Saturday, July 17, 2010

utah trikes talks about Schlumph mountaindrive, details

Combining the Schlumpf HSD with rear internal hubs
For the ultimate in gearing solutions, we like to combine the Schlumpf HSD with internal hubs in the rear. This provides a super easy-to-shift system that is perfect for triking in mud, water, and snow. We have tested the Schlumpf HSD with the Shimano Nexus 8, Nuvinci CVP, and Rohloff SpeedHub. Note that the high torque of the 27-tooth chainring voids the Rohloff warranty, so you do this at your own risk. Under special circumstances we can fit the HSD with a 34-tooth chainring which brings it closer to Rohloff’s minimum requirement of 36 teeth.

What about efficiency?
Planetary Gears - The main criticism that I ever hear about the Schlumpf drives are the stated efficiency of the drives. According to the latest test the planetary gears are rated at 95-97% efficiency when compared to a chainring. In other words, a 68-tooth chainring would be 3-5% more efficient than the Schlumpf in overdrive. What does this mean? Well, it means that if you could actually find a 68-tooth sprocket and had it on your trike instead of the Schlumpf HSD, you might be able to go a little bit faster.

Riding with the Schlumpf
I ride with the HSD overdrive engaged probably 90% of the time. My lowest gear without downshifting the HSD is about 42 gear inches, which I find to be low enough to handle during the stop and go of my regular commute. Should I ever have to make a sudden stop, or forget to downshift, I always have a bail-out gear by just clicking the shift button.


D: I would not select a gear hub/ S Drive combo that results in the S Drive engaged most of the time.
Not a big deal, but a few % efficiency lost all the time adds up.
Better, I say, to finesse the chainring/cog combo and gear hub/S drive combo to allow near-direct drive engaged as much as possible. The Schlumph drive should only be occasionally engaged.

The potentially wide range of gear inches possible with an S drive means buying an expensive wide gear-inch range gear hub could be a waste of money.
I remain unable to locate any info that suggests the 1.65x drive is any more efficient that the 2.5x drive.
That is the only thing that would change my mind.
Plus the 2.5x range S drive will merely results in a wide area of overlap in gearing - no point at all.

Changing the gears will be simpler but slightly reminiscent of the half-step gearing used in yester-year.

A large # of teeth on the chainring and cog will result in improved efficiency but also a weight penalty. Plus technical difficulties.
D: this remains the benchmark study.

Fussing with the Rohloff min. # os teeth on the chainring is not the salient point here.
That chainring will simply be more efficient, if matched with a similarly larger cog.

E.g. NuVinci 2:1 ratio. 52-36. Or 48-24.
Can the 27 be used?

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D: well it exists.

The Nuvinci is eminently suitable to automatic gear shifting. Combined with the silent aspect, it could carve out a niche.
It should stop trying to compete on a conventional basis with gear hubs.
I'm sure even a 'dummy interface' of cheap and electric vs computerized electronic nature could work.

My design philosophy, as somebody planning to cross Canada on a touring bike, is:
1) always take the weight penalty in exchange for improved efficiency
2) expect a prolonged mid-speed level
3) anticipate the need for a 'killer granny gear' given 1).
This pretty much means a mid-range gear hub with a Schlumph drive.

I'll ask Utah Trikes about whether the 2 high speed S drives have different efficiency.
Not sure why I'd spend an extra 100 on the new Alfine 11-gear if the IM 9-gear plays well with the S drive any way.
Other than that the 400%+ range might be more use by itself prior to the fairing addition and S drive upgrade.


Anonymous said...

Pen and ink is wits plough. ............................................................

Dino Snider said...

keep it up with the cryptic nonsense, and i delete all these asian posts! grr
then block u

dino snider said...

Look you stupid shits, stop it with the zen crap. Gonna delete all your garbage! Fucking spammers....