urbanknight

Just bought this bike and this looks like it should have something in the holes, no?

Andrew R Stewart 

The real issue is the cables rubbing on the bare frame. I suggest some liner sleeve and if possible a second larger tube sleeve over that. Don't worry about the cable routing holes still having a lot of openness. Andy

rosefarts

I think a little plastic sleeve would increase cable life.

If you really want to go nice, cut some copper tubes that diameter and bend them to perfectly match the curve of the frame. I think a 1" long tube would do it.

urbanknight

Thanks. I was going to see if some housing fits in the hole, but was wondering if anybody knew what was meant to be there in the first place. It's a Raleigh Pursuit tandem FWIW.

easyupbug 

The kinetic (sliding) friction coefficient for dry or lubed copper and your cable is high just like for the a steel or aluminum frame and your cable, the plastic liner sleeve is very helpful.

sweeks

The cables seem to be making a pretty sharp bend as they pass through the frame. These small-radius bends don't bode well for cable life, I would think. Considering it's a Raleigh, I doubt it's designed to work like this. There is probably a missing piece.
I reserve the right to be wrong.

EDIT: Looking at all the bottom-bracket cable guides (Sample), one sees that they all have a radius of curvature that is close to that of the BB shell. It seems very unlikely that a reputable manufacturer would design a cable routing with such small-radius bends in the cable. There must be a missing piece.

rosefarts

My old Voodoo has some some cable hole/guides. Different part of the frame but same effect.

As I alluded to in the previous post, I used a short piece of copper tube to run through it. There is a piece of plastic liner around the cable in the same spot. The friction is basically non existent and the cable isn't sawing into the frame or getting prematurely worn.

The "repair" cost a few cents and took a few minutes.

HillRider

I wonder if the third unused hole in the center of the guide is intended for a cable operated drum rear brake.

Andrew R Stewart 

When I replied I initially asked if this was a Santana tandem. But then thought better of my often faulty recall so nixed that and went with the pure answer. I have seen this treatment on the captain's BB shell before. Where I'm not sure. Andy

drlogik 

Doesn't look right to me either. I see some options:

1. Use a small round chainsaw file and lightly round the front and rear edges and keep it lubed with Moly grease
2. Find some Delrin plastic tubes that fit inside the holes, cut them to be a little longer that the holes and lube with Teflon grease
3. Call an old bike shop, that is a long-time Raleigh dealer, and ask them how that bike was set up down there and maybe find the right part.

I agree that adding another metal part to go inside those holes may not help at all and it could corrode in place through galvanic action and you might never get them out.

sweeks

Here is the missing part!


From the Escher Cycle Werks. ;-)

HillRider

Did you draw that on your Echer-sketch?

Davet

I see what you did there!


very good!

WizardOfBoz

I'm trying to figure out what the two red protrusions are. Socket-headed cap screws? If so, do they effectively function to clamp somethingin those holes? Seems like overkill.

You might buy some Teflon(R) lined brake noodles if they fit in the holes. Cut them to fit, make sure that the cut ends are filed smooth. This would give you a rigid guide (to avoid the sharp angles) as well as the low-friction liner (to, well, to give you low friction).

This does seem like a somewhat questionable design. But it can be made to work.

There's pics of a Raleigh pursuit (link below) and it only has two cables as well. Dont know what the third holes is for.

https://classifieds.ksl.com/listing/62181827

woodcraft

Screws clamping eccentric BB is my guess.

Andrew R Stewart 

Yes, the bolts are to secure an eccentric BB in place. Hence my wondering if it's from a Santana. Their welds, in their Al frames, were very similar looking too. Andy

freeranger

Would the skinny part of a noodle for a v-brake fit in there? If yes, would the cables go thru the liner for a v-brake noodle. If it works, could solve the problem.

urbanknight

Yes, the two bolts are for the eccentric bottom bracket shell (to adjust the timing chain tension).

I grabbed some cable housing that was sitting around, and it fits in there. Maybe one layer of tape around it and it would fit snugly, so I'm thinking of just doing that with the housing sticking out a few mm to soften the curve.
That means a noodle should fit just fine, but would be very loose and might come out of place when the cable moves or momentarily loses tension.

urbanknight

Found a pic of the bottom of the bike (I think) and I can't see anything in there.

hokiefyd 

That's interesting -- the picture just posted seems to depict much larger/darker cables than typical for shift or brake cables. I wouldn't think a typical shift or brake cable would be near that visible in a photograph like that.

This website shows a Raleigh tandem with cable stops about 5" north of the bottom bracket on the down tube, with cable housing passing down past the bottom bracket. I don't suppose there are similarly-positioned cable stops on the subject bike, or evidence of them being there at one time? If cable housing did pass through those bottom bracket holes, you could procure several clamp-on cable stops (Origin8 makes two-holed ones that would work) to add them to the frame if desired.

JoeTBM 

I think that is liner the cable is passing through, not bare cable

sweeks

Now *that* makes sense. Those holes in the BB look the right size for cable housing, and the cable stops (braze-on or bolt-on) would allow for the cables to pass through the BB with appropriate curvature. The sharp bends in the cables shown in the images above would probably not allow proper shifting, and even if they did, not for long.