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The Merco story

By Ian Russell

Andrew Nahum of 'Model Engine World' has twisted my arm to recount what I know of A-M/Merco history. I have to say where this is concerned I am very much a Johnny-Come-Lately, but I am certainly willing to say what I know in the hope that better informed people than me will add to and correct anything I say. Ideally this document should become an ongoing item with additional information being added as it comes to light. I am certainly willing to volunteer as co-ordinator for this task. One thing I have come to realise with our engine histories is that most of us know something, but I have never met anybody who knows everything. Another thing, it is very easy to think of something as fact, whereas if we are truly objective, we realise it is subjective opinion (our own or somebody else’s) or hearsay. Also, human memory is highly fallible, and the longer since the event we are remembering, the more likely we are to remember it wrongly. The most accurate way of recording our history is to get as many opinions as possible, and consider the evidence for these, cross referencing them whenever possible. By sifting through these, a good approximation for the truth can usually be deduced. Of course, contemporary writings (engine tests, announcements of new engines, happenings among the engine producers, etc.) are usually accurate, but even here there can be political considerations involved. Sometimes it is "the done thing” to put a tactful gloss on the true facts. (But of course what I am writing now is The Absolute far as I am aware!).

For sure, although people often think of them as synonymous, A-M and Merco originated as two entirely separate companies with entirely different owners. Having said that, I believe they were all members of the West Essex club, that hot-bed of aeromodelling activity just after the last war.


I believe A-M was started in 19?? as a collaboration between three people, Dennis Allen, who had the engineering/production know-how, (Did he already have an engineering business?) Henry Nicholls, who ran Mercury Models, (and provided/arranged most of the finance?), and Len Steward, who had worked for various model engine companies, (Kemp engines, then AMCO)(*1). Len was a very competant machinist/engineer and we frequently read he was noted for his skills with the hone. I believe it is well documented how Len designed and built a 2.5 diesel which was offered to AMCO and possibly E.D., but they were not interested. Thus the design moved with Len to A-M and became the Mk.1 A-M 25. I wonder if this engine was the reason for A-M coming into being? (CHECK) Subsequently other A-M designs and marks appeared. A man called Les Parker also figures prominantly in the A-M hierarchy. The September 1960 Aeromodeller reports the companies second move into larger premises, and quotes Les alongside Dennis Allen as a “partner proprietor”, so the indications are he should be included with the above three gentlemen, PECKING ORDER? Dennis/Parker/Nichols/? Steward effectively an employee? Ron Ward also listed as on the payroll. (presumably designer of such models as Ward’s Wagon)

It is interesting looking at this 1960 article to recognise in the photos pieces of machinery still being used 25 years later when I became a partner.


I understand Merco was born from a suggestion by Bill Morley to Ron Checksfield that they should design and get into production a British C/L stunt 35 engine. This was primarily to make such an engine easily available to enthusiasts in this country, (at a profit of course, otherwise it would be a pointless exercise). The definitive stunt engine of the time, the Fox 35, was difficult and expensive to obtain in this country in those days. And if the new motor could be better than a Fox 35 so much the better. Henry Nicholls was associated to a degree with Merco, in that he is listed in contemporary adverts as the distributor.

Bill was one of the top British C/L Stunt competitors in the 50’s and 60’s, placing high in the Gold Trophy and gaining places on the British international teams of the time. His designs include the APS 'Thunderbolt', which is for me, one of the most aesthetically pleasing models of all time. At that time there were so many models which were clearly Thunderbirds by a different name, but while obviously having all the Thunderbird, the Thunderbolt managed to have a distinctive classic look all of its own, and at 48” was just that little bit smaller, to fall into a niche 'one size down' from the largest of the 35 size models of the time. For a truly classic complete package today it would be hard to beat a Thunderbolt with a Merco 29 on board.

This is also a good point to give a little history/eulogy on Ron. Ron was already world famous for his engine rebuilds of various engines, particularly the Checksfield Special speed and T/R engines based on the McCoy and Dooling motors. He also did some Oliver Tiger III reworks which are not quite so well known. I believe these were the ones with extra long venturis, about a half inch taller than the standard item, but visibly the same shape.

I understand Ron was a relatively retiring person who preferred to keep out of the limelight, although when I was privileged to meet him on a couple of occasions he proved to be a pleasant sociable man, certainly quite willing to talk about a common interest, - engines. It seems Ron grew up with his family, went to school, reached leaving age (14?) and left, with no formal qualifications. Subsequently he never obtained any employment, and remained living at home. In due course he reached National Service age, duly fulfilled his patriotic duty and then returned home. Still he lived at home and never got any job. He had an abiding interest in.......knowledge! He seems to have spent most of his time in his local public library, reading anything and everything he could lay hands on, of a technical nature. He also possessed the most amazingly retentive mind. It appears that once absorbed into his mind, something was there permanently, and could be recalled as needed. And incredibly, he also had the intelligence and natural ability to apply this knowledge to problems and design matters better than most professionals, despite having no formal training. It must have been during this period that the famous Checksfield Specials were born.

When Bill put the Merco suggestion to him, he was over 30 years of age and still had never had a job. From these modest and unlikely beginnings Ron did all the design work and made all the drawings, dies, jigs and tools necessary to produce the Merco 29 & 35. Talk about “in at the deep end”!! Not only this, but he also made a complete set of “check jigs” - I don’t know if that is the right terminology - for the engines. If you ended up with an engine with something wrong with it and didn’t know what, using these it was possible to assemble the engine one part at a time, and check if it fitted in the jig. When you reached a point where something would not fit, you knew this was the component at fault. Of course, having no 'day job' clearly meant that Ron had more time than most would have had to apply himself to these tasks.

The Merco 35 and 29 duly entered production, and Ron then designed the 49 engine, doing for this engine what he had done for the 29/35, and catering for an increase in size to 61 in due course.

By now the business had snowballed to such an extent that it became impossible for the small two man Merco company to keep up. Peter Chinn’s 'Latest Engine News' column in the September 1961 Model Aircraft records that getting the first three Merco 49 prototypes to running stage was the final achievement of the original Merco company, before it was sold to D. J. Allen Engineering. Thus A-M and Merco came under the same ownership for the first time. ..............And Ron Checksfield went with the business.

Merco company notepaper is headed:

D.J.ALLEN Engineering Ltd
30 Lea Valley Trading Estate
Angel Road . Edmonton . London N18 3JD
Telephone: 01-803 9321
Telegrams & Telex: 25101 FDELON G

Registered number 574138 England.

The Directors are listed as D. Jackson-Fielding (Managing); D. J. Allen; L.C. Parker, T.A.Munn F.C.A., (Secretary), E.B. Payne M.A., A.C.M.A. The 01-803 system of telephone numbers was not in operation for very long, so this can be tied down to quite a short time frame.

I find it so interesting to learn that at its peak D. J. Allen was employing a workforce of about 30! Those were the days! Although nothing to do with A-M/Merco, the climate of the time is well illustrated by a 50’s report that E.D.’s were producing 50,000 engines a year! D. J. Allen (or Dennis Allen?) eventually sold/left the business, (possibly to Parker?)

The various marks of A-M and Merco should be documented, and this should not be a difficult task. A piece of information I can add which is not obvious from a bland description of the marks concerns the change from small to large crankcase in the 49/61. Ron’s small Mk1 case is undoubtedly a thing of beauty, a classic, a work of art. For the large case it has been beefed up with the large vertical bar from under the exhaust to the mounting lug, and with its back cover screw bosses extending right forward to the front face of the crank chamber looks for all the world as if it is intended to cut off the front housing and substitute a bolt-on one. Not so. It seems the radio boys started to complain about vibration, (early over-sensitive equipment?) so Merco commissioned a professor at London University to investigate and recommend a cure. The professor duly pondered and then pontificated, no doubt collecting a fat consultation fee along the way. “Make it heavier, it will vibrate less!”. (A heavier crankshaft counter-balance was possibly also a result of this). So the chief conclusion of all this expensive intellectual activity was that heavier items subjected to the same forces vibrate less! Hmmmm! Didn’t we cover that in ‘O’ Level physics and ONC Mechanical Engineering? So the vertical bar and extended screw bosses were deliberate weight-adding exercises. I suspect the decision to consult the professor was a management one, and not Ron’s!

By the 80’s Merco was owned by an engineering company called Ferraris, whose chief business was making medical instruments (*2). Ron Checksfield was still with the business. The company makes medical tools, but they also make medical measuring instruments, like for example respiration gauges for measuring lung capacity and efficiency. These were all old fashioned mechanical designs. Here Ron’s genius came to the fore once more, and he dragged them all into the electronic age, teaching himself electronics and redesigning all these instruments to electronic/digital sensing and measurement and readout. Not to put too fine a point on Ron’s value to the company, I understand this exercise ensured the company’s survival. Ron subsequently used one of these gauges to measure the “respiration” of some of the engines!!

One story I like about Ron is how, on taking delivery of his brand new Myford lathe, no doubt in pre-Merco days, he stripped it to the last nut and bolt and rebuilt it properly! So those Checksfield Specials got off to a good start in life!

Peter Chinn’s 'Motor Miscellany' column in Radio Modeller May 1990, under the sub-heading 'Classics of Yesteryear', gives an excellent little history of the Merco 49 and 61. The Merco 49 and 61 were clearly the World Leader of their day, and the same article comments that at the 1965 British Nats Merco 61’s took 1st., 2nd., 3rd. ,4th., and 6th. places, with 49’s taking 5th. and 7th. In the World R/C Champs. that year, Mercos powered half the entries, including the winner. Thus Merco has a truly majestic record, and ranks as one of the greatest classic motors of all time. Peter also remarks that in the 25 years since their beginnings, Merco had undergone several changes of ownership, and this is obviously an area to be investigated. (*3)

Round about 1983 Ferraris decided to sell the Merco/A-M business. In their employ was a man called Reg Hills, who had been with the company man and boy, since the Dennis Allen days. He became the buyer, and set up production under the name Forest Engineering, living as he did at Waltham Forest in East London. This was an historic occasion because for the first time since their inception, Merco did not have Ron in their employ, he remained with Ferraris. However, he remained good friends with Reg and was consulted for his advice on various matters from time to time.

At this time I became friendly with Reg and started working at the premises at weekends, unpaid of course, but in heaven learning how to operate the machines and such. I well remember my incredulity and the thrill when the first batch of engines went out of the door with cylinders honed by me! In due course it seemed that the company was not progressing as one would have wished. We agreed I should take a half share in the business, matching Reg’s investment. Because of its small output, (a staff of two full time), Merco was running on about a three month delivery period, and everything made could have been sold in three markets, viz. in England, in the USA, and in the rest of the world. This is not to say there was a huge demand, more that the output was, relatively speaking, so small. So there was scope for increasing production. My hope was that my money would be used to buy some modernish machinery, (possibly second hand/CNC?) enabling the company to increase production to the extent that when I eventually left the Railway, where I was employed as a Civil Engineer, there would be a nice little business I could retire to and live happily ever after. Ah, the best laid plans of mice and men!!

In my time with Forest Engineering, I felt we were rather up against it trying to compete in the modern R/C market with a rather dated design and 25 year old production methods, machinery, jigs and tooling, against the excellent modern products coming so cheaply from the Orient and the East. But there was one market where we should have been unchallenged, that of C/L Stunt. A widespread perception at the time was that the traditional loop scavenged engine was the best format for the C/L Stunt engine, and the 60 size was the size for the serious flier to have. And the Merco was the last such engine still in production in the world! I did persuade my partner we should produce the Merco 61SS, (Super Stunt), using data taken from an excellent research project by an American stunt enthusiast/engineer/academic, Scott Bair. This was sent to us by Tom Dixon, who was acting as our agent in the U.S. at the time. This motor had milder timing than the standard R/C motor, and a rear plug position. This engine might have assisted Merco’s fortunes significantly. With only a venturi to produce, instead of a throttle, which was surprisingly labour intensive, it was significantly quicker and cheaper to produce. A throttle took about 20% of the time needed to produce the engine, so there was an immediate 25% increase in production/revenue at no cost. It sold at the same price as the R/C motor, (and was still excellent value). However, I feel it was held back by a desire to cater for the home market / R/C fliers, which Reg felt was important.

No machinery was ever bought with my money, and then, while the first experiments with ABC construction were in progress, I became aware of two things. Firstly it appeared to me that the business seemed to be in a state of suspended animation, neither going forward nor backward. Secondly, a company called Premier appeared on the horizon. Premier already had a flourishing kit/accessories business, and wanted to add engines to their portfolio. The price being offered was acceptable, so I had no objection and agreed to sell my half of the business. I was to bow out, and Reg, on receiving his payment for the company was to remain as a director and general manager. During the Premier years I had no input to or connection with the company whatsoever, except that until I received my money, I still owned half of it!

Thus Premier Engines was born, and they arranged for the use of premises at Southminster in Essex. During their reign various “improvements” to the engines were introduced. The ABC construction started at Forest Engineering was brought in, albeit ABN in truth. The dies were modified to facilitate the increase in size of the 29/35 range to include a 40, and the transfer passages on the 29/35/40 and 49/61 series were also significantly enlarged. The word MERCO was modified, incorporated in much larger letters on a diagonal raised plinth on the transfer passage. The engines were anodised black and the large MERCO polished to make it stand out. All this was chiefly an exercise in marketing, but also resulted in a further slight increase in weight!. (The professor would no doubt have approved!). The shaft size was increased from half inch to 15mm, in a search for more power, (also adding weight), but the basic loop scavenged cross flow design remained.

The A-M 10 and 15 were also brought into the modern world, by modifying the dies to accommodate a silencer, a “built-in” throttle, and schnuerle porting. This little exercise represents a classic example of the dilemmas facing the engine manufacturer. There was a steady but not large demand for the 10 and 15. It appealed because it was virtually a vintage, and definitely a classic, engine, and still in production and available. It thus appealed to 'Classic' and 'Nostalgia' enthusiasts. But the shops were not ordering in any real numbers, saying “It’s a new world. Everything is R/C now”. So the thought was put to them, “What would you think if the 10 and 15 were updated to schnuerle porting, R/C, and silenced? And a glow version made available?”. “Brilliant” said all the shops. “We’ll sell thousands”. So the deed was done, the model shops informed, and Premier sat back waiting for the orders to flood in. Back came the responses, “Oh all right, send us one, and if we sell it we’ll order another one”. Or even worse, “We’ll mention it, and if anyone wants one we’ll order one”. And of course, the vintage/classic market was lost completely. What such enthusiast wants a schnuerle ported silenced R/C motor? Digressing slightly, there is an interesting parallel here with what happened to Lotus Cars. While travelling from London to my office in Birmingham daily, so as not to waste the time on the train, I took a Diploma in Management Studies at Coventry Polytechnic, a very car oriented establishment. One of the case histories concerned Lotus. They could not produce cars fast enough, and dealers were e.g. ordering ten cars and being sent three. The dealers were asked “If we could supply the numbers you want, what would your orders be?”. The replies confirmed or even increased the numbers they were asking for. The banks were approached and on the evidence of these replies a large amount of money was borrowed for a big increase in production capacity. The dealers were informed and Lotus sat back waiting for the orders. There was an immediate reduction in numbers of cars being ordered. Asked why, the dealers said “We never really wanted ten cars, we wanted three. If we ordered three, we got one. The only way we could get three was to order ten. Now that you supply the numbers we really want, there’s no need to over-order”. So Lotus was overextended financially and went to the wall. The moral in both these cases is be extremely careful with your market research. Ensure you ask the right questions and understand the situation fully. Model engine-wise I notice a possible parallel here with PAW motors, who also introduced glow versions of their engines which did not remain in the range for very long. One source of solace for collectors though, these A-M and PAW engines are now becoming very collectable! The dies for the A-M 25/35 engines disappeared in the mists of antiquity, and we don’t know what became of them. A small run of A-M 25’s was produced by Forest Engineering using the remaining stocks of the crankcases. These are among the best A-M 25’s ever made, having excellent piston/cylinder assemblies, testament to Reg’s skill with the hone! Subsequently “Merco Engines” (see below) produced a very few 25’s on some sandcast cases made using one of the diecast cases as a pattern.

For reasons not quite clear to me, Premier disappeared from the scene. Maybe they realised how difficult it is to make a living in our hobby. Since Reg and I were still waiting to be paid, we still owned A-M/Merco. Reg moved the business to new premises and soldiered on doing sterling work with development and production, trading under the name “Merco Engines”. During this time preliminary sketches and drawings were laid down for a 10cc side valve four stroke, a layout which produced an exceptionally small engine for the capacity, but before this reached fruition diesel versions of the Mercos were produced, and also a spark version of the 61. Finally Reg designed and produced the wonderful, awsome, Merco 120 Flat Twin. This necessitated the addition of yet more metal to the “front face” of the crankcase, so yet more weight was gained, as this carried over to the single cylinder 61! Less than a hundred have been built so if you own one you have a rare piece of engine history. I did have the one marine version of this motor built through my hands. This was distinguished by having the exhaust and intake on the same side (the top) of the engine, whereas the aircraft versions had the intake at the top and the exhausts at the bottom, so this engine is unique. This engine is now destined to reappear with aircraft cooling fins, as that is where its new owner’s interest lies!

Meanwhile, I had not lost my interest in engines and rather than trying to beat them, I joined them! I started trading under the name Rustler, sub-contracting work where the value is best, producing engines for a niche market too small for the major manufacturers. This entails farming out components and doing final inspection, fitting, and assembly myself. The business is chiefly reproductions of classic vintage engines, but being a C/L stunt enthusiast, I have not lost my interest in Merco. Reg and I agreed an amicable parting of the ways, (true, - no politics here!). I have the rights to the name in double barrelled form, and he retains the straight Merco title, so I guess we have “done a Rossi”, like when that company split into Rossi and Nova Rossi. My first batch of Rustler-Merco 61S true ABC C/L Stunt motors has been up and running for some time now. And one of the jewels in my crown(!) is the totally new C/L stunt engine, the Rustler-Merco Metamorph 40S. This is the first new design bearing the Merco name for 40 years, and is so called because it boasts my unique new silencer system which can be assembled in either side exhaust or rear exhaust configuration. In the C/L Stunt world, until now it has been necessary to buy an engine in each configuration if you want to have both. Since the first draft of this article was produced, one of these Metamorph 40’s has placed second in the Classic stunt event at the U.S. Nats, 2002. What a thrill.

One comes to realise that while there are various engine producing companies, in the early days certainly, the number of people involved in engine production has been surprisingly small. In America the classic example must be Bill Atwood, who was involved with an amazing number of engines of different makes. In this country there was a large impetus immediately after the last war, and we find one person frequently moved from one company to another, or perhaps started up their own business after initially working for another. Sometimes there is great cooperation between various companies which one would assume would be rivals. A fact not commonly known is that a large number of the components of the early Dunham replica engines was made for them by Merco. Merco also advised Dunham on suitable production methods and machinery, as they moved towards 100% in house production. I have to say that one thing I find curious is the way Dunhams produced replica engines which were technically no different from Mercos, yet sold at two or three times the price. Was Merco on the wrong track here?


Date for set-up of A-M
We should talk to Dennis Allen, Bill Morley.
*1 consult Len Steward obit - lot of info.
*2 Owners between Allen and Ferraris?
*3 Possibly during the Ferraris period, although Merco remained owned by Ferraris, Ferraris itself
changed hands, so there was a 'hidden' change of Merco ownership.
When did Reg Hills start at Allen Eng?
prototypes A-M35 Glow/Merco 20.
Check Ron Prentice article in MEW on Dennis Allen.
Ask Bill Morley his design/contest record.
Was HJN West Essex?

Merco 35 - Prototype 1958. Production 1959. Multispeed Feb 1960.
Merco 49 - Design started 1960. Prototype Jan. 1961. Production Spring 1962.
Merco 61 - Prototypes tested 1963. Production 1964.


'Merco - The Early Years' by Bill Morley. MEW No.73.Oct. 2002. p3.
Aeromodeller Sep. 1960. 'Behind the scenes at D.J.Allen Engineering Ltd.'. p483.
Radio Modeller May 1990 'Motor Miscellany'.
Model Aircraft Sep. 1961 'Latest Engine News'.

Ian Russell

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