Author Topic: Alternators to replace BTH pancake dynamo  (Read 20590 times)

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Offline Edin

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Alternators to replace BTH pancake dynamo
« on: 16 Nov 2007 at 19:10 »
He all.
I would like to build an small alternator on my Douglas T6 1930, in such a way, that the original BTH cover can hide the alternator. I wil be happy for any help and advise for this project if somebody have any experience to share.
Many  in the North hope for a solution,- they have the same problem.
Regards Edin DK.

Offline ChrisS

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Re: Alternators to replace BTH pancake dynamo
« Reply #1 on: 09 Dec 2007 at 12:30 »
I have an E32 which is essentially a T6 and I have replaced the DC generator with an alternator. The Yamaha 125 TZR or DT 125 both have an alternator under the flywheel. I sourced  from scrap,  a flywheel/ backplate with coils and the Yamaha solid state rectifier/control unit
I made a new backplate  which fits into the timing side cover as before, this carries the coils. The backplate carries a new shaft supported by two bearings to couple to the idler gear driving the magneto and by taper to the Yamaha flywheel. I machined the Yamaha Flywheel externally to reduce its mass and to fit under the old pancake generator cover  and with the rectifier mounted  between the frame top tubes under the tank I now have a 12 volt alternator.
I'm sure there will be other ways of doing this using similar components from other bikes but this has worked out ok

ChrisS

Offline jaiboni

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Re: Alternators to replace BTH pancake dynamo
« Reply #2 on: 10 Dec 2007 at 04:57 »
HELLO  Edin DK.
HI PLEASE GIVE ME COUPLE OF DAYS , ONE OF MY FRIEND HAS IT BTH FULL SET HE WANTED TO SELL IT ,
AS HE OUT OF TOWN,
REGARDS :lol:
OM NAMO NARAYNA
JAI MATA DI
OM SAI BABA

Offline Edin

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Re: Alternators to replace BTH pancake dynamo
« Reply #3 on: 10 Dec 2007 at 14:03 »
I have an E32 which is essentially a T6 and I have replaced the DC generator with an alternator. The Yamaha 125 TZR or DT 125 both have an alternator under the flywheel. I sourced  from scrap,  a flywheel/ backplate with coils and the Yamaha solid state rectifier/control unit
I made a new backplate  which fits into the timing side cover as before, this carries the coils. The backplate carries a new shaft supported by two bearings to couple to the idler gear driving the magneto and by taper to the Yamaha flywheel. I machined the Yamaha Flywheel externally to reduce its mass and to fit under the old pancake generator cover  and with the rectifier mounted  between the frame top tubes under the tank I now have a 12 volt alternator.
I'm sure there will be other ways of doing this using similar components from other bikes but this has worked out ok

ChrisS

Hej ChrisS - Thanks for information,- description and support to the project. Just what I need to go further on.
Do you have any problems with diameter and height in your project - was it possible to hide the alternator under
the BTH cover without change coverdimension?
Best regards Edin DK.



[edit quote codes, 10DEC07.  -Doug]
« Last Edit: 10 Dec 2007 at 18:58 by Doug »

Offline ChrisS

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Re: Alternators to replace BTH pancake dynamo
« Reply #4 on: 10 Dec 2007 at 19:25 »
Mine fits ok under the original cover, however my cover is cylindrical and came with the bike but I have seen others which are bowl shaped. Any way I suspect there will be a number of semi modern lightweights out there with similar alternator systems and it will be a matter of searching around to get one which is suitable.  Because the drive is off the idler the rotational speed is  approx 1.25 engine speed that means the alternator is probably rotating in the range of 2500 to 3750  revs for normal riding which is in the  range of reasonable generation for a two stroke alternator.
ChrisS



Edit: Image added 14/12/2007.  A.



[edit image links from http to https, Doug, Site Moderator, 04Dec18]
« Last Edit: 04 Dec 2018 at 21:50 by Doug »

Offline Alan Cun

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Re: Alternators to replace BTH pancake dynamo
« Reply #5 on: 12 Dec 2007 at 08:16 »
Yes good one Chris I have often picked up those type Yamaha motors but just to use the small oil pump in Doug projects. But the last one (motor) lies on the floor. My good mate Des arrives for a visit on Friday to bring back completed my 32 Bulldog and take away to  finish the S1 projects. I am sure we will have much discussion on the Yamaha alternator as his E29 is missing covered by a flat plate. There was available from camping stores a stainless steel soup type bowl that was the perfect size for the cover. I was thinking of the alternator on some Kabota tractors but the bike one seems a better alternative. Again thanks for your input regards Al
« Last Edit: 12 Dec 2007 at 10:22 by Alan Cun »

Offline ChrisS

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Re: Alternators to replace BTH pancake dynamo
« Reply #6 on: 15 Dec 2007 at 04:17 »
I managed to find a photo of the components for my units which I sent in and has been posted. Of note is the drive gear which fits the muff coupling was obtained from HPC Gears Limited Foxwood Industrial Park, Chesterfield S41 9RN a good source for worm gears and sprockets.

ChrisS

Offline cardan

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Re: Alternators to replace BTH pancake dynamo
« Reply #7 on: 15 Dec 2007 at 08:48 »
Hi all,

We put up with (and hopefully enjoy and value) 1930 carburettors, 1930 motors, 1930 wheels, 1930 brakes... on our 1930 motorcycles. I'm wondering what is so terribly wrong with a 1930 generator?

Does anyone out there have a 1930 Douglas with a BTH generator that works OK? If so, perhaps they could share their experiences with us: What does it look like?  How does it work? How hard is it to rebuild? Where can parts be found? Is there an expert repairer?

Edin have you considered sticking with the original arrangement?

It would be a pity if all our running machines had authentic-looking covers masking Japanese alternators.

Cheers

Leon

Offline Alan Cun

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Re: Alternators to replace BTH pancake dynamo
« Reply #8 on: 15 Dec 2007 at 09:59 »
Hello All, Funny thing about my previous remark about talking to Des about fitting a Yamaha alternator. Would you believe the conversation lasted about 30 seconds. Des explained that he had put the dynamo on his E29 but as I can also verify it bangs against your leg with footboards and is more comfortable to have fitted just the flat plate. Now I have a mate who attends swaps up here in Qld and sells a small bike battery for around $10. Now Des is happy to hide one of these in an old case if the need arises for electrical power. Now in the past I have loaned the cone clutch set up that operates the drive to the dynamo, but with the several bikes I have fitted with the dynamoes they are just for show and none are rotating.. The other point being they run from the magy gear at top cam gear speed to a small dynamo gear, Dont know what RPM that means but a considerable amount of power would be lost in overcoming the permanent magnet and charging. I can also say how soft the timing gears are on a pre war Doug and an additional load is additional wear.  Now I remember the late Andy Clarke for what ever reason going to the trouble of re-magnetising  the almost full circle magnet. An aircraft engineer was successful after many knockbacks from tradies. Now I dont know how many riders ride their trusty restoration after dark, but if your rallies are anything like ours the first or third or more drinkies has long passed the lips before the sun goes down. Not looking for an argument on the subject just a few observations. One other trade secret is an orange Hawker gel battery of around 20 amps ex Telstra size of a brick 10 years old still got enough grunt to jump start a V8 keep an eye out at your scrap metal dealer. I have bigger examples in a lot of my collector vehicles( some havent been charged for months and still hold 12.6 volts)  regards Al

Offline Doug

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Re: Alternators to replace BTH pancake dynamo
« Reply #9 on: 15 Dec 2007 at 15:51 »
Quote from: cardan
How does it work? How hard is it to rebuild? Where can parts be found? Is there an expert repairer?
Work?  Not very well, output is about 20 watts maximum. In countries (like Edin's) where they require daytime running lights, even for vintage vehicles, the dynamo just can not keep up.
Rebuild? It is a permanent magnet, four pole dynamo, so is quite simple in construction. Short of the armature or commutator being damaged you are looking at replacing the brushes and if needed, ball bearings. It is recharging the four-pole ring magnet that is the problem. No one wants to touch them as they are likely to make them weaker rather than stronger. You can not charge one set of poles and then the other, they both need to be done simultaneously. That requires special kit that was likely last seen at the BTH factory! What needs to be done is special pole pieces made so it can be done on a standard magnet charger. The reward for all this trouble is a full and blindingly bright 20 watts output.
Parts?- Nonexistent since the mid-thirties. You collect other BTH pancake dynos and hope for a stronger magnet. Lucas brushes can be filed down to fit.
Experts? Nope, everyone looks after their own. Most have been removed and a blank-off plate installed!
But if you like to ride your bike a lot, then you do what you need to, or have several swappable batteries on standby!

-Doug

Addendum- I have been told the BTH Pancake dyno was used on the early LE Velocette, continuing availability into the early forties.
« Last Edit: 15 Dec 2007 at 20:01 by Doug »

Offline cardan

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Re: Alternators to replace BTH pancake dynamo
« Reply #10 on: 16 Dec 2007 at 05:01 »
Thanks Doug - a fascinating description of a rather primitive device! Apparently there is a similar problem remagnetising some Villiers flywheel magneto magnets. I understand that there is a genuine factory device for the purpose still existing here in Adelaide - you'd think that there might be a BTH device lurking somewhere!?

Let's imagine that there was a way to remagnetise the magnets. What can be done with 20 W? These days probably quite a lot! Halogen globes are now very bright at relatively low power consumption, and I see people advertising around the place with halogen globes on old-style fittings. For the rear, I'm sure that a cluster of super-bright LEDs could be adapted into the base of a standard bulb to give a bright tail light. It's common now to see bicycles with fabulous lighting systems, and I suspect they all are working with less than 20W.

The poor old BTH pancake generator seems to be a threatened species, but I wonder if this needs to be the case? Being so simple, it should be quite reliable in service (I guess less idealistic people that me are laughing now?). Perhaps the club, in conjunction with a repairer, could invest in a set of adaptors to fit a standard remagnetiser? Couple this with some better globe technology? STP! (Save The Pancake!)

Leon (whose bikes are mostly too old for electric lights...)

Offline Doug

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Re: Alternators to replace BTH pancake dynamo
« Reply #11 on: 16 Dec 2007 at 05:25 »
Since this thread is about alternator conversions, I have started a new post here-

https://www.douglasmotorcycles.net/index.php/topic,2461.0.html

with some pictures of the various BTH pancake dynamos and what is inside them.

-Doug

Offline graeme

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Re: Alternators to replace BTH pancake dynamo
« Reply #12 on: 16 Dec 2007 at 20:58 »
Have to agree with Doug here - if you need lights that work, it really makes sense to upgrade the electrics. And in this case the new alternator can be hidden under the original cover, so nobody would pick the modification in any case.
I have done something like this with our Austin 7 - where the generator will throw the solder out of the windings if you try to get decent lights - even when using low wattage halogen bulbs. Fitting a modern solid state regulator has transformed the electrical output, and I could drive with the lights on all the time if I wanted to - with bright 35W halogen bulbs fitted. These are actually very good lights at night.
If a modification can be hidden from view I can't see anything wrong with it - otherwise we would be stuck with original cast iron pistons, dodgy original valves, mica condensors for magnetos, felt oil seals, old style sealants etc etc. Why not make old vehicles more practical? 

Offline Edin

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Re: Alternators to replace BTH pancake dynamo
« Reply #13 on: 10 Jan 2008 at 20:40 »
He all.
I would like to build an small alternator on my Douglas T6 1930, in such a way, that the original BTH cover can hide the alternator. I wil be happy for any help and advise for this project if somebody have any experience to share.
Many  in the North hope for a solution,- they have the same problem.
Regards Edin DK.

He all
Thanks for great interest,- help and support with my project to build an alternator on my 1930 - T6.
The job is done,- the test is finish and the result is good. The test outcome was following : 14volt - 10amp - at 2000 rev./min. The alternator I build on, came from a small KUBOTA dieselengine.
The price for the alternator is doubtful - "a small part in an bigger deal" - about 150,- and to this I have to add
a SPARX  regulator rectifier at 30,- + Vat and shippingcost from UK.
As illustration to the job enclosed a fotoserie there step by step shows you what is done.
regards Edin DK.













































[edit image links from http to https, Doug, Site Moderator, 04Dec18]
« Last Edit: 04 Dec 2018 at 21:51 by Doug »

Offline Dave

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Re: Alternators to replace BTH pancake dynamo
« Reply #14 on: 10 Jan 2008 at 21:50 »
Photo series added.

 

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