Shopping-cart physics

  • Thread starter Thread starter Sakiale
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Sakiale

Sakiale

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Like some of you, I am one of the nutters that is addicted enough to walk in a racing line and drift shopping carts in supermarkets.

Case in point: I am at the local Stop&Shop, with my mom, buying groceries. I start handling the cart like a race car, with racing line, reverse 180, and most commonly, drifting.

Today, I had an idea. After finding out about ballast weights in GT4 yesterday, I thought 'what if I weighted the wagon with groceries?'
So I experimented.

I found that when I put a lot of weight on the front, say 70/30 distribution, the back wheels would lose grip really easily, and start to do a perfect drift. I could even do perfect 90 degree turns without hands. But if I put more, or less weight, it would go back to being hard to drift.

Since I am only in high school, I still dont know too much about physics. And Ive never had the opportunity to drive a car, besides some boring steering on a highway, and shifting.

What I would like to know is, how does weight ballasts and distribution affect a car's handling? Now, I realize that a shopping cart is quite different from a car, but were their behaviours the same? Shouldnt more weight in the rear help drift the car? I know that MR cars tend to drift more, especially the NSX in Gran Turismo 1, but I remember seeing something about braking in GT2 that says weight transfer to the front will help induce drifts...

:confused:

Please help me understand this. It would be greatly appreciated.

Thanks,
Sakaile (misspelled in username)
 
Oh, thanks a lot! That looks really helpful.


HA! And my mom thinks I'M a crazy nutter...

I wouldnt hesitate to do any of that if she let me...


We need a shopping cart racing league-- lets send in videos of shopping-cart drifting!:lol:
 
I'd say try and get something dense and heavy underneath. Dense because you don't want to it take up too much room (liquids would be good for this) and heavy because you want a fair amount of ballast. You want it low down to keep the centre of gravity low. Depending on what kind of handling balance you want you obviously have to position things carefully. I used to put the heavier items at the rear and the lighter ones at the front, probably a 75/25 or 80/30 weight distribution. Balance was towards oversteer but not too much, helping to point the front wheels towards the apex on turn in through to mid-corner. Power oversteer was quite easy to induce with so much power at the wheels.

Driving technique also plays a big part in the equation. With the above setup I found it best to be fairly smooth on inducing the slide, sudden movements would produce snap oversteer, almost out of my control. With smooth, progressive movements I was able to shift the weight smoothly and not overstress the wheels or chassis. A technique you might want to try is called the Kankkunen flick. If you're not familiar with it, it's a technique used in rallying to try to flick a car into a tight turn. It involves applying a quick burst of turning in the opposite direction to the turn then a snap back to the right direction of steering. This unsettles the grip levels and acts like a pendulum and can make those end of the aisle hairpin turns a bit quicker.

Something I considered (but was sadly not able to try out) was to add inverted kites onto the front and back of the trolley to provide downforce. The theory is sound, as I'm sure you'll agree, but I didn't have the time to put it into practice.
 
How exactly do you drift a shopping cart? You can slide a cart pretty easily, but I'm not sure how you'd sustain a drift without any sort of drive.

And no worries about the crazy cart stuff. At the market, I treat everything (and everyone) as an obstacle. I like to see how fast I can push the cart around without hitting anything. I've startled a few people with my aggressive driving :)
 
A Corvette steering rack will make your shopping cart 1,000 times better.;)


Anyway, that would be fun! I'm 17, and my friends and I still mess around with shopping carts. I got it: a 24 pack in the front, with a 12 pack and a 6 pack at the far rear of the bottom shelf thingy. 57.1% front, 42.9% rear. :dopey:
 
I forgot to mention before about dynamic weight distribution. When you accelerate or brake, the vehicle will be subject to a degree of weight shifting (depending on such factors as the ferocity of the acceleration and the setup of the vehicle). If you already have a rearwards balance and you accelerate hard, you throw more of the weight to the back and run the risk of unloading the front wheels inducing severe understeer. Not what you want if you're trying to slide the vehicle. Conversely, under hard deceleration you'll throw the weight forward and unload the rear tyres. This is good for starting a slide, but if it breaks away too quickly you'll be in trouble.

Another aspect would be changing your settings to match the venue and/or conditions. In a tight area you might want to move the weight distribution rearwards to improve turn in, whereas on an open area you might want to move towards the front to improve high speed stability and make the vehicle a bit safer. If you spot some spilt liquid on the floor you might want to move towards understeer to be safe on the wet surface.
 
It's simple. The cart doesn't have nearly enough inertia to unload its wheels alone. That, and it doesn't propel itself. When you give a sideways push to the cart, the wheels that you transfer the most energy to will slide. The front wheels with front ballast have a lot more friction against the ground with all that weight on board. You're also usually pushing to the side from the back of the cart. Therefore, the rear wheels, with much less friction against the floor, and much more lateral input will always break traction before the front.
 
Do this:

If you have a Traxxas or other gas powered RC car, and know a few others with some, get them.

Tie them all to the front of a shopping cart (probably not best to do in-store).

Adjust wheels, camber, toe and such as necessary.

Have everybody go full throttle on their RC's at the same time and enjoy.

Turning is tricky though. Everyone has to be synchronized.
 
okies, all you need is a spray can so you can demonstrate 3000BHP OF NAWZZZ!! and pull the e-brake to perform the perfect drift.. oh, no wait, that's FnF3.. :lol: want advice? drop it before the guards kick you out.
 
Another question--how/are these shopping cart physics similar to real cars, or to the weight ballasts in GT4? I assume that in GT4 you have to put ballast in the BACK for drifting. Please answer.

=]
 
So how exactly are you drifting without actually having power sent to the rear wheels?
 
interesting stuff 👍 made me laugh some time.......but as Mdnlte said, how do you drift without a drivetrain and power sent to the rear-wheels?

viper
 
MdnIte
So how exactly are you drifting without actually having power sent to the rear wheels?
Click to expand...

The rear wheels transmit the power provided by the engine (your arms on the bar) to the ground. If you push hard enough, the front wheels will lift, but the vehicle is still being powered...
 
Famine
The rear wheels transmit the power provided by the engine (your arms on the bar) to the ground. If you push hard enough, the front wheels will lift, but the vehicle is still being powered...
Click to expand...

Ah, I was assuming he was sitting in the trolley.
 
No, ~18 year old kids have a hard time fitting in the basket, much less the baby seat. I've tried. And then I flew into a bush.

You know, I've never seen any other kids drift carts through Kroger (the foodz place), so I think it's quite nifty that somebody is out there who thinks I'm not a complete "...idiot kid!".:lol:
 

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