SOME IMPRESSIONS OF AN UNCONVENTIONAL FRAME.

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36

SOME IMPRESSIONS OF AN UNCONVENTIONAL FRAME. THE DUPLEX STEERING O.E.C.

By E. B. N.

Iordered the model in question last Show, greatly against the advice of my friends–technical and otherwise—who told me that it wouldn’t steer; that it ran out of track ; the hind quarters were always off the ground ; with the aforesaid result—.1 ordered one.

It was delivered to me at the end of last January, and since then it has moved about 4,000 miles—ioo miles a week regular—to and from work, in all weathers and an odd jaunt or two up to Town or the Track on the week ends.

I got the bus about six o’clock one Friday night, fitted it with a flash lamp and rode it straight from Coventry to Twyford non-stop, a distc.nce of 83 miles, on a frosty—a very frosty—night.

The manhandling of the model is somewhat difficult at first, owing to the balance and one or two of my experienced friends promptly fell over it on first trial ; but it becomes simple after a day or two. The lock, which is not all that could be desired when foot slogging, becomes ample when riding owing to the ease with which the machine can be heeled over to any angle. I can ride round in an 18 feet circle, which is more than sufficient for any town or hairpin. The lock can be greatly improved by replacing the large valenced guard for a sports type guard, as the large guard restricts the movement.

To continue, directly I got going on the road the superior steering at once became apparent, and let me say now, once and for all, I shall never, never go back to the old 6 in. length single head perched above the front wheel, flexing and wobbling at the smell of a pot hole or corner ; the steering is excellent and honestly and truly, I couldn’t ask for a better, and all who have tried it have enthused on this point, and agreed With me. My first experience of a skid was on the aforesaid night when taking a corner slightly faster than the surface considered decent. The tail started to swing outward and I pursued a diagonal course round the bend, but to my amazement, the model just straightened out and continued on without the suspicion of a wobble or •

reactionary skid. All the time I have had the bus, I have never had a wobble, in fact, it can’t wobble ; you can ride along hands off and punch as hard as you can either end of the bars and simply nothing happens, the bus just ” shivers” and goes straight on. As far as skid cornering is concerned it is great ; one can go round a dusty corner in a front wheel skid, just like a car, and provided you don’t try to correct it by straightening out in a hurry it simply takes grip as the corner is rounded and one continues on as I have already said without any wobble. There is a left-hand bend I go round every morning on the way to work which can be taken at 40-50 and necessitates the model being leaned over to an angle

of about 45°; the front wheel completely ignores halfa-dozen pot holes on the corner, and the back just moves two or three inches to the right over each hole and that is all! I tried some broadsiding on a cinder track the other day and provided the back wheel is kept revolving the

model goes round the circle definitely in a real broadside with the front wheel on the opposite lock, until you wear your left shoe through or it comes off, as mine did! A rumour is abroad that the model will not steer at slow speeds ; to disprove that statement I am often having” slow” races with my critics ; I can beat them, or at least they beat me, by yards in about 20 yds., or they subside. I sometimes find some slight difficulty

in manoeuvring round the Arm of the Law when they stand on the far corner and make you go round them to turn right, if you know what I mean. As far as pot-holey roads are concerned, they can be traversed at any speed you may choose, even the wheel buckling variety, and except for sundry Ford-like noises in the interior (of which more later), one continues blithely on without any wobble or uncertainty whatever. There is a certain amount of back wheel bounce over rough roads, only noticeable by the spasmodic revving up of the engine and the consequent loss of speed, but I think this is entirely a case of riding position; you see, you can’t have your cake and eat it, so to speak, and to obtain a low riding position with

the consequent low c. of g., the saddle must be placed forward to miss the rear wheel, and to keep the rear Wheel on the ground, you must sit on top of it to keep it down. Hence, the track racing position. N.B.—I have dwelt rather lengthily on the steering and road holding capabilities of the model as these are

undoubtedly its most interesting and unique features ; but let us now disintegrate the model and examine it in detail from the mechanical and technical points of view.

Starting at the forward end, the 27 x 2.75 Dunlop all-Rib shows no appreciable wear even for 4,000 miles which speaks well for the tyre and the front springing arrangement of two barrel springs accommodated in the two front tubes ; these could be slightly stronger and I am thinking of fitting a Hartford from the hole over the off-side spindle-rest to the tube above, to counteract an occasional pitching. The forks are attached by four flat links to a similar fixed rectangle on the frame as shown in the accompanying photograph. En passant, it would be better if these links were braced vertically or made T-shaped as the strain is vertical rather than horizontal. Thee links work in cu’ps and balls, which must have been made of very inferior steel as they have now worn “

flats” in the vertical position and made the steering come out of the straight with a jerk. I am replacing them with Timken Taper Roller bearings. The tank, such as it is, is a wierd and Heath Robinson looking contrivance, precariously suspended by thin strips from the duplex top rails and a small quart oil tin stuck in the top which rattles on the tank at every opportunity. The whole, and a lot more, is covered by an enormous tin canopy, which covers a multitude of sins, and doesn’t fit and does not go far enough down the front to cover the mess of strips and petrol

tin, which, by the way, holds gallons. The general effect, when viewed with any scrutiny, is far from pleasing.

The engine, an excellent job (of which more later), is suspended by (Cod forgive them) 3/32 engine plates ; the front plates, or rather wafers, are suspended in turn by two long thin bolts clipped to the duplex front down-tubes and distance pieces which hang over the bolts like quoits. The Burman box and M. L. Mk neto all exist on the rear plates, which extend right away back to the seat-pillar, like a suspension bridge, and when you kick over, the whole contraption bends and flexes in. a most alarming manne. The box fixing isr, or rather was, made of aluminium, and consequently the first time I tightened up the bolts it cracked all over. I have made a steel one which is certainly better and seems to steady the plates a little ; but I ‘am making some new engine plates of steel and some respectable bolts and fixings, and dropping the engine it inches in the frame—it is far too high—and exchanging the box for one having a bottom fixing, giving room for a seat-pillar oil tank and a decent petrol tank.

The foot-rests are bolted on to two fan-like plates, drilled for six positions, only two of which are available owing to the unique design of the brake-rods and stays in the vicinity. The tool-box on the back mudguard suspended from the valence has already fallen off owing to insufficient support.

The brakes, two 6 in., front and rear, work well enough if kept in good order, but the front is worked by Bowden wire from the right foot and bottoms on the exhaust pipe unless kept right up, and then requires such force that you have to stand on it to feel the brake at all. I am fitting up a rcd and lever with only a 6 in. length of cable at the far end, which should be more efficient.

The rear brake is good at 50 and over, but gradually declines as the speed drops, until at io m.p.h. it hardly has any apparent effect. It has a habit of sticking on unless carefully oiled and has to be pushed up with the toe on release. The motor itself is a touring 350 S.P. Blackburne engine with low-lift canis, weak valve springs (rather too weak) and no pressure fed lubrication (as on the sports models); it is capable of hauling the bus along at a maximum speed of just under 70 when excessive valve bounce puts an end to its further activities

The touring Amac gives a low petrol consumption, bad acceleration, good starting, and continually loses its float chamber top.

The Burman box stands up to a lot of hard wear although I dislike the cork clutch (I have burnt it out twice) and the somewhat difficult gear change at low speeds owing, I think, to the coarse design of dogs on the gear faces which do not give sufficient positions of enmeshment.

In conclusion, as far as the general design is concerned and the link motion type of steering, the model is far away ahead of the present average designs ; the smaller points of design and materials leave much to be desired, but I think the 1929 models will have the majority of these points eradicated, and in its improved form with the teething troubles over I could not think of a finer machine.

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