Heres an idea ive already tried on a scooterteq electric bike, and it worked fine once i got used to it, problem is that it produced a lot of drag, and that combined with cold temperature, made it impossible to get more than 15Km of range on a charge. Another problem would be the use of brakes if used on the rear tire of a motored bike, but with coaster brakes, this would be an ideal way to get traction in snow.
1. start with a length of chain (ten feet would be more that enough) that is small but strong.
2. Wrap the chain around the tire and rim and cut the chain so that the to ends of the chain meet but do not overlap at the rim. (an example would be like putting on a wrist watch with your wrist being the tire and rim.) You now have the length that you need for all your pieces of chain.
3. How many lengths of chain that you will need depends on how spaced out you want your chains to be on your tire. You dont need many and its not too important that they are evenly spaced on your tire tread, but what is important is that all your lengths of chain are exactly the same length, or the number of links are the same. Cut as many lengths as you need to go around your tire. (Less is better, less drag, less work)
4. Remove your rear wheel and take a few psi out of the tire, but not all of it. This will help you get the tension you need to keep the chain from sliding on the tire once you have reinflated the tire.
5. Use removable chain links (or whatever would work best) to join the links when wrapped around the wheel and tire. Do this all the way around the wheel than reinflate the tire. Make sure all the chain lengths are snug with equal tension all the way around the tire to ensure the chains do not slide on the tire.
Another way to join the chain links at the rims is to use old brake or derailler cables (without the casings) clamped together with whatever is available.
6. Put the wheel back on and challenge the snow.
If your riding on paved roads for a good length of time, be sure to check for exessive wear on the links, it never happened to me, but I would hate to see where the chain would end up if it flew off the tire.
Im sure there are tire chains are available for bikes, but I dont know of any and im sure their pricey. Besides it only costed me around ten bucks, and a couple of hours to concieve this idea. Hopefully someone might try this and let me know how it works on a 26" tire so that snow does not conflict with our need for speed.