New member needs a large OHC dynamo

[Ian Grace]

Another new member, Lee Robertson, has acquired the ex-NZ re-paneled fabric saloon, and is in need of a replacement late/large diameter dynamo. Can anyone help him?

Ian

[Ian Grace]

Actually, Lee has the smaller diameter dynamo but has been quoted GBP 450 + VAT to rebuild. Can anyone recommend a dynamo rebuilder that might be less expensive? The chap I used to use retired!

[lee_rob]

Thanks for posting this Ian, would prefer the larger one if I can get my hands on one as it would give me a few more amps but am I right thinking I need to change the nosepiece to fit this on? Any idea what I should expect output wise on my current DEL24?

[Ian Grace]

Hi Lee,

Yes, the nosepiece would need to be changed, which isn't an afternoon job!

As for output, neither dynamo will show positive charge with the headlamps illuminated. The early dynamo cars had 16-0-16 amp ammeters fitted, while the later cars had 20-0-20 amp ammeters. One common problem with either dynamo is adjusting the third brush too far in an attempt to get positive charge with the lights on - you run the risk of melting the solder in the commutator.

[lee_rob]

I would never expect any vintage dynamo to keep up when headlights are on, I currently have a discharge of about 11-12 amps with all my lights on, so I would expect to reduce this down to 6 or so with the dynamo going. With my 80 a/h battery i should get a good 8 hours motoring before it fails if I donlt use the starter.

[Toby]

There is a good guy who does them, can build in a current regulator too, can't find details at present but he's in lincs and has beeen mentioned before so should be in a previous topic, ...

[garagiste]

I am at present looking into the use of LEDs for stop, rear and side lights - this should ease strain on the dynamo. Suitable 12v LEDs more readily available than 6v.

Have converted with success a number of old bicycle lights, for use on my 1930/40/50s bicycles, to LEDs. In fact use modern LED cycle lights at night on the rear of the M type as they are very effective and can be mounted and removed with ease.

Would be pleased to hear other peoples experiences with LEDs. Perhaps a new thread?

[plj]

Classic & Vintage Dynamos Ltd of Notts 01623 747666 have a good reputation, reasonable price and quick turn around. With regard to LED's I am looking for some easily mountable/demountable ones as running lights and indicators using a separate loom with concealed connectors.

Regards,

Philip

[lee_rob]

Thanks Philip I shall give them a call in the week and see what they quote for repair of my current one

[Ronald]

I used them to rebuild the dynamo on MT, however, i think i connected it wrong, it still doesn't work..............!

[lee_rob]

Can anyone give me the dimensions of the different mounting holes for the dynamo on the early and late engine nose pieces. I need to find out if I have an early one or a late one which has been modified to take an early dynamo. It makes a significant impact on the cost as to get a correct nose piece is going to cost me £285.00+VAT plus the hassle of taking the engine out to change it. I have found I can buy a reconditioned 6V larger dynamo for £486.00+VAT so if I have the correct nose piece this isn't too bad. If I dont I have to decide whether I get a nose piece or just have my current dynamo refurbished and live with the smaller output.
Your help would be appreciated guys.

[ian judd]

I believe there is also a difference in the front of the block, with blocks for the smaller dynamo being flat at the front, and blocks for larger dynamos having a 'scoop' out of the front. If you have the early block a large dynamo may not fit even with the later front housing fitted - it will ( I think ) foul the block. Modern dynamos based on the Lucas C40 have a very slightly smaller diameter but I don't think it's enough.
Are there any smaller 'modern' dynamos that could be converted ?
( I have a spare later front housing if you need it ).

Ian

[lee_rob]

Hi Ian,

I have the later block its a 31 engine (No 31672A) so should take the later dynamo, thank you for the offer of the housing I will bear that in mind it turns out I need one.

Lee

[Ian Grace]

Ian,

I always thought that you couldn't fit a later dynamo in front of an early block, but the tourer I bought in Kansas City had this arrangement. It was a close fit, but there was clearance, and the dynamo wasn't modified in any way. After making this discovery, a couple of M Types with the same arrangement emerged.

[lee_rob]

Hey guys

Been a while so I though I would bump this thread in case anyone has a small dynamo that they would sell, I will be at Pre-war prescott this weekend with I hope a fully charged battery to keep me going

Thanks