OscarF1

Re-building the upper and lower deck of my 1:10 electric touring car,
I was surprised to discover the strange distribution of weight on the four wheels.

On my car the right front wheel carrys 110 grams more than the others.

Re-designing the upper and lower deck, I managed to get an almost equal distribution of weight on all four wheels.
In order to achieve that, I had to move the battery more to the center ( always better ) an to the rear.

Testing the car it worked really well,
the car has en good balance and a predictable behavior on the track ( MACH Heemstede Holland ).

Unfortunately I am not familiar with the balance of other cars,
and I have no knowledge about any theory concerning weight distribution.

I noticed that with the transition from 6 sub-C cells to 5 cells,
most drivers choose to leave the rear hole empty.

This means that the CG moves slightly to the front.

What would be the ideal place for the CG ? ( top view )
And what consequences does that have ?

Tucker101

iTrader: (-1)

I might be able to help you there and i might not, i have heard that if you have more weight over the front it will there fore produc more grip because there is more weight pushing that end down, but it you feel you need more weight over the back then just push it backwards, Team Associated have had a look at this by having space for seven cells on their TC4 and fill the empty one with a foam spacer so the battery wont move around but if you need more grip or are on a low grip track just push the battery backwards and it should give you some more grip they say. The weight distribution is something i have never thought of but im not really crazy about racing as of yet im gonna get more into it when i get my new car. anybody else correct me if im wrong because i only have a slight idea what im talking about so i could be wrong haha.

Tucker

sosidge

Certainly the ideal place for the CG is along the centre line of the car, so you have even balance in left and right turns, however it's fore/aft position can be varied for different performance.

Most 4wd touring cars have it relatively central or slightly towards the rear of the car. Look at 2wd buggies and they have it well to the rear of the car.

The axle with more weight on will have more grip, however it will also have greater inertia so will be less responsive to changes of direction as well.

gonzo416

iTrader: (39)

you can place the battery to the front for more stearing but now the car will not be balanced because the battery is on one side of the car. to get the car to handle equally and consistently the chassis should be balanced so it will react equally and notice any change in setup or when car is tweaked. my problem is how to go about balancing a chassis (equal weight at all four corners of the car at at legal weight). i have heard people using 4 scales.

OscarF1

I used one scale and 3 woodblocks for the other wheels.

In my opening post I mention rebuilding my touringcar,
but I meant Redesigning it.

mangobanana

WOW nice ta05

mattnin

iTrader: (44)

This is a perfect explanation. It should be noted that with an increase of weight on the tires, there will be a decrease in side bite.

Probably the simplest way to think about it is like this. If you get a shopping cart and put a case of pepsi in the front of the cart, it is will be the most difficult to steer. If the pepsi is put in the middle of the cart, it will be only slightly difficult to steer. If the pepsi is put all the way in the back of the cart, it will be the easiest to steer.

With an increase of weight, there will also be an increase of slip angles. A car with a neutral weight balance with the same weight on four wheels pretty much steers in the direction the front wheels are pointed. A car with a front heavy weight balance requires a greater slip angle so the front wheels are turned more to achieve the same heading as the neutral steering car, so this car is actually pushing. A car with a rear heavy weight balance has greater slip angles in the rear of a car, therefore the front wheels don't have to turn as much to get the same steering radius as the neutral steering car, so this car is oversteering.

OscarF1

What would be wise,
the CG in front of the center or just behind the center. ( top view )

And what would be preferred for a short carped circuit,
and what for a long asphalt circuit ?

sosidge

Personally speaking I have found that the cars with the weight further forward are better suited to tighter tracks.

Might not suit you though! Experiment.

Rob Janssen

I normally run the batterie in the rear of the car.
Last weekend at the LRP Masters I tried the batterie in front and the car
was much easier to drive and went from oversteer to a little understeer.

Rob Janssen

OscarF1

Could this mean that on a small circuit
its better to have the CG more to the front,
and an long highspeed circuit more to the rear ?

mattnin

iTrader: (44)

Well ya gotta play with the CG to get to what you want.

Having the CG forward of the center of the car adds stability but increases understeer. However, on tight tracks with slow turns, you will actually have better steering. If you have high speed turns, you will understeer with the CG too far forward.

The further rear you put the CG, the more unstable it gets but increases steering on sweeping or high speed turns.

I'd say start with the CG right about center of the car, or a little forward of center. If you feel you aren't steering enough and the car is too stable, move the CG back and keep moving it back until it gets to the point where you have too much steering and the car feels too unstable.