MitchJi wrote:boostjuice wrote:I found this very interesting document while surfing the net.
FULLY ENCLOSED FRAME MOUNTED GEARBOX FOR DOWNHILL MOUNTAIN BIKES
It would be a lot more interesting if the standard specified an auxiliary input.
Gary wrote:Basically, there are two options (well three, counting the Cyclone crankset...).
One is that you use a high-end trials-type front freewheel cranksset, which is basically
nothing more than a high quality White Industries ENO freewheel with special crank arms
that screw into the FW threads. What they typically do is have a fixed 12T cog on the rear
hub, and an 18T FW at the crank. Anyway, what we are doing is using a 22T ENO FW, with
the trials crankarms, and then make an adapter that bolts to the 22T FW and then has a
standard 110mm BCD mountain bike chain ring pattern, so that we can have lots of chainring
choices to achieve the right gearing.
The second option for getting a freewheel into the crankset, is to use a IPS crankset from
some tandem bike setups. This is used sometimes, to allow the second rider on a tandem to
not have to pedal. Again the IPS crankset is nothing more than crankarms that screw into
a regular freewheel, which is attached to a standard 110mm BCD spider. the nice thing about
this setup is that you don't have to make the adapter, but the downside is that like the
Cyclone crankset, they use cheap 16T freewheels. The solution for both, however, is to
replace the cheap FW with an $80 ENO version.
Miles wrote:So, you screw your freewheel onto the trials cranks and then you need an adapter to mate up with one of the three common chainring BCD standards. 104mm 110mm and 130mm. For my bike, I designed a chainring to fit directly to the ENO 22t freewheel (see photo).
The ENO 22t is a particularly convenient one to adapt because it has 5 circumferentially milled slots which can be used to bolt to:
Mitch wrote:After Gary and Miles posted that information Sick Bikes Introduced a White FW that is the same mechanically but more convenient to use and less expensive than the Eno 22t.
Sick Bike Parts also sells:
1. A FW removal tool ($5.95 - a bargain) which works with both their less expensive FW and White FW's.
2. The Cyclone FW cranks which are much less expensive than Echo (the quality is probably proportionate).
Super heavy duty front freewheel made exclusively for Sick Bike Parts by White Industries.
170mm crank set for front freewheel system. Forged alloy for use with square taper spindle.
Freewheel removal tool for both our standard and HD freewheels.
This is the forged (less expensive) Echo Front Freewheel crankset - the black one. It's available in ISIS or square taper.
A CNC'd ISIS trials crank from Echo in 160mm (mod) and 170mm (stock) lengths.
The CNC crank from Echo is machined from 7075 aluminum. ISIS Spline and 160mm and 170mm lengths. It accepts a front freewheel or fixed cogs (Thread 1.37"X24T).
Vision Independent Peddeling System, Crank, Rear, For Tandems, 175mm
Sun Bicycles - Independent Pedaling System Crankset
Price: $162.00 - 180.00
His prices are high but most of the parts are off the shelf.
Motor using 44t plus 44t+32t+22t chain rings:
If you want more numbers, including speed and cadence data,
Jake Odell has a more elaborate gear calculator:
HPV Drivetrain Analyzer
Welcome to the HPV Drivetrain Analyzer. With this program, you can see what the metrics are for the drivetrain on your hpv (bike, trike, etc), if it uses chain coupled sprockets with an optional shaft coupled pair of sprocketsets between the crank and the road. Schlumpf Mountain-Drive, Speed-Drive, and High-Speed-Drive crank ratios are available modifiers in sprocketset #1. Three hub styles are accommodated, a single ratio or direct hub, a hub with up to 15 distinct ratios like the SRAM Spectro, and the Rohloff SpeedHub that has symmetrical ratios.
Math is done in floating point, which means that you can enter fractional numbers for the tooth count. This way you can, for instance, integrate the two Schlumpf ranges into one output display by entering the Schlumpf ratio times each of the chainrings on the crank. For an example of this technique, see the Schlumpf/Rohloff sample config.
There are five optional output tables:
1. A Cadence table showing speed data in miles/hour and kilometers/hour for a selectable range of crank rpm's,
2. a recap of the Input Data,
3. a table of Hub Ratios if the configuration has a ratio other than 1:1,
4. a Split Table showing tooth splits and percent change for shifts among sprockets in each sprocketset,
5. and a Gear Metrics table of gear permutations sorted by the output to input ratio. This table has several optional columns.
At the top of the input panel, there is a selector that will preset the inputs with known or typical configurations, which immediately display output when changed. One of the selections is 'My Configuration'. In this selection...
ThereÃ¢â‚¬â„¢s a common link between the bikes weÃ¢â‚¬â„¢ve reviewed so far this issue: they all use internal hub gears Ã¢â‚¬â€œ and not just any hub gears, but the newest and latest from Shimano, Rohloff and NuVinci. As IÃ¢â‚¬â„¢d also fitted the new SRAM 9-speed to my town bike, the stage was set for a four-way shoot-out.
Links and Information - A lot of High Quality DIY Info
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