I don’t know if this is technically a physics or an engineering question so I put it as physics but if it’s more in the engineering section feel free to let me know.
But I watched a movie called Dragged across concrete and there’s a bit where it’s demonstrated that a security vehicle can has solid rubber tyres. I thought a vehicle with solid rubber tyres would be too unweildy to operate. I’m not a physicist or mechanical engineer. Is that a fiction solid rubber tyres or are they actually used on day to day security vehicles on conventional roads?
In: Physics
Solid rubber tyres are common in construction vehicles, military vehicles and some “security” vehicles. They work fine on normal roads but are considerably more expensive than air filled ones. They are completely maintenance free and can’t be punctured which is why they get used in those cases.
Physics wise, they still deform under load so have good friction on roads but they work better on heavier vehicles because of the increased pressure to stick them to the road.
Solid tyres do work, they were for years the only type of tyres, and in a number of use cases they’re the better option. They’re tough, they don’t puncture, last forever and a day, all of which mean that in harsh environments, or situations where damage is a distinct possibility (e.g. when under attack), they have significant advantages.
However, as a converse to this, they’re heavy, they don’t adapt to surfaces so can give a harsh ride, they can’t go to particularly high speeds (accellerating a rotating mass gets a lot harder with increased weight).
Putting these features together, solid tyres are the better choice for construction vehicles, agricultural vehicles, and, in some cases, security vehicles. There are also vehicles that have a sort of hybrid – pneumatic (air-filled) outer layers, with a thick solid rubber core around the rim of the wheel to allow them to move at a reasonable speed if the pneumatic layer is punctured.
You are right that a solid rubber tyre is not not going to handle well. So they have a fairly low top speed. You would not drive it on the highway. But solid rubber tyres are used a lot for low speed situations. They handle more weight and are more durable. So security vehicles based on golf cart with solid rubber tyres are quite common in industrial areas where it is likely to get a flat. You can even get softer rubber compounds that handles even at medium speeds. So you could have a city car on solid rubber tyres to drive around on city streets, but still not highways.
Another style of rubber tyres are run on flat inserts. These sit inside a regular tyre and normally does not touch the outside rubber. But if you get a flat the tyre can not collapse and you now run on the rubber or plastic insert. Again handling is a lot worse so speeds are limited. This is intended to get you home or to a tyre shop without stopping, not to drive around day after day. So if you get a flat on the highway you can slow down and limp to a suitable highway exit.
But there is more research being done with rubber tyres. There is a concept of cutting holes in a solid rubber tyre so that the remaining rubber forms a dampening lattice. This have properties much closer to compressed air which gives the tyre similar properties to a normal tyre. The handling is good enough to drive highway speeds. Even though this is still under research there are lots of prototypes of these types of tyres. But there may be issues with cost, durability, longevity, etc. preventing them from being sold commercially. Or at least only for very limited use cases.
Latest Answers