MASCOT October 1984

THE ROADSTER FRONT - The Wiper Motor.

Bill Haverly

The next time there's a downpour and you're out in the Roadster, spare a thought for the little black box on top of the windscreen as it struggles to keep the rain off the glass. Considering it was designed over 40 years ago, the CWX wiper motor can't be criticized too much for failing to come up to modern standards, but it certainly runs a bit on the slow side.. If you stretch the imagination, it could even be seen as a two speed wiper, being either battery powered or manual - and if you have a willing passenger the hand operated method is much faster. On the credit sides it's sturdy simple design makes for a reliable unit, providing the basic maintenance of adding a few drops of machine oil to the centre bush lubricator and the felt washer under the protector plate (see diagram) is carried out occasionally.

The CWX consists of two parts - the front contains an electric motor which via its splined armature shaft drives two gear wheels in the rear section. The larger of these, the guide wheel, is linked to a sector which drives a gear to the wiper spindle and causes it to oscillate. From the spindle a short arm attached to the coupling bar connects the two wiper arms. In the back of the motor, the drive gear is lubricated by an unpleasant-sounding high melting waterproof grease called Ragosine Listate, for which Shell Retinax 'A' can be substituted if not available.

The CWX does heat up in use, but according to the makers, should only reach a comfortable hand held temperature. In practice I've found it gets hotter than that, but if it becomes unbearable to touch there are a number of possible, usually secondary, causes:

1. Persistent use on a dry screen.
2. Too much spring tension on wiper arms.
3. The use of oversize blades (8" blades are standard).
4. Sticking wiper arm spindles.
5. Dried up grease in the drive gear.

Overloading caused by any of the above will, in the early stages, melt the insulation in the wiring, particularly the input leads to the field windings, and could eventually lead to a burnt out motor.

If a breakdown occurs suddenly and is not accompanied by the unmistakable smell of burnt out wiring, however, a good idea of what is causing the trouble can often be found after removing the front cover. But before doing this make sure that power is getting to the unit. Check first that the copper strip on/off switch is clean and making contact, the brushes are in good shape and not sticking in their holders, there are no obvious burn-outs in the windings and that the armature moves freely. If all these points are in order, then there.is most likely an internal short in the motor. The case of a sluggish armature usually means that the drive gear needs cleaning out and re-greasing. Remove the backplate (i:e: the cover nearest the windscreen) to get at these works. Two nuts locked together on the fixing studs usually gives enough purchase to release them, and after sliding off the spacer/bearing and removing the split pin, washer and spring off the drive spindle, only the two retaining screws remain to be taken out. On the right hand side is the guide wheel which determines by the position of its pivoting take-off to the link arm, to what degree the wiper blades will sweep. Each guide wheel is stamped with a number which denotes its degree of sweep and for the Roadster this figure is 130 degrees. The range of CWX guide wheels is between 100 and 150 degrees but 130 is fairly common, and as it's an easy job to change one from a secondhand motor, it's tempting to drop in a 150 degree wheel to give that extra coverage. To check the sweep of a motor when off the car, connect a battery and note the range of movement on the chrome handle fitted on the end of the wiper spindle.

The correct model/type wiper motor for the Roadster is Lucas CWl BP739, CW1 being a top mounted version of the universally fitted CWX, whilst BP73 is the specific Singer coding. This series together with the voltage, month/year of manufacture and service number are stamped into the backplate, so are easy to check. There are other versions of this motor, including the CW2 (bottom mounted), but as all are the same style but with different fittings, lengths of spindle, etc. interchange is no problem. If you happen to have £100 going spare, Lucas still do a part exchange on the CWX, but otherwise a much better bargain can be obtained from PVT Auto Electrical Supplies, 19 Lucks Lane, Buckden, Cambs. (0480 810440) for about half the cost. Specialists in obsolete Lucas stock, they can also supply a few spares for the CWX such as brush gear and springs, cork washers, armatures and drive gears, but don't expect to get these parts from Lucas. The other alternative is to scratch around the autojumbles for a working unit, but check out the backplate to make sure it's not
a 6 volt wiper. They all look the same. Who knows, with a bit of luck and a lot of searching, even new motors can sometimes be found.

Regarding features of the Roadster's CW1 unity only one packing block/bearing assembly need be fitted between screen and motor but both fixing studs and spindle can be-cut down to around 1 1/4" if a non-standard unit is being used. The only other point needing mention also concerns fitting - for all
Roadsters up to late 1951 had the wiper mounted the right way up. After modifications to the windscreen, probably due to problems with remanufacture, the three pivot points were then set into the tap rail.. In it's original position on the motor would have protruded above the screen, and caused a bulge with the hood up, so it was turned upside down. The changeover point occurred with the last of the 4AB's, (with V suffixes) and the first of the new 1952 season's 4AD's which ran parallel in production. The motor works just as well the other way up however and lubricators on both sides of the body suggest that inversion was always an option.