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Can regular bike forks be modified to allow front drivetrain setup?

Some bikes have front drivetrains instead rear drivetrains. The problem is that bike stores don't seem to carry forks that have a derailleur hanger. Forks don't always outlast the bike and custom building another fork is likely very expensive unless it's mass produced.

It's possible that you want or need a different style of fork. One might prefer metal instead of carbon fiber for safety and a larger room for errors, one might need a different style for panniers and fenders for touring and commuting purposes, one might need a different shape for fork lights or cameras, one might prefer mounting holes for a disc brake caliper, you nane it.

Here are some bikes that have a front drivetrain:

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Can you widen a steel fork from 100mm to 130mm to accommodate 8 through 10 speed hubs using the cold set method? 30mm of widening sounds quite large. It's almost three sizes up. I've heard of 10mm. What are the risks? Once you widen it, how do you install the derailleur? Can you tap a custom shaped steel bar and use it as a derailleur hanger?

You can find standard spacings for hubs and seatstays here: https://www.sheldonbrown.com/frame-spacing.html

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    Note that these bikes are either recumbent bikes and/or have hand-driven front wheels. Which of these is your goal? – anderas Aug 28 '18 at 7:46
  • I would make one using carbon fibre (foam core, wrap fibers around core, wet with epoxy resin, wrap with heat-shrink foil, shrink). I think a fork could be a decent first carbon-fibre-composite-project. – Nobody Aug 28 '18 at 11:46
  • The Twicycle is my dream bike. – Brian Aug 28 '18 at 14:55
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To cold set a regular fork by 30+ mm would no doubt weaken it far too much to use. The better starting point would be something like a 135 mm fat bike fork, common sizes are also listed in the Sheldon brown table you linked.

Notice however, that three of the four pictures you found feature extensive modifications to strengthen the fork or supporting frame to handle the pedalling forces. None of them will have off the shelf forks, they will all be custom made, along with the whole frame; they have totally different riding positions to a regular bicycle.

If you are serious about getting a bike with front wheel drive, it’s worth doing properly which would mean sourcing something specially designed for the purpose.

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    Note how heavy the fork is on that TwiCycle - that's no off-the-shelf, stock fork. Also, that crankset on the handlebars is set perfectly to slice your face and/or neck right in half... – Andrew Henle Aug 28 '18 at 9:47
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    @Andrew yes there is a lot wrong with that one - I didn’t want to entertain it any further – Swifty Aug 28 '18 at 9:58
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    @AndrewHenle And the brake cables will wind around the handlebars and chain and... It's clearly not an actual bike. – David Richerby Aug 28 '18 at 10:14
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    @DavidRicherby Pure magic? Maybe set up a GoFundMe so someone can try to buy one and find out? :-) – Andrew Henle Aug 28 '18 at 10:43
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    @David The same way as the other hand cycle, the handles articulate – Swifty Aug 28 '18 at 10:51

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