Posts Tagged ‘single speed bicycle gearing’

Over the past several years the fixed wheel has risen to some sort of cult status in urban cycling circles, but I would argue that it’s the freewheel that has the mystical mechanical properties. I mean, the fixed gear is easily understood from a mechanical viewpoint, having no moving parts – the appeal comes from the immediacy of transmission, its simplicity, and the anticipation needed to survive the many hazards of riding fixed in the ‘real world’ of obstacles, without coming a cropper !

NOS 1/8 inch ball bearings

NOS 1/8 inch ball bearings and the inside face of this freewheel

The freewheel was thus invented a long time ago to overcome the disadvantages of fixed and allowed the magic of “coasting” to enhance cycling’s appeal and safety. ( I defy any cyclist to convince me that coasting isn’t enjoyable and fun ).

Mechanically, the fixed wheel is a “sundial” to the freewheel’s “swiss watch” and, I confess, I had always been a little wary of those two small holes on the freewheel cover cone race. I was content to remove and swap freewheels complete from time to time but had no wish to delve any further within.

Now I have discovered that the most intimidating thing about them is the initial doubt about controlling the huge number of tiny ball bearings contained within and the ease with which said bearings fly in all directions when anything is loosened or reassembled … all the rest is straightforward.

the freewheel body

the freewheel body and pawls

My golden rule is :  ” Don’t touch anything unless there’s a container to catch all the bearings, and even then, make sure there is absolutely nowhere else they can roll away to and hide “.  This will probably still happen anyway !

the pawls removed with their fine spring retainer

the pawls removed with their fine spring retainer

Freewheels spin off anti-clockwise so that the motion of pedalling naturally tightens them, and it’s essential when refitting that the threads be well greased or anti-seize compound applied. They need a fair amount of force “down the track” to release this pedalling tightness. There are so many different removal tools for them that it’s not funny, so you may need the help of a friendly bike shop here. A vice is the next most helpful tool as you can then use the wheel’s inherent leverage to your advantage to spin them off on the vice-held tool.

To disassemble the freewheel itself there are generally two pin holes on the cover cone race that turn it clockwise to loosen, using a pin spanner or strong needle-nosed pliers to assist.

the cog and spacing leaf washers with the cover race left

the cog and spacing leaf washers with the cover race left

I think the rule is that the cone race will tighten in the direction of freewheeling though, as this one’s cover is on the hub side and it is right hand thread ( anti-clockwise to loosen ) – just to trick me again !

Freewheels can sometimes be flood cleaned in situ with light oil down the gap, spinning to make them work again, but often will make unpleasant gritty noises afterward as the dirt crunches through them, which is what happened with this 16T BMX single-speed.

you can see the one-way mechanism here

you can clearly see the one-way mechanism here

Amazing to think that all your pedal power goes through those two tiny pawls …

The screw on freewheel clusters of older ten-speeders are much the same internal arrangement … btw,  they probably should be oiled rather than greased, but I had to use some grease to make the balls stick in place for re-assembly. I will gladly take note of any sticky suggestions here !

you need plenty of balls to tackle this job (teehee)

i must have plenty of balls to tackle this job (teehee)

I’ll try to soften it with light oil, but the freewheel is at least engaging and running quietly so far ( see pic top ).

this is how i got it off - sans tool

and this is how i got it off the wheel – sans tool

The above view is from the “outside” though on most older derailleur bikes it is the pin holes for disassembly that are facing out with a left-hand thread.

Now I’m off around the lake, freewheeling with the wind…

see ya !

see ya !


Read Full Post »

as it was — use it or lose it !

I have decided to remodel my old Speedwell popular diamond frame, for better or worse, as changed work circumstances have resulted in it getting less use than it should. Commuting is mostly on the red Road King now, but I don’t want to part with the Speedwell of my youth, so have decided to make it lighter and more responsive, a bike to take mainly on relaxed daytime rides rather than “must get there” practical commutes. I also wanted to give it a more integrated and simple appearance.  This bike is a collection of memories and modifications, it’s not meant to be either pristine or faithfully original.

the new look

It was with reluctance that I disconnected the Shimano “3s” three speed hub, but never mind – this bike was originally a single speed with coaster brake. The “3s” rim is a little worn and I wanted matching wheels this time. Yes, I could have searched for ages for good second hand 27″ or 28″ wheels perhaps, but thought I’d try these new ones that I found for a reasonable price .

new 27″ wheels and fork, centre pull brakes

The bike had lost it’s 28 x 1 & 3/8 inch (that’s the 642mm version) wheels long ago as I had fitted it with the 27″ 3-speed hub in the 70s, and as its original forks were also damaged it was later fitted with a 26 x 1.75 inch i.e. decimal front end, a little less than ideal as far as ground clearance goes.

I previously fitted it with a front rack to hide this mis-match but have since ordered a set of new 27″ chromed front forks and 27″ high flanged front wheel for it, from Vintage Bicycle Rebuilds, so the big front rack has gone, replaced by a little PDW Take-out basket. I’ll do a review on this useful bit of gear later…

it’s much lighter now ..

The fork caused some problems as it did not have quite enough thread and I had to shim the bottom crown race higher – so far it’s OK .. there is no play (fingers crossed). If that trial fails then it’s a new fork.

The rims are Chinese made Weinmann 4019 made of alloy in a kind of satin silver colour – maybe not my ideal style for a classic, but hey – this bike is so far removed from the worn out original that it’s really not worth being a perfectionist about it !

The look is growing on me, anyway …

sand in my shoes …

The front brake is a new Dia-Compe long reach centre pull caliper (just in case I have to fit 700C (622mm) wheels one day). These calipers will fit  27″ (630mm) wheels with the pads near their highest position. They are really classy looking brakes, I think,  and although the coaster is pretty efficient, I wanted the added security on this bike. I have fitted a N.O.S. (new, old stock) vintage steel lever to operate it. The gusset on the bolt-on seat stays was always a bit flimsy for a rear caliper brake. I will have to practise using the coaster more though – old habits and all…

Another temporary addition was a set of Tange moustache bars which I flipped just to be contrarian – actually they were too low the proper way up (down?) as this frame is just a little small for me and I don’t like leaning forward too much. I also tried a very well made Nitto “dynamic 10” alloy quill stem, however the 100mm offset with a low height stem and low bars made me lean forward too aggressively, so I just kept the previous high stem with low offset and “gull-wing” bars as being better for comfort – nice idea, I guess I’m just not the sporty type !

i get my kicks – on a bee sixty six

I’ve kept the saddle as a Brooks – a B66 in antique brown, and am keeping the old rack, but might remove the Miller dynamo and rear light because the front light will need an odd change of location as the stem has recessed bolts and will not take a headlamp bracket.

I am thinking to possibly front axle mount it as I have a bracket for this. Not sure, the cable will look ugly on a chrome fork, and maybe I don’t need lights at all on this one – K.I.S.S. as they say !

The mudguards are the existing Zefal plastic, at least for now. Any metal replacements will have to be be black also.

Tentative gearing is 40T x 18T, or about 60 imperial gear inches on a 27″ wheel – that’s on the low side of neutral, for greater flexibility and for my ancient knees. This isn’t a bike that you pedal down hills, but that does make it a little easier uphill, into headwinds  and starting. We will see, and that’s the usual single speed compromise isn’t it ?

Always locked into the same cadences at the same speeds, regardless of conditions. It is true that practising a high cadence improves your pedalling, well, that’s what I tell myself as I spin like mad in a tailwind …

never mind the horizon,  just smell the salt !

The bike performed well on a c.20km test ride I took today, it’s much smoother riding than the 10-speed Road King despite having the same type of saddle and alloy wheels, but is not in the Gazelle’s league of comfort. Steering is not as light as either of those two bikes, but responds slower than the Road King and faster than the Gazelle – geometry ?

Thank goodness the rain has gone today, I was going stir crazy for a ride ! BTW – the pictures are taken at Swansea Heads where I spent much of my youth messing about on this bike.

the rain has lifted

This is just a preview really – I am a long way from finished yet.

Happy cycling !

Read Full Post »

Having had to use a larger chainwheel on the Speedwell popular, I found the gearing too high on starts and grades at 48x18T, up from the original 44x18T.

The “new” cottered crank set is one that I have had for many years and while it’s not as nice as the delicate spidery original one, it was the best I could find at short notice without using a tapered square modern crank that would be even more out of character.

a different bike - but this is the proper style of crank

So changing the rear cog was the way to go, and like the Malvern Star 2-star the cog on the old coaster hub is a standard thread “English” 1/8″ track style cog. These are relatively cheap up to 16-18T but beyond the 20T mark they are harder to find.

Surly 22T looks huge ...

Surly makes a range right up to 22T in both 1/8″ single speed and 3/32″ derailleur widths however, so I ordered a 22T to try. Believe it or not, while not horrendous, this cog cost more new than the entire bike did on ebay !  (I did get the bike at a very good price though, as it was neither going nor complete).

The top secret cog supplier was an online UK outlet – if you google them you will most likely see 1000 sites for a kid’s pop group that rhymes with “giggles” so just leave off the “s” on your search (teehee).

compare the old 18T with new 22T

To do this “gear change” you need a chain whip to move the (right hand threaded) cog and a C-spanner for the lockring – (it’s left hand thread btw). I use copper-slip anti seize compound on the threads too, so it’s not a nightmare job next time … put the new ones on by hand at first for a few turns – if you have to force them then something is wrong, so re-check before going further (The Golden Rule of Threads).

Also check the tightness again after a few rides, as the lockring can become loose when the cog tightens further under pedal pressure.

It’s also lucky I didn’t shorten the new chain when I fitted it a while back – it now fits about right with the wheel lining up more evenly with the mud guards (fenders) …

the hub's cog thread is now not visible - the thread showing is waiting for the lock ring

With the drilled holes and silver colour this cog (compared with the old one) somehow looks like the bike equivalent of fishnet stockings on the grand old dame, but I like it anyway !

now 48T x 22T on 642mm westwood rims (28 x 1 & 3/8 ")

Single speed gearing is always going to be a compromise – too high on starts and hills and/or too low at higher speed – I hope I don’t find this gear too low, I used 48x20T on the Malvern Star and that’s a good all round gearing for me, but I thought this bike should be a fraction lower. It feels right on a quick ride. We shall see.

you can just see the lock ring here

Incidentally, with a back pedal coaster braked bike the braking effort should also change along with the gearing, in this case needing less pressure but with a longer stroke, though it’s not all that obvious here.

Anyway, enough philosophy, I’m off riding.

Read Full Post »