Hello again

The previous owner sent me a link to the eccentric he installed on the bike: https://funecobikes.com/product/boitier-de-pedalier-excentrique-aluminium-pour-tandem.

The part is made of aluminium and my frame is made of steel. Isn't there a risk of corrosion.

I will try to remove the screws next week and tell you.

Thanks again

Dissimilar metal corrosion can be a problem with steel and aluminum, but the metals have to be in contact for that to be a problem.

For example, aluminum seatposts can bond to steel frames.  But if you grease the seatpost, that not only solves that problem, but the grease reduces the amount of water from rain that gets inside the frame as the grease acts as a sealant.

My Nomad Mk II has paint (or powder coat or something like that) on the steel shell around the anodized aluminum eccentric, the anodizing and the paint do a good job of preventing dissimilar metal corrosion.

I do not read French, I do not know if that is anodized or not.  But if the shell on the frame has a good layer of paint, it is unlikely that it would be a problem.

My Thorn Sherpa has an aluminum seatpost that I make sure is greased, but most of my other bikes have painted (or some other material) seatposts that prevent the metal to metal contact.

As Matt has said, on our Raven Tours the bolts have pointy ends and are designed to dig into the EBB so will leave an indentation in the soft alloy.   If small rotational adjustments of the EBB are made the indentations can become a groove and the eccentric is then not correctly locked.

On mine I can remove the bolts, look down the holes with a torch, and rotate the EBB to see where the next indentation is.  I have been lucky as mine had been adjusted properly by the PO and the indentations were well spaced apart - so I have simply reused those indentations rather than make new ones.

I have found that the bolts can loosen off so mine are now drilled and lockwired (others use bands made from innertube).   I also found that after 1500 miles in one position that the bolts needed to be wound in a touch further to take out a little looseness between the EBB and frame - the downward loads from cycling had pushed the bolts deeper into the EBB.

If you get new nuts welded on make sure they are fine thread M8, not standard M8 nuts.

Edited to add:
What I have written above is relevant to a Raven, looks like the Voyager may use a slightly different system with flat ended bolts??

Hey, just to let people know that this is still available.

I've been dealing with some family matters so apologies for the silence.

Mark

I agree with Dan, likely metric.  But there are fine threaded and course threaded versions, so if you get them out undamaged, measure the diameter and the pitch.  Your mechanic friends most certainly should be able to help.

If it is M8 X 0.75, you likely need this one.  That is the same one I use on my Nomad Mk II.
https://www.sjscycles.co.uk/bottom-brackets/thorn-m8-extra-fine-conepointed-screw-for-eccentric-bottom-bracket-shell/

One thing that has not been mentioned here, if you get them out and get new bolts, you should install the eccentric so that the thick metal part is the part that the pinch bolts press against.  If you set it up so the pinch bolts press against thin metal, it may deform, thus you want to avoid that.  See attached photo of mine, the thick part of the eccentric is on the bottom where the pinch bolts are, not the thin part of the eccentric.

Thanks a lot for all yours answers. I'll try to contact the man who sold me the bike and ask him what happened.

Some colleagues of mine are mechanic, I'll have some help of that topic.

Do you think that the threading is to be metric?