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Monthly Archives: September 2013

Gearing dreams and reality (another one for epicyclists)

Sometimes, you do not fully appreciate why something is the way it is till you try to do it differently (as a writer and a lover of books, I hope that may be the lasting effect of e-readers such as the Kindle:  they will make people appreciate just what a clever piece of technology a book is – but that is by the way). My Dream Roadster, as its name suggests, is an attempt to realise an ideal form of the Imperial Roadster bicycle by retaining its desirable features while overcoming its shortcomings, principally in gears and brakes.

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In practice, I have found that the Dream Roadster has served mainly to deepen my appreciation of the production Imperial Roadster, in particular the two versions of it that I own, a pair of Royal Sunbeams. The matter of braking systems I will consider another day (the Dream Roadster has drum brakes, where the standard Imperial has rod-operated rim brakes) – but my excursion earlier this week ,  which involved the strenuous ascent of Necessity Brae on my 1934 Sunbeam,

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revived a question I had asked before, how many gears does a man need?.  The Sunbeam’s low gear is around 54”. I had managed to climb the hill in that, though it took a deal of effort and determination – at several points I had thought about stopping, but had willed myself on.  Evidently, then, a lower gear would make things easier, but how much lower should it be? That was the question I set out to answer the next day, when I repeated the same route using the Dream Roadster.

The Dream Roadster has a five-speed rear hub (SRAM/Sachs P5) coupled to a two-speed bottom bracket gear, a Schlumpf Mountain Drive. On the present set-up, this gives nine distinct gears (two are duplicates) – a normal range of (approximately) 47”, 58”, 75”, 96” and 118” with a lower range of 19” 23” 30” 38” and 47”.  My guess, from previous experience, was that the lowest useful gear would be the 30” one so I resolved to put that to the test. Before setting out I made a couple of trial ascents of hills near by, Glenlyon Rd

Glenlyon Rd Craigie

and Quarry Rd

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which confirmed my suspicions: the 19” is effectively useless – though it offers virtually no resistance, the speed at which it must be turned to make even the slightest headway requires a far greater effort than walking, for less return. The next gear up – 23” – is only marginally useful as it still requires to be spun at a higher rate than I find comfortable to achieve a forward progress less than walking pace.

So I set out to repeat the trip of the day before (map 4 here) with a minor variation at the start – a new secret way such as Craigie (the district of Perth where I live) abounds in

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My aim was to use 30’’ (the mid-gear of my lower five) as my lowest gear. The ascent of Necessity Brae was still strenuous,

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but less so than the day before, and at one point where the slope lessens I actually changed up to the 38” gear for a time. Though I already knew I could ascend the hill in a substantially higher gear, my aim was to find the most practical lowest gear for the Dream Roadster, and the answer to that appeared to be around 30”.

This was borne out by the fact that I continued without dismounting, save to record the occasional rarity –

red phone box

and some wild flowers here and there:

blue flowers

purple crocuses

(it’s nice, with the hedgerows so dominated by red, to find a touch blue and purple)

I even managed the sharp ascent to Craigend which had undone me the day before, though this time I was expecting it. I returned as I had previously, with occasional stops for blackberries and to record the onset of Autumn,

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(a sight that recalled a line from Eliot:  ‘the communication of the dead is tongued with fire beyond the language of the living’)

and so home via another secret way:

a narrow walled lane

The one casualty of the trip was my mileometer, which I must have shed somewhere along the way (I did have to stop at one point to adjust the front wheel, which had slipped, so I think it was some time after that – I retraced my route on foot next day, but to no avail).

lucas cycle odometer

before setting out…

bicycle wheel sans odometer

…after returning home

So, the conclusion to be drawn (besides the obvious one of checking the tightness of all fixtures before setting out) is that around 30″ is as low a gear as I need. However, once I fell to my calculations, I found a familiar problem. An earlier version of the Dream Roadster had coupled the Mountain Drive to a 7-speed SRAM/Sachs hub, giving 14 gears with a spectacularly wide range of 763%. This setup was arrived at before I ever built the bike and sprang from a couple of simple-minded comparisons – the fabled (and fabulously expensive) Rohloff Speedhub had 14 speeds but a range of ‘only’ 526%, so an arrangement that was cheaper but offered the same number of gears over a wider range had to be better, surely?

In practice, I soon encountered the difficulty I describe above – the lower end of the gear range was something like 17, 20 and 24 inches – of which only the last was even marginally useful. This led me to conclude that the SRAM/Sachs 7 speed hub offered an adequate range in itself, so I swapped it for the SRAM/Sachs 5 speed I had installed in my daughter’s bike, giving us both (I hoped) a more useful range of gears.

However, setting 30” as a bottom gear with the P5/Mountain Drive combination and a 28” wheel implies a direct drive  of some 119”, not only ridiculously high in itself and giving an unfeasibly huge 188″ top gear, but requiring a gear ratio (front to back) of 4.25:1, meaning that a 48T chainwheel would need an 11T sprocket (impossible to obtain for a hub gear – 13T is the smallest I have come across). With 13T at the back a 55T chainwheel would be required to maintain the same ratio.

The upshot is that I have ordered a 14T sprocket which, with the present 48T chainwheel, would give a gear ratio of 3.4:1, meaning a direct drive of c95” and a lowest gear of c24” – still barely useful. The full range would be (approximately)

lower: 24, 30, 38, 49, 60        upper: 60, 75, 95, 122, 150

I look forward to testing that – the long-striding twelve-and-half foot top gear should be fun* but I have to admit that I am already toying with the notion that for my purposes six gears might be enough – using the same 14/48 set up with a typical 3 speed would give me approximately

lower: 28, 38.5, 52        upper: 70, 96, 131.

That gives a bottom gear much closer to my tested useful minimum and makes an interesting comparison with the fabled six-speed Sunbeam of 1908, which offered 49, 66, 72, 88, 96, 129:

Sunbeam A6 crop

(photo by kind permission of Leon Wise)

Some might object to the increasingly wide gaps in my upper range but I think that is a matter of taste and cycling style. The justly-celebrated Rohloff offers 14 evenly-spaced gears (at 13.6% intervals) but for me that is an epicyclic hub brilliantly conceived to do the same job as a derailleur, only better – it’s all about maintaining cadence, keeping the same input and varying the gear to suit.

Riding a roadster bicycle is about varying input to suit the conditions: you are prepared to labour up a hill, or even dismount and walk, knowing that eventually you will reach the top and be able to freewheel down the other side; and on the flat, there is no more lordly feeling than to sweep along at great speed by turning a tall gear at a dignified, leisurely pace. Large steps between high gears are not a problem as you only use them when you are already travelling at speed; it is in the low gears that you want to avoid the jarring shock of too wide a gap.

Around 70 inches was the common single-speed gear for the Edwardians, who liked to calculate at 10 gear inches for each inch of crank, and regarded 7” cranks as the standard. I reckon that a future 6-speed Dream Roadster with the set-up above would give me in one bike the equivalent of two three-speeds, one well-suited to the hill country, the other formidable on the flat.

I have to say I’m sorely tempted…

* 13 yards on the road for a single turn of the pedals, or better than 26mph at a modest 60 rpm – though I expect wind-resistance would be a factor.

Autumn circular with brambles, hips & haws

(The map for this route can be found here)

Well, after a dull morning, the sun came out and so did I. Early on it had shown all the promise of a classic Autumn day – bright sun, a nip in the air, trailers of mist on the hills – but then it all went grey and I thought I wouldn’t bother. Then in the afternoon the clouds dispersed and I though it was too good a day to waste indoors. I found with shame that both my serviceable mounts – the Dream Roadster and the 1934 Royal Sunbeam – needed air in their tyres. Was it so long since I had been out?

After a brief consideration I chose the Sunbeam: it suited the day better, somehow. Before setting out a buzzing made me look up and there was a microlight enjoying what must have been a beautiful view. You need good eyes to see the microlight, but I like the accidental saltire made by the wires – and what a fine sky!

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What route to choose? I decided to take the old road to the West out of Perth which starts with a long climb called Necessity Brae. This makes a fine pairing with the splendidly-named Needless Road, which runs off the Glasgow Road into Craigie. To get there, I decided to take the route round Craigie Hill – it being the especial pleasure of the cyclist to go by secret ways and strange, where motor cars cannot.

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This path swoops around the base of Craigie Hill under a leafy canopy for much of the way:

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Necessity Brae is a strenuous climb in low gear but a merciful bend hides the upper section and keeps you going. This is the view looking back to Perth

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at the top, you are rewarded with brambles, or blackberries, if you prefer.

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They never tasted better: solar-powered Blackberries.

And here we see that great rarity, a Sunbeam recumbent:

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It’s a good viewing point – you can look North East, across to Strathmore, with Kinnoull Hill on the right,

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or North to the Grampians

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The Brae takes you up out of Strathtay, the valley of the Tay, and over a shoulder of land to Strathearn, the broad and splendid valley of the Earn.

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There is a fine descent into Strathearn,  but age brings caution: I enjoy going down hills, but no longer at full-tilt as I did in my youth.  I find the conviction that I am immortal has weakened with the years.

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Once down, I swung back  Eastward towards Craigend and so to Perth.

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There are a couple of handsome railway bridges over the Earn, where the lines out of Perth branch South to Edinburgh and West to Glasgow. This is the Westward route:

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and this is the Southern route, marching away across fields of gold, while the Western route runs across the middle ground:

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A fine bush of red berries made me think of Seamus Heaney and The Haw Lantern, though these I think were hips.

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Further on I found what I think were haws, but I am open to correction. My father told us often on country walks, but alas! I did not heed him well enough.

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Approaching Craigend I was surprised by a stiff ascent and exercised the first rule of cycling, ‘it’s all right to walk’.

Remounting, I joined the main road from Edinburgh to Perth, a short climb over the same shoulder I had crossed earlier in the opposite direction. I passed a fellow-cyclist enjoying his share of brambles and really should have been sociable and stopped but I was eager to be home (why? there was no rush) so made do with an exchange of greetings. I caught a glimpse of the classic view of Perth coming from the South East but I fear the picture does not do it justice:

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And so home again, feeling as always much the better for having been out on my bicycle. What better way to spend a fine September afternoon?

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