Number of teeth on cogs.

[Andy in Sig]

My HPV Street Machine is Rohloff equipped. Has anybody got any idea what is supposed to be the optimal number of teeth on the front cog (is that the chain ring?) and on the rear one? I think I've got 50-odd on the front on mine. Secondly to what extent do those Schlumpf gadgets extend the gear range (I'm thinking of hilly areas i.e. extending at the low rather than the high end)?

 

[Gasman]

Have a look at Kinetic Cycles. The've got some useful info and a gear calculator. I believe that one of the Schlumpf drives (High Speed perhaps) isn't recommended for use with the Rohloff hub but I've also read reviews by people who've done it anyway and had no problems.

 

[ufkacbln]

Redmount offer the option of combining the Rohloff and Schlumpf systems on their Trike. they give (here) details of the gearing options. ICE and Greenspeed also offer both, and a combination.

Mountain Drive; high 1:1, low 2.5:1
Speed Drive; high 1:1.65, low 1:1
High Speed Drive; high 1:2.5, low 1:1

Ratios are detailed on the Greenspeed site

I believe that it is the streses on fixed gears that Schlumpf cannot cope with - although even this is in dispute!.

 

[Andy in Sig]

Thanks Cunobelin. That Redmount Roller looks interestng. I've been thinking about an HPV Scorpion for some time (if I ever get the money together). The two designs are not a million miles apart. How would you rate the two of them comparitively?

 

[Will1985]

I thought I would take a peek into the unknown of this part of the forum and found this post. The Schlumpf chainsets look interesting.

For the Speed and High Speed Drives, do they make it any easier to pedal by having direct drive gearing or anything? I had this sudden idea that it would roast the competition in a Time Trial (although probably highly illegal if it does drive you forward with the same applied force in either setting!!).

Can someone burst my bubble?

 

[Andy in Sig]

I'm not technical enough to answer the question competently but I think the Schlumpf sits in the place normally occupied by the bottom bracket i.e. it is effectively a two speed hub gear masquerading as a bb. Dunno if that makes it illegal or not.

 

[BentMikey]

Will, there's no such thing as a free lunch. It's just a different kind of gearing system is all.