First job in the workshop is to take advantage of the space and have a sort out of parts. A few small items have been mislaid over the past couple of months, but will hopefully appear in the process of reorganising
|Long overdue sort out of remaining parts|
Since the beginning of this year I've deliberately avoided doing anything that can be done whilst the car is away at the trimmers, so that I would not be 'kicking my heels' for a month or so. Consequently I have a small list of jobs lined up for the next few week, the first one being to strip and re-con the wiper motor and rack, or possibly upgrade it.
Before starting on this I did some research and looked at alternatives. The original item has a few downsides in that it is single speed, not self parking and uses a wound field coil motor rather than the later and more powerful / efficient permanent magnet type. Will it still work after around sixty years of inaction, and if so, could it be made to operate satisfactorily in spite of its drawbacks? With the rack removed I applied 12 volts with a 2 amp limit to avoid any disasters but nothing happened.
|Grease is solid due to fifty years of inactivity - no wonder it wont run.|
Looking at the almost solid grease in the gearbox this wasn't really surprising so the gearbox was also removed, but to no avail. Next the end cover was removed then the brushes. It was clear now that the output shaft was seized solid in its bearing, probably just through lack of use.
|Output shaft (other end) seized solid in it's bearing|
I left it to soak in a shallow bowl of thinners then turned my attention to the seriously 'gunged' up gearbox. This was stripped, cleaned and checked for wear. Once cleaned up, every part looked almost as good as new (as did the motor commutator and brushes). I was quite impressed by the design detail of the gearbox, particularly the two sets of needle roller bearings supporting the intermediate gear driven by the motors worm gear.
|Nicely made with two sets of 15 needle roller bearings to support intermediate gear|
After an hour or so of soaking, the rotor shaft was free allowing the rotor to be withdrawn. After a good clean and a coat of crackle finish paint to the motor casing, it was re-assembled and again connected to a 12 Volt supply. This time it ran beautifully drawing just over 2 Amps without any load. Increasing the load by slowing the worm gear drive increased the current draw by up to half an amp. This will be a very useful way to determine the friction created by the gearbox and rack.
|Motor cleaned, painted and re-assembled - as good as new|
Next the gearbox was added and the current draw remained constant indicating that all was nice and free with little friction.
|Gearbox added - no increase in friction|
The motor with gearbox attached was left running whilst the rack and wheel boxes were stripped, cleaned and given an ample coating of Graphogen grease. Again the wheel boxes were in exceptional, good as new condition with no perceptible wear.
The whole assembly, motor, rack and wheel boxes were now reunited. Initially the current draw was around 0.3 Amps higher but slackening the rack retainers on the wheel boxes brought it back to around 2 Amps. Playing with the positions of the rack outer casing ends and gradually tightening them up with the motor running seemed to allow them to settle into their preferred location and the 2 amp draw was again achieved. After a couple of hours running, the current actually settled to 1.7 Amps (20 watts) which I would guess is about right.
|Rack and wheel boxes added. Current settles to 1.7 Amps when run in.|
The dash board now has the benefit of connectors so is much easier to remove which makes access to the wiper assembly straight forward. If it transpires that they are in fact hopeless then I will have to look at upgrading. Local fellow 120 owner Tony Hamnet wrote an excellent article in the January 2013 XK Gazette detailing everything necessary to fit a more powerful two speed, self parking arrangement. Quite an involved bit of work not to be undertaken lightly but good to know it can be done if necessary.
Uniquely for an old car, my XK140 fixed head has excellent self parking two speed wipers, but I really miss the single wipe facility of a modern car. In the UK it's as likely to 'drizzle' as it is to rain making a single wipe facility much more useful than a second higher speed. So one possible side benefit of the original very basic system is that it may be possible to add a second switched supply to the motor via some sort of pulse switched timer relay allowing for a single wipe. With a mere 1.5 secs for a wipe back and forth, getting the timing right might be a problem or even impossible but it could be an interesting and cheap solution. I'll look into it. In the meantime it'll be fun honing the skill of switching off at exactly the right moment to neatly park the blades in the right place.
Trimmer John was most adamant about the need to be able to drive the car in and out of his workshop, so the run up to its delivery to him, due to this additional work, was very busy. I had not intended to install the engine until April and bringing this forward meant not doing a few other jobs. Consequently I was duly chastised for my lack of preparation. As the starting procedure was complicated by the battery isolator switch and immobiliser I had written out the order of actions - Isolator on - blip immobiliser - ignition on - choke on if cold - starter button - then - choke off after a couple of minutes. I explained all of this to John and his response was "all looks a bit complicated - I don't think I'll be bothering to move it after all".
Good trimmers are hard to find so I bit my tongue!
Next post beginning of April