What is COM, Weights, Polishing and tweaking

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millettbbc
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What is COM, Weights, Polishing and tweaking

Post by millettbbc »

I see many people reference COM. What is it? I am not an engineer, actually, I just like making the cars and the race is a bonus.

Though I just like to make the cars, since I do race them I want to do well.

Any thoughts of best way to polish your wheels and axles to make them fast. Where we race we must use official Awana wheels and axles and the only "do nots" is:
1. Don't alter the width of the wheel, or the general shape.
2. Axles must be from the kit or purchased through awana but can be polished and taped heads.

We are allowed to round over the bottom corner of the body and apply lube to any area we please. We are allowed to use any lube.

Are there any tried-and-true methods to making them fast?

How about weight placement? any ideas? Does it matter what you use for weight or is weight weight no matter what it is?
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Re: What is COM, Weights, Polishing and tweaking

Post by Pinewood Daddy »

Here is the DerbyTalk encyclopedia. http://derbytalk.com/lexicon.php

Spend a few hours reading the Car Construction forum and you'll find many answers to your questions.

The proper weight and location (COM) is very important along with reducing friction between the wheels, axles & body. This will give you speed. Good alignment will allow that speed to carry the car to finish quickly.

Stan's "How To Build a Winner" is a good place to start. http://members.aol.com/standcmr/lbw1.htm
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Re: What is COM, Weights, Polishing and tweaking

Post by pack529holycross »

millettbbc wrote:Any thoughts of best way to polish your wheels and axles to make them fast

Are there any tried-and-true methods to making them fast?
One thing you will want to remember is that with axles and wheels, these components represent opportunities to rob the car of energy through friction and imperfections. Prepping the wheels and axles doesn't exactly "make them fast ", in so far as what you are really doing is reducing the energy cost through these imperfections.

axles - ridges, stamping marks, and lack of smoothness hamper the freewheeling factor

wheels - wheels that wobble, are not perfectly round, or are not smooth also rob the car of the potential energy that going down the incline generates.
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Randy and Son
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Re: What is COM, Weights, Polishing and tweaking

Post by Randy and Son »

millettbbc wrote:I see many people reference COM. What is it?
COM=Center Of Mass. Its the point that the car would be able to balance if it were placed on something like the edge of a ruler. A good place to balance is about an inch in front of the rear axle. A more aggressive COM (closer to the rear axle) can yield improved times but you need to be better at other aspects of the build or you can bite yourself by getting too aggressive.

Read on as recommended and you will learn a lot more.

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Re: What is COM, Weights, Polishing and tweaking

Post by gpraceman »

millettbbc wrote:I see many people reference COM. What is it?
There is a link to the Encyclopedia of terms up near the top of the website. It is a good place to go when you run into one of these terms.
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Re: What is COM, Weights, Polishing and tweaking

Post by Teeeman »

FYI, Center of Mass and Center of Gravity are often interchanged.

There is a difference in the 2 by definition, but they are virtually the same for a Pinewood car.


The explanation I read on the difference was that for the COM and COG to not be the same... the item in question would have to be immense in size... i.e. a 20 mile tall skyscraper...

engineers routinely put CG on drawings (Center of Gravity) and use term freely and without correction from peers... unless I'm in the room, then I sting them just to be a wise-guy :)


-T
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Re: What is COM, Weights, Polishing and tweaking

Post by Teeeman »

Maybe more on topic here:

Image


-T
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Re: What is COM, Weights, Polishing and tweaking

Post by Stan Pope »

Teeeman wrote:engineers routinely put CG on drawings (Center of Gravity) and use term freely and without correction from peers... unless I'm in the room, then I sting them just to be a wise-guy :)


-T
Could those engineers fear confusion with the metric system? (CM = "centimeter" or "Center of Mass"?) Probably not ... everybody knows that "engineers are fearless!"
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Re: What is COM, Weights, Polishing and tweaking

Post by Teeeman »

Stan Pope wrote:
Teeeman wrote:engineers routinely put CG on drawings (Center of Gravity) and use term freely and without correction from peers... unless I'm in the room, then I sting them just to be a wise-guy :)


-T
Could those engineers fear confusion with the metric system? (CM = "centimeter" or "Center of Mass"?) Probably not ... everybody knows that "engineers are fearless!"

I only thought I was fearless until I got married :mrgreen:


-T
"I dunno..." - Uncle Eddie, Christmas Vacation
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