|
Post by derbydad63 on Oct 8, 2008 20:40:10 GMT -6
Hey, does anyone have any input on cm relative to track configuration?... we are used to racing on an aluminium track with a gradual slope (probable 8' radius, 40' length) and have a challange race for charity and they are using a best track with the steeper drop and 4' radius curve to the straightway (also 40'). We are used to designing CM around 1 1/8"... Keeping in mind the sweet spot of 1" - 1 1/4" in front of rear axle I am wondering if my cm can be little closer to 1" on the best track config or if we are better off moving other direction towards the 1 1/4" given the shorter radius and seemingly sharper curve. We use extended wheelbase and only enough pine to hold wheels and weight. No weight behind rear axle and tungsten to keep mass centered.
New to the board and appreciate the help!
|
|
jmca44
Pine Head
DYNAMITE RACING
Posts: 28
|
Post by jmca44 on Oct 8, 2008 21:40:24 GMT -6
i race on a 35' best track with the steep ramp i put 4 tungsten cylinders in front and 4 behind the axle sometimes only 3 in front and some puddy. everyone i know has great results with this setup. you really need to get your car aligned good when you do this or it will get a little out of control. hope this helps thats what i would do.
|
|
beakerboysracing
Head in the Pine
You can pick your friends, you can pick your nose, but you can't flick your friends across the room.
Posts: 167
|
Post by beakerboysracing on Oct 9, 2008 6:01:57 GMT -6
Hey, does anyone have any input on cm relative to track configuration?... we are used to racing on an aluminium track with a gradual slope (probable 8' radius, 40' length) and have a challange race for charity and they are using a best track with the steeper drop and 4' radius curve to the straightway (also 40'). We are used to designing CM around 1 1/8"... Keeping in mind the sweet spot of 1" - 1 1/4" in front of rear axle I am wondering if my cm can be little closer to 1" on the best track config or if we are better off moving other direction towards the 1 1/4" given the shorter radius and seemingly sharper curve. We use extended wheelbase and only enough pine to hold wheels and weight. No weight behind rear axle and tungsten to keep mass centered. New to the board and appreciate the help! DerbyDad63, You can get really aggressive with weight placement on an aluminium track. Most guys in the leagues are running between 3/4 and 3/8 COM in front of the rear axle. I wouldn't go there unless you are going to incorporate some advance techniques such as Rail Riding because you might have some stability issues. Those stability issues can be corrected with Rail Riding and the car can be made to go super fast.As far as set up between the two diff kinds of aluminum tracks, its about the same. I have found you need more steer for a Best Track than you do for a Pandadosi style track you are refering to. Also, you want to try and keep your weight as low, centered, and compact in the chassis. Take a look at the following thread and weight triangulation. It may help. pwdracing.proboards91.com/index.cgi?board=weight&action=display&thread=754&page=1Good Luck Scott Beakerboys
|
|
docb
Addicted to Speed
Atlas Derby Cars
Posts: 100
|
Post by docb on Oct 9, 2008 12:15:10 GMT -6
Derbydad.... If you have relatively good alignment you should definitely move your COM back to about 3/4" in front of rear axles. If you have confidence in your alignment and rail riding techniques then you can be even more aggressive. If you go anything over 1" for your COM then you are leaving valuable time on the table My thoughts. Good Luck
|
|
|
Post by derbydad63 on Oct 9, 2008 21:05:29 GMT -6
Outstanding... exactly what I was l looking for. Thank you everyone. By rail riding I am assuming you mean setting up the alignment for a gradual push along the rail. We use the wax paper technique to dial it in and run on 3 wheels. We have very centered weight mass... tungsten weight in the 3 1/3 oz disk sitting right in front of the rear wheel with another 2 - .5 oz added (ground down to get to 5 oz max) directly in front of that. Body itself is styled and cut so that weight by itself is less than .8 oz.
I built an alignment board with lanes drawn in that is 6' in length. If I was going to create a good rail hugger how quickly (aggressive) should the car move to the side in that distance?
|
|
beakerboysracing
Head in the Pine
You can pick your friends, you can pick your nose, but you can't flick your friends across the room.
Posts: 167
|
Post by beakerboysracing on Oct 10, 2008 6:09:53 GMT -6
Outstanding... exactly what I was l looking for. Thank you everyone. By rail riding I am assuming you mean setting up the alignment for a gradual push along the rail. We use the wax paper technique to dial it in and run on 3 wheels. We have very centered weight mass... tungsten weight in the 3 1/3 oz disk sitting right in front of the rear wheel with another 2 - .5 oz added (ground down to get to 5 oz max) directly in front of that. Body itself is styled and cut so that weight by itself is less than .8 oz. I built an alignment board with lanes drawn in that is 6' in length. If I was going to create a good rail hugger how quickly (aggressive) should the car move to the side in that distance? DerbyDad63, The term Rail Riding is a technique used that is intended to make the car run as straight a line as possible with the rear wheels never touching the center rail. The idea is that no matter how straight the car runs, due to factors such as track set up, track configuration, lane bias, staging and etc, the car will never run down the track without touching the center rail. In fact, even with a car that will roll 10 ft and not deviate 1/8 of an inch in that span will still contact the center rail several times before the finish. This side to side contact scrubs speed off the car and if you think about it, the car actually may travel 42 ft on a 40 ft track to get to the finish. That could be the difference between winning and losing. To set up a Rail Rider, you simply narrow the front end of the car so that the front wheel track is narrower than the rear wheel track. Most guys will narrow the front around a 1/16 of an inch on each side, although it is only necessary to narrow the Front Dominate wheel side of the car. This will allow the rear wheels to stay off of the center rail. You then steer the car into the center rail with the FDW by bending the axle or shims. As far as how much steer, that depends on the car. The lighter the front end, the more steer. Most experts say 1 1/2 to 2 inches in 6 ft. I have had cars that needed as much as 4 inches in 6 ft and some that only need 2 inches in 10 ft. It really depends on the car and you will have to play with it to find the "sweet spot". As for you weight placement, if you have room behind the rear axle, I would put those two .5 oz weights behind the axle. One ounce of weight will make a huge diff in COM and potential energy the car will have coming down the slope of the track. Scott Beakerboys
|
|
|
Post by derbydad63 on Oct 10, 2008 19:20:02 GMT -6
Thanks Scott... you've been a huge help. As soon as I figure out how you get a picture in your ID or message body Ill post a picture of the final car. We race next Friday for a United Way charity event. Ive been helping our scouts build winning cars by running clinics and our pack derby for 4 years now and am constantly amazed at how much more there is to learn... I've always tried to give the boys a solid dose of the science as well as the creative design. Appreciate the knowledge transfer, I will pass it along to the scouts in our clinic this year.
Thanks to docb as well.
|
|
|
Post by teamfreeroller on Apr 26, 2009 18:12:15 GMT -6
we run 3/4 or less ..my son car ran 295.640 6 run avg with stock bsa wheels .only thing we done sanded the mold bump only. that was on 42`besttrack. hope that helps. teamfreeroller.
|
|