In a world where snowfall is "reliably common", how would an injured person with an immobile leg get around?

Question

There are a few techniques for people with injuries to get around in the real world; wheelchairs, crutches, and several other wheeled mobility devices come to mind.

Generally, if someone is dealing with a broken leg in winter, they would stay indoors, let a caretaker tend to them, and not travel on their own. However, I imagine the situation would change if the injury was relatively long-term (not healed after 4 weeks), and shoveling the roads to make flat paths every day was not a realistic option.

While snow is mostly considered an obstacle, if it's often relatively fresh and smooth - of the kind used for skiing/sledding, I imagine the option of relying on that smoothness to get around would become more likely, letting someone recovering from an injury retain some self-reliance. However, from what I've quickly researched no such device has been invented in real life - perhaps because even snowy communities tend to have snow cleared.

The thought that comes to mind would be something like a "sled-chair" someone could use to traverse a space the size of a spread-out village. Someone might carry a set of convertible crutches that can be used indoors, but also used as skiing poles to push their chair around. However, I'm trying to consider how practical it is if this person would have to handle the entire device's weight when approaching small inclines, with difficulty setting up any kind of effective braking system.

I'm specifically looking for ideas on what are the closest real-life inventions in the real world, as well as what are some unexpected concerns that would arise from use of such an invention.

Answer 1

In essence, this is a matter of ground pressure. Since a human on snow shoes exerts a ground pressure of 3.5 kPa or 0.5 psi, it would be necessary to reduce the subject's ground pressure to this level.

A combination of a snowshoe for the good leg's foot and a snowshoe attached to each of a pair of crutches should work.

Have a look at this commercial product for an idea of a modern attempt at solving this problem:

While I am doubtful that these devices would work in very soft snow or deep, soft mud, if they were made a little larger, I expect they would work very well on any soft surface.

I expect that as the size of the pads increases, the liklihood of tripping over them also increases.

Also consider the adaptations necessary for para-alpine skiing, where the usual ski poles are substituted with poles with skis at their tips:

Answer 2

Introducing the "kicksled," which is a chair on a sled. I used it in Norway to go to school. It is commonly used by older people. You stand behind the chair and push it along with foot power. It isn't that heavy which allows you to go up hills. Breaking can be done by putting a foot down or turning the handles to cause the runners to dig into the snow and ice. Because it gives a much wider ground contact, I expect that a person with one leg could lean on the handles and use it to get around. The biggest problem comes in spring time when much of the snow and ice is melting and there are big patches of mud / bare ground.

Answer 3

The larger the surface area is the less it digs in and, to a point, the lower the total friction. You do get to a point of diminishing return where a larger vehicle footprint starts to slow you down again but there is a sweet spot you can exploit for very low effort mobility over the snow.

The issue I see is that the sweet spot is weight and surface packing dependent, this causes two major issues that I can see:

• The design optimum footprint can be quite different for people of similar sizes if their weights are quite different, this will mean that mobility sleds have to be largely, if not completely, custom built, bespoke goods are often disproportionately expensive. It also hurts the ability for reuse which raises the price further.

• Quite minor differences in snow quality will make major differences to the actual (as opposed to design optimum) efficiency of the sled. Someone who can get around on a day with perfect, fresh but packed snow might be home bound without warning the next day when the lower humidity makes for a fresh layer of fine powder snow.

I also foresee potential design problems around passenger comfort vis-a-vis comfortable lengths and widths versus surface area and stability requirements etc... but I don't think any of those are insurmountable.

I think something in a paddle/shovel could work quite well for self-propelled mobility sleds, these could well be part of a reconfigurable crutch. For those who can't move themselves a pusher bar is already standard on racing sleds, where it doubles as a hand hold once your dogs are up to speed, a carer in snowshoes shouldn't have too much trouble moving a charge's sled over short-medium walking distances.