I notice some people use wheel weights (i.e. Puma weights and similar designs) and some do not. Fast cars in both cases. What are the positives and negatives of wheel weights. For the purposes of this thread ignore the aerodynamic aspects of wheel weights. I am more interested in how the weights impact COM and if moving the weight off centerline helps, etc. so why do you use or not use wheel weights.
Wheel weights
- Thread starter GDH Racing
- Start date
I use wheel weights on my Basx and SS cars. I use brass or lead, the tungsten ones required too much steer and without a track it's tuff to guess a steer with that aggressive of COM. I have had nothing but good results since using the wheel weights, it does require a little more steer but the weight is more centered. My suggestion is try them, see what you think.
I use Fender washers for weights on my Basx and SS cars. They seem to work well but I still had to put a lot of cubes in the back of the car. I have one BASX car that has the full tungsten weights and I agree, it takes a lot more steer and I could only add 5 cubes. Not sure if that is enough cubes to move around to fine tune the speed of the car. I am going to try the brass ones on a future build. Has anyone tried the 1/2 tungsten Cubby Wheel weights yet? What do you think of them? Or are the lead wheel weights from DD4H the way to go for wheel weights?
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Vitamin K
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Do you have to add more steer for wheel weights on account of the CoM getting pushed further back, or is there something destabilizing about having the weights that far out to the sides of the car?
GDH Racing said:
There are quite a few discussions about these in various threads on the forum. Here are a couple that I've read about them.
This thread starts about DD4H wheel weights, but has a lot of discussion of the weights themselves throughout the many pages: http://www.pinewoodderbyonline.com/post/more-secrets-released-7012609
This other thread talks about using the weights and it's affect on COM, thereby affecting steering: http://www.pinewoodderbyonline.com/post/need-advice-on-com-of-0-5-or-less-using-puma-weights-7282126
I'm sure there are probably a lot of other threads about them as well.
Vitamin K said:
It's a catch 22 really, but bottom line there's more speed in wheels weights. I personally didn't have to add more steer when I had wheel weights in. All about the fine tuning. But then again my car was slow as neck last month. Luckily I know it wasn't because of weighting or steer.
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Vitamin K
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Obsessedderbydad said:
What's the reason for this? Does increasing the horizontal moment of inertia (physics people, correct me here), make the car resist lateral motion more readily?
Vitamin K said:
I do not know the technical scientific reason. All I know is it does and that works for me.
Obsessedderbydad said:
This is not an entirely true statement. Just because you use wheel weights does not mean your car will be more stable than a car without wheel weights.
My BASX car Nilon Hoze has the full tungsten wheel weights and it is one of the most unstable cars I have.
I have 6" of steer and the car wiggles badly. I added 5 cubes and puddy to make weight but I am probably to aggressive with where I placed those 5 cubes. So... I need to move some weight around to fine tune the car to see if I can get it stable.
Mister B Racing said:
Hmmm 6" of steer? Still have wiggle? Sounds like something is really wrong. My SS had Pumas plus about 12 cubes and I could run 3" of steer no problem. Probably could go less.
Obsessedderbydad said:
Don't forget that you have fenders on your SS that are deflecting air away and around your wheels and wheel weights and also probably putting some down force on your body that will help stabilize your car.
On my BASX car I will tighten up the wheel gaps, and will move some weight around, maybe even try some different styles of weight and see what happens.
But like Hogans Racing mentioned above, racers are finding that with the tungsten wheel weights, the cars need more steer to be stable.
G
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I usually don't measure or worry about COM. I put the weight in the car, adjust it a bit to gain some speed and get the car as stable as I can, wherever COM is, that's where it is.GDH Racing said:
As far as Nilon Hoze goes, the axle drilling is good and the body is not warped. So all new wheel and axle prep is in order. I am going to pull the cubes out of it and try some tungsten plates. Some of my wiggles are probably from wheel gaps that are too loose, so I'll tighten those up. I can probably take some steer out of it. I just need to spend some time testing. Each car is different and each car setup is different and it just takes some time to figure it out.
I think the radius of gyration that everybody is talking about is the energy it takes to induce rotation based on the location of mass. With a figure skater in a spin, he/she will stick their leg out to slow themselves and pull it in to speed up. The energy stayed constant but the speed of rotation changed. When a PWD hits the track or a small bump the same amount of energy is transferred to the car regardless of weight position. But, with a wide distribution of weight such as with wheel weights the car will rotate slower. My question for you physics geniuses is "will it make a difference?" If the com is still centered from side to side, the effect on the car should be of the same magnitude, just at a different speed. It'll be slower to get out of position but slower to get back in position as well. Thoughts?
G
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