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Ian Bowers
United Kingdom
942 Posts |
 Posted - 09/05/2012 : 15:09:10
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I am trying to ascertain the history of the windscreen wiper position in J3 3772.
As far as I can tell, at this point in the production, the wipers were electrically driven and mounted at the left hand side of the screen, driving the passenger side wiper with the driver side as a slave.
My understanding is that the earlier vacuum driven wipers were centrally mounted but had been phased out by this time.
The photo below (magnified to a rather blocky image) and dating from mid-1934 shows the wiper mechanism as central, where it remins today. Does this suggest that the wiper on the competition version was still vacuum driven (which given its tendency to stop under serious accelleration would be surprising), or that a prescient Miss Watson recognised the risk of braining her passenger on the wiper motor, and had it moved to the centre (as was only finally recognised as good practice with the MGTD from 1952 onwards).
Your wisdom on this subject would be most welcome.
Ian Bowers
OD 6791
J3 3772 |
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David Allison
United Kingdom
665 Posts |
Posted - 09/05/2012 : 15:32:14
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Ian
The car had a 3 wiper set up driven off a central wiper motor mounting when it arrived at Barrie Gillies place for its initial restoration overseen by my father.
Not sure if this is a period aftermarket piece - an up-sell product available from the works (probable) or an effort by the "precient" Miss Watson to save her passenger a head injury - but I am pretty sure it was the only wiper motor that had been fitted to that screen.
I have noticed that at least two other J3's have this wiper arrangement so maybe it was a "go faster option"!
Any improvement over the standard 2 wiper set up is a good one though :)
Regards David |
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Ian Bowers
United Kingdom
942 Posts |
Posted - 09/05/2012 : 17:39:28
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Thanks for the confirmation, David.
The set currently only has two blades and this seems to be the situation in the photo.
However whilst the chassis and bodywork are consistent with its history, there are photos from the 1970's without a windscreen (and much else!), so this, and the one your father worked on, may not be original. Certainly the bonnet is not original and is marked 2511 BK (does this car still exist?).
On the evidence to date then, J3's were fitted with centrally mounted electric wiper motors (or is there more to come on this subject?).
Ian Bowers
OD 6791
J3 3772 |
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George Eagle
United Kingdom
3240 Posts |
Posted - 09/05/2012 : 19:58:02
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Hi Ian
My L2 has a centrally mounted wiper motor which has a short arm which in turn is connected to the two wipers. I believe the windscreen is original to the car.
My car has the earlier styled windscreen where the supports do not extend up the sides unlike the later and better supported J2/L2 windscreens.
Regards
George
L2023 and NA0960
Nr Buckingham.
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daveroberts
United Kingdom
75 Posts |
Posted - 09/05/2012 : 21:35:28
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Ian,
The attached photo shows the unrestored screen from J3758, where I believe we are looking at the front of the screen. It clearly shows drilled mounting points for the lucas wiper in the centre and in front of the driver!! Also a slave mounting point in front of the passenger.
I will go to the car and check if it is the front later
Regards............Dave.
J3758
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JMH
United Kingdom
911 Posts |
Posted - 09/05/2012 : 22:00:48
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Ian,
The electric motor for J2s was introduced after the build date of your car. I have period pics of other J3s with the vacuum unit (which I suspect yours was originally fitted with).
However I also have 1934 photos of J2s & J3s built before the change date which have changed to the electric motor (hardly surprising really) & the easiest place to fit it would be in the centre as a direct replacement, with less faffing about with linkages & the like. Most if not all seem to have done it this way, rather than fit on the n/s as the factory did for production. Miss Watson, probably retro-fitted pretty smartish, as others seem to have done.
My data is split over 2 locations, but when I've gathered it all, I'll jot the logic/evidence down & e-mail it to you, then you can draw your own conclusions.
Regards,
Jeremy |
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Richard Hardy
United Kingdom
2162 Posts |
Posted - 09/05/2012 : 23:03:42
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The central wiper motor position does involve fitting an extra arm although the benefits are with it centrally is that it stops the passenger getting the activation stitch embedded in their forehead in times of an unfortunate crash and it also avoids contact with the top of the glazing on aero screens
Rich
Vintage MG Parts |
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tjackson
Australia
106 Posts |
Posted - 09/05/2012 : 23:13:11
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Hi Ian,
Confirming Jeremy’s post, a quick scan of some period photos show the following cars had the centrally mounted pneumatic wiper systems when new: J3751, J3753, J3756, J3767, J3770
Cheers,
Tim
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tholden
United Kingdom
1638 Posts |
Posted - 09/05/2012 : 23:16:59
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Jeremy is correct. The vacuum motor was standard during the production period of the J3's but many J2's and J3's were converted very soon after the introduction of the Lucas electric wiper motor because the original vacuum motor was pretty useless.
It was normal to retro fit the electric motor in the original holes in the centre of the screen with appropriate linkage to the arms.
The interesting question is why was the electric motor as standard fitted in front of the passenger ? Certainly a more dangerous position - perhaps the linkage was cheaper to produce ?
TH |
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daveroberts
United Kingdom
75 Posts |
Posted - 10/05/2012 : 09:18:27
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Ian,
I was wrong earlier. The screen is drilled to mount the motor in the central and passenger positions, with the slave in front of the driver.
regards.Dave
j3758 |
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Ian Bowers
United Kingdom
942 Posts |
Posted - 10/05/2012 : 10:21:10
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Many thanks to you all for bowling this subject along.
Looking back on the discussion to date, it now seems clear that the car will have been originally supplied with a pneumatic wiper and that this was replaced 'in situ' by an electric motor. As has been suggested, this may well have been sooner rather than later in its life. That does then go a long way to explaining the centrally located electric motor, and possibly the external wiring to the motor.
Dave Robert's photo showing fitment work both over the passenger side and centrally adds yet another small twist to who did what, when and why!
Ian Bowers
OD 6791
J3 3772 |
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John Hunting
Australia
88 Posts |
Posted - 11/05/2012 : 01:44:58
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| What happens when the blower is on boost and not vac . John |
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Ian Bowers
United Kingdom
942 Posts |
Posted - 11/05/2012 : 09:17:05
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John
And that is precisely where my thinking started! My understanding was tha tthe pneumatic wipers were driven off the vacuum in the inlet manifold. However J3's were all supercharged, so thte inlet manifold would, presumably, be above atmospheric pressure, and would inject an explosive mixture into the wiper internals. Using corrosive exhaust fumes would seem unwise also. I can't think of any convenient place for access to a vacuum other than a venturi feed into the exhaust.
Or are we thinking rather too linearly here?
Ian Bowers
OD 6791
J3 3772 |
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David Allison
United Kingdom
665 Posts |
Posted - 11/05/2012 : 09:32:29
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Ian
Too linear - in fact you are sort of right with vacuum wipers and blown cars but sor of not too.
A blown car with throttle off has a very strong vacuum - so they probably go into overdrive when you take your foot off the gas on a blown car (even more than with an unblown one).
But with the throttle on - there is NO vacuum at all - so no wipers!
This is probably why the cars were converted to electric wipers.
There would be no real "injection of explosive gas into the wiper internals" though (I dont think so anyway), the feed pipe is too small.
I would stick with the electric motor though :)
Regards David |
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Ian Bowers
United Kingdom
942 Posts |
Posted - 11/05/2012 : 12:19:50
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Maybe I am being still too linear!
True that in a supercharged situation the vacuum would be substantial in throttle off and over-run, but this is a small proportion of the operating time and would suggest not a rather, but a totally useless wiper.
Obviously the feed to the wiper would be positive pressure for the majority of the time, if driven off the inlet manifold. A vacuum model would simply not work in these conditions. So, if a pneumatic wiper is to work in the reverse mode to the usual vacuum model, it will be puffing explosive mixture from the wiper exhaust and into the driver's face. I think that a nascent Elf & Safety would, even then, raise an eyebrow.
To me the use of a pneumatic wiper still does not ring true and I lean towards electric wiper motors from the factory as the easiest/safest solution to driving the blades. However I still have to recognise Tim Jackson's comment that original photos of three J3's are shown with pneumatic wipers.
Ian Bowers
OD 6791
J3 3772 |
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David Allison
United Kingdom
665 Posts |
Posted - 11/05/2012 : 13:29:35
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| The original set up was vacuum not pressure Ian - the only car I know of to use pressure wipers was the VW Beetle whichs used pressure from the spare tyre. |
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