17 April 1997

Mobile mill and mixing goes one step beyond…

By Andy Collings

Unlike most areas of the agricultural industry, the mobile mill and mixing business has been enjoying some good times recently. Low grain prices combined with low market prices have encouraged a greater emphasis on the use of home produced feeds.

But now Peter Rhodes Feed Services, based at Storwood, Yorks, has taken the operation further by offering an on-farm mill, mix and cubing service.

Peter Rhodes believes his company is the first to provide this facility. Using a unit designed and built by his son James Rhodes of Rhoco Engineering, the system has been in operation for only a matter of weeks, but business is reported to have been brisk.

"Straightforward milling and mixing using on-farm feed clearly has its advantages," says James. "But having the ability to cube feed appeals to a wider spectrum of stock farmers.

"Automated pig feeding systems, for example, are better able to use pellets rather than powder."

So how did Mr Rhodes set about designing and building the machine?

"Weve had a lot of experience building conventional mill and mixers in the past, so to add a cubing press into the system was a logical – if challenging development," he explains.

Six-cylinder turbocharged

"We first considered how much power the main components – the hammer mill, the press and the mixing units – would require in total. We settled for a six-cylinder turbocharged Cat engine rated at 350hp."

Then came the problem of placing these components onto a lorry chassis – and connecting the drives. The units two half-tonne capacity mixing tanks were placed at the rear of the machine – the contents of one tank supplies the cubing press, while another batch is prepared in the other.

Working along the lorry chassis from the rear, after the mixing tanks comes the hammer mill, press, engine and then the 3t capacity cooling tanks. Drive to the pelleter is off the tailshaft of the engine – split by a clutch unit – while other drives are a combination of belts and hydraulic.

In operation grain is sucked out of store and enters the hammer mill. Ground grain is then passed to one of the mixing tanks where the required additives are included. An essential ingredient to enable the pelleting system to work effectively is a quantity of molasses to help bind the mix.

Output from the pelleting unit is about 5t/hour. The mix is forced at high pressure through a die – the size of which can be changed to produce different diameters. Produced as a continuous extrusion, a "breaker" chops them to length.

"Due to the high pressure exerted, the pellets are quite hot when they leave the unit," explains Mr Rhodes. "And they are still quite soft as a result."

In the original machine freshly formed pellets were transferred to the cooling tank by an auger but this tended to cause too many breakages. The final machine employs a belt elevator.

Once in the cooling tank – and when it is full – air is forced through the pellets. "We only start taking the pellets off the machine when the tank is full to allow air to pass right through them. From then on the tank is kept full," he says.

As the pellets leave the cooling tank, shakers separate out any broken pellets which are then returned to the mixing tank to be repelleted.

"There is a price premium for this service, as you would expect," says Mr Rhodes. "For normal mill and mix operations we charge about £14/t for a 10t job. Pelleting puts about another £5/t on the bill."

James Rhodes at the controls and (below) the finished product.

Mill, mix and cube. Mixing tanks are on the back with the first auger taking the mix to the cubing press.Power is supplied by the 350hp Cat block and pellet cooling takes place at the front.