I respect your experience, and have no doubt that what you observed is correct.
However, nothing you have brought forward suggests that there is a bias towards a cart leaning or steering to one side or the other, and that is what the OP is suggesting.
That’s an extremely weak argument.
I had to type out all of that twice (I was also doing something else the first time and I timed out) and it got a bit mis-ordered the second time, but the key part is:
the point being that debris on the right side of the aisles either gets shoved underneath the shelf or up against the recessed area, which would be out of the way of the right-side wheels, while debris in the middle of the aisle is freely rolled over by the left side.
Additionally, checkstand conveyor belt units tend to be flush at the bottom, and are almost always arranged so the conveyor belt is the left side of the baskart, while the right side of the lane is a candy/merch rack with space underneath for trash to go under. At least that’s how they were arranged at the stores I worked at back in the day.
Well I have learned one thing from this thread, the pulling comes from the back wheel. Not that I given it much thought but the default movie conceit always shows the squeaky, wobbling front wheel so I just assumed that was causing the problem.
I came here to post the correct answer, but Loach beat me to it. Left in the Northern Hemisphere, right in the Southern Hemisphere, straight ahead at the equator. Coriolis effect, baby!
But wouldn’t that depend on whether you are going around a low-pressure or a high-pressure store?
I first thought this also. And of course it exacerbates the unequal wear.
I wonder if a cart on ideally swivelable casters on some sort of non-biased test surface eventually does not undergo chaotic flutter, and its motion dynamics under even pushing is unpredictable at some point.
Where’s a mechanical engineer when you need one?
Also, DCnDC, great input. Breadth of SD is such a pleasure.
Which way is the cart moving and to which side of the aisle is the cart on?
For every cart going one way and/or on one side so left wheels are in the center there will be another cart positioned the opposite so right wheels are in the center.
I seriously doubt any explanation in which most stores and/or most shoppers must travel in a consistent manner.
People go all different directions around store and up down aisles and positions within aisle etc.
The only thing you can say is that carts move forward not backward most of the time.
A couple of answers to this question.
This question seemed to be asked out of bias but since this question was posed I’ve been keeping track of the carts I’ve used during my Christmas shopping and without exception they have all pulled to the left. There is definitely something going on here.
That’s funny, because I got 2 that pull to the right yesterday and today.
Funny. If something gets stuck in the wheel, it will pull - left or right. But since I first posted this I’ve been keeping track. So far no right pullers for me.
The first one, apparently, is from the end of the 1930s (and we just missed an anniversary).
https://www.google.com/patents/US2196914?dq=2,196,914
FOLDING BASKET CARRIAGE FOR SELF-SERVICE STORES Filed March 14, 1938
The present invention relates to a novel rollable market basket carriage of a lightweight portable type expressly but not necessarily, adapted for convenient usage by shopping customers in grocery stores and similar establishments of the so-called self-service classification.
The chief object of the invention is to provide the trade with a novel lightweight easy to handle multiple rack equipped roller supported carriage, the preferred embodiment being characterized by a dependable structural assemblage which is rigid and reliable when erected for use, and compact and convenient when folded for storage in an out-of-the-way location in the establishment.
In its preferred embodiment the improved construction has to do with the adoption and use of a pair of complemental intersecting pivotally adjoined wheel supported leg frames, there being associated with the upper portions of said frame, an additional frame functioning as a rack and this having linkage connection with the associated parts to provide for the aforesaid rigidity when the device is in use, and to facilitate folding and unfolding with requisite certainty and expediency
Shelton’s “A Brief History of the Shopping Cart” has a few good pictures (despite its idiotic historical premise): http://www.eldo.us/wp-content/uploads/2010/10/Shopping-Cart.pdf
These two cites among others, including the founding tech’s legal history, taken from an excellent article on the technology and the business of groceries by Zachary Crockett, published at Priceonomics last month, “How a Basket on Wheels Revolutionized Grocery Shopping.” How a Basket on Wheels Revolutionized Grocery Shopping - Priceonomics
The most interesting thing of the article, and the kind of analysis for which the site is famed: ask a random person (me, eg) 1) what good are shopping carts, and, although most people don’t put it this way, 2) why would someone–engineers, the industry–have come up with them. I think everyone would say:
Answer 1 Is debatable, and is certainly wrong during the era (that just before the invention, unsurprisingly) when you got a clerk to box everything, and the business was switching for many reasons to “self-serve,” which meant that
Answer 2 is absolutely backwards. The design challenge was how to get people to buy less stuff.
Fascinating situation.
NB: Other SD thread left to RIP, but interesting: What causes the clicking of a grocery cart wheel? What causes the clicking of a grocery cart wheel? - Factual Questions - Straight Dope Message Board
I can’t help feeling that this problem could be best studied with the cart on a fast-moving conveyor belt.
I neglected to thank and cite
, which is why I chose this thread for the bump with the Priceonomics article.
Let’s consider a spherical shopping cart on a frictionless conveyor belt.
I have observed that the staff who collect those long lines of trolleys have a habit of standing on the right wheel by using their foot as a form of friction steering.
I do not recall seeing them stand on the left wheel, my guess is that most folk are right footed and they prefer to steer in a certain direction.
Maybe that has some effect on these trolleys
Thanks for posting the Priceonomics article. It’s interesting but you seem to have misread it and drawn a false conclusion.
The article says:
That’s carry less stuff, not buy less stuff. The point of the carriages was absolutely to get customers to buy more stuff. It still is today.
My WAG: If it’s true that shopping carts tend to pull to the left, I propose that it’s because shoppers turn shopping carts left more often than they turn right.
Whether there’s actually a bias or not, I’ll agree with dragging the things sideways contributing to the wear. And I think part of the problem is the rotten turning radius. When I find myself in a situation where I can’t turn the cart sharply enough to go the way I want to go, my solution is to skid the rear end around the way I want it. Undoubtedly, not good for it, but I’m going to do it anyway, so there. If somebody wants to think about the design, try to give them the ability to turn a bit tighter - maybe make the rear wheels swivel, too?
And they HAVE made a change which makes me use carts rather than a basket more often - Safeway has started adding these smaller, more maneuverable carts which I now usually use (they’re black instead of silver, BTW). I still wind up skidding them sideways sometimes, but they are better.
Fun fact: in the UK, shopping carts generally have four steerable wheels. I don’t know why the back wheels are always fixed on US carts.