So, these next few pics are an expose of the rear derailleur on the light bike
First 2 pics are of the derailleur when finished @ 67.7 grams
Pic 3 and 4 show a sort of explosion of the parts involved.
The derailleur is a hybrid based on the Huret Jubillee derr.
I had to dig through a few boxes, but found the parts, most of them anyway.
There are some parts not there, they were sold or disappeared. A few parts
there are of aluminum relacemants made way back in the mid 80's which
made a 120 gram version on a 14.75 lb bike. The pulleys are from the 67 gram
version, now replaced.
First all parts were removed/unbolted.
Next rivet heads on the body were drilled out and body dismantled
and pins/pivots pressed out.
The 4 body forgings were machined for larger pins, over sized pivot bolt
w/13mm hex, and excess material removed where not needed/lightening. Also
shaped and polished.
New hollow pins/pivots made from 6-4 titanium with miniature screws 3mm x .5mm
thread used in place of rivets. These were very difficult to machine, in a non production
setting. Titanium heats up very quickly and will seize on a drill or tap. Sometimes
breaking. And then you start over. The only parts made using CNC are the the thin
brass precision washers spacing the 4 body pcs. when joined together w/pins and screws.
Titanium springs had to be made using bike spokes 1 for return spring
and the other for cage pivot. The most difficult was #2. As you can see from the #3
pic., the spring has 3 1/2 windings internally and another 2 1/2 externally as well as
the end pcs.
The lower half or pivot cage assembly is based on the Shimano 7800 derr.
The biggest improvement here is that the original design had 2 pulley bolts
with the upper one threading directly into the derr. body and locked with a nut.
The pulley cages actually pivoted on the shaft of this bolt.
The cages were reshaped/lightened and machined for an oversized aluminum
pivot bolt that has a large flange head which is recessed into the outer cage
and bonded into place with a titanium pin protecting the epoxy in shear.
So all steel was taken out of the derailleur except 1 part was actually added.
The oversized pivot bolt allows for the use of a thin low profile bearing inserted
in the lower housing that the cages pivot on. The pulleys are actually remachined
shimano upper pulleys with the ceramic bushing/bearings. They can be seen in pic
#4. Endcaps were made by machining a mould and pressed out of Coke cans, as
well as the shim spacer/washers.
As I was nearing the end of the hill climb project, I decided to black anodize everything.
So the derr. was dimantled, pins pressed out, pivot unbonded, and then anodized.
Then reassembly. The parts lost a bit of weight during stripping of clear anodize
and some fit problems.
So...How does it shift? Well for a 6 spd old school derailleur, non indexed actually quite
well. The new narrow chains and cassettes w/ shift indents help a lot. Major difference
is that the body parts aren't quite long enough and the body spring wether steel or ti,
isn't strong enough to push out to the smallest cogs on a 10 or 11 spd.
On an 11 spd set up it can get the 9 cogs on the inboard side if you give it an extra
couple links. Which for a hill climb bike works quite well.
The ceramic bushing pulleys were replaced because they were a pain. The oil would dry out too quickly requiring dimantle & oil. And the dust caps had too deep a shoulder on 1 or 2
and would rub/add friction. So I made new one of delrin. They look a bit like the Extralite,
because I just visually used them as a pattern for hole placement. I don't know the differences
in the guts, but I can tell you that mine have 2 small ceramic bearing each and 3 spacers.
The derailleur now weighs 64.6 grams.
There are probably 150 or more hours into this derailleur.