• 7th February 2005 - By greg

    Feb 7

    Feb 7, 2005

    The Sandwich Racer Concept

    1. 700 rear wheel, 650 front wheel, oversized chain ring (regular shown), standard cranks (not shown) and a carbon seat.

    2. The blue object is the left hand sandwich piece. This could be cut out of a stock, flat carbon sheet – or some other good weight/strength ratio material

    3. Here is the second carbon sandwich sheet. The axle of the rear wheel fits through two holes in the sandwich sheets and a standard quick release holds the wheel in place. The holes could be drilled slightly oversized to allow alignment of the real wheel. Since the width of the front drive wheel is wider at the hub with gear cassette, a large hole needs to be cut out of right hand sandwich. The left hand sandwich also shows this hole, but since there is no gear cluster on the left side, I don’t think that large hole is necessary.

    4. Fairing support ribs are bonded or fastened to each sandwich sheet. They could be made of the same material as the sandwich sheets. I’m not sure these support ribs are even necessary.

    5. This shows the bolt-on steering mechanism. In it’s simplest form, it could be a standard head tube that supports the right hand side of the axle. A push/pull action on the left hand side of the axle causes the wheel to turn. The turn radius is limited by the 650 wheel touching the sides of the sandwich sheet (about as much turn radius as the Varna currently has).

    The chain is held in place by the derailleur (hopefully).

    My first concern with this system is the chain staying on the gears. Since the turn radius is so small, I wouldn’t think there would be an issue with the chain bending, but that chain is quite short and it may not want to bend that much. A test will confirm that. If it is a problem, then I may have to add an intermediate drive directly above the gear cassette and a second chain that is in-line with steering axis. This is the ‘standard’ approach. Like this

    My second concern is if the pull of the chain when peddling will cause the wheel to turn to the right. Since the pivot is so close to the chain, this may not be and issue, or, it may be a small issue that could be solved with an elastomer on the left hand steering side.

    Third concern is forward motion causing the wheel to want to turn left. Again, this could be resolved with an elastomer on the left hand side. This speedbike has a pivot to the right of the front wheel, and it seems to be ok for 50 mph or above!

    6. Showing the pilot in place. The two sandwich boards should be easily pulled apart and put back together to facilitate repairs or tire changes. They could be held apart by standoffs (aluminum or carbon collars), or one of the sandwich boards could have an edge molded to it.

    Another benefit of this sandwich approach, is it provides sealed wheel wells for both wheels – if each wheel also has a disc covering the spokes, the wheel will turn with less drag inside the sheltered compartment. Also road debris will be kept from entering the inside of the fairing.

    Actually, thinking about it now, I realize that the wheel well areas at the bottom need to be faired – they can’t simply be cut out of sheet material. Or, they could be molded and faired and then bonded to the sheet material… Or the entire sheet could be molded to include a tighter fit for each wheel and elliminate the need for collars…

    7. The fairing half shells would each fasten to the sandwich sheets. One sandwich sheet might have an edge to it, and that edge becomes the missing strip of the fairing, or, the fairing halves fit together over the sandwich sheets. The fairing half shells could be bolted directly to the sandwich sheets – not sure how to do this without the fasteners showing, but it should be very quick and easy to put on or take apart.

    Since the sandwich frame itself acts as support ribs for the fairing, the fairing could be VERY, very light. Possibly just a layer or two of carbon without any sandwich material. Or perhaps a layer of kevlar on the inside to protect the rider from carbon shards after a crash. If the vehicle tips over, then I would hope that the support ribs would stop the fairing shell from becoming crushed.

    If the ribs and sandwich frame support enough of the fairing, then perhaps the fairing could be vacuum formed from plastic – maybe Lexan, or even better the fairing bubble material that Varnas use (polycarbonate?) – same as large pop bottles. Then maybe the fairing shells could be disposable??

    Sandwich Racer to do list

    1. Everything!

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