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Do Shopping Carts use Positive or Negative Caster?

ABC Nightline has a 22 minute segment "Shopping Cart Design", but does not address the caster issue very much:
 
When you get right down to it, it doesn't matter on a shopping cart.
 
Every one knows that positive caster has a tendency to keep the wheels straight and to return them to center after a turn. So try this. Go down to your local grocery store, find a shopping cart, and spin the front wheels around, so the wheels are sticking out front in what you call a positive caster position. Push the cart forward, and let me know what happens.
 
The shopping carts pivot point projected to the ground, hits it in front of the wheel where it meets the ground. Same as the motorcycle, bicycle, office chair. they all have positive caster.
 
Like this
Unknown-1.jpeg

C = caster
 
Somehow I always get one with the "death wobble" issue!
 
Here's my take on this. Positive caster uses the weight of the vehicle to steer it straight. Negitive does the opposite. My 60s style altered has plenty positive caster. Straight and stable at all speeds. Hard to turn at any constant speed. Now back it up. Like after a burn out. Need to hold on tight cause those wheels will flop over and lock up in an instant. Need to move forward to unlock em. And if weight shifts forward to fast the wheels can go into a death wobble! A tap on the throttle takes care of that. So what's the point? Sometimes you need extreme examples to clarify things. And shopping carts have no effective castor. As weight over the wheels does not cause them to "steer" in any particular direction. And nose gear on aircraft generally locks straight ahead then unlocks at a very low speed. That's it. Slice away! LOL.
 
Hey, don't forget that classic rear axle/suspension has its own caster and camber effects designed into it. It's in the chassis book. Check it out.
 
Hard to tell, depends how many times they’ve been run over in the parking lots
 
I wonder what our wife's woud think of us, about this deep, profound, technical spiritual, and philosophical discussion that we're having about shopping carts :bananaweed::realcrazy::steering::fool::lol:
 
Yet who actually depends on em more? We laugh at em. (The carts,,,mostly.) They take em seriously, I am sure.
 
Wow, I can't believe there's actually a debate on something that's so simply obvious.
 
Motorcycle, bicycles - positive caster.

Shopping carts, dolly casters - negative caster.
 
Kin always tell when it's winter time around here lol
 
I think the castor depends on whether the cart is being pushed, or pulled backward.

main-qimg-638655b88171aafa5f79912ce16e6a55-c.jpg
image_1.png
 
Aha! Finally getting scientific enough on this.
Now...let's get into high speed wobble...
:nutkick:
 
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