Removeable firebars - how neccessary are they?

[springcrocus]

I think I may have asked the wrong question in the Britannia diary, here's why.

While I was at the club last Saturday I mentioned about making the ashpan and one of the members remarked that he had changed to a rosebud grate because he kept burning out the firebars in his loco. Others then mentioned being able to remove firebars through the firehole.

The 5" Britannia grate is designed as a single assembly and can only be removed by lifting the boiler. The ashpan cannot drop down because of the pony frame and the grate assembly is bolted to the inside of the ashpan.



If I make everything to drawing, and using stainless steel throughout for the grate assembly, what are member's opinions about the likelyhood of burning through the bars, requiring replacement? Is it worth trying to design a means of making the grate assembly removeable bearing in mind all the pipework either side of the ashpan?

People's thoughts on this would be very welcome.

Regards, Steve

[Cro]

Steve,

I think if you are using the standard off the shelf stainless firebars and working the engine hard and often then you may get one or two. If you are fabricating it (haven’t looked closely at your drawing for dimensions) I would imagine it’s thicker than standard stuff so less likely. I’ve never seen one go, hardly seen any come close.

If you want to be fail safe then made it as it shows in the drawing but in 3 sections that lift out through the door. My 9f has two fixed either side and one in middle that comes out and just locates on one of 3 cross bars. Bit of an art getting them in and out but you’ll get the hang of it!

Adam

[pault]

I would make them so you can get them out, pretty much any material will give up with many years of hard use, and some with not so many years. A lot will depend on how the ashpan deals with the ash. On some locos the ash can build up to the bottom of the bars causing localised overheating of the bars. It can also make dealing with clinker much easier.

[oldnorton]

Steve,

Like you I went through the thought process of what was best.

I have made my own grate in three longitudinal pieces and each can be (fairly easily) hooked out with a custom tool through the firehole. I used substantial SS bar of 12mm x 3mm section and TIG welded the parts; you could have a bolted up design but that increases the dimensions fractionally and the firehole clearance is marginal. The three grate sections rest on two support cross bars that mount on legs rising from the insides of the ashpan.

The centre grate has a drop door directly over the centre ashpan door and a lifting crank with cross rod through the ashpan. That centre grate also has a hooked piece in the front to physically hold it down onto the front support. The idea is that 90% of the time I can drop the fire through the grate door and ashpan door. But when the inevitable blockage occurs the grate can be hauled out through the firedoor. I know of a famous builder who made a 'rocking grate' and on first steaming it all jammed with ash pieces. The engine is still waiting for the boiler to be removed to allow the grate to be replaced.

I have made an ashpan in SS that largely follows the Perrier/Prototype outline and has three drop doors at the front operated by lever, cross rod and cranks. The centre door will drop fully through the pony truck frame opening but the outside pair only drop 45deg before they strike the pony truck. This is how it has to be and I don't see it as a problem, as long as the doors don't accidentally drop while the locomotive is in motion!

I have also made a proper steel support ring that the ashpan sits in and this is firmly mounted on the main rear loco frames to properly support the weight of the firebox and boiler. The lack of support in the Perrier design seems a very weak point to me. It all comes from the fact that the prototype has a massive boiler support just in front of the firebox and the firebox hangs in the air. The ashpan is then held on pins coming from the foundation ring. The models don't attempt that - they have odd bits of metal trying to hold the ashpan up and the main boiler support is mis-fitted or forgotten. The odd bits of metal then become the entire boiler support system. In my design the boiler expansion is allowed for by the foundation ring sliding on the top flange of the ashpan which sits on the steel support ring.

Norm

[lankyyorky]

Dec 24, 2019 7:58:10 GMT springcrocus said:

I think I may have asked the wrong question in the Britannia diary, here's why.

While I was at the club last Saturday I mentioned about making the ashpan and one of the members remarked that he had changed to a rosebud grate because he kept burning out the firebars in his loco. Others then mentioned being able to remove firebars through the firehole.

The 5" Britannia grate is designed as a single assembly and can only be removed by lifting the boiler. The ashpan cannot drop down because of the pony frame and the grate assembly is bolted to the inside of the ashpan.



If I make everything to drawing, and using stainless steel throughout for the grate assembly, what are member's opinions about the likelyhood of burning through the bars, requiring replacement? Is it worth trying to design a means of making the grate assembly removeable bearing in mind all the pipework either side of the ashpan?

People's thoughts on this would be very welcome.

Regards, Steve

[lankyyorky]

On ex LMS narrow firebox locos the firebars were in three sections from front to rear, at Holbeck (and other ex Midland sheds I believe) the usual practice when cleaning the fire was to save a portion of clean fire under the door, rake all the rest down to the front then remove several firebars from the middle section with a (very) large pair of tongs and push the old fire through the hole, the ashpan would also be raked out without going underneath.

The bars were then jiggled back into place with a bar hook and the fire made up.

The point I am making is would it be better, at least in the larger scales, to have individual firebars located in notched transverse supports rather than welded up units?

Rocker grates on BR standards were a godsend until they jammed.

[Andrew C]

Hi Steve
The Britannia I have has a grate with a center section that can be dropped/rocked.

Let me try and describe the bars and how they are connected.

the rear rod goes through all the bars. The front is made of three separate rods, a center and two outer ones, the number of bars evenly spread over the three. the two outer section of the grate are fixed in place the center is held in place by a pin that goes through the sides of the ash pan. Pulling this out allows the center to drop and allows the fire to be scraped out into the ash pan.

modeleng.proboards.com/attachment/download/2151

If this link has worked then you can see the pointy end of the pin just behind the injector.

If not it is modeleng.proboards.com/thread/5704/cosmetic-finishing-touches?page=3

If you read old copies of M.E. LBSC and Martin Evans seem to advocate fully removable grates. so you can get them out in a hurry if things go wrong.

In the last 40 Years of steaming 5" locos I have had 2 gauge glasses break and one clack fail to seat. Each time this has happened by the time I have been in a position to pull the pin, the blower has been turned off, the regulator closed, the injector(s) on full plus the smokebox and firehole doors open the fire has been hardly worth the effort.

[Jim]

I decided the ash pan and grate looked complicated and so a cause of potential problems. With that in mind I modified the ashpan to a simple shute with a flap at the bottom that lets the ash out through the gap in the pony truck. The grate is a rosebud style plate that slides out to the side.

This is a mock up of the ash pan, in the final version I added air holes at the front.

This shows the grate in postion:

and finally partly removed:

This is just my approach to what I saw as a problem. Lurking in the back of my mind is plan B in case the Rosebud doesn't work as planned with the new fuels being used in which case I'll make a more conventional slide out bar grate.

Jim

[springcrocus]

Thanks to all who have replied so far. It appears that the general consensus is that it's worth making the grate removeable and I'm now inclined to try and devise something along these lines. If seven or eight members suddenly say it's not worth the effort than I shall reconsider. Either way, nothing will happen until the spring so plenty of time for people to add their two-pennorth if they feel inclined.

Now it's definitely off to the loft, the workshop is locked!

Regards, Steve

[Jim]

Enjoy the 'O'gauge in the loft and do as you will, and that is to decide on a solution to the grate issue that you feel comfortable with.

Have a great Christmas.

Jim

[steamer5]

Hi Steve,
I'd go with removable, made from stainless, unless you decide to follow Jim. the grate in my loco is the original, so now over 40 years old (admittedly its not been steamed week in & week out). I think I posted a picture of my grate...could be wrong....when I get home, given that's its Xmas day here its likely to be tomorrow I can post a picture.....the loco is Nigel Gresley & the grate is in 3 sections front to back & hinged together if that make sense. The are removed via a section of foot plate which lifts out & the grate is then pulled out. Dads loco has a 3 piece grate which is removable via the fire hole. He has made tools to help get them in & out.
Having tried to dig a fire out of the fire box via the fire door a removable grate makes it WAY easier. Nigel's ash pan has a drop down flap to dump the ash etc...but it doesn't fully open the rear axel is in the way so big lumps of coal are an issue!
Hope some of that is useful

Merry Xmas to you & your family!

Cheers Kerrin

[uuu]

I had always wondered why Ken Swan's Jessie design had a big hole in the frames, that's half covered up by the rear sandbox. Now I realise that it gives access to the rear ashpan fixing, so this (and the grate) can be removed with the boiler in place. Genius.

Merry Christmas

Wilf

[delaplume]

Hello all........Here are some more reasons in favour having a removable grate}----

a) The need for a Boiler Inspector / Operator to be able to view the crown of the boiler, ( Especially with those Rosebuds )..

b) Provide access to inspect / repair stays on the side sheets, plus fore and aft sheets..and all silver soldered joints..

c) Provide access to change any fusible plugs that may be fitted.

d) Provide access to view any water tubes within a combustion chamber


Remember that pre-assembled Stainless Steel firebar units make use of prototypical taper section bars------this is done to prevent lumps of coal or clinker becoming jammed between the bars.....

Ideally the grate assembly should fit up into the space that the foundation ring creates, ( ie----the bottom of the grate is flush with the bottom of the Foundation Ring )..thus preventing air from being drawn over the top of the burning coal and creating localised "Hot-Spots" at the edges of the foundation ring... Have a look at Steves drawing which clearly shows this feature..

[delaplume]

Dec 24, 2019 8:12:51 GMT Cro said:

Steve,

I think if you are using the standard off the shelf stainless firebars and working the engine hard and often then you may get one or two. If you are fabricating it (haven’t looked closely at your drawing for dimensions) I would imagine it’s thicker than standard stuff so less likely. I’ve never seen one go, hardly seen any come close.

If you want to be fail safe then made it as it shows in the drawing but in 3 sections that lift out through the door. My 9f has two fixed either side and one in middle that comes out and just locates on one of 3 cross bars. Bit of an art getting them in and out but you’ll get the hang of it!

Adam

Yes, that's the way I would suggest as well.......after all that's how full size grates are fitted and in the case of the model we have an oval hole which will be of great help ( I can't believe I just typed that !! ).......and it's why I opted for the same on my Bear..

One other thing to consider}---- The drawings are quite old and show the "Do it yourself" type of firegrate assembly made from  bars of parallel steel drilled and  held apart by spacers with long bolts clamping them all together......Do be aware that these types are prone to warping and can be quite awkward to replace after withdrawal and being cooled

[Jim]

Dec 25, 2019 23:37:38 GMT delaplume said:

snippeda) The need for a Boiler Inspector / Operator to be able to view the crown of the boiler, ( Especially with those Rosebuds )..

snipped

I can't quite see what the problem is with a Rosebud grate Alan.

It slides out sideways leaving a clear view up into the fire box depending on the model of course. In the case of a pacific such as the Britannia you do have the pony truck partly restricting the view. Personally I'd use one of those large style dentist's style mirrors inserted through the fire hole door to view the crown of the fire box, which is what I've done when needed.

Jim

[springcrocus]

Alan's reply seems sensible but some items miss the point a little. Having removeable bars is about changing damaged ones without lifting the boiler. Any other repairs to the boiler would entail separating it from the mainframes anyway, so are of no consequense.

Nowadays, inspection is probably best done with an endoscope-style camera, which everyone can get from the likes of Aldi and Lidl for under £40, through the firehole. I've had one for years, great for seeing cables in building cavities.

The firehole on this britannia is just about large enough to accomodate a 2" x 1/2" section so four sections of firegrate would be required to make this work. This will mean two side sections and two centre sections and I would like to retain the drop-down feature, so some designing needed here, not normally my strong point. Should be fun.

Alternatively, Jim's grate is suddenly looking attractive again.

Regards, Steve

[Jim]

I'm sure you'll sort something out Steve that will work for you and that you're satisfied with.

I'm still experimenting with my rosebud grate in terms of volume and distribution of air through the grate. Out here they are fairly common and work well but subject to tweeking.

Jim

[delaplume]

Hello Jim,

Quote}--"I can't quite see what the problem is with a Rosebud grate Alan."......all I meant was that by it's very design a Rosebud grate is almost a solid piece of steel with small holes in.......thus virtually blocking any chance of a direct view up towards the crown, unlike the better view afforded by firebars...

Looking at your photo with the Rosebud being removed sideways then of course that negates my original comment, and nicely too !!

Hello Steve,

Having removeable firebars with our models I would say is more to do with dumping the fire when disposing at the end of the running day.......The last thing you want to be doing is digging it out, either in scale or full-size, especially if heavily clinkered.....In over 40 years actively involved with both types I know what I don't want to be doing when it's time to Book-off--- that's for sure !!

Also, depending on actual size, if you can't design-in a removable grate then a simple rocking type will at least help dump that dying fire...

[andyhigham]

The Martin Evans "Conway" has a problem when dropping the fire. The ashpan and grate are wider than the rails so the only way to remove them is to back the loco off the end of the steaming bay (twitchy bum time).
I saw a "Britannia" that had a QD rear truck so after backing the tender off and pulling the truck out the grate could be dropped, IIRC it was in 3 pieces

[delaplume]

Hi Andy,

Quote}--"I saw a "Britannia" that had a QD rear truck so after backing the tender off and pulling the truck out the grate could be dropped, IIRC it was in 3 pieces"

That's exactly how I have designed The Bear's ashpan & grate .... At the moment it's only a set of drawings....I'd love to actually see a working set-up......

There is a chap in the Wolverhampton MES who runs an American 4-4-2 and I've seen his rear truck being removed in the same way......Have a look at this, it's the maroon loco on the left of the photo---------> www.wolverhampton-dmes.co.uk/ If anybody knows who he is can you give me a contact No or E-Mail address please ???....I'd love to have a chat and take photos etc...Many thanks

Alan