NAMING OF PINS

I’m afraid a couple of your correspondents have been misleading us.

Firstly Neil Cairns in RC240 insists that split pins are not cotter pins. Cotter pins are indeed those with the angled face, used for fixing bicycle pedals, kickstarts and the like, it’s true. But the pins colloquially known as split pins are properly known as split cotter pins. See the British Standard BS 1574 ‘specification for split cotter pins’ for example. The word cotter applies equally to both types.

Secondly Tom Gaynor talks about horsepower. 1PS is not equal to 1000 Watts. It is equal to 735.5 Watts (rounded to four significant figures) and is therefore very close to 1HP at 745.7 Watts (to four figures). The difference is only about 1.4% so for most practical comparisons they can be treated as pretty much interchangeable (ie. 1PS = 1HP to a close approximation). The real accuracy with which an engine’s output power can be measured is probably no better than + or 1.4% anyway.

Great magazine, read avidly the moment it arrives each month so please keep up the good work.

Ben Lang, member

I thought I knew the difference between cotter pins and split pins until my dad gave me this tin many years ago. Who could argue with the maker of the famous Aero Springs? Could the variations in nomenclature be regional, like sinks and basins?

Oilybootbob, member

It must be a regional thing because I have been in engineering all of my life and a split pin is as described and a cotter pin was a tapered pin with a spigot containing a nut aka cycle crank.

Chas Stickley, member

A cotter is a pin, whether retained by a nut or by being split. Does this help? BS 1574 refers to ‘Split Cotter Pins’.

Richard Payne, member

I agreed with Neil Cairns about the naming of pins in RC240. I think he is a bit dismissive of the railway engineers for still using the term ‘cotter pins’ for split pins – they are supported by no less than the illustrious firm of Guest, Keen and Nettlefold, who actually made the things. This picture is of a tin of split pins which I inherited from an uncle who died about 30 years ago. He was a professional mechanic until the mid-1970s and that tin must be at least 50 years old. It shows clearly that when it was produced, GKN were still referring to split pins as cotter pins.

I suppose that the term split pins was originally introduced to differentiate between and prevent the confusion which probably did occur with the cotter pins as described by Neil, although when that actually happened I have no idea. In large organisations such as the railways, where apprentices learned from older employees and all of the older technical literature would still refer to cotter pins, then the terms are not likely to get changed very rapidly… at least not in general use amongst those directly involved.

Colin Atkinson, member

Just to cheer everyone up, AJS & Matchless used ‘cotter’ pins to retain the swinging arm spindle. Pic here. Never attempt to remove them using a hammer…

Frank W

In next month’s inciting episode: duct tape / duck tape, why an A10 is a Golden Flash but a DBD is a Gold Star (and not a Goldstar) and is a swingarm really a swinging fork? Oh. The thrills. Rowena

The Kempton Park Classic Bike Show and autojumble returns on Saturday 11 May with the biggest-ever show and autojumble at the racecourse. The one-day show will host more than 350 trade stands, 120-plus classic bikes and displays from all the key classic clubs. Then there’s the special guests – a new feature for Kempton.

First up will be rotary Norton guru and race team manager, Brian Crighton. Alongside his stage talks, Crighton will bring his all-new rotary race bike, the CR700 for all to admire. It’ll be started during the day so you can see – and hear – the rotary’s unique audio effects.

The second star of the show is Gordon May, author and adventurer, who’s well-known for his epic adventures on old bikes. During Gordon’s overland to India trip in 1988, he travelled 5000 miles on his Royal Enfield Bullet, two-up, loaded, and the bike never missed a beat! May will be on stage talking tales of his trips across Europe, the Middle East, Asia and the Americas.

Last but not least, Kempton Park Autojumble founder, AMA speed record holder and all-round die-hard classic bike enthusiast Eric Patterson will take to the stage. Eric will be talking about his exploits on the Bonneville Salt flats as he chased down land speed records on his Brough Superior.

There will also be a range of awards for the best bikes on display, the ‘sounds of yesteryear’ in the start-up arena, refreshments – and all the new, used, NOS and really rare spares on the jumble stalls.

Gates open 9.30am and advance tickets cost just £6. Parking is free at TW16 5AQ, just off the M3 and outside the ULEZ Zone. See kemptonautojumble.co.uk

Herefordshire on the Edge takes place on Sunday 30 June and for just £8 offers VMCC members the chance to enjoy a unique event exploring the stunning countryside around Hereford. This non-competitive challenge is restricted to motorcycles and three-wheelers made before 1999, and is organised by the Herefordshire and Midwales section of the VMCC.

Entrants can start at either Ross-on-wye or

Leintwardine and must plan and then follow a route to visit as many as possible of the 28 designated waypoints spaced at intervals in and around the borders of Herefordshire. Riders might find themselves on an old toll bridge, or crossing the Wye near Ludlow Castle. For the more adventurous, four of these waypoints have an optional location on non-damaging unsurfaced legal rights of way. These are passable on road tyres.

In 2023, 110 machines represented by 29 different marques were entered, including some rare and beautiful models. Rick Stevenson’s 1954 Guzzi Cardelino was the smallest capacity bike to be awarded a medal in the event’s history, while the oldest to take part was a 1928 Ariel. This really is an event for vintage and classic machines of all types and sizes.

Regulations and entry forms at herefordmidwalesvmcc.org