|
I don't think keeping constant force between the tyres will be difficult or complicated. The 5:th wheel must off course be spring loaded to follow the car's tyre, but the movement will be much smaller than if the 5:th wheel has to follow the ground.
Mounting the 5:th wheel in FRONT of the car's own rear wheel like Frank Lee suggested is probably good, but such a location is almost impossible on most passenger cars without some serious body modifications (and sacrificing some of the rear seat). Placing the 5:th wheel BEHIND the rear wheel may be possible without any modifications that may upset the authorities/MOT/car approval. The extra engine/motor can be located in the trunk as cargo or on the hitch-ball. Drilling a hole or two for suspension and drive-shaft in the fender will probably not upset any approvals.
If built in a clever way, the 5:th wheel will be difficult to discover along the road and if the entire hybrid system is installed as cargo (hooks and straps instead of bolts and no need for tools) there's not much to say about it for either the police or MOT/yearly test and approval.
For accelerating a car from stand-still through the friction drive will take a LOT of traction in the start, but as the speed goes up the torque will decrease to transfer the same amount of power. -Just like any car powerful enough to spin the tyres in first gear, it will probably not spin in higher gears. If powerful acceleration is needed, the car's own engine is used, not the auxiliary drive.
To minimize friction losses and tyre wear the 5:th wheel can have a variable spring tension, by an electric motor or air bellow. If the swing arm is designed carefully it may even control the tyre-tyre force by transferred torque.
If I get some spare time I will definitely try this 5:th wheel idea out in my 40 year old scrappy Saab. To keep things as simple as possible, the first test will have a fixed gear ratio for highway cruise, where the need to transfer torque is relatively low. I will either try my little 12hp diesel (quite heavy thing) and go for maximum efficiency, or put the friction drive to a more demanding test by the 30hp Yamaha two-stroke snomobile engine with CVT.
|