Single rear cog, double crank????
 

For those of us who live in really hilly areas but want the weight of a fixed or single gear bike has anyone heard of building a single rear cog with a double crankset/front derailleur bike? I am sorry if this has already been addressed but I could not find it in the search feature.

I am a newbie here and to the idea of fixed or single gear bikes. I guess it l must be regressing to the times I learned to ride a bike, single with a coaster brake but after riding only multi speed bikes I would like to give the single rear cog a try but in the hilly area I live, I would be walking the bike uphill all day long.

In short anyone build a single rear cog bike with a double or triple crankset?

you would need something to keep chain tension..

I did this to my bike with a triple when my cassette wore out. The idea was fun but performace wasn't that great. If you do proceed with this then stick to a double crank just for better chainline. You're not going to save much weight because you the rear derailer to take up the chain slack.

You could use a single speed tensioner to hold the tension when you chain your front. You might have to fiddle with it.

how are you going to keep a straight chain line? chain will fall!

not if he keeps the RD and uses a narrow chain

It's been engineered, so its viable; I wouldn't jump to conclusions about anything in this industry.

White Industries makes this.

http://whiteind.com/images/429_156.jpg

I tried it on my '86 Moots w/ vertical dropouts. Used a Paul's tension-er, 16t 3/32" FW, and a Deore XT Compact Drive Crank, 32/44 with a cheap SRAM 8 spd. chain & XT Ft. DR.

I also used a 68 x 107mm BB to bring the crank in a bit... it worked pretty good!

Alan :thumb:

I did this back in the early 1980s with a double crank and derailleur in front, and a 3-speed hub in back, with a rear derailleur for chain tension. Worked great as a six-speed. Not bad for what was available at the time, but if I were to do it again today, it would be a straight IGH, no derailleurs.

What about a Surly Dingle or whatever?

I did this very thing recently. You can check it out here: http://forums.roadbikereview.com/fix...et-271286.html

I have a fellow who plays bike polo and has this setup. Double chainring crank (one to play bike polo other to use on the streets) and it is fine. He doesn't need a chain tensioner like the poster above btw.

Thanks to everyone for the quick replies.

I really appreciate knowing it is not hopeless but also appreciate the advice that there is more to it than simply adding a double crankset to an existing fixed gear bike. I thought I could take a Masi Speciale Fixed and add a narrow double crank and front derailleur with a shifter and climb hills here. Can only imagine the sound of the chain grinding on the frame when I went to change gears or it falling completely off. No doubt it would do that while still on the bike repair stand with the first attempted revolution.

To Aaron_F awesome job and thanks for the details. It is beyond my skillset but I can at least show some skilled bike tech what you have already accomplished and ask for something along those lines.

Fixed gear, 3 ratios, no tensioner needed:

http://www.sturmey-archer.com/userfi.../small/S3X.jpg

http://www.sturmey-archer.com/products/hubs/cid/3/id/47

So does he have a front derailleur for changing the crankset gears or does he take links or add links out of or to the chain depending on his activity?

Nope, he changes the front manually and adjusts the tension pulling the rear wheel on the horizontal dropout. He may have fitted a longer dropout to the frame, he works for a framebuilder so it's possible. I'll check his bike out this week and try to take some pics.

Thank you. I thought about a sealed hub but I was trying to keep weight to a minimum but you know, if I can't pedal a few extra hundred grams or even two pounds of additional weight I should probably just walk wherever I go and give the bike to someone more deserving. It is not like I am Tour de France competitor or triathlete "shaving grams".

Now if I tried to put the sealed hub on my Masi Speciale I guess that would require some special spoke dishing of the rear wheel or I wonder if I could even get it to fit between the dropouts?

If he needs two different gears for different activities (i.e. polo and street riding), then it's pretty straight forward to combine two chainrings with two cogs sized so the chain length remains the same. Loosen the rear wheel a bit, manually shift the chain over to the desired combination and retension.

What's the spacing on your frame? The S3X hub comes with axles for 120 and 130mm spacing. I used the 120mm hub in my 126mm frame and just added a 3mm spacer on each side of the axle.

You could also ditch the tensioner, and go straight fixed. have two master links on your chain, and take out a length when your in the smaller gear, put it back on when you gear up.

You'd have a dirty chain more than likely, but it sounds like a simpler answer.

sounds like a pain in the ass and inevitably will have uneven chain wear

I've always wondered what a dual drive setup would be like to ride ? That is a left hand & right hand side same gear inches/ratio on both sides while pedaling. Something like this only both sides freewheel or even both sides fixed ?

http://www.youtube.com/watch?v=T-IjXMQmodw

This was a similar concept ?

http://www.bikeforums.net/showthread...le-drive-fixed

Isn't that a steel frame?

Man, I think you are over-thinking this. Just ride your road bike.

Think about what you are asking. You want to be able to switch gear ratios on your single speed or fixed gear bike. Once you get this manual system (like get off the bike, get a wrench out, change the gear) or rudimentary system (only a few gear ratio options) you will immediately want an improvement...to something like your road bike. Sooo...just ride your road bike. :)

The only other option is to make a lightweight fixed gear (probably from a frame that is not steel) and gear it for the hills and you'll have to spin on the flats.

In terms of basic transportation, fixed gear / single speed bikes are like skateboards in that they are only practical in relatively flat cities.


EDIT:
And as far as weight is concerned, you can certainly get a road bike to be the same weight or less than your steel Masi.

The few intracoastal bridges I have to cross are more hill than I want to encounter in a ride. Flat land is good.