Originally Posted by
Rick
With 26" wheels my Rohloff gives me a 17" low gear. Rohloff doesn't recommend a gear ratio between front and rear of 2.5 to 1 for GVW above 100 kilos. I have a 50 tooth up front and a 20 tooth in the rear. A Schlumpf Mountain Drive might solve your problem. They are less expensive than a Rohloff or Pinion. You could have 727 percent range. Would a gear inch range of 15 to 110 work for you. The crank is an internal 2 speed. If this interests the OP than look into it. Cycle Monkey is a US importer for the Schlumpf cranks. Recumbent bicycle shops also may have them.
I do believe you are correct. The Schlumpf's come in a standard 5x110 bcd & a type "08" version. It is possible to run the 5x110bcd as a double & run the timing chain to the unused chain ring. They are rated at 250nm of torque, so using one on a tandem
should be ok.
As far as Cycle Monkey is concerned, I have not had luck in any form of contacting them this past year. After many fruitless attempts both email & phone, eventually their voice mailbox said it was full & could not accept more messeges. My only guess is the covids caught up to them & they are no longer in business. Or, so far behind it doesn't even matter anymore.
An email to Haberstock Mobility directly got a prompt response & a new Speed-drive with crank arms Cycle Monkey doesn't even stock to my door within a week via DHL. (Silver, 172.5mm)
I wouldn't have any problem bypassing Cycle Monkey again on the future.