Author Topic: Rear light for 1930's F/G 31  (Read 4965 times)

0 Members and 1 Guest are viewing this topic.

Offline alexd912

  • Full Member
  • **
  • Join Date: Jun 2009
  • Posts: 118
  • Location: Finland
Rear light for 1930's F/G 31
« on: 12 Nov 2013 at 05:17 »
Hi there,

Im just in the process of putting my G31 back together and Im trying to get the electrics sorted to as close to original as I can.

The version I have has front and rear light but I seem to have an aftermarket rear lamp as it has a plastic lens. What make/model would these early Douglas have?
Also if someone has one knocking about then that would be great.
 
Would the bike have had a brake light for the rear brake?

Also would anyone have the design of the battery tray that would have fitted under the tank? I have seen some pictures of the bike but it's a bit hard to determine how it was designed.

Best regards

Alex

Best regards
Alex
1930 Douglas G31

Offline oil baron

  • Full Member
  • **
  • Join Date: May 2011
  • Posts: 66
  • Location: Motueka, New Zealand
Re: Rear light for 1930's F/G 31
« Reply #1 on: 13 Nov 2013 at 09:06 »
Hi Alex

I am pretty sure that the battery carrier would be identical to that fitted to the S6, if you look under parts wanted tdale66  dated 16/1/2011, who is wanting parts for an S6 including a battery carrier. Martin  (MRD) replied with a copy of the works drawing for the main part of the batter carrier.  From memory the one on the M32 I owned once, the bottom strap was a tray that fitted the battery fairly neatly with an inside depth of about  6mm, with 2 short bosses welded to the outside to fit over the studs as shown on the carrier.  The machine would not be fitted with a brake light originally.  Hopefully if the attachment I have included works there should be a picture of the Bth lighting set up, of course the F/31 would have been fitted with the Bth Mag/dyno  in place of the pancake generator.

Hope that is of some help

Steve L.



Steve L

Offline alexd912

  • Full Member
  • **
  • Join Date: Jun 2009
  • Posts: 118
  • Location: Finland
Re: Rear light for 1930's F/G 31
« Reply #2 on: 14 Nov 2013 at 06:04 »
Thanks for the picture as I havent seen this before.
I will check the old post out as well. I have an old douglas battery frame and maybe I can look at that for some inspiration.

Would the connectors between the looms be lucas style bullets with rubber over the top as well as the cables from headlamp to frame, would that be rubber or something similar?

Regards

Alex
Best regards
Alex
1930 Douglas G31

Offline oil baron

  • Full Member
  • **
  • Join Date: May 2011
  • Posts: 66
  • Location: Motueka, New Zealand
Re: Rear light for 1930's F/G 31
« Reply #3 on: 16 Nov 2013 at 23:55 »
Hi Alex

I think all the components would be hard wired without Lucas type bullet connectors, which did not appear on the scene till the late 1940s.  The wires certainly be rubber insulated with a fabric covering, a rubber sleeving would be used to carry all the wires that come together near the cutout mounted under the front of the tank  up to the headlight.

The F/G models were fitted with the Bth Mag/dyno. The dynamo probably produced all of about 15 watts on a good day. This would hardly balance the headlight load.  The dynamo is a permanent magnet type (similar to the pancake type) and as such does not need to use a CVC (constant voltage control) unit or regulator as used on the post war machines.  It will of course need to use a cut out or reverse current relay, which senses when the dynamo output is high enough to start feeding current into the 6v. system. At that point it will close its contacts and stay closed until the output of the dynamo falls below 6v., whereupon current would flow backwards to the dynamo unless the contacts open. With the contacts open the dynamo is disconnected from the system.  Because there is no control of the voltage as such, unlike the post war set up which regulated or reduces the field current of the dynamo once the output voltage reaches 6.8v., which is the on charge voltage of a 6v. battery. Thus the constant voltage control, the earlier method of controlling  the current and voltage was means of the 3rd brush system, whereby to prevent overcharging of the battery a series resistor was incorporated in the headlight switch and was in use unless the headlight was in use. The Bth used a similar system incorporating a series resistor.
In the sightly earlier BTH headlight, i.e. fitted to machines in around 1930, with a large bakelite rotary switch at the rear of the headlight. It was a 4 position switch with the following positions, Full, Dim. Charge & Off.  I cannot remember what the later P & H headlamps with the cast aluminium switch knob, which would have been fitted to the 1931 models, had on the switch but I am pretty sure it too was a 4 position switch.  No dipswitch would have been fitted originally as a single contact headlight bulb of 12w. would have been fitted, together with a 6w. park bulb.  The four position was Off, presumably the charging system was off but I am not sure how this was achieved, unlike the Lucas system which did not generate at if the field circuit of the third brush was open, Dim presumably was the park light, Full switched on the headlight bulb, and Charge being used to charge the battery during daylight running.
When double filament bulbs (which appear to have come into regular use on English cars around the late 1920's) became available, it was some years before they became mandatory. It became a requirement have dipping headlights on all vehicles in New Zealand in July 1939, this required the replacement of the headlight bulb holder,  for one with 2 contacts. It was also necessary to fit a dip switch, or reconfigure the headlight switch so that the system was charging in the charging position, the off position became the park light, and the high/low headlight was operated in the Full/Dim position, this avoided the use of a dip switch.  My H3 of 1930 has been rewired in this manner, but unfortunately it has a Lucas headlight not a Bth with the rear switch. No brake light switch was originally fitted.  I am not sure what the original hooter button was like but it may well have been an insulated metal strip which was pressed against the handlebar.
Hope my ravings may be of some help
Best of Luck with the restoration

Steve L
Steve L

Offline alexd912

  • Full Member
  • **
  • Join Date: Jun 2009
  • Posts: 118
  • Location: Finland
Re: Rear light for 1930's F/G 31
« Reply #4 on: 17 Nov 2013 at 14:41 »
HI there,
Big thanks for a very excellent description of the inner workings. So I have a BTH magdyno which needs striping down and rebuilding as there are some rattling coming from the dynamo side and I have a very stuck screw which needs drilling out. I also have what I think is the 6v relay, please see attached picture. If this is correct then how would this have been wired to the maydyno?

I do have a BTH headlight as well with what i think is the correct switch. Please see attached. I presume the load resistors you are talking about are the coils of wire around the switch??

Mine has the following letters "Off C D F" which are as you mentioned as well as only a single beam light holder.

The only wiring diagram I have is from a bit later than 1930 book on Douglas which shows a dynamo configuration but as I don't have the book with me I cant recall if it has the relay there..

As for horn I managed to get a P&H bike horn, now I just need the mounting bracket for it.

Thanks again for all your help.

Alex







« Last Edit: 15 May 2014 at 21:01 by Dave »
Best regards
Alex
1930 Douglas G31

Offline alexd912

  • Full Member
  • **
  • Join Date: Jun 2009
  • Posts: 118
  • Location: Finland
« Last Edit: 15 May 2014 at 21:04 by Dave »
Best regards
Alex
1930 Douglas G31