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dade
United Kingdom
503 Posts |
 Posted - 25/01/2016 : 11:03:12
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I would appreciate it if a forum member would give me details of the fitting for the 30mph warning lamp on a PB.
I have recently discovered the remains of a fitting called Lucas WL4 in my toolbox and this has led me to believe that this is the holder for the bulb on the rear of the dashboard and that the lens just plugs into the hole in the front of dashboard.
At the moment I have utilized an old Ignition warning lamp and so it may be too late to swap, as the hole size may be too large.
Never-the-less I would like to know which fitting is correct.
Look forward to your replies.
Russ
PB0333
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Richard Hinton
United Kingdom
131 Posts |
Posted - 25/01/2016 : 13:33:34
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How interesting , do we know any more about this , exactly how it worked and what models it was fitted to? Was it an option, standard or after market ?
My J1 Salonette has a speedo only no rev counter. I have tested the reading against sat nav speed indicator and was really surprised to see it is exactly accurate to the precise same number from satellite (does not over read at all - like current cars)
All this at a time when Ford are about to launch a speed limit engine speed limiting device, on their new cars , which can identify all speed limits by both satellite and forward camera recognition and automatically shuts down the vehicle so that it is impossible to break any speed limits.
Now that does sound like fun doesn't it. All George Orwell got wrong was the date.
Richard Hinton |
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Peter Dowson
United Kingdom
63 Posts |
Posted - 25/01/2016 : 14:42:08
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If my understanding is correct, these were introduced at the PB model as the 30mph restriction in towns came in in 1934 (I think). So any previous cars, eg my PA, did not have this device. I believe it connected to the speedometer and the light lit when you were doing more than 30mph - that's it.
Peter - PA0448 - 4 Seater |
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whirlwind
New Zealand
94 Posts |
Posted - 25/01/2016 : 19:38:08
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Hi Russ,
You are correct that the Wl4 was used as the PB 30mph light. The contacts in the Speedo closed as 30mph was approached & the light came on. The light went out again when 30mph was exceeded.
The bulb fitting had two wedge shape wings which rotated to clip under the leaf springs on the mounting plate that was screwed onto the back of the dash board, hence the fitting could be removed to change the bulb. The Lens just pressed into the hole in the front of the dash board.
Note: In pictures 3,4,& 5, the bulb holder has been clipped into the mounting plate (with the leaf springs) from the wrong side.
Colin
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ags
United Kingdom
275 Posts |
Posted - 25/01/2016 : 19:55:30
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Russ,
You are correct, the bulb holder does just screw to the back of the dashboard (two very small wood screws through metal "ears" on the holder and the lens holder is a simple circular metal pressing around the plain glass disk. The glass holder has a tubular portion which is a friction fit directly into the wood of the dashboard. There has never ever been any sign at all of any plating on the visible rim of the holder on my car though I admit that it could have disappeared in the 29 years prior to my ownership. The bulb holder has an electrical feed which is permanently at 12 V when the ignition is on. (I use the feed to the dash-lamp switch as this is near by). The correct PB/NB speedometers have an insulated screw terminal on the back which allows a lead from the warning bulb to have an earth when contact is made within the speedometer with a short metallic segment turned by the needle spindle. The length and angular position of this segment is adjusted so that the light comes on at 20 mph and goes out at 30 mph. In other words in those simpler days of only one speed limit, if the light was showing then you were legal or somewhere just under the limit. As has been noted the chronometric speedometers can still be very accurate as long as they are set up to take account of final drive, wheel size and tyre size so that my own light does indeed go out at 30 mph according to the numerous speed displays in my part of the world. (And this is at least forty years after I last had the speedometer rebuilt and recalibrated by Speedograph- Richfield).
Finally the only MMM models fitted with these speedometers were indeed the PBs and NBs as a result of the legislation about a year before and the prevailing image of speeding sports cars. This feature was retained when the TA and TB were introduced.
More technical ramblings from
Andrew Smith MMM571
PB Abergavenny |
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whirlwind
New Zealand
94 Posts |
Posted - 25/01/2016 : 20:01:40
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Russ,
The 30mph light apparently was also used on the TC.
The lens unit only (not the whole light unit), is listed as being available from 'FROM THE FRAME UP'
I don't know whether this lens unit is the same as that used for the PB but it could be an avenue to explore if you don't have the lens.
Colin |
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LewPalmer
USA
3211 Posts |
Posted - 25/01/2016 : 22:51:17
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The TC lens is not the same as the PB/NB lens. The correct lens is shown is whirlwind's first photograph (after the drawing) They are not terribly difficult to make a reasonable replica of the lens. Below is a photo of one I made for another PB owner.
The socket was simply a standard lamp socket attached to a base, which in turn was screwed to the back of the facia.
Lew Palmer
PA1169, PB0560 |
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farley1
Canada
152 Posts |
Posted - 25/01/2016 : 23:17:49
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Russ and others.
Another picture for viewing. I have seen these from time to time on eBay less the lens assembly.
Ian
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DDMDSN
New Zealand
329 Posts |
Posted - 27/01/2016 : 22:43:32
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Good information, thanks
As can be seen in Ian's photo, the original lens has fine lines in it.
Measured and assessed an original a little while ago. The owner described the material in the lens itself as 'brittle'- like egg shell. This would be why I imagine very few cars still have them intact.
From my assessment and consideration of materials available at the time, I believe the lens was neither glass or celluloid. The fine lines under close inspection have micro fibres on them. Which leads me to believe the lens, made in very small quantities for the PB and NB, was made like a fabric aircraft wing. That is, cotton thread and cellulose dope. The curvature is 19mm dia, 3/4".
Not easy to make, there are across the 14.4mm width of the lens, close to 34 fibres.
I have prototyped making the lens and the lens holder and looking at a making a small batch later in the year if anyone is interested, let me know.
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Jamie
Canada
218 Posts |
Posted - 28/01/2016 : 07:13:28
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Donald
I would be interested in the lens if you make a batch in the future. I have looked for a lens similar to the original and found that the Lucas SM5 dash panel from Austin 7s has a red lens that fits the job. Even closer is the orange TRF lens from an XK120 dash which has a deep bezel. Either one provides a suitable alternative until an original (or re-made) one can be found.
Jamie |
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ags
United Kingdom
275 Posts |
Posted - 28/01/2016 : 23:26:58
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Hi Russ,
One thing I forgot to mention in my description above is that I believe that the warning light lens should be green in colour. This makes sense when you think that the speeds I mentioned (taken from some printed literature somewhere, though heaven only knows what or where) are all legal and so green would indicate that all is well. The light should definitely not be on above 30 mph because as my description said it can only be on for a small speed range because of the limited width of the contact segment, and so if the light comes on at a higher speed then it will also go out at an even higher speed e.g. on from 30 to 40 mph which does not make much sense in a Thirties context.
I suggest that the odd colour shown in the photographs such as Lew's is the result of the fading of pigments. I certainly have had to darken my lens somewhat using a piece of theatre lighting green filter courtesy of a friendly stage manager. Also my lens is definitely one piece of material (probably just flat glass though I have never analysed it specially) and not some early type of composite.
I also acknowledge that my memory slipped up with respect to the exact rear of dashboard components and I managed to combine at least two parts into one. The spring clip arrangement which allows the bulb to be changed from behind the dash, as shown in the various drawings and photographs is undoubtedly correct. I remembered this as soon as I had thought about the last time (quite a long time ago) when I changed the bulb.
More technical ramblings from
Andrew Smith MMM571
PB Abergavenny |
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dade
United Kingdom
503 Posts |
Posted - 29/01/2016 : 08:27:24
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Well Thanks everyone for such a splendid response, I think that we now know all there is to know about 30mph light fittings
Thanks everyone for your input.
Russ |
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