Mamod Locomotive

A very popular starting point for Live Steam. With their low cost comes a number of problems which can be discussed here
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Tony Bird
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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.


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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.

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Original and replacement bolted bushes.

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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.

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

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Finished.

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Regards Tony.

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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.

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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.

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

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Valve block fitted in chassis.

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

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Completed valve assembly with spring strengthened.

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

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Silicon tube fitted to throttle/reversing lever.

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Work so far done to the model.

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Cylinders next!

Regards Tony.

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

Hi,

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

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Removing the cylinders usually breaks the steam passageway gaskets.

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The cylinder shows no wear at all.

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

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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.

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

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Cylinder apart and jigs used.

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

Regards Tony.

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

Started on the cylinders. First the bore was lapped.


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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.

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The slot is turned with a parting graver.

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The slot finished.

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

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

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That is it for today.

Regards Tony.

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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. :)
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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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.

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Drilling the ports larger in the cylinder.

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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.

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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.

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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.

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

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Nearly finished cylinder assembly.

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Regards Tony.

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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.


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

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The original Safety Valve.

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

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The original valve apart.

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Altered.

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Assembled.

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Original steam pipe plugged.

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Safety Valve attached to the boiler.

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Steam dome with flat top fitted.

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I think I have a day off tomorrow.

Regards Tony.

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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

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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.

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

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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.

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Regards Tony.

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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!

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Some silicon sealant on the reversing block.

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Reversing block fitted.

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

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Chassis air test.

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Chassis steam test.

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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.

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Regards Tony.

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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

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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.

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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.

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Regards Tony.

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Post by Tony Bird » Thu May 08, 2014 2:24 pm

Hi,

I haven't decided decided on how or where the lubricator will be fixed, there isn't much room on the footplate. So while I have been cogitating the regulator has been partly made and fitted.

The connections for a pressure gauge and the regulator valve have been blanked off. Initially the reversing valve will be used to regulate the steam.

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A meths burn has been made as it didn't seem practical to fit a ceramic burner as a flexible gas pipe would be needed. Years ago when the only real alternative to solid fuel was meths, Merlin did make and supply radiant gas burners for Mamods but these were not very good and quite expensive. There were a few meths burners of different designs commercially available but a lot of us made our own.

The following is of one I made a lot of, its design is borrowed from several different designs. In the early days of 16mm Scale when meths burners were the norm the track used wasn't very good. The use of Hornby tin plate track was quite common when left in the elements it became very rust and uneven and model locomotives quite often came off the track! So a design of meths burner which didn't dump all its flaming meths out if the model fell on its side was a good idea. This burner gives at least a few moments to right the model if it does leave the track.

First the filling tube goes to the bottom of the tank so that it can be fill and nearly emptied using a syringe. When soldered in the filling tube is bent to the right which means that if the tank is on either of its sides or even upside down little fuel will come out of it.

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There is an overflow pipe fitted which comes out the same side as the filler tube bends. When filling as soon as meths comes out of the overflow a certain amount of meths is drawn back into the syringe to allow for the expansion of the meths as it heats up. If meths does come out of the overflow it is deposited on the side of the track well away from the burners.

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The meths tank itself is quite heavy which compensates to a certain degree for the weight at the front of the model. This photograph shows the tank hard soldered together along with the burner tubes and their feeder tube. The feeder tube goes to the rear of the tank so if the model is tipped forward not a lot of meths will be spilt from the burners also the holes from the feeder tube to the burners are kept small also to reduce the flow of meths if there is a spill.

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This design doesn't stop the burners flaming but does slow it down.
The burner all hard soldered together except for the bung in the end of feeder tube which is soft solder to allow the tube to be easily cleaned if necessary. I always fit a removable bung on all my meths burners but I have yet to have had to remove one, but if I don't fit one!

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Burner painted with VHT paint.

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Burner fitted in the frames of the model it is secured by a bolt to the footplate and the front flame guard is sprung into the frames.

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Part of the carriage footplate has to be cut away to clear the burner parts.

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As the model looks today. Next will be a filler valve to give more time to think about the lubricator position.

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Regards Tony.

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Post by LnBmad » Thu May 08, 2014 3:05 pm

That's a great discription of how to build a meths tank. Some useful pointers I will be taking with me from that I know
If it can be made full scale it can be made 16mm

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Post by Tony Bird » Fri May 09, 2014 8:48 am

Hi,

Yesterday made my version of a Goodall valve.


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The steam pipe has been taken through to the back head, but still not decided how the pipe work and lubricator will be mounted, we are away for a few days so maybe inspiration will strike.

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I hope to meet up with three Queens this afternoon!

Regards Tony.

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Post by KNO3 » Sat May 10, 2014 8:21 pm

Very nice work. Are you going to use a simple lubricator or an adjustable one? I would recommend the latter.

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Post by Tony Bird » Sun May 11, 2014 7:57 am

Hi,

Are you going to use a simple lubricator or an adjustable one? I would recommend the latter.

As there isn't a lot of room a simple one.

Regards Tony.

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