Dutch Delights - the Typhoon Engines

ATY-01 Group of Typhoon engines

This article is intended to serve as an introduction to the range of high-quality model engines manufactured in the Netherlands from the late 1940’s through to the early 1960’s by J. G. Veenhoven of Keizeragracht 372, Amsterdam, Holland (more properly known as the Netherlands today). Veenhoven applied the “Typhoon” trade-name to his products, which is the name by which they are best remembered. His manufacturing facility was generally referred to as the “Miniatuur-motorenfabriek Typhoon”. He characterized himself (quite accurately) as “The only maker in the Netherlands of miniature glow-plug motors”. 

I’m by no means an expert on the Typhoon range. Indeed, my sole claim to any connection with the range is my possession of a handful of  fine examples of Veenhoven’s work. I’m greatly indebted to my good mate Peter Valicek of the Netherlands for his assistance in obtaining my examples of the 2.5 cc and 5 cc Typhoon twin ball-race diesel models.

When it comes to knowledge of the Typhoon range, there was no greater authority than well-known collector Tom ten Brink of the Netherlands. Over the years, Tom acquired a depth of knowledge about this range which was unmatched by that of any other enthusiast. As of 2019 when I began the research for this article, Tom was in the process of preparing a book covering Dutch model engines, including the Typhoon range. It was hoped that this book would appear sometime in 2020. Pending the completion of his book, Tom was most generous in providing me with essential background information and dates for my own article.

However, Tom subsequently lost all interest in completing this work, for reasons which remain unclear. There can be no doubt that Tom’s book would have represented the last word on the history of Dutch model engines in general and the Typhoon range in particular. As matters now stand, all that I'm able to present here is a condensed summary of the range, which should nonetheless suffice to introduce it to my fellow enthusiasts. I’ll also be presenting a few of my own tests of a number of Typhoon models.

Speaking of tests, a number of the Typhoon engines to be discussed here have been the subject of published tests by previous commentators. These tests are preserved and made generally available on the extremely useful Sceptre Flight website which is maintained by my mate Brian Hampton of Adelaide, South Australia (my own birthplace!). Given the number of these tests to which reference will be made in what follows, I’ve chosen to link them in the following text rather than download them to my own site for pasting into the body of this article.

Now on with our story ………….

The Typhoon Range - a Capsule History

The Typhoon engines were the brainchild of J. G. Veenhoven, a well-known Dutch aeromodeller who established a workshop at Keizeragracht 372, Amsterdam shortly after the conclusion of WW2. The first model engine to be produced commercially was a 4 cc fixed compression plain bearing crankshaft front rotary valve (FRV) diesel featuring a sandcast crankcase with an updraft venturi. This was designated the Typhoon Mk. 1 model. It first appeared in 1947.

1948 saw the introduction of a Typhoon Mk. 2 replacement for the above model. This was also a 4 cc plain bearing diesel with a sandcast case and updraft induction, but it now featured variable compression - a significant improvement. The crankcase casting on this model was slightly changed from that of its predecessor.

In late 1947 Ray Arden of the USA had set the modelling world on its ear with his introduction of the commercial miniature glow-plug. It didn’t take long for the new technology to cross the Atlantic, leading to the introduction of a number of pioneering glow-plug models in Britain and Europe during 1948. It’s clear that Veenhoven quickly became quite enthused about the possibilities offered by glow-plug ignition, because it was in 1949 that he introduced the first of a series of Typhoon glow-plug models.

Veenhoven’s first glow-plug design was his 4 cc Typhoon Mk. 3  model. This was in essence a glow-plug version of the earlier Mk. 2 diesel, retaining the plain bearing, sandcast case and updraft FRV induction of its diesel predecessor.

In a number of previous articles I’ve had occasion to note the fact that during the early classic era, glow-plug versions of previously-developed diesel models almost never performed up to the same standard as the diesels on which they were based. Even when an engine was designed as a glow-plug unit from the outset, there was a tendency to base its design upon standard diesel practise. The Allbon Arrow is perhaps the best-known example of this latter approach - although designed as a glow-plug motor from the outset, it was arranged very much upon standard contemporary diesel lines. Its performance failed to match expectations, quickly leading to its conversion into the famous Allbon Javelin diesel, in which guise it performed extremely well by the standards of its day, out-performing its glow-plug ancestor by a wide margin.

A few forward-thinking designers like Ken Bedford of ETA Instruments quickly grasped the fact that for best results a glow-plug motor had to be designed as such from the ground up, with diesel influence set to one side. It’s apparent that on the basis of his experience with the Typhoon Mk. 3, Veenhoven quickly came to share this view. Like Bedford, he understood that the strength of glow-plug ignition lay in its ability to allow the use of “hot” fuels at high operating speeds. There was no need to design for low speeds, as there was with general-purpose diesels - low-speed torque was never going to be the glow-plug’s strong suit.

Accordingly, from this point on the Typhoon glow-plug models were designed far more along American-influenced racing engine lines than upon European sport diesels. The first such product was the 1949 Typhoon 10 cc "Sport" model. This was a single ball-race glow-plug motor featuring a sandcast crankcase which was finished with black crackle paint. This was followed in 1950 with a twin ball-race version of the same engine called the Typhoon 10 cc "R" model. This was a true racing glow-plug motor featuring a twin ball-race shaft and disc rear rotary valve induction. As before, the sandcast crankcase was finished with black crackle paint.

At the same time, Veenhoven expanded his fledgling range to include a completely re-designed 4.87 cc glow-plug unit designated the Typhoon Mk. 4 “Sport” model. First appearing in late 1949, this continued to feature a sandcast crankcase with black crackle paint finish, but now incorporated a single ball-race. It was joined in 1950 by an all-out racing version having a twin ball-race shaft. This was designated the Typhoon Mk. 4 “R” model. 

At the same time, Veenhoven was rethinking his approach to model diesel design. At this time, general-purpose diesels represented a far broader market than the more specialized racing glow-plug models. If Veenhoven was to succeed in economic terms, he would have to cater to that market as well as the niche market represented by the racing glow-plug engines.

The initial result of his deliberations was the 1951 release of the first of several 2.5 cc diesel models to be offered under the Typhoon name. This was the Typhoon 2.47 cc diesel, a plain-bearing radially-ported FRV model having bore and stroke dimensions of 15 mm and 14 mm respectively. Thanks in part to its short-stroke arrangement, the engine was both compact and lightweight at only 111 gm (3.9 ounces).

This was the first Typhoon model to come to the attention of model enthusiasts outside the Netherlands. Up to this point, the engines had been more or less individually produced in very small numbers. Sales were initially very slow, in large part because the individually hand-made engines were very expensive compared to other makes from England and elsewhere.

However, things started to improve once the International modelling media began to cover the range beginning in 1952. Clearly anticipating this, Veenhoven took the step of introducing die-casting as opposed to sand-casting with his new diesel model. This makes it clear that he was expecting significantly improved sales figures for this offering.

The first Typhoon model to receive media attention in Britain was the afore-mentioned Typhoon 2.47 cc plain bearing diesel. This model was tested by Lawrence H. Sparey, who published his test report in the April 1952 issue of “Aeromodeller” magazine. The engine was also featured in a test by Peter Chinn which appeared in the March 1953 issue of “Model Aircraft”. Sparey obtained  0.241 BHP @ 13,500 rpm, while Chinn found a peak output of  0.23 BHP @ 12,300 rpm. By the standards of the early 1950’s, these were very good figures for a lightweight plain-bearing diesel of this displacement. Both testers praised the engine very highly.

Encouraged by this favourable attention, Veenhoven soon developed a twin ball-race die-cast “racing” version of the 2.47 cc diesel. The new design made its appearance in 1952 as the Typhoon R250 2.47 cc diesel. Bore and stroke of this model were unchanged at 15 mm and 14 mm respectively. The addition of the ball-races had pushed the weight up to 135 gm (4.75 ounces), but this was still a very reasonable figure for an engine of this displacement and specification.

This model too attracted the attention of the resident testers for the English “Aeromodeller” and “Model Aircraft” magazines. Ron Warring of “Aeromodeller” published his test report in the magazine’s September 1953 issue. He found a peak output of 0.295 BHP @ 13,500 rpm, not too far adrift of the manufacturer’s claim of 0.33 BHP @ 14,200 rpm. 

Peter Chinn waited until the November 1954 issue of “Model Aircraft” to publish his test of an updated version of the same engine. Somewhat unusually, he failed to match Warring’s figures, reporting a peak output of 0.255 BHP @ 13,700 rpm. Still, these were excellent performances by 1952/53 standards. Both testers once again praised the engine quite highly.

Meanwhile, back in the Netherlands, Veenhoven was turning his attention back to his racing glow-plug models. The first step was to apply the then recently introduced die-casting process to his 5 cc glow-plug designs. This led to the 1952 introduction of a die-cast version of the 4.5 cc Typhoon Mk. 4 “Sport” glow-plug model featuring a single ball-race crankshaft. It was quickly joined by a revised twin ball-race disc rear rotary valve (RRV) die-cast racing version, still called the Typhoon Mk. 4 “R” model. Bore and stroke of this latter unit were 19 mm and 17 mm respectively for a displacement of 4.82 cc. The racing model weighed in at a fairly healthy 248 gm (8.75 ounces).

The Mk. 4 “R” racing glow-plug model was tested by Ron Warring of “Aeromodeller”, whose report was published  in the March 1953 issue of the magazine. Warring found a few problems with his test unit (of which more below) but was generally quite impressed. He found a peak output of 0.430 BHP @ 13,000 rpm using unspecified fuel. Although not exactly earth-shaking for a 5 cc racing engine, this was still a reasonably respectable performance by the standards of the day, and one which Warring admitted was doubtless amenable to improvement.

1953 also saw the appearance of the final 10 cc glow-plug racing model, the Typhoon 10 “R” design, sometimes referred to as the “Super Typhoon” model. Understandably enough, Veenhoven clearly did not see this unit as a massive seller, since he stayed with sand-casting for the various cast components. This engine seems to have remained in production more or less as a special order item for some years. One of these engines reportedly achieved a speed of 237 km/hr (147.27 mph) at Schiphol Airport - a quite creditable performance for a European 10 cc design dating from 1953.

The Typhoon 2.47 plain bearing diesel, the R250 diesel and the Mk. 4 racing glow-plug unit also remained in production for some years. Along the way, the R250 acquired a red-anodized cooling jacket, giving it a very handsome appearance to go along with its excellent performance. However, the number of engines produced was quite small. Tom ten Brink estimated that no more than 1200 or so examples of the various 2.5 cc diesels were manufactured in total during the entire production life of the Typhoon series. Even so, these engine were by far the largest-selling Typhoon models.

During this period, Veenhoven expanded his manufacturing activities into the production of radio control equipment, offering transmitters, receivers and servos under the Typhoon trade-name. He also produced Typhoon glow-plugs.

In 1957, Veenhoven introduced his first new model engine for some time. This was a die-cast diesel unit based quite closely upon the 5 cc racing glow-plug model. It shared the glow model’s RRV induction and cross-flow loop scavenging, along with a twin ball-race crankshaft. It was a very fine engine indeed, but relatively few were manufactured.

This was capped in 1958 by the appearance of Veenhoven’s most ambitious project of them all - the near-legendary Typhoon 7 cc alternate-firing in-line twin cylinder diesel. This was an extremely sophisticated design which must have been extremely challenging to produce.  All cast components were produced by die-casting. The engine utilized a ball-race crankshaft along with rotary valve induction, also being equipped with an R/C throttle as standard equipment. In keeping with its intended use in R/C applications, the engine featured a power take-off at the rear which the maker cited as being intended to drive a vaccuum pump, vaccuum-activated R/C systems being quite popular in Europe at the time. The engine weighed in at a healthy 435 gm (15.4 ounces).

This twin reportedly ran very well, although it was never the subject of a published test. Performance appears to have been relatively modest - the maker claimed that it turned a 12x6 or 13x5½ airscrew at 7,000 RPM, suggesting good torque development at modest speeds. Given the engine's complexity, it was understandably extremely expensive. Only some 30 examples were produced in total, making this a very rare engine today. Good examples change hands at astronomical prices.

In late 1959, seeking to expand his market outreach, Veenhoven made arrangements for the Typhoon engines to be imported into England by Performance Kits. According to Performance Kits owner O. F. W. Fisher,  the models imported were the R250, the 5 cc diesel and the 7 cc Twin.  All three were still in production in 1962, but the manufacture of the Typhoon engines appears to have ceased fairly soon thereafter. Presumably Veenhoven found himself unable to compete with the high-volume manufacturers in other countries.

I have now completed this condensed historical summary of the various engines produced over the years under the Typhoon brand-name. It remains for me to present some of my own test impressions of a few Typhoon models which I am fortunate enough to own. I’ll begin with the R250 diesel.

The Typhoon R250 diesel on Test

As previously noted, this model was tested back in the day by both Ron Warring of “Aeromodeller” and Peter Chinn of “Model Aircraft”. Their reports appeared in the September 1953 and November 1954 issues of their respective publications.

Looking first at Warring’s assessment, he characterized the R250 as a “honey” of an engine, stating that it was “one of the most powerful motors in its class, and a delight to operate”. Finger-choking was the only required preliminary to an almost instantaneous start. Warring reported a peak output of 0.29 BHP @ 13,500 rpm, which he stated to be “directly comparable with any 2.5 cc design so far tested”. Indeed, his figures were not far short of the manufacturer’s claim of 0.33 BHP @ 14,200 rpm. He also praised the flexibility of the engine’s response to the controls.

Looking now at Chinn’s report, it’s evident that he had a later version of the same engine. The example tested by Warring had featured a prop driver which was threaded onto the shaft and secured with a lock-nut. This was found by experience to be somewhat less than satisfactory, leading to the replacement of the lock-nut with a set screw to secure the prop driver. Chinn’s engine also featured a hard-chromed cylinder liner.

Chinn praised the engine’s handling and performance very highly. He found its handling characteristics to be “very satisfying”. Like Warring before him, he commented particularly upon the engine’s very flexible control response. He confirmed Warring’s comment that finger-choking was sufficient for a quick start to be achieved, with port priming not being necessary at any time. In performance terms, he noted that his measured figures of 0.255 BHP @ 13,700 rpm fell somewhat short of the manufacturer’s claim, but expressed himself as being very satisfied with these figures nonetheless.

OK, how does present-day experience with this engine compare with the findings summarized above? Thanks to the outstanding co-operation and assistance provided by my mate Peter Valicek, I had a superb example of this model on hand for test. Why waste a great opportunity?!? Into the test stand it duly went!

This virtually unused example would clearly require a full break-in to deliver its ultimate performance.  Since I had no plans to fly it, I saw little point in expending the time, fuel and neighborly forbearance necessary to complete this process. I therefore elected to subject it to a few break-in runs leaning out briefly right at the end to subject the piston to a full-range heat cycle.  I would take the maximum RPM achieved during that run-ending burst as teh speed for the prop being used at the time.  This would obviously yield a level of measured performance that would fall somewhat short of the engine's true capabilities, but it would provide a reasonable basis for a ball-park estimate.

The Typhoon Mk. 4 Racing Glow-Plug Motor on Test

Once again, I am following in the footsteps of others in presenting my own test of this engine. The Typhoon Mk. 4 racing glow-plug model was the subject of another Ron Warring test which appeared in the March 1953 issue of “Aeromodeller” magazine. For those interested, this test provides full details of the engine’s construction.

Warring appears to have gone for a bit of a rough ride during the course of this test. For starters, he found that his example of the engine was unusually prone to flooding. The best approach was found to be to administer a single choked turn with the needle set at the running position, after which one or two quick flicks would produce a start.

Once running, the needle setting was found to be extremely flexible, making the establishment of an optimum setting quite straightforward. The engine was run in for some time, but here Warring displayed a certain lack of appreciation for the finer points of glow-plug operation. He stated for the record that he ran the engine in using a “large diameter propeller” at some 5,000 - 7,000 rpm - in other words, he treated it like a diesel. At such speeds, a typical racing glow-plug motor will be subject to potentially-harmful pre-ignition, imposing greatly elevated stresses upon the working components. Far better to use a prop that will allow the engine to operate near its peak on a rich needle. Warring’s predecessor Lawrence H. Sparey invariably fell into this trap as well when testing glow-plug motors, leaving a long trail of bent con-rods in his wake!!

At the end of this running-in period, Warring found that his example exhibited an almost complete absence of compression seal when hot.  How much difference a proper break-in might have made is a matter for debate ………my own example has an excellent compression seal from its two rings, hot or cold.

Warring then tried some faster props, allowing speeds of around 12,000 rpm. However, each of these runs ended with the engine seizing!  Subsequent inspection showed that the alloy piston with its two rings was perhaps fitted a little too tightly, while the aluminium alloy rear disc valve was definitely binding. To me, this looks like a consequence of running the engine in at too low a speed using too large a prop. It's quite clear that Warring's test results must have fallen well short of demonstrating the engine's true capabilities.

Indeed, Veenhoven himself evidently read Warring’s report and was moved to comment upon it in very much the same terms as myself. In a letter to Warring (part of which was published in Warring’s later report on the Typhoon R250 diesel), Veenhoven commented upon the reported low break-in speed, stating quite correctly that given the very high temperatures at which racing glow-plug engines operate at or near their peak, high temperature seizures are an inevitable consequence of a break-in at too low a speed. He stated quite openly that he should have run the engine in himself before sending it to Warring. He also suggested that breaking-in would be facilitated by the periodic injection of a few drops of oil into the intake.

Compounding the issues experienced by Warring was the fact that the prop mounting hub on this engine has a monumental diameter of no less than 11 mm!  Drilling the required hole in the hubs of many props will weaken them excessively - indeed, Warring experienced a catastrophic and potentially dangerous prop failure while running the engine at over 14,000 rpm using a small diameter high pitch speed prop. This led him to complete his testing using air-brakes in place of normal propellers. 

Despite all these problems, Warring characterized the workmanship displayed by the engine on the whole as “generally good”.  He commented particularly upon the close limits to which tolerances had been held, as well as complimenting the engine’s very fine bore finish.

In performance terms, Warring found a peak output of around 0.430 BHP @ 13,000 rpm using an unspecified fuel. He was gracious enough to admit that this performance “might well be improved under more favourable conditions”. I have to say that based on my own extensive experience with such engines, the design appears to have the potential to beat these figures by a significant amount. When we take into account the facts that there appeared to be an issue with the fit of the rings and piston in Warring's example and that the disc valve was binding, it's clear that his example performed well below the potential of the design.

However, how to prove this view?? The problem came down to that ridiculous 11 mm prop mounting hub size.  There was no way that I was going to drill out any of my standard test props to that diameter - this is the only engine in my collection that requires such a hub size, and most props won’t accommodate it anyway.

In the end, I selected a Zinger 11x10 wood prop (of which I have quite a few) sporting a pretty massive hub which I judged to have sufficient material to allow it to be safely drilled out to 11 mm. After drilling it out, I cut its diameter down to 9 inches, making it a wide blade 9x10. The maker recommended the use of speed props of 10 to 12 inches in pitch and 7 inches in diameter. I reasoned that I could always cut my modified Zinger down by increments until I had a prop that the engine would turn at my target speed of around 13,000 rpm or thereabouts. After doing that, I could fit the same prop to an engine of known performance characteristics and thus obtain the power absorption coefficient for my modified prop.

Clearly this would not be one of my more usual tests base on figures obtained for a range of calibrated airscrews.  However, it would serve as a check on Warring’s reported peak figure and would allow me to assess the engine’s operating characteristics. Far better than nothing!

The Typhoon 5 cc Diesel on Test

At last I get to present a test which is all my own!! As far as I’m aware, the Typhoon 5 cc diesel of 1957 was never the subject of a published test, at least in the English language modelling media.  I’m on my own, folks!!  Once again I have my good friends Peter Valicek and Tom ten Brink to thank for the fact that I have a fine example of this engine available for testing.

Once again, the almost unrun state of this example meant that a full break-in would be required in order for the engine's full potential to be realized. As with the R250 tried earlier, I had no plans to fly this engine, making a full break-in appear to be redundant. I therefore elected to follow the same procedure that I had applied to the R250 - subject it to a few break-in runs, leaning out briefly right at the end to put the piston through a full-range heat cycle.  I would take the maximum RPM achieved during that run-ending burst as the speed for the prop being used at the time. This would obviously yield a level of measured performance that would fall somewhat short of the engine's true capabilities, but it would provide a reasonable basis for a ball-park estimate. 

Conclusion

The Typhoon engines are quite rare today, even in their native Netherlands if reports be true. Tom ten Brink estimated that perhaps around 1,500 engines of all types were made in total over the years. Of these, as many as 1,200 may have been examples of the various 2.5 cc diesel models.

My own examination of a handful of representative examples of the engines which made up this range has confirmed that they were extremely well-designed model powerlants which were constructed to very high standards and displayed more than satisfactory levels of performance. It was only the relatively low levels of production coupled with their limited market reach that prevented them from becoming far more widely recognized than they eventually were. This was a range that more than justifies our recognition of J. G. Veenhoven as one of the more talented model engine designers and manufacturers of the classic era!

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Article © Adrian C. Duncan, Coquitlam, British Columbia, Canada

First published