Ralph has been suffering a bit of late. I could see the chain needing replacement & I wasn’t happy with the chain tensioner alignment, so it was time to take action. My earlier postings on “Ralph’s flaws” probably cover my issues with the chain tensioner & occasional chain loss on unfolding. Having removed the rear wheel & taken off the rear cog for inspection prior to obtaining a replacement to go with a new chain, I felt compelled to look further & wanted to check out a “chewed up” Alfine 11-speed hub seal under the rear cog. I shall not repeat here my embarrassing boo-boo with the seal (refer my “Extra tools” post for the sordid details) but then set out to source all the parts I would need.

Checking an exploded diagram of hub parts, I determined that I needed to obtain the seal (or dust cap, to give it its correct name), a chain guard (missing from Ralph?), rear cog & chain. Thinking I should support the local bike industry, I sought the Alfine parts from Shimano – only to find that I could only get the dust cap by purchasing the whole internal hub assembly! Rather than spend a few hundred dollars (at least?) locally, I turned to SJS Cycles, my UK online Brompton parts source who also deal in Shimano parts. Yes, no problems with the individual parts & everything arrived promptly (about $15 total for the dust cap & chain guard). I had already obtained the dust cap tool via eBay (no prizes for guessing that I couldn’t readily obtain it locally).

The distorted chain tensioner & poorly engineered sprocket wheel mounting (once again, this background in earlier blog posts) were definitely to be addressed but I first needed to obtain better spacers to fit between the sprocket wheels & chain tensioner arms. No luck with finding anything to fit or adapt, so I considered getting some spacers turned out of alloy but then it occurred to me that 3D Printing the spacers would be the ideal solution. A bit of Internet research, a phone call & my simple spacer requirements (no need for me to generate 3D imaging for the basic cylindrical spacer) were produced & delivered in about 2 working days. I’m very pleased with my first foray into 3D Printing!

Refer pics of an ABS plastic spacer & the chain tensioner components – showing new & old (stainless steel) spacers –

The reassembly work started with grinding a protrusion off the new plastic chain tensioner body (something included for the normal use as a 2/6-speed derailleur unit) & creating a little more clearance to the Alfine gear change mechanism. Then I could assemble the jockey wheels with my new spacers & the chain tensioner was ready for installation. For the rear hub refresh, I fitted the new dust cap & then the chain guard (missing from Ralph & I’m pretty confident that it was left off through being impossible to fit, once somebody had mangled the dust cap through not using the correct fitting tool). The new rear cog went on & was retained by its circlip & finally the gear change mechanism went back on. The rear wheel was then refitted, a new chain added & the chain tensioner attached. Done!

How has it worked out? Ralph is purring! The new dust cap & chain guard now provides less chain drag, noticeable when back-pedaling, which allows the tensioner to maintain pressure on the chain during the fold & unfold operations, thereby curing the chain drop issue? The new chain tensioner & better sprocket wheel support has improved the chain alignment & probably also lessened drag on the chain. (I had thought that the chain drop came just from the distorted chain tensioner, bad chain alignment & maybe from the tensioner spring action appearing to be weak but hadn’t recognised the effect of the damaged hub dust cap.) Ahhh… bliss is an efficient bike!

Before & after pics below –