sosidge

Just bringing this up again...

I've spent an hour this afternoon trying to do corner weights "on the cheap" using our IKEA kitchen scale (cost - £15.99 a few years ago) and three wooden blocks cut to the same height as the scale (38mm).

And all I have proven is how sensitive corner weighting can be!

Plan was to put blocks under three of the wheels and use the scale on the fourth to get a reading. But the results were wildly inconsistent.

Reason being that I had hand cut the wooden blocks. Although the tolerance between them was only around 0.5mm, certainly less than 1mm, it was sufficient to completely mess up the readings on the scale.

Depending on how I had the blocks arranged I could get a difference of up to 50g in corner weight (with a typical reading around 350g!).

I also noticed that even 1/4 turn on a spring collar could make a significant (10g+) difference to a corner weight.

Stetler17

iTrader: (6)

Doug,

I've spent a lot of time lately playing with my dirt oval car on the scales. The above noted issue of the scale height accuracy has been my biggest nemisis so far. I've even went as far as using the laser sight sytem from my big car scales to try and get them perfect, but the small amount that they can be off and cause inacurate readings on these little cars is unreal.

On to your actual question about ride heights.

Once you use actual ballast to get your desired Left/Right and Front/Rear balance, which will not be effected by coil spring adjustments, you can start to balance your ride heights and cross weight. If you see that the ride height from say the LF to RF is off but the cross is spot on, or balanced as you would want on a touring car, you should be able to make corresponding adjusments at all four corners to restore the ride height without changing the cross. If the cross can't be balanced with the ride heights all at their desired location then one corner of the car must be heavy or light and will need ballast moved. Example, if the RR has a lot of physical weight on it you will always struggle to keep the ride heights correct and the cross weight balanced. This may be an over simplification or way off from what you were originally asking.

On the big oval car using the old method of changing cross (tweak) without changing ride heights by going equal amounts on all four coilovers is very effective, turn in RF/LR, turn out LF/RR. The inverse of that will change ride height without changing tweak, turn in RF turn out LR Again, if that messes up the ride height at the other end of the chassis, ballast will need moved.

I'm far from an expert on these small cars and especially road course stuff, but from the outside looking in I would think that there has to be a ton of trial and error and ballast moving before one of these things is as perfectly balanced as you would need.

What about it experts? Does it take forever to get it right, or are they pretty well balanced from the manufacturers?

Big B

iTrader: (4)

If you don't already have a copy of XXX Main's Touing car Setup Book pick one up, it explains chassis balancing really well. Hudy make chassis balancing tools for L to R Balancing, and The MIP Tweak board is a great tool as well.

mattnin

iTrader: (44)

I don't claim to be an expert at this either, but I do try balancing my cars too. I made a 4-scale system for my off-road cars. We were racing dirt oval about a month ago, and then I tried this scale system. Immediately, I noticed so much steering after I did this. The weight balance was so far off initially.

I can typically balance my truck or buggy in about 2-5 minutes. I usually do a few setup changes like springs, oils, etc. I then re-adjust my ride height then I throw it on the scales. It is amazing too how well the truck stays balanced even after a few heats of racing. I would think the truck would become too tweaked even after a jump, but it doesn't.

Here is a picture I took one day after balancing my truck. It is a MF2 setup for dirt oval.

John Stranahan

iTrader: (27)

I thought I would post my procedure with scales. I use two. I measured the height with the height gauge. They are fine. Molded parts are generally pretty precise. I also use two 1 inch square beams and a 7/16 suare beam that equals the height of the scale. This just makes it more portable than 4 scales.

First I use a beam on both scales both fronts on a beam and both rears on a beam on separate scales. This Isolates your front to back weight (avoids any math). On a touring car for asphalt I like aobut 2-3 ounces heavier in the back. This keeps the car from developing a push on corner entry. Hopefully there is some ballast that you can move forward or back to make this like you want. This is done roughly on assembly of the car. On my 1/10 scale pan car I want as much on the back as I can get. 8 ounces more with body on. It only weighs 40 ounces.

Next I put left tires on a beam and right tires on a beam (on separate scales to get the left right balance where I want it. Usually dead even for road cars. This is done roughly.

Now I put rear tires on the beams stacked in the back and front tires on the two scales. This is very similar to the setup for a tweak station, but when I get the fronts to weigh the same, and reverse the car I will know how many grams off are the corner weights. If the corner weights are good then the rears become even at the same time. Ballast then needs to be moved a small amount to get the front tires to balance out even and the rear tires to read close to even when the car is reversed. If you only move ballast forward or back at this point side to side weights stay the same forward to back split changes a little. Perfection is not achievable due to friction. Just quit when you are close. .1 -.3 ounces is close. And of course bounce the front and back a couple of times before a reading.

Before doing this set your ride height on three corners. Ride height will be affected only a little by tweaking on the scales if the weight is put in the car correctly on assembly. You avoid this ride height change by going down with the shock collar a little on the light corner and up a little on the diagonal corner. 1/8 turn at a time.

Only really takes a few minutes on assembly, then tweak station or scales once in while at the track.

John

gonzo416

iTrader: (39)

where did you get the scales and how did you make the board? oh, and what was the cost?

mooony

Has anybody tried this system:




It seems quite good.

Ronald

mattnin

iTrader: (44)

I paid a little over $120 for the scales. I got them on sale though, $10 off each one. You can find them all at oldwillknottscales.com

I paid about $20 for the melamine board at home depot. It was a large board and I had them cut it to 18"x19". I also bought the contact paper at home depot for about $6 and a bubble level for about $5. I bought the leveling feet, leveling mounts, and knobs at True Value for about $20.
So the total was $171 if you can get your scales on sale. If you tried to do it today, it would be $211. Of course you have to build this all yourself.

I spent a lot of time buidling it, making sure everything was precise. I first applied the contact paper completely around board. It looked really sleek and black after this. Then I marked off the 4 corners where I would drill using a compass and ruler. I also marked off an area on the center of the board and put a skull sticker there which signifies the exact center where I can place the bubble level. I then grabbed the girlfriend to help me hold it on the drill press and drilled out the 3/8" holes so I can insert the leveling foot mounts. I also used the grinder to grind a notch in the top of the leveling feet so the knobs would grab it when I tighten the set screws (if you do this, make sure you get the leveling feet with at least 2" of adjustability). The rest of the work was just putting everything else together, applying stickers, etc. It works like a charm :-)

gonzo416

iTrader: (39)

moony, how much and where do thhey sell these?

mooony

Gonzo,

I found this on a german site and the cost 325,00 EUR:

http://www.rc-cars.de/

Search for this code: CSE-J30030 in search box on left.

Here is the site that makes them:http://www.jrp-technology.de

The price seems very high but it looks good.

Ronald

xtaiji

Just $40 for 4 scales.

vroomtshh

I spent a lot of time trying to balance my car like this, up until recently, where Andy Moore said he did not bother, and most of the other top touring car drivers dont bother with weight distibution, so long as tweak is ok.

I think balancing the cars is probably more important to those of us out there, who dont have the responses of a world champ though

CAlbrecht

I know lots of guys use individual scales for setups, but it seems like there is a "black art" to it, and no one wants to give away their secrets. [/QUOTE]

Cause it doesnt work..I know of a guy who uses four scales on his middle battery car and from what I see its crap...MIP tweak station is all you need..

Or buy four 300 dollar each scales and get the same outcome..

Hurting

Skiddins

This shot was taken with perfect tweak on a setup board set with a spirit level. I haven't been near some bigger scales to see what the overall weight is.

When I've had to add weight to the car to make it reach the 1500g, up a 10g weight in front of the cells etc only ends up making a couple of g difference at the wheels anyway.

Johnny Wishbone

iTrader: (6)

Just a couple of things to note that no-one has mentioned but probably assumed. Make sure your tire diameters are the same L/R or that will screw up your readings as well. I don't think all 4 have to be the same dia, but L/R is pretty important since it would effect the jacking of the car. Another thing thats a little different from a big car to our TC is they generally are using a straight rear axle and not a independant rear so there are some variables that don't work the same. In principle yes, but physical dynamics are different. And of course there is the issue of sprung and un-sprung weight and how this is placed for different purposes. Tweak and weight balance are two different entities, the one that makes the most handling difference is the tweak setting or corner weight down pressure. Try this with one scale, place your car on your table and just put the scale under one wheel at a time and measure, that will give you the same measurement as a tweak bar would but only with a number instead of a level bubble. Also one other thing to take note of is making sure your front steering stays the same or at least straight as per your race setup, as the slightest turn one way or the other is going to fudge your readings too, and thats in the front and back opposite corners.