Author Topic: Travel Agent mod to replace rear deraileur loop  (Read 1479 times)

Travel Agent mod to replace rear deraileur loop
« on: 05 September, 2021, 04:44:56 pm »
I got so fed up with indifferent shifting on the tandem (105 STi 10s) I decided to bodge a fix.  As reported elswhere in this fine forum I thought the shifting issues have been banished when we were forced to swap our titanium frame for a rather nice one made from 853 tubing.  Certainly the shifting has been great but has been worsening recently.  Someone, Biggsy maybe, sugested it was the new cables and he could well have been right.

I had 2 travel agents in the bottom drawer, one new and one with a notchy pulley bearing which is the one that was modified.  All I can say is the shifting was so easy to set up and is crisp and light and accurate (so far!).

Travel agent mod 34 tooth by Russell Wiles, on Flickr

Travel agent mod 11 tooth by Russell Wiles, on Flickr

Lower one has lost its cable adjustment and the hole openened up to 5.5mm to acept the upper unit.  Also I cut off 5mm or so to reduce the overall height to allow cable to pass between derailleur and QR.  6mm washer added between lower agent and derailleur body to allow for clearance between pulley and lower adjustment screw,

I'm guessing that there migth be  propriety item out there but I'm not aware of one.

The cable adjustment lock nut is now snugged up before anyone comments!

Paul

  • L'enfer, c'est les autos.
Re: Travel Agent mod to replace rear deraileur loop
« Reply #1 on: 05 September, 2021, 04:58:57 pm »
Oh, that’s some nice fettling.

What keeps the top one in place? I understand that you’ve slotted it into the bottom one somewhat, but it looks to me as though it might move around a bit. Is it mainly/purely the tension in the cable?
What's so funny about peace, love and understanding?

Re: Travel Agent mod to replace rear deraileur loop
« Reply #2 on: 05 September, 2021, 05:12:34 pm »
The cable is short and stiff missus so there doesn't seem to be movement, cable tension looks like it's enough.  I'll post back after a few rides.

Re: Travel Agent mod to replace rear deraileur loop
« Reply #3 on: 05 September, 2021, 09:43:14 pm »
I'm guessing that there migth be  propriety item out there but I'm not aware of one.
Not as good as re-using existing parts, but there's a Shiftmate Zero which does the same as your bottom pulley.
I haven't used that one, but the two versions I have used (Which also change cable pull) work flawlessly.
http://www.jtekengineering.com/shiftmate/shiftmate-zero/

Re: Travel Agent mod to replace rear deraileur loop
« Reply #4 on: 06 September, 2021, 08:10:37 pm »
Well, we did 33ml today, reasonably hilly so a lot of gear changing, on a tandem there's far more changing than on a solo, and the gear change was near perfect.  One shift in the middle that required a further movement of the lever and one shift from 3-2 that ran onto 1 for a brief moment before settling on 2.  So in the high hundreds of shifts only 2 were not perfect.  That's around 99.9% I reckon.

What I did notice right from the start was how light the shifts were moving up the cassette, so much so that I shifted 2 at a time for the first few.

A relavation!

Paul H, yes I was aware of the Shiftmate zero but it doesn't do a 180deg bend as you point out.  Prior to this I was thinking of using a shiftmate to convert to the long cable movemant of SRAM and using a SRAM mech.

Re: Travel Agent mod to replace rear deraileur loop
« Reply #5 on: 06 September, 2021, 11:09:21 pm »
Well, we did 33ml today, reasonably hilly so a lot of gear changing, on a tandem there's far more changing than on a solo, and the gear change was near perfect.  One shift in the middle that required a further movement of the lever and one shift from 3-2 that ran onto 1 for a brief moment before settling on 2.  So in the high hundreds of shifts only 2 were not perfect.  That's around 99.9% I reckon.

What I did notice right from the start was how light the shifts were moving up the cassette, so much so that I shifted 2 at a time for the first few.

A relavation!

Paul H, yes I was aware of the Shiftmate zero but it doesn't do a 180deg bend as you point out.  Prior to this I was thinking of using a shiftmate to convert to the long cable movemant of SRAM and using a SRAM mech.

Would two noodles work? Or a bit of nicely curved 8mm microbore copper? I'm not entirely sure if the two shiftmates are being used as cable guides or are actually pulling cable.

Kim

  • Timelord
Re: Travel Agent mod to replace rear deraileur loop
« Reply #6 on: 07 September, 2021, 12:25:44 am »
Also, how does this compare to a derailleur with the cable exiting at the appropriate angle?
Careful, Kim. Your sarcasm's showing...

Re: Travel Agent mod to replace rear deraileur loop
« Reply #7 on: 07 September, 2021, 09:23:34 am »
There's no cable pull adjustment going on, the pulleys are just guiding the inner around the curve.  As they have ball bearings there is very little friction.

What is an appropriate angle Kim?  Do you mean the SRAM direct pull arrangement?  I was just working with what  had and spending no money on it.

Kim

  • Timelord
Re: Travel Agent mod to replace rear deraileur loop
« Reply #8 on: 07 September, 2021, 12:03:48 pm »
There are certainly rear mechs where the cable exits in a more-or-less straight line along the seatstay/chainstay.  Barakta's trike has an SRAM one that works that way, though it seems that any benefit is immediately defeated by the grip shifter being a grip shifter.

Avoiding that loop of inevitably-gummed-up cable certainly seems like a good idea, by whatever means.
Careful, Kim. Your sarcasm's showing...

Re: Travel Agent mod to replace rear deraileur loop
« Reply #9 on: 07 September, 2021, 05:25:11 pm »
I thought that's what you meant.  If I was feeling rich I would have gone down the route of a shiftmate at the bars end to convert to the long pull of SRAM and a SRAM mech to match.  SRAM shifters, if available in triple, would have the step after.

Kim

  • Timelord
Re: Travel Agent mod to replace rear deraileur loop
« Reply #10 on: 07 September, 2021, 06:04:35 pm »
I have vague recollection of some Shimano MTB mech with the same arrangement.  Seems eminently sensible, especially off-road.
Careful, Kim. Your sarcasm's showing...

Re: Travel Agent mod to replace rear deraileur loop
« Reply #11 on: 08 September, 2021, 08:42:22 am »
I think* most/all Shimano MTB mechs were improved a good 10 years ago.  This photo appears to be 2012 model year: https://images.immediate.co.uk/production/volatile/sites/21/2019/03/1302770086707-fue0rntx5qaf-1bd97a5.jpg?quality=90&resize=800%2C605

The cable angle still works better routed up the seat stay than the chain stay, though.


*I'm a bit out of touch as all my gears have been inna can for a similar period.
Life is too important to be taken seriously.

Re: Travel Agent mod to replace rear deraileur loop
« Reply #12 on: 08 September, 2021, 09:24:31 am »
Also, how does this compare to a derailleur with the cable exiting at the appropriate angle?

...or frames that route the rear disraileur cable along the top tube and down the seat stays...
If it ain't broke, fix it 'til it is...

Re: Travel Agent mod to replace rear deraileur loop
« Reply #13 on: 08 September, 2021, 10:55:17 am »
The model name Shadow rings a bell somewhere.  I always thought there was a very small clearance between that mech and the spokes.

My rear mech is not that old, it was new in 2016.  It's actaully a 9sp mech which is recommended with 10sp STIs.