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SM Kingpin MkIV

24/06/2012

Steve Morton is a keen cyclist who uses his bikes as everyday transport. For some time, he has been developing his ideal utility machine, based on the once-popular Dawes Kingpin open-frame small-wheeler of the 1960s-80s but with a top-tube added for additional rigidity. The following extracts from a 2002 letter show how Steve’s MkIV version of the SM-Kingpin has evolved.


SM Kingpin MkIV

SM Kingpin MkIV

The main improvements over the MkIII centre around the front forks. The bike now has a pair of Pashley 20″ forks, the same as those on our Two’s Company Tandem and presumably the same as those on the Fold-It. This has allowed the fitting of a front drum brake (90mm, and recycled), and more importantly enabled the fixing of a second Esge/Pletscher type alloy carrier on the forged drop outs which have two threaded fixing points. This arrangement is a significant improvement to the previous axle fixing, and has the obvious advantage that the front wheel may be removed from the machine without affecting the support of the carrier and top box in any way, very useful if the top box is full. (However it is important to note that the third fixing point of the carrier has to be behind the fork crown to enable the carrier to sit level. Unfortunately I did not realise this until after I had fitted the forks – annoying mistake.) The Pashley forks do shorten the wheelbase by about half an inch but any difference to the handling is unnoticeable.

Other changes are:

  • the use of 36 hole, 451, chromed steel rims and 37- 451 tyres,
  • narrow front and rear mudguards,
  • the use of a Weinmann Vanqueur 750 centre pull rear brake,
  • a Brooks Champion Flyer S leather saddle, and
  • front as well as rear led lighting, with supplementary front lighting from a Smart 10 watt lighting system with a rechargeable acid battery.

Otherwise the bike is as MkIII with:

  • brazed in top tube,
  • the dreaded Hammerite paint job on the frame,
  • Sturmey Archer S5/2 gears with a 17 tooth sprocket, operated by two Sturmey Archer twistgrips,
  • drop handlebars on a swan neck stem. (The stem is actually a forced change from MkIII because the alloy clamp on the long stump neck stem cracked. This was a little disappointing as the swan neck stem is not quite as long. The length is important if drop handlebars are used and unfortunately I have not been able to find a replacement stem.)
  • GB brake levers,
  • cables to rear routed along top tube, with gear cables continuing to the gearbox down the seat stays, two white top boxes for conspicuity, security, and weather protection,
  • a 40 tooth chainwheel with 150mm cranks. I find the short cranks are perfect, allowing me to spin the pedals easily, and finally the pedals – my one real extravagance -the MkIV has blue alloy mountain bike type pedals. They do make the bike look stylish though!

I find the bike a real pleasure to ride, and it, or certainly the embryonic MkV would be my ‘bike for life’ – I’m sure you will have come across Gary Lovell’s AtoB article recently (issue 25, August/September 2001).

The bike seems to cut through the air very well even though it might be assumed that the front box would present a considerable drag. Could it be that having the matching top boxes on the same level somehow has a streamlining effect on the machine, reducing the turbulence I create by pedalling? I am reminded of a picture in the very interesting book you published – Human Power: the forgotten energy. The lower picture on page 66 of the Mochet plywood boxes obviously illustrates ‘real’ streamlining but could it be that, even though the front and rear faces of the boxes are flat, there might be something unexplained going on? I like to think so though it’s probably just my imagination. At some future date it could be that I might even shape the front and rear boxes to give an improved streamlining effect without compromising their utility of course.

Just getting back to brakes – on my ideal bike I would have the opposite system to that on my MkIV, i.e. centre-pulls on the front therefore allowing the use of a hub dynamo, and a drum brake on the rear to provide the effective braking. The Kingpin rear dropouts however do not allow the use of 5 or 7 speed hub braked gearboxes. I like the S5/2 so I forego the advantages of the hub brake, and will rely on the front brake in emergencies. It’s not ideal but it’s the best I can come up with at present. MkV is in my mind but it will require wider rear dropouts.

Steve Morton
Hereford, England
June 2002


Steve wrote to me again in December 2006 with news of further Kingpin developments. The photo below shows him competing in a local ‘open’ 10 mile race organised by the local wheelers as part of National Bike Week. He went round in 30 minutes 42 seconds and was pleased to come 12th in a field of 69 entrants. Obviously a lot of people were there just for the fun of it but Steve did beat quite a few serious cyclists. Here’s Steve’s description of his latest hot Kingpin, which I think must be his MkV: 

The Kingpin has a top tube brazed on and 20″ unicrown forks from Pashley. Onto that basic frame I added :

  • a Shimano cartridge bottom bracket,
  • Shimano 600 single key release cranks,
  • a 48T Stronglight chainring,
  • Shimano 600 pedals with toestraps,
  • a 3/32″ SRAM chain,
  • a Sturmey Archer S5/2 gearbox with a 15T sprocket,
  • a stumpneck handlebar stem,
  • a stem fitting S/A dual lever changer,
  • alloy drop handlebars,
  • cut down and turned upside down,
  • Shimano Exage aero brake levers,
  • tribars,
  • a Brooks Champion S Flyer single rail sprung saddle,
  • a 451 36H rear wheel and Schwalbe Stelvio 28-451 tyre,
  • a 406 36H front wheel and Schwalbe Stelvio 28-406 tyre,
  • a Sturmey Archer XFD front hub brake,
  • an Alhonga dual pivot rear brake and a single leg bike stand (essential even for a ‘racing bike’).

Since doing the 10, I have a couple of changes in mind to make it a little faster to ride. Under 30 minutes is obviously the target, but those 42 seconds may take some shaving off. Incidentally, the aero levers were used simply because the rear entry at the top of the lever minimised and simplified the cable routing. The cables were not taped onto the bars in any way. The aero brake levers, the tribars and the small section matching tyres with unequal wheel size also added to the image of the bike as a serious machine!

Steve Morton
Hereford, England
December 2006

SM Kingpin MkV

SM Kingpin MkV

Steve makes it clear that making the Kingpin ‘lightweight’ was only half the story. He decided it was little use trying to shave off grams here and there if the rider was overweight, so he resolved to lose weight himself and succeeded in shedding about a stone, i.e. 14 lb (6.4 kg). This obviously made a great difference too. Steve feels better for it, so the race had other lasting benefits.

He also makes the point that the work he does on his Kingpins is largely a solo effort. It is done without reference to the Sheldon Brown website, for example. To describe Steve’s work as original is difficult, because it must be a synthesis of other bikes he has seen and learned about, but he has not deliberately or directly copied anyone else’s ideas.

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From → Small-wheelers

2 Comments
  1. david permalink

    great bike well done

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