Anyone have kart 4 corner scales?

[Rick]

Anyone have 4 corner scales that I can borrow or use?

[Jeff Salak]

Making a home made scale and stand. Should work, Going to test it this weekend at my friends house who owns a longacre scale for $1400. My scale was about $250 to make. See how it works side by side with me in kart and kart by itself on stand. I will compare and make sure its accurate! Before I go and say I have a scale! If it works Rick, you are welcome to it and anyone else who wants to use it. I charge a case of Budweiser!!:thumbsup:

[Jeff Salak]

Benched that Idea. Im buying some Tanner wireless scales. Your welcome to use for a small fee!!!! LOL!!:stickpoke::rofl:

[Jeff Salak]

Rick, bought a set of Longacre scales with a stand. Bought it on ebay. Very good deal.

Will let my dear friends use at a very low cost!

Has all the features thats needed.

I will have them set-up at first race.

Jeff

[JET Karting - Andy Finke]

We have scales too. What ever works easier for you Rick.

FYI, to all that are working on this:

I typically run in the 55-60% range of rear weight, and make sure the left and right fronts and rears are within 5 lbs of each other.

I used to believe in scales as a VERY important tool. Then I visited the Birel factory. They don't even own a set of scales at the factory. If you put the seat in the right spot, and have a straight chassis, it is fine. After checking the method extensively, I found the factory was right... Who'd have thunk it??

Now I mount the seat per factory specs, and check the frame on a flat plate. Works every time. Static weight distribution is far less important than dynamic weight distrubution.


Andy

[Rick]

Static weight distribution is far less important than dynamic weight distribution.

Andy

Doesn't the static weight influence the dynamic weight?

[Jeff Stamper]

Well Andy, since not everybody is the same size or shape, that cannot possibly work more than half the time. We mounted seats years ago without even considering most of this stuff. But what you said about where the seat goes only applies to the kart with no driver. Some folks are top heavy, others bottom and so on. I am sorry to put it that rudely, but that makes no sense. Please keep in mind that they dont race at the factory, they just want you to buy them. They really dont care if they scale out or not I am sure. One more thing. If they have no scales at the factory, how do they know how the kart scales out with the seat in the PERFECT position ?

[JET Karting - Andy Finke]

Jeff-

You're missing a couple important pieces of info. I'll give you some things to mull over today, and then answer both your and Ricks' questions. Today I have to deliver another kart and don't have time to explain it as well as it deserves.


1:
We all agree weight can either be high in the seat or low. Either with lead on the outside, or the drivers build inside the seat.

How can you tell the difference between weight high and weight low in the seat on a set of scales?

Will weight high versus low in the seat have an effect on the track?


2:
I met some of the best racing minds I have ever had the chance to spend time with during my week at the factory. There is a lot to learn there, and they aren't just trying to sell chassis. Much like Ferrari, selling chassis allows them to win races, not the other way around. So my questions are:

How well has the Birel factory done in World Championship karting in Europe for the past 40 years?


Not everyone believes that what happens in Europe is important here. I get that.

Who won the WKA Manufacturer's Cup in '08, and how close was second place?


If anyone else is following this, make sure you answer the 1: questions as well. Understanding what is happening to the kart on track makes you much smarter, and smarter drivers are faster drivers. Making a mistake is only wrong if you don't learn from it.


Andy

[JET Karting - Andy Finke]

Hey guys-

I have some time this morning, so I'll dive into this a little further. This has turned into a pretty long article, but if you bear with me, I think it’s worth it.

First of all, this started as a question of the importance of scaling your kart. Let’s look at some hard numbers:

Most everyone will tell you that rear weight should be somewhere between 55 and 60% of total. The difference between 55% and 60% is very little. In the Sportsman class at 250# we are argueing over a total of 12.5 lbs difference in the rear weight. That's only 6.25# per tire! In a class at 360# we are looking at only 18# difference in rear weight or 9# per tire. Still not a lot.

I found the factory seat position achieved this goal without trouble.


Moving on.

How can you tell the difference between weight high and weight low in the seat on a set of scales?

If the weight is moving ONLY up and down, with no left/right or front/rear change, you will obviously see no change in the scale readings. Most of the time you will be pretty close to this moving the weight up or down on the back of the seat.

Will weight high versus low in the seat have an effect on the track?

This is where the difference between Static and Dynamic weight distribution becomes VERY important.

Static is stationary, not moving. Like you measure with scales.

Dynamic is in transit, or moving. Like what happens in the corner with g force affecting your carried weight in each corner.

Since the chassis needs to flex to move the load and handle correctly in the corner, we have to tune the stiffness of the chassis to be 'balanced' with the force available to twist it. This is why Becker has a 28mm tubing building his Sportsman chassis, and Rick has 32mm tubing building his TAG chassis. Rick has more weight up high, stickier tires to build more g's, higher speeds, and more hp. All of these create more 'twist' force to the chassis.

Rick needs a stiffer chassis to control these forces, and Becker needs a softer chassis to be sure his flex's with the lower ‘twist’ force.



This is also the ‘tuning’ we do to the stiffness of the chassis. While I’m not going to come up with an exhaustive list, some adjustments that change chassis stiffness are:Torsion bars – front, middle, and rear
Hub length
Seat stiffness
Seat struts – number and location
Rear width
Front width
Axle wall thickness
etc...Changing either the ‘twisting’ force, or the way the chassis deals with that force, affects your Dynamic Weight Distribution. I have found that the Dynamic issue is far more important that the Static issue. While static distribution has some influence, we are working on better handling in a corner. It isn’t a stretch to see that the distribution under the effect of g’s in the corner is most important.


I’d love to hear some feedback to this. Ask anything you’d like. If I’m wrong, a debate will only make us all smarter. And faster. ;)


Andy

[Rick]

Andy, that's a great explanation. But I think Jeff does have a point. There has to be a difference in the way a kart handles if Ryan (220lbs and 6'2") or me (170lbs and 5'11") drive the same kart. There's probably an even larger difference if someone like Chris Lupo (155lbs? and 5'3"?) sits in the same kart. Chris will probably flex the chassis the least out of all of us. Ryan will probably flex it the most. Chris will probably accelerate the fastest. Ryan will probably accelerate the slowest. This is all assuming that all of us drive exactly the same way.

I'm just guessing, but I would think that a setup specifically for my and my height and weight is probably not going to be the optimal setup for Ryan or Chris. For Chris to have the same forces to act on the kart and twist it correctly, he must move his center of gravity up. That way he will have the same leverage as Ryan at the same speed and same lateral G force loading. I think this is what Jeff is trying to get at.

I don't know the answer, but I would think that static weight distribution has to have some influence on dynamic weight behavior. That's why mid engine rear wheel drive cars are better than front engine front wheel drive cars. The static weight placement of a mid engine rear wheel drive car is much more optimal for high speed driving and cornering. Maybe that's not a concern in karting because the weight differences are so small, like you pointed out. But I think there has to be some effect, no matter how small.

[Jeff Salak]

All I know is I have a new Ribtech seat. Im going to scale it out right.

Last time i scaled my kart was with Johnny West at USKGP. He had it set-up and after runs he made adjustment as i know nothing. What I was amazed at was how little as a couple pounds of air and a front end adjustment and your karts weight was way different. Is it pyschological? maybe? I dont know? There nice to have.

I know they will be perfect as they are at Longacre service center getting a run through and calibrated.

I got a great price on them with a stand! Oh well!

My problem is that Im not that tall and the position for my seat is way up in the front. Plus when Im Road racing this year I may have 2 sets of holes to get me a little laid back. See if it that can be done with the same seat. Im still a newbie and will make plenty of mistakes at this. But I know i will keep trying!

Plus when I race Tag/heavy in Road racing I have to put 60#'s of lead on. I think I might need to know where to put it all!

[D. Harrington]

I am with Andy on this one.....seat position is critical. Set the seat to factory settings and go racing. As Andy has stated, this has worked for Birel quite well over the years in Europe and the U.S. I would recommend putting the chassis on a frame table once a year or anytime you have significant wreck to make sure the chassis is straight. However, many people are big believers in scaling the chassis.....I see some racers scaling several times throughout a race weekend. Do whatever makes you happy....have fun racing....we are looking forward to another fun season!

[Rick]

I've read and heard that seat position is critical and don't doubt that is the "magic" that will make you faster. I basically do whatever Andy and Les tell me and it has worked so far. They've been racing karts far longer than I have.

But I still think that the location of the weight on the kart must have an influence on dynamic weight, no matter how small or insignificant. For example, imagine if the seat were mounted on the front bumper. I'm pretty sure that kart would not handle as well as one mounted per factory specifications.

Maybe this has all been calculated and engineered by the factory and the seat position is designed to work with the chassis to act as a lever to flex it. And perhaps, as Andy said, the tube diameter is more important to change as weight, load, lateral force, etc change than the actual position of the seat.

Since I have moved my entire TAG setup to a 32mm chassis, I have also opted to move my seat (the one Les and Andy mounted) to the new chassis. The previous owner had mounted his seat completely different from what Andy and Les did on mine. And since I was very happy with my kart last year, I just moved over my seat as well and mounted it using the same holes.