Intermediate Drive

• Many home built HPV's have an intermediate cog mounted on what was the old bottom bracket. (main pedal axle) Recently what I've found is the cone nut that holds a pedal axle in place is the same thread and size as a rear cassette. (set of cogs mounted on the rear hub) The idea then is to use a rear cassette as an intermediate. The ratchet part inside the cassette needs to be removed so that it will freewheel both ways with all the bearings etc left in place. The BB then has only the right cone nut screwed in half way and the casette screwed onto that nut. The rear chain then could go to one cog and the front to another. With a bit of creative arrangement a derailuer can be added to give some gearing as well and the cogs may be able to be rearranged in the order you want. I would expect the 2 chains to clash when on side-by-side cogs with the existing cog spacing on a cassette so this may need to be made a little wider at that part. This shouldn't be hard as they usually have spacers between each cog anyway but it may mean you lose a cog in the group to make this happen.
  Thinking about the strength of this arangement, both the pulling motion at the front will be mostly compensated by the pulling from the rear so I would expect it to be strong enough. As the 2 chains get moved apart there is a twisting force but I don't think this is strong enough to cause problems.

  Now there's one problem with all of this. The right hand thread on a BB is usually on the left which means the cassette won't screw on so you will need to improvise. You could either re-fit the BB the other way round, re-thread the tube or weld a right hand thread cone to the outside of the right one.

• See the SWB USS Trike & SWB ASS Bike at Darryl Shelswell's Web pages.

• See the Baracuda

• Gary Adderton's Sociable tandem trike.

• IHPVA

• Dave Barrett's Econobent Saga
  
  
• Making an HPV Jackshaft (Intermediary gear)
  
  
• From: William Gaines
  Subject: RE: Freehub as Jackshaft
  Date: Wed, 3 Nov 1999
  I have used a cassette hub with a separate double roller bearing (from a datsun water pump) with very good results. I made an aluminum insert that I pressed into the inside of the cassette hub.
  The nice thing about the bearings that I used was that they slipped neatly into a tube that I brazed on to the frame. The tube that I used was a metric size. It also was from a Datsun. It was the internal tube for the front shock assembly (the factory did not use a cartridge type in 72'). The distortion from brazing is all that I needed to hold the bearings in place. I'm no powerhouse, and I do not put a lot of miles on this vehicle, but I have not had any problems in the 15 years that I have used it. BTW, when I first used this bearing, I left the flange on the shaft, and used it to bolt the flange of a sectioned rear hub (which had threads for a free wheel) I lockwired the freewheel on to the hub. With the cast iron flange, this was heavy, but cassettes didn't exist at the time! A few years ago I was putting the trike on a diet and obtained a cassette shell. I ground the internal palls down as much as I could, and turned a bit of aluminum to give a press fit. I added some set screws for locking the insert to the bearing shaft. I saved a pound or so!
  
  
• From: "Ross or Judy" <rossjudy@mars.ark.com>
  The Intermediate drive that I am using has 4 speeds, attaches with a quick release, and gives me a range of 15 to 96 gear inches using a 32 tooth front.
  I used a 7speed shimano casette and freehub with pawls removed and a 7spd on the 16" rear wheel giving 28 gears that I use 16 of. Grind or file about 3mm of the QR nut to decrease the diameter so that it fits into the right side of the freehub.
  Remove all sprockets.
  Grind or file out small slots in the 12 tooth sprockets so the sprockets fit on backwards.
  Replace the 12 first . It is the driven sprocket.
  Make a spacer about 1/16" thick with diameter 1/16" or so larger then 12 tooth sprocket diameter.
  Place it next .
  Place the following sprockets backwards as they are driving instead of being driven.
  12
  spacer
  16
  spacer
  21
  spacer
  28
  Lock nut
  Bolt on with quick release (reduce the nut diameter so it fits into the freehub bolt hole )
  Add a post for a front derailer .
  The hardest part is adding the post for the derailer. Other then that its all very easy and works better then many triples. I love the neat front chainline.
  

• How to calculate gear inches with an intermediary gear
  Date: Sun, 9 Jul 2000
  From: Charles Mantey
  With an intermediary gear you just need to add another ratio to the gear forumla.
  Standard Gear Formula:
  Gear Inches = (Drive Wheel Diameter) * (Front Teeth)/(Rear Teeth)
  With an Intermediary gear the formula become:
  Gear Inches = (Drive Wheel Diameter) * (Intermediary Teeth)/(Rear Teeth) * (Primary Teeth)/ (Intermediary Teeth)
  So lets say you have the following:
  Drive Wheel is 26 inches in diameter Rear Gear is 32 teeth Intermediary gear is 30 teeth Primary gear at the cranks is 26 teeth.
  Gear Inches = 26 * 30/32 * 26/30 = 21.125 Gear Inches.
  Sheldon Brown has a nice explanation about gear inches at http://www.sheldonbrown.com/gloss_g.html#gearinch
  

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Thursday, 29 January 2009