Wipers and wheelbox...
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Wipers and wheelboxes

Roger King
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Having recently fitted reproduction wheelboxes of the correct configuration to allow a proper sweep of the screen, on the way to the Bicester Scramble last Sunday I encountered a lengthy, and somewhat biblical downpour that was not a lot of fun for all concerned.  The misery was compounded by the passenger's side wiper flopping down onto the screen frame and doing the twitching thing, due to a failure of the arm to grip the wheelbox splines effectively.  Luckily the driver's side held so I could maintain some degree of vision (although I must get around to fitting an internal system to wipe the inside of the screen, and both sides of my spectacles).

The problem analysis on returning home (thankfully in the dry) was not straightforward, as both arm and wheelbox are modern replacement items (wheelbox from a supplier who trades via ebay, arms direct from Tex).  A few days' research, involving much discussion with the US oracle, have revealed that my arms and blades were incorrect for 289 anyway - the wheelboxes are the right part number, but the splined spindles have not been manufactured to the original standards.  I've had this before with the Cooper S's wipers - repro parts made to look right but incapable of the proper performance of their intended purpose.

The wiper arms, for all Cobras (I think - never sure about those fat things - I believe they're known as '427s', or something similar) have various part numbers (745101, succeeded by service replacement 745071), but boil down to this spec:  10.5" long (centre spindle to tip), push fit, wrist action ('spoon') connection to blade, left crank, 10˚crank, 'lock' spring (not coil spring), chrome and stainless construction.  You will be incredibly lucky to find either of those part numbered items in serviceable condition.  If you can find some with the cast, hinged socket in good condition, it is possible to drill out the long pivot stainless rivet and fit modern repro components to the actual cast pivot.  This replaces the repro female splines, which are generally made of cheese, with 50- or 60-yr-old components which are vastly superior.  Please note, classic car repro parts industry.  We don't care about price, we want them to work...

Wiper blades for Cobras need to be wrist-action fit to match the arms, and were mostly supplied by the factory as the shorter 8" blade, usually Lucas 'Rainbow' but not always.  A very few cars seem to have been given 9" blades - Dan reports one new car that was supplied with one 8" and one 9" blade - but these put a little more strain on the mechanism, which is never a good thing.

The wheelboxes are also not straightforward.  To work properly with the DR3 reverse-park two-speed six-wire motor with 120˚gear, with which all Cobras were fitted,* the wheelboxes must have 22-tooth gears rather than the more common 32-tooth wheel.  A 32-tooth wheel with the correct motor etc. will only give you a screen sweep of around 80˚- ask me how I know.  Unfortunately it seems the material used for repro wheelbox splines is also a variety of dairy product, hence my misfortune last Sunday.  A micrometer reveals them to be of a slightly reduced diameter too, which doesn't help.  If you're searching for NOS or used, I won't give part numbers as the list is long and complex but there are a lot of cars that use the same design under a different number.  Pre-1962 Morris Minor is probably the most common - the 'clap-hands' wiper model, but not the even earlier split-screen.  Used wheelboxes are still likely to be much better than repros as original-quality splines don't seem to wear badly.

Or just fit a modern 14W wiper motor and have done with it!**


* I think, see above comment regarding 427s

**  Definitely not the same - the wipers should park down on the screen rubber, which they can't with this motor as it does not reverse park.

The Cobra Register - Historian
Several old bangers, which used to include a 289