Sorry but I'm going to rain on your parade a bit by being skeptical about the improvements you claimed.
There is very little friction from the bend at the bottom of the BB shell, particularly when a plastic guide is involved – the contact is short and (more importantly) the tension of the shift cable is light. Most of the friction will be from the significantly longer runs of housing from the barend shifter to the cable stop, and from the cable stop to the derailleur. Anyone with downtube friction shifters that are set too light will attest to almost frictionless shifting with all the tactile feedback coming from the derailleur return spring, particularly with the front derailleur (that actually wraps more degrees around the plastic BB shell guide). I suspect by having to thread the shifter cable through your contraption, you've also cleaned up at least the derailleur-side of the run and refined the cable adjustment, leading to most of the improvement you observed. In addition, while the newer Rivendells have longer chain stays necessitating longer cable runs, the extra length is *unhoused*, meaning there should be no additional friction compared to bikes with "normal" chain stay lengths. Last but not least, the BB shell is at the lowest point of the cable run. Water ingested into the custom tube guide won't be able to evaporate away quickly. Even if you use stainless cable and tubing, there's still pooling, which shouldn't happen with a well-maintained bike. On Tuesday, December 3, 2024 at 1:47:27 PM UTC-8 krhe...@gmail.com wrote: > Upon owning a Rivendell Clem Smith Jr. "L" bicycle, I have very long chain > stays. This has given me to thought of how can I increase the speed of > shifting by reducing the friction and slack times for better shifting > through the BB cable guide for my right indexed Shimano Dura-Ace SL-BS77 > bar end shifter. > > I came up with an idea. I took a curved V brake noodle. I removed both end > pieces and the plastic sleeve from inside. I measured the appropriate > length to cut it. I took a Dremel tool and bit. I carefully carved a wider > channel on the plastic BB guide to accommodate the steel tube. I repeatedly > kept bending the piece of tubing to the right angle for the best passage of > the rear derailleur cable. I returned the plastic sleeve to the steel tube > and cut it to a shorter length. > > Once that was done, I placed two plastic cable housing caps on either end. > I used Gorilla Clear Maximum Strength Construction Adhesive to glue down > the steel tube onto the BB guide. Let it set for 24 hours. > > Upon my return, I threaded the rear derailleur cable through the new tube > and pulled out the slack in the Shimano RD M531 long caged rear derailleur > and tighten the anchoring bolt. > > My test ride results are as follows: > > The report on the custom BB steel cable guide I made, there was a > significant improvement in shifting up into the lower gears, whilst > shifting back down into the higher gears, there was a slight delay. With > such a long rear derailleur cable, I believe this is going to be expected. > I am happy to say that there was no "ghost shifting " whatsoever. YAY! All > the slack in the cable was pulled out. (I had prior issues with 'ghost > shifting". I was unaware of the rear derailleur cable as loose and needed > fixing.) > > No grease nor oil has been applied inside the plastic sleeve of the tube > at this time. > > Overall, I feel my custom BB steel cable guide has been an improvement > over what was before. > > Yes, I do have a lot of helicopter tape on my frameset. > > Kim Hetzel, who loves to tinker. > > [image: 20241123_213949.jpg] > > [image: 20241128_060401.jpg] > > -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/rbw-owners-bunch/27cc8677-bc88-4f4a-a291-e33f39992f77n%40googlegroups.com.
