Gosh that's new to me.
How's about a few details, bike, age, is this the first time you have looked at this?
Matt.

I bought the bike second-hand about two years ago. Sorry I don't know its age.
The frame is a thorn voyager like this one:https://www.sjscycles.co.uk/frames/medium-xx-small-thorn-voyager-tandem-frame-yellow/?geoc=FR.
It's the first time I look at this part of the bike.

Cedric

Hello

I would like to adjust my front chain tension but I think there is a problem with the screws.
I took two pictures from below.

Shouldn't there be a head on the screw so that I can loosen it to adjust the eccentric?

Bests

If you’re thinking about doing the Strawberry Line suggest you check out the planned closures and diversions for the next 6-8 weeks, here

https://n-somerset.gov.uk/my-services/libraries-leisure-open-spaces/parks-countryside/parks-open-spaces/strawberry-line-heritage-trail/strawberry-line-temporary-closure

New one to me.

https://manualzz.com/doc/25836591/rohloff-hub-user-manual?ct=2de541614f263223%3A4f2a6dd8b02804a3fc2fdec7691641&utm_campaign=captcha_passed

Lots of helpful stuff here people, thanks. Also lots of different approaches.

I'm in sympathy with PH on the maintenance. People with no experience don't realise how fast it gets bad – if you're a long way from home and have a simple breakdown that nevertheless you can't fix with what is on hand. On the sort of rides I do it won't be life-threatening, but even 20km is a long way to walk. Pushing a loaded bike with a broken wheel, a very, very long way.

That's one of the things I really like about having my Thorn and the Rohloff. The Thorns are beautifully built and while the Rohloff would strand you if it did develop a fault, from all accounts that's less likely than snapping off a derailleur mount. I know I'm tempting the fates with that statement, but I reckon they'll leave me alone. (Touches wood for good luck.)