XRAY - Model racing cars

I really need to understand something...why is it that Mr. Hudy went from the rear mounted motor style T1R platform, to the now common side-motor style platforms? I ask the question from an engineering/physics point of view...it just doenst make any sense to me that a car could be better balanced or perform better with a motor mounted on side, versus one on the rear and down the center...what's the idea. Even in real race cars, there are no cars that I know in F1, Indy Car, etc, that have such a set up- everyone tries to keep mass/weight as low and centered as possible...so why in RC cars do we see this akward set up of putting the motor to rear and to the side? What are the advantages/disadvantages of this car set up? If Mr. Hudy would design a T2'007, but a rear motor version, I am sure it would just as fast and realiable as the current '007 kits; however, I think the car would be easier to drive and balance, wouldn't it? Please help me understand the physics behind these concepts...thanks

Keep in mind that a rectangle has more mass moment of inertia than a square.

Keep in mind that design is all about compromise.

You want to have a low center of gravity, and a mass distribution that allows for a favourable polar moment of inertia about the X, Y and Z axes, allowing the car to rotate best about these axes while still maintaining the proper weight balance to all 4 wheels.

There are set components that need to be on a car (motor, batteries, servo, etc) with pre-defined sizes....the designers look at methods to configure them for performance and user friendliness while still being mindful of the distribution of these masses.

Add to this, the requirement for drive efficiency and you can clearly see that there are many factors that a designer must focus on in order to optimize a chassis design.

thanks tot he Canadians for their replies...however, are you trying to say that Mr. Hudy/Xray examined all thse variables and came to the conclusion that the best design is the curent popular side mounted motor design? If so, then I'd love an explanation as to the how and why, so I could understand it better, since this is the part that I just cannot see...what are the advantages of side mounted motor belt car over the rear mounted centerline mounted belt cars, like a T1R or Losi TYpe R? I know Mr. Hudy is the best in the business, and for sure there are things that made him switch over to the common side mount motor platforms witht he FK04-T2...its just that no body else seems to care to explain this over to us engeneering/scientifically challenged...

Chris P was on the nose. There are so many factors to consider.

Real race cars do not have to deal 1/4 of their weight in the form of a long rectangle object that has limited mounting options. Also handling at the SCALE speeds reacts a little different than 1:1 There are several CAD programs out there that will simulate a full range of real world scenarios at any imputed conditions.

2 problems with some other layouts (expeirenced here myself) is that especially in rubber tire weight transfer is crucial and chassis roll is big. one needs to set low roll center to get any transisiton in corners and that effects handling tgraffic and other high speed manuveurs. Also practically speaking the layout and battery install is such a pain I'll never go through that again.

That said the general approach seems to be to balance the batteries against the other electronics to facilitate ease of pit work....then take that basic principal and make it as LOW, Centered, and functionally sound as possible. All Xray specialties. work around that all the tuning and suspension options possible.

I suspect their are other design options but again it is all about compromise of : Handling, practical and economical feasability, Marketability (including ease of maint.), and great engineering design and knowhow

Edited by ChrisP - removed reference to other manufacturer

There are two key factors that were the driving force behind the current motor positioning:

1. Todays motors and batteries create loads of torque.
2. Corner speeds are extremely high (full scale equivalent of 500Kph!).

Taking point 1 first. If the motor is at the rear of the car it generates more front-rear weight transfer when going on or off power. With the motors and batteries we ran say 5 years ago this was no problem and even helped us a little. Nowadays however the torque has grown so much that even top drivers often have difficulty controlling the car when going on or off power. Moving the motor more towards the middle (i.e. more to the front) we reduce the weight transfer and thus make the car more driveable as it is simply more stable. In fact in 1:1 racing this is done quite often as well in socalled midmotor designs.

Point 2 is just as easy to see. If the motor is on the centerline the CG is higher. With todays cornering speeds we get too much side-to-side weight transfer (and resultant chassis roll). Moving the CG down reduces that effect allowing faster cornering. There are two basic methods to do that. One is to keep the motor on the centerline and move the front and rear belts more to the outside so they go around the motor. The disadvantage to this is that the torque generated through both belts causes the car to have torque steer. The alternative is to keep the belts in the middle and move the motor out. Also may cause some torque steer (but less) but obviously leaves more room in the car to position for instance the battery.

In all, at the moment this is the best compromise. But off course things keep changing which also means design compromises need to change as well to keep having the optimal package.

Can someone please help me with a low traction set-up please. The track I run at has new carpet, that new fast track stuff, I would say about 9 race weekends old. We only race on Sunday and get a bout 10-20 racers. We use Jack the gripper, so needless to say it has like no traction. I have tried just about all the team drivers set-ups. My car just keeps pushing in the corners. I swiched from another brand car to a '007 in January. So far I'm not liking it. I told my self I would give the car an honest try to get it to work for me until another brand new car comes out and If I still don't like it I am switching back. The car seems so hard to drive.
I would really appreciate some help, the last thing I want to do is have to try to sell my '007 to buy another car.

Please post your current setup in the set-ups section and describe the kind of problem you have in a bit more detail. Is the car pushing in all corners or only in tight low speed corners for instance?

I had exactly the same problems with my 007 EU edition. But everything is ok now and the car is very fast.

I use Jack the Gripper too, on rubber tyres, the trick is to try and let it dry naturally, then wipe it off, even it that means doing it the day before.

I use the stiffest chassis settings.
40W front and rear.
6.5mm ride hight, this influences the overall roll centre of the car and makes it much easier to flick in a chicane.
Silver D=1.5 17.5LB springs front, gold D=1.4 14LB rear.
Rear - 2 degree toe in, 1.5 degree camber.
Front - 0 degree to in, 1.5 degree camber.
Ball diff front and rear set so that when you grab one wheel and the spur it is very difficult to turn to opposite wheel. Both diffs are extremely smooth though

To be really honest, I started with the basic set up in the instruction manual then used the accompanying cheat sheet to work the rest out.

I posted my current set-up in the set-up section. I didn't state it in my other post, but I am running foams on carpet.
I even called Ralph Burch about a month ago and he was really helpful and spent like 45 minutes on the phone with me giving me a set-up. I think the problem is that my track has no traction and the set-up he gave me and the ones the other team drivers use are for paragon high bite tracks. My car seems to really push in tight corners, but it is also hard to hold a line in a sweeper as well. I mean i can do it, but it is hard to do. Like I said, it just seems so hard to drive, like I have to force the car to do what I want it to. I'm an average driver, but when I can pick up my friends FK04 and it I can drive it better than my '007 there is somethiong wrong. My frind has other brand shocks on his FK04. I wonder if the shocks make a difference. Thanks for the help guys

Did you try one of the team setups from the IIC in Las Vegas last year? For instance from ?

At the IIC grip was not optimal despite being a big event. The race was on new CRC carpet too and off course Jack was the only additive allowed.