Power play

  • Kevin Doveton runs in one of his Stirling engines before applying its final layer of paint.
  • Image credit: Sean Woods
  • This exquisitely crafted Watt"â„¢s beam engine is another of Doveton"â„¢s one-off designs that are unfortunately not for sale.
Date:30 September 2009 Tags:, , ,

How a childhood fascination with steam engines became a life long obssesion

Not everyone gets a chance to earn a living from their childhood passion. Napier resident Kevin Doveton, obsessed by engines since he was a small boy, is one of the lucky few. Careful, focused and extraordinarily capable, he handcrafts beautifully detailed model steam and Stirling engines in his home workshop and sells them to enthusiasts who know when they’re on to something good (Catch one of Doveton’s Stirling engines in action… |click here).

On the face of it, Napier – a sleepy rural town on the road to Cape Agulhas in the Western Cape – doesn’t project itself as a hive of industry. That’s until you pop in to see Kevin Doveton, at which point your presumptions are turned on their head. This resourceful tinkerer believes in keeping busy, and his workshop, jam-packed with piles of potentially useful junk, shows it. Showing me around, he cheerfully admits that he hasn’t been able to get into the back of his garage for years.

Doveton’s healthy attitude to recycling – there’s not much that he considers disposable – hasn’t left him with much space to build his models. Then again, he doesn’t need much: his engines are rather small, and his many home-made speciality tools, designed for the myriad fiddly components that he machines, are pretty much on a Lilliputian scale, too.

To give some idea of the precision work involved in constructing these engines, Doveton works within tolerances of fractions of a millimetre.

The only standard tools that require any floor space are his pre-1924 vintage British lathe (salvaged from a local farmer’s shed years ago and “spruced up”), a drill press, a metal bandsaw and a belt sander.

Time has taught Doveton that there are serious advantages to having a wealth of useful material lying around, especially when you live in a small town. He elaborates: “Not having any shops nearby means you need to be inventive, and the more materials you have at your disposal, the more creative you can be. I even make the small knurled brass knobs, springs and chains for my models – simply because I wouldn’t know where to buy them even if they were available.”

All his flywheels start out as pieces of scrap galvanised steel tubing. After cutting the tubes into slices and removing their zinc coating to expose the bare metal, he fashions the hub and spokes. “I used to have them cast, but got messed about too much. Making them this way takes longer, but their weight is better, and I can make them up as required.” Other materials used on his models include brass, mild steel and copper tubing. Silver steel rods are used for all shafts because they are always be round and true, says Doveton, adding: “Sometimes you get what appears to be a round rod, but when you put a micrometer to it, you find it’s oval.” Old computer boxes provide the metal sheeting for the bases of his models.

Doveton prefers a single-acting oscillating valve for his steam engines, especially the ones he intends selling. He acknowledges that some enthusiasts prefer the more complex slide- or piston-valve designs, but is quick to point out that these are a relatively rare breed.

As he sees it, the man-hours and level of craftsmanship involved in the “fancier” designs makes them prohibitively expensive for anyone but a serious collector. “The average guy just wants a simple, affordably priced steam engine that he can show his kids to explain how it works.”

That said, Doveton’s choice of a simple valve system should not imply that his designs are simplistic or crude. Quite the contrary, in fact; he makes two steam engine variants – one horizontal and one vertical – that he’s named “Lady Jade” and “Jenna” respectively. Th ey work on the same principle: the brass single-acting oscillating valve plate has machined inner channels to pass steam from the boiler into the brass cylinder, then vent it from the cylinder back into the base of the funnel.

This design has a few significant benefits. As the spent, condensing steam is expelled from the cylinder and deposited at the bottom of the funnel, heat from the boiler dissipates it, obviating the usual puddle associated with these toys. More importantly, it causes the newly invigorated steam to exit realistically through the funnel while making a pleasant chuff -chuff sound.

The boilers start out as lengths of copper tubing before being cut to length. Each tube is then placed on a purpose-made jig, where all its brass components are attached using silver solder. The end caps are attached only once all the silver soldering is complete. Says Doveton: “Making a steam engine isn’t diffi cult once you know how, but you’ve got to get your procedural sequence right. For example, there’s no point in soft-soldering the boiler’s end caps on before the hard (silver) solder is complete, because it will simply burn away.”

Although the boilers operate at a pressure of only 0,5 bar, they are tested to 7 bar, and feature safety valves that are almost impossible to remove. Doveton explains: “Th e last thing I need is for a kid to dismantle the safety valve, fiddle with its inner spring mechanism, then put a blowtorch to the boiler and blow it up!” Finally, to pressure-test the boilers, he simply rigs them to a tap and waits to see if they spring any leaks.

Like many people, Doveton initially found the operating principles of Stirling engines hard to grasp. “I avoided them at first because I thought they were way too difficult, but they’re actually quite simple.”

As he sees it, the man-hours and level of craftsmanship involved in the “fancier” designs makes them prohibitively expensive for anyone but a serious collector. “The average guy just wants a simple, affordably priced steam engine that he can show his kids to explain how it works.”

That said, Doveton’s choice of a simple valve system should not imply that his designs are simplistic or crude. Quite the contrary, in fact; he makes two steam engine variants – one horizontal and one vertical – that he’s named “Lady Jade” and “Jenna” respectively. They work on the same principle: the brass single-acting oscillating valve plate has machined inner channels to pass steam from the boiler into the brass cylinder, then vent it from the cylinder back into the base of the funnel.

This design has a few significant benefits. As the spent, condensing steam is expelled from the cylinder and deposited at the bottom of the funnel, heat from the boiler dissipates it, obviating the usual puddle associated with these toys. More importantly, it causes the newly invigorated steam to exit realistically through the funnel while making a pleasant chuff -chuff sound.

The boilers start out as lengths of copper tubing before being cut to length. Each tube is then placed on a purpose-made jig, where all its brass components are attached using silver solder. The end caps are attached only once all the silver soldering is complete. Says Doveton: “Making a steam engine isn’t difficult once you know how, but you’ve got to get your procedural sequence right. For example, there’s no point in soft-soldering the boiler’s end caps on before the hard (silver) solder is complete, because it will simply burn away.”

Although the boilers operate at a pressure of only 0,5 bar, they are tested to 7 bar, and feature safety valves that are almost impossible to remove. Doveton explains: “The last thing I need is for a kid to dismantle the safety valve, fiddle with its inner spring mechanism, then put a blowtorch to the boiler and blow it up!” Finally, to pressure-test the boilers, he simply rigs them to a tap and waits to see if they spring any leaks.

Like many people, Doveton initially found the operating principles of Stirling engines hard to grasp. “I avoided them at first because I thought they were way too difficult, but they’re actually quite simple.”

Related material:
* Video: Catch one of Doveton’s Stirling engines in action
* Blog: "Celebrating the ingenuity of the human condition" by Sean Woods
 

Latest Issue :

Jan-February 2022