Thorn Cycles Forum
Technical => General Technical => Topic started by: Coaster on March 31, 2022, 08:25:14 pm
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Looked for a post on this, but could not find one. My2010 Raven Sports Tour has two bolts at the bottom of the bike to hold the eccentric. Mine work lose and have to be tightened regularly. Is this normal? How can it be stopped?
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We have the same set up on our Thorn tandem
The bolts need to be torqued in the 10 to 16 nm range, yours are probably not tight enough.
There was also a suggestion to put a tight rubber band around both the bolts.
Mike
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Good afternoon, in the workshop we now add blue thread lock to the bolt to help reduce the chance of them vibrating loose, most people will never have an issue, but we like to be prepared.
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One of mine came loose several years ago. I then tried blue (removable) threadlocker, but decided not to use it any more as I liked to be able to unthread it by hand once it was initially loosened.
Then I decided to use a rubber band, this is cut from an old inner tube, actually used two in case one broke, the other is the redundancy. This has worked well for me for several years, the photo is three years old and I had been doing this some time before I took the photo.
If you are curious why I want to remove a bolt easily by hand, more on that here:
http://thorncyclesforum.co.uk/index.php?topic=14475
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Since 2012, I've had stellar luck using thin M8 x 0.75 stainless "jam" nuts on my eccentric bolts.
They only have to be slightly more than finger tight to prevent any loosening of the extra-fine threaded grub screws.
Best,
Dan.
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150 inch-pounds of torque worked for my Raven's bolts.
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Thank you all. Now the drain plug has fallen out of the Rohloff and disappeared!
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150 inch-pounds of torque worked for my Raven's bolts.
Hi John
I think that works out at just under 17 nm.
They definitely are not going to come loose!
Mike
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Thank you all. Now the drain plug has fallen out of the Rohloff and disappeared!
I save all my old drain plugs when doing the oil changes for occasions like this.
When doing the oil changes I place the bike workshop stand on an old blanket so if I drop the plug it doesn't bounce high off the concrete floor and disappear.
I am sure that Thorn will sell you a couple of new ones for five quid or so!
Mike
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If you are concerned about losing an eccentric bolt, I was too, keep one in my spares for touring. I bought a spare one from SJS when I was buying some other stuff. And I have a couple spare Rohloff oil plugs too. Occasionally when working on my bike on my patio, something falls and rolls to where it falls between the grooves between the concrete blocks. A few spares of everything are useful for that work area.
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If you are concerned about losing an eccentric bolt, I was too, keep one in my spares for touring.
“Shortly after leaving Eureka, I had yet another mechanical issue. After hearing a cracking noise coming from my bottom bracket, I noticed that I had lost one of the two bolts holding the eccentric shell in place. I had foolishly forgotten to bring a spare, so I needed to order some from England. This was an exotic, finely threaded bolt I wouldn’t be able to find anyone in the USA, apparently. I had them sent to a Warm Showers host in Challis, about 10 days ride away. I would just have to deal with the annoying sound for a while. “
Quote from Tara Weir at,
https://followmargopolo.com/blog-4/
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...
“Shortly after leaving Eureka, I had yet another mechanical issue. After hearing a cracking noise coming from my bottom bracket, I noticed that I had lost one of the two bolts holding the eccentric shell in place. ...
...
To make a long story short, when I start a tour with my Rohloff bike after an airplane trip to get there, my bike is packed in the S&S case, thus fully disassembled. And before I leave home, I do the Rohloff oil rinse with cleaning oil, drain, but do not add fresh oil until I assemble the bike after a plane ride.
So, I am handling a LOT of small nuts, bolts, washers, and Rohloff drain plugs. I want to have a spare of every small part I can think of. M5 bolts, M6 bolts, eccentric bolt, Rohloff drain plug, quick chain links, washers, cables, etc.
And since I use blue (removable) threadlocker on my rack bolts, I even carry a bottle of threadlocker with my spares too.
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Thank you all. Now the drain plug has fallen out of the Rohloff and disappeared!
Not Thorn / SJS but available on ebay https://www.ebay.co.uk/itm/124097942900. Alternatively get the oil change kit which includes a new plug https://www.sjscycles.co.uk/tools/rohloff-full-oil-change-kit-8410 and add a spare plug https://www.sjscycles.co.uk/hub-spares/rohloff-screw-in-drainplug-for-speedhub-50014-8205 so they share the delivery charge.
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...This was an exotic, finely threaded bolt I wouldn’t be able to find anyone in the USA, apparently....
So! This caused a Danneaux trip to the garage in search of a suitable in-a-pinch substitute.
Found one.
Thorn's eccentric grub screws are threaded M8 x 0.75 extra-fine pitch -- the same thread as a crankset chainring bolt. I found a 1/4in ball bearing will nest against the inner shoulder of the hollow chainring bolt and will also engage the dimple left in the eccentric by the proper bolt.
While far from an ideal substitute, this could well get one by until a proper Thorn eccentric grub screw could be found. Might work well enough to quell any noise caused by having only one grub screw.
Best,
Dan.
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12.5 ft-lbs, Mike, near as I could figure to the upper limit. "Old money", I know, but that's what's on my torque wrench.
Cheers, J.
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I have only bought two torque wrenches in my life.
First one, my used Land Rover came without the receiver hitch that had been installed at the factory. Bought the new hitch, and a hitch is the kind of thing you want to make sure is installed right, so bought the half inch drive extra long torque wrench. Discovered that was a waste of money, I was unable (insufficient arm muscle) to put enough torque on the bolts. I could have skipped the wrench and just used all possible muscle without using a cheater bar. But, since I had it I started to use that when installing square taper crankset bolts after had one that was not torqued high enough.
Second torque wrench, bought a Ritchey Breakaway frame. They specifically instruct you to use a torque wrench on the coupler, max 4 Nm. Needed the tiny little torque wrench for that.
I am not going to buy a new in between torque wrench for eccentric bolts. If one is a bit loose, I will tighten it. And with the rubber bands it should mean that I will never need my spare one that I carry on tours.