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Australian and UK shopping trolleys steer with all 4 wheels. Absent the fulcrum of non-steering rear wheels, to get a fully laden Aussie trolley to go around corners, one must either swing the back end of the trolley widely around corners to oppose centrifugal force, or use one's legs and upper body
to grunt the trolley sideways. This motion places an unacceptable amount of torque force on the knees.
Paths which slope sideways are especially treacherous with 4-caster trolleys as they will happily roll in the direction of the slope. One must drag the trolley against the force of gravity or push against it from the side.
A simple clamp made from a piece of square tubular steel welded to a pair of vise-grip type or "C" clamps could be used to fix the rear wheels in parallel position so they do not steer.
This aid would be of great assistance to shoppers who have had knee injuries or surgeries.
The plastic 'Markitcart'
http://www.markitcart.com/
your competition [weezil] [ConsulFlaminicus, Jan 17 2005]
[link]
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Interesting. Around here the only carriages with 4 pivoting wheels are the ones designed for people who have trouble walking. They clamp to the front of wheelchairs and other such transportation. Why are there 4 castors on all of them? |
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Shz, that's an excellent question. |
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I've only lived in Australia since 1996. Far as I know from asking lifelong Aussies, the trolleys always have been like that. |
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Aussie grocery stores are much smaller than their US counterparts- or at least the older ones (pre 1980s) are. Perhaps there was a need to be able to move trolleys sideways easily to suit the floorplans. |
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I like being able to spin the trolley around, it's fun shopping with a trolley with 4 castors. Anyone having trouble with it is not playing enough to learn how to push the trolley along a slope (point it up hill and slightly in the direction you want to go, then 'ferry glide' (a kayaking term.)) Going around corners is like playing asteroids, apply thrust penpendicularly to the tangent drawn on the desired path (does that make sense?) don't struggle at the back of the trolley trying to apply a moment. |
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Given that my favorite part of shopping is shooting down the aisles on the back of a speeding trolley, I would love to be able to spin it as well. Could you ship a couple over, and I'll send you some fixed rear wheel American trolleys by return mail? |
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I welded up a copy of this device yesterday arvo. Took it over to the local Woolies and showed the manager. He wants 5 copies by 5 January. |
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Showed a couple of shoppers a 2WS trolley and let them push it. People walked away wondering why Aussie trolleys steer with all four! |
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Wonder where the negative votes on this idea are coming from & why. It's much more popular in steel than as an idea. |
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One of them's mine, 'cause like I say pushing a trolley with all for wheels free to rotate is fun! |
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Good luck to you though, go into production and make a killing, there's a lot more millionaires out there from producing widgets than from sports, TV, or music. |
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I too wondered why some trolleys
have 2 fixed castors and some
don't. I'm sure I've seen both
though, either in NZ or
Australia. |
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At first I thought this idea
would fix the front wheels, to
give rear wheel steering. That
would reduce the force necessary
to turn. The front wheel
steering trolleys require quite
a bit of torque to turn (and
unlike the free castor versions,
you can't avoid it by fancy
asteroids-style maneuvering). |
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I like the idea of having
removable clamps. |
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I just thought of one commercial
disadvantage of the partly-fixed
trolleys: The long chains of
accumulated trolleys in the
parking area couldn't be steered
by staff. [edit] I guess they
can. |
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Trolley attendants in the USA manage to push long (10-12 metre) nested chains of fixed-parallel rear wheel trolleys just as they do here in Australia. |
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There's enough slop in the fit of how the trolleys nest together to permit a trolley train to turn like a caterpillar. |
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It's easier for the average person to manoeuvre a trolley with 4 wheel steering. Apply torque to rotate, pull sideways to go sideways, push forwards to go forwards. Physically it is more difficult, but mentally it is simpler. |
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For example, if you want to move out of somebody's way, you can just pull a four-wheel trolley sideways. With 2ws, you need to move either forwards or backwards. |
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That said, on sloped ground, 2ws has definite advantages. How many grocery stores near you are built sloping? |
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Notably, the UK uses both - 4 wheel steering for grocery stores, and 2 wheel steering in hardware stores. |
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In the US, at least the bits of it I've lived in, the hardware stores usually have four wheeld steering. They aren't the same kind of carts though, they are much heavier, with a flat bottom and no basket. Now that I think of it, I rarely see people using carts of any sort in the hardware store. |
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How about constructing a trolley with six wheels: two swivel casters in the front, two fixed wheels in the back, and a couple of swivel casters in the back which can be pushed downward via lever (to take weight off the fixed wheels)? This would allow for the advantages of an all-freewheeling trolley when needed (e.g. when the trolley had to be shoved sideways) but otherwise keep the advantage of the fixed-rear one. |
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You're asking shoppers to think, and to use controls? |
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David wrote: "That said, on sloped ground, 2ws has definite advantages. How many grocery stores near you are built sloping? " |
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In Sydney, I can think of very few malls which are on a level site. Real estate is extraordinarily expensive here, mandating small building footprints, thus many malls are multilevel with ramps connecting the levels. |
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These site issues are the whole genesis of the idea. |
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20 units now sold. They take about 15 minutes each to make, including cutting the steel and 2 MIG welds. |
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If customers like it, who are we to argue? |
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Like a truck's steering wheel? I think I'd prefer a pair of vertical handles, but I don't have much of an issue with the current setup. |
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I forget where, but I have used a brilliantly designed five-wheeled trolley. There was one fixed wheel mounted centrally under the trolley and four castor wheels at the corners. The trolley would corner well, unlike the four-castor designs, but was also highly maneouverable due to it's ability to spin around it's central fixed wheel. |
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[weesil] - Top marks for not only making this, but selling it as well. Might I suggest that you look into some upmarket baby buggies that have castors on the back that can be locked in the six o'clock position with the tap of a toe. If you could build this mechanism you could retrofit all the trolleys, allowing all shoppers to fix the rear wheels if they want to. |
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Having used both US and UK trolleys, I do find the fixed-rear-wheel US trolleys easier to manouver. On the other hand the trolleys with 4 pivoting wheels do allow the trolley to be spun within its own length by applying a sharp sideways force to the handle. Children sitting in the trolley's childseat love this.
Perhaps supermarkets should offer a choice - fixed-rear-wheel trolleys for serious shoppers, and pivoting-wheel trolleys for those with children who need entertaining, those who hark back to their Asteroid-playing youth, those practising for a production of "Woolworths on Ice" and those who just like showing off? |
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[weezil] You go , girl! Please also start design work on a trolley designed to discourage the carriage of children. Something with spikes similar to those anti-pigeon devices would be a good start. |
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"Girl" alliterates with "go". "Boy" doesn't. No, I don't know how he reached that conclusion either. |
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Somebody who has balance problems when walking would appreciate the fixed rear wheels.
I have some personal experience after having an accident and normally using the shopping trolley to steady my walking while I did my shopping. |
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Why not make the rear wheels convertible to both options so customers could choose their preference? |
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