The Shed - Engineering

Race cars made in NZ

31 July 2025

Craig Greenwood is one of the best examples of someone who turned his passion into a business. He is also one of New Zealand’s most prolific racing car builders.
Craig got into motor racing in the early 1990s, progressing from competitive cart racing to Formula Vee (now Formula First). The class is based on a 1200 cc VW motor and uses a collection of stock parts to form a competitive car from the engine, transmission, front suspension, brakes and wheels built into a space frame.
The body is fibreglass or carbon fibre. It’s a racing class that allows an enthusiast to build and maintain his own car. Craig bought his first car but soon decided to build his own, working nights and weekends in a cramped single garage with little more than an oxy-acetylene welder, a hacksaw and a hand-held drill.
“I wasn’t all that successful at first. Of 18 starts I made, I only finished four,” says Craig.
“I realised that just knowing how to weld a chassis wasn’t enough, so I started to read about designing and building race cars.”

Hand tool grand slam

24 April 2025

It splits wood and rock, it severs roots, it levers…it slams. The Slammer may be a literally ground-breaking tool to work with, but the manually operated device is a rare creature in the thriving high-tech landscape of new DIY tools.
Developed by TJ Irvin, a globe-trotting American who settled by Lake Hawea more than a decade ago and handcrafted by one of the oldest engineering firms in the country, Templeton & Sons, the Slammer is an unusual piece of kit any manual worker needing a bit of extra grunt should consider trying.
The 9 kg, two-piece Slammer developed by Irvin uses the impact of a solid, high-tensile steel rod rammed down a length of pipe by the operator. This provides the momentum to ram the attached blade into—and through—the sort of material most people hire a jackhammer to deal with. Other attachments turn it into a fence-hole rammer and a compacter for foundation work. As TJ describes it, the slammer/rammer multipurpose tool is a combination of a crowbar, axe, spade, mattock and sledgehammer all in one. Made in New Zealand.

Man who gives a toss

21 March 2025

The incentive for the project came from Dave’s sons, Josh and Andrew. The boys were jumping their bikes and Josh (13) came up with the ultimate idea—throwing their bikes with a trebuchet which they had seen in action on computer games. The boys started with a small trebuchet using stones but it didn’t throw them far so dad got into the act. Dave checked out machines on the internet that were even throwing cars. The world record is a 630-metre throw. He was impressed and thought he would give it a go. He had some Lawsoniana trees he intended to drop so thought now was the time. He finds the Lawson trees were straight and the wood is very flexible.

The great Greek gear train

28 February 2025

Many years ago in a history of technology, I read a passing mention of a strange artefact, a piece of mechanical gearing, that was in the Athens National Archaeological Museum. I didn’t know then, but getting to see this would become an obsession in my life.
The artefact was recovered in 1900 from an ancient Greek galley. This ocean-floor wreck was accidentally discovered by sponge fishermen sheltering from a storm by the tiny island of Antikythera. One of the artefacts later taken from the ship was a corroded block of copper which, after it was cleaned, revealed the vestiges of a complex gear train. This has come to be known as the Antikythera Mechanism.

The Shed King is going to Bonneville, can you help get him there?

26 February 2025

“My name is Dave Alexander, and I am on a mission to set a land speed record of over 420 kph at the iconic Bonneville Salt Flats.
With decades of experience in motorsport dating back to the 1970s, I have had the honour of competing at Bonneville before, where we achieved three records in just one week with my home-built car from New Zealand.
My latest creation is an impressive 7-metre ‘Lakester’, engineered specifically for land-speed racing and powered by a turbocharged Nissan RB30 engine. As a self-employed engineer, fabricator, and welder, I took on the challenge of building this vehicle in my shed with support from a small team of skilled friends.
In February 2025, we successfully completed the build and ran the car on a hub dynamometer, ensuring all systems were calibrated and functions tested. This marked a crucial milestone in our journey. Now, we face the next challenge: packing the car and transporting it across the globe to compete in ‘Bonneville Speedweek’ 2025.

My car the barbecue

13 December 2024

A mobile barbecue built out of an abandoned Holden Statesman? Why not. This clever conversion by Scott Edwards, a former freezing-worker-turned-motor-mechanic, was the pin-up attraction at a car, bike, truck and boat Show Day held in Riverton, the popular coastal resort town about 32 km west of Invercargill.
Scott is currently completing an adult motor mechanic apprenticeship but has always had a flair for anything to do with engines. He began early. Scott’s partner, Nicola Swain, says his mother had told her that Scott pulled apart every toy he got as a child, then put them back together again to see how they worked, before he played with them.

Getting up to speed

11 October 2024

As sheddies, we are known to cobble together machines from whatever we have at hand. More often than not these items are less than ideal and a motor of some sort may run at a different speed to what we need. If we are looking to make a spindle moulder, belt sander, garden chipper, wind generator, compressor or similar item then it is likely that some sort of gearing will be necessary to give the right RPM at the business end.
Calculating the sizes of gears, sprockets or pulleys is a relatively simple exercise. Below is an easy reference to save having to work it out from basic principles each time.

Along for the ride

16 August 2024

Every Wednesday and Saturday morning about 20 retired tradesmen leave their lunch boxes in the Oamaru Steam and Rail smoko room, shrug themselves into their overalls, and head for the old railway workshop to get on with the day’s tasks.
They might be restoring turn-of-the-20th century railway carriages, stripping down a locomotive or installing wiring systems. Each man brings a lifetime’s worth of skills and the willingness to learn something new.
They work out of the old New Zealand Rail wagon workshop, or lifting shop as it was called, at the back of Oamaru’s historic precinct. The Oamaru Steam and Rail Society Inc took over the building in 1989. Most of the tools and equipment needed to complete the volunteers’ first major project were on hand so they rebuilt the 60mx12m workshop which had been partially demolished by NZ Rail when they decamped.

Ponoko—a cut above the rest

25 June 2024

While laser cutters are now practical for home-build projects, they are not something that everyone will want to run. They take up bench space, need care and feeding, get expensive in large calibres, and if you don’t use one that often you might well be better off letting a company like Wellington-based Ponoko cut things for you.
Ponoko stock a wide range of materials and are experienced with using their laser cutters on them. Handy, but scarcely unique given the number of engineering outfits that are out there that’ll do pretty much the same thing.

Making a kayak anchor

13 June 2024

This simple and effective rebar anchor is perfect for small boats and kayaks and is the result of welding $30-40 worth of materials. If you are a small boat and kayak enthusiast, fabricator or just want to learn some new metalwork skills, this two-hour project will be great for you; it needs few welding skills. Remember that the construction is modular and can be made to fit your needs.
With a net weight of only 7 kg, the anchor will not weigh down a boat or kayak. Anyone can pull it up, but it will still catch the seabed.

Frozen in time

7 June 2024

I just love nosing around other people’s workshops to see what they are making and what gear they have, and I’ve just had the special opportunity to look at a manufacturing workshop that was about to be sold up and, as a bonus, learn about its history.
Macdonald Refrigeration surely has a place in Auckland’s heritage as a pioneer in its field. The factory has been closed for some time now and it has been hard for the family to let go of all the gear, but it is filling a lot of valuable space.

The right stuff – part 2

2 May 2024

If you have followed our Metalworking Lathe 101 series in The Shed magazine, you will have a grasp of the basics, so here are some helpful tips to improve your lathe experience and make those projects a bit easier to do.
Quite often the material or item we need to hold in the chuck is delicate, either due to a fine finish that we do not want to put chuck jaw marks on or due to it being thin walled. For jobs with a surface finish that you need to protect it is handy to have some strips of aluminium to put between the chuck jaws and the job material. These are mostly used when holding in a 4 jaw chuck as the job will need to be “clocked up” using a dial indicator to get it running true.
The thickness of the aluminium strips cannot be relied on to be consistent as they squish up a bit with the tightening of the chuck jaws, so when using a 3 jaw chuck the auto centring effect is not so good.

The right stuff – part one

18 April 2024

These tips are a random collection of thoughts that I have grouped under the classification of things that relate to working at a bench using hand tools, rather than using a lathe, mill or other machine tool. So if you have only a workbench with some hand tools in your shed, this is meant to be useful for you too.

Metal spinning lives

12 April 2024

The exact origins of metal spinning are unknown but the craft can be dated back to ancient Egypt where examples of spun vessels have been found. Metal spinning today differs little from the past with the only real advance being that an electric motor is used to drive the chuck instead of manpower or water power.
Before the advent of power presses, metal spinning was used to make almost all round sheet metal objects such as pots, pans, lampshades and wheel rims.
The principle of metal spinning is simple: a disc of metal is clamped between the tailstock and a former or mandrel. The disc is spun and the operator then uses a lever to manually work the metal down onto the mandrel. The process helps maintain the structure of the material and does not stress it, resulting in a stronger and more stable product than if it was pressed.
While metal spinning by hand does not generally alter the thickness of the material, hydraulic-powered tools can be used to flow-form products making sections thinner where required.

Rolling stool build

4 April 2024

My wife, Rosaleen, loves to cook, and will happily spend an afternoon in the kitchen cooking meals to be frozen and given to our daughters and their friends whenever the need arises or opportunity presents.
However, arthritis makes standing in one position for long periods difficult for her. She wanted a stool for the kitchen, but ours is a galley-style layout and quite narrow. It’s wide enough for one person to walk past another working in the space, but the presence of a stool would present a major obstacle. “Why don’t you invent something?” she said.
I love a challenge like that.

Engineering