Track Tac

Discussion on rotating weight and its benefits

If you plan on spending money (or time) to reduce rotating weight at the rear axle, look at items that have the greatest radius from the center-line of the axle. One key factor in calculating the moment of inertia, is the radius of the object.

Paul was on to something when he mentioned the Titanium chain a while back.

If you really want to get deep into the calculations, look at inertia matching (or a ratio of) your driveline to the inertia of the crank and rotating mass.
 
"I'm just trying to decide if its worth the time, effort, money to try and lighten up all my rotating parts."

If your close to beating the next kart above you in the pecking order, yes.

Things like that are once there done there done and you can never go back. You won't be able to go back again because with racing, it becomes one of those things you need to do or it just ain't as good. Can you find more speed elsewhere, you will have to answer. I think you'll probably find the answer to be yes. Remembering back to just about every time my son came off the track for the first time at a night of racing, he'd always say the rpm's are down. My reply was always, should I put more gear on it? His reply was always after some thought, no I'll fix it with tires and air pressure. Back then we never prepped but we did always have 20 or so tires crammed into the back of the van and my son was on a first name basis with each and every one of them. So will reducing rotating weight help, yes. But is it where your immediate speed is, probably not.
 
"(especially on a flat foot track)" ... music to my ears. ... :)

But I'll tune the song a little because some reading on here may be using a little bit more hp the boxstock/clone hp. Either the track or your left foot is going to have to slow you down to the edge and beyond of maintaining momentum. Even a boxstock flatfoot track may require a little applied left foot. ... :)

maybe???
 
Paul, your response seemed well thought out and I appreciate the acknowledgement. See, no arguments- sometimes it's just that easy.
 
Just a little racing humor story thrown in here.

This past year out east I was talking to a local out east hot shoe who I've talked to about my general bs for well over 10 years now. Though my purpose to go to Susquehanna was to talk to him about rear torsion arm lengths I sort of lead the conversation into commenting on how I thought he was the best around at the "insert arc" part of it. I related to him there was no one I've ever seen at Port Royal able to rotate through the entry of turn three maintaining momentum until deciding where to enter the front stretch. His instant reply to me which totally surprised me and threw me off was, "yes but then it pushes". Sorry to say it wasn't until weeks later the reason for his push prior to exit and the fix came to me. The reason and the fix for his push after "inserting an extended arc" all the way through 3 and into 4, was mind set. He had developed the skills to maintain an enhanced momentum into and through turn entry, but he is not applying a separate same thought process of "insert arc" to his final exit turn onto the straight. In case you missed it the humor was a local out east hot shoe replying, yeah but then it pushes. ... at least I think it's humorous. ... :)

ps... I think he won at Susquehanna and by golllleeeey he was running his car exactly as I talked with him about it. ... like he listened to me. ... nawwwwww
 
Allot of the time, when you think outside the box, you just find yourself laying on the floor.
The hope is, that somebody will pick you up and build a bigger box. :)
 
M.D.racing said:
Allot of the time, when you think outside the box, you just find yourself laying on the floor.
The hope is, that somebody will pick you up and build a bigger box. :)
Click to expand...

I've been telling my family for years I'll need a bigger box. I want to be laid out with my arms folded behind my head and my legs crossed, with a fishing line and doe ball tied to my toe, like I'm resting and catching a few zzzzzzzzzzz under an old Oak tree down by the lake. ... :)
 
paulkish said:
I've been telling my family for years I'll need a bigger box. I want to be laid out with my arms folded behind my head and my legs crossed, with a fishing line and doe ball tied to my toe, like I'm resting and catching a few zzzzzzzzzzz under an old Oak tree down by the lake. ... :)
Click to expand...

No. No. Wrong kind of box Paul. You ain't done. And besides, you should go with the chicken livers. Those doe balls melt to quick.:)
I just hope they don't forget the rubber on the walls of my box.
Take Care
 
yep i'm into chicken livers. April last year I was wading out in the ocean off indian rocks beach, throwin a line out with chicken livers on it. fact is I gave up cat fishen with chicken livers to go kart racin with my son. I came real close to buying a bass boat for a kart trailer. The way I had it figured one kart up front on the flat and one in the back with racin needs in between. Might have been the first ever to go kart racing with a bass boat, but bought an old chevy van instead. ... :)
 
but another thing to keep in mind. it takes more energy to rotate and object than it does to push it. take for an example, a broom handle. push it along the floor. then pick it up and spin it like a propeller. then spin it like an axle. take note of how much force you apply to it to make it move and stop.
 
^^ I guess that depends on whether you're considering the linear distance compared to the circumferential distance or the two "linear" distances involved.... :)
 
the video shows how the weight placement of the object's rotating weight affects the inertia of the object. the further the mass is from the axis, the more difficult it is to change its velocity. the closer it is to the axis, the easier it is to change its velocity. the rotational force is caused by the lateral force from gravity while on in inclined plane. cant get as consistant of a testing platform as you can get there.
 
zablocki said:
the video shows how the weight placement of the object's rotating weight affects the inertia of the object. the further the mass is from the axis, the more difficult it is to change its velocity. the closer it is to the axis, the easier it is to change its velocity. the rotational force is caused by the lateral force from gravity while on in inclined plane. cant get as consistant of a testing platform as you can get there.
Click to expand...

Then it's back to 6 pins because with more weight closer to the center, they will be easier to roll. ... :)

______________________

The video is incorrect because his first demonstration of the blocks is incorrect.

The value of µ stays the same 'only' if the two surfaces don't change.

The increased weight of two blocks could cause the surface to change and the value of µ will change. The grain of the wood, could also cause the value of µ to change when the blocks slide down the ramp.

His trying to relate his demonstration to car tires is also flawed by the same reasoning. Moving weight towards the center with a rubber tire would almost mandate a change in µ. I'm assuming I'm remembering from watching the video last night that µ is the coefficient of friction. I guess last night is long enough ago to remember something. ... :)

The other point he missed in his video is when does reduced weight over come what is lost by the physics of weight placement, as it relates to being either harder or easier to roll something. ... sure ain't sure I understand what I just wrote. ... :(

... nawwww... Six pins are the way to to. Anyone need any Six pin front end stuff, we got a bunch to sell or use up?
 
“I'm kinda' surprised that nobody's using carbon fiber, titanium, or magnesium rims in LTO racing... ditto for sprocket hubs, brakes, brake hubs....etc. etc.”

Although I haven’t played with this in karts, I did play with it some in cars (as well as research it). Talked to a big name Legends car racer who tried lightweight wheels, and the only difference he could discern was that those wheels were more expensive and got damaged easier.

Although you are correct that the amount of mass affects how much inertia is generated (or must be overcome), that is only part of the deal. It’s also important where that mass is located. The farther the mass is located from the center of rotation, the more its affect is amplified – a lightweight mass located far away from the center can even cause more affect than a heavy mass located close to the center of rotation. Simplified to freezing a rotating system into one moment in time, Inertia = mass times radius squared. Radius is the distance from the mass you’re interested in, to the center of the rotation. By being squared it has a major impact on the inertia generated by that mass.

The benefits of lightweight wheels are usually swamped out by the weight of the tires mounted on them. The tire mass is not only farthest from the center of the axle, it can be as much or more than the mass of the wheel itself. So if you’re going to lighten your load, start at the mass farthest away. Make 'em lighter, or get them closer to the center of rotation.

Those other parts do contribute to the inertia, but again are typically swamped out by the tires. You might be able to gain a little by lightening them, but probably won’t see it on the stopwatch until you’ve optimized your tire masses first.
 
Does anyone add weight around the inside of the RF rim?

If it's important to put weight to the RF, why not load up the rim close to the center of rotation? Or how about weight spacers for the RF?

... my minds just wondering again. ... :)
 
Sure, when they're balancing the wheel assembly.
But that contributes to unsprung weight, which is its own ballyboo...

I suppose technically a kart doesn't have unsprung weight since it doesn't have springs - unless you count the elasticity of the tubing in the area of the wheel (in front, or the spring rate of the axle stub in the rear). Darn, once again the real world makes things more complicated!
 
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