The Great Dorset Steam Fair 2018 pt1

The fiftieth anniversary of the Great Dorset Steam fair and it's a big one. 500 steam engines all gathered in one place is quite a sight. It runs through to Monday, make it along this year if you can, otherwise keep a date in your diary for 2019...

As well as steam engines there are all variety of elderly mechanical devices and country crafts on display. Here are a few images from the motorcycle tent and random snaps taken from a wander around the site.

This 1924 Zenith fitted with 350cc 'dog-eared' JAP motor is
one of my favourites in the motorcycle tent.

Binks 'Mousetrap' carb fitted to the 350 Zenith.

And the drive side of the '24 Zenith. The machine was brought
to the event by the Brooklands Museum.

Also from the Brooklands Museum this stunning ohv flat
twin Bradshaw engined Zenith Gradua. For the uninitiated
below I attempt to explain how the Gradua infinitely variable
gear system works with words and pictures.....

The gear ratio is adjusted from this 'coffee grinder'
handle on the petrol tank which turns a horizontal
shaft through a bevel gear.

The horizontal shaft is then connected by chain to
shafts inside the chain stay tube. 

As the shafts in the chain stays turn the rear axle moves
forwards and backwards on a scroll to ensure that the
drive belt tension is kept.

Obviously as the axle moves the wheelbase changes. This does
not seem to have much of an adverse effect on handling.

On the drive side of the bike there is a crank on
chain stay. When the axle moves forwards or back
this causes one rod to be one to be pushed and one
to be pulled.... 

.... which in turn works a scroll which either pushes the engine
drive pulley together or apart. The inside of the pulley is cone
shaped hence pushing it together causes the belt to drive through
a greater radius and raises the gearing. Pulling the drive belt apart
has the opposite effect.
Clear? Perhaps... a very clever system that on the face of it seems
rather complicated but in the days of belt drive and before gearboxes
were perfected it gave real world results. Zenith Graduas were competing
against single speed machines in competition and were dominant.
Such was the success of the Zenith that they were banned from
competition for having an unfair advantage. Zenith used this in their
marketing with the 'barred' logo.

1923 OEC Blackburne 550cc.

Super shiny and immaculate 1923 New Hudson
Popular Tourist model.

1914 BSA.

Foden steam lorries.

Sentinel steam lorry detail.

Sentinel steam lorry.

This Scammel is an absolute beast. Six wheel drive and massive.
It was apparently used as a tender vehicle for a Hungarian oil
field. Despite appearances it is running.

In the 'playground'.

Working hard pulling a trailer loaded with chains up the
hill in the playground.