1996 Eight Speed Cassette meets 2016 replacement

My dog walking mountain bike turns 20 this year, I bought it in May 1996 after my junior year of engineering undergrad.  It's now my most ridden bike because I use it to walk the dog several miles almost every day.

Shimano 11-28 cassettes, 1996 LX, 2016 Alivio

The new cassette might be lighter, it's drilled and the 2nd largest cog is riveted to the largest as a carrier with 3 arms removed

Worn and hooked teeth on old cassette, the 2nd/4th/5th largest cogs skipped the worst

The cassette teeth were already hooking when I replaced the chain 3 years ago, along with a skipping middle chainring and a new rear wheel because the original rim split.  When I put a new 3rd chain on last week, it skipped on at least 3 cogs, so the original cassette's done.

The new cassette's made in Indonesia, I've noticed that Japanese companies like Shimano, Canon, and Sony initially make their high end stuff in Japan, and later revisions and lower end stuff are eventually outsourced to Taiwan, China, Mexico, Singapore, Malaysia, etc.  Since the latest mountain bike cassettes are 11 speed, no more 8 speed cassettes are made in Japan.
 
Pirelli also moved Diablo Rosso II 110 front tire production from Germany to China, I noticed while changing tires on the ninja 250 and also on RC390's at the KTM demo.  The vibration from the single cylinder engine on the RC390 was ridiculous.

The rear rim split 3 years ago, it's the 2nd rear rim I've worn out this way

 The ninja 250 needed a new chain last year after 25k miles, and I realized I have accumulated a chain tool collection spanning 24 years.  A 1991 Cyclo Rivoli, a 1995 hyperglide compatible Cyclo Rivoli, a 2000 Crank Bros multitool, a 2004 Park folder, and now a 2015 Motion Pro PBR

Red Logitech Momo Force Hub Repair Method and 3D Printed Replacement

The hub of my red Logitech Momo Force that I’ve owned since 2003 broke last week.  A replacement part is not available.  I came up with a repair method that can also reinforce unbroken hubs. 

I have not tested the repaired hub yet, because while I was measuring it to design a 3D model for my friend’s 3D printer, I found a completed 3D printable hub model by user StoraBrollan on thingiverse.com.  I forwarded his model to my friend to look at and continued working on my own 3D model, because I wanted to include my reinforcement.  Then my friend texts me that he went ahead and printed StoraBrollan’s hub.  Link to StromBrollan's replacement hub 

With a little work to correct ABS shrinkage on my friend's printer, StromBrollan's hub design is installed and working.  I designed another 3D printable part to add my reinforcement to his 3D printed hub.  My part also keeps the steering angle limiter aligned if the hub breaks in the same place again, to protect the wheel angle sensor from over rotation.  Link to spacer  

Repair/Reinforce Method

The force feedback gear is held onto the hub with 3 internal m3x20mm screws that thread into an external metal ring.  The hub breaks just past the screw heads because that center section has to transfer all of the gear torque to the steering wheel.  My hub had a crack almost all of the way around.  It didn’t crack all the way because I finally checked it after hearing a loud crack and realizing the wheel could tilt. 

The force feedback gear and threaded metal ring slide onto the hub from the outside, and are held on with screws from the inside. 

Large end of hub with internal ledges, the force feedback gear screws go into the 3 hole pattern deep inside.  The hub eventually breaks just above them.

The large opening of the hub has inner ledges.  I drilled and carved a metal washer with a rotary tool and metal files until it would sit on the ledges.  Three notches have to be made to fit around the pockets that prongs on the steering wheel mounting ring fit into from below.  These pockets and notches help because they prevent the washer from turning.  Now longer m3x45mm screws can replace the 20mm screws holding on the force feedback gear, and clamp the hub back together. 

Threaded gear mounting ring, PVC spacer, notched washer, and m3x45mm screws

I made a spacer to hold the m3x45mm screws straight, by sanding a piece of 3/4" PVC pipe to fit inside a 1” PVC pipe, gluing them together with PVC cement, and cutting slots.  This will hopefully allow the screws to transfer some torque between each other to the notches of the washer, instead of all of the torque going through the hub center section and cracking it again.  The spacer needs a gap under the notched washer so that the washer can provide a clamping load on the hub, my spacer thickness was about 18mm.  A spacer could also be made with no sanding or gluing from a 1”x1/2" PVC bushing, I just didn’t want to go to the hardware store.  Or the spacer could be 3D printed.

Hub with spacer for holding longer screws straight

Hub with spacer, notched washer, and longer screws

Repair components assembly

I also glued the crack with ABS pipe cement, and used my repair method to clamp it while the cement set.  The small end of the hub was also cracking where the wheel angle sensor fits, so that also got ABS cement and metal foil tape.

Additional repair materials

If the cracked section of hub broke into pieces instead of forming a crack, it might be possible to cut it out completely, make a new center section, and bolt it all together with my repair method.   In that case I might want to run the screws in the other direction so I could fasten them with 3mm hex nuts.  I also might drill everything out to use fatter m4x45mm screws and nuts.

3D Printed Replacement Hub

Link to StromBrollan's replacement hub

My friend printed the hub in ABS, which can have more shrinkage than the PLA that StromBrollan used.  This may have caused the tiny <1mm loose fit at the bearing and gear contact areas.  To see if the part would work anyway, I used layers of metal tape to build up these contact areas.  The gear keyways had to be shaved a little wider, and the edges of the cone holes had to be shaved for the gear mounting ring to lie flat.  PLA has less shrinkage and better layer adhesion than ABS, but ABS can be tougher, less brittle, and can be carved after printing.  I currently have no preference.

3D printed hub with metal tape to build up contact surfaces

Force feedback gear installed

3D printed hub screwed to steering wheel, the steering angle limiter protrudes from the metal mounting ring

My notched metal washer fits in the 3D printed part too, but longer m3x50mm screws are now needed to reach the gear mounting ring, because a ramp of material to aid 3D printing covers the shapes the notches used to mate with.  My local Ace Hardware store had both 45mm and 50mm m3 metric screws.  Those shapes only protruded because the injection mold designer removed as much plastic from the hub as possible to save money, which we're not concerned about anymore.  My own preliminary hub design on thingiverse is nearly solid and needs some hollowing out and 3D printing overhang ramps, and is actually more suitable for machining than printing.  The washer might be able to turn now, so the 3D printed spacer I designed might not transfer as much torque through the 50mm screws to the washer/hub interface, but it will still keep the steering angle limiter on the steering wheel mounting ring aligned if the hub breaks in the same area as before, to protect the wheel angle sensor from over-rotation.    
Link to 3D printable spacer 

3D printed reinforcement spacer, notched washer, and m3x50mm screws

Assembled reinforcement components

3D printed hub without spacer

3D printed hub with spacer

3D printed hub with reinforcing washer screwed down

Test fit

Test fit

Big thanks to StromBrollan and my friend with the 3D printer.