"Nice bike..." they'd say. (It's fluorescent green, with red tyres, gold hubs, and one black and one blue rim.)
Then... "How do you go up hills?"
If I was feeling cheeky I'd just slap my bulging thighs and say "No worries at all!"
For a more serious answer I'd point out that you can set up your single speed in any gear you like, you can set the gearing as low as you need for the hills you want to climb. In fact I was finding that it was going down hill, and even on the flats, that I was wishing I had another gear to change up to. Riding down the hill from my house I was "spinning out", unable to turn my pedals any faster to push the bike along, and even on the long flat run along the river I was coasting when I could have been pushing. And any time some lycra clad hard-man sitting on thousands of dollars worth of road bike went past me I was itching for a bigger gear to give them a run.
Of course at some point I was going to have to ride back up hill to get home.
It was while I was looking on the internet for parts to change the gearing on my single speed that I found THE IDEA OF A DINGLE.
I think this is the website where I first found the idea explained nippleworks.blogspot.com.au.
A Dingle is a dual configuration, single speed bicycle. Generally with two chain rings up the front and two sprockets at the back. Without derailleurs, it gives the lightweight, straight chain line, mechanical simplicity of a single speed, or fixed gear bike, with the option of two different gear combinations. Using the bigger chain ring with the smaller sprocket for a high gear, or the smaller chain ring with the bigger sprocket for a lower gear, they're usually set up so that the chain length is about the same for both gears.
Of course you can't change gears on-the-fly. It takes a couple of minutes and maybe a spanner, so the dingle is not suited to continuos riding over mixed terrain, but it may be just the thing if you want to use one bike for two distinct types of riding.
My idea was to start out in as high a gear as I could possibly manage, head out from my house down the hill, mixing it with stream of grim faced riders who use my street as part of their oh-so-serious training circuit, ride hard and fast along the flat track beside the river until my legs hurt, or the joke had worn thin, then stop for a rest, move the chain onto the lower gear and cruise back up the hill for a cup of tea and a lie down.
That's my idea of a dingle, but there are probably some less ...ummm... idiosyncratic reasons for a two-geared, single speed set up.
USES FOR A DINGLE
Climb / Descent - The obvious reason. Lower gear for uphill bigger gear for down.
Head wind / Tail wind - Regular riding with a strong prevailing wind. Use different gears for your outward and return journey.
On road / Off road - Ride the big gear on the bitumen till you get to the trailhead, then change down to head off into the dirt.
Race / Bail - Some days you want to push it all the way. Some days you just want to take it easy. One bike, two personalities.
Out with the boys / Out with the family - Big gear for the big egos, little gear for the little tykes. (Am I starting to stretch the idea a bit too far?)
Step down resistance training - Exercise to exhaustion against a high load, then have a brief rest and go again with lighter weights.... I don't know why, ask an exercise physiologist.
Any way that's some food for thought. Here's some eye candy.
There are more pictures of this gorgeous machine at cycleexif.com and on its' builder's website fastboycycles.com. It's got a two-speed freewheel on one side and double fixed sprocket on the other. Look at that chain ring! I'm pretty sure it's two cogs made in one piece! That's got to be a special custom job. You can read the brand in one of the pics I haven't posted, it says White Industries U.S.A.
That's the general idea of a dingle. There are a few details to think about and different ways to actually make it work, so here is my...
Dingle Taxonomy (different types of dingle)
Perfect dingle - The two different gears available on a dingle, depend on the ratios of the sizes of the front and rear cogs used in each set up. The big front cog with the small rear cog gives a higher gear than the small front cog with the large rear cog. If each pair of cogs used has the same total number of teeth, then the chain length for each combination will be exactly the same. For example 36T at the front with 14T at the back uses the same chain length as 34T front with 18T rear. (This might not be exactly true if you used a front cog so large that the chain was in contact with more than half the diameter of the cog, but that's not really going to happen in any practical situation.) Keeping the chain length the same for both gears means that when you change gear the rear wheel ends up in the same place and bike's geometry is unchanged. This is how the dingle can work without derailleurs.
Imperfect dingle - Sometimes keeping the total number of teeth on the front and rear cogs exactly the same in both dingle gear combinations can be inconvenient and limits the choice of gears you can use. But if the total tooth numbers are different in the two gears the length of chain needed to drive them will be different. If you want to use the same chain for both gears you'll need some way to take up the slack in the long gear. Both the bikes in the pictures above have track forks not drop outs, so the rear wheel can slide backwards and forwards up to a couple of centimeters to do this. Depending on the set up you may need to adjust the rear brakes when you switch gears.
Tensioned dingle - This bike uses a chain tensioner such as a singleator or a melvin. This is one way of adjusting the chain length for an imperfect dingle. It also lets you use vertical drop outs and disc brakes. You can probably change the gears without having to loosen off the rear wheel too. What's the down side? Extra parts.... and the look!
These pics come from biketinker.com.
Unchained dingle - One day I went out with a dingle set up so far from perfect that I needed to switch chains when I switched gears. I stopped in the park at the bottom of the hill, turned the bike upside down, took off the chain and promptly lost the connecting link in the grass. Half an hour of searching before I could find it and start home. NOT RECOMMENDED.
Half dingle (or Single dingle) - Two rear cogs and one front chain ring, or one rear cog and two chain rings. What do you call that?
Flipping dingle - The rear wheel has a different sized drive cog on each side. You change gear by flipping the rear wheel around. Apparently this was state of the art racing technology in the 1920s.
Right-handed dingle - Two cogs on the same side of the drive wheel. You don't have to take the rear wheel off to change gears, but you may be limited in the choice of rear cog combinations. I could only find 3 ready made 2 speed cogs on the market. The surly dingle cog comes as a 17/19 17/20 or 17/21, but only as a fixed cog. ACS make a 2 speed freewheel, but I could only find a 15/16 that fits the smaller side of of a BMX flip flop hub. And the White industries DOS freewheel comes as 16/18 or 17/19 ... and costs about $130! You can probably customise a multi speed cassette to get a wider choice of gears. I don't know how.
Left-handed dingle - Apparently you can make a bike with the drive train on the left. Can you make a leftie dingle? I don't know.
I still don't know some things about dingles, but I reckon I know enough to build my big green single speed into single purpose downhill / up hill trainer for my home circuit.