Double singlespeed?

[MontyVeda]

... I could just freewheel on the descents.
...
Have any of you ever done anything like this?
...

All the time!

 

[Chris S]

I am going to try doing one of those hilly loops on my best bike with the gear kept at 28/19, which is near enough equivalent to 42/29. If I like it, I will go ahead with the dinglespeed project.

I doubt that I will be able to use 28/17 but if I can, that would be equivalent to my next higher option - 42/26. Forget that - different chain lengths!


A 'dinglespeed' or 2 singlespeeds?

Two chainrings and two sprockets, each pair with the same total number of teeth.

 

[ColinJ]

The bike is off the road for a short time until new brake inners and outers arrive, so I might as well do the dingle conversion now. I found a 29 tooth sprocket in my junk box with very little wear on it. That will do nicely.

I realised that I will need to use an Allen key to adjust the chain tensioner** when swapping between the 2 ratios, so I might as well use that as a hook to lift the chain and thereby keep my hands clean. (** The jockey wheel on the tensioner is on a rod which can be slid in or out to line up with the chain.)

I'll report back once I have converted the bike and done a test ride.

 

[ColinJ]

Hmm... I tried it but was surprised by how much slack there is in the chain in the 42/29. It is a lot more slack than I'd want to take up with the chain tensioner. It might work with a 43 or 44 tooth ring but I am not going to buy an expensive new Campagnolo chainring to find out.

If the bike had horizontal dropouts I would be able to take up the slack without using a tensioner. Maybe one day I will buy a suitable new frame and do it properly!

In the mean time... To simulate overgeared dinglespeed climbing, I will try to do those climbs without changing from the 36/24 gear on my best bike. That is around a 40" gear. (And I can use a sensible gear for the other parts of the rides.)

 

[GuyBoden]

Hmm... I tried it but was surprised by how much slack there is in the chain in the 42/29. It is a lot more slack than I'd want to take up with the chain tensioner. It might work with a 43 or 44 tooth ring but I am not going to buy an expensive new Campagnolo chainring to find out.

If the bike had horizontal dropouts I would be able to take up the slack without using a tensioner. Maybe one day I will buy a suitable new frame and do it properly!

In the mean time... To simulate overgeared dinglespeed climbing, I will try to do those climbs without changing from the 36/24 gear on my best bike. That is around a 40" gear. (And I can use a sensible gear for the other parts of the rides.)

Using multiple sets of chainrings/sprockets with the same chain length, but with the same tooth count or one tooth difference does work.

Edit:
You currently have 52+19=71
You want to use 42+29=71

I'm surprised it doesn't work, but I have a proper track bike with rear track ends.

 

[ColinJ]

Using multiple sets of chainrings/sprockets with the same chain length, but with the same tooth count or one tooth difference does work.

IF you have horizontal dropouts...

I have literally just tried it with the same tooth count (52+19 vs 42+29) and have now got a slack chain.

PS Ah, you have posted the same thing while I was typing!

I'm surprised it doesn't work

I had another look. The chain does have quite a lot of slack and I don't like how much chain deflection the tensioner is having to impose, but it does actually just work.

These pictures show the extra slack on the 29...

I haven't quite got a perfect chainline. I put 2 spacers between the sprockets thinking that would match the gap between the rings, but it is obvious looking along the chain that 1 spacer would have been better. I've come this far - I might as well move the sprocket to improve the chainline and ride the bike to see how well it works. It might be okay out on the road rather than upside down in my kitchen!

Yes, there IS a 3rd sprocket but it is only there for the lockring to tighten against. I did a few rides with the lockring tightened against the end spacer but it kept coming loose.

 

[ColinJ]

When I turned the bike the right way up, I could see that the chainline on the 42/29 was as good as it was going to get without resorting to half thickness spacers. Using two was about half a spacer off perfect one way, one would have been half a spacer off the the other way. Suffice to say, it was fine.

I did a 20 km test ride. The first half was done with my original 52/19 gear, then I stopped to switch to 42/29. It only took me about 90 seconds to do it. Then I set off up a hill that defeated me in 52/19...

Oh wow, this was good. This was VERY good! Despite the slack taken up by the tensioner, the chain ran really smoothly. I have a newish ring, a newish sprocket, and a newish chain and it was so quiet in operation that I couldn't hear it. The gear felt ideal for what I was doing. Hills that I was climbing at 10 - 15 kph felt good but I could have managed those in the bigger gear anyway. Steeper 7 - 10 kph climbs were much better in 42/29. A couple of steep ones that I climbed at 4 - 7 kph would have been way too hard for me in 52/19 but were merely nicely challenging in 42/29.

I am very pleasantly surprised at how well this arrangement works! I will definitely plan more rides which can be done ~50% in one gear and ~50% the other. (I don't want to mess about dismounting and manhandling the chain multiple times per ride.)

There was one catch though...I had to mess with the chain tensioner to get it to reach far enough for the new chain position. Something about that change has stopped the retaining bolt tightening enough so the tensioner slowly slipped down in the second half of the ride. I got within a few hundred metres of home and then the chain peeled off! Probably putting a washer under the bolt head will do the trick? I'll sort it out before my next ride.

The bike is now officially a dinglespeed!




PS Things may not work quite so well once the chain starts to wear. At that point I might have to consider shortening the chain by using a half-link to replace one pair of links.

 

[GuyBoden]

Well done, that's a very creative solution.

I'm presuming that you are using standard Shimano type sprockets removed from a cassette, with a standard hyperglide hub.

If so, as you already probably know, a 30T sprocket would probably work too.

Maybe, someone has a spare used 30T cassette, so you can remove the 30T sprocket by drilling the rivets.

 

[ColinJ]

Well done, that's a very creative solution.

I'm presuming that you are using standard Shimano type sprockets removed from a cassette, with a standard hyperglide hub.

If so, as you already probably know, a 30T sprocket would probably work too.

Maybe, someone has a spare used 30T cassette, so you can remove the 30T sprocket by drilling the rivets.

No, it is Campagnolo, but I now use 12-30 cassettes rather than the 13-29 that I used to use!

I can't remember if I have moved to a second cassette since I made the change. If I HAVE then I probably have the old 30 in a bag somewhere. If I have NOT, maybe it is time to put one of my new cassettes on the best bike and pinch the 30 off the old cassette? It would certainly help with the chain slack, and would give me another 3.3% off the climbing gear.

 

[Venod]

What you need now is a derailleur to replace the chain tensioner, and while your at it a front derailleur and a couple of down tube shifters, would be a good idea.

 

[ColinJ]

What you need now is a derailleur to replace the chain tensioner, and while your at it a front derailleur and a couple of down tube shifters, would be a good idea.

Ha ha.

I have bikes with lots of gears, as you know since you and your lad sold me one! (Ok, that one was minus a front derailleur but it has a nice 11-42 cassette to compensate.)

The thing is, when lower gears are available it is really hard to resist the temptation to change down. The hills I am thinking about for the 'dinglespeed' are no challenge in a really low gear. In 42/29 (or maybe 42/30) they need much more effort, which makes those rides more interesting. Since I don't have a lower gear, I will just have to make the effort in the gear I'm in. Just like people did years ago, though they wouldn't even have had a gear as low as 42/29. I bet many people were riding 42/21 or 42/23 bottom gear 40 years ago?

Instead of being in the ideal gear all the time, on the dinglespeed I will be about 1/3 under-geared, I/3 well-geared, and 1/3 over-geared.

This would not have made any sense to me before I got to like the singlespeed bike. It was only intended to be a knockabout bike to nip up and down the valley roads on, but I started doing longer rides and really enjoyed them. Then I started doing a few moderate hills, and they were good too. It was the longer/steeper hills that stopped me doing more on the bike.

I will still have my other bikes for rides with lots of 15-25% ascending.

 

[ColinJ]

Obviously, if I were bothered about speed, this would be a very bad idea! 1/3 of the time I will be freewheeling, and on steeper climbs I will grovelling rather than spinning an ideal gear.

I like the idea of easy effort, moderate, hard, moderate, easy, moderate, hard, easy... A version of Fartlek on the bike?

 

[Venod]

You can still just use the 2 gears with derailleurs, just stops the messing about changing by hand.

 

[ColinJ]

You can still just use the 2 gears with derailleurs, just stops the messing about changing by hand.

Use the rear mech as a chain tensioner... Select the sprocket of choice and hold the chain there by adjusting the endstops to prevent rear gear changes!

 

[keithmac]

You cold have 8 gears with an Alfine hub 👍