weight, anyone doing the new placement ?

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sporty
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weight, anyone doing the new placement ?

Post by sporty » Wed Sep 17, 2014 1:27 pm

Anyone doing the new weight placement ?

The weight attached to side of body at axle whole area ? Fits more or less inside wheel hubs .

Anyone got pictures to share ?

Sporty



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Re: weight, anyone doing the new placement ?

Post by FatSebastian » Wed Sep 17, 2014 2:19 pm

sporty wrote:The weight attached to side of body at the axle hole area? Fits more or less inside wheel hubs .
I am imagining the weight protruding from the body into the doughnut-shaped channel between the tread and the hub on the back of the wheel. Is this correct?

What is the supposed advantage of this placement?



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Re: weight, anyone doing the new placement ?

Post by sporty » Wed Sep 17, 2014 2:40 pm

A few top racers are doing this and winning.

I was hoping to hear more about it.



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Re: weight, anyone doing the new placement ?

Post by whodathunkit » Wed Sep 17, 2014 6:15 pm

sporty wrote:Anyone got pictures to share ?
Sporty,
I hope this photo helps you out with getting this topic rolling!
Image
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Re: weight, anyone doing the new placement ?

Post by sporty » Wed Sep 17, 2014 6:23 pm

Thanks, awesome.

I had heard about this.

Feel free to say what u think. Thank you so much for posting and sharing the picture.

Sporty



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Re: weight, anyone doing the new placement ?

Post by FatSebastian » Wed Sep 17, 2014 7:27 pm

Interesting. Once, a long time ago, we had contemplated employing something almost exactly like that, presuming these mild benefits:
  • 1. If the wheel void was filled, it might improve the aerodynamics around the wheel.
    2. It adds weight close to the rear axle where it is generally needed.
    3. It requires less ballast to be added into the body, allowing more flexibility.
But we never pursued it fearing disqualification, as every rule set we've ever competed under included something like "wheel bearings, washers, and bushings are prohibited."



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Re: weight, anyone doing the new placement ?

Post by gpraceman » Wed Sep 17, 2014 7:51 pm

That is a very novel idea. When I first heard about it, I thought the weights were being attached to the wheels, not the body. That certainly makes more sense.


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Re: weight, anyone doing the new placement ?

Post by Stan Pope » Wed Sep 17, 2014 10:17 pm

FatSebastian wrote:Interesting. Once, a long time ago, we had contemplated employing something almost exactly like that, presuming these mild benefits:
  • 1. If the wheel void was filled, it might improve the aerodynamics around the wheel.
    2. It adds weight close to the rear axle where it is generally needed.
    3. It requires less ballast to be added into the body, allowing more flexibility.
But we never pursued it fearing disqualification, as every rule set we've ever competed under included something like "wheel bearings, washers, and bushings are prohibited."
Good list!

If the "washers" wording were truly an issue, then you could replace them with custom cast shapes from lead or sintered tungsten and accomplish a more refined fit.


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Re: weight, anyone doing the new placement ?

Post by sporty » Wed Sep 17, 2014 11:17 pm

My first thoughts are.
This reduces micro vibrations. And provides wider weight distribution.
Congrats to those who came up with, tried it and got it to work and share it.
Great to see new thinking and new ways. I only ever tried to glue cubes before or after on the side of the wood.

This is great in my view of it.

I'm sure its faster, so I've heard and believe some are winning with it.
Wonder if it provides a big increase ? Or just another small increase ? But I'm sure its a increase none the less.
I
Tungsten puma weights , hope I can mention that, see they are for sale.
Our other people selling them or something like it ?

Anyone got some, can post pictures of there weight ?
Does washers or the tungsten . I assume the center while is big enough not to cause any canting issues ?



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Re: weight, anyone doing the new placement ?

Post by Stan Pope » Thu Sep 18, 2014 3:30 am

Nice see you again, Sporty!

Pix: google "Tungsten puma weights"

Plus is reducing void in wheels to reduce aero drag.
Plus is allowing reduction in the car body cross section.
Minus is spreading the weight, but that should not be a significant factor on a smooth track. (On a rough track, the wider the weight distribution the more energy is used up in raising one side or the other.)

Nets out as a "plus", I think.

The "puma" has a large notch intended, perhaps, to avoid touching the rail. I think that is unnecessary, since you align to keep rears off rail. However, some rules may take exception to anything that "could" touch the rail. Pic a few posts ago showed washers set into the wheel so that even when the wheel were at the nail head, the inner edge of the wheel would touch the rail before the weight. That should satisfy the concern of the weight toughing the rail.

If you wanted to lower the CM in the car, the puma weight notch could be on top! But I think that CM should be even with the axle, and with thin body, that is almost automatic!

Time to put it on a test track and take some measurements! :)


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Re: weight, anyone doing the new placement ?

Post by FatSebastian » Thu Sep 18, 2014 8:34 am

Stan Pope wrote:If the "washers" wording were truly an issue, then you could replace them with custom cast shapes from lead or sintered tungsten and accomplish a more refined fit.
Not sure if it would truly be an issue, but we never want to tempt complainers either. (The thought of "casting" something that was clearly not a washer also crossed our minds, but we didn't think that was worth the effort for our type of racing.)

Another drawback is that it completely masks the inside wheel area which prevents inspection for lightening or official marks. Makes ya' look like your hiding somethin'! ;)
sporty wrote:Tungsten puma weights...
The Puma weights are snazzy! A big improvement over using steel or even lead.

With the notch for guide-rail clearance, the center of mass of the car becomes slightly raised. Some people swear by keeping the CoM slung as low as possible. Also, wheel doughnuts increase the mass moment of inertia about the "roll" and "yaw" axes, so like Stan I wonder how it would respond to a rough wooden track (not an issue for league racing I'm sure). Those issues wouldn't detract us from trying them though.



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Re: weight, anyone doing the new placement ?

Post by Stan Pope » Thu Sep 18, 2014 11:09 am

FatSebastian wrote:Makes ya' look like your hiding somethin'!
Great point!

Inspector could require that you remove the wheels for inspection. If you align by a "bent axle alignment" procedure, then you might be in a bind unless you know how to get 'em back in alignment quickly.

If you run straight axles in unaltered holes, you might get by okay. As an alternative to pre-race wheel pull, you might negotiate a post-race wheel pull inspection and "public DQ" if you know you are "clean."

On the issue of roll moment ... The reaction to small bumps (bumps in which the axle can move without requiring the wheel to move also) CM below axle plane may be better (see note below). For larger bumps (bumps in which body roll predominantly causes wheel roll also) CM at axle plane is better. For "in between" bumps, I'm not sure.

Note: Lower CM may be better ... Trade-off's: lowering the CM below the axle plane (1 +) slightly increases the "head" (height differences between CM at starting line and CM at finish line), (2 -) slightly lengthens the path followed by the car as it runs the track, and (3 +) slightly reduces the track's apparent radius of curvature. Each of these has a small impact on the car's elapsed times. You probably don't notice these even at competitive pack racing.


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Re: weight, anyone doing the new placement ?

Post by FatSebastian » Thu Sep 18, 2014 11:19 am

Stan Pope wrote:Note: Lower CM may be better ... You probably don't notice these even at competitive pack racing.
Discussed ad nauseam over here :sick: . I concur that the vertical CoM effects are very small, although, perhaps not small relative to the benefits from using doughnut ballasts.



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Re: weight, anyone doing the new placement ?

Post by sporty » Thu Sep 18, 2014 12:04 pm

What if 1/2 of the washers were used ? Or tungsten 1/2 rounds were used ? insteal of a full circle ?

Still get the wider weight distribution. That also would keep the weight low.

Perhaps the weight already, using full washers. Its lower cog, since it is lower than the more common weight location ? Perhaps the weight height their is not a issue ? Its going lower, now.

The lowness of the weight and the height of the wight are centering, balancing out the mass at center, right where you have your axle whole to begin with .. That's what I think is going on and should be real close to where you want the weight height at.

I prefer to have less of a physics type of conversation and more of pictures of the build and what the comments and thoughts are from the builders, who are doing it.

I see a few different ways and types of material to use here and im more interested in learning about it.

So Maybe Stan, can you build a couple and run it down your track ? get some pictures, maybe try some different ways .? maybe you can figure out how much faster it is ? do some testing and times .


I would think the grooved axle head , k- groove. would make it easy to turn and unless the axle is glued in. I don't see a issue with adjusting alignment.

That's if you are using bent axles in the rear, So many drill cant these days !

Im sure the axles wholes are canted, pretty common to run 2.5 to 3 degrees of cant in the rear these days.

Sporty



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Re: weight, anyone doing the new placement ?

Post by FatSebastian » Thu Sep 18, 2014 12:38 pm

sporty wrote:What if 1/2 of the washers were used? [...] instead of a full circle ?
If some of the benefit is aerodynamic, then C-shapes (half-doughnuts) should have less of that benefit. I wonder if it is possible to test the aerodynamic benefits by mounting lightweight "washers" (shields) made of paper or cardstock inside the wheels, then dismounting and replacing with an equivalent amount of (small) weight, and comparing the results. This could be done with the front wheels and well as the rear. Such a test doesn't require investing in actual ballast, and maybe somebody's already done such.



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