rc corner weighting

[peteboo35]

im playing withthe idea of making corner gauges to set cars up any 1 with any ideas im thinking ov small bar ona hinge and sum small digi scales

[James]

I think you need to describe that better...?

Scales under each corner isn't accurate..

[Teaboy]

Originally Posted by James

I think you need to describe that better...?

Scales under each corner isn't accurate..

Why are scales under each wheel accurate? this is how we set up the full size F3 cars and is spot on.

Cheers

Rich

[Karting]

Have to agree with above, corner scales are accurate, we also use them on bigger scale kart and comp car stuff.

Buy 4 mini scales

[PTRU]

only if you use flat patcth and or if they are all level to each other then it will work for both f3 / any large car or RC cars.

[Frecklychimp]

To get it accurate and to be able to use the data from scales properly you need to get a consistant contact patch between scales and car... standard tyres are too soft and corrupt results

for full size cars with slicks we inflate tyres to 80psi all round to make them hard enough to give good readings and so its consistant.... plus they are kept as set up wheels/tyres and not used for anything else other than weighting or geometry set up.

if you had some set up wheels with solid rubber rings to grip scales then it works... i've tried to master it a few times but couldn't get it accurate enough to work like 1:1 scale

I've found that balancing wheels after fitting tyres on offroad cars is more beneficial and does make the car more consistant and jump flatter, it doesn't take much vibration to throw the handling out or the car to one side when its in air!

[sosidge]

The easiest way to corner weight is 4 scales on a level surface. I use some inexpensive kitchen scales.

The results are not innacurate - but they can be a bit misleading. Because RC cars are built with larger "tolerances" (ahem) than full-size cars, you can end up with a different result every time you put the car on the scales. I don't get obsessive about the corner weights any more, but if I have one wheel that is, say 30gm more loaded than the others then I will give the car a good going over.

The scales are very useful for measuring weight distribution. Even though the corner weights can have quite a large tolerance, the left/right and front/rear sums are always spot on.

[James]

The corner weights on a set of 4 scales are not accurate - unless you car is built perfectly which is never the case. You can do it accurately by replacing the shocks with rigid rods and make sure the car is not tweaked corner to corner whatsover, plus do this upside down aswell, I bet your shock towers aren't equal if you check the tweak.

Or)

Put a pivot point under the centre at one end and measure the opposite two wheels, turn the car round and repeat.

[SlowOne]

The natural 'stiction' in the suspension system will always render results variable - as James suggests that can be overcome by replacing the spring/damper units with solid rods. However, when you put the shocks back on that will alter the results again.

If you use four mini-scales, then it will tell you your front/rear weight distribution. If you need to balance the car side to side, then use some balance buttons not the scales. Use the 'lifting' method front and rear to make sure the shocks are equal length.

If you are going to use corner-weight scales, then go by the maxim that setting up this way is a matter of being roughly right, and not precisely wrong. HTH

[pasl333]

4 scale is not give the accurate result some times these scale give the wrong weight show in the result..I personally use the truck scale for the weight because its have high capacity to lift the weight...

[BazzerH]

I use 4 small digital scales, all you're looking for with these is your front/rear balance and your left/right balance. With a pen and paper take all 4 weights FL, FR, RL and RR

add all four for your total weight
FL+RL / TOTAL WEIGHT = left bias % (should be 50%)
right bias = 100%-left bias%

FL+FR / TOTAL WEIGHT = front bias %
Rear bias % = 100% - front bias %

I run mid motor 2wd and my front/rear ratio is something like 33/67
It would be interesting to hear what others ratios are.
For 4wd I believe 50/50 f/r is preferable

With this method the results are easily repeatable and accurate and no need to worry too much about individual corner weights. you can also just use 2 scales and blocks to keep chassis level whilst you take each corner reading.

IMO use of solid bars, set up wheels etc isn't necessary

[cornishboy176]

This is how I calculate it

Weigh Front - 535g

Weigh Rear - 924g

Add together - 1459g

Divide Front weight by overall weight - 37%

Divide Rear weight by overall weight - 63%

This is the way I got shown years ago,

Hope this helps

[BenStephenson]

[QUOTE=Frecklychimp;680837]for full size cars with slicks we inflate tyres to 80psi all round to make them hard enough to give good readings and so its consistant.... plus they are kept as set up wheels/tyres and not used for anything else other than weighting or geometry set up.[QUOTE]

Only problem is when you run the car with the 'Race' PSI in, you will have changed your corner weights.

[Frecklychimp]

[QUOTE=BenStephenson;780386][QUOTE=Frecklychimp;680837]for full size cars with slicks we inflate tyres to 80psi all round to make them hard enough to give good readings and so its consistant.... plus they are kept as set up wheels/tyres and not used for anything else other than weighting or geometry set up.

Only problem is when you run the car with the 'Race' PSI in, you will have changed your corner weights.

Rubbish!

Corner weighting a full size car with lower pressures will result in the tyres compressing and giving false inaccurate scale readings.

You set a high 'constant' pressure for accuracy,

The wheels and tyres are unsprung weight and do not effect the corner weight forces

you need to understand the principles and reasons for doing this... it's to set 'sprung' weight balance using suspension adjustments and to give values in order to calculate centre of gravity etc

also on a track tyre pressures change with running temperatures and unsprung weight changes as tyres wear.

[goldy]

I think you should go out to the garage and actually try that theory then come back and tell us what you found. Set all the tyre pressures to the same pressure and jot down the weights, then let one tyre down say 15psi and tell us what you find. You are altering the ride height of the vehicle exactly the same as going up or down with a spring seat which alters the weight on that corner and the corner diagonally to it. If you turn the steering, the change in castor angle will change the scale readings because the height of the vehicle changes. Unsprung weight has nothing to do with it

[BenStephenson]

So your telling me the weight would stay the same on 1 corner if you reduced the pressure in that tyre.
Also i dont know what scales you use but setting a car up in its race trim i.e pressures, fuel, driver with helmet etc, gets accurate results down to a KG. At least this way your sat in the car on the line knowing you have exactly the same car that was setup. Even the tyres you run (Radial or crossply) have an effect.
I do understand the principle of doing this.
So if you take your 80PSI all round and adjust 1 corner half a turn on suspension to shift the weight you could be over exaggerating the efffect when running the tyre at 25-30PSI race pressure.
Just something i have noticed when setting up single seaters.
everyones got there own way though.

[QUOTE=Frecklychimp;780401][QUOTE=BenStephenson;780386]

Originally Posted by Frecklychimp

for full size cars with slicks we inflate tyres to 80psi all round to make them hard enough to give good readings and so its consistant.... plus they are kept as set up wheels/tyres and not used for anything else other than weighting or geometry set up.

Rubbish!

Corner weighting a full size car with lower pressures will result in the tyres compressing and giving false inaccurate scale readings.

You set a high 'constant' pressure for accuracy,

The wheels and tyres are unsprung weight and do not effect the corner weight forces

you need to understand the principles and reasons for doing this... it's to set 'sprung' weight balance using suspension adjustments and to give values in order to calculate centre of gravity etc

also on a track tyre pressures change with running temperatures and unsprung weight changes as tyres wear.

[Frecklychimp]

You have a PM Ben,

this has nothing to do with toy car racing, but will happily discuss with you

[smokes]

lads the tyre is a Spring damper and will throw of the readings if the ride height becomes uneven which shift the cg left right front rear of the design static C.G.

Ideally the process of corner wighting is to first set your sprung mass up by using a non deformable wheel at the correct ride "ideal" height as the springs are not pefectly equal length or rates even if they are "matched" and the damper seal friction can cause issues.

Then put your race wheel and tyres inflated "hot tyre pressure" using the same guage to race pressure on hopefully matched to eliminate stagger and ovality. Then check your race height because the walls on the tyres do not deform equally under static load you will see that the corner weight will get thrown off. if you have "perfect " wheels and tyres you won't

Take the tyre AND wheels off then adjust the ride height on the solid wheels to and recheck the corner weights.

This will eliminate the varibles that you can control from the variables you can't control.

but it is expensive and time consuming to do this and a 7 post rig is the better faster option and will fine other issues such a sieazwd CV joints a wheel stiffness deflection etc..