Does a dynamo have to turn the correct way if arrow points clockwise will it work if turning anti clock wise
Thanks Ian

email (option): Ian.baldockapps2@btinternetcom

It won't work in the opposite direction unless you swap the wires round inside. Ron

email (option): ronpier@talk21.com

Isn't it also the case that the brush holders are set slightly differently ?

Yes they are...There is a different brush holder plate depending on direction of rotation..It's to reduce brush wear...Ian

email (option): ian@wright52.plus.com

Could I swap the wires over to get it to work if so what do I need to do How long before the brushes wear out if it's the wrong direction
Thanks
Ian

email (option): Ian.baldockapps2@btinternetcom

I didn't know about the brush plate holder being different, but BSA Service Sheet 808 (negative earth) and BSA Service Sheet 809A (positive earth) show the brushes swapped round. Both service sheets are for A, B and M models. The dynamo direction of rotation for these bikes is the same.

I was going to ask Noam about this, but didn't get round to it.

ps I think the wires Ron is referring to are the field coil wires.

email (option): sacombsashtrees@hotmail.com

Yes Noam would be the best bloke to comment. But if you lay the dynamo on a vice and motor it in the normal testing mode and then swap the field coil wires, I'm sure it will motor the opposite way.

This PDF lucas sheet might be useful. /C:/Users/ronpi/Downloads/Lucas%20dynamo%20(4).pdf


Ron

email (option): ronpier@talk21.com

Well I tried that as a clickable link with Sven's instructions, but I've cocked up somehow. Ron

email (option): ronpier@talk21.com

Hi Ron

Yes it will do as you say. I have an E3L on the bench. Both wires from the field coil were black and the same short length, so I didn't know which wire went where. A little bit of trial and error got it to motor in the right direction.

I was thinking about the brush holder plate too. In my mind, the brush holders are two brass holders riveted onto a brown tufnol plate. The carbon brushes are held in place by wibbly wobbly springs. I just can't see this set up as being precise enough to be rotationally sensitive. Maybe the concern is the leading edge of the brushes digging into the grooves of the commutator.

So, my personal view only, is that depending on the bike's useage, the brushes could last for some considerable time. Especially if you give the commutator a good clean once the brushes have bedded in (or if I am wrong, worn down to nothing in a very short space of time).

Thinking through the brush positioning (808 v 808A) I came to the conclusion (rightly or wrongly) that it cannot matter. The way I looked at it was if the brushes were at say, 12 o'clock and 6 o'clock (I know not physically possible, but that was the way my brain worked it out) so long as the "Field brush" was earthed and the other brush went to "D" the wiring of the brushes stays the same; the same as turning the dynamo upside down.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Concise Patrick! Ian the original poster now has something to experiment with and it sounds like he has nothing to loose.
And to make amends for file I tried to upload, here is a scan of the relevant page which shows the two field coil wires to swap. Ron

email (option): ronpier@talk21.com

From the Brightspark pages :-



200431 is clockwise and 432 anti-clock.

I believe that it is to do with leading and trailing edges and the aramture centre line.

How much difference it makes will probably depend on the brushes used and the state of the slip ring...but there must have been a reason for Lucas doing what they did and increasing the spare parts inventory accordingly. Any extra wear means extra dust and unreliabilty. It certainly wouldn't be fair to ever make Lucas jokes again if the incorrect parts are knowingly used.

Bearing in mind that most MO1 magdynos are anti-clock with corresponding clockwise dynamo, it shouldn't be too much problem to find a second hand brush holder.

Thanks for that Rik. I didn't think there could be a difference.

My thoughts were based on a brushed cordless drill perspective where clockwise and anti-clockwise rotation is used.

email (option): sacombsashtrees@hotmail.com

Hi Rik

I have just had a look at a Lucas E3LM and I get your point. I have not noticed it in the past, but the brushes are not exactly at 12 o'clock and 6 o'clock, they are (not being precise, but to illustrate your point), they are at 10 to 12 o'clock and 10 past 6 o'clock.

Every day is literally a school day!

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Here is a more detailed view of the two brush holders - mirror image construction.
The alloy end pieces are also mirrored.

email (option): rays54@hotmail.com

Thanks to all who replied I swopped the field coil wires flashed the f terminal started the bike and it charges fine
Thanks
Ian

email (option): Ian.baldockapps2@btinternetcom

Thanks to all I know the brushes will not last as long as intended but the bike will only do a few hundred miles a year so I can live with that I do wonder how many dynamos are on bikes with the wrong brush plate ( just a thought )

email (option): Ian.baldockapps2@btinternetcom