Dapol 2P tender drive

[Ken Shabby]

I recently bought a very cheap Dapol LMS 2P , which appears to have hardly ever run. I decided to dismantle and service the tender drive motor as it made a screeching noise and I thought that maybe some lubrication was needed. The problem is I can't get to go back together.
There are 2 small white cogs , one of which I can't work out were it goes. For now, I have put the motor back together minus the mystery cog, and when I applied power all the wheels turned .
Clearly this cog must do something, but I've spent all evening on it and I can't work out how it fits in the motor.
Does anyone have experience of servicing this type of motor ? , It seems to be very similar to the old Airfix 4F motor.
Kind regards, Ken

[Bigmet]

Almost certainly the same drive as the Airfix GMR 4F, as the 2P was another Airfix GMR product that went via Dapol to Hornby. So comparing to the 4F drive gear arrangement would be likely to help.

Sketch of the Airfix GMR tender drive in this original publicity material.
http://www.airfixrailways.co.uk/Motors.htm

[Mike Parkes]

The 2P originated with Mainline and none of the commentaries on Airfix GMR I have read make any reference to a 2P. Airfix had planned a 4P Compound but dropped that because of Hornby releasing their own. Other LMS locos Airfix planned to make were a Crab, Black 5 and 8F. Source Ramsay's British Model Trains Catalogue.

[Ken Shabby]

I have 2 Airfix 4Fs and they are both reliable runners, however I do recall one of them had to have a new tender drive unit about 8 years back, because I'd taken the old one apart and had not been able to get it back together . You'd think I'd of learnt my lesson.
Because of this I decided not to dismantle one again to aid the rebuild of my 2P.
After spending a couple of hours on it this afternoon, have decided that I will bide my time and try and find another cheap 4F /2P motor unit
Thanks for the advice.
Ken

[Mountain]

Some motor designs, some of the cogs go onto little bumps on the motor housing.

[Bufferstop]

Ken, you say all of the wheels turned, which is odd, did they all turn the same way? Is one of the cogs a double one with large and small diameters. Having been playing around trying different sizes of gears with the aim of building a motor bogie, I decided at one point to introduce an extra cog into the gear train. I ended up with an arrangement of holes that allowed me to switch back and forth between the original gears and the same set with an extra one added. The new bearing hole was covered by one of the original gears when I swapped back. Perhaps something similar happened in the development of your tender drive.

[Ken Shabby]

This week I bought a cheap Airfix 4F , which came in at well under £20 including postage. After a test run it took about 20 minutes to fit the tender drive unit into the 2P tender. I fitted the tender wheels from the 2P to the repalcement drive unit, as they were in far better condition to the the ones that came with the 4F which had perished and grubby traction tyres.
So the 2P is now running again and all the parts of the original drive unit are safely stored,and I may have another go at reassembling it in the future.
There's probably enough parts in the spares box to get the donor 4F running again, once I've finally got my head around how the tender drive unit goes back together.
Although they are a bit rough and ready these old Airfix tender drive locos are very powerful. For many years my old 4F was the the strongest loco on my layout.
Ken

[Mountain]

Is a good plan to take the working tender drive as an example to see how the others should fit back together correctly.