XRAY - Model racing cars

Tony,
Thanks for all the advice, I've been lurking these forums for some time and everyone has been a great help. There is one subject that I haven't seen talked about and that is the why's of offsetting the saddle packs. I have seen and raced against several set-ups with this configuration, see Josh's Ohio set-up. Please comment on what your trying to get the car to do with that.
thanks,
push-

It is all about weight distribution. By moving three cells forward we get more weight bias towards the front. In fast corners this makes the car more easy to drive as the car will get a more natural tendency to understeer (bigger centrifugal force at the front compared to the rear). In slow corners it is the opposite as the additional weight at the front presses the front tyres down harder than at the rear increasing front traction.

So if you want more steering on fast flowing tracks move the weight backwards, if you want more steering on slow tracks move them forwards. Also, if the rear is stepping out on fast tracks moving the cells foward will keep the rear in check and if it does slide it will be easier to control the slide (with the weight at the rear the car will act as a pendulum once the rear slides out).

Fast flowing would be reeeaaallly fast flowing in US. I am talking European style 1:8th scale gas car tracks such as in Lostallo or Graz.

The trick is that the additional weight at the rear will be subject to a much higher centrifugal force than the front. So assuming you have enough grip to avoid a slide the larger centrifugal force at the rear will help the car hug the inside of the corner as the car will have a natural tendency to oversteer without losing rear traction. Like I said before, once the rear does break traction you are in definite trouble as the extra weight at the rear will make the car snap oversteer severely.

In slower corners the centrifugal forces are much less important and it is the grip that the front and rear suspension and tyres generate that will be more important.

I hope it makes sense now as we are in the realm of more advanced setups...

That does help. I can't say that I've thought much about the dynamics of making a car turn in terms of centrifugal force front to rear. I'll have to let that soak in for a while. Given enough time I can usually turn the dials to make the car feel neutral to me, so it's that extra .10th of a second or making the car more forgiving that I'm interested in lately, so if there is anything else advanced you want to share I'm all ears. I am suprised that the secret secret prototype car has it's batteries all on one side.
Thanks Tony!

with the batteries all down one side. The car probably has wieght bias to each corner. Tony will know whats what, but I presume that this will mean wieght transfer during accel and decel will be the only affecting factors.

Tony i unfortunatly did not mean really fast. More technical but on power(carpet). It is more apparent on a sweeper as it is set at the apex and then iam full lock around the entire bend!

If i am already running 3 deg castor is it really wise or necessary to go 6!

I think both diffs are too loose but light,medium or tight is all subjective.

Well, that is difficult to answer as it depends on the track. I suggest you try it back to back and see what the difference is. BTW, if you have the FK you can also run 1.5 degrees kickup to get 4.5 degrees castor.

Given your desciption of the track I think you should try running more weight at the front. With the FK I allways have about 40 grams of weight right before the front bulkheads and often run the cells forward (XRC chassis) as well. It sounds like this will work on your track too.

Another thing you can try is to run a little bit more front toe-out and consider running a bigger Ackerman angle by putting the steering arms in the forward (#1) position on the steering block (don't forget to reset your EPA). This will make the car turn more aggressively but not everyone likes it. Andreas and Joel often run this way while Jilles usually prefers less Ackerman.

BTW, you guys do realize who the designer is right
Juraj is a genius in my opinion and you can trust him to get the weight distribution just the way he needs it to be

For those that have a little more knowledge in physics a little different way to explain is to think of torque.

When cornering the car moves forward and turns at the same time. Now forget the forward movement for a sec and just look at the car itself. First we need to understand that the car rotates around an axis in the middle of the car (it turns!). So let's assume the car is fixed in place by this rotational axis (it can now only rotate). Next consider that the front is light and therefore has a small centrifugal force while the rear is heavy and thus has a large centrifugal force (I know the car is fixed in place, but that is a conceptual model only in reality it is racing around the corner). Assuming the car is turning left these forces work on the righthand side. The force at the front tries to rotate the car clockwise and thus away from the turn (towards the right instead of left). The force at the rear does the opposite. This is because both create a torque around the rotational axis. Since the force at the rear is larger the force at the front is nullified and in fact some torque is left to rotate the car counterclockwise and therefore into out lefthand turn.

Longwinded, but you should get the picture now. The weight at the rear makes the car rotate into the corner effectively giving more steering. However if the car is going slowly the effect is too small compared to other effects to be a factor. At speed however....

Tony, as always, incredible insight ! On Josh's car he has 3 batteries on the left forward and 3 batteries on the right reward. A quick look and one might say that the weight would be biased on an angle. How does he get around this ? Do the rest of the electronics balance it out ?
Thanks.

You are right, in principle there would be a weight bias. But this is why we de-tweak the car, either using a tweaker board or using the method in the XRay and Hudy described setup booklets. Personally I use the latter.

When you de-tweak the car what you effectively do is setup the spring preload on each corner of the car in such a way that the left and right front carry exactly the same amount of weight at rest and the same for the left and right rear tyres. I am sure Josh does the same.

Sounds to me that he would certainly do this. Else left and right turns would have a slightly diff effect. Unless of coarse this is disired !

I only have the original t1 did anyone actually have one of these

LOL some people must of brought them as Xray is still here and getting better

Well my point is did anyone else find the car to be like this Mario ? maybe you would know t1 with c-hub fr+rr

I will try the ackerman setting, is this the connector at the wheel tony ?