- 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
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
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
Shelswell's Web pages.
Barrett's Econobent Saga
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" <email@example.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.
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
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
With an Intermediary gear the formula become:
Gear Inches = (Drive Wheel Diameter) * (Intermediary
Teeth)/(Rear Teeth) * (Primary Teeth)/ (Intermediary
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
Thursday, 29 January 2009