Nov 16

Hi guys. After a bit of a hiatus I am back. We moved our shop to a new location which was a LOT more work than I anticipated. The move is now over with and I can hopefully dedicate more time to the TriBike.

I have done some exploratory sketches focusing on the TriBike. I figured that this part of the project is much more involved than the running cart, and so I am planning to focus on it for this round of concepts.

There goes:

I started off by exploring possible structures that would be stiff enough to support the load with a single span frame. This first sketch shows the preferred layout that we discussed in our last conversation. Because of the large span and high loads that the bike will be required to withstand the frame must have some triangulation to avoid too much frame flex.

tribike4sm

This is basically a variation of the theme. In this case there would be a space frame that would form the chassis of the bike, and then the seating and drive trains would be mounted to the chassis.

tribike5sm

This frame is a wishbone frame where the load of the front rider gets split between the 2 rear members. The recumbent bike behind are each mounted on an arm of the wishbone. This has the potential to be more rigid than the previous concepts.

tribike6sm

One big concern that I have with all of these concepts is the overall length that the bike will be and the fact that we will have to support a load over the entire length span of the bike. While it is definitely possible to build a bike that will work well, I worry about maneuverability, and ease of transport of such a long bike. This lead me to rethink the configuration to come up with ways to shorten or articulate the frame.

One way of doing this is actually to place the rear bike behind the 2 recumbents. This eliminates the length of the rear triangle and the need for clearance for the legs of the rider diamond frame bike.

With this in mind I started sketching:

tribike2sm

While this configuration would definitely reduce the length of the frame I felt that the bike could be further simplified by employing a standard diamond frame bicycle in the TriBike. This would bolt onto the back of a side by side recumbent at the front fork, eliminating the need for a customized diamond frame, and creating an articulated bike. This would greatly increase the maneuverability of the bike, and it would also reduce the cost of building it.

tribike3sm

realizing the benefits of an articulated frame for maneuverability and transport, I thought that this could be equally well accomplished, in the desired 1 fore 2 aft configuration. So my final sketch is of this concept. While this bike will be very long, since it articulates at the joint between the diamond frame and the recumbent tag along, it would be relatively maneuverable compared to a fixed frame. These separate frames could then be split apart for ease of transport. Furthermore the load span has been considerably reduced which means that frame flex will be less of a problem.

tribike7smLet’s plan to talk tomorrow to see what you guys think about this as a direction for the bike.

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