Car Weighting

[Mister B Racing]

This posting is for Momentum Racing. As you all know we each did the “Key Board Warrior” thing on each other in a different thread, but that's behind us now. He had asked me about how one of my cars is weighted and I said I would post a picture for him.

One thing that JBD has mentioned a lot and Kinser has mentioned also is to take and keep notes on everything you do on each car. So I am also posting one sheet of my notes so it may help someone else who might not be sure about keeping notes. I have used white out on a few things that I want to keep to myself but for the most part since I am a mid pack racer I don't have anything to hide. Now the set up on this sheet is an ongoing process, at this point in time I get the best track times with this set up. I am still trying to completely understand why this set up seems to work for this car, but that is all part of the learning curve. Each car is different and your set ups will probably be different than this.

I may get some heat for posting too much info, but I have my Big Boy Pants on but I hope it does help someone or someone can help me too.

 

[gWebber]

Can't imagine you would get too much heat for this.
Pretty much all this info is out in the world to find already ... Maybe not all in the same place, but out there.

Meanwhile I'm sure this info being in one place and diagramed will save some rookies and newbies some sleepless nights /images/boards/smilies/smile.gif

 

[BulldogRacing]

Good notes mr.B Great work.

 

[Momentum Racing]

Nice post Steve, you're a true gentleman and a man of your word. /images/boards/smilies/thumb.gif

Do you often start your weighting with the intent of a moderate bias on the DFW?...I tend to start with a bigger "motor" 6|6|A|6|6 set-up and work from there. If I don't end up with good results or using equal weights, I have always biased the DFW with the odd cube or putty.

 

[Vitamin K]

Nice post Steve, you're a true gentleman and a man of your word. /images/boards/smilies/thumb.gif

Do you often start your weighting with the intent of a moderate bias on the DFW?...I tend to start with a bigger "motor" 6|6|A|6|6 set-up and work from there. If I don't end up with good results or using equal weights, I have always biased the DFW with the odd cube or putty.

Out of curiosity, have you messed with Minion Racing's COM visualizer at all? Pretty slick little tool, IMO. Lets you see where the COM falls in both the X and Y axis.

http://jsfiddle.net/minionracing/uunt5/embedded/result/

 

[Mister B Racing]

Nice post Steve, you're a true gentleman and a man of your word. /images/boards/smilies/thumb.gif

Do you often start your weighting with the intent of a moderate bias on the DFW?...I tend to start with a bigger "motor" 6|6|A|6|6 set-up and work from there. If I don't end up with good results or using equal weights, I have always biased the DFW with the odd cube or putty.

On this board I think under general building DD4H has posted some basic building and setup info and that is my starting point

I have just recently started to move weight around during test sessions. For me it's like an experiment. Run the car and record the time. Move a weight, run the car, did it get faster, if it did that's my new baseline. If it was slower go back to my starting point and try something different. Sometimes the car is faster but now it wiggles, so more steer is required. So it's a bunch of stuff having to work together. Your wheel and axle prep, drill on the body, wheel gaps, weight placement, type of wheels, even type of axle.

Probably most of the top tier builders can get a lot closer to their final race set up during their initial building and do less testing because of race experience and total understanding of what a car needs to be fast.

 

[Mister B Racing]

Out of curiosity, have you messed with Minion Racing's COM visualizer at all? Pretty slick little tool, IMO. Lets you see where the COM falls in both the X and Y axis.

http://jsfiddle.net/minionracing/uunt5/embedded/result/

No I have not. I have never checked COM on any car. I don't quite understand why so many new board members are so interested in knowing that, most likely someone on a scout board said it's important and now racers that read think it's important. I just try to get my car to get the fastest times I can with my current know how and where ever the COM is located that's where it's at. As E3 PWD mentioned in another thread, the only thing that matters is what the track timer shows and wether your time is faster than the other racers in that heat or final.

But it is good to know there are tools like that out there for racers.

 

[Momentum Racing]

Out of curiosity, have you messed with Minion Racing's COM visualizer at all? Pretty slick little tool, IMO. Lets you see where the COM falls in both the X and Y axis.

http://jsfiddle.net/minionracing/uunt5/embedded/result/

I haven't seen that before VK...really good stuff ! Thanks for the link./images/boards/smilies/smile.gif

 

[Vitamin K]

No I have not. I have never checked COM on any car. I don't quite understand why so many new board members are so interested in knowing that, most likely someone on a scout board said it's important and now racers that read think it's important. I just try to get my car to get the fastest times I can with my current know how and where ever the COM is located that's where it's at. As E3 PWD mentioned in another thread, the only thing that matters is what the track timer shows and wether your time is faster than the other racers in that heat or final. But it is good to know there are tools like that out there for racers.

Well, the COM of the "Y" (long) axis is maybe less important nowadays. Pretty much just go with "2 oz behind the rears" and let the chips fall where they may as far as the other things go.

COM of the "X" axis (short) on the other hand, is a different beast. What that (theoretically) tells you is how balanced the car is from the left to right. It would seem (to me) that the better balanced a car was along the X axis, the more stable its journey down the track should be.

Of course, a lot of things about PWD defy intuition, so who knows! I definitely think it's something worth exploring further.

 

[Mister B Racing]

Well, the COM of the "Y" (long) axis is maybe less important nowadays. Pretty much just go with "2 oz behind the rears" and let the chips fall where they may as far as the other things go.

COM of the "X" axis (short) on the other hand, is a different beast. What that (theoretically) tells you is how balanced the car is from the left to right. It would seem (to me) that the better balanced a car was along the X axis, the more stable its journey down the track should be.

Of course, a lot of things about PWD defy intuition, so who knows! I definitely think it's something worth exploring further.

Yes good point about the side to side balancing. You can also check that by putting a scale under each rear wheel.

 

[Momentum Racing]

I completely respect that everyone has different views on what to focus on. I personally like having a firm grasp of the numbers involved in the car, values such as COG,COM, weight on each wheel etc... as I feel they are directly tied to the ultimate numbers you will see on the clock. But, I also don't want to get a case of "paralyzation through analyzation." The good thing about this sport is the physics applies to all of us equally, we are all on equal footing in every race. Now, one could accurately argue the physics is not the same in Utah as it is in Florida, but that would quickly arrive at one ending up paralyzed and in a mental wheelchair,with nothing to show for it./images/boards/smilies/crazy.gif

I'm currently at the point where I know I'm going to use 12 cubes in the rear, with 6 directly in front of the axle, so the first thing I do is glue them in. The 6 cubes in front of that I leave loose so I can tweak things a bit when tuning. I know a lot of guys just tape their weights in or glue them in later,but I have a different view. I feel the glue adds weight which has to be accounted for in the tune, and more importantly it stiffens the integrity of the frame structure. I want to tune the car with it as stiff and as close to the final product as I can.

All and all it's really a simple concept.The winner of any Pinewood race is always the same guy...he's the guy that started with the biggest motor, and/or who used the least amount of energy during the journey down the track.

 

[Vitamin K]

Yes good point about the side to side balancing. You can also check that by putting a scale under each rear wheel.

Just to be clear, the COM calculator works in conjunction with a scale to measure the weight of the rears. You tell it the weights and it tells you where your COMs lie.

What was a little surprising to me was that equal weight on the rears does not give you a centered X-axis COM. Definitely worthy of experimentation.

 

[Momentum Racing]

Just to be clear, the COM calculator works in conjunction with a scale to measure the weight of the rears. You tell it the weights and it tells you where your COMs lie.

What was a little surprising to me was that equal weight on the rears does not give you a centered X-axis COM. Definitely worthy of experimentation.

VK...I believe It's because they are only factoring for a literal 3 wheel car.

 

[Mister B Racing]

I completely respect that everyone has different views on what to focus on. I personally like having a firm grasp of the numbers involved in the car, values such as COG,COM, weight on each wheel etc... as I feel they are directly tied to the ultimate numbers you will see on the clock. But, I also don't want to get a case of "paralyzation through analyzation." The good thing about this sport is the physics applies to all of us equally, we are all on equal footing in every race. Now, one could accurately argue the physics is not the same in Utah as it is in Florida, but that would quickly arrive at one ending up paralyzed and in a mental wheelchair,with nothing to show for it./images/boards/smilies/crazy.gif

I'm currently at the point where I know I'm going to use 12 cubes in the rear, with 6 directly in front of the axle, so the first thing I do is glue them in. The 6 cubes in front of that I leave loose so I can tweak things a bit when tuning. I know a lot of guys just tape their weights in or glue them in later,but I have a different view. I feel the glue adds weight which has to be accounted for in the tune, and more importantly it stiffens the integrity of the frame structure. I want to tune the car with it as stiff and as close to the final product as I can.

All and all it's really a simple concept.The winner of any Pinewood race is always the same guy...he's the guy that started with the biggest motor, and/or who used the least amount of energy during the journey down the track.

I use double sided carpet tape to hold the weights in. It's light weight, good stickiness to keep the weights in but yet it's easy enough to remove the weight at a later time to reuse them.

 

[Vitamin K]

VK...I believe It's because they are only factoring for a literal 3 wheel car.

Do you think? I'm actually not sure of this, because the car is only actually rolling on 3 wheels, so the actual balance of the unit is calculated based on a triangle. Presumably, any weight of the raised wheel would be reflected by additional weight on the on wheels (in varying percentages). I could be incorrect, but I believe that for a 3-wheeled roller, it should not matter whether you have a wheel or a guide pin there.

Also, DD4H said in a different post than when he ran a car with equally weighted rears, it was majorly slow, so take that for what it is worth.

 

[Momentum Racing]

Do you think? I'm actually not sure of this, because the car is only actually rolling on 3 wheels, so the actual balance of the unit is calculated based on a triangle. Presumably, any weight of the raised wheel would be reflected by additional weight on the on wheels (in varying percentages). I could be incorrect, but I believe that for a 3-wheeled roller, it should not matter whether you have a wheel or a guide pin there.

Also, DD4H said in a different post than when he ran a car with equally weighted rears, it was majorly slow, so take that for what it is worth.

If you adjust the amount of weight on either rear wheel it effects the X axis, you can bring the red line to the cars center just by changing the weight on the rears. If the weight is the same on the rears and you have the extra weight of the front wheel on one side ,it will have to bring the X axis that direction.Imagine the car is balancing on the x axis on the edge of a ruler, not sitting on the ground.

 

[Momentum Racing]

I use double sided carpet tape to hold the weights in. It's light weight, good stickiness to keep the weights in but yet it's easy enough to remove the weight at a later time to reuse them.

I might just have to try that. Without over analyzing things, I wonder if there is any difference in weights that are secured fast, and weights that have a very small amount of pliability to them...perhaps they could cancel out harmonics, or buffer the car through the transition. Great....now I'm going to be up all night thinking !!/images/boards/smilies/biggrin.gif

 

[GravityX]

Pretty solid notes on the build Mister B. Great Job!