Mamod Brunel Exhaust Steam Issues

[Thornhill]

I have taken delivery of a new, latest (Dec 2019) Mamod Brunel loco. I was suprised to see that there is no exhaust pipe; steam and oil just exit the cylinder through a hole on the side. This will cover the loco with condensate, I believe. I have not yet steamed the loco. I have searched the internet forums and Youtube and some people have made their own exhaust pipes and even condensers. I do not have the skills to solder in exhaust pipes and do not believe I should have to on a brand new loco. Apparently previous versions of this loco had a downward pointing exhaust pipe. I phoned Mamod today and they just said they do not provide exhaust pipes any more and that's the way it is. There was nothing they could do. I believe they should have an exhaust pipe either directed down to the track (as they used to apparently) or up in the air close to the chimney, where condensate would stand more chance of dispersal and not cover the loco so much. Clevedon Steam make an exhaust condenser which may provide a solution but there would still be the problem of fitting the connecting pipe to the tiny and shallow exhaust port. It is threaded. Mamod told me today that the thread is 4BA. I threaded a copper pipe with a 4BA die (I can do this) but found it was much too loose. I don't believe it is a 4BA thread in the cylinder. Anyway, after a couple of thread turns any inserted pipe would start fouling the steam passages. I cannot silver solder in an exhaust steam pipe -beyond my skills and fiddly for an expert I inagine. Having just spent £500 (including canopy and boiler cladding) of hard-earned I just feel depressed over this loco.
Anyone with experience or ideas?

 

[trammayo]

If it's a split die you could have it 'open' or maybe have a back-nut! I presume you will have tried a wisp of PTFE tape (the one for gas is thicker).

 

[Paul M]

The good old Brunel, lovely little beasty but steaming can be a pain.
My 5 year old Brunel has a downward facing exhaust pipe. This is just a push fit into the hole. If you contact Dreams Steam, they may be able to help with a new or spare pipe. TBH Mamod haven't really thought this through, if there's no pipe, as you say, your loco will be ruined, or at least very cruddy. You may also find the steam oil only lasts a short while as mine hasn't a proper oil reservoir, and it ends up spraying and dribbling everywhere.
But when it goes it's great, obviously it's a lot cheaper than most steamers, so you have to make some allowances. Also let it coolooks right down between each steam up.

 

[dunnyrail]

Had a similar problem with Roundhouse loco’s sploging all sorts of crud over the body when just steamed up, was the condensate mixed with oil that is present in the cylinders before they get warmed up. My solution was to make a sort of ‘spark arrester’ looking device. It just sat inside the chimney and all the crud went into it via the internal pipe. A hole allowed the excess crud to drop back into the chimney and down onto the track.

The black arrow is just a hole out of the top of the circle for Steam.
Red arrow points to the tube that goes from the exhaust pipe into the top circle, there is a cap on top of this
The green blob is a hole for the crud to exit the pipe
The circle is made from larger tube or made up from flat to a circle

Mine was silver soldered but a soft soldered job should work just as well as the heat in this area should not be enough on a Mamod to melt the solder.

Size of this can be relatively small to represent a spark arrester often seen on yugoslavian ng locomotives and others As seen below.

 

[Thornhill]

If it's a split die you could have it 'open' or maybe have a back-nut! I presume you will have tried a wisp of PTFE tape (the one for gas is thicker).

Thanks. I can try that but the problem remains that the exhaust hole isver shallow. Just a couple of threads before you come to a steam passage.

 

[Thornhill]

Had a similar problem with Roundhouse loco’s sploging all sorts of crud over the body when just steamed up, was the condensate mixed with oil that is present in the cylinders before they get warmed up. My solution was to make a sort of ‘spark arrester’ looking device. It just sat inside the chimney and all the crud went into it via the internal pipe. A hole allowed the excess crud to drop back into the chimney and down onto the track.

The black arrow is just a hole out of the top of the circle for Steam.
Red arrow points to the tube that goes from the exhaust pipe into the top circle, there is a cap on top of this
The green blob is a hole for the crud to exit the pipe
The circle is made from larger tube or made up from flat to a circle

Mine was silver soldered but a soft soldered job should work just as well as the heat in this area should not be enough on a Mamod to melt the solder.
View attachment 259890
Size of this can be relatively small to represent a spark arrester often seen on yugoslavian ng locomotives and others As seen below.
View attachment 259891

Thanks for you description. I will have a think to see if I can apply any if it to my Mamod.

 

[artfull dodger]

Clevedon steam made me a 4ba to hose connector to allow me to fit that tank to my model before I passed it on to a fellow live steamer. Email him and see if he will make you one up. The tank and fitting worked great, I plumped a second chimney up thru my canopy for the steam exhaust. This keeps it away from the boiler chimney and its burner at the bottom. Mike

 

[Fred2179G]

My Brunel came with the pipe and it does keep the crud from spraying everywhere. It is just a push fit in the side of the cylinder block. Not very smart of Mamod to stop including them.

I don't think you have to make yours watertight or any kind of tight - it just needs to stay in the right place while your engine is bouncing along the track. Look at bolting the bottom of it to the chassis so the top fits in the hole in the cylinder block, loosely? Wrap the top of your pipe in some heat-resistant (e.g. PTFE) tape so it stays where you want it.
Another option to explore is tin the end of the copper pipe where you threaded it with soft solder, and gently screw it into the cylinder block - let the solder take the threads already in the hole.

The more I think about it, the more I like the idea of clamping/bolting the bottom of the pipe to the frame/chassis so the pipe is held where you want it. Set it in the cylinder block with tape or solder and then tie it down.

Here's a 9 sec video of my Brunel making steam with the pipe.

Finally, if you want to go further, a "spittoon' is a desirable thing to have. As described by others above, a box with the exhaust entering it at the top, a drain hole for the water/oil to continuously dribble out onto the track, and another pipe out of the top for exhaust steam. The Regner Chaloner has exactly this 'condensate' box from the factory. I made one for my Regner Otto using a 1/2" copper pipe cap.

 

[Thornhill]

Thanks for all the advice and ideas - very helpful. I hope to get a Clevedon condenser as a result or make a simple one of my own. Luckily, and thanks to the brilliant help of a skilled model engineer friend, I have got a short threaded brass tube to fit into the exhaust port. It was difficult as there are only three threads to play with and the port is a very bad 4BA fit - in fact slightly bigger than 4BA and tapering to boot. My friend was miraculously able to machine the part to fit. I now have a centimetre brass exhaust nozzle sticking out that I can fit a silicon tube to. This can then be connected to metal exhaust pipe, up or down, or to a condenser. I hope to do the latter.
Thanks again for helpful replies. It's just a shame that Mamod have this poor and annoying port design on what is otherwise a solid and nice loco.

 

[Paul M]

That's very odd, my exhaust pipe is just a push fit. In fact it's quite a loose fit, so I've made a clamp for it. What is really required is a proper steam oil reservoir

 

[RMurphy195]

Hi there - I am in exactly the same position as Thornhill, but with much less knowledge/skills in this area (The Brunel is my first steam engine of any kind) but have noticed te likely problems with gunge. In my case, apart from the looks (the model will take pride of place on my mantelshelf when not in use) I intend that my grandchildren might be able to put small toy figures into wagons that the loco will pull, so a bit of cleanliness would be appreciated!

I'm very interested in a couple of aspects of the above replies, esp the push-fit pipe as supplied to earlier versions, so would appreciate any extra detail that contributers might give, such as the pipe diameter (the threaded hole looks to be about 3.4 - 4mm diameter) and the material - e.g. maybe a bit of silicon tube might do the trick?

Any advice for this raw beginner would be much appreciated, thanks.

PS I've just converted 3.5 mm to fraction and come up with 1/8", if that helps anyone (haven't a clue what 4ba is)

 

[Fred2179G]

the push-fit pipe as supplied to earlier versions

The pipe that came with mine is 3.1mm, approx 1/8th. 4BA is a british size - BA is the British Association and is described in a Wikipedia article as 'obsolete'. 4BA is 3.6mm outside diameter.
British Association screw threads - Wikipedia
As mine hasn't fallen out yet but seems quite loose, I suspect there may be an O-ring or something in the hole that the pipe pushed in to. I don't know that silicon would be my choice of exhaust pipe - I'd try 1/8th copper tube and see if you can persuade it to stay in with some kind of hi-temp glue. Mine sticks down to below the floor - see the photo on my video above.

 

[Paul M]

The pipe that came with mine is 3.1mm, approx 1/8th. 4BA is a british size - BA is the British Association and is described in a Wikipedia article as 'obsolete'. 4BA is 3.6mm outside diameter.
British Association screw threads - Wikipedia
As mine hasn't fallen out yet but seems quite loose, I suspect there may be an O-ring or something in the hole that the pipe pushed in to. I don't know that silicon would be my choice of exhaust pipe - I'd try 1/8th copper tube and see if you can persuade it to stay in with some kind of hi-temp glue. Mine sticks down to below the floor - see the photo on my video above.

My exhaust pipe is just a push fit, I've made a bracket to hold it in place. I really ought to get round to doing a better job of it, mine always suffers with lack of steam oil

 

[JimmyB]

The pipe that came with mine is 3.1mm, approx 1/8th. 4BA is a british size - BA is the British Association and is described in a Wikipedia article as 'obsolete'. 4BA is 3.6mm outside diameter.
British Association screw threads - Wikipedia

I hope note I still have a draw full of BA nuts and bolts (actually machine screws)

 

[RMurphy195]

Thanks for the replies folks. I think my way forward is to try a 1/8" screw-in insert of some sort (lots around on supplier websites) then if that works connect something to that, or if not try a bit of 1/8" copper pipe - which would be my preferred route either way unless I fit a catchment tank for the goo at some point! (I quite fancy a bit of polished copper)

 

[Fred2179G]

mine always suffers with lack of steam oil

I don't see what the exhaust pipe has to do with lack of steam oil - it's a way downstream. Usually it's the hole in the lubricatior pipe that isn't letting enough oil in with the steam.

 

[PhilP]

Does Paul perhaps mean that the loco uses an excessive amount of steam oil?

(Not that I know much about 'little dragons')

 

[Fred2179G]

Does Paul perhaps mean that the loco uses an excessive amount of steam oil?

Usually, lack of steam oil means there is more left in the lubricator than one expects - so not enough is getting to lubricate the cylinders; hence they are lacking lubrication. We will see what he thinks it means . .

 

[Paul M]

What I mean is the engine hasn't got a decent steam oil system. Usually the steam oil is delivered to the pistons through a small hole in the steam pipe. On my Brunel, the steam pipe stops at the reservoir and pushes the oil ahead of into the piston. Thus most of the oil is used in the first minutes of operation. As I said I must sort out a better method

 

[Fred2179G]

On my Brunel, the steam pipe stops at the reservoir and pushes the oil ahead of into the piston. Thus most of the oil is used in the first minutes of operation

I think you have a defective engine. My oiler has the pipe running through the oiler to the cylinder block with a small hole on top to pick up the emulsified oil.