Intrigued by this double chainring concept...
 

https://www.cxmagazine.com/gravel-bi...ost-found-2018

This intrigues me, for my own Surly Cross Check singlespeed (freewheel). Looks like an interesting experiment. Could be nifty to be able to gear down just a little like that, and just reposition the wheel in the sliding dropouts. What would I need to consider when mounting the extra smaller ring--I assume you need some kind of spacers? Obviously the chain line will suffer a little--how big a deal would that be?
Alternatively, could you mount two sprockets to the rear cog?

EDIT: just found this: https://wabicycles.com/collections/c...ixed-cog-18-16
Looking to see if there's a freewheel variety...

To the chainline issue: "The most interesting part of Barre’s Cross Check singlespeed is its drivetrain. Barre mounted two chain rings to the alloy crankset, and the rear wheel’s flip hub had two cogs mounted to the fixed side, implying the Barre adjusts his gearing based on the ride."

Seems unnecessarily complicated to me-- it's effectively the slowest shifting 2-speed drivetrain possible. If you want more gears, get a 3-speed hub. Easy.

I have been riding and fooling around bikes forever and never even remotely day dreamed of a set up like this > in pre covid days it would get you into a lot of curbside conversations

https://www.sheldonbrown.com/org/quickbeam-index.html

Sheldon Brown had a bike with 40/33 chainrings. Then a 2 speed 16/18t White Industries freewheel on one side and a 14t fixed cog on the other. Very cool set up.

It just seems kinda nifty, for example, I take my ss on family camping trips to tool round on when it's not a trip that requires my geared bike. But sometimes you discover your destination is a lot "climbier" than you thought:). Would be cool to just swap it over like that.

I think what appeals to me is that, with either chainring, you're still riding a singlespeed, with all that entails.

This is very cool indeed...

Well lo and behold: https://www.benscycle.com/White-Indu...iABEgLvQvD_BwE

Why not just build a wheel with an alloy rim and a 3-speed internal gear hub? With that you don't have to stop to change gears.

Cheers

You're missing my point. As I say, what intrigues me about this is, you're still singlespeeding when you're riding. The simplicity and purity (and yes, the limitation) of it is still there. It's just easier than replacing a rear cog to change up your gearing relatively quickly for different situations.

I love riding fix gear, I love riding hills. I'm in my 60s and have had chronic knee issues the past 40 years. 9 years ago I had a custom fix gear built that had a road style dropout but long enough to run any 1/8" cog I've ever heard of. (I now have from 12 to 24.) I've ridden 5 Cycle Oregons on it using a fix-fix flip-flop wheel and carrying a chainwhip.

Three years ago I set my Mooney up to ride the (canceled) Cycle Oregon with its promised 30 miles of gravel. But how to do the gears on a standard late '70s Campy horizontal dropout? Geeky engineer here. Multiple chainlines. I went with three. Made up a rather custom 110 BCD triple pushed as far in as a 38 tooth ring would allow. Had a "dingle" made using a 21 tooth cog as the core, flipping the 21 so the cog sits flush with the hub and cutting out the center of a 17 tooth and braising it to the 21 with a steel spacer. Dished a flip-flop wheel in a touch for the dingle. That kicked out the small cog a touch.

End result? I run a crankset of 46-42-38. Using a 13 tooth small cog gives me a 46-13 (96:) high, 42-17 (67") level ground and a 38-21 (49") low. I can also swap out the dingle and screw on a 24 for a 43" low (very low for a fix gear on pavement) if I carry the chainwhip. All three cogs like up near perfectly with their respective chainwheel. Everything is rock solid 1/8". (A shout out for Izumi chains. $25 gets you a really good one. Lots of pin extension so driving and re-driving pins is easy and safe to do. No, not the quietest. Quiet and sweet shifting are closely related, I NEVER want to shift until I stop and pull the wrench out. EVER. So noisy Izumi chains and EurAsian cogs are up my alley. And EurAsian cogs, despite the name are made in the US.)

Yes, on both bikes, changing gears costs my a couple of minutes. Unscrewing cogs about 5. But - this is all fix gear. I ride it to get away from freewheels. Yes, fix gear internal hubs exist but I have never heard that they were up to hard riding. My Mooney has a drive train close to velodrome worthy in all three (very different) gears and the custom, with its Sugino 75 crankset, is fully velodrome worthy, just not a track bike at all.

Ben

You're still single-speeding with a 3-speed hub too but it's much easier faster to get into a lower gear than it is to stop, and change the gear as the setup you talk about requires. That's almost as bad as in the days of yore when a bicyclist stopped at the bottom of a hill and then flipped their rear wheel to get at the samller cog.

Whatever floats your boat I guess. After all I have a 9-speed 11-19 teeth corncob on one of my MTBs. :lol:

Cheers

I'm building that very sort of thing right now. SS, not FG. There's a thread about it here: https://www.bikeforums.net/singlespe...-retrofit.html

Basically two chainrings and two cogs, that take the same chain. Both are magic gear ratios. No derailers or tensioners. It's called a dinglespeed. A bit easier than a flip flop because you don't have to remove and flip the wheel. Just loosen the QR unseat the wheel, move the chain, and reseat and set the QR.

36:15
http://i.imgur.com/YL7L7B5l.jpg

24:28
http://i.imgur.com/gHLTgUSl.jpg

Wow, what a cool project bike! Nicely done.

Thanks, I'm very happy with the final look of the frame and am just letting it cure a bit before putting the bike back together.

What would be really cool is if they came up with some kind of derailing mechanism that could shift the chain while you're riding.

pssh HTFU and just reach down with your hand and grab and pull while pedaling.

[QUOTE=Happy Feet;21573624]I'm building that very sort of thing right now. SS, not FG. There's a thread about it here: https://www.bikeforums.net/singlespe...-retrofit.html

If you don't have it already, seriously consider carrying a Pedros Trixie fix gear wrench. Makes the chain swap very easy and clean. Tool has a very good hub nut wrench so you can leave what you are using at home and the lockring spanner is perfect for picking up the chain and moving it to another cog or chainring.

If you do go to flipping wheels - another trick -a chain peg. Easy way to do that: take a 4mm screw (my faulty memory says 4mm is the near universal fender and toeclip screw) and run it into your fender eye on the dropout from the wheel side. Pan head screws work really well. Flat heads might even be better. I use a nut, also on the inside, tightened against the dropout to keep it locked in place. That way, you can tailor how far out the peg sticks. Further inboard is easier but different wheels and cogs can impact the optimum placement. Now, with the Trixie, you can just lift the chain off the cog or freewheel, drop it on your new peg, flip the wheel and put the chain back on. That's how I get my 2 minute wheel flips.

Ben

Hey, that's hilarious.. and so original too.

Fwiw, this build is for some local SS mtbing where we have great gravity flow trails but long doubletrack access climbs. You may prefer to walk up hills for 2-3 kilometers at a pop but I like the idea of being able to ride up and down.

The beauty of bicycles is that they are a technology that lends itself to being creative by home enthusiasts. I feel no need to become stuck in any sort of traditional paradigm.

[QUOTE=79pmooney;21574600]Funny about the chain peg. Intetesting diy idea. First frame I ever saw with one I was like: what the heck is that thing for?

Because the chain comes completely off of an e stay frame without breaking I'm going to experiment with waxing the chain instead of oiling. Two 8 speed chains in rotation should make that a snap and create a cleaner chain for handling.

If I did something like this I see myself sticking with whatever gear I started out in for the most part. For example, when I go out my front door, I have two choices--one way is straight up into the mountains, and the other direction is pretty flat. Right now my singlespeed is geared pretty low because of all the potential climbing. Could be cool to be able to swap my "singlespeed" gearing on the fly if I'm gonna head into town and stay in the flats all day. I can always just take my geared bike of course, but this idea seems nifty.

Once you get your main gear ratio figured out, in this case 2:1 via the 36-15 combo, you can then play around with the secondary gearing.

Combined 36-15 equals a total T count of 51T. Therefore 24-28 equals close to the same T count (52T) and should fit the same chain/dropout distance. I probably will wind up using 22-30 when I get another 22T chainring.

22-30 is a pretty low gear range and makes the dinglespeed worthwhile IMO, unlike other double cogs systems that only vary by a few T when probably I would be unlikely to bother to swap between a small variation and just crank through instead.

Ideally the change up gearing should be where it becomes too hard to crank in the preferred ratio so that the second combo extends the range of SS further.

The application doesn't really make sense for day to day urban riding but fills a niche for SSMTB or SS touring in regions with big long hills. The route from Hope to Manning Park for example, involves a 60km climb. You just can't ride that with a SS using a gear ratio that would otherwise be suited for more horizontal travel.

What kind of girly-man would use something like that? :)

Indeed--all makes sense. I was Bikecalc.com trying to figure out how I'd work it if I got one of the White Ind DOS rear cogs--they offer 16/18t, or 17/19t. I have gone up and down 1 to 2 teeth on my rear cog at times and it is for sure different, but not that big a change, not like what you describe. I'll have to figure out what to do up front....
FREEWHEEL ? White Industries

Nice!
Once you start wrapping your head around the concept all sorts of possibilities begin to materialize. A person may like riding SS or FG but find the routes they want to do make a traditional set up impossible (or problematic beyond practical). A commute that is predominantly up hill one way (and down hill on the way home) is a common problem.

If one wanted to bike tour SS from Vancouver to Calgary for example it would be virtually impossible on a one ratio bike without a lot of walking. However, two ratios make it potentially doable with long stretches between swaps.

The route from Vancouver to Hope (about 180km's) can be done with road gearing, it's mostly flat. Switch to mountain gearing for the 60km climb up to Alison Pass. Road gearing from there for a couple of hundred Km's to Penticton. Same gearing through the whole Okanagan Valley to Revelstoke, about 300km's more or less. Mountain gearing over the Rogers Pass and road gearing down to Golden and beyond. Mixed gearing from there to Field. Mountain gearing up the Kicking Horse Pass and road gearing from there for 200 Km's to Calgary.

Or, like me, one could live in the middle of five downhill MTB parks that one can ride to but that also have long access climbs. If I choose to SSmtb I can either walk up or ride up.

http://i.imgur.com/pGESxHVl.png