Page:Motors and motor-driving (1902).djvu/172

110 Gas-tight Joints.—Should a leakage of gas from the cylinder occur at the joint between the tube and the cylinder wall, it will greatly interfere with the working of the engine.

To detect if there be one, hold a match close against the joint where the tube enters the cylinder, at the same time turning the starting handle. As compression takes place, gas will be forced through any leak, and will show itself by blowing the flame of the match. If a little petrol be poured into the cylinder and the same method of testing employed, the leak will be detected by the escaping petrol becoming ignited.

It is essential that the nut which holds the platinum tube in its place in the wall of the cylinder should be kept perfectly tight, a special 'box' spanner being required for this purpose to give greater leverage.

Cracked Platinum Tubes.—It sometimes happens that the platinum tube becomes cracked, and thus allows the compressed gas to escape.

The same method as above may be employed to test this. If the tube be cracked, a new tube must be inserted, with a fresh asbestos washer. Never use the same washer twice. Care must be taken that the new tube is of the same length and quality as the old tube, to ensure accurate timing of the ignition.

Soot inside Platinum Tube.—Faulty ignition is sometimes caused by the interior of the tube becoming blackened by sooty deposit, which prevents the gas becoming properly ignited.

Take out the tube and clear the interior with petrol and a little waste or rag. If deposit still remains, use a piece of fine emery cloth wrapped round a small stick.

How to Light a Burner.—The burner must be thoroughly heated in order to vaporise the petrol before it is allowed to flow freely through it, and for this purpose small cups are provided at the base in which methylated spirits can be burnt. A small oil-can may be conveniently carried on