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Power Pak

by Andrew Pattle

When the Power Pak was announced in April 1950 by Sinclair Goddard & Co Ltd of 162 Queensway, Bayswater, London W2 they claimed that its main features were "light weight, simplicity, a positive non-slip drive, ease of fitting, and lack of vibration".  The specification included an Amal carburettor, Wico-Pacy ignition and a KLG water proof sparking plug (this was a special plug for motor cycles, which had an extended gland nut surrounding the porcelain insulator.  The plug cap fitted onto this gland nut, thus making the plug completely waterproof).  It was claimed that the Power Pak would cruise at 27 to 30mph and would return 200mpg at 20mph.

The Power Pak was a 49cc engine mounted above the cycle's rear wheel.  The engine was on the right hand side with the cylinder pointing downwards.  The cast alloy frame of the Power Pak was clamped onto rubber sleeves around the seat stays of the cycle and there were several different designs of clamping plates to fit different sizes of bicycle.  A stay from the bicycle's rear axle was secured to the rear of the Power Pak via a rubber bush.  This stay was drilled to suit 26" or 28" wheels and it also had a drilling for a mudguard stay.  A lever on the left of the machine controlled the engagement of the roller drive.  In the uppermost position the roller was disengaged, the next position was for normal running and below this was the "emergency notch" - described as being "to provide extra pressure in the event of a soft tyre".  The kidney shaped fuel tank gave a reserve of fuel which could be used by tipping the unit forward - a lifting handle was provided for this purpose.  Petrol:oil mix was 16:1, the carburettor was an Amal 259/001D, the magneto was a Wico-Pacy Bantamag and the plug was a KLG WF50.  A single lever controlled the throttle and decompressor.  On early models this lever was similar to a 2-wire derailleur gear lever and, therefore, an extra spring was needed on the decompressor to keep the cable in tension.

Sinclair-Goddard soon changed its allegiance from KLG to Champion and recommended the use of an L8 plug.  However, illustrations on their advertising material continued to show engines fitted with a WF50.

Because of its deflector piston design, the Power Pak was not the most powerful of cyclemotors: adequate for solo work but in need of much pedal assistance for anything heavier - as my own experiences with one on a tandem have shown.  On 28 June 1951 "The Motor Cycle" contained a picture of a tandem quadruplet powered by a Power Pak but its comment of "there's no need to push" could only have applied to going down hill.

Design of the standard model Power Pak changed very little over the years but there were several detail improvements, most of which were made in 1951 as minor problems came to light.  The original models had a screw-in end to the crankcase which allowed access to the big-end bearing.  From engine number 6751 this crankcase door was replaced by one held by three studs.  The big-end itself was held by a circlip which, if not properly fitted after an overhaul, could come off and drop into the transfer port, damaging the piston and cylinder.  A modification of a heavier circlip was introduced on engine 9501.  If dislodged this would seize against the crankcase end, stopping the engine before anything more serious happened.  Other variations concerned the petrol tap and pipe - this was because of problems with supplies rather than design improvements.  There were also two types of crankcase oil seal, drive roller and magneto mounting plate; in all cases the two types were not interchangeable.  Some Power Paks were built with a steel con-rod instead of the standard alloy one.  Again, these were not interchangeable and the crankshafts they were fitted to were different too.

The Council of Industrial Design selected the Power Pak as part of its exhibition at the 1951 Festival of Britain.  Power Paks were exhibited both at the South Bank and as part of the Festival's travelling exhibition.

1952 saw the introduction of a magneto with lighting coils and a new design of roller, known as the "Series B".  Also, the "emergency notch" disappeared at about this time; it was intended for use when the tyre pressure was low and no pump was available, but several owners found it useful to overcome roller-slip in the wet.  Using the "emergency notch" with a fully inflated tyre would eventually damage the main bearings, so it was removed.  But, of course, the big change in this year was the addition of a second model: the "Synchromatic".  The Synchromatic drive was nothing more than a clutch, but operated by the same control as the throttle.  Rotating the twist grip first engaged the clutch and then opened the throttle.  Outwardly, the new model looked very much like the Standard Power Pak but could easily be distinguished by its polychromatic copper fuel tank.  The Standard model now cost £25 4s (it had gone up to £26 5s in 1951) and the Synchromatic was an extra 42s at £27 6s.  Once again, slight variations occurred and there were two designs of clutch and roller, one with six locating teeth and one with four teeth.

No history of the Power Pak can be complete without a mention of Peter Lee-Warner.  On 20th March 1953 he set off to ride to Australia and back on a Tradesman's cycle powered by a Synchromatic Power Pak.  The intended route was outwards via France, Italy and the Balkans, Syria, Transjordan, Iraq, India, Burma, Siam, and Malaya.  The return journey was to pass through Egypt, North Africa and Spain. The cycle was fitted with a 2 gallon auxiliary fuel tank in the frame triangle and a tank of drinking water below the front carrier.  By the middle of May he had reached Baghdad where he recorded an account of his experiences so far for the BBC Midland Regional programme "What Goes On" which was broadcast on 28th May.  It was while in Iraq that Peter changed his plans and decided to make his journey a trip around the world.  September saw Peter on his return journey, flying to San Francisco on a "Clipper" airliner.  Then there was just the 3,000 mile journey to New York to complete before boarding the "Queen Elizabeth" for the voyage back to Britain.  At midday on 20th October 1953 Peter rode up to Australia House, the starting point of his journey, where he was greeted by Vivian Blaine, star of the musical "Guys & Dolls".  The four-figure milometer on the Power Pak read 5,501 miles - on its second time around.  The Power Pak had suffered no mechanical trouble on the journey, and had averaged 200 miles to the gallon.  Part of the reason behind Peter's journey was that he intended to emigrate to Australia and wanted to "look the place over first".  He went to Australia for good in 1954.

More detail improvements were made at the end of 1953. For the Synchromatic there was a new twistgrip which incorporated a fingertip tickover adjuster.  Tickover adjustment had been a problem on earlier Synchromatic models; the carburettor setting which gave a reliable tickover could often result give a rich mixture (and hence four-stroking) at normal running speed.  On the Standard models, of course, a reliable tickover was not needed. The clutch-less model now became known as the "New Standard" and had modified porting to improve engine efficiency and now this model too had a twistgrip control.  The price of the New Standard was £19 19s but the Synchromatic remained at £27 6s.  From August 1954 the New Standard model was fitted with the BEC carburettor in place of th Amal instrument.  More changes were made to the New Standard at the end of 1954, The fuel tank now had a rib all the way round the outside - not as elegant as the previous "seamless" design, but cheaper to produce.  This tank was further changed in 1955 to incorporate simpler mountings.  At the same time the lifting handle at the back was changed to a smaller plate.  It was also announced that the 1955 model Power Paks were available in colours to match any cycle on the British market; in fact, the choice of colours being offered at the 29th International Cycle and Motor Cycle Exhibition in November 1954 extended to two-colour spotted designs.  Price of the New Standard was increased to £23 2s but, again, the Synchromatic remained at £27 6s.

For most of its life, the Power Pak was supplied complete with a 26"x1 3/8" Dunlop Motorette tyre; this could be exchanged for a 26"x1½" or 28"x1½" for an extra 3/-.  The recommended tyre for the earlier models was the Dunlop Tandem (ie those machines produced before Dunlop introduced the Motorette to its range).  The cables supplied with the Power Pak were for a gent's cycle frame (known as Type A cables).  They could be exchanged for longer cables suitable for lady's cycles and double-gent's tandems (Type B) or lady-back tandems (Type C).

For a short period in the early 50's the additional accessory of a "Power Pak" pennant was supplied with each engine.

Introduced in 1952 was a chromium-plated steel luggage rack, which fitted above the fuel tank, and a free-wheel guard.  The Power Pak's roller was directly above the cycle's free wheel so there was a danger of dirt being dislodged from the tyre and dropping onto the free-wheel.  On a cycle without a gearcase, the free-wheel guard could be fitted to give protection from this problem.  An enamelled luggage rack was also announced, but not actually produced.

One other accessory was a set of anti-splash guards to stop water being thrown forward from the roller onto the rider; these were fitted as standard from the end of 1952, but were available as an extra for earlier models.

Like the Cyclemaster, the Power Pak had its own newsletter: the "Power Pak News". Unlike the "Magic Wheel" it was distributed to dealers as a sales aid, rather than being a subscription newsletter for owners.  Dealers were generally well provided with sales material.  As well as "Power Pak News", there were leaflets which could be supplied with the dealer's name overprinted, special display stands and printing blocks for incorporating Power Pak material into the dealer's own newspaper advertising.

The discontinuation of the Power Pak cyclemotors was announced in October 1955.   This was prompted by the launch of a new Power Pak model, the Mo-ped. The announcement was somewhat premature because The Mo-ped was destined never to reach full production and it would be the cyclemotor units that continued for several more years.  The Mo-ped was not an original design but a version of the Italian Nassetti model AR.*  Less than a month after this announcement, all three Power Pak models were exhibited at the Earls Court Show and, for the first time, the price of the Synchromatic unit had been increased - to £33 11s. The New Standard now cost £28 7s 10d.  In January 1956 a further announcement confirming that the cyclemotors would continue in production was made by Sinclair Goddard.

At the end of the 50's the cyclemotor market was rapidly dwindling but the Power Pak continued to be available until 1961 - one of the last three cyclemotors on the British market (Cyclemaster and Itom being the other two).

First published - June 1993

* Please Note: further research subsequent to the publication of this article indicates that the Power Pak Mo-Ped was not a Nassetti.  Although the frames are nearly identical, the engine of the Power Pak was a modified Itom Tourist.

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