Seat Tube Free TT bike
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This bike is not based on a specific model but based on existing forms that could exist in practice.
The advantage of a fixed wheel model is simplicity removing the need for a gear mechanism.
The model is 1/14.26th scale of full size.
This is a functioning model that can be printed flat without any supports in one complete operation.
Meaning the parts are printed in the main horizontally and vertically with no overhangs and hence no supports.
What this means from the point of view of the cycle to be created is that there will be only one rear chain stay and only one front fork blade. On most bikes these elements exist in pairs but real world examples with single sides stays and forks do exist in mass production.
However, including the other side of the pair on each of these would require the use of supports or printing these separately and fixing together to complete the model.
Removing these from the model does not compromise the function and simplifies the process.
In addition the seat tube has been removed and the wheel rim profile increased.
The functioning model will have rotating wheels front and rear, movable steerer, chain ring, pedals and drive linkage from the chain ring to the rear wheel.
Rather than trying to create sprockets and a chain which although not impossible is impractical for a model of this size. A drive belt (elastic band), with be used and the rear drive and chain ring will be grooved.
Profiling will be applied to the elements to replicate aero functionality.
This involves having a rounded tubular form for the downtube, seat post and the wheels/spokes. Bladed profiles for front fork, chain & seat stay.
In this design the seat post is a continuation of the seat tube for simplicity.
A separate seat post would require a slot, holes or other attachment.
Once printed, separated and any smoothing applied, assembly is designed to be glue less and requiring only 7 screws to attach the loose elements and one elastic band.
Materials and methods
The holes in the wheel hubs may required a little widening with a 2mm drill to allow rotation if printing tolerances impact clearances.
Whilst the holes in the tri-bars, fork, front fork headset, pedals, chain-stay & crank-set require no adjustment.
Extra supplies required to complete the model.
Screws required are all M2 in 3 lengths
1: 8mm x 3qty, pedals & front wheel
2: 12mm x 3qty, rear wheel & steerer
3: 18mm x 1qty, crank set
Elastic band x 1qty, 20mm diameter, 1mm thickness.
Material : PLA
Size: 128mm x 107mm x 10.1mm
Layer Height: 0.15mm
Filament used: 28g - 9.41m
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