| 摘要 |
A power driven ski-bob with an elongated propulsion unit having preferably an anterior sliding portion, a posterior endless tread portion and an upwardly extending post means; the propulsion unit is connected to the rest of the ski-bob's structure through a pivoting connection which is substantially higher than the sliding and tread portions so that the pressure between these portions and the snow is decreased and increased respectively, in response to said tread generating thrust against the snow to secure the engagement between the tread and snow. |
