Out of curiosity, I built a Lego model of a three wheel cluster of one of these dollies and tried it on different sized steps to figure out what relative wheel cluster size works best
why you (metric users) must always point out such shows you pet your ego , as a slight, at others you consider non-conformist,.. I use the standard system and do perfectly fine with it, use it if it pleases you, that's what I do, ...just not metric,
I've always been fascinated by these. I've seen ones with clusters of 5 wheels as well. There is this big vehicle called the Landmaster that was made for a sci-fi film in the 1970s which has front and rear axles with wheels in this configuration.
I modeled this in CAD, and the interesting thing to me is how big the trade-offs are between wheel size and arm length, especially when you consider nosing on the treads. And then there is the problem of the load on the axle clearing the nose of the stair, at a reasonable angle. It's like it needs to be optimized for different stair styles.
@@matthiasrandomstuff2221 my house is rather old. As a result, walking on modern (consistent tread height etc) stairs feels strange. No idea how you all manage it so easily
What if you whould have gears instead of wheels and a (rubber?) chain going around them and then playing around with chain tension? There are these interlockable belt chains you could mount in exchange for a v-belt. Maybe these are suitable for that?
These dollies are good for pulling a load up a straight flight of stairs (no "spiral"/helical stairs). In most other cases they often fail in practice: - Going downstairs, the wheel cluster tends to not move as intended and shown in the video. The wheel that was contacting the top step before will often roll down the riser instead of the cluster rotating about the wheel resting on the bottom step. - Going up (or down) "spiral" stairs, the clusters on the left and right side do not stay in sync, so the whole dolly including the load tends to tip to one side. - Going on a flat surface, the dolly does not corner worth a damn, because it is like a car with all wheels locked straight. You have to drag at least two of the wheels sideways for cornering. I have one of those dollies and am seriously thinking about throwing away the clusters and just replacing them with regular wheels.
Sounds like those problems could be fixed by making a separate axel for both wheel-groups and adding a brake so that you can apply brake when going downstairs so the wheel group would spin instead of wheels
I find the motion of stair climbing sack barrows fascinating, but I have been frustrated that no-one will slow down the motion and make it possible for me to analyse it. This video was perfect for me. Thank you.
Thank you for showing the movement pattern of the 3-wheel dolly. I have a ROLSER Cart with three wheels on each side. With a heavy load, it helps that ascending and descending on stairs. I call it my $60+ well spent. God bless!
Throw in a motor and a sensor to make it lift itself up stairs when it's loaded with "heavy" things. Incorporate that into the the dollies for old people and you'e solved a huge problem :) No more heavy lifting for old people. The ones that they have now still require them to lift the bag up the stairs, 6 wheels or not. The bag is heavy and needs to be lifted up... Not if it had a motor doing that work. That's just my idea, but i have no money so i can't make my "inventions", so i've just decided to drop them around and hope someone picks them up and makes a shit ton of money. Only requirement to make a shit ton of money, is to have money in the first place. Good luck, i've given up.
An important feature would be for it to rest on a step without rolling all the way back down the stairs. Some of the bumps in the line may be necessary for this.
Peter Rhodes Depending on where the center of mass is placed. Maybe just a simple lock, like one of a kids bike may have? Where going backwards holds it in place.
@@AgameWeAllPlay That's called a coaster brake. It relies on a mechanism inside the hub. I don't know if they can be designed to be switched on and off, though. However a mechanism that _does_ work in both directions is ratcheting pawls, which someone else mentioned are actually used on some of these dollies. Personally I was wondering how you could adapt a bicycle brake, or indeed any brake at all, to a wheel like the ones on single-wheel dollies (at least with off the shelf components that I know of), and I can't really think of anything. Maybe if the wheels could be fixed to axles, one brake handle could be used on two brakes on the axles? That would probably be hell to set up, though. Fun to think about, anyway.
oh! unless there was just a cable from one brake to the other and that's what gets pulled on, so the mechanism could equalize itself! I guess you'd want a pulley to get pulled on by the handle's cable. 😂 I wonder if that would prevent friction from ruining the equalization when the brakes are off.
It's a nice theoretical exercise but your assumption that a smooth, continuous slope is the optimum does not take into account that the human body is designed around intermittent jerky motions, powered by muscles with only a finite range of contraction. Unless you had a very light load, in which case one has to question the need for a dolly, the ability to rest midway seems advantageous?
Instead of trying to find the perfect wheel geometry, I would tackle the jerky behaviour via a spring /oil damper on the handle pulling the trolley. This will smoothen the whole pulling experience for the person pulling the trolley.
As a Dane (born in Denmark) I can't help feeling a little proud every time I see LEGO used as a "science tool" (The toy for all ages, genders and knowledge levels)
I almost pulled the trigger on a $500 aluminum cart with these wheels, but I tried to find a review on it first and I did. What I found is that it is the nosing that is the problem. People were complaining on it wrecking their wood stairs. What I think needs to happen is to have less space between the wheels so it does not hit the nosing on the metal part between the wheels. Possibly bigger wheels would fix this. Or possibly are wheel in the middle on the axle that extends past the frame part.
Excellent! I was looking for how these things actually work/look while climbing. I wanted to compare the tri-wheel design to some that seem to be advertised as stair climbing but just have big normal wheels, and that option's existence actually makes a bit more sense after this even though you didn't show it.
In middle school I had to read for 30 mins. I usually picked popular mechanics or rc mag etc. A vehicle with cluster wheels ment to explore mars or something was in one of the magazines. I can't find it. But I think it would be a hell better.
I have one of the stair climbing dollies in my spare room, left over from a business I used to own. It has been a life saver when moving large awkward objects like washing machines, fridges etc. Will never part with it. Love your analysis of it, thanks.
Aha, this confirmed my suspicion that appliance hand trucks with tracks for climbing stairs allow for a higher load (360 vs ~200kg). Thanks for illustrating. Because they allow the load to be pulled up at a constant incline instead of an oscillating incline, with a higher peak incline, you get with the triple wheels. Want to get a tracked one then, unless there're other advantages to triple wheels?
You actually made physics enjoyable to watch! That's a feat in and if itself! Lol Now it's time for me to go build a couple sets for a dolly lift. Thanks!
With those dollies, you want enough wheel base, so the unloaded wheel can "land" on the next tread (up or down), and both wheels can "rest", on a single tread at the same time. I realize that won't happen all of the time, but it should happen most of the time, with properly built stairs.
I remember when I was a small kid going to ball games and seeing those people carrying huge crates filled with ice and beer or food or whatever to sell on the bleachers. And they would lean the crate against the rail and slide it down or push it up along the walkways. Ever since I've always thought that a 3 wheeled dolly would dramatically decrease the amount of force needed to haul said crate. If you could come up with a way to make an adjustable dolly (to accommodate for every venue and their different layout) that's lightweight (I'm thinking Al) and a battery that somehow helps push the dolly up, that would be a very easy sell for any stadium, you could even prop it with speakers or LED screens to promote prices or something like that. Anyway, it wouldn't be made out of wood, but perhaps you could work out the physics of it and sell the plans or partner with someone who would build the actual demo-able model. Have fun with that man! I love watching your videos. Please keep it up.
Since I’m a day into this, I realize it will probably not get read, but I’m surprised nobody brought up Dean Kamen’s ibot. It used 2 motorized wheels (about 1ft or 30 cm in diameter if I remember correctly) pivoting around an axle to help a wheelchair climb stairs. And yes the tech from this was eventually what lead to the Segway. I saw a demonstration of it in 1999, was awesome and unheard of technology back then, and still a cool idea even now.
Propably the best way to engineer this would be to figure out what size of wheel and arm is best for what step-size. Maybe by figuring out some mathematical function that takes the size of the step and outputs the best size of wheel, and/or arm.
Armed with this formula, it should be easy to build grocery carts superior to the junk being sold to people who would depend on them. They would only be required to carry a load in one direction, so don't need to be overbuilt. Unfortunately, that's why they are always underbuilt, and end up collapsing between market and home, according to Amazon reviews.
I like how some of the forward force pushes it up. Or all of it I guess until a smaller wheel has to climb a up. Both directions of force help move it.
I think that using wheels of this diameter can electric carts because manual prevents stopping between the two steps because the width of the step of the stairs is 28 cm and therefore the best measurement of the diameter of the wheel is 12.5 mm where 12.5 plus 12.5 equals 25
If a "perfect" slope is available and considering that the wheels on a typical dolly would be of fixed size, could you in theory design a mechanism where you enter the stair rise and the dolly adjusts the distance of each wheel axis from the dolly axis to compensate... would be an interesting project.
I wonder if you could change the length of the arms to optimize for the size step if it would be worth it. Another idea would be an additional single large wheel (or skid) in the center that overlaps the smaller ones to reduce the height difference between the peaks and valleys in the 3 wheel configuration.
Or you could design it so that it's facing one way and you go up and the other way when it goes down (so it always turns the same way). But having a ratchet that you can turn on and off is probably more versatile, if you want to be able to stop half in the middle of the flight.
you might also find that they're designed for workplaces that have a more defined "stair height" standard (and or the grip at the top). An older house is less likely to meet the standard dimensions you would find one a newly built workplace.
actually, it is very likely to meet standard stair dimensions. If a stair is farr off standard, you *really* notice, so unless you notice a stair being off, it's fairly standard.
There's a lot of other factors unaccounted for. Carpet adds some amount of extra headache, and I can't imagine this would handle corners both on the ground and mid-climb very well. Plus in some areas you have construction still standing that was put up before modern stair height standards. I think the ideal way to move heavy but nonfragile things up a wide variety of stairs might be with some sort of moderately-flexible, low-friction skate that can lash to what's being moved. I've read about old fashioned movers using moving blankets to speed things around without having to fuss with dollies, so that might be a path to it.
To add: It probably works great when the factors in a job can be accounted for though - like it's probably a godsend to the lower backs of people who make regular, large, commercial deliveries to business locations that lack elevators!
After hearing the opening section, I almost thought you were going to design a strange gear-like wheel that rolls smoothly in a straight line on a staircase. :D
The times I have encountered them I didn't really get them to work as intended. They just work way to slowly, because you have to take each step individually and they can't handle normal small humps like a threshold or small kerb at speed. You also can't adjust them, so the chances of them being ideal for the stairs you will encounter is pretty small.I prefer the standard ones with two big inflatable wheels, even with heavy objects going step by step.
You want that horizontal gap, it gives you resting points, if the wheels were enough to give you linear motion it would have no advantage. Being able to stop on any step with a heavy load is important.
REMEMBER People that the three-wheel design came from “Dean Jeffries” as seen in the movie “Damnation Alley” 1977 Starring Jan-Michael Vincent. The Tri-wheel vehicle is called: “Landmaster”.
That was great. I just moved house and the movers were using a plain two wheeled dolly to lift the washing machine down the stairs. It looked like a real pain in the ass. I'd hope that this or something similar would work well going downwards without being a hazard.
theirs some straps that go over your shoulders with a single wide strap between 2 people and that makes things like washers go up and down stair so much easier.
@@g6qwerty Sounds a lot easier than banging your legs on whatever you're carrying while trying to coordinate with the other guy. (manual carry) I imagine you'd use that in a longer distance situation though. It was only about 20 steps for me so I don't know if that would have been worth the setup time.
Your scaling of the size of the step versus the assumption that this is the same as size of the assembly is not correct. The lip on your tread does not adjust.
Have you experimented with the smaller wheel diameters? I’d like to develop a thin profile for strap on dollies for tight spaced applications. Landings for dollies are tight and a standard tri wheel configuration does not work.
Could you add a section where you show the axle path of a traditional single axle hand truck? Why are these triples easier and how much easier are they? Hmmmmm....
Very interesting... Just so happen to be building a trolley to take the De Walt T-Stack boxes as the one that you can buy for it doesn't suit, having a three wheel stair climbing will add so much ease of use, glad I came across your video today... coincidence? hmmm
For general use a single axel is better, 3 axel types are difficult to turn. I also recommend pneumatic wheels as they they provide some shock absorbtion.
What would happen if you replaced every wheel of your 3 wheel dolly with three smaller wheels each (so 9 wheels in total)? Mathematically this would start to resemble a Fourier decomposition but I have no idea what the practical effect would be...
@@matthiasrandomstuff2221 3 wheels instead of every single wheel, 9 wheels in total. 3 triplets of wheels, not 9 wheels acting as one large wheel (nine...agon?)
It seems that dollies of this type should be optimised for each set of steps? The path of the axle of a single larger wheel would be an interesting comparison. (I don't think Lego make one tho'). Good fun learning. :o)
@@matthiasrandomstuff2221 I was thinking more along the lines of the typical Pneumatic tyre found on dollies of this size, compared to the three (or more) wheeled version you showed. The "trajectory" of the axle would be far less straight, I guess.
4 wheels: Your cart will be stuck at the first stair,step with an overhang (as shown on this Video) because in a square the upper front wheel will directly touch the 'stair-wall'. 5 or more wheels: It will have the same effect as on one big wheel.
This arrangement works great when going up stairs, but they are not very maneuverable on the flat...with 4 wheels on the ground. they really only like to go straight......kinda kills for me.
Idk if that is possible but you could use the same system of an injection. Fill it with air inside and when the wheel touches the ground, gravity will make the other stay higher. Its useless tho.
allluckyseven yes: if you add more wheels the overall effect is closer to a single wheel and with two wheels the arm connecting the wheels will hit the stairs
Forgetting for a moment what you would do when you reached the top, but... What about square wheels of similar size to the rise and run of the stars..?
I dont know why youtube suggested this to me, but this is fascinating. Do you think it would work if the dolly was pushed up instead of pulled up? I want to put those wheels on a cart of sorts
This reminds me of those videos of bicycles with odd-shaped wheels (squares, etc) rolling over odd-shaped terrain such that the axles move in a straight line. So what would you need to do to get your axle to move in a straight line up the stairs?
it would have to be three threads high to do a decent job, at which point it's too big to be practical (cause the load would have to be too high to clear it)
