Mamod Locomotive leaking reversing block

A very popular starting point for Live Steam. With their low cost comes a number of problems which can be discussed here
Post Reply
User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Mamod Locomotive leaking reversing block

Post by Tony Bird » Tue Dec 02, 2014 12:15 pm

Hi,

Some of I hope only the older Mamod parts aren't very accurately made.

A regulator reversing block for a Mamod Locomotive.

Image

These misaligned holes can leak and cause poor steam characteristics and if the leak is seen it it often attributed to the cylinders or the reversing valve.

This leak can be cured by using 1/8" OD K&S tubing. The reversing block is screwed to one of the frames and the holes for the steam on the frames filed so the line up with the holes in the reversing block (they don't necessarily do so) . A 1/8" hole is drilled through the frames and about 7 mm into the reversing block. With the reversing block removed from the frames short lengths of 1/8" brass tubing are Loctited into the holes and allowed to protrude about 1/16". The same is done with the reversing block fitted to the other frame. The holes in the frames are made a little larger to make the brass tubes an easy fit in them. The tubes are then filed flush with the frames. When finally assembling the faces and around the brass tubes are coated with silicon sealant before being fitted to the frames. This is done without fitting the cylinders which allows any excess sealant to be removed. When the sealant has set the cylinders are fitted.

Modified reversing block.

Image

Dry assembly of reversing block in the frames.

Image

Image

I hope this is found useful.

Regards Tony.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest