Reverse Polarity ??

[bobby]

Hello,

I am new to the forum and hope to enjoy the e-speak with other Loco enthusiasts.....

I have purchased among other interesting Trains a Dapol 0-6-2 Tank N2 Class D51. The loco runs perfectly........apart from running in the wrong direction i.e.forward is back and back is forward. Unlike a lot of other models where reversing wiring or repositioning the magnet, I can see no way of changing things and ask if anyone can help me. The Armature housing, which is the pre-formed magnet cannot be reversed or changed around of course, and there appears no wiring to be re-located. Indications are that I appear, maybe, the first person to have opened the body, so there looks as if no previous tampering has taken place. Any help would be appreciated.
Thanks in advance
BobbyG

ps cannot load the photos I prepared because too large !

[Mountain]

I am not sure... As you mention that it has a circular fixed in magnet it is puzzling. I once had a Dapol N2 but I never needed to open it up, and sold it on in pristine condition.
The natural thoughts are to look at the wiring... But you have looked at that.

But one quick note. Are you intending to wire it for DCC? If you are there is no need to change it as the direction can be altered via the programming. However with DC, you have already covered the main aspects. Not easy! Hopefully someone can say more.

[Flashbang]

Have your tried reversing the two wires that feed the motor? That should reverse the direction of turning of the motor, thereby reversing direction of travel. There has to be two connections to the motor somewhere?
If you cant see them, how about the two wires that come up from the wheels/pick ups. Reversing these will do the same on DC.

[Bigmet]

Trying to remember how the connections between pick up wiper strips and brushes were made as produced. I think it was by the ends of the pick up wiper strips sprung against the brush terminals, no insulated wire connections to be seen.

If you take the motor out, (it is retained by a single screw roughly above the pony truck wheelset, so remove the rear truck first!) then all becomes clear. Bend the end of the wiper strips out of contact with the brush terminals, solder wires one on each wiper strip end, and take them each to the brush terminal they didn't previously contact, and you are done. (I didn't do it for this reason, but to enable conversion to DCC, very quick and simple on this model.

Caution. Work around the pick up wiper strips carefully, they are retained on the plastic chassis by little melted over pegs and can easily be ripped off if they snag on the sleeve of a knitted pullover. Then you have to find some miniature self tappers to screw them onto the chassis side...

[End2end]

ps cannot load the photos I prepared because too large !

Hi bobby and welcome to the forum.
Here's how to quickly resize your pictures.
viewtopic.php?f=42&t=53064&hilit=resize#p652047
Thanks
End2end

[bobby]

Thank you for your replies, much appreciated. In the first instance I am going to go down "Bignet"'s route but would really like him and others to see the photos now that I have broken down the train into components. "End2end" has kindly sent me a link on how to downsize photos for the forum, but I have an Applemac computer and think his guidelines were using Microsoft. Is there any possibility that I can send the photo's to Bignet as an email attachment which would be very simple. I cannot understand why the polarity has altered without human intervention, there are "no" wires at all in the loco and the wiper strips are already bent out at the ends. Your continued indulgence is very much appreciated.
Bobby

[End2end]

Ahh yes sorry about that bobby. They are indeed instructions for windows.
Thanks
End2end

[Bigmet]

...I cannot understand why the polarity has altered without human intervention, there are "no" wires at all in the loco and the wiper strips are already bent out at the ends...

Bobby, it's no problem answering your questions, I am pinned down by a duty and this is a fun way of using the time.

Simplest probable answer is that the motor was misassembled with the magnet inverted. Dapol at the time were a tiny operation, essentially David and Polly Boyle - see where the name came from? - and this product was being made from a stock of bought in parts and production from the tooling, all obtained from the defunct 'Mainline' business. Either the assembler didn't notice it ran wrong way, and off it went for sale, or it may even have been sold at reduced price as a 'second' because it ran wrong way, there was a lot of that going on in the 1980s.

The computer I am using here is a hulk, and almost certainly won't open an e-mail photo attachment I am afraid. If you can see the wiper strip ends where they contact the motor brush terminals, all you have to do is swap them around with wire links to get 'right way' running.

I'll send a PM with my email address, and we can try...

[bobby]

Thank you Bigmet its all most appreciated.

Now this is going to sound strange !! I cannot see/find a "separate" magnet unlike all the other locos in oo gauge etc, where its all too obvious. It looks like the whole of the armature housing is magnetised, therefore you can understand why I cannot reverse it being a moulded unit.I am definitely missing something, the old brain isn't as sharp as it used to be being 20 years retired ! Thats why I need for you to see the photos, and no doubt you will see straight away.....ahh !! thats what he's talking about. Look forward to your pm email to give it a shot, meanwhile I will photo again in very low megapixels to see if that works.
Regards,
Bobby

[Bigmet]

I have sent the pm with my e-mail addy, in case posting the picture fails. There should be '1' (or greater) in the Private Messages box, top right of the header bar.

Now the motor that Dapol fitted in the N2 - in the one example I have - was exactly as in the original Airfix GMR design that ended up released by Mainline. This was a large open frame five pole motor of much the same layout as the Triang XO4, with the usual block magnet at the end. Illustrated here in the 14xx tank engine, also designed by Airfix GMR. http://www.airfixrailways.co.uk/Motors.htm

[bobby]

Established with help from "Bigmet", that the miss-shaped piece of metal attached to the inner housing, was in fact the magnet, which had magnetised all of the armature housing body. I have turned the magnet upside down and now she runs perfectly .Looks like Someone has at some time, replaced the magnet and cut it (with a blunt saw) to fit the engine, I thought it was an extra weight holding the back down!!

Anyway thanks to Bigmet and you all for your help.

Bobby

[Bigmet]

Excellent. What else have you got?