THE COMMERCIAL MOTOR
Page 17
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Opinions from Others.
A Benz with .a HaIlford Bonnet.
The Editor, THE COMMERCIAL MOTOR.
[1388] Sir,—I note in your issue of the 4th February, under "Despatches from the Front," your correspondent writes of "A Hanford with a Benz bonnet," and goes on to say that. the Hanford was fitted with a German body and that the bonnet was from the German vehicle. I should be glad if you would insert in your valuable space that the vehicle referred to was captured from the Germans at the start of the war. It is a Benz this has a large covered body, with all sorts of German signs on the side, which I am afraid I do not understand, but it is a most useful lorry for rations, which is its employment for the battery. Where your correspondent makes the mistake is that the Benz radiator got far beyond repair, and, as we were unable to obtain a Benz radiator as a substitute, we replaced it with a Hallford, which was all we had at the time. It does present a very curious appearance as the bonnet is about 4 ins, higher than the radiator. This lorry, bar a big-end running, has worked day after day for five months without saying no.—Yours faithfully, 0.0. MO SIEGE BATT. AIM. COL.
Do Hydraulic Presses Damage Tires?
The Editor, THE COMMERCIAL MOTOR.
[1389] Sir,—We have read with much interest the article entitled "Tires That Don't Wear Out" in the COMMERCIAL MOTOR, Vol. XX, page 430. It interests us because of the clear proof that many tires fail long before their value has been obtained, due to breaking away at the root. [Our correspondent was writing of tires at the Front only, it will be recalled.—En.] We contend that this is largely due to initial damage in the nature of a rupture of the hard vulcanite root solely through the use of the hydraulic press. Tires are pressed on to wheels with a pressure that varies between 50 and 120 tons. The bore of the embedded steel band in tires is, as a rule, from in. to in. oval (due to dumping from railway trucks, etc.), therefore, when being pressed on to the wheels which have been purposely made larger in diameter than the bore of the steel bands, the limn& are forced to become circular and are also expanded. This causes a wave of fracture at the juncture of the hard vulcanite and the steel band.—Yours faithfully,
THE 'CHEERY WHEEL CO.
Floating or Semi-floating Axles?
The Editor, THE COMMERCIAL MOTOR.
[1390] Sir,—In reading over your description of the Chase truck on page 436 of 11th February issue of your paper, I find that you rather criticise the semi-floating construction as shown on this particular model. If you will refer to the " Automobile " (an American paper), of 20th' August 1914, you will find an article there which goes rather thoroughly into the relative merits of the semi-floating as compared to the full. We always figure that an axle never fails through straight rolling loads, but always from the side blows at the rim of the wheel. On the full-floating type these reactions are taken on ball or roller bearings usually placed too close together, or on a plain bearing of inadequate length which puts tremendous pressures on the tubes supporting them. [We know of many axle fractures which have occurred through other than lateral blows through rims.—En.]
In the semi-floating construction, where the combined bending and torsion is taken care of and drive shaft is designed properly, there is no more danger of breaking this shaftl‘than in the case of locomotive practice, and in case of breakage through striking rbs, or any accident, the shaft can always be replaced muchlvinore easily than a broken tube.
Again, this type of axle is so very much more' easy on bearings. The reactions are taken on very inuch wider centres, and the dynamic loads on the bearings are about 11 times the static on the semi-floating, as against from 4 to 6 times the static on the full-floating type, deriending, of course, on the spacing of the bearings. The semi-floating construction has been very 'much abused in the -past.in cheap pleasure-car construction where the torsion has only been taken care of, forgetting abSolutelY the bending moment beneath the spoke line. Where this is taken care of adequately, it is by far the most satisfactory axle, particularly for heavy duty. [This is the principal point to which attention has been given.—En.]
Where ball or roller bearings must be used in the full floating type under very heavy duty, the hub becomes so large that, on the 36-in, wheel diameter, 'there is very little spoke left, and unsprung weight is certainly a factor in the heavier types of commercial 'vehicles, and it is difficult to get a lighter construction where great strength must accompany light design. It is already agreed by certain engineers that the full floating type of axle is a relic of the horse-drawn days, while the semi fellows locomotive construction and is a thorough engineer's job. Having in mind always, as I said before, that axles never fail through straight rolling loads, but,always from the side blows delivered at the rim of the wheel.—Yours faithfully, AarwuR M. LAYCOCH. [We are not in agreement with our correspondent, nor are many other engineers, as regards the relative merits of the semi-floating axle as compared with the more modern construction, the full-floating type. Nor does our experience enable us to concur with him as to the more usual cause of failure of such axles. His criticism of the latter type can best be met by a reference to the policy of established makers in this country, who have, with few exceptions, adopted it after trial of the other.—En.]