Roundhouse Garratt

[dewintondave]

A quick calculation suggests that a standard Roundhouse boiler would be able to steam four 10mm x 15mm cylinders (3/8" x 5/8" for the non-metricated).

Excellent work Graeme.

With my project, I calculated that my loco would use twice as much steam as a Roundhouse due to the gearing and cylinder size. The boiler is 3" dia by 6' long with two 3/4" burner flues and only one internal 3/4" uptake.



Best wishes,
Dave.

[Big Jim]

The problem I can see is that If you reduce the size of the cylinders then the power that they can provide is reduced as well. So you may be able to run four cylinders from the standard boiler but you would end up with quite a low powered set up.

Lets face it a big impressive bestie with a very limited haulage capability is going to be a bit of a disappointment.

Good luck with the project though.

[funandtrains]

I was wondering if rather than trying to design big boiler from scratch and hope that it steams well why not consider using a proven small 3 1/2 inch gauge loco boiler design such as a Titch or Rob Roy. There are boiler kits available or you can buy them ready made from a model boiler maker. You would also get the choice of using coal, meths or a ceramic burner to fire it. A small squat tank loco boiler in 3 1/2 gauge is about the same size a Garratt boiler in 16mm.

[TommyDodd]

why not consider using a proven small 3 1/2 inch gauge loco boiler design such as a Titch or Rob Roy.

I believe John Campbell used the small tich design (LBSC produced 2 boiler options, as well as Walschaerts or slip-eccentric valve gear options) in his first coalfired engines (freelance rigid tender engine and a freelance garratt).

[ace]

With my project, I calculated that my loco would use twice as much steam as a Roundhouse due to the gearing and cylinder size.  The boiler is 3" dia by 6' long with two 3/4" burner flues and only one internal 3/4" uptake.

That boiler looks promising, can I ask why you have the internal uptake tube? I thought the air came in the back of the burner and out the front into the smokebox?

I have to say, this project I am going to keep an eye on.

I was wondering if rather than trying to design big boiler from scratch and hope that it steams well why not consider using a proven small 3 1/2 inch gauge loco boiler design such as a Titch or Rob Roy. There are boiler kits available or you can buy them ready made from a model boiler maker. You would also get the choice of using coal, meths or a ceramic burner to fire it. A small squat tank loco boiler in 3 1/2 gauge is about the same size a Garratt boiler in 16mm.

Where would you get a kit like this?

[funandtrains]

With my project, I calculated that my loco would use twice as much steam as a Roundhouse due to the gearing and cylinder size.  The boiler is 3" dia by 6' long with two 3/4" burner flues and only one internal 3/4" uptake.

That boiler looks promising, can I ask why you have the internal uptake tube? I thought the air came in the back of the burner and out the front into the smokebox?

I have to say, this project I am going to keep an eye on.

I was wondering if rather than trying to design big boiler from scratch and hope that it steams well why not consider using a proven small 3 1/2 inch gauge loco boiler design such as a Titch or Rob Roy. There are boiler kits available or you can buy them ready made from a model boiler maker. You would also get the choice of using coal, meths or a ceramic burner to fire it. A small squat tank loco boiler in 3 1/2 gauge is about the same size a Garratt boiler in 16mm.

Where would you get a kit like this?

The model engineering supply companies sell kits, I'm at work so don't have the links to hand and their name shave slipped my mind. If you search for live steam, 2 1/2 inch and 3 1/2 inch gauge you will find several suppliers.
When you get to a loco of this size it is worth considering that it is comparable in size to many larger gauge locos and more appropriate parts will be available from suppliers that specialise in these. The 16mm world can be a bit self contained with most suppliers only catering for 32mm and 45mm gauges where there are a whole load of other live steam modellers out there for larger gauges, model boats, traction engines, etc. You may find a boat or traction engine boiler may also be a fit.

[funandtrains]

If you can get to London the Modell Engineering Exhibition this month should have many of the suppliers their.

Several suppliers sell drawings and parts for the popular LBSC and other popular starter locos in the smaller gauges.

[GTB]

So you may be able to run four cylinders from the standard boiler but you would end up with quite a low powered set up.

That was the point I was trying to make. The power output of a steam loco. depends on the ability of the boiler to convert water into steam.

However, not all Garratts were earth shakers. There were also dinky little ones, such as the Mayumbe line in the Congo and the Buthidaung-Maungdaw line in Burma.

These mini-Garratts were only about the power of an L&B Manning-Wardle in real life, so a SM32 model could easily be built around a Roundhouse boiler and four small cylinders.....

Graeme

[GTB]

I was wondering if rather than trying to design big boiler from scratch and hope that it steams well why not consider using a proven small 3 1/2 inch gauge loco boiler design such as a Titch or Rob Roy.

There is plenty of information around for designing boilers from scratch and existing designs are easy enough to modify if you stick to the rules.

Except for Tich, most 3 1/2" gauge boilers would be physically too large for SM32/45 locos., but some 2 1/2" gauge boilers would be in the right size range. You would still have to run through the calculations to check the boiler would steam the size of cylinders you wished to use.

As it happens I had a look at the small Tich boiler drawings a while back to see if it was useable in this scale. It was an academic exercise, as I've no interest in coal firing in this scale.

The small Tich boiler has the capacity to easily steam four Roundhouse cylinders, if you wanted to build a coal fired Garratt about the size of K1 using a couple of Roundhouse Katie chassis. It's the right diameter, but actually a bit shorter than scale for K1, but that's not a major problem. The fire tubes are of a size that would still steam OK if the boiler was made 1 1/4" longer. The firebox may also need to be made a bit shallower so the ashpan will clear the rails.

Graeme

[GTB]

With my project, I calculated that my loco would use twice as much steam as a Roundhouse due to the gearing and cylinder size.  The boiler is 3" dia by 6' long with two 3/4" burner flues and only one internal 3/4" uptake.

Great minds think alike......

What burner design are you using? The cab photo looks like they are your own build.

Graeme

[steamyjim]

As it happens I had a look at the small Tich boiler drawings a while back to see if it was useable in this scale. It was an academic exercise, as I've no interest in coal firing in this scale.

The small Tich boiler has the capacity to easily steam four Roundhouse cylinders, if you wanted to build a coal fired Garratt about the size of K1 using a couple of Roundhouse Katie chassis. It's the right diameter, but actually a bit shorter than scale for K1, but that's not a major problem. The fire tubes are of a size that would still steam OK if the boiler was made 1 1/4" longer. The firebox may also need to be made a bit shallower so the ashpan will clear the rails.

Graeme

Just out of interest, would the large Titch boiler be more suitable? I don't have my Titch drawings to hand, so I don't know if LBSC changed the diameter or length of the boiler when altering the design.

What about the Juliet boiler? That's a similar sized loco if I recall correctly

[laurence703]

The Juliet boiler is twice the size of a titch boiler... I know... I've had a working Juliet...

[DLRdan]

Just for reference, this is a Robroy boiler, pretty much the same size as a Juliet.

[ace]

That may be a little large....

Second thoughts though, you could build a 7/8ths garrett?

[laurence703]

Its not far off a NGG16 boiler but its still rather big...

[ace]

A quick calculation suggests that a standard Roundhouse boiler would be able to steam four 10mm x 15mm cylinders (3/8" x 5/8" for the non-metricated).

Excellent work Graeme.

With my project, I calculated that my loco would use twice as much steam as a Roundhouse due to the gearing and cylinder size.  The boiler is 3" dia by 6' long with two 3/4" burner flues and only one internal 3/4" uptake.



Best wishes,
Dave.

What is wrong with the boiler on the previous page? That looks great! I still would like to know what the internal uptake is for?

[DLRdan]

Its the exhaust from the burners, the two horrizontal tubes have the ends blocked.

[ace]

Its the exhaust from the burners, the two horrizontal tubes have the ends blocked.

Oh, I thought the burners could exhaust into the smokebox? I suppose it is slightly more efficient this way.

[MDLR]

I suspect that the boiler gos right to the front of the smokebox.

[ace]

I suspect that the boiler gos right to the front of the smokebox.

So where does the exhaust from the cylinders go? I think I'd prefer to have a open smoke box and no uptake if it were mine.

Either way, its a great boiler, I'd just like to understand it a little more.