A Holdsworth Trike Conversion Set

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26th.May 2010:

An interesting Holdsworth trike conversion set has just turned up on eBay. Item no: 160438652198

The vendor has very kindly given me permission to use his excellent images:

The Holdsworth tricycle axle conversion set.  UK built, one wheel drive trikes and conversion sets are normally left hand drive. The entire axle is passed through the rear triangle of the donor bike and fixed securely to the rear drop-outs.

Holdsworth has used a rather neat and distinctive form of central, axle casing reinforcement. Instead of multiple, small diameter, half hoops, Holdsworth has chosen a single,  larger diameter, hoop with a straight brace. The hoop stiffens the axle assembly and resists the axle casing from folding up when the rider sits on the machine.

The majority of loads on any trike axle are upwards at the outer ends in response to road shocks. And downwards at the centre from the weight of the rider. The donor bike's chainstays provide for-and-aft bracing to resist compressive loads from the drive chain. The existing bicycle seat stays are supplemented by the triangulation provided by the telescopic, adjustable seat stays of the conversion set. These stays are very similar to Higgins and Longstaff and are finally locked by the clamps provided when the axle installation is complete.

Strong fixing points are provided to fit the conversion set to the donor bicycle's rear drop-outs. Lighter lugs are provided to join the widely splayed, supplementary seat stays to the saddle pin fixing bolt. Or a clamp around the seat post itself.

The axle casing central detail. The central nut fixes the sprocket adaptor to the driven axle. It seems as if this axle uses journal bearing because there are none of the usual bottom bracket cups and locking rings visible. Nor are the axle casings enlarged to fit such cups and rings. A gear hanger bracket is brazed onto the idler side, axle housing.

The complete Holdsworth axle conversion shown with the close ratio, sprocket block lying between the rear drop-out, fixing lugs. It looks as if this conversion set belonged to a tricycle, time trialist. Probably used to fairly flat courses judging by the likely ratios provided. The block would be fitted onto an adaptor which fits a taper on the inner end of the drive side axle. Those looking for more gears and wider ratios should contact Geoff Booker at TRYKIT for a modern, Shimano cassette, freehub adaptor set. Geoff can also provide new hubs and complete wheels to fit any trike.

http://www.trykit.com/

Here is the Tricycle Association's excellent web page on Holdsworth trike conversions:

http://www.tricycleassociation.org.uk/THAHoldsworth.html

and

http://www.tricycleassociation.org.uk/HoldsworthGallery.html?


These Holdsworth trike conversion sets must have been reliable because they can be seen in the latest galleries on the Tricycle Association website. So they are still being used by tricyclists for time trialling and touring.

The great thing about trike conversion sets is that they give the would-be triker a real taste of triking without the heavy expense of buying a complete new machine. Axle conversion sets can easily be resprayed to match the donor bike for a more unified appearance if desired.

Those with sufficient brazing skills can turn a trike conversion set and lightweight, steel, donor, bike frame into a full-blooded trike. This will save the weight of the bike's original seat stays, drop-outs and various fixing lugs on the conversion set. Making for a much neater job once the finished trike been cleaned up and resprayed.

If you are tempted by such a project, or willing  to pay an expert frame builder to do the brazing, ensure you have adequate foot clearance from the trike axle casing. A short wheelbase donor bike will not be the best choice if you have the same genes as Big Foot. It will also make the finished trike more difficult to sell. A longer wheelbase will also be less twitchy at speed and more stable and more comfortable on rough surfaces. It helps if the donor bike frame has "relaxed" angles. An aluminium frame cannot be brazed, of course. If in doubt, as to suitability for a donor frame, aluminium is easily checked and rejected with any magnet.

 The back page of an original 1965 Holdsworth leaflet in my possession from new. Alas a new trike conversion was well beyond my pocket money. Ironically, I bought a complete, used trike for half that price only a couple of years later and used it for commuting between two cities fifteen miles apart. I can still remember that 27 x 1.25 high pressure tyres did not last long on a trike. Today's tyres are infinitely better than those available in the 1960s.

A couple of links with pictures of Holdsworth conversions:

Holdsworth Trike conversion set

Holdsworth Fixed Wheel Tricycle Conversion on velospace, the place for bikes

Well, the Holdsworth conversion sat on the £75 reserve until the last couple of minutes and sold for £95.02 in the end after just three bids. Not a bad price considering there were no wheels on offer. Chris Hewitt occasionally has used spare trike wheels. I'm not sure if the Holdsworth axles/hubs match any other make.  

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