Mamod Locomotive

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

Mamod Locomotive

Post by Tony Bird » Mon Apr 28, 2014 10:02 am

Hi,

While at the 16MM NGM Show at Peterborough I bought a Mamod Locomotive. It seemed never to have been steamed but had its cab back and burner tray missing so for £65 it became mine.


Image

These days there are plenty of very good up grades for Mamod Locomotives that make them work better. I thought it might be interesting for members to know what Deryk Goodall along with others including myself did to Mamods to get them to do a reasonable job of work in the 1980's. Most of the following ideas used were thought up by Deryk and were published I think in 16MM Today many years ago by Peter Jones.

After the model was taken apart the first job to be tackled was to stop the axle bushes rotating in the frames, if left unchecked these bushes wear badly on their outside because of the thin frames. One way of stopping this rotation is to use a ball end punch to slightly close the hole in the frame making the bush a press fit. Another is to make new bushes which are bolted into the frames as I think was done on IPE's Jane, but to use these it on a Mamod it needs the wheels removing and replacing on their axles.

As original.

Image

Original and replacement bolted bushes.

Image

A way I use needs a thin strip of K&S rectangular section brass.

First a flat is filed on the flanges of the bushes.

Image

The K&S brass is drilled and filed and held to the frames by the exiting stretcher screws.

Image

Finished.

Image

Regards Tony.

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Mon Apr 28, 2014 5:46 pm

Hi,

To continue with the up grades to the locomotive. The throttle/reversing valve was played with today. A lot of people know about finishing the faces of the valve and valve block and increasing the strength of their spring. What might not be as well known is sometimes the steam leak attributed to the valve can be added to by a leak between the the valve block and the frames. As made unless things have changed there is no seal between the valve block and the frames. As the frames are painted and the ends of the valve block can be roughly finished often no matter how tight the screws are tightened there still can be a slight leak which might not me apparent. One solution after finishing the ends of valve block smooth it can be sealed to the frames using silicon bath sealant making sure that the steam passageways aren't blocked with the sealant.

Sometimes as in the case of this model the steam passageways don't line up well with the holes in the frames.

Image

Though it will work, it will work better if the holes line up. The holes in the frames can be made larger with a file to improve things. They can then be sealed in the way mentioned above. To improve things more 1/8" K&S brass tube can be introduced to improve the joint. Having filed the hole in the frame a 1/8" hole can be drilled through the frames and into the valve block and a tube Loctited in.


The valve block as it was removed from the model.

Image
Image
Image

The valve block with its burrs removed and the brass tubes fitted.

Image

Valve block fitted in chassis.

Image

The valve face cleaned up and the excess solder removed from one of the steam slots.

Image

Completed valve assembly with spring strengthened.

Image

The exhaust pipe cut back and a silicon tube fitted nearly to the top of the chimney. This makes assembly a lot easier.

Image

Silicon tube fitted to throttle/reversing lever.

Image

Work so far done to the model.

Image

Cylinders next!

Regards Tony.

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Tue Apr 29, 2014 9:39 am

Hi,

Late yesterday I made a start on the Mamod locomotive cylinders.

Image

Removing the cylinders usually breaks the steam passageway gaskets.

Image

The cylinder shows no wear at all.

Image

While visiting Tilford I bought a number of old Mamod locomotive cylinders.

Image

I have an idea on how to fit '0' rings to the piston with out removing it from its rod. First the piston had to be removed from its cylinder. A 13 mm hole needs to be drilled in some metal or hard wood. The cylinder is placed plain end down into the hole and the hole in the big end is filled with a suitable dowel. The big end is hit with a hammer and the cover comes off.

Image

A metal or hard wood rod is then used to remove the other cover.

Image

Cylinder apart and jigs used.

Image

After cleaning up the bits with luck today I will try and fit an '0' ring to the piston.

Regards Tony.

User avatar
DLRdan
Driver
Driver
Posts: 1083
Joined: Wed Nov 12, 2008 12:05 am
Location: Blyth
Contact:

Post by DLRdan » Tue Apr 29, 2014 11:33 am

A very interesting thread, I've never seen either of those fixes before. I'd be interested to know how you are going to stop the mamod piston rotating on the rod while it is machined.
Dan,

James: "Dan, can you use your hearing and tell me if that trains coming ?"
DLR
www.freewebs.com/dlrail

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Tue Apr 29, 2014 5:01 pm

Started on the cylinders. First the bore was lapped.


Image

Image

Image

This is the bit I wasn't sure about. Before I have always made new pistons to fit '0' rings to for Mamod cylinders. I had to make an over hanging 'T' rest for turning and a female centre to support the big end. The cylinder cover was held out of the way using masking tape on the piston rod.

Image

The slot is turned with a parting graver.

Image

The slot finished.

Image

'0' ring fitted nearly got it in the centre sorry poor photograph.

Image

The one cylinder cover was pressed in using a vice and the other using a hollow punch and hammer, again sorry poor photograph.

Image

That is it for today.

Regards Tony.

User avatar
ace
Fireman
Fireman
Posts: 291
Joined: Sun Jul 14, 2013 9:03 am

Post by ace » Tue Apr 29, 2014 9:01 pm

I am amazed that no one has commented on this thread until now Tony. I will echo what I have said on the UMF. Nice set of modifications and I am looking forward to seeing more and the fabrication of the lubricatior.

Thank you for sharing, they are a valuable set of photos for good reference. :)
YouTube ChannelImage

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Thu May 01, 2014 8:57 am

Hi,

A track test was done and it was found that the carriage wobbled a lot caused by it having a high C of G.

Image

So some supporting rollers were fitted to the bogie frames which cured this. Compliance between the locomotive and carriage being accommodated by their pivot on the buffer beam.

Image

I was about to remove the balloon chimney and fit a parallel one when I remembered I had a Mamod Locomotive with one so they were exchanged.

Image

Image

As the model tram engine looked at close of play yesterday. It is stood on a reverse curve of Mamod track which is used to check that coupling angles will work. The premise being that if the train will go through this length of track it will go through any track that it is likely to encounter.

Image

As I have had to order more 3/8" '0' rings work will crease on the cylinders until they arrive so a start will be made on the boiler.

Regards Tony.

LnBmad
Trainee Driver
Trainee Driver
Posts: 881
Joined: Fri May 31, 2013 10:17 pm
Location: Coventry

Post by LnBmad » Fri May 02, 2014 6:58 am

A very interesting read... Nice to see some engineering solutions to the common problems with these little locos
If it can be made full scale it can be made 16mm

My line: http://gardenrails.myfreeforum.org/about7200.html

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Fri May 02, 2014 8:57 am

Hi Paul,

The 3/8" '0' have been ordered and I was going to start on the boiler but decided to clean up the 8 Mamod cylinders ready to fit '0' rings to that had been bought at Tilford. These cylinders were very greasy and dirty but looked as if they had never been used just stored badly. One of the cylinders was missing a cylinder cover and its piston was loose.

As bought.

Image

After taking apart cleaning in paraffin, cleaning in caustic soda, scratch brushing, drilling the ports bigger, lapping the cylinders, cleaning again in paraffin and finally boiling in washing soda.

Image

The ports were drilled larger to improve steam distribution especially the exhaust. As can be seen from the drawings at the end of the stroke the piston nearly covers the port and there is a lot of lap between the ports in the cylinder and port block.

Image

Image

So the lap can be reduced almost to nothing by drilling the ports larger. As can be seen on the port block on the right with its 2 mm ports there is about 3 mm between the edges of the ports. The easiest way to reduce the lap is to partially drill the port in the cylinder to 2.9 mm or a little less than the distance between the ports in the port block, this can varie even on the same port block! This can be done without taking the cylinder apart. If the cylinder is apart it is better to drill all the ports the same size as can be seen on the left port block where the ports are the same size as the space between them.

Image

Drilling the ports larger in the cylinder.

Image

A note on working on the working faces of the cylinder, port block, reversing valve and its block. It is not necessary to attain a polished finish just flat one. This can be done using a fine paper on a sheet of glass using a figure of eight motion.

Image

It is a good idea to check the port line up between the cylinder and cylinder block. When the best position is found mark the cylinder and its block so they will always be assembled together and the right way around.

Image

To tighter the cylinder springs stronger springs can be used or as with the reversing valve washers can be used. The 5 BA washers are too larger for the hole in the frames so either the hole is drilled bigger or the washers are turned down.

Image

To remove the burrs from the washers a cork and paper can be used.

Image

Nearly finished cylinder assembly.

Image

Regards Tony.

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Fri May 02, 2014 6:20 pm

Hi,

Blackgates sent the '0' ring which arrived this morning their usual quick service. I had started on up grading the safety valve so continued with this. Mamod boilers have only three way of getting steam out of the boiler the two bushes on the top and the steam pipe coming from underneath. So if you wanted to fit a filler valve the whistle had to go and if you wanted a regulator as well it had to be Roundhouse style with the safety valve in it.

However years ago we used to fit the filler valve or safety valve into the steam dome which is what I have done to the Lagos Tram engine.

Dome drilled to show a lot of room beneath it.


Image

The tram engine has a flat top to its steam dome so.

Image

The original Safety Valve.

Image

A drawing of Deryk Goodall's modification which increases the pressure and stops it dribbling.

Image

The original valve apart.

Image

Altered.

Image

Assembled.

Image

Original steam pipe plugged.

Image

Safety Valve attached to the boiler.

Image

Steam dome with flat top fitted.

Image

I think I have a day off tomorrow.

Regards Tony.

LnBmad
Trainee Driver
Trainee Driver
Posts: 881
Joined: Fri May 31, 2013 10:17 pm
Location: Coventry

Post by LnBmad » Fri May 02, 2014 6:25 pm

Great work tony!
If it can be made full scale it can be made 16mm

My line: http://gardenrails.myfreeforum.org/about7200.html

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Sat May 03, 2014 5:43 pm

Hi,

Returned earlier than expected but late enough not to want to get into fitting '0' rings to the pistons so some further work was done on the boiler.

Screws were fitted to replace the 'Pop' rivets that had been removed.

Image

The back head of the boiler was removed so that screws could replace the 'Pop' rivets. Soldering jig.

Image

Some further work was done the buffer beam which was cut down and its coupling removed and as no cab will be fitted a cross beam was fitted at the bottom of the boiler to support the rear of the boiler.

Image

Regards Tony.

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Mon May 05, 2014 9:31 am

Hi,

Some more work has been done on the model.

Did the other cylinder and this time I got the '0' in the middle!

Image

Some silicon sealant on the reversing block.

Image

Reversing block fitted.

Image

Gasket trimmed to clear steam holes they often partially cover them.

Image

Chassis air test.

Image

Chassis steam test.

Image

The model runns well and quite slowly but alas I still cannot retrieve both photographs and videos that I have put into Photobucket, so no video.

While the chassis was running in I fitted a couple more '0' ring to other pistons, one of which split as it had an uneven undercut and the cylinder that had a cover missing was split. I still have a few pistons to do which I hope are OK.

Image

Image

Regards Tony.

LnBmad
Trainee Driver
Trainee Driver
Posts: 881
Joined: Fri May 31, 2013 10:17 pm
Location: Coventry

Post by LnBmad » Mon May 05, 2014 9:34 am

Loving it!!! Can't wait to see it all finished.
If it can be made full scale it can be made 16mm

My line: http://gardenrails.myfreeforum.org/about7200.html

User avatar
Tony Bird
Fireman
Fireman
Posts: 395
Joined: Thu Jul 29, 2010 8:25 am
Location: Cardiff, South Wales, UK.

Post by Tony Bird » Mon May 05, 2014 5:33 pm

Hi,

Didn't do much work on the model today. We had to deliver a birthday card which we had forgotten to post to a friend and ended up buying a car!

I managed to finish fitting the '0' ring to the cylinders except for the broken piston and split cylinder one.

Image

The steam pipe has been extended so it will ft to a boiler mounted regulator via a lubricator. At meths burner was borrowed from another Mamod to check clearances of the steam pipe.

Image

Image


Regards Tony.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest