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Author: Subject: How about something different? mtb
02GF74

posted on 1/5/20 at 09:03 AM Reply With Quote
How about something different? mtb

following on from Allen Millyards Z1, here is an MTB he made way back as I know there are one or two interested.

anyone figure out how the gear change works - I failed to catch on to the explanation, if there indeed was one.

https://www.youtube.com/watch?v=iUak9sqJmnM

some info about the gearbox.
https://www.pinkbike.com/news/allen-millyard-part-1-2008.html






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rf900rush

posted on 1/5/20 at 09:36 AM Reply With Quote
I watched the Kawasaki 6 being made recently.
Then spent another hour looking at some of his related videos.

This one was WOW.

Most of us dream of doing one of these projects. he's made more projects than I have time to look at.

Once again wow.

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jps

posted on 1/5/20 at 09:39 AM Reply With Quote
Very interesting and innovative. The latter doesn't seem to be that common in the bicycle world!

quote:
Originally posted by 02GF74
Anyone figure out how the gear change works - I failed to catch on to the explanation, if there indeed was one.


It reads to me as though he is saying it has a Nexus hub gear. It looks like he's relocated that from the usual rear hub position into the frame - above the bottom bracket. I thought with a hub gear you had to 'lift' slightly when changing to get the next gear to engage, but you can definitely click from high to low (or vice-versa) at standstill.

I wonder how they'd deal with changing the chain - and where the adjustment is to take up chain tension. Eccentric bearings?

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steve m

posted on 1/5/20 at 10:14 AM Reply With Quote
I too watched a lot of Alans Vids, his skill is incredible, and all done in a home garage, and BBQ

I haven't a clue on how that gearbox works, but would like to see inside





Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at




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jps

posted on 1/5/20 at 11:36 AM Reply With Quote
quote:
Originally posted by steve m
I haven't a clue on how that gearbox works, but would like to see inside


Steve - if i've understood it correctly it's this: https://en.wikipedia.org/wiki/Epicyclic_gearing

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02GF74

posted on 1/5/20 at 11:43 AM Reply With Quote
explained here:
https://www.youtube.com/watch?v=_Q5iEywX3yM






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SPYDER

posted on 1/5/20 at 11:44 AM Reply With Quote
GT bikes did a similar thing in 1996 with their "Gearbox Concept" and then with the iT1 production bike. I nearly bought one a couple of years ago with the plan of doing an electric conversion. Both used a Nexus gearbox built into the frame above the crank.
All credit to Alan. Gt probably spent many thousands of dollars and employed a team of designers to do what he did in his garage.

GT Gearbox Concept click





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coyoteboy

posted on 1/5/20 at 12:17 PM Reply With Quote
Hmm not really sure what was innovative about that at all - I remember it at the time.

As mentioned above the gearbox at that location has already been investigated (and is valid - I'd love a gearbox bike but they're so damn heavy and limited in range).

The type of box is well known and has been in existence since the 30s or so, but usually used in the hub and fed by a single gear.

The front triangle - not really ideal - that's nicely manufacturable in a home shop, but aweful from a strength or stiffness to weigh ratio in that application. Not to mention the fact that there's not really a stiffness issue with normal DH bike frames of the time - strength, sure, people were snapping head tubes off left right and centre lol, but that's again easily rectified on normal designs.

Having the chain enclosed in the swingarm is interesting, the route up to the pivot and down taking out the travel-shortening of the load path - still very much in existence since the turn of the century. Complete PITA if you snap a chain, as happens regularly - though you could argue "because of poor derailleur control".

The rear axle is the norm on a range of DH bikes and had been for a decade or so, only his implementation of it is somewhat clunky.

The rear shock - jesus christ, it's enormous - what does that weigh?! What's so special about it? The vid suggests mounting it between the arm and seat stays (as such) is unheard of - not sure how, I had a similar arrangement on my production bike at the turn of the century.

I mean I'm always impressed with anyone who designs something like that from scratch, and especially if they can make it. I just don't really understand what's innovative. The funny side point is that most DH bikes are back to the original bike format - because it's simple, parts are cheap and easily replaced and they don't require 15 different tools to disassemble.

Maybe I'm feeling grumpy today?

[Edited on 1/5/20 by coyoteboy]





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02GF74

posted on 2/5/20 at 05:47 PM Reply With Quote
^^^ I think you are being slightly grumpy. Innovative would be doing away with the chains by having the crank drive the gearbox via gears. That way they could be made much smaller but wider to take the power. Drive to the rear wheel is screaming belt drive, assuming it's not already, ideal for an enclosed drive system or maybe even shaft drive.

The frame looks massively over engineered.






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