An alternative drive system for the "Light Pattern" lathes was a drive unit using a motor flange-mounted to the inside rear of the headstock-end leg. Unlike the same system used on the full backgeared and screwcutting Union lathes this had no reduction gearbox on the end and drove the headstock pulley directly.

Continued:
In addition to the "Light Pattern" machines two backgeared and screwcutting Union models were made with 3.5 and 5-inch centre heights. These were not heavy, commercial lathes but economical machines intended for  … technical schools, garages, metal workers, amateurs, etc … Though both resembled the light lathes - and used the same form of flat-topped bed but with V-edges to guide the rather short saddle -  each was a separate model with no parts in common.
3-inch:
With a specification that shows it was built down to a price the design of the 3.5" x  22"  Model L.1.A.S. lathe was absolutely typical of its era. Whilst later versions used a relatively large-diameter ball bearing at the front of the spindle, early models were fitted with a plain bearing closed down by twin bolts  - though both used the same rather light, single pinch-bolt plain bearing at the rear. Most spindles have been found with the maker's specification of a 3/8-inch bore, No. 1 Morse taper with a 1" x 8 t.p.i. thread, but others are believed to have been used as well - including that found on the 5-inch at 1.25" x 12 t.p.i.. The backgear was the simple kind that slid into place, with engagement possible without the use of spanners - a spring-loaded pin being used to couple pulley and bull-wheel together. Spindle speeds naturally varied slightly according to the type of countershaft used - bench, wall, ceiling, foot-treadle and motor-driven units all being available - but the six available (when driven from a 400 r.p.m countershaft) generally spanned a useful 32 to 800 r.p.m. arranged in geometrical progression. The 3-step headstock pulley took 1-inch wide belt and had diameters of 2", 3" and 4". Unlike many similar lathes that ran their treadle-driven flywheel on plain bearing, Harrison used a pair of ball bearings, fitted a "frictionless" chain for drive - and also ensured that the assembly (with cone diameters of 20.75, 21.375 and 22 inches) was properly balanced. The most sophisticated drive unit employed a 0.5 h.p. motor flange-mounted against the inside face of the headstock-end leg - and incorporating a reduction gearbox (optimistically termed silent pinions) around its output shaft. The bed was given a permanent gap to swing material 10.5-inches in diameter and the 1" x 8 t.p.i. leadscrew - allowing for the full-nut on the apron - was fitted with a dog-clutch by the headstock and a handle at the tailstock end. To permit the generation of left-hand threads a simple form of reverse was used on the leadscrew drive with a bracket, carrying a permanently-mounted gear, that could be swung into place when required.
Off-set right to the left-hand side of the saddle - to let the cutting tool reach up to the spindle nose across the permanent bed gap - the compound slide rest assembly lacked micrometer dials on both cross and top slide -  though most examples have been found with the 6.75" x 3.75" cross slide equipped as a boring table with T-slots to the rear of the top slide. Secured with just a single bolt - pressing against an inverted cone - the top slide could be quickly removed; the feed screws ran through replaceable bronze nuts - the makers resisting the temptation to tap these directly into the casting in a fashion then common amongst other purveyors of less-expensive lathes.
In the late 1930s the basic bench model sold for £15 : 10s : 0d equipped with a countershaft, the treadle lathe for £17 : 10s : 0d and the motorised version for £ 26 : 0s : 0d. Backgear and changewheel guards were supplied as standard but covers for the drive belts were extra: fifteen shilling for a lower shield or £2 : 0s :0d for full enclosure. He lathe was supplied as standard with a faceplate, two Morse centres, one wood-drive centre, 10 changewheels, a screwcutting chart, spanners and drive belt.
5-inch:
Enjoying by far the best specification of any Union lathe the 5" x 30" model L.2.A.S. was fitted with drive to the 1" x 4 t.p.i. leadscrew through a proper tumble reverse mechanism, single-lever engagement of backgears, clasp nuts on the apron and a bed whose planed top was hand-scraped to an accurate finish. The spindle, with a 1.25" x 12 t.p.i. Nose,  ran in ball races at both ends - that at the front being a combined radial and thrust unit - with a single-lever enraged backgear ensuring that no fastenings needed to be release before the slow-speed range could be selected. The stand was identical in design to that used on the 3.5-inch model, though the gearbox on the motor-drive type had an output speed of 200 rather than 400 r.p.m. to give spindle speeds that spanned a usefully slow 15 to a inadequately high of 375 r.p.m.  Using a 1.25-inch wide belt the cone diameters on the treadle-powered flywheel were slightly altered at 20.75", 21.375" and 22", as were those on the headstock spindle at 2.75", 4" and 5.25".
Basic equipment supplied as standard consisted of: a faceplate, drive plate, a set of (unspecified) changewheels two centres, a travelling steady, spanners and a screwcutting chart. Anumber of accessories was available for both lathes - the usual chucks, steadies, metric conversion changewheel, turning tools, hand T-rests in two sizes, faceplates, etc - and also a milling slide and a special milling and gear-cutting attachment of the type offered until the late 1960s..

1930s and 1940s Union 3.5-inch backgeared and screwcutting lathe with ball-bearing headstock, a permanent gap in the bed, "frictionless" chain drive from foot pedal to flywheel and a leadscrew with dog-clutch and a handle on its end.

1930s and 1940s 5-inch backgeared and screwcutting Union lathe with single-lever backgear, tumble reverse, detachable gap bed and clasp-nuts on the apron. This art-worked publicity pictures gives an impression of smooth finishes and neat detailing - the reality, as shown in the photographs below,  was rather different

By way of comparison here is the contemporary and very much more robust commercial lathe that was made in 4.5 and 5-inch centre heights. Note the many similarities to the later and long-lived L5 series made from the 1940s onwards

The Union 5-inch could be arranged for underdrive and had a neatly-arranged, single-lever backgear engagement mechanism. As the photograph shows, the cosmetic finish left a good deal to be desired.

Although well built for an inexpensive lathe some aspects of its detailing were poor with no micrometer dials on the compound rest feed screws nor any protection for the cross-feed screw

Headstock on an early 3.5-inch with plain bronze bearings. The bracket holding the reversing changewheel for left-hand threading can be seen on the end of the headstock