OVER OR UNDERTYPE STEAMERS?
Page 4
Page 5
If you've noticed an error in this article please click here to report it so we can fix it.
By "The Inspector."
WITH PERIODIC4L REGULARITY certain topics crop up in technical papers devoted io our own industry, just as others do year by year in the columns of the daily Press. War condis tiona have, of course, ousted some of the More hoary varieties ; the giant vegetable marrow, the first cuekoo, the sea serpent and other happenings of immense import having yielded pride of place to yet more momentary chronicles. In the commercialvehicle world aubjeets asf this kind include : "chain versus live axle " ; " steam against petrol" ; " tram versus motorbus," or similar contentious matters. Judging by what the Editor tells me, another old friend is at present agitating a certain section of the public to which the " C.M." appeals. Fresh records are being sought as to the respective merits of two accepted types of steam wagon, viz., the Foderi and its copies, and the undertype. There are, of course, others.
The subject, discussed at length in the past, has apparently been reopened by a somewhat dogmatic and, I suspect, a little prejudiced article published in the house journal of the makers of the Alley and MacLellan undertype steam wagon. I have read this -effusion,. and the Editor has shoWn me a number of expressions of opinion that have reached him in favour of the other type. I may claim to know something of both ; it may not be disagreeable to my readers if I set down, wifh as unbiassed a pen as I can command, the case summed up after both sitles
have been heard.
First of all achievement to date must certainly be accounted as reputable evidence of satisfaction, and herein we find the Foden and its prototypes outnumbering all other steam-wagon types, it may be, by at least ten to one. I have not the figures, but that is a perfectly safe estimate. Of eight makers producing the Foden type to-day three at least gave up the. undertype to do it. In addition, I can count no fewer than 18 British-designed steam wagons all embodying the essential features of the undertype, Manufacture of all of which has long ceased. Arhongst the better known of these u-ndertypes, a few of which were abandoned for reasons other than for essentially bad features in their designs, I recall the Thornycroft, Straker, Garrett, Coulthard, Savage, Hindley, St. Pancras, Hercules, Allehin, Londonderry, Yorkshire, Hay, Jesse Ellis, Thames and others; the Purrey-Exshaw was a Frenchman.
That is a sufficiently formidable list. Against it I know of no failure wifh the engine-over-boiler type. At present the Sentinel is the only -undertype being manufactured on any scale, the Leyland Co. having interrupted the production of their successful under-type owing to their preoccupation in Army petrol lorry work ; the Atkinson is quite a new corner.
• There is also the Shep pee. *
What has become of Alley and MacLellan's own overtype, produced as an alternative to their unique and origirsal undertype machine? I remember it created quite a stir when it first appeared a year or two befote the war. It was distinguished by several Unusual features. It had the engine in the Foden position, but the boiler was exceptionally large and embodied a special round firebox. Are we to assume that the article in the "Sentinel News" for August, at17. is a formal announcement that the Shrewsbury factory abandons its overtype alternative, or is it to be considered only as the individual: expression of opinion of a 'valued contributor "I In any case,
B2
there was evidently a period, not so very long ago, when even the Sentinel builders were not convinced as to the unsuitability of the Foden type as to "speed, load, handiness, ease of steering, driver comfort, clear vision, safety, axle weiget, quietness and
interchangeability."
-Now I am .fairly well informed as to the real facts dankly hinted at by the Sentinel contributor in his letter in the last CM." issue, of these " experiments' being carried out by well-known makers," as also do know something of the deliberations of London and other police authorities as to their future interpretations of the Use and Construction Order and. other limiting. regulations. But he is beside the mark in suggesting, as he does, that the Feclen as a general type is likely to disappear. He is generous enough to suggest that the Sentinel need not be the new mode, excellent alteraative as it is ; there are, of course, any number of variations available to the designer if he be forced to provide, for certain service, a machine which will give a better driver's view than does the overtype.
If there be a weak spot in Foden design, it is admittedly the obstruction of the effective vision of the driver due to the interposition of the high-hill engine on the boiler-barrel in front of him and between him. and the road -ahead. There the undertype very considerably scores. There are advantages and disadvantages to both of these broad types, but it has to be borne in mind that no mechanical device, as indeed any production of man, is at its best more than a relatively clever compromise. It may be useful to endeavour briefly to state the case for and against the classes of design represented by the Foden and the Sentinel respectively.
It is claimed against the Foden type that the coma fort of the driver, his vision ahead and general control over his machine, are impaired by the arrangement of the boiler and engine. To this argument I have already conceded that there is certainly room for improvement. As to.speed, I am of opinion that other conditions being equal, it would be a fast overtype that could catch a well-conditioned rubber-tyred Foden. I would as soon handle a Foden as a Sentinel at all speedssanctioned by the law. Criticism of chain steering is met by the adoption of the Ackermann type, successfully I presume, in the Aveling and Porter overtype three-tortner of camparativelyareeent appearance. Many drivers, too, claim they are safer with the sack of a chain steerage than with the relatively stiff Ackermann or similar arrangement, even at reasonably high speeds on a loaded steamer. I remember a law case wherein the judge ruled that the slack of chain steerage was a necessary provision on a steam wagon.
I can find no argument of any moment in the statement that the overtype precludes "handiness, safety or interchangeability of parts." The universal employment of the overtypes for all classes of warehouse and general transport -work confutes the first suggestion. As to the second, surely the type is particularly free from accidents in operation. As to exactly what relation the third " drawback " has to the type of machine, I am afraid T ant uninformed. The Foden has a long pull with regard to accessibility.
Taking the Sentinel as the example of the rival design, I readily s,gree to the claim as to more effective distribution of weight, as -to the avoidance of overhang and the shorter wheelbase. The enclosed
engine makes for quietness and for ease of lubrication; it also makes for inaccessibility. It is a distinct disadvantage too, to have to employ jointed steam pipes of considerable length between boiler in front and engine below the middle of the frame. The engine, from a heat-economy point of view, is certainly better off on the top of the boiler, steam-jacketed, than separately slung' below decks."
Finally, there is the not negligible factor of prime cost. If the undertype is to become as popular as the overtype, it will have to cost little, ifany, more. Both types are sound British pateductions, and both are successful compromises. That considerable modifications are under investigation by well-known makers agafiast peace-time productions is not, nor need it be, a secret. But that the overtype is doomed to be superseded I cannot agree. Remember, there are other overtypes than the Foden, such as the Yorkshire, and particularly. the Mann, with the engine in the boiler and the driver at the side. Sonic years ago there was a keen discussion as to the relative merits of the bonnet and the engine under the driver's seat on petrol chassis. There are few enough designs in England or America to-day ; there are more in France, of course, in which the retention of the bonnet has been hindered by the longer wheelbase and the smaller platform area. The same considerations will, it is to be presumed, carry weight in the ease under review.
I should like the" Sentinel News" contributor to say, if he can, what factor induced Alley and MacLellan to design and build the Sentinel overtvne until quite recently?