[Rick]

Originally posted by Martin Lenick@Nov 4 2006, 05:45 PM
Adam, I wish you hadn't rounded it off to so few decimal places.
2494


Yeah :angry: There's a definite lacking of precision here. :closedeyes:

[Adam Andrea]

Originally posted by CoolBreezeRacer@Nov 3 2006, 06:26 PM
If I understand your diagram, it looks like the wheelbase has more to do with the rear wheels 'short cutting' the turn than the width of the car.
2483

Wheelbase determines the amount of the shortcut (IE: Large semi trucks need to swing out before taking a turn in order to avoid the curb with the rear wheels).

The width of the vehicle (along with the turn itself) is important as well, for a more obvious reason: If you have a 5 foot wide car and a 6 foot wide car, the 5 foot wide car gets to use that extra foot on the track by taking a slightly larger radius (faster) turn.

EDIT - My new diagram will have more decimal places.

[MPIGP - Phillip Gordon]

[the 5 foot wide car gets to use that extra foot on the track by taking a slightly larger radius (faster) turn.]

I see said the blind man. B)

[Rick]

Originally posted by Adam Andrea@Nov 6 2006, 09:23 AM
EDIT - My new diagram will have more decimal places.
2522


:lol:

[Adam Andrea]

You thought I was kidding about the decimal places:
[attachmentid=109]
The dimensions of the track is the same on both sides of the diagram. The car on the left is half the width of the car on the right. Both racing lines shown are the greatest possible radius through the turn.

If you take a turn at a constant radius, the largest arc you can make is equal to the width of the track minus half the width of the vehicle.

[Rick]

Can you also create a diagram showing how pitching a car into a turn might be better. For example, the autocross situation you described.