Our District and Council races are this Saturday. The following description of the track (from the organizer) is below, and answered a question about weight placement.
"5. The acceleration (down-hill) span on the SD500 track is full straight section followed by a 30 degree curved slope-section to the flat run-out portion of the track. The transition section of the track uses a 182 inch radius section to obtain the smooth transition over the 72" drop from the top of track. The design does not follow the "Challeger" plan, it only uses the same plating. Many folks belive that the rear-weighted cars run faster. Theory would seem to support it but in reality many other factors overshadow the weight placement where there is such a long run-out distance (40 foot) on the flat track."
After reading this board we decided that our car should be changed a little from the 30' wooden track we used for the Pack. We decided to jump right into Ninjarabbi1997's idea (Railriding & 4 wheelers):
"Next year, we plan on doing differently: a CG of 1"-1 1/8" in front of the rear, keep the weight low again, 1 oz on front wheel, use Pinewood Extreme lube followed by Hob E Lube, cone the body, and are thinking of building two cars each for the boys--a rail rider and dead aligned--and race the fastest. I like the idea of going for dead alignment with the rear wheels and offsetting both front wheels, but want to heed Stan's warnings."
Our car is now pretty much like this except it has a "quick start bar" and .84 oz on the front end.
Here's the strange part. I read a rather odd thing in a thread titled "Who has the longest track" (March 19th). The rumor was that on a very long track, a lighter car has an advantage at the end of the flat.
Does this make sense to you guys?
I thought the weight was necessary to shoot the car forward at the end of the curve. Would the lighter weight reduce friction at the end of the 54' flat? The only way to know for sure is to test it, but this race is not the time to experiment.
Anyone know for sure about moving the weight forward, or making it lighter for a long aluminum track?
60' aluminum track and lighter weight car? (long)
-
2kids10horses
- Master Pine Head
- Posts: 424
- Joined: Thu Feb 17, 2005 11:57 am
- Location: North Geogia
Re: 60' aluminum track and lighter weight car? (long)
I have no experience with this type of track, so my comments are just theory.
But, I would focus on making sure I had very well balanced wheels, and highly polished axles. Use the best lube available. If you have to use dry, the graphite technique you quoted appears to be popular. If you can use oil, Krytox is popular.
Rear weighting is still the best way to get the most out of the total potential energy available to you.
On a long track, those who do the best to remove friction and acheive the best alignment will prosper.
Good luck. Tell us how it went, and YOU'LL be the expert on designing for long tracks!
2K10H
But, I would focus on making sure I had very well balanced wheels, and highly polished axles. Use the best lube available. If you have to use dry, the graphite technique you quoted appears to be popular. If you can use oil, Krytox is popular.
Rear weighting is still the best way to get the most out of the total potential energy available to you.
On a long track, those who do the best to remove friction and acheive the best alignment will prosper.
Good luck. Tell us how it went, and YOU'LL be the expert on designing for long tracks!
2K10H
Re: 60' aluminum track and lighter weight car? (long)
It is true that weight is not everything. 
I use a 8 section beta-craft aluminum track. It has the Challenger design AND it has a 2 inch per section continuous drop to help out some of the cars.
The track record is held by a 3.5 oz car, the wieght limit of the Pack's Adult division. Granted, most of my 3.5oz cars do very well against the heavy 5oz cars. Pack limit of 3.5oz for adults is to make the racing between parent/child more favorable to the kids!
I just had a District race where a cub brought a friend who wanted to race. The race officials said it would be fine and asked if I had any cars. (little did they know. . .
) I went out to the truck and grabbed my box of style demos from my workshops and let the visiting boy pick one. These cars haven't raced for a few years and are played with every Sunday by cubs at the workshops. 
Well to make a long story fun, he picked a 5 year old 3.5oz car. It passed inspection and the officials looked at me when it only weighed in at 3.495 oz. I said it was ok. They asked if it should be lubed, I said no. Lucky for me there were only 3 throphies because it came in 4th - - at a district race after being a toy and no new lube!
So, I can attest that weight is not everything that people think it is ON LONG ALUMINUM TRACKS WITH FASTEST RUNS IN THE 4.350 second time - 58' pin to sensor. Hob-e-Lube must have a long shelf life. . . . alignment was straight -- axles holes drilled with the pro-body tool, axles prep with "special stuff" (available soon at a url near you?). Body design is very sleek, but not just a slab by any means. It still had 3 of the original racing wheels, sanded and coned. Fourth looked to be straight from the box - replaced for style demo at workshops. -- the three were matched mold, the 4th spun nicely without wobble.
I use a 8 section beta-craft aluminum track. It has the Challenger design AND it has a 2 inch per section continuous drop to help out some of the cars.
The track record is held by a 3.5 oz car, the wieght limit of the Pack's Adult division. Granted, most of my 3.5oz cars do very well against the heavy 5oz cars. Pack limit of 3.5oz for adults is to make the racing between parent/child more favorable to the kids!
I just had a District race where a cub brought a friend who wanted to race. The race officials said it would be fine and asked if I had any cars. (little did they know. . .
) I went out to the truck and grabbed my box of style demos from my workshops and let the visiting boy pick one. These cars haven't raced for a few years and are played with every Sunday by cubs at the workshops. Well to make a long story fun, he picked a 5 year old 3.5oz car. It passed inspection and the officials looked at me when it only weighed in at 3.495 oz. I said it was ok. They asked if it should be lubed, I said no. Lucky for me there were only 3 throphies because it came in 4th - - at a district race after being a toy and no new lube!So, I can attest that weight is not everything that people think it is ON LONG ALUMINUM TRACKS WITH FASTEST RUNS IN THE 4.350 second time - 58' pin to sensor. Hob-e-Lube must have a long shelf life. . . . alignment was straight -- axles holes drilled with the pro-body tool, axles prep with "special stuff" (available soon at a url near you?). Body design is very sleek, but not just a slab by any means. It still had 3 of the original racing wheels, sanded and coned. Fourth looked to be straight from the box - replaced for style demo at workshops. -- the three were matched mold, the 4th spun nicely without wobble.
Mr. Slick says: Honey, I am doing this for the kids, not myself.
-
Mike Doyle
- Master Pine Head
- Posts: 275
- Joined: Fri Mar 05, 2004 2:26 pm
- Location: Kansas
Re: 60' aluminum track and lighter weight car? (long)
It sounds like you face a very similar pair of tracks to what we race on. Our Pack track is 28', wood/formica faced while the District track is around 50' aluminum.
This year we finally hit on the right combination and won the Districts with a rear weighted car. I think I've read just about every thread here and the general consensus is to go with more of a center weighted design for longer tracks. My opinion is the alignment is more critical for longer tracks and the center weight offers more of a compromise.
If you want to "go for it", then run rear weight and focus on alignment. The math proves it, maximum weight and position = a greater PE to KE conversion.
This year we finally hit on the right combination and won the Districts with a rear weighted car. I think I've read just about every thread here and the general consensus is to go with more of a center weighted design for longer tracks. My opinion is the alignment is more critical for longer tracks and the center weight offers more of a compromise.
If you want to "go for it", then run rear weight and focus on alignment. The math proves it, maximum weight and position = a greater PE to KE conversion.
-
2kids10horses
- Master Pine Head
- Posts: 424
- Joined: Thu Feb 17, 2005 11:57 am
- Location: North Geogia
Re: 60' aluminum track and lighter weight car? (long)
Slick,
It would be an interesting exercise to take one of your 3.5 oz cars and time it on the long track. Add .5 oz, and time it again. Up to 5 oz and see if adding weight helps or hurts your times.
Also, observe whether the 3.5 car is the first down the hill to the transition? Or did it pass others on the flat? Where is the advantage? I suspect it's on the flat: Less weight on the axles, therefore less speed loss due to friction. But is that the case?
However, a well lubed and aligned 5 oz car would have considerable more momentum to power past a lighter car.
The center weighting is an advantage to those tracks that start out relatively flat, then transition to a steep area, then transition to a flat. Rear weighted cars start out slowly on those S shaped tracks. (Or so I've heard. I've not raced on one.)
Of course, you could test this, too! While you're adding weight to the car, run it with center weighting, time it, then move the weight back and time it.
(Make friends with the guy who manages the track! <grin>)
2K10H
It would be an interesting exercise to take one of your 3.5 oz cars and time it on the long track. Add .5 oz, and time it again. Up to 5 oz and see if adding weight helps or hurts your times.
Also, observe whether the 3.5 car is the first down the hill to the transition? Or did it pass others on the flat? Where is the advantage? I suspect it's on the flat: Less weight on the axles, therefore less speed loss due to friction. But is that the case?
However, a well lubed and aligned 5 oz car would have considerable more momentum to power past a lighter car.
The center weighting is an advantage to those tracks that start out relatively flat, then transition to a steep area, then transition to a flat. Rear weighted cars start out slowly on those S shaped tracks. (Or so I've heard. I've not raced on one.)
Of course, you could test this, too! While you're adding weight to the car, run it with center weighting, time it, then move the weight back and time it.
(Make friends with the guy who manages the track! <grin>)
2K10H
Re: 60' aluminum track and lighter weight car? (long)
Well, I have to set the track up tomorrow for a race and again on Friday night for another group, maybe I could make a few runs. . . 
(I'll feel guilty just having fun!)
If I do this, I really won't have time to send a car to WIRL this month!
Is .5 oz the best increment? how about a smaller increment? Should I try all 6 lanes or just one? Too much science, not enough appreciation of the art side of this sport!
Do I need to post the results, and if so, what topic/thread?
(I'll feel guilty just having fun!)If I do this, I really won't have time to send a car to WIRL this month!
Is .5 oz the best increment? how about a smaller increment? Should I try all 6 lanes or just one? Too much science, not enough appreciation of the art side of this sport!
Do I need to post the results, and if so, what topic/thread?
Mr. Slick says: Honey, I am doing this for the kids, not myself.
Re: 60' aluminum track and lighter weight car? (long)
Wow, that would be great if you could do this experiment. As an artist, I appreciate the art and science of pinewood.
I don't know what kind of weight you have, possibly lead or tungsten. The tunsten cylinderss weigh .5 oz, the cubes are about a fourth of that, .125.
If you raced two cars, keeping each in the same lane each race, but added two cubes or a cylinder per race, it would tell us what, if any, difference it makes. The time is most important, but seeing the difference at the finish line between the two cars is kind of "real world."
The posting of results doesn't need to be much more than posting the times of four or five races, starting with 3.5 oz and added a cylinder, or some lead. Yep, no doubt about it...this is a scientific group, but I personally will take even the most informal test if you are willing If you just add a post to this thread on Friday evening we will be most grateful.
You are the ONLY one set up to do this, and with a race this Saturday you have no idea how important it is to us. We follow the rules, but we also look for every possible thing that helps. Be happy, race cars!
Thanks,
Bob and Robert
I sent you an email.
I don't know what kind of weight you have, possibly lead or tungsten. The tunsten cylinderss weigh .5 oz, the cubes are about a fourth of that, .125.
If you raced two cars, keeping each in the same lane each race, but added two cubes or a cylinder per race, it would tell us what, if any, difference it makes. The time is most important, but seeing the difference at the finish line between the two cars is kind of "real world."
The posting of results doesn't need to be much more than posting the times of four or five races, starting with 3.5 oz and added a cylinder, or some lead. Yep, no doubt about it...this is a scientific group, but I personally will take even the most informal test if you are willing If you just add a post to this thread on Friday evening we will be most grateful.
You are the ONLY one set up to do this, and with a race this Saturday you have no idea how important it is to us. We follow the rules, but we also look for every possible thing that helps. Be happy, race cars!
Thanks,
Bob and Robert
I sent you an email.
-
2kids10horses
- Master Pine Head
- Posts: 424
- Joined: Thu Feb 17, 2005 11:57 am
- Location: North Geogia
Re: 60' aluminum track and lighter weight car? (long)
Slick,
Any research you do is well appreciated by all readers of this forum!
I suggested the 1/2 oz increment because it's pretty easy to get 1/2 oz tungsten cubes.
To eliminate lane bias, I'd do all the timing using just one lane. If you use two lanes, one lane may be faster than another, and you'd get skewed results. ("Skew" is a technical term when discussing statistics, and the statistians may tell me that I'm using the term in the wrong context. Let's just say that using one lane would introduce fewer variables for evaluation!)
Please post the results here! You could start a new thread, if you like. Don't worry. We'll find ya!
Shoot, you might be able to use this data to improve those WIRL cars!
2K10H
Any research you do is well appreciated by all readers of this forum!
I suggested the 1/2 oz increment because it's pretty easy to get 1/2 oz tungsten cubes.
To eliminate lane bias, I'd do all the timing using just one lane. If you use two lanes, one lane may be faster than another, and you'd get skewed results. ("Skew" is a technical term when discussing statistics, and the statistians may tell me that I'm using the term in the wrong context. Let's just say that using one lane would introduce fewer variables for evaluation!)
Please post the results here! You could start a new thread, if you like. Don't worry. We'll find ya!
Shoot, you might be able to use this data to improve those WIRL cars!
2K10H
Re: 60' aluminum track and lighter weight car? (long)
Slick, this would be very interesting. I'd vote for .5 oz increments, same lane, 3 or 4 trials for each weight, that should tell you. If your increments are too fine, you'll have trouble distinguishing the difference. No doubt that someone who is a talented builder could build a fast car that was 3.5 oz. But I can't see them defeating another talented builder weighing in at 5 ounces. I am not from Missouri (Show-me state!) , but I'm only a 1/2 mile away, so they still have to SHOW ME!
-
Stan Pope
- Pine Head Legend
- Posts: 6856
- Joined: Sat Jul 05, 2003 7:01 pm
- Location: Morton, Illinois
- Contact:
Re: 60' aluminum track and lighter weight car? (long)
If you do this test, please document these measurements for each condition:
total weight
front wheel weight
rear wheel weight
heat times
Thanks!
total weight
front wheel weight
rear wheel weight
heat times
Thanks!
Stan
"If it's not for the boys, it's for the birds!"
"If it's not for the boys, it's for the birds!"
Doh! Should've kept the data!
Doh! Should have kept the data!
We were able to run several hand-timed practise races at the tuning/check-in night with the weights in different locations. I'd been told by some veterans that the 5oz cars don't necessarily do well on our track because of it's very long runout, so I was eager to try different combinations of weight and CG. (Alex was just eager to pick where the weights would go and write down the times to see what was fastest..)
I wasn't able to measure it, but after seeing it all set up, I think our track is in the neighborhood of 50' with a 45* ramp and starting pins around 5' off the ground.
The car ran on 3 wheels. Camber was terrible on all 3 wheels, rear toe was mostly straight, and front toe was set to rail-ride with an inch of turn in 3' or so. (he's still learning how to see the alignment of individual wheels..)
Results taken by averaging 4 trials on the hand-punched watch in each config showed a 4.5oz config to be slowest, 5.0oz with aft-most weight 2nd, and 5.0oz with forward-most weight fastest. Total difference was around 2 tenths out of 4 seconds.
It seems like we tried a center CG, but the difference between it and the others might have been in the noise... If I can find the paper we recorded data on I'll post something more exact.
Forward-most CG was more than 1.5" ahead of the rear axle, rear-most was more like 1" or 3/4".
We spent 2 solid hours polishing the axels down to 2500 grit mirror-smooth as well as breaking them in with derby-worx lube, so I'm not surprised that the heavier weight was faster; but I was surprised to see the forward weight go faster. I think the additional stability of the forward CG helped the car deal with its alignment over the long track.
Oh, and a rail-rider note: The first 3 race-day runs were 4.01, 4.00, and 4.01 on the official optical timer. *VERY* consistent. After the crash, the alignment was significantly different and the times were very erattic- differing by nearly 4 tenths over 3 runs in the same lane!
The winner turned in a 3.98 and a 3.97, but was also less consistent. His average was slower than our pre-crash average (not much, though..). Seems like the dead-straight alignment has a higher chance factor...
We were able to run several hand-timed practise races at the tuning/check-in night with the weights in different locations. I'd been told by some veterans that the 5oz cars don't necessarily do well on our track because of it's very long runout, so I was eager to try different combinations of weight and CG. (Alex was just eager to pick where the weights would go and write down the times to see what was fastest..)
I wasn't able to measure it, but after seeing it all set up, I think our track is in the neighborhood of 50' with a 45* ramp and starting pins around 5' off the ground.
The car ran on 3 wheels. Camber was terrible on all 3 wheels, rear toe was mostly straight, and front toe was set to rail-ride with an inch of turn in 3' or so. (he's still learning how to see the alignment of individual wheels..)
Results taken by averaging 4 trials on the hand-punched watch in each config showed a 4.5oz config to be slowest, 5.0oz with aft-most weight 2nd, and 5.0oz with forward-most weight fastest. Total difference was around 2 tenths out of 4 seconds.
It seems like we tried a center CG, but the difference between it and the others might have been in the noise... If I can find the paper we recorded data on I'll post something more exact.
Forward-most CG was more than 1.5" ahead of the rear axle, rear-most was more like 1" or 3/4".
We spent 2 solid hours polishing the axels down to 2500 grit mirror-smooth as well as breaking them in with derby-worx lube, so I'm not surprised that the heavier weight was faster; but I was surprised to see the forward weight go faster. I think the additional stability of the forward CG helped the car deal with its alignment over the long track.
Oh, and a rail-rider note: The first 3 race-day runs were 4.01, 4.00, and 4.01 on the official optical timer. *VERY* consistent. After the crash, the alignment was significantly different and the times were very erattic- differing by nearly 4 tenths over 3 runs in the same lane!
The winner turned in a 3.98 and a 3.97, but was also less consistent. His average was slower than our pre-crash average (not much, though..). Seems like the dead-straight alignment has a higher chance factor...
Re: 60' aluminum track and lighter weight car? (long)
Ok, I had about 5 minutes after getting the track set up before the boys came in. I will do a quick data dump and try to get some sleep -- tomorrow night is check-in for a couplke hundred Girl Scout cars for Friday night's race!
Cars all stayed in the same lane. These cars ranged from never raced to 6 years old.
Car A, starting weight of 3.270 oz. 3 years old
Car B, starting weight of 3.495 oz. 5 yrs old, well aligned
Car C, starting weight of 4.980 oz. 6 years old, son's car.
Car D, starting weight of 2.625 oz. never raced, workshop scroll saw demo that got painted and had "raw" BSA wheels/axles.
The Races, Started with 3 heat straight from the box, C1, C2, C3.
Added a bit of Hob-E-Lube since all of the Tube-O-Lube was in the workshop truck that the wife had. . . I just had the racing trailer.
After lube, ran 2 races for fun, C4 & C5.
+1 Front = Added .36 oz. above the front axle of A, B, D.
+2 Front = Added another .36 (total of +.73 oz. with tape) above the front axle of A, B, D.
+3 Front = Added more for a total of +1.10 oz above the front axle of A, B, D.
+3 MID = Moved the 3 weights to MIDDLE of car.
+3 Rear = Moved the 3 weights above rear axle.
Race, Time A, B, C, D, Weight A, B, C, D
C1, 5.149, 4.650, 5.463, 5.068, 3.270, 3.500, 4.980, 2.625
C2, 4.849, 4.684, 4.936, 5.046, 3.270, 3.500, 4.980, 2.625
C3, 4.874, 4.680, 4.745, 5.100, 3.270, 3.500, 4.980, 2.625
C4, 4.887, 4.581, 4.673, 4.860, 3.270, 3.500, 4.980, 2.625
C5, 4.576, 4.601, 4.923, 4.872, 3.270, 3.500, 4.980, 2.625
+1 Front, 4.902, 4.553, 5.452, 4.758, 3.630, 3.860, 4.980, 2.985
+2 Front, 4.595, 4.496, 4.663, 4.713, 4.000, 4.230, 4.980, 3.355
+3 Front, 5.021, 4.561, 5.129, 4.744, 4.370, 4.600, 4.980, 3.725
+3 MID, 4.505, 4.516, 4.808, 4.686, 4.370, 4.600, 4.980, 3.725
+3 Rear, 4.873, 4.510, 4.817, 4.782, 4.370, 4.600, 4.980, 3.725
anyone want to do an experimental design for the varibles. . . not tonight!
Cars all stayed in the same lane. These cars ranged from never raced to 6 years old.
Car A, starting weight of 3.270 oz. 3 years old
Car B, starting weight of 3.495 oz. 5 yrs old, well aligned
Car C, starting weight of 4.980 oz. 6 years old, son's car.
Car D, starting weight of 2.625 oz. never raced, workshop scroll saw demo that got painted and had "raw" BSA wheels/axles.
The Races, Started with 3 heat straight from the box, C1, C2, C3.
Added a bit of Hob-E-Lube since all of the Tube-O-Lube was in the workshop truck that the wife had. . . I just had the racing trailer.
After lube, ran 2 races for fun, C4 & C5.
+1 Front = Added .36 oz. above the front axle of A, B, D.
+2 Front = Added another .36 (total of +.73 oz. with tape) above the front axle of A, B, D.
+3 Front = Added more for a total of +1.10 oz above the front axle of A, B, D.
+3 MID = Moved the 3 weights to MIDDLE of car.
+3 Rear = Moved the 3 weights above rear axle.
Race, Time A, B, C, D, Weight A, B, C, D
C1, 5.149, 4.650, 5.463, 5.068, 3.270, 3.500, 4.980, 2.625
C2, 4.849, 4.684, 4.936, 5.046, 3.270, 3.500, 4.980, 2.625
C3, 4.874, 4.680, 4.745, 5.100, 3.270, 3.500, 4.980, 2.625
C4, 4.887, 4.581, 4.673, 4.860, 3.270, 3.500, 4.980, 2.625
C5, 4.576, 4.601, 4.923, 4.872, 3.270, 3.500, 4.980, 2.625
+1 Front, 4.902, 4.553, 5.452, 4.758, 3.630, 3.860, 4.980, 2.985
+2 Front, 4.595, 4.496, 4.663, 4.713, 4.000, 4.230, 4.980, 3.355
+3 Front, 5.021, 4.561, 5.129, 4.744, 4.370, 4.600, 4.980, 3.725
+3 MID, 4.505, 4.516, 4.808, 4.686, 4.370, 4.600, 4.980, 3.725
+3 Rear, 4.873, 4.510, 4.817, 4.782, 4.370, 4.600, 4.980, 3.725
anyone want to do an experimental design for the varibles. . . not tonight!
Mr. Slick says: Honey, I am doing this for the kids, not myself.
-
Stan Pope
- Pine Head Legend
- Posts: 6856
- Joined: Sat Jul 05, 2003 7:01 pm
- Location: Morton, Illinois
- Contact:
Re: 60' aluminum track and lighter weight car? (long)
Car C is "all over the board", even though the only change (if I understand correctly) was to lube once after run C3! I don't think that this car tells us anything, except perhaps that either the car or the track has some serious problems. The following analysis assumes the the problems are with the car, not the track!
The Front, MID, Rear sequence of times for Car A and D suggest that the front-end friction is better than rear-end friction. If the car is a 3-wheeler, then the rear is probably not well aligned and the wheels are "pinching". When CM moves toward poorly aligned wheels, times deteriorate. I think we can not learn anything from these cars.
In each case, the increments of weight resulted in moving the CM forward in the car (reducing the effective potential energy). This results in strange behavior of the numbers, since the increase is intended to be distributed to overcoming aerodynamic and wheel inertia losses. It may have done so, but moving the CM forward also causes ET to deteriorate.
That leaves Car B.
Presuming that Car B's original CM is somewhere between the rear axle and the middle of the car, and that moving the added weight around that point produced only a small change, it seems reasonable to compare Car B's +3 MID and +3 Rear times to its consistent post-lube times, C4 and C5, noting an ET reduction of about 0.078 sec. That would be large if it were statistically significant.
There is a lot of unexplained variance in the data, especially in Car B's numbers from C4, C5, +1 Front, +2 Front and +3 Front. C4 and C5 should be the same. The next three should show some consistent trend, a more-or-less straight line. But, they "bend"!
The "shifting of CM" nasties the data badly. I believe that horizontal shifts of CM usually cause more change in CM the comparable vertical shifts of CM. So, if you have a chance to repeat the test, adding the weight AT (or just above) THE CM would eliminate a lot of distractions in the data!
The Front, MID, Rear sequence of times for Car A and D suggest that the front-end friction is better than rear-end friction. If the car is a 3-wheeler, then the rear is probably not well aligned and the wheels are "pinching". When CM moves toward poorly aligned wheels, times deteriorate. I think we can not learn anything from these cars.
In each case, the increments of weight resulted in moving the CM forward in the car (reducing the effective potential energy). This results in strange behavior of the numbers, since the increase is intended to be distributed to overcoming aerodynamic and wheel inertia losses. It may have done so, but moving the CM forward also causes ET to deteriorate.
That leaves Car B.
Presuming that Car B's original CM is somewhere between the rear axle and the middle of the car, and that moving the added weight around that point produced only a small change, it seems reasonable to compare Car B's +3 MID and +3 Rear times to its consistent post-lube times, C4 and C5, noting an ET reduction of about 0.078 sec. That would be large if it were statistically significant.
There is a lot of unexplained variance in the data, especially in Car B's numbers from C4, C5, +1 Front, +2 Front and +3 Front. C4 and C5 should be the same. The next three should show some consistent trend, a more-or-less straight line. But, they "bend"!
The "shifting of CM" nasties the data badly. I believe that horizontal shifts of CM usually cause more change in CM the comparable vertical shifts of CM. So, if you have a chance to repeat the test, adding the weight AT (or just above) THE CM would eliminate a lot of distractions in the data!
Stan
"If it's not for the boys, it's for the birds!"
"If it's not for the boys, it's for the birds!"
Re: 60' aluminum track and lighter weight car? (long)
Car C was one of my youngest daughter's cars. I grabbed it because it was easy to put on weights - nice and flat for the most part. One axle is held on with duct tape - probably the reason for times all over the board.
Car D should have a set of good axles and wheels - not just the raw, out of the box ones. My guess is that the back ones are worse then the front ones.
Car A had raw axles on the back also. It has a set of prep'd axles and wheels on the front.
Car B just wants to get to the end.
I might get a chance to do some races on Friday night before the practice round for the Girl Scouts. If so, I will get better axles on the cars and get more runs in each of the conditions so that we can try and determine the level of track "noise".
A large set of numbers, from a recent district race, can be had at:
http://www.skypoint.com/~kalsowwp/cbd2006_packres.html
This should be readily copied and pasted into your favorite spreadsheet software. This data might help "characterize" the track.
Total time spent racing: 646.8 seconds
Total variance from Average Time:
Lane A: 4.17 seconds, on average.030 seconds per car
Lane B: 4.22 seconds, on average .030 seconds per car
Lane C: 4.19 seconds, on average.030 seconds per car
Lane D: 4.92 seconds, on average .035 seconds per car
Lane E: 4.13 seconds, on average .029 seconds per car
Lane F: 4.88 seconds, on average .035 seconds per car
So it looks like the variance from lane to lane is fairly equal. We are talking 2/3rds of one percent as one measure of lane variability.
Lane A: 22 Fastest, 17 slowest
Lane B: 18 Fastest, 25 slowest
Lane C: 20 Fastest, 23 slowest
Lane D: 34 Fastest, 20 slowest
Lane E: 33 Fastest, 16 slowest
Lane F: 19 Fastest, 41 slowest
Based on this I would say that Lane F, has some bias compared to the other lanes since a lot of cars had their slowest runs in Lane F and a small number had their fastest runs in lane F(but more that lane B . . )
To see how musch faster than average a lane is when a car had it's fastest time in a specific lane. . . I take the variance from the average time for cases where the car had it's fastest run in each lane, the totals are:
Lane A: 0.68 seconds, .031 per car on average
Land B: 1.37 seconds, .076 per car on average
Lane C: 1.14 seconds, .057 per car on average
Lane D: 2.08 seconds, .061 per car on average
Lane E: 1.45 seconds, .044 per car on average
Lane F: 0.58 seconds, .030 per car on average
Curious that Lane B, the lane with the fewest Fastest runs, had the largest gap between the a car's average time and fastest times. . .
And the same for the sum of the variance from average when the car had it's slowest run in a lane:
Lane A: 1.12 seconds, .066 per car on average
Land B: 1.26 seconds, .050 per car on average
Lane C: 1.31 seconds, .057 per car on average
Lane D: 0.78 seconds, .039 per car on average
Lane E: 0.83 seconds, .052 per car on average
Lane F: 2.55 seconds, .062 per car on average
And my poor lane F seems to have a close to normal gap between a car's average time and it's slowest time. . . .
So with 140 cars and 6 lanes there should be enough raw data for today.
Car D should have a set of good axles and wheels - not just the raw, out of the box ones. My guess is that the back ones are worse then the front ones.
Car A had raw axles on the back also. It has a set of prep'd axles and wheels on the front.
Car B just wants to get to the end.
I might get a chance to do some races on Friday night before the practice round for the Girl Scouts. If so, I will get better axles on the cars and get more runs in each of the conditions so that we can try and determine the level of track "noise".
A large set of numbers, from a recent district race, can be had at:
http://www.skypoint.com/~kalsowwp/cbd2006_packres.html
This should be readily copied and pasted into your favorite spreadsheet software. This data might help "characterize" the track.
Total time spent racing: 646.8 seconds
Total variance from Average Time:
Lane A: 4.17 seconds, on average.030 seconds per car
Lane B: 4.22 seconds, on average .030 seconds per car
Lane C: 4.19 seconds, on average.030 seconds per car
Lane D: 4.92 seconds, on average .035 seconds per car
Lane E: 4.13 seconds, on average .029 seconds per car
Lane F: 4.88 seconds, on average .035 seconds per car
So it looks like the variance from lane to lane is fairly equal. We are talking 2/3rds of one percent as one measure of lane variability.
Lane A: 22 Fastest, 17 slowest
Lane B: 18 Fastest, 25 slowest
Lane C: 20 Fastest, 23 slowest
Lane D: 34 Fastest, 20 slowest
Lane E: 33 Fastest, 16 slowest
Lane F: 19 Fastest, 41 slowest
Based on this I would say that Lane F, has some bias compared to the other lanes since a lot of cars had their slowest runs in Lane F and a small number had their fastest runs in lane F(but more that lane B . . )
To see how musch faster than average a lane is when a car had it's fastest time in a specific lane. . . I take the variance from the average time for cases where the car had it's fastest run in each lane, the totals are:
Lane A: 0.68 seconds, .031 per car on average
Land B: 1.37 seconds, .076 per car on average
Lane C: 1.14 seconds, .057 per car on average
Lane D: 2.08 seconds, .061 per car on average
Lane E: 1.45 seconds, .044 per car on average
Lane F: 0.58 seconds, .030 per car on average
Curious that Lane B, the lane with the fewest Fastest runs, had the largest gap between the a car's average time and fastest times. . .
And the same for the sum of the variance from average when the car had it's slowest run in a lane:
Lane A: 1.12 seconds, .066 per car on average
Land B: 1.26 seconds, .050 per car on average
Lane C: 1.31 seconds, .057 per car on average
Lane D: 0.78 seconds, .039 per car on average
Lane E: 0.83 seconds, .052 per car on average
Lane F: 2.55 seconds, .062 per car on average
And my poor lane F seems to have a close to normal gap between a car's average time and it's slowest time. . . .
So with 140 cars and 6 lanes there should be enough raw data for today.
Mr. Slick says: Honey, I am doing this for the kids, not myself.
-
Stan Pope
- Pine Head Legend
- Posts: 6856
- Joined: Sat Jul 05, 2003 7:01 pm
- Location: Morton, Illinois
- Contact:
Re: 60' aluminum track and lighter weight car? (long)
If so, try to add the weight increments at (or just above) the car's CM.Mr. Slick wrote:I might get a chance to do some races on Friday night before the practice round for the Girl Scouts. If so, I will get better axles on the cars and get more runs in each of the conditions so that we can try and determine the level of track "noise".
The moving CM raises more issues about fore and aft Cf (coefficient of friction) differences. And, Cf differences arise from BOTH wheel-axle quality AND alignment-induced pinching. Holding CM nearly constant should nearly eliminate the effect of the Cf differences!
Stan
"If it's not for the boys, it's for the birds!"
"If it's not for the boys, it's for the birds!"
