HINTS ON MAINTENANCE.
Page 66
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Renewing Dennis Valve Guides. Peerless Hints Required. Fitting Piston Rings. Salving a Fiat Axle and Torque Casing.
Fitting Dennis Valve Guides.
When it is found necessary to fit Dew valve guides to the 105 aim. and 115 mm. bore Dennis engines, a great saving of time can be effected, especially In the case of units where it is perhaps only necessary to fit one or two guides or where it is not desirable to remove the cylinders, in the following manner :— Remove the plinth plates, then the inlet pipe and carburetter as a unit, also the nuts securing the exhaust manifold, and then, without detaching any part of the exhaust pipe, pull the manifold away from the cylinders. Remove the 'valves and springs, and, through the valve ports, groove the heads of the guides by means Of a chisel, afterwards giving each guide a sharp tap with a fairly heavy hammer through the medium of a bar. By this means it will be found that the heads will break away cleanly and easily.
Having removed the heads, use can be made of a special punch consisting of a fin, diameter bar reduced to in. for a length of 2 ins., and by this each guide can be punched downwards in turn. New guides can now be fitted from the top. For this purpose another punch will be required, this having an upper portion of in. diameter to suit the heads of the guides.
It is claimed that by this method a complete set of new guides can be fitted and the valves reseated and ground in 4? hours.
Peerless Advice Required.
One of our readers states that he has had considerable trouble with overheating on Peerless engines and wishes to know of any means which can be employed for obviating said trouble.
Another inquirer is anxious to know if there be any method whereby the double screwed end collar which couples the selectors and the change-speed rods together can be prevented from stripping its threads.
• We would, therefore, welcome useful hints on these matters.
Preventing Piston-ring Leakage.
Upon lifting a cylinder block it is often found that the piston rings, instead of being in their position as when fitted with the gaps equally spaced around the pistons, have worked round until the gaps meet and form a break from the top ring to the bottom, thus forming a direct path for the gases, this giving poor compression and back pressure in the crankcase with all the inconveniences which result from these, such as bad starting, poor acceleration and oily plugs.
The explosion forces a small amount of gas through thegap of the first ring, and, this being at an angle, c44
Repairing a Fiat Axle and Torque Casing.
As is well known, the 1-ton and 30-cwt. model Fiats have a special axle casing which also forms a torque tube, which is in the form of a T made of pressed steel held together by numerous bolts. Two ends of the member fit over sleeves for the wheels, whilst the remaining end has a sleeve which, in its turn, is an easy fit in a Y-shaped suspender, which is hinged to a cross-member by means of two of its legs and supports the front end of the T tube. The hinges allow for vertical movements of the rear axle, but when one wheel is raised above the other the necessary movement is provided by permitting the forward sleeve to turn inside the Y.
Sometimes, owing to neglect, this sleeve rusts up, with the result that the front end of the casing cracks at the point where the sleeve enters.
To replace half of the casing would involve considerable expense, and the following repair has been tried with successful results:— The halves of the case being completely dismantled, two pieces of sheet steel of the same thickness as the case were shaped to fit inside the halves and to extend a suitable distance from each side of the cracks, there being plenty of clearance for the cardan shaft. Quarter-inch steel rivets were used for holding these patches and these were completely brazed. The axle unit was then reassembled, and found to be quite satisfactory.