Alternate Trike ideas

I thought of a possible alternate "trike" that would really be a kind of diamond-quad, with the trailer-wheels/hubs using 26" tires on the rear sides, at the same spacing as the WC ones in the pics I have in prior posts, but with a bike's rear wheel and mountings just behind that, as the actual driving wheel. This way there'd be no worrying about how to hook up the drivetrain to the wheels.

It'd be about 10-15 pounds heavier, though, and it would be even harder to turn, because I'd have three rear wheels all in a single plane that would need to stay in ground contact. A side-wheel suspension that allowed pivoting around the center wheel during turns could cause problems with rocking back and forth on anything but perfectly smooth pavement (which is fairly rare). If I coupled that with the steering so that it only tilted during turns it'd be ok, but it would be more complex and even heavier.


Now that I have those shocks and springs, I am tempted to build the tadpole trike instead. A potentially serious disadvantage of the tadpole is that the cargo section in the rear would have to be split into two halves, on either side of the wheel, just as it is now on every other bike I have.

This can be solved by either putting the cargo section up front between the front wheels, which limits how high I can stack things due to visibility concerns, or to add length to the bike and place the cargo section between the back of the seat and the rear wheel.

It should be possible to do the latter in such a way as to be extensible, so I can keep the bike short when not carrying cargo, but that would require a foldable or soft-sided cargo "pod". I'd rather have one that is fully lockable so it's more secure, so I think that I am much more likely to leave it as a solid longer trike (longer by as much as 2 feet!), with even more cargo space on either side of the rear wheel as the pannier-style cargo boxes I have now.


If I do the tadpole, several problems go away:
--trailer rear wheels can be used for the front wheels as they are, no changes
--WC wheels can be used on the trailer, no changes
--drivetrain connection to rear wheel can be exactly like a normal bike, or like my current CrazyBike2
--Front of bike gets shorter, so easier for me to see around corners before I get there

The front end and steering gets more complicated, but it would also have better suspension *and* I think I could even do the rear suspension I want (still using springs rather than airshocks, though).

I can use either regular steering or under-seat steering (USS). The regular steering is as pictured above, and the USS is below:


The versions sketched above (in MSPaint) are 20" front and 24" rear (might not really be proportional). Medium blue is the main frame, black is the front double-A-frame suspension and the tires. Dark blue is steering. Gold is the rear triangle. Orange with black lines is the shocks. Teal is the seat. Light green is the motor. Red is chainlines, purple the pedals/cranks, pink the bottom brackets and chainrings. Gray is the cargo box (only pictured on the long version, but present on the other as well as just the split-box rear half, without the full-width box just behind the seat).

I'll need to work up a parts list for the tadpole version and see how many things I don't have already, to see if I can build it faster than I could come up with solutions to the other problems involved in the wheelchair trike's drivetrain and such.