You Were Asking

Have you any idea of themake of this motorcycle? It’s a pity the chap’s leg is in the way. The car in the background is a Sunbeam, which has been inone family ownership since new. The rider is George Bulman of Hackney and later Croydon. He also at one time ownedaNew Hudson of which he was very proud and we also knowhe had an outfit, possibly theNew Hudson. Searches of family photographs are continuing. George Smith, Mike Lunchand Keith Gibbons, email viaGeorge Smith.

Thank you to all for sight of such an evocative period photograph. Fromthe background it is clear George was pictured at a camping weekend meeting in the country, possibly Essex, whichwould beamodest ride from Hackney, or, more likely Surrey, as he later moved to Croydon andmust have favoured the area. With his tent and luggage neatly fastened to the machine’s carrier, we can only guess whether George, in his natty leather coat, is arriving at or departing fromthe weekend rally.

Initially, the machine posed a mystery as the fuel tank looks very like that of a 277cc side-valve Triumph ModelWand with eye of faith, the front fork could just suit, but everything else is wrong, including its date of registration. Themark YK 8083 is a London issue fromJune or July 1925 and as the Model WTriumph was announced for the 1927 season, this machine predates it by about two years.

Its London registration number is a small clue, asmakers sold a slightly greater percentage of machines within a 25/50 mile radius of their works than elsewhere. However, this can only serve as a minor clue, asmany makers sold their machines nationally and internationally, including the manufacturer of the subjectmotorcycle. But it served as a clue, which, alongwith its timing chain cover set at a rakish angle, suggested it could be aMatchless.

While themachine is largely finished in black, its tank is in a light finishwith darker panels, which could match the light grey/green Matchless still applied to some machines in the 1920s and dates from the veteran days with darker green panels. With the chap’s leg blocking the engine, we are left to back up these thoughts with further clues à laHercule Poirot; these include gearbox with curved kick-start lever, exhaust port angle (suggestive of a side-valve engine), rear carrier and front fork design. Without seeing the engine, these observations aren’t conclusive, but the likelihood is this machine isaMatchless made at Plumstead, another London borough, and a dozen or somiles from the owner’s home in Hackney.

Likely to beaMatchless, but what model? For the 1925 season, dealers’ guides implyMatchless offered a six model range comprising the 347cc sidevalve L/4, 347cc sidevalve L/4 All Weather, 347cc ohv L/S and 591cc ohvM(all single cylinder machines), plus the 972cc sv V-twin M/3 and H. As the machine is a side-valve single, it is either a 347cc L/4 or the (perhaps fittingly for a camping trip…) All Weather option.

Last month, the YWA column published an email from long time enthusiast Peter Langridge regarding the poor quality of some ‘rubber’ products offered on the classic motorcycle market. While I addedmy observations, I have no real knowledge of what has led to this situation and hoped representatives of the trade associatedwith themanufacture of such goods would respond. To date, none have.

Fortunately, we have a retired polymer chemist amongst our ranks, Barry Brown. Many of youwill knowBarry from his association with KopHill Climb teamand he proudly adds the team has recently been given the Queen’s Award for Community Service and Charity. On behalf of the TCM team and all readers, I offer our congratulations to all at Kop

Hill and, fingers crossed, this super event will be able to go ahead again later this year.

Barry writes:

“Your correspondent Peter Langridge rightly highlights the poor quality of some rubber products being offered for sale in the UK. This is particularly serious in the case of tyres with flimsy construction and showing deep ozone cracks on sidewalls, even prior to use. There are now strict standards for tyres on sale here and more checks by Trading Standards are needed to enforce these to ensure the safety of riders.

“The same applies to inner tubes, which are now made from Butyl rubber, which has the lowest permeability to gas of any polymer combinedwith good tear resistance. Should any old natural rubber tubes be found, especially if coloured red, they should be removed, as they are prone to cause sudden blowout if punctured.

“I have spent my entire working career as a polymer chemist working with tyres, mouldings, hoses, coatings, cables etc in almost every area of the expanding polymer industry, including plastics and adhesives, and have seen many changes in technology, mainly for the better.

“During the post SecondWorld War period the main polymers used for automotive applications were natural rubber and SBR (styrene/Butadiene). Natural rubber was a strategic material during the Cold War with availability and prices varying drastically, especially during the Russian backed Communist insurgency inMalaysia, successfully overcome by the British andCommonwealth military. The result of this was that rubber products were extended with large amounts of fillers including clay, whiting (chalk), pine tar, mineral oil or anything to conserve supplies. Added to this were the predatory pricing pressures of the major car and motorcycle manufacturers which resulted in a steady decline in quality, so nothing new there.

“The problems mentioned of cracking are simply that of both, natural and SBR rubbers are not resistant to small amounts of ozone in the atmosphere characterised by cracks at right angles to the direction of any strain introduced. Good quality tyres for instance would be protected by a combination of antioxidants, antiozonants, plus waxes which bleed to the surface to give added protection.

“I have recently changed a John Bull tyre on the rear wheel of my wife’s 1929 Calthorpe Ivory, which has been in regular use for over 30 years on numerous club and Banbury runs and which I believe to be over 50 years old, since the company ceased the manufacture of tyres some time after the Dunlop takeover. This company was well regarded for quality and sure enough the tyre was free from signs of ageing.

“Tyres need to be checked frequently for tread and ply separation, as well as deflating to about three/four psi and rotating under load to assess the depth of sidewall cracks.

“Technology has progressed so that most of the issues raised by Peter Langridge can be overcome, such as the availability of reproduction items made in liquid polyurethane polymer, which will neither ozone crack nor discolour if extended over forks or twist grips. There is a wide range now availablemade in such material including footrest rubbers, tank knee pads, grommets, tank mountings, etc.

“For other applications such as trim strips specify EPDM which is totally inert and will not deteriorate over the time, most suppliers to the classic vehicle market keep stock.

“Most motorcyclists choose reinforced PVC petrol pipe, which is a good choice, as the fuel extracts plasticiser, hardening the plastic but tightening the connection. Those using petrol resistant nitrile pipe should check for cracking as this polymer is susceptible to ozone and unreinforced hose should never be used. Always avoid a tight radius when installing pipes to reduce cracking and perhaps apply a light coating of silicone grease to slow crackforming.

“The imminent introduction of E10 petrol will no doubt create further problems for old vehicles, especially fuel systems, but then for every problem created technology will provide an answer, maybe…”

Looking at internet sites, I’ve recently found two adverts for RobNorth frames which take Triumph Trident engines. One of the sites I looked at lists them as ‘new stock.’ My questions are: What is their history? When were theymade? And are they still made today? DeanOwen jnr, email, USA.

RobNorth served an apprenticeship with Coventry-based Alfred Herbert and Co Ltd whomanufactured and provided an extensive range of machine tools for almost a century, until theywere subject to a final buyout, resulting in the closure of the business in 1983. North also competed at national level, road racing sidecar outfits.

Initially working fromadisused colliery shed at Bedworth and latermoving toadefunct cinema in Nuneaton, Rob Northbuilt speedway frames, earningagood reputation for their qualityand strength. At some point, he adapted and alteredaManxNorton Featherbed frame for one of his Triumph-powered outfits.

While his work was strong, the stresses of a racing outfit fractured some parts of the original frame, encouraging him to redesign the frame work, including to the steering head, with the result of nomore breakages.

He also startedmaking frames for other road racing competitors, including Chris Vincent, who presented Robwith a 750cc URS engine for framing.

In 1968, Rob Northwas contracted to make a frame to house a 750cc Triumph engine for Percy Tait. Based on his past experience, North revised the design tomake his first socalled ‘wrap around’ frame. This underwent some further development as he felt the initial subframe too stiff. A year later, he started development work for Triumph and, with input fromPercy Tait, developed his famous RobNorth Trident frame. Others involved includedDougHele.

From this work, he built six frames for Triumph’s racers at the 1970Daytonameeting. At the lastminute, one of the completed machines was taken over by an American rider, meaning Percy Tait had lost his ride.

As this famous story goes, over the weekend Rob built another frame which was rapidly built into a racing Trident powered motorcycle for the renowned Triumph road tester and racer. In itself no mean achievement, as North hand-built his frames alone, bending tubes by fillingwith sand, heating and shaping on formers, then brazing the sections together – all slowwork but, inhis case, precise work. Such was their nature therewereminor differences as one expects with hand-fashioned chassis.

But they did what was required – they handled superbly and were strong.

In the race, Honda fielded four works machines of which three dropped out and victor Dick Mann’s CB750 four finished on three cylinders, just ahead of Gene Romero with DonCastro third, both riding Triumph Tridents with RobNorth frames.

RobNorth built a small number of frames for the BSATriumph group up to 1973 and replicas were made by a couple of others in the USA. Rob moved to the USA, setting upaworkshop in South California where he continued tomake, among other things, RobNorth Trident frames. It is known he built small numbers of other frames and on occasions one-offs for engines customers provided, including the Honda CB750.

Of the two links you sent Dean, one is for an incomplete machinewith a Rob North frame and an educated guess is this is one of the 80-110 frames he built inCalifornia, while the other link is for a TridentMCS. This firm owns the Rob North trademark and supply components from frames to rolling chassis, with the frames manufactured to RobNorth’s famous design, and many other components for Tridents.

When restoringmotorcycles, or any older vehicle, wewill eventually need to cut strips from sheet steel or copper/brass shim. Use tin snips and inmoments, the thin stripweneedas part of a battery carrier, securing a tank or whatever, curls.

It is possible to cut the strips off with a guillotine and shearing devices work, but all leavemarks and/or curlededges to the strip, which then need straightening. Often, cutting flat numberplates from sheet steel ends in disappointment, too.

Suitably reimbursed, some steel suppliers will guillotine strips from their sheetmetal stockwhich, with little work, are sound, and, equally, firmswith water jet cutting and associated equipment can do the job easily, if they are willing todo so.

Problem for us and many others, is that our best local bet is a 35-mile ride/drive fromour workshop and, generally, they aren’t open when I need them – that’s late at night or on Sunday afternoon! An alternative is to disturb the neighbours using ametal mangler (disc cutter), an unwelcome tool in some engineer’s workshops, but often very useful.

Here’s howacouple of strips for a post Second World War motorcycle battery carrier and a rear numberplate for the recently registered 1911 Humber were cut from 1.2mm steel sheet off-cuts in double quick time, leaving our long suffering neighbours no real cause for complaint… this time!

George Bulman of the London borough of Hackney, with his Matchless loaded up for an excursion.

Rob North poses with two of his creations, a Triumph and a BSA triple.

These tin snips are a leftover from my early motoring days in the late 1960s. Running a sixth hand Triumph Herald followed by an old VW Beetle with Speedwell Conversion (the wooden steering wheel was nifty) I learned how to repair (bodge) car bodywork as part of the annual MoT test preparation. And there was logic in making good repairs, as Dick the tester seemed to award marks for ingenuity, thus when I repaired a section of the Herald’s rear chassis near the prop shaft (don’t ask how this got broken, but it involved five cricketers on the way home from an away match and a hump back bridge…) with sheet steel I cut, folded and pop riveted in place, he awarded a pass – even though pop riveting car chassis was illegal – because he considered I’d been enterprising. All probably very bad practice today, but it was a case of ‘happy days.’ And during the learning process, I discovered that trimming thin strips from sheet steel with snips caused it to roll as demonstrated here. Not useful when you need flat, true strips

The cut raw edges to the work can be dressed by many approaches to achieve exactly the same smooth finish with slightly bevelled edges or however you wish. In this demonstration, a hand file, powered linisher and emery cloth was used, one approach for each piece of work to give a near identical end result. But far more important than the approach you choose to dress the steel’s edge is that the work is both true and remains perfectly flat, with absolutely no curl

The finished rear numberplate is photographed with the two battery carrier strips and the previously completed rear numberplate for comparison. While true cuts are easily achievable using this method, as can be seen by the true cuts in the chipboard cutting surface, the edges will be raw and sharp along the cut, so need dressing.

Using scrap chipboard or similar as a base to protect the workbench, place marked sheet steel on the surface and clamp another piece of scrap wood of about ½ to ¾in thickness with its straight edge along the cutting line to serve as a fence. Run the disc cutter fitted with 0.8 to 1.0mm steel cutting disc along cutting marks using the fence as the guide. As you all know, such cutting is best achieved with a number of shallow passes rather than attempting to cut in one pass.

Mark out cutting lines on sheet steel with permanent marker pen or scribe and, if the sheet is rust protected with fluid or varnish, remove first with solvents. The small, finished blank rear numberplate illustrates the intended end result. Although this number plate is undersize compared with current regulations, it was a size used in period, thus the choice of the route you take is yours and this column isn’t advising either way.