The tower is built of good quality red brick, laid in Flemish bond. It is 24ft 6ins outside in diameter at ground level and the walls are nearly two feet thick. The height to the top of the brickwork is nearly 50ft and to the top of the cap 61ft. It is the tallest surviving windmill in Suffolk.
On the far side of the structure you may see the foundations of the engine house. A portable steam engine there drove the mill on windless days. A belt extended up to a pulley on the second floor. The sails span nearly 70ft. and are of the type known as Cubitt's Patent Sails, after the famous Ipswich engineer, Sir William Cubitt. They work on the principle of the Venetian blind, with a series of pivoting shutters all linked together to the spider, a four-armed coupling on the striking rod which passes through the centre of the hollow windshaft to the inside of the cap. Note also the fantail mounted to the rear of the cap. This turns when the wind changes direction and by means of gears and shafts acts upon a toothed rack at the top of the tower, keeping the sails facing the wind, without the need for intervention by the miller.
A plan of the mill showing the 6 floors. Note the stone floor with four pairs of stones, the meal floor, which contains the meal bins and the drive to the stones above and the bin floor housing the grain bins and the sack hoist mechanism.
Entering the mill on the ground floor you will find an excellent display on the history and workings of Buttrum's Mill. A centifugal flour dresser from another mill is stored here.
The first floor was mainly used to stack the flour sacks. There is a door to the adjoining granery. The miller's office was on this floor and a unique communications system - a speaking tube which runs to the bin floor. This must have been vital when operating the sack hoist and raising corn.
The meal floor is the heart of the mill. The wholemeal flour passing from the stones above falls into the central bins. Here the miller can exercise his skill by operating a device to control the gap between the stones and also the rate at which the corn falls into the stones. Thus he controls the quality of the flour that he is milling. Look up to see the undersides of the fours sets of millstones and the impressive gearing which drives the runner-stones. The illustration below shows the great spur wheel and the stone nuts.
Up you go to the stone floor, the 3rd floor. Here you will find the four pairs of 4ft diameter French millstones. The usual system of horse and shoe brings the corn into the stones, rattled down by the action of the damsel. The runner stones rotate at about 120rpm and weigh 750kg each. Here's a view of two of the four sets of millstones. Note that the area is remarkably small for the operation of so much machinery. The miller needed to be quite nimble and very careful.Under the ceiling you can see the iron crown wheel mounted on the upright shaft. This drove two short horizontal layshafts, operating machines on the floor below and the sack hoist above.
The fourth floor is the bin floor where the grain was stored prior to being ground. The sack hoist machinery can be best seen from here.
The top floor is known as the dust floor, as it served to keep the mill dust out of the gearing of the cap. The top of the upright shaft finishes in a bearing in the centre of the massive cap frame. The iron gearwheel on it, called the wallower, can be lowered out of gear by screw jacks to allow the mill to be driven by an engine, without turning the sails. You will remember that a steam engine had been installed in the mill in 1886. The heavy cap rotates on a numer of iron wheels bearing on a metal curb fixed to the top of the tower. The curb has a toothed rack which is connected to the fantail.
A view inside the cap, looking towards the sails. The brakewheel dominates and is mounted on the windshaft. Note in the foreground the striking mechanism which opens and closes the shutters of the sail. The striking wheel and controlling chain are on the right.
The brakewheel has 96 wooden teeth which mesh with the wallower and so drive the mill machinery. Look at the iron brake band which encircles it and was used to stop the mill. To the rear of the cap can be seen the iron striking wheel which controls the sail shutters by way of twin racks and pinions acting on the striking rod which passes through the hollow windshaft. When the shutters are closed, by hanging a weight on the chain passing around the striking wheel it is possible to make the sails self-adjusting; a strong gust of wind will open the shutters against the force of the weight and once the gust has passed the weight will pull them closed again. Visitors are generally not allowed on the outside gallery.