About Comments

Comments are enabled on all postings. Click a posting to find the comment box. Comments are moderated and appear after my review.

Wednesday, 13 August 2014

My Dapol M7 Bogie Wiper Contacts Broke

If you have insulated frog turnouts then failure of the bogie electrical pickup renders the locomotive pretty useless as it will stall on the frog without the bogie pickups conveying that additional source of power at the other end of the locomotive to the driving wheel pickups.

The bogie wipers make contact on the electrical collection strip that is fixed to the chassis. It is not a very reliable connection and if you fiddle with the wipers trying to remake a failed contact then they will eventually break, most likely on the bend. Furthermore, if the bogie is removed and refitted then the wipers can get trapped between bogie and chassis weakening them.

I have never liked the fallibility of this part of the design but cannot think of an alternative to convey power from the bogie to the motor whilst allowing it to be removed for servicing. But I have come up with a method used to repair broken wipers. This only works of course if there is still part of the wiper remaining.

I used 0.2mm wire. One end is soldered to the chassis collection contact and the other end to the bogie wiper. We have to take care not to melt the plastic. Just a touch of the iron and solder on the contact and wire is enough to form a solid joint.

The wire needs to move in unison with the bogie as it rotates on its pivot. This is achieved with an omega loop formed in the wire (although in practice mine is a semi-circle). The loop opens and closes in unison with the bogie as it rotates. There is some spring back of the bogie but no more than the original and it goes around 9 inch curved track without derailing.

This is a far more reliable electrical connection than the original design but removal of the bogie is now compromised. If it needs to be removed for servicing I'll probably have to desolder one end of the wire(s).

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...