CaptainHaddock

Alright, so I'm looking to tinker with the tandem and starting with my newly developed slack in the timing chain. I've read up on the two forms of Cannondale eccentrics (one or two wedge systems) and what (in theory) you are supposed to do to adjust them. Yet I find myself unable to loosen the EBB within the shell (and am unwilling to take a hammer to it). Do you fine folks have suggestions on where I should go next?

thanks,

-J.

Chris_W

The hammer was the only option on the two Cannondale EBBs that I worked on.

PMK

Captain, I am not sure on the new style eccentric but the older ones did require me to loosen the bolts several turns and then unseat the eccentric by using a pin punch around 1/8" and setting it into the bolt head, than using the hammer to drive the wedge back.

FWIW, someone is modding those eccentrics on the newer Cannondales so they work better, it's one of the tandem shops. Might be worth checking into.

Then again, considering you wanted to drop some weight. In comparison, I swapped out our original Co-Motion eccentric, for a Bushnell. Was considerably lighter, works as a Cadillac should and is adjusted with just an allen hex wrench. Possibly a worthy upgrade and they should be almost local to you at https://www.rodcycle.com/index.html. Check other stuff they make, the featherlight EBB.

PK

WheelsNT

Please, no hammering!!!!!

Full instructions here: https://hobbes.ucsd.edu/tandem/Maintenance.faq

Here's the section from the above link on loosening the EBB:

2) Loosening the wedge.

(If you are going to be overhauling the bottom bracket, remove the crank arms
and the cartridge first.)

The Cannondale uses an expending wedge eccentric, similar in design to a handle
bar stem. The bottom bracket shell is a featureless aluminum cylinder. The
bottom bracket axle is mounted in a aluminum rod whose outside diameter is
slightly less then the inside diameter of the shell. The axle is mounted
off-center ("eccentricly"), so that rotating the holder (the "eccentric") moves
the axle fore-and-aft (and slightly up and down). A diagonal cut is made
through the cylinder, producing a wedge shaped piece. A nut is mounted in the
wedge, and a countersunk hole is drilled through the eccentric from one end
through to the wedge. A bolt is inserted into the hole and threaded into the
wedge nut. When the bolt is tightened, the wedge is pulled into the bottom
bracket shell, causing the effective diameter of the eccentric to increase,
wedging it into the shell.

The common and wrong way to loosen the wedge is to back the bolt out so that
the head is exposed, and pound on it with a hammer.

To loosen the wedge the right way, you need a short bolt with the same
threading as the wedge bolt and a stack of a couple of washers, of increasing
sizes. The bolt, with the stack of washers, is inserted into the eccentric from
the wrong side, i.e., into the big end of the wedge (on the right side of
tandem), and threaded into the wedge nut. The largest washer should be large
enough to bridge across the large end of the wedge from the bottom bracket
shell to the eccentric. Now, when this bolt is tightened, it gently pulls the
wedge free. When the wedge is free, remove the bolt and washers, and put them
in your on-bike tool bag.

The next step is to show this to your local bike shop mechanic, so that he
stops pounding on frames with a hammer.

EDIT: I see that those are instructions for the old "single wedge" cannondale design. The newer ones are the "double wedge". I'd guess the instructions would still work to get one of the wedges loose (the one on the opposite side of the bolt head), but I've never worked on one of those, so I can't tell you how to proceed from there. Others on this forum will know better...

Bostic

When I was swapping from the stock 172.5mm Gossamer to 170mm SL-K Captain cranks, I had the shop (Crank 2 Tandems) replace the EBB with a Bushnell. I didn't want to have to deal with the Cannondale model since its had negative reviews.

specbill

I love the current generation C'dale BUT..it has the worst EBB ever. I recommend the first time that anyone loosens that ebb it to replace or modify it immediately, because if you don't, sooner or later that sorry little "c clip" will pop out of its groove and self destruct. Without the "c clip' being perfectly seated you will be unable to release the eccentric as intended.

Modifying that one is quite easy if you have some fabrication skills...otherwise there are plenty of replacement choices at places like Tandems East. Mel has a lot of ebb's there along with a good picture or a modified version of the problematic one you are now dealing with.

https://www.tandemseast.com/parts/brackets.html

Bill J.

Bent In El Paso

Is the Bushnell eccentric easier to adjust than the standard Co-Motion eccentric. While the Co-Mo works great, I don't like having to loosen and tighten 4 bolts. While on the bike stand, I don't really mind. My concern is that I may have to make an adjustment on the road sometime, and it will not be an easy thing to do.

TandemGeek

Easier than the 4-screw Co-Motion eccentric? Probably not, but I like the Bushnell just the same.

The Bushnell has only one threaded "bolt", but you need a torque wrench to get it tight enough to keep them from being the source of creaking, but not too tight as that could lead to stripping some threads on the wedges that ride on the threaded shaft and secure the eccentric. There's also a little learning curve to using the Bushnell, in that when you first try to remove one you'll think you've loosened the bolt and the eccentric should now rotate. However, in fact you've only loosened one of the two wedges inside the eccentric and you will need to keep turning the bolt a little more before the other one will start to offer resistance. Once both wedges have been backed out of their recesses, the eccentric will rotate.

I'd also venture a guess that you turn the Bushnell's screw 4-times as many times as you do the four screws combined on the Co-Motion eccentric to secure and loosen the thing.

Again, I like the Bushnell and have them on all 3 tandems & the triplet, going so far as to have the OEM bottom bracket shell on our Calfee modified to accept the Bushnell. Great design, made better by Todd Shusterman a few years back. But, not necessarily "easier" to use than the 4-screw Co-Motion model.

DASTandem

Capt Haddock

I have the same Cannondale. A RT2 I bought in Oct 2011. For me, the eccentric was easy to adjust. What you have to watch out for is the fact that as you loosen it, you'll get some resistance and think you're done, but you need to keep loosening and then you will be able to see the wedge moving. Once the bolt comes out, you can use a hex wrench in one of the two holes on either side of the eccentric bolt to move the EBB in its shell.

I also have a 1995 Cannondale, and in that case I needed to use the trick outlined by WheelsNT above.

CaptainHaddock

Ok, so here's what I figured out.
1) My RT2 has the double wedge system as described here.
2) after talking to two differing LBS' the overriding consensus was to remove the captain cranks and then try loosening the EBB.

The cranks are FSA gossamer and are held in pace by way of a self-extracting bolt so that was easy enough to remove. Once I was able to remove the cranks, I was able to view that in fact while the right hand wedge had loosened the left hand side had not and necessitated further rotation of the bolt. At that point I was then able to take my 5mm wrench and adjust the location of the EBB within the shell.

Thanks for the input everyone!