COM

Feb 28, 2015
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Building a BASX car. What COM do you aim for? Is 1/2 inch way too aggressive? What is considered too mild? I'd like to be able to ballpark it. Should I leave it aggressive and try to fine tune it by moving putty around? Should I build it to wiggle and try to get the wiggle out with steer/ or tame down the COM and use less steer? Any and all suggestions related to this topic are very welcome. Just curious what you guys aim for and what your objectives are when you approach this aspect of building. Thanks!
 
Half inch is aggressive but needed. 3/4 would to too mild. Move the weight around until you find your fastest time. If you can tune do it in traffic as too see how it reacts to dirty air. Hope that helps.
 
BlewBYu said:
Building a BASX car. What COM do you aim for? Is 1/2 inch way too aggressive? What is considered too mild? I'd like to be able to ballpark it. Should I leave it aggressive and try to fine tune it by moving putty around? Should I build it to wiggle and try to get the wiggle out with steer/ or tame down the COM and use less steer? Any and all suggestions related to this topic are very welcome. Just curious what you guys aim for and what your objectives are when you approach this aspect of building. Thanks!

You should never build a car to wiggle and work backwards. You should make your build as good as you possibly can from the start. You will be a lot further, faster, doing it the right way the first time.
 
The more friction you get out of your system the more aggressive the COG can be. Years ago 1/2 inch COG was a tough one to handle. Now it's the minimum to keep up with the league leaders. I suspect the faster cars of today are partially due to getting a stable aggressive COG.
 
I don't know, maybe it's just me, but I have never measured COG or COM on any of my cars. I know racers also use three scales to adjust the weight in their cars but i don't know how much weight is needed on each wheel so I'm not currently doing that.

For a first BASX car I would put your weight in evenly in front and back of the rear axle. Any left over cubes put them on the side of your DFW and then move those cubes around to find your fastest speed but yet keeping the car stable. Set your steer at 4" over 4' and send it to race and then start making one change at a time. Keep records of what changes you make. My AM BASX car Odds Zonn that finished 3rd overall in the Ice Series is weighted like above.

I feel wheel and axle prep is more important than worrying about COG or COM when you first start out league racing. I work harder on wheel and axle prep than anything else.
 
TRE said:
instead of messing with com just try and get you DWF to weigh .4 to . 5 ounces

Wouldn't that vary depending on what wheelbase he runs?
 
instead of messing with com just try and get you DWF to weigh .4 to . 5 ounces

It seems that whenever I post a question, it leads to others as well. Could someone link or explain to me HOW to weigh the DFW? In all the research I've done on this sight, I have never seen an explanation on how to do this. Certainly it cant be as easy as putting the rear wheels on one scale and the DFW on another, could it?
 
BlewBYu said:
instead of messing with com just try and get you DWF to weigh .4 to . 5 ounces

It seems that whenever I post a question, it leads to others as well. Could someone link or explain to me HOW to weigh the DFW? In all the research I've done on this sight, I have never seen an explanation on how to do this. Certainly it cant be as easy as putting the rear wheels on one scale and the DFW on another, could it?

It is exactly that easy. In fact, you don't need two scales. Just put the rears on something the same height as your scale platform and place the DFW on the scale. If you want to double check, weigh the rears by themselves and add the weight to the DFW, and it should equal the total weight of the car.