change C of G

After talking with one of the guys at Ardent on Friday I was told, that by moving the battery bay forward behind the servo. This will give the car greater cornering speed and change the balance of the car. Has anyone tried this and what was the results like.
I have a new chassis on order and will be building the second car like this also the servo will be facing backwards. I know James had a backward facing servo fitted on his car.
So over the next week or two I will be building the car to compare against my second car.

I did quite a bit of playing with CoG when I ran 1/10 WGT cars a year or two back and I guess a lot of the theory of those cars can be applied to the V12 chassis too. I've tried a few things on my V12 and, yes, it does have a big influence on handling and balance of the car.

In an 'ideal' world race drivers seem to want the weight evenly balanced over their four wheels. This gives each wheel equal grip and a balanced chassis. To do this the chassis must be equally balanced front to rear as well as side to side. However, with WGT cars the waters were muddied by the cars having very wide rear tires and relatively skinny fronts. In this situation a balanced car should have its CoG moved towards the rear of the car - the ratio of front to rear tire widths = the ratio of CoG to front axel to CoG to rear axel:-

(Front tire width) / (Rear tire width) = (Distance from CoG to Rear axel) / (Distance from CoG to Front Axel)

NOTE:- few racers can drive a perfectly balanced car, it seems too twitchy on the track and loose on the rear, especially if it is rear wheel drive! We get over this with stiffer front springs, harder front tires and more additive on the rear. These are easier to change than the position of the CoG at a race!

On the V12 chassis we have an extra problem in that our tire widths are the same front to rear and, when built 'as kit', the CoG is very much towards the rear. This is even worse if you use 4-cell rather than the lighter 1s LiPo cells. The V12 wheelbase is around 205mm but on my car (with all electrics is a prety much standard position and no weights added at all) the CoG was about 75mm forwards of the rear axel. This is not good - I would have to either cut my front wheels down to about 13mm width, use massively hard front tires or put up with much too much front grip.

However, my car also weights in about 65g under weight. I did a bit of jiggling with the position of the electrics - moved my servo to the left hand side and about 8mm forward (it is a Savox 1250 so nice and small) and then moved the speedo to the left hand side and as far forwards as I could as well. I also shimmed the motor 2.5mm away from the motor pod. This combination prety much sorted the side-to-sode balance out and also moved the CoG a few mm forwards. I then added my additional weight INSIDE the front bumper, ie well infront of the front wheels. This had the effect of now giving me a GoG split 112/93 front to rear.

On the track the effect was impressive. With no CoG alterations my car would twitch violently into high speed corners and risk oversteering or grip rolling at the apex and understeer badly in slow corners. With the CoG alterations I have a much more neutral car - it carves its way through fast corners better and is much more positive in the slow ones too. I have also gone to similar spring rates and tire compounds front to rear and even add some additive to the front tires from time to time!

Having a forward servo might well do the same thing as me adding weight to the bumper - it will certainly move the CoG forward with just that change but it will also allow you to move the cells forward plenty too. Since these are the heaviest movable part of the car this will certainly alter you CoG! My concern though is wether ot not you will be able to mount your servo so the servo saver is still mid-chassis without interfering with the wishbones. If it is notdead centre them I am worried as to how having uneven track rod lengths will affect Ackerman and steering...

James

Thanks james for the info seems like you know what you are talking about mate your comments i have taken on board, and i will mull these over the next few days.
thank you again cheers paul

going to build a second car to try this out and see the diffrence

I've used a low profile servo on my circuit dave and this has allowed me to move my battery tray forwards by 20mm, I have also drilled holes to mount the tray 10mm forward as well. So I have three possible positions for my cells to give a bit more adjustability to the chassis.

Some good info there james, currenlty trying to work on improving the CoG on my mardave, what would you say is a good weight balance on the front and rear wheels.
I have got a very small ko propo servo and that has allowed me to move the lipo 45mm forward then all electronics not including the servo and personal transponder to the rear where the battery used to sit. But this has not really made a difference I have only losted about 1% from the rear will keep working away at it. With moving the esc further back it is now sitting just about on top of the motor so will be able to shorten the motor wires and put a smaller sensor wire in place this should help get some weight of the rear and more weight balance up front.
Just a quick one about drilling holes in the chassis, as I know that a few years ago you where only permitted to drill 4 holes in the chassis, has this changed!!!

Guys its all down to your own driving style what suits one driver wont suite others. . .

If the car and you are doing well then leave it as is just do a fine tune on springs and tyres along with additive like full or only half etc dont swop any thing else other wise you end up changing even more just to get it to go like you had in the first place

been there done that what a waste of time and headache