Rohloff questions

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531colin
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Rohloff questions

Postby 531colin » 9 May 2020, 2:37pm

I'm gathering my strength to tackle a Rohloff build, so can somebody help me with some questions please?
Rohloff specific dropout....how long is the slot?
I have a frame with 40mm long horizontal dropout slots....could I use the torque reaction arm designed for the Rohloff dropout?

Brucey
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Re: Rohloff questions

Postby Brucey » 9 May 2020, 2:58pm

'not quite' or 'only just' I think is the answer

Image

and of course even if it is long enough, you will have to run a tensioner because the wheel will only be able to sit in one place. There is also a question mark over whether the dropouts will be strong enough if they are not designed with rohloff in mind (BTW the reverse torque can be much higher than the forwards torque on the axle). You can always use an external torque reaction arm.

cheers
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cycle tramp
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Re: Rohloff questions

Postby cycle tramp » 9 May 2020, 3:58pm

If you can give me until tomorrow afternoon, I'll have a look then

KimBowers
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Re: Rohloff questions

Postby KimBowers » 9 May 2020, 4:20pm

Hi,

There is a Speedhub Finder on the Rohloff Website : https://www.rohloff.de/en/service/search/speedhub-finder/
This suggests it is possible to fit a speedhub to horizontal dropouts even shorter than 25mm :-

Speedhub Finder.png

The distance between the mounting bolts on my bike using the OEM dropout is approx 30mm.
Total length of the slider slots is approx 55mm.

PH
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Re: Rohloff questions

Postby PH » 9 May 2020, 5:16pm

Is this for your Longitude? If so I think you can use a set screw and bolt as a torque anchor point with the appropriate axle plate. It's a frame I was considering a few years ago, so did a bit of research before going for something else.
I use that system for the Rohloff on an Airnimal Joey, it makes the wheel a little fiddly to get in, but that's mainly holding the tensioner out of the way something you wouldn't need to do.

slowster
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Re: Rohloff questions

Postby slowster » 9 May 2020, 6:14pm

I would recommend reading this thread on Singletrackworld. NB It's a 5 year old thread, and I don't know if the current Longitude drop out is the same as then. One of the posters was Ben Cooper of Kinetics, who is very knowledgeable and experienced on this subject, and according to him:

The OEM dropout slot needs to be at least 35mm long – plus space for adjustment.
and
As long as the dropouts aren’t paper-thin (doubt it) then it’ll be fine with the OEM1 plate – the only ones I’ve seen spread out are the old-school track dropouts with thin lower prongs – or forward-facing slots.


NB SJS are selling off their stocks of the older pattern OEM1 axle plate for QR hubs for £2.99 each, so you could buy one relatively cheaply to measure it yourself and check there is enough room for the stub and to allow for chain stretch.

Incidentally, according to this more recent thread, the 2016 Longitude was specifically designed to accept a Rohloff OEM2 axle plate, but it seems that only applied to that particular model year. You can see the difference between the 2016 frame below in yellow and the current frame in orange: the left hand drop out of the 2016 frame has a slot which can accept a nut and bolt, and the bolt head will fit into the notch in an OEM2 axle plate, i.e. the same design as used by Surly on the Troll and Ogre frames. In the 2019 version of the frame, the slot in that position is much shorter it and does not have parallel horizontal edges.

Image

Image

Cavemud
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Re: Rohloff questions

Postby Cavemud » 9 May 2020, 6:47pm

Not sure if this helps, or even if your frame takes disc brakes:

I recently converted my wifes bike to Rohloff, and used something called a Monkey Bone disc brake adapter (available from SJS), which is basically a conventional disc brake adapter with a cutaway for the axle plate to sit around.

Works nicely.

It's worth looking at a picture of that adapter anyway, as the disc bolt is centred on the oem2 slot, so for a bike that didnt use that adapter you could just use the bolt itself.

(I hope that makes sense)

PH
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Re: Rohloff questions

Postby PH » 9 May 2020, 6:52pm

slowster wrote:the 2016 Longitude was specifically designed to accept a Rohloff OEM2 axle plate, but it seems that only applied to that particular model year.

How odd that they should take away such a useful feature for no discernible advantage (That I can see)

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531colin
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Re: Rohloff questions

Postby 531colin » 9 May 2020, 7:07pm

Slowster, thanks for that, good shout. I'll get one of those arms for next to nothing and have a play. Mine is the orange frame without the extra slot; but it might be a bit of a fiddle to get the reaction arm tab into that slot even if you had one? I guess you might have to spring the frame?
I'm pretty sure I'll be using a chain tensioner anyway; my plan was to contrive limit stop(s) in the dropout(s) so the wheel just goes straight back in with no fiddling.
I maybe could fix a bolt in a random hole in the dropout and use the OEM2 plate; using a chain tensioner frees me from needing an adjustment slot.
The official way of doing it is to use the OEM2 plate and a disc brake adapter with a stupid name (monkey bone?) and a tab for the plate...that seems to make hard work of it. Let alone moving the disc brake when you move the wheel to take up chain wear, lifes too short!

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531colin
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Re: Rohloff questions

Postby 531colin » 9 May 2020, 7:11pm

PH wrote:Is this for your Longitude? If so I think you can use a set screw and bolt as a torque anchor point with the appropriate axle plate. It's a frame I was considering a few years ago, so did a bit of research before going for something else.
I use that system for the Rohloff on an Airnimal Joey, it makes the wheel a little fiddly to get in, but that's mainly holding the tensioner out of the way something you wouldn't need to do.

Ah, I think I understand?....OEM2 plate and a bolt in a random dropout hole?

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Re: Rohloff questions

Postby PH » 9 May 2020, 7:27pm

531colin wrote:
PH wrote:Is this for your Longitude? If so I think you can use a set screw and bolt as a torque anchor point with the appropriate axle plate. It's a frame I was considering a few years ago, so did a bit of research before going for something else.
I use that system for the Rohloff on an Airnimal Joey, it makes the wheel a little fiddly to get in, but that's mainly holding the tensioner out of the way something you wouldn't need to do.

Ah, I think I understand?....OEM2 plate and a bolt in a random dropout hole?

Not that random, it was intended to go in the slot that Slowster pointed out has been removed. So that might be a dead end.
On the Airnimal with a tensioner, it's just a hole with the screw in it, the Longitude with the appropriate slot would have done away with the need for a tensioner. If you use a tensioner, then yes the OM2 plate and a bolt in the appropriate place would work, I think it's 40mm from the axle.
Last edited by PH on 9 May 2020, 7:30pm, edited 1 time in total.

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531colin
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Re: Rohloff questions

Postby 531colin » 9 May 2020, 7:28pm

Kim, I hadn't found that bit of the Rohloff website; but unfortunately they are talking about dropout length to permit chain wear adjustment rather than fitting the axle plate.

slowster
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Re: Rohloff questions

Postby slowster » 9 May 2020, 8:50pm

531Colin, I would preface the following comments by saying treat what I say with caution and don't assume I know what I am talking about. In your shoes I would be reading through that first Singletrackworld thread very carefully. Ben Cooper in particular is an expert: he makes kits to fit Rohloffs to Bromptons and has undertaken various other exotic bike projects.

531colin wrote:Mine is the orange frame without the extra slot; but it might be a bit of a fiddle to get the reaction arm tab into that slot even if you had one? I guess you might have to spring the frame?

By 'reaction arm' and 'reaction arm tab', I presume you are referring to the OEM1 Axle Plate, whereas the words reaction arm make me think of the Torque Arm. I don't mean to be pedantic, but there are so many different options with Rohloffs and odd names like Monkeybone and Speedbone, that I think there is a danger of confusion when discussing different Rohloff set ups on an internet forum, especially without the benefit of photographs.

To be clear, if the length of the drop outs is enough for an OEM1 Axle Plate and that is what you fit, then there is no need to fit a bolt somewhere on the drop out since a bolt head is only needed to provide an anchoring point for the notch on the OEM2 Axle Plate. The projecting tab on the OEM1 Axle Plate should slide without difficulty into the drop out (before* sliding the hub axle itself into the drop out) and there should be absolutely no need to spring the frame apart to accept it. The main 'fiddling' required is the usual lining up of the brake disc with the gap between the brake pads, and having at the same time to grip and rotate the Axle Plate to line up the OEM1 tab with the drop out entry (or the OEM2 notch with its anchoring bolt head) is not something which I would consider a big deal.

* EDIT - Apologies, I should have written "after sliding the hub axle itself into the drop out".

531colin wrote:I'm pretty sure I'll be using a chain tensioner anyway; my plan was to contrive limit stop(s) in the dropout(s) so the wheel just goes straight back in with no fiddling.
I maybe could fix a bolt in a random hole in the dropout and use the OEM2 plate; using a chain tensioner frees me from needing an adjustment slot.

One thing to check might be compatibility with an electric motor, which I think you are considering fitting as well at some point. Apparently Rohloff now make/sell sprockets for 1/8" chains, and I think they have been introduced specifically for Rohloff E-bikes. However, I think they don't yet make/sell a chain tensioner which accepts a 1/8" chain. If the 1/8" chain is necessary for a Rohloff E-bike to cope with the extra forces and wear and tear, that might be an issue you need to consider (although in that case I would expect them to introduce a 1/8" compatible tensioner pretty quickly).

I don't know how much they cost, but Surly Monkey Nuts (specifically the Mk2 model) might be ideal for your limit stops.

Even if you have some form of limit stops in the drop outs, if a motor is fitted I suspect you might have to use a solid nutted version Rohloff, rather than a QR version.

531colin wrote:The official way of doing it is to use the OEM2 plate and a disc brake adapter with a stupid name (monkey bone?) and a tab for the plate...that seems to make hard work of it. Let alone moving the disc brake when you move the wheel to take up chain wear, lifes too short!

I agree. Moreover, according to Ben Cooper in that STW thread, in a frame like the Longitude with rear facing horizontal drop outs the "OEM tab is sometimes at too shallow an angle for the Monkeybone", and if that is the case he has to modify the Monkeybone:
With vertical dropouts the entry path is from below the Monkeybone, so the prongs of the OEM2 plate can just slide up and over the MB. With rearwards-facing dropouts the entry path is at an angle and the OEM2 plate rotates as you slide the wheel in. So it’s perfectly solid once it’s fitted, you just can’t get the wheel in and out.
Last edited by slowster on 9 May 2020, 9:29pm, edited 1 time in total.

Brucey
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Re: Rohloff questions

Postby Brucey » 9 May 2020, 9:20pm

there's a very great danger of overcomplicating this, isn't there?

What I had assumed Colin meant was that you use one of these

Image

in a rear facing dropout. If the axle can be pulled to the front of the slot (or against spacers) for consistent positioning, and a tensioner used, it could hardly be any simpler?

As I mentioned upthread a concern in my mind is the strength of the LH dropout; it has to take a potentially very large torque reaction load in the reverse direction, and not all dropouts will be stiff/strong enough in the long run. The genesis dropout looks like it would be much improved (in terms of dealing with the torque reaction) if at least one of the cutouts were filled in.

Anyone as handy as Colin I would expect to quickly modify something to suit the frame or the frame to suit the hub.

Idea; if you want to stiffen the dropouts up without having to repaint etc, you could cut close-fitting infill pieces from (say) 1/4" aluminium plate, which is then bonded into the cutouts using epoxy resin. A few strategically placed small nuts bolts and washers would ensure that the infills also stayed put in the long run, too, even if the epoxy started to crack up after a few years.

cheers
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531colin
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Re: Rohloff questions

Postby 531colin » 10 May 2020, 9:57am

This is the dropout in question..
IMG_5108.JPG

Its over 6mm thick, but that includes paint.
The slot is (maximum) 40mm long; my original idea was to use the OEM axle plate that Brucey shows in the dropout wheel slot. (In preference to the "official" axle plate with a half-round cutout which engages with something on a modified disc brake adapter ISO/post mount.)
Its more complicated because (apart from the frame) I haven't got the stuff in my hands, and I can't go and see my pal who rides Rohloff because we are both over 70 and in lockdown.
Everybody's idea of whats a faff is different.
I'm happy to grind up some bits of metal and silver solder them in the cut-outs to stiffen the dropout against axle torque, because that's done once.
I'm happy to use a chain tensioner, because all my existing bikes have a rear mech.
I don't want to have to faff with getting the wheel position spot on for chain tension when I puncture in the rain, and I'm not moving the disc brake to suit the chain wear, its getting fixed once!
I don't even know if the axle plate/torque arm moves with the "external gear mech. kit" or if you have to wrestle them both separately while getting the wheel in the slot and the disc rotor between the pads...but if they are separate then the axle plate might be getting a handle added!
I'm not worried about breaking stuff, even though electrification is a future possibility I won't be riding it like a motor bike.