Best way to arrange 2-cog manual shifting for "single speed" disc braked bicycle

[Patrick Moore]

Thinking out loud; help me clarify my thoughts.

I think of devising a Monocog replacement, with 622X76/29X3" wheels, but instead of a mono cog, with a duo cog. This hypothetical bike would have disc brakes. I don't want to use a chain tensioner, and I prefer to take advantage of the greater gear ratio differences between cogs of different sizes compared to rings with the same tooth differences, and of the consequent smaller axle movement required to adjust chain slack, so the multiple cogs would be in the back and not on the crank.

On my beloved 1999 Joe Starck Riv Road Custom fixie I use a 17/19 Dingle on a Phil hub with a QR axle; it's very easy to stop, flip the QR lever, move the chain, align the wheel, and tighten the QR.

That's what I imagine for the Monocog replacement.

1. Disc brakes. But this bike would have disc brakes. I'd probably not need more than a 2-t cog difference, but will your typical caliper/rotor setup accept the 1/4" axle movement? (1/8" of axle movement is required -- so they say; I've never measured it and take it on faith -- to accomodate a 1 tooth sprocket difference.)

2. Two cogs. How to get 2 cogs onto a suitable "ss" hub with a freewheel. The DIngle isn't made anymore and in any event wasn't made -- am I right? -- with 2-teeth gaps. The Monocog has a freehub designed to take 1 single Shimano-spline-type cog; there's no room for a second cog. >>>What options does one have to get 2 cogs with a 2-tooth difference onto a hub suitable for a QR axle?

I realize that I could just use an old 7 speed Shimano freehub, and I might end up doing that, but I'd prefer to have a hub that does not require a wide stack of spacers.

3. Axle type and dropouts/trackends/thru-axle holes. I know that long forward-facing horizontal dropouts, a QR axle, and a hub with 2 cogs on 1 side allows very easy manual shifting, as this sort of shifting goes. I am also pretty sure that a good builder can use 135 mm OL spacing and still give me the stay clearance I need for true 3" tires, so I'm inclined to stick with this very old-fashioned wheel attachment method.

But if there are other wheel attachment methods that allow you to easily move the chain from one cog to another, I'd be interested to learn about them. Sliding dropouts?

Are there any other things to consider ?

Thanks, Patrick Moore, who had a nice ride to church and back today on a pretty Fall day riding the Monocog with 72 mm tires and a single 65" gear despite the bosque trail sand and the rear tire knobs occasionally "whisping" on the chainstays (I fixed seatstay clearance with a hammer). The Silca Impero with Campy head and the Road-style BB7s pulled by non-aero DC levers are ironic but in fact work very well. When braking from the hoods you simply pull from a bit lower down on the lever; and the Impero's fat barrel moves lots of air fast into low pressure tires; 13 psi this morning and it could have been lower.
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Patrick Moore

Alburquerque, Nuevo Mexico, Etats Unis d'Amerique, Orbis Terrarum

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[Patrick Moore]

I mean, the DOS fw is not made anymore and in any event wasn't made -- am I right? -- with 2-teeth gaps. (The Dingle isn't either, but I have a stash.)

On Sun, Oct 15, 2023 at 4:11 PM Patrick Moore <bert...@gmail.com> wrote:

...  The DIngle isn't made anymore and in any event wasn't made -- am I right? -- with 2-teeth gaps.

[Eric Daume]

The simplest solution is to also use two chainrings, matching the cog difference (for instance, with a 16/18 Dos freewheel, use 42 and 44t chainrings). Then the 44/16 and 42/18 have the same chain length, and the rotor to pad relationship doesn't change.

Or just use a disc front and a rim brake rear, and a forward facing horizontal dropout (like typical UJBs have)

Eric

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[Patrick Moore]

Thanks, but I don't want that complication. I want (if I can get it) the simplicity of my Riv customer gofast: QR rear hub, Dingle cog, long horizontal dropouts. I don't necessarily need these means but I do want the same end.

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[DavidP]

Patrick, I hope I am understanding what you are looking for, but the DOS freewheels are still made in the two tooth differential versions; it's only the three tooth differential version (16/19) that was discontinued.

I'm not sure if you are looking for DOS freewheels in this situation though as these are thread on and not splined

If you are looking at a different wheelset on this hypothetical bike and a standard single speed threaded hub then the DOS will work:

https://www.whiteind.com/product/double-freewheels

Regarding disc brakes, to Eric's point I know of no way to have the quick change of gearing you are looking for with non constant chain length and a rear disc. Most single speed disc options that carry the disc with the wheel use sliding or swinging dropouts but these are not really something you want to be adjusting on the fly.

A double chainring setup really is the simplest. It's a quick change and adds a few seconds to the process.

If you adopt a constant chain length dual ring/cog setup, sliding dropouts (or an EBB) make the change even quicker as you just drop the wheel, swap the cog/ring and reinsert.

-Dave

[Patrick Moore]

Thanks, Dave, good to know about the DOX 2-tooth gap fws.

Back to the question of disc brake and axle movement: the chain length will remain the same; the axle will have to move to accommodate different size cogs since I don't want a tensioner.* This of course assumes that one is using horizontal dropouts or track ends; I'd like to stay with that assumption until it is entirely and definitely ruled out.

When moving the chain from a 17 to to a 19 t cog and v/v the axle should have to move only 1/4" or ~6 mm. This movement would be back to front and v/v. 

The rear caliper on the Monocog is  mounted above the rotor (actually, it seems to be a wee bit forward of the rotor centerline). Couldn't you mount the caliper at top dead center of the rotor? And if so mounted, the rotor would move only ~3 mm forward or back for a 2-tooth axle shift.

Could the caliper not accommodate a 1/8" or 3 mm movement fore and aft? If I have to specify a particular disc brake, let's just say a cable operated BB7.

I'll think more about the 2 rings/2 cogs arrangement. I could use, say, a 36X17 and 34 X 19 for 65" and 55". And certainly, a vertical dropout would be much easier to use for manual chain shifting than track ends.

Or one could use a kickback hub: 32 X 21 for a 46" gear in direct, 64" in 138% overdrive. 

All in all, I think I prefer the QR and horizontal dropout system, and if disc brakes can't accomodate this then I'll stick to a single speed. [Or, I could go back to a fixed off road bike where I wouldn't need a rear brake; but I rather think I want a freewheel.

*The reason might sound silly but it's a valid one: One reason I took the Monocog in trade was to have a snow bike. We very rarely get enough snow to ride in but we do get a few days per year and I like riding in it. A few years ago I found that wet gummy snow clogged the cassette and rear derailleur of my Matthews and made the chain skip. Thus the thought of getting a snow/sand single speed with 3" tires.

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[DavidP]

Yes, chain length remains the same in all cases - I guess what I meant to say was 'rear center' (distance between bottom bracket and axle).

It's entirely possible a rear disc might work well enough over that ~3mm range. I've never owned a disc braked bike with horizontal dropouts allowing the axle to move independent of the caliper so I'm not sure about the tolerances in setup.

[Wesley]

When I was using a monocog 29er as my winter bike, I had a triple speed: three cogs, three chainrings (the third, lowest gear was used for maximum torque to drive through deep snow without bogging down) . All three combos added up to the same total teeth but the change in angles was enough that I usually had to adjust the wheel in the dropout when changing gears. It worked fine with the disc brakes.

-W

[Coal Bee Rye Anne]

I have no personal experience with single speed disc nor Rocker/Slider or any of the existing dropout configurations being discussed other than keeping a mental catalogue and casual interest of such things as I discover them... but what about telescoping chainstays?   

I recall seeing a few interesting options including a build that Rick Hunter did with a bottom bracket positioned wingnut to adjust chain tension with a form of telescoping chainstay (I forget what that particular bike or design was referred to but I think it had a rigid fork, 26+ tires, disc brakes, upright riser Hunter bars, and a cow pattern custom frame bag... in case that helps ID it or dig something up for further review from the interwebs!)  

Another is the design currently used by Cjell Mone of Mone Bikes referred to as the Mone Changer.  I couldn't find an actual page discussing or highlighting the chainstay design itself but believe he builds them into various frames as requested.  Here's a snippet from the FAQ page on his site.

How do I work them Monē Changer dropouts?

 - Remember, there are 5 (not 4, don't forget the caliper adaptor ones) bolts to loosen. To lengthen, sit on the saddle and hold the rear brake, give a couple gentle bounces...that should do it. To shorten, get your chain started on your single speed cog and chainring and pedal it around. straighten the tire in the chainstays and tighten 6 bolts. If you're running gears your penance is putting the bike in the stand, throwing a foot on the BB and pulling the rim to the front.

Since you are going the custom route for this hypothetical bike I figured I'd add these possibilities to the mix : )

[Coal Bee Rye Anne]

Ooh, a deeper look through the Mone website I just found a good example and a readymade XL frame that I wish I could just add to my stable right now as a SS and multigeared drop bar bike that currently has a Paul WORD disc hub with the same telescoping chainstays.  Look through the photo album and there's a good view of the rear with Paul SS hub and WI ENO Freewheel which could easily be changed to a DOS ENO:

http://www.monebikes.com/store/hvepkoczf2qa03o3ndxq5dpuffgv6a

[Patrick Moore]

That's interesting, and after blundering into a few search result pages about money markets and currency conversion I got:

http://www.monebikes.com/read-me/

But he says nothing about adjustable chainstays,

Still, he does talk about weird possibilities like 3" tires and drop bars, so I must investigate.

Really, though, to conclude this question, it seems that I can either have a very simple bike with disc brakes as long as it's a single speed, or I can accommodate 2 cogs using some niche, complex technology. I think I'll either settle for a fixed drivetrain (no rear brake, no problem) or get off and walk. Rear rim brake not option since I want to use disc rims.

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[Bill Lindsay]

Sounds like Patrick Moore is ditching his idea.  That's a bummer.  I was hoping he would eventually pay an expert fabricator to build him a disc brake two speed 2024 version of the Campagnolo Cambio Corsa.  One QR lever and two small step gears, shiftable while riding!   I wonder if anyone would take up that job.  Numerous photos exist, so there's stuff to copy.  There would only be a few truly custom fabricated bits.  Let's say if Patrick Moore offered a fabricator $20k, would they take it on?  Or just stick to more normal stuff?

On the MUCH more expensive side, what about a 2024 re-enactment of a two-speed IGH?  The "technology" exists in kickback hubs.  Copy that tech, and insert that into a disc brake hubshell, and bob's your uncle.  Put Rohloff on a quarter-million retainer and see what they can do for you?  

Pity if none of these get pursued...

Bill "not my money" Lindsay

El Cerrito, CA

[Patrick Moore]

Reinventing anachronistic technology at 100X the price. Wish I could afford it!

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[Wesley]

Hey Patrick,

My recollection of my monocog was that the freehub had room for three cogs. I think there were spacers on the hub that covered up most of the free hub - remove the locking and you can do adjust the spacers as necessary. If yours is the same, then you could just keep that wheel and put the additional cogs onto it.

And, in case I wasn't clear in my earlier response, I think there is plenty of adjustment room in the disc brakes to accommodate the rear axle being adjusted in the dropout.

-Wes

On Tuesday, October 17, 2023 at 10:44:19 AM UTC-7 Patrick Moore wrote:

[Patrick Moore]

Not mine, said by seller to be a 2012 model. I have a 5 mm spacer, then the 3/32" cog, and then the lockring threads.

Good to know that the caliper (again, list, almost vertically atop the rotor at top dead center, but actually offset a cm or two forward) can accommodate a bit of fore/aft axle movement.

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[Wesley]

Ah. Can you not remove the 5mm spacer? That should be enough room for a second cog, IMO.

-W

[Patrick Moore]

I could indeed get a second cog into the place of the spacer but .... there'd be no room for the chain.

No, good thought, but you'd need 5 mm more of space for: big cog + spacer + small cog; then lockring. As it is, the big cog and small cog would have to butt up against each other; no room for chain.

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[Bill Lindsay]

Patrick Moore claims to have a 5mm spacer + a 3/32" cog on a hub.  Assuming his story is accurate, that's a stack up of 7.38mm

Wesley said "put another cog on there", to which Patrick Moore said there would be no room for the chain.  

8-speed Shimano cassette cogs are 1.8mm thick, and the right spacer between Shimano 8-speed cassette cogs is 3.0mm in thickness.  So, if your stack up was COG+SPACER+COG then that would add up to 1.8mm + 3.0mm + 1.8mm = 6.6mm.  That's a shorter stack up than what you have, and would have a spacing between cogs that you know works.  What's the problem?  Would the "inner" cog run up against the spokes or something?  It sounds to me like you have ample room to try two cogs plus a spacer and see what you think.  You frequently describe your box full of all generations of 7, 8, 9, 10 speed cassette cogs and spacers.  Give it a go!

Bill Lindsay

El Cerrito, CA

[Patrick Moore]

Sorry, not 5 mm, the usual ~2mm Shimano spacer. Actually I think it's a 9 speed spacer.

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[Bill Lindsay]

The updated numbers now corroborate the qualitative claim that it won't fit.  So, have you ordered your new Paul Disc WORD hub yet?

Bill Lindsay

El Cerrito, CA

[JohnS]

Hello Patrick,

Did anyone mention the All City Nature Box 853 SSCX disk brake bike? The rear disk brake mount is slotted to allow for alignment. No idea how easy that would be to adjust on the fly.

JohnS

[Patrick Moore]

Thanks, John. I'd not seen that before.

Funny, the Monocog has track ends with considerable room for axle movement but it has the old fashioned caliper mounts with no such adjustment. Perhaps that answers my question as two whether the caliper could accommodate 1/4" of axle movement.

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[Patrick Moore]

Wesley: Sorry, I missed this post in the thread volume.

I'm pretty sure that my Monocog's freehub body takes only 1 cog; see photo with single 3/32" cog and 2.5mm spacer: the splines end right after the spacer.

Am I looking at things right? I hesitate to remove the wheel because getting the tire exactly centered in the chainstays, with 2-3 mm clearance a side and the inevitable tire runout, while also adjusting chain tension is a pain.

On Tue, Oct 17, 2023 at 3:56 PM Wesley <brooks...@gmail.com> wrote:

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[Wesley]

Yeah, it looks marginal to get a second cog in there with a narrower spacer. According to Sheldon Brown, 9-speed cogs want a 2.54 mm spacer between the cogs: https://sheldonbrown.com/cribsheet-spacing.html

I now remember that my monocog became a three speed after I built it a pair of winter wheels (I used a pair of very wide unicycle rims for maximum float). So I probably kept the original when intact and built a new hub into the new wheel. Sorry for not remembering, the bike has been out of my life for about eight years.

-W

[Patrick Moore]

Do you recall the hub you used with the unicycle rim? I seem to recall BMX freehubs that had room for 2 cogs.

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[Wesley]

Hi Patrick!

I don't remember the hub, and I searched my email for hubs I bought in 2009 – I was only able to find the one I built into the front wheel. However! This exercise show something loose in my head and I now recall how I made the monocog into a two-speed (before whatever I did to add a third cog). I replaced the locking by a fixed-gear cog. Here's a text diagram:

Your current setup has: spokes - spacer - splined cog - lockring

Change it to: spokes - splined cog - spacer - threaded cog

I hope this helps!

-Wes

[Patrick Moore]

Excellent! Thank you! So there is serendipity in that the lockring threads match standard fw threads. Very good to know.

Now I can simply overhaul that cheap ss freehub -- Redline? -- and don't have to spend $$$ for a DOS; also I can use the current 32 t ring with an outer, screw-on 15 t cog for a 65" cruising gear and buy a splined ss 17 or perhaps even 18 t cog for a 57" or even 54" sand bogging gear -- if, that is, a QR disc rear wheel allows this.

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[Patrick Moore]

Messing around online I discovered that Shimano offers 3 speed hubs with rotor mounts and 135mm OL spacing -- interesting possibility. 32 x 20 with 30 1/2" wheel -- actual current measurement -- gives 49" direct, 65" overdrive and 37" underdrive (I am assuming Shimano uses the same ratios as the AW). 

I find AW ratios awkward for road gearing but these ratios are pretty useful for my flat, sandy bodsque riding.

[Patrick Moore]

Oh! And at least 2 studies have shown that 3 speed hubs (well, at least those tested, but I assume all use the same simple, basic 1-epicycle design -- because: why not?) are not only no less efficient than derailleur ones but ever so slightly more efficient -- in the 0.0n range. And you can retrofit an oil port to a modern 3 speed 'IGH ...

On Fri, Nov 24, 2023 at 7:13 PM Patrick Moore <bert...@gmail.com> wrote:

Messing around online I discovered that Shimano offers 3 speed hubs with rotor mounts and 135mm OL spacing -- interesting possibility. 32 x 20 with 30 1/2" wheel -- actual current measurement -- gives 49" direct, 65" overdrive and 37" underdrive (I am assuming Shimano uses the same ratios as the AW). 

I find AW ratios awkward for road gearing but these ratios are pretty useful for my flat, sandy bodsque riding.

[Patrick Moore]

Shimano: direct, x 1.364 and x .733, SA CS RK3 has 1.0, 1.33, 0.75.

On Fri, Nov 24, 2023 at 7:13 PM Patrick Moore <bert...@gmail.com> wrote:

Messing around online I discovered that Shimano offers 3 speed hubs with rotor mounts and 135mm OL spacing -- interesting possibility. 32 x 20 with 30 1/2" wheel -- actual current measurement -- gives 49" direct, 65" overdrive and 37" underdrive (I am assuming Shimano uses the same ratios as the AW). 

I find AW ratios awkward for road gearing but these ratios are pretty useful for my flat, sandy bodsque riding.

[Wesley]

Hey Patrick,

Maybe you've already completed your two-speed conversion, but if not, there is some useful info in yesterday's Bikesnob blog: https://bikesnobnyc.com/2023/11/29/dingle-all-the-way/

The key message is that the Surly single-speed cogs are thicker at the base so you could use one for your second cog without needing a spacer. It should allow the lockring to fit.

-Wes

[Patrick Moore]

Thanks -- yes, I've noticed that Surly fixed cogs are thicker in the center than at the teeth. Will have to remove Monocog wheel and investigate the freehub to verify the space available.

I'd read the BSNYC blog and noted the QR used with the "rocker" dropouts; his description actually tempted me to reconsider a 2X2 with equal teeth sums, say 

32/15 and 30/17 which would give me the current 65" and a 54" deep sand or long hill gear.

We'll see. I still haven't heard from the local builder.

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[Bill Lindsay]

" I still haven't heard from the local builder"

You can defer actual action FOREVER with that disclaimer...  maybe that'll force you to think about "That Libertas". 

BL in EC

[Patrick Moore]

Procrastination is what I do best.

BUT!!! What about that 2020 IGH Matthews? I finally happened. Slowly but eventually ...

Re: LIbertas: My brother owes me some $$ to be repayed in kind; he has all sorts of kind including bike stuff that he picks up dirt cheap because he likes (very intelligent) scavenging, which I hate doing. One option is to build up the frame at least at first as a scavenge beater with parts I can find cheap; I want to try tubulars before I die and old fw tubular wheelsets often turn up cheap. The frame has an old steel Campy hs,  I've got cranks, probably bb, certainly pedals, chains galore, brakes and levers galore, saddles,derailleurs; even I think a black Logic 27.2 sp -- not sure what the frame takes; would need a freewheel if fw hub, otherwise build it (really, I need to get down to build my 2nd wheel ever) up with that S3X hub for use with either fixed cog or fw. I think that I even have a stem, but I'd need a bar. This build would be what my aunt once facetiously and disparagingly described, referring to someone's furniture, as "early available." This option has the advantage that I would feel comfortable building up the frame as-is, with tt dent and broken tt housing guide and wonderfully scuffed paint.

Or I could indulge my perfectionist compulsion and procrastinate until I collect "nice" parts, either for a period-correct retro build (unlikely) or a bastardized (but nice bastardized) mix 'n' match -- S3X with Stellacooms and Xpedo ti pedals?

Really, the Libertas would be higher on my list if (a) I didn't already have 3 bikes that ride so nicely on pavement and dirt, at least firm dirt, and (b) the nearby offroad wasn't so sandy.

As things stand, the Libertas frameset is employed as an anchor or backdrop for daydreams about different possible builds.

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