Author Topic: BTH light switch, 1930 (Read 7825 times)

Tony Townsend · « **on:** 19 Nov 2011 at 16:45 »

Hi I'm a new member . I'm trying to find a BTH light switch for A T6.Failing this the rotating part or a pattern to make the rotating part will do. i.e. I require the shape and position of the brass contacts on the back. the bike is a1930 model

kmd · « **Reply #1 on:** 20 Nov 2011 at 11:22 »

Hi Tony
I have recently picked up a WD BTH switch for my T6 at Kempton race course
Bike auto jumble.
The Stall holder had a box of new olds stock, I paid about £20.
The only difference was the lettering on the back but all the contacts were the same.
The Next kempton is Saturday 3th December 2011
Regards
Kevin

kmd · « **Reply #2 on:** 20 Nov 2011 at 12:29 »

Here is the BTH switch that i got from Kempton

Tony Townsend · « **Reply #3 on:** 20 Nov 2011 at 19:36 »

thanks for your prompt reply . this one does not seem to be the same as on the inside of the switch there are coils and also it is attached to an ammeter I shall see if I can get a photo or two up . thanks Tony

eddie · « **Reply #4 on:** 20 Nov 2011 at 20:13 »

Tony,
Are you sure your bike has a BTH headlamp? From your description of the switch, it sounds more like a Powell and Hanmer type with brass strips connecting it to the ammeter. The coil you mention is probably the half charge resistor. Also, the Powell and Hanmer switch has a cast aluminium knob with a blade and the positions for the knob are stamped into the brass headlamp shell.

Eddie.

Tony Townsend · « **Reply #5 on:** 21 Nov 2011 at 01:14 »

Hi Eddie Thanks for your reply I'm assuming that the switch is made by BTH as the ammeter is marked BTH . The switch is 3 inches diameter on the inside and 2 3/16 diameter on the outside. the switch is held in place by 3 scews equidistantly placed around the static part of the switch on the outside . The switch is on the back of the headlamp shell and the ammeter on the top . The switch is soldered to the ammeter via a yoke type plate with access points for the lamps. There are places for 2 lamps and the connections are labled tail ,batt ,& dyn . the coil centre is made of pocelain and is held in place by a screw from the plate connecting the switch and ammeter.I shall try and sort out how to send photos when I can manage to scan them. Thanks in anticipation of more information.Tony

Dave · « **Reply #6 on:** 22 Nov 2011 at 06:37 »

Tony sent in these photos of his light switch.

Douggy29 · « **Reply #7 on:** 30 Jul 2022 at 03:29 »

Dave
In your picture it seems as though the body is also the reflector.? Is that so? Also I don't suppose you have a picture of the catch on the bottom do you?

Dave · « **Reply #8 on:** 30 Jul 2022 at 08:02 »

Sorry, I can't help with any details or more photos. The parts belonged to the topic starter, Tony Townsend. I just posted them on his behalf back in 2011.
However other members may have some information or a photo of the catch, so suggest checking this topic again in a few days - something may turn up.

Dave

Douggy29 · « **Reply #9 on:** 30 Jul 2022 at 08:57 »

Thanks Dave
So little info available for much of the douglas stuff

cardan · « **Reply #10 on:** 30 Jul 2022 at 23:44 »

Nope, I don't agree. From the "home" page here, type bth headlamp into the search box and all manner of content appears. There has been a lot of discussion about BTH headlamps, which (I will agree) are now rare and hence fetch high prices.

This thread, for example, has some nice info: https://www.douglasmotorcycles.net/index.php?topic=7770

Good luck.

Leon

Douggy29 · « **Reply #11 on:** 31 Jul 2022 at 03:51 »

Yes
Followed your instructions Leon and still came up empty. Some of the stuff was mine anyhow. My original post was about a year ago and was to ask whether there was a reflector, or was the body the reflector. Richard responded and said there was a reflector. I still haven't seen a picture or diagram of the internals. The picture I saw yesterday tend to show a shiny surface on the inside of the body and I can sort of believe it is correct because of the parabolic shape of the body. Nor the clip underneath to secure the rim. So if anyone has one would they please take some pictures of it or some diagrams etc..

cardan · « **Reply #12 on:** 31 Jul 2022 at 06:59 »

OK, but we sometimes have to work for knowledge - most often it doesn't just appear for the asking. Reading the various BTH posts here there is some very interesting stuff about the different BTH headlamps, and the P&H-like variants, with the different configurations of switches (bakelite knob or alloy blade) etc. There are clear variations in the detail of body shape and rims, switches, and meter positions.

I'm interested, but I'm not an expert. However I can say that by 1930 all headlamps worked by positioning the filament of the globe at the focal point of a parabolic reflector, so, yes, there is a separate reflector. But to get the details, you need to be really specific about exactly which headlamp you have, and let us know what is there and what is not.

With the internet, there is info everywhere. The Vintage Motor Cycle Club (UK) has a library with an online catalogue. They have the following:

BTH Ignition and Lighting sets, types PBK, PBM, 1930, 28 pages
https://library.vmcc.net/Catalogue/Details/79088

BTH Ignition and Lighting sets, types PBK, PBM, Forms A&B, 1927, 11 pages
https://library.vmcc.net/Catalogue/Details/79089

BTH Generator lighting set, type PA for Douglas, 1930-33, 12 pages
https://library.vmcc.net/Catalogue/Details/78581

Maybe the answer to your query is in one of these? If you're a member of a club affiliated with the VMCC, you're welcome to use VMCC facilities, and the librarian might be able to help.

Leon

Douggy29 · « **Reply #13 on:** 31 Jul 2022 at 07:19 »

Thanks Leon
It is actually the model pictured above and you can see the reflective quality of the inside of the body. I'll see what the VMCC has to offer.

Douggy29 · « **Reply #14 on:** 31 Jul 2022 at 07:29 »

Couldn't get anywhere without joining and they want 65 pound . I don't want to pay that just to get another picture of the lamp.

cardan · « **Reply #15 on:** 12 Aug 2022 at 12:46 »

Here's the clip: https://www.douglasmotorcycles.net/index.php?topic=6487.msg25264#msg25264

Douggy29 · « **Reply #16 on:** 13 Aug 2022 at 01:37 »

Thanks for that Cardan . I still cant find a reflector which makes me think that it is the body itself.
Douggy29

douglas1947 · « **Reply #17 on:** 15 Aug 2022 at 17:51 »

Douggy29,

I have the same BTH headlamp on my 1930 H3.
The reflector is direct fitted in front of the lamp body.
In the headlap rim is only the glass fitted.

I have added photos.

Michael

douglas1947 · « **Reply #18 on:** 15 Aug 2022 at 17:53 »

Photo Lamp body incl. refector

Douggy29 · « **Reply #19 on:** 15 Aug 2022 at 23:58 »

Hi Michael
Finally, I have proof that there is a reflector. Many thanks for the pictures. I presume the depth of the reflector is 65mm, is that correct?
I don't suppose you have a picture of the rim catch as well. All I've got is a brass rod with a thread on one end and a hinge on the other.

Once again many thanks
murray

douglas1947 · « **Reply #20 on:** 16 Aug 2022 at 06:08 »

Hi Murray,

will this photo help you?
If you need more information don´t hesitate to ask.

Michael

Douggy29 · « **Reply #21 on:** 16 Aug 2022 at 06:44 »

Thanks again Michael, I got the bike in pieces so I just might have one of them and overlooked it. Unfortunately I probably wont be able to get a reflector so I will buy a cheap one and cut it down.

Many Thanks Murray

Douggy29 · « **Reply #22 on:** 16 Aug 2022 at 07:18 »

Hi again Michael, I couldn't find a piece like that in amongst my bits. But I have attached a picture of mine after much panel beating etc.
I was assured that the glass is genuine, but the rim sits up quite high and for that catch to work I'm sure the spring would have to disappear inside the catch. Do you think apart from the homemade catch that it looks correct.
Sorry to keep bothering you.
Murray

douglas1947 · « **Reply #23 on:** 16 Aug 2022 at 12:33 »

Hi Murray,

you see my glass an otherbsurface, nearly clear with very small spots.
May be yours is of early Lucas (MU42) type?
The holder for the rim has no thread, just a plain shaft to allow the spring to press the winged holder to the sloted part on the lamp body.

I send a further picure. Let me know, if you need any measures or photos.
My bike is "unrestored", so "very untouched".

Michael

Douggy29 · « **Reply #24 on:** 17 Aug 2022 at 00:57 »

Yes Michael I'm starting to think my glass perhaps isn't the right one and is to thick, therefore the rim sits up higher than it should making the catch strained. That can be seen in my pic.
Once again many thanks.
I'm sure that this info would have been in original documents but as yet have never found any.

Murray

Douggy29 · « **Reply #25 on:** 17 Aug 2022 at 01:11 »

Here is a picture of my lens, upto9mm thick. Replaced it with a thinner dimpled piece of glass and now the rim sits down on lip around the light . Much better! I just noticed on the outer surface it says Guide or cuide tractor lens, very hard to see. I intend to google it to see. Anyhow having a thinner lens makes more sense.
Murray

Image rotated, cropped and converted to linked file - Dave, 16Aug2022

douglas1947 · « **Reply #26 on:** 17 Aug 2022 at 05:43 »

Hi Murray,

I think up to 9mm is very thick for a lens, so a thinner will make a better fit.
I send a further picture I have, with measure of the "Low" light beam hole. May be it is of use for you.

Michael

Douggy29 · « **Reply #27 on:** 17 Aug 2022 at 06:10 »

Yes it is Michael. I found the lens is actually a tractor lamp lens so I was told incorrectly. I'll just use a thinner glass.
Thanks Michael