Tandem Road Roller
Built by Adrian Ashford in September 2012
This is the New Meccano Model featured in the February 1955 issue of Meccano Magazine.
It is based on a diesel-driven road roller, with both rolls the same width and diameter. It has a novel feature and use of parts, making it an interesting model to build.
It is driven by an E15R motor (E20R in the original) and the drive to the front roll is through a reversing gear-box via reduction gearing, including a Worm meshing with a 38-tooth 1” Gear, at non-standard spacing, the final drive being by a ½” Pinion and the external teeth of a Gear Ring on the outside of the roll. It has the novel feature of power steering, driven by a separate gear train, including a ½” Pinion meshing with a 1” Gear. The steering is actuated by a tiller-type lever which engages friction clutches with contra-rotating ¾" Pinions, so enabling the rear roll to be turned either way, via cords wound onto a rod in opposite directions.
According to the instructions, the steering roll is at the rear, not the other way around, as you might think! The driver’s seat faces towards the front, driven roll. Presumably this model was based on an actual machine.
I did make some changes to suit my own ideas as I went along, notably the pivot for the steering roll, which I made more robust, and in the levers for operating the steering. Otherwise, it’s built pretty close to the instructions, which are generally good. Like other Meccano Magazine models of this period, it is a good attempt at producing an interesting, worthwhile model for the more advanced builder.
One usually thinks of having to use a mains transformer to power an E15R/20R motor, which or course means trailing wires, which I’ve always detested in a mobile model. Knowing that alkaline batteries are capable of delivering a heavy current (try short-circuiting one and see what happens to the wiring!), I found that 15V worth of AA-size cells gives plenty of power for an E15R. These are all concealed under the driver’s platform. So this may well be the first ever side-plate motor-driven Meccano model powered by dry cells!
January 2013
I came across the reversing clutch mechanism, used for the power steering in this model, in the October 1952 issue of Meccano Magazine, on page 464. It was designed by the Danish Meccano enthusiast Neils Gottlob. A number of his mechanisms appeared in Meccano Magazine in the 1950s, all illustrated by superb line drawings.
Also, in the engineering notes on page 565 of the December 1952 issue, I discovered a photo and brief description of the actual machine which the Meccano model was obviously based on! It is surprising that they made no reference at all to this information in the model’s instruction when it appeared in February 1955. I have made some modifications as a result of studying the photo, though the original was pretty close. I’ve also altered the power steering to be operated from a lever on either side, as the Meccano Magazine model was actually correct in this respect, rather than the tiller-type lever which I originally has used. The only snag is that, because there’s more slop in the extra linkage, it doesn’t work as well!