Track Times

[sdupont1]

Finally got the K3 installed on our new 35' best track. We ran it against last years car which was the council champion in tiger cub and 2nd overall. The new car ran:
1 - 2.608
2 - 2.602
3 - 2.610
4 - 2.607
5 - 2.600
6 - 2.604
7 - 2.599 (fastest time of new car)
8 - 2.610
9 - 2.608
10 - 2.605

According to the derby worx website, a stock BSA car on a 35' aluminum track should be 2.669 and for the razor wheels, 2.564.

This new car is legal as far as wheels go but we do allow extended wheel base. The fastest time posted was last years car with a time of 2.597. I know that track are different, but do these times look right? Basically I have matched last years car.

[ohiofitter]

Looks like your right up there with your times.

[ichiban]

Speeds from slowest to fastest...

DerbyWorxes Best Track 35' Aluminum Track w/ stock BSA car
358.5" / 12" = 29.875'
time = 2.6699s
speed = 29.875' / 2.6699s = 11.190'/s
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DerbyWorxes Micro Wizard 32' Wood Track w/ stock BSA car
331.5" / 12" = 27.625'
time = 2.4460 seconds
speed = 27.625' / 2.4460s = 11.294'/s
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Our Micro Wizard 40' Aluminum Track w/ our pack winning car
27.625' + 8' = 35.625' (not sure distance from pin to sensor so added 8' for the 8' difference in Micro Wizard track lengths)
time = 3.109s (our fastest time of the day)
speed = 35.625' / 3.109s = 11.459'/s
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Your Best Track 35' Track w/ your car
29.875' / 2.599s = 11.495'/s
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Having some hypothetical fun with an accuracy level on scale with a ball park...

Our Micro Wizard 40' Aluminum Track w/ how your car would have done
time = 35.625' / 11.495'/s = 3.099s
x / 11.459'/s = 3.099s
x = 3.099s * 11.459'/s
x = 35.512' (our distance traveled as your car hits the sensor)
35.625' - 35.512' = 0.113' * 12" = 1.356" (distance our car nose is behind as yours hits the sensor)

[sdupont1]

so hypotheticly, I guess I'm running pretty good.

[ichiban]

At the very least pretty good

Did you have one wheel raised?
Was your car alignment setup for straight or rail riding?
Were the wheel hubs coned?

[sdupont1]

-Extended wheelbase
-4 deg camber
-RR , but RRing to the raised wheel. I feel I could run a little faster if it would track to the running wheel.
-COM approx .5" in front of rear wheel. 8 tungsten plates + some lead weight to fine tune.
-alignment is damn near straight, approx .5" at 4'.

car is paper thin, approx 1/8" thick the entire length of car and approx 1/2" wide except for nose which has to be 3/4".

Lets just say that this car will run with and sometimes beat (2.599 compared to 2.597) my outlaw car with 1.0 gram wheels. This car will also only get beat by 1" on the down slope due to the lighter wheels on the oputlaw car but the aggressive COM will catch and make that up + more on the straight away. I really feel that if we were running on a longer track, the new one would beat the outlaw car by an inch or two.

[doct1010]

I'm confused. You say it was RR on lifted wheel and then go on to say it "ran darn near straight"? Help me here. Good times none the less, you may be on to something!

[sdupont1]

When I tested it on my glass coffee table which is about 4' long, the car drifts to the right about .5". The left front is the raised wheel so the car pulls to the right causing the raised wheel to ride the rail. When I drop the starting gate, the car hits the rail within 1' and rides it all the way down to the stopping section. Is the table not level, don't know but I'll check. Is the track level, need to check that also. All I Know is that this car flys. I would rather the raised wheel be totally out of the loop and have the right front wheel ride the rail. By having the raised wheel RR, I'm probably getting some braking action to get the raised wheel going rather than RR with an already moving wheel. All in all, very satisified with the outcome.

One other thing, on the derby worx web, they claim that their track is 50" high and they are running times of 2.6699 stock and 2.579 with razor wheels. The funny thing is that I just noticed that and measured mine. Mine is only 47" to the back of the track from the floor. So if I would have an additional 3" of height or PE, times could be faster.

[ichiban]

By some of your car specs we shouldn't be within a cars length of yours at the finish. Possible my math is not even in the ballpark.

However, isn't cambering for when you dont want to rail-ride? And could that COM location be causing your front wheels to lift resulting in problems?

[sdupont1]

not sure, but I may have found something that others don't want you to know. Remember, there is always someone beating the other by a nose at the finish, well I have a track and can tinker and have found something that works. As far as COM goes, last years council champ and this one is running .5".

[3 Cub Dad]

not sure, but I may have found something that others don't want you to know. Remember, there is always someone beating the other by a nose at the finish, well I have a track and can tinker and have found something that works. As far as COM goes, last years council champ and this one is running .5".

Talk about cryptic! Are you talking about the camber? Just curious with that COM, did you do a front / rear weight comparison? How much weight did you have over the front wheels?

My youngest's car won the pack today, (big brother was second), but looking at his alignment you would think it would be slow. The front dominant RR wheel was actually canted down, as well as slightly toed in. However, he was almost as fast as my illegal wheeled open class car!

[sdupont1]

I don't have two scales to do a comparison and not much weight in front of front wneels. Camber on all wheels except the raised wheel.

[3 Cub Dad]

Just as an FYI, you don't need two scales to do a front vs back weight. Just set up a block or stack of wood next to the scale so that it's basically level with the scale, (I use a stack of wood shims). set the car so the front wheels are on the scale and the back wheels on the wood, that's the weight of the front, flip the car around and that's the weight of the back, add the two together and they'll equal the total weight of the car!

Are the axles canted up and do you have any idea how much?

[sdupont1]

The block worked well.

rear weight 130 grams
front weight 10 grams

Car isn't painted yet so I left some room for paint. I can always go back and add more weight to get to around 141.7 grams or 5.0 oz

[3 Cub Dad]

The block worked well.

rear weight 130 grams
front weight 10 grams

Car isn't painted yet so I left some room for paint. I can always go back and add more weight to get to around 141.7 grams or 5.0 oz

0.36 ounces on the front wheel?!? Lets see, 10 grams, each wheel at 3.6 grams would be 7.2 g, close to 8g with the axles, did you leave ANY wood??

seriously, I'd love to see a picture. This kind of goes against what I've always used and heard as a working principle, and that is that you needed to have close to an ounce on the front, or 20% or 28 grams, in order to have it steer and stay stable. I've got my adult/open class car set up as an extended wheel base RR, but the entire amount of weight I added to the front is underneath with tungsten putty. I think I'm going to have to move it to the rear cavity and try some test runs!