So I haven't been able to find many methods or scales on how to measure CoG. How do y'all measure the CoG of your care. Pine car has a kit to measure it, but I have to believe you guys have a good way to do it. Thanks for the help.
Measuring CoG
- Thread starter Obsessedderbydad
- Start date
Call it CoG or COM. As mentioned a lot of racers here won't check COM. But! I feel that if you do not have a track to test and tune on, you have to know as much as you can about the car and it's characteristics in order to tune it the best you can. I don't have a track to tune my cars on and all I can do is tune them on a 4 foot tuning board, "mirror". All it (tuning board) can tell me is how much steer I have in my car over 4 foot. It also lets me listen to the wheels as they roll over the smooth glass surface, quite is good. Too much noise and I'm cleaning and rechecking my wheel bores for contamination. Wipe tread surface first and re-roll before taking apart. Also, make sure the mirror surface is clean and free of debris.
Anyhow, I can say this, if I know the COM on my car I have an idea the amount of steer my car will need to get decent times. It's an inexact science but it gets me close. I track all specs on my cars before and after a race. It is all recorded, from here I make single minute adjustments to try and capture additional speed. I sometimes don't follow my own rules and screw up my cars, more is not always better. My method of tuning, as I like to call it, is the Trial by Fire method as described above. Tune by what I know and what I've seen by reviewing the races and tune from there each month.
With all this said, and thanks to Minions Racing, this tool for calculating COM was born. It'll get you close enough and it's consistent. So, if you use every time, your results will be relative to the previous results of the same car. After awhile you'll see patterns as to how COM affects steer given different wheel bases and weight placement. Use it or not, it's up to you.
Anyhow, I can say this, if I know the COM on my car I have an idea the amount of steer my car will need to get decent times. It's an inexact science but it gets me close. I track all specs on my cars before and after a race. It is all recorded, from here I make single minute adjustments to try and capture additional speed. I sometimes don't follow my own rules and screw up my cars, more is not always better. My method of tuning, as I like to call it, is the Trial by Fire method as described above. Tune by what I know and what I've seen by reviewing the races and tune from there each month.
With all this said, and thanks to Minions Racing, this tool for calculating COM was born. It'll get you close enough and it's consistent. So, if you use every time, your results will be relative to the previous results of the same car. After awhile you'll see patterns as to how COM affects steer given different wheel bases and weight placement. Use it or not, it's up to you.
To find the COM, simply balance the car on your fingertip. It'll be pointing directly at the COM.
For me, I build the car, then out of curiosity check the COM. "Hmm. So that's where it is this time. Not bad." /images/boards/smilies/biggrin.gif
For me, I build the car, then out of curiosity check the COM. "Hmm. So that's where it is this time. Not bad." /images/boards/smilies/biggrin.gif
- Nov 24, 2011
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Use a block of wood (the Silver Bullet, on it's side works best at this). The wood has to be about 3/4" thick and fit between your rear wheels. Place the block of wood or Silver Bullet on the table and place your car, with wheels, weight and axles installed on it. Try to get the car at the point where it starts to tip forward. The point at the edge of the wood or Silver Bullet is your COM. The edge of the wood or Silver Bullet measured to the center of your rear axle is the COM measurement.
For you guys that don't check your COM, do you check corner weights instead (like on three scales)? Or do you just check the total weight of the car and go with it?
- Nov 24, 2011
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I don't check my COM anymore and I don't check the weight of each wheel. I just check my total weight and go with it.
I think the three scales can be educational. I was amazed at the difference in the weight difference at each wheel. There is no way to position your weights to equalize the weight on each wheel let alone the rears. It's amazing how much slower the DFW side of the car is compared to the other side considering the weight difference and the two wheels on one side versus one wheel on the opposite side.
+1, People ask me some pretty specific questions on this. I tell them I have no idea. I don't think they believe me, not trying to keep anything from anyone I just don't measure it.
Kinser Racing said:
- Nov 24, 2011
- 3,903
- 30
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5KidsRacing said:
How else are you going to throw off these guys getting so fast? I guess we could tell them to wax their wheel bores. /images/boards/smilies/biggrin.gif
Kinser Racing said:
Now that would just be going too far! Nobody would believe me if I said to do that!
jator359 said:
Is this the post you were thinking of?
http://www.pinewoodderbyonline.com/post/show_single_post?pid=1279663364&postcount=1
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