Changing COG Dynamically

[69CSTranger]

So I have been thinking about this for a while.

Some test aircraft have large water tanks built into the aircraft and pump water between them to simulate rapid changes in the aircrafts COG, such as cargo shifting or people moving about the aircraft.

What if a vehicle could change their COG in relation to movement?

I imagine a box mounted in the bed of our trucks with 200-500lbs. of ballast and the box would move on two axis inside the bed on a frame bolted to the bed. The box would be attached to accelerometer, similar to what is in your iPhone, and controlled by a computer.

The box would move to the right on a right hand turn, and move to the rear right, on a right turn involving braking, etc. When you brake hard in a straight line the box moves to the rear of the truck.

What do our resident track and suspension gurus think?

[theastronaut]

I think the weight added would counteract any gain from better handling or braking. 100 pounds roughly adds .10 second in a 1/4 mile. You'd lose one tenth at the end of longer straights for every 100 pounds of ballast added.

[69CSTranger]

It wouldn't necessarily have to be ballast, it could be the battery, fuel cell, etc. But even if it was ballast, vehicles that handle and brake better, do far better on race tracks than high horsepower vehicles.

Much of the time one can't hit WOT until well after the turn, because of oversteer. If that distance was reduced because you're cars weight distribution was better, you may not be able to accelerate as fast, but you would begin accelerating earlier. Then you would brake later, carry more speed into the turn, accelerate earlier.

[Ziegelsteinfaust]

I read an article about 15 years ago where Mercedes did it for some European road course car.

Yes the concept works, but unless you have to build up to a weight it is not a good idea. Mercedes used a trick of the rule books to do it, by putting a big motor into a smaller car. Then they had to add ballast, and this opened up to staging the car the way they wanted. The car had rams that would move the ballast from left to right depending on which corner they were at.

If I were building a pro-touring truck I would just concentrate on keeping weight centered inside the trucks frame the best I could. Other then that your throwing tons of money at smaller, and smaller gains.

One guy I read about years ago as the pro-touring craze got started built a road race ready C20 for a hair under $10,000. Yes he bought lots of things of CL, and it was built to a class. He was able to run with prepped Porsche's, and other exotics. Plus the guys who beat him in the had many many many more times the dollars he had into his truck.

[87chevy.com]

why not make the truck handle better with better suspension parts instead of adding 500 lbs of weight?

[6 Door King]

your post sounds like me in Mech Eng. school. I tried to convince the instructor that electromagnetically dampened shocks/struts would improve our school's cart for IMechE racing. It would work, but is it worth all the money for just that bit of an edge?

[BMERDOC]

Seems like a good time to share something that has been out for a while...

BMW has Active Roll Stabilization (ARS) It works in concert with ABS and DSC (Dynamic Stability Control) and EDC (Electronic Dampening Control) . Sensors in the car measure Steering angle, braking, acceleration, yaw, fore, aft and lateral movement in the vehicle. The sway bars are hydraulically controlled to twist causing the car to turn flatter in the corners. Its not changing COG but you would effectively end up with the same result.

Heres a video of start-up. You have to perform the start-up procedure anytime the module is reprogrammed or one of the bars are replaced. Its always fun to watch. This is what a car looks like when you put powered sway bars on it!! LOL!!

http://youtu.be/ngOjtS5WQ4o

[69CSTranger]

It's all hypothetical at this point.

But if you had a truck with great suspension, as light as possible, then you still have this large open area in the bed. And if one could drive to a track, bolt in a frame, add some ballast, and then the truck would perform much better, why not?

The point is how to use the large space in the bed to make the truck handle better. I only see the benefits of actively controlling COG, and not much downside. Cost would be an issue in development but how much would a frame, two electric motors, and small computer with accelerometer really cost? A few hundred bucks? And if it drastically increased the performance of your pro touring truck by using a large empty space? Plus have another 'gadget' to show off on race day?

[mongoose]

pmoi > cog.

cog is useless you're you adding weight to make the numbers... imo.

[69CSTranger]

Moving heavy objects around the vehicle is how one changes PMOI if I'm not mistaken.

Changing the CG dynamically would also change the PMOI dynamically.

[mongoose]

Yes and no.. it could and would.. but i cant see it being beneficial. pmoi is to do with changing directuo. And you want a lower number.. to get a lower number you need to off set the cog.... its kinda two steps forward one step back... so just adding a bunch of sandbags just before the rear axle will do the same thing.

Where to get a decent set up imo youll want to lighten the front end as much move stuff to the center like the battery, fuel cell, rad etc. Even move the motor back.. then try and set up for the most mech grip you can. so you can have your cake and eat it too..