Cost Of Extraction

The extraction includes digging and loading. In ordinary brick - earth (lehm), a good digger can do 15 cubic metres per day of 10 hours, provided that he uses l'abattage; that is to say, digs below the mass to be removed, and when it only holds by cohesion, drives into the top of it, at a certain distance from the edge, stakes armed with iron points. The excavated mass falls away, and becomes lighter in falling; a few blows with the flat of a mattock make it fit to be shovelled.

The shoveller can treat 20 cubic metres in his day's work, but we will suppose that, being entrusted with the maintenance and displacement of the line, he only loads 15. Wc will take 40 centimes an hour as the cost of labour; that is to say, 4 francs per day of 10 hours.

The cost of a cubic metre of clay loaded on the waggon will therefore be 0.533 fr.

Cost Of Traction

A man of medium strength will push a waggon of .3 cubic metres at an average speed of 4 kilometres an hour on a straight road. If we lake a distance of 100 metres, we shall have:

Journey loaded

• ••••

2 mins.

Return empty...

...

2 "

Unfastening emptying, etc....

....

2 "

Total for a return journey .

6 mins.

That is to say, 10 journeys an hour; 100 journeys a day to transport about 30 cubic metres. The man pushing the waggon is paid about 3.50 fr. a day; that is to say, per cubic metre:3.5fr/30 =0.116 fr.......0. 116 fr.

Depreciation Of Plants Interest', Etc

100 metres of rails of .5 metres gauge

15 ,, ,, ,, for shunting

115 at 3 fr. 20 cems.l .

368 fr.

3 crossings „ 45 ,, .

135 "

1 turn-table ,, 60 ,, .

60 "

8 waggons of 300 litres (Fig. 9) ,, 94 ,,

752 "

Discount or rebate .

I315fr.

Total .

1315fr

Depreciation 10 per cent, per annum on 1315 fr. .

• ..

131.50 fr.

Interest at 4 per cent, on 1315 fr.

..•

52.60 „

Oil and maintenance, taken at 2 per cent. .

• ..

26.30 „

Total .

210.40 fr.

Taking 300 working days and a daily output of 120 cubic metres, the annual output would be 300 x 120 = 36,000 cm. If we suppose a less large extraction, or, as often happens, a stoppage of work in the winter for four months, we may reduce this estimate by a third, leaving 24,000 cubic metres.

In the first case, the cubic metre would cost 210.40/36,000fr. =.0058 fr., and in the second,210.40/24,000 =.0087 fr.

We will take the latter and higher price ....... 0.008 fr.

The cost of extracting and transporting a cubic metre of clay to a distance of 100 metres on a level road thus comes to ...... 0.657 fr.

If there are any inclines, the cost is at once increased, and it is better to use horse traction.

Horse Traction

The cost of extraction and loading does not change, and is always, per cubic metre . . 0.533 fr.

Cost Of Traction

A horse of medium strength, walking beside the track and pulling with a chain, can haul on a level road of .5 in. gauge 8 waggons of

1 We have liken the prices from the catalogue for September 1895 of the Decauville line and plant.

Brought forward........0.533 fr. .5 cubic metres each ; that is to say, 4 cubic metres. His speed is about 4 kil. per hour ; taking a distance of 500 metres, we shall have -

Journey loaded.........

8 mins.

Return empty.....

6 „

Unfastening, coupling and uncoupling of waggons, shunting, etc. per journey ............................................

6 „

Total duration of return journey .

20 mins.

That is to say, 3 journeys per hour carrying 12 cubic metres 30 „ ,, day ,, 120 ,,

A horse costs in food and maintenance about, per day .

4 fr.

Driver, 50 fr. a fortnight, per day.....

4 „

Total .

8fr.

Which makes per cubic metre: 8/120 = .066 fr. .066 fr.

Depreciation Of Plants Interest', Etc

500 metres of .5 m, gauge.

35 ,, „ for shunting./

535 " " at 3.20 fr......

1712 fr.

4 crossings at 45 fr. .

180 "

1 turn-table at 60 fr....................

60 "

16 waggons of 500 litres with buffers and couplings (Fig. 11), at 150 fr....

2400 "

1 set of harness for horse, with chain ....

90 "

1 horse (approximate price) ......

1200 ,"

5642 fr.

Discount or rebate .

Total .

5642 fr.

Depreciation at 10 per cent, per annum ....

564.20 fr.

Interest at 4 per cent, per annum.....

225.68 "

Oil and maintenance, 2 per cent, per annum

112.84 "

Total .

902.72 fr.

Supposing as before an annual extraction varying from 24,000 to 36,000 cubic metres, each metre will cost from 902.72/36,000 or .037 fr. to902.72/24,000 or .025 fr. we will take the higher estimate........0.037 fr.

Thus the cost of extraction and carriage for a distance of 500 metres is, per cubic metre of clay ........... 0,636 fr. that is to say, is less, for a distance five times as great, than that of man-power; but naturally the cost is greater if there are inclines. In this case, the amount carried per journey sinks.

On a slope of 2 centimetres

per metre to 3 cubic metres (6 waggons)

" 4 "

" 2 (4 " )

" 7 "

" 1 " (2 " )

" 10 "

" 1/2 " (1 " )

The cost of extraction and loading are the same, also the depreciation, and, the daily output being fixed at 120 cubic metres, we have: -

Incline of 2c.

Incline of 4c.

Incline of 7c.

Incline . of 10c.

Cost of extraction

0.533 fr

0.533 fr.

0.533 fr.

0.533 ft-

„ depreciation

0.037 "

0.037 "

0.037 "

0.037 „

„ traction

0.082 "

0.132 "

0.364 "

0.528 "

0.652 fr

0.702 fr.

0.834 fr.

I.O98 fr.

It is therefore evidently advantageous to have only slight inclines; when the slope is more pronounced, traction by cable and inclined plane must be used.