The Shimano SLX 10-speed mountain bike drive system provides all the components for a mountain bike. We will use the derailleur, the cassette, and the shifter. For cranks we need a square taper approach (see an upcoming post). We have no front derailleur. Not sure if we'll use their disc brake. SRAM has one made by Avid. I kinda like that name.
The most crucial component is the derailleur. The Shimano SLX RD-M675 10-speed SGS Rear Derailleur offers much of the features of the fancier XLR line. This includes some clever techniques that make sure the chain always has tension. This is key as a mountain bike jumps over rough terrain. In the handcycle, this will be a useful feature because you often turn the steering 90 degrees, which puts the chain sideways over the cogs which are now in a horizontal rather than vertical position. On my older bikes, if you backpedal in this situation, you will likely have a chain come off. And that's a pain. But with this derailler, maybe the tensioner will help avoid the situation.
The Shimano XTR CS-M980 10-Speed 11-36 Dyna-Sys Cassette X is ten speeds and should fit on the Bionx front wheel, as well as in the intermediate derailleur position.
The M980 is a premium product, selling retail for about $200. The M980’s largest three cogs are made from titanium. This saves 3.5 oz over the less expensive cassette. Taken together, the two more expensive cassettes add about $250 to the retail parts cost, but they save about half a pound, and they reduce the rotating mass. This seems like quite a nice win for the money.
The Shimano SLX SL-M670 Shifters - 2x10 trigger shifter looks like it will work for the front derailleur which has an unmodified cassette. It won't work on the intermediate derailleur once we're done mucking with the cogs. We'll be taking a ten speed and making it 8 speeds or even 7. (The same thing on the New England Handcycle is 4 speeds.
Here's how it looks on the New England Handcycle (circa 1982!). Note 4 speeds and one drive cog.
The shifter controls on the New England Handcycle is a click shifter on the left side running a derailleur, and the right side is just friction and it runs the intermediate derailluer.
So lets look at what we might do with 2 times as many cogs as we used to have!
In the intermediate position, the cogs would be arranged as follows:
ORIGINAL: 11, 13, 15, 17, 19, 21, 24, 28, 32, 36T
Modification:
Remove the 28-32-36 titanium grouping
Remove the 24 and save it as a drive gear by putting at the end when done.
Remove the 19 to create additional space.
Rearrange with proper spacing
Replace the 28-32-36.
Add the 24 on the end.
MODIFIED: 11, 13, 15, 17, __, 21, __, 28, 32, 36T, 24
This rearrangement will mean we can’t use the trigger shifter. Will need to find a regular friction shifter for the intermediate derailleur. That’s the way we do it now. The front one uses a click shifter.
Comparing the original and the modified:
ORIGINAL: 11, 13, 15, 17, 19, 21, 24, 28, 32, 36TMODIFIED: 11, 13, 15, 17, 21, 28, 32, 36T, 24T
(bold sprockets are one unit)From our parts database: (Click on the underlined part to find out much more.)
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