Clinker and tube blockages

[JonL]

I turn down the blower when running but leave it cracked as I'm using anthracite and was advised that would be the best bet.

I'm intrigued about the brick arch, I didn't even think it was possible in a firebox as small as a 3.5" William. How would you go about it?

[barlowworks]

My colleague has one welded to the front of the grate on his polly and says it has helped the steaming no end. I works because the grate drops out underneath. Unfortunately it won’t work on my Britannia because I would love to give it a go.

Mike

[JonL]

I guess I could use some stainless steel sheet rivetted to the front edge of the grate and bent to clear the foundation ring....

[Gary L]

May 20, 2021 4:09:24 GMT JonL said:

I guess I could use some stainless steel sheet rivetted to the front edge of the grate and bent to clear the foundation ring....

It doesn’t hurt to try something if it is easily unscrambled. Personally, I’ve found the results disappointing (read unnoticeable) and concluded Julian was right when he said that scale effects mean that unlike full-size, the bulk of the heat transfer in a model firebox is by radiation not convection, thus the ‘brick’ arch does as much harm as good. We’d be interested in your results, especially if they were measurable, difficult though that might be.

Fixing the arch to a removable grate is a very good idea though, especially for testing, because one of the disadvantages of a fixed arch is it collects char and makes tube cleaning a bit more difficult.

Gary

[uuu]

A glass arch seems to be the answer, then.

Wilf

[ejparrott]

May 19, 2021 20:36:35 GMT JonL said:

I turn down the blower when running but leave it cracked as I'm using anthracite and was advised that would be the best bet.

I'm intrigued about the brick arch, I didn't even think it was possible in a firebox as small as a 3.5" William. How would you go about it?

Anthracite does require a constant draft, but when running the loco should provide the necessary, you shouldn't need the blower as well. Kind of suggests the front end isnt what it should be.

An arch can be tested by securing to the font of the grate as suggested

[coniston]

I fitted an arch to my Speedy which had a most vicious draft in an attempt to reduce the coal being drawn off the top into the tubes. Didn't see any real benefit and just made inserting the grate more difficult. I also made a removable one for my B1 but again didn't see any real benefit and being only held by gravity it had a nasty habit of being dislodged by a misplace shovel or poker then dropping onto the fire so then had to drop the grate to remove it.

In all honesty as others have said drafting is where I would look for improvements which includes grate and ash pan as much as the smokebox end. Maybe a grate with wider spacing and fewer bars? more air and lets the ash fall through easier.

Keep improving and you'll end up with a really nice little loco.

Chris D

[JonL]

Thank you, to be honest I think the arch may be more trouble than its worth in the firebox I have. I'll double check the sealing of the smokebox today, and when I run it tomorrow I'll do a midday grate drop and poke through of the lower tubes. At least I'm getting a better idea of the issues. Other than that she runs really well now.

[smallbrother]

May 21, 2021 5:28:10 GMT JonL said:

Thank you, to be honest I think the arch may be more trouble than its worth in the firebox I have. I'll double check the sealing of the smokebox today, and when I run it tomorrow I'll do a midday grate drop and poke through of the lower tubes. At least I'm getting a better idea of the issues. Other than that she runs really well now.

Don't forget to clean out the smokebox too!

Pete.

[dhamblin]

I was doing a bit of research to replace Britannia's petticoat pipe after finding it too damaged under a layer of soot. There are some good posts on here from Julian about optimising the blast and petticoat pipe design that I think would be worth looking at.

Looking at machining mine out of solid brass as per Keith Appleton's YouTube videos.

Regards,

Dan

[andyhigham]

If you open the smokebox you can clean all the ash out and poke the tubes with a piece of dowel or similar without dropping the fire

[gingerneer]

Nobbysideways an arch can be hung from the super heater if they poke in to the fire box, but like a rose bud grate, its not necessarily the answer, although it might help steaming.

How big is the coal? too bigger lumps can not cover the grate completely, leaving gaps for cold air, so running with smaller coal might help, what is the spacing of the grate bars?

It sounds like there is some under lying issue. Is the smoke box sealed? I have used Heatmate high temp silicone seal to seal all the holes from the pipe work and smear on the barrel to smoke box joint.
Are they any pipe holes or leaks on the steam pipes/wetheader? A good way to check is with the engine running on air using soapy water to see any leaks.
Is the blast pipe out of alignment? Even a slight knock to one side will affect how the exhaust steam fills the chimney. A long good fitting rod in the blast pipe with show how it aligns with the chimney.
Is the blower alingment? Pump the boiler full of water, then with 30 psi of water pressuer open the blower valve, you are looking for the jet of water to be central in the chimney.
What is the front end set up like? Is the chinmey tapered? No doubt that it can be improved, but how much depends on how much you want to alter. But a taper liner and a 3 or 4 jet blast nozzle, if correctly portioned should be a big improvement, not to need the blower and reduce the carry over from the fire. I have found any changes i made to my locos are well worth the effort spent.
A good book for exhausts is The Fire burns much brighter By Jos Koopermans. Julian also has also been a great help to me when i was struggling with the exhaust on Tich.

Will

[JonL]

The smokebox was sealed with an aircraft grade RTV sealant during construction, it seems pretty well together. I aligned the blast pipe and blower as well and they don't appear to have shifted. When the blower is first opened up the jet of water seems pretty well centralised. The superheaters are not radiant so I don't have any where to hang anything, but I think the main reason I've chosen to discount the brick arch in this case is that I think it will get blocked very easily on this firebox. My grate is very small indeed with not much space above it.



I have wondered about making a better blower, I made a 4 jet one for the Britannia and was quite pleased with it. Maybe I can do some experiments with the blast pipe at the same time

[stevep]

At the risk of stating the obvious, if you are getting ash and char sucked into your firetubes, you are not suffering from a lack of draught - indeed, it may even be too much.

If you need to have the blower on to keep your fire lively, then I think you need to look elsewhere for the reason for the blockages.

Obviously, building the fire too high can be a cause. When I am near to finishing a run with my Rob Roy, I stop feeding the fire, and I am always surprised how long it takes for the fire to die down while still running, and it is often at it brightest. I just can't seem to remember not to put so much coal on.

Bigger lumps of coal will not block the tubes so easily, but as another poster mentioned, can leave gaps in your fire bed. Small lumps prevent this happening, but are lighter and more able to be sucked into the tubes.

I think too much coal in the firebox may be the most likely reason, and I would try running with a much shallower fire. Just remember to ensure it is well established before you move off initially, as if you still have wood and/or charcoal in there, the fire will die quickly.

[JonL]

I think you are probably right, I'll run with less blower and see how we go, and also run the fire lower.