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Firing a 1" Minnie

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Paul Lousick15/12/2021 01:31:20
2019 forum posts
712 photos

A member of our club (full size steam engines) has purchased a 1" Minnie traction engine and had trouble raising steam . (The previous owner had only run it on air). We tried a number of different types of wood, pine, old hardwood, BBQ fire lighter tabs, soaked wood in kerosene (parafin) but the fire kept going out.

Tried elevating the front wheels and extended the chimney to get a better draft. He did not have a blower to create a forced draft, which could solve his problem.

Does anyone have any experience with fireing a minniature traction engine ?

1in minnie 1.jpg

Jon Lawes15/12/2021 06:17:01
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895 forum posts

Certainly until the fire is established I need an external (electric in my case) blower on my 3.5" locomotive, which obviously has a larger boiler. Usually I need the steam blower to some extent to keep the fire in when stationary, probably because I'm using anthracite.

I usually start on a single cube of a firelighter, light that and throw it in, poke in some bbq charcoal, get that going on the blower, then once I'm onto the steam blower I switch to coal. If it makes a difference I usually have 2/3 of the gauge glass full of water, which in the case of my locomotive is as much as I can get away with without priming once pressure is up. The process takes about 20 minutes I think off the top of my head.

Paul Lousick15/12/2021 06:43:07
2019 forum posts
712 photos

Thanks Jon.

I have no problem with full size traction engines and my 6" Ruston Proctor. I can fire it with kindling only but normally use an electric blower and have steam in about 40 minutes.

I have been told that it is a good idea to fill the boiler with hot water but I think that an electric blower is a must have.

Cheers, Paul;

JasonB15/12/2021 07:24:21
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I know of a couple of people who run them on charcoal, first soaked in paraffin then as you get a good hot bed ease off on the paraffin. But they do need almost constant attention and filling with hot water will also help

Ady115/12/2021 11:02:25
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5071 forum posts
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On the subject of blowers those Lidl pumps also have an airbed attachment which has a decent fan blower or sucker

The advertising all focuses on the bike pump bit but the blower blasts out a very impressive slug of air

I took the compressor part to bits and lubed it up to extend its life, the internal compressor build is pretty weedy to maximise its efficiency

Edited By Ady1 on 15/12/2021 11:15:58

Dave Halford15/12/2021 16:16:00
2015 forum posts
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The smaller you get the bigger the pain they are.

The Minnie boiler mounted water pump probably won't work when it gets hot.

Small air leaks around the smokebox have a big effect, as does the blast nozzle location,

Sometimes they work on air but won't work on steam. If it's not been fired before it sounds like a steam test was not undertaken so don't trust the safeties when you do fire it.

Paul Lousick15/12/2021 21:13:20
2019 forum posts
712 photos

A better name should be a "steam raising sucker" because the fan is normally fitted to the top of the chimney and draws the air from the fire and up the chimney. A Lidl type pump made of plastic and will melt from the hot gasses.

An injector will not work when it gets hot but a mechanical pump should be OK. The full size Marshall portable engines at our club and this Roby all have water pumps attached to the side of the boiler.

robey 4.jpg

Ady115/12/2021 23:22:26
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5071 forum posts
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Yes I think a plastic air blower might work more reliably from the cold end

Like a bellows on a blast furnace

Edited By Ady1 on 15/12/2021 23:26:26

duncan webster15/12/2021 23:41:51
3946 forum posts
63 photos

Blowing air into the Ash pan will make flames come out of the fire hole door. Black gates used to sell steam raising fans

noel shelley16/12/2021 10:21:41
1298 forum posts
21 photos

A 12v car heater blower can sometimes be adapted, provided the fan or impellor is not plastic, or if compressed air is available then an extended chimney with a small bore pipe let into the side pointing up will act as a blower. The idea is to PULL the fire up not blow it from below. Such a small coal fire will require constant attention. Noel.

Jon Lawes16/12/2021 10:38:43
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895 forum posts

As Noel says, an arrangement like the bypass air on a modern jet engine can be used, one tube inside another (with the air being fed to the outside ring to drag the fire gases up through the centre).

Dave Halford16/12/2021 10:43:01
2015 forum posts
23 photos
Posted by noel shelley on 16/12/2021 10:21:41:

A 12v car heater blower can sometimes be adapted, provided the fan or impellor is not plastic, or if compressed air is available then an extended chimney with a small bore pipe let into the side pointing up will act as a blower. The idea is to PULL the fire up not blow it from below. Such a small coal fire will require constant attention. Noel.

Which is how Ady's little would actually work, though I'm sure Paul will already have worked that out.

Nigel Graham 207/03/2022 19:37:15
2056 forum posts
28 photos

Although owners of the larger 3-inch scale and bigger miniatures can emulate full-size practice by using a long extension-chimney and natural draught, it is not very likely to succeed on an engine of 'Minnie' size.

I must admit I've not heard of using hot water first off, but that will only accelerate steam-raising a bit once the fire is burning properly. It won't help the fire to burn.

Many do use paraffin-soaked wood for firing up miniature engines. I've done so, many times, but it is messy and sooty even before adding any coal. The type of wood is not very significant, though a soft wood like pine is more absorbent of the accelerent.

Another long-established primer is charcoal soaked in meths.

Prepare such fire-starting materials well in advance - say, the day before.

'

Surprisingly, I have seen ex-computer cooling fans on suitable chimney adaptors, for direct induced-draught. Despite plastic rotors on delicate little motors, they seem fairly able to withstand such 'orrible operating conditions. The exhaust gas temperature is not as high as might be expected, at least during steam-raising, but I would not like to forecast such fans' longevity in this new career!

I have also known a freelance traction-engine whose blower pipe was fitted with a branch-pipe terminating in a connection that could be closed with a simple screwed cap. This was connected to a small compressor for steam-raising, using the engine's own blower (or 'steam-jet' as apparently more often called in TE practice). Though feasible technically, the steam-jet's valve and pipe is usually very noticeable on a traction-engine, so such a modification is poor aesthetically.

Instead, use an extension-chimney with its own air-jet as Dave suggests. Of course, the jet should be concentric and parallel to the chimney.

'

I don't know the 'Minnie' design but the feed-pump on both full-size and miniature traction-engines is usually mounted somewhere slightly away from the boiler so does not become unduly warm. Typically it's on the hornplate just aft of the backhead - near the crankshaft and accessible for servicing. Robey did put it on a bracket on the firebox side, though, on their engines.

It's really the injector that's fussy about therms so is normally low down on the bunker side, below the man-stand, to keep it cold. (Assuming no leak back through the delivery clack-valve or the steam-valve.)

Harry Wilkes07/03/2022 20:56:15
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1329 forum posts
65 photos

I once owned a 2" TE and had great difficulty getting it to steam in the end I tried a small fan which I purchased off ebay it worked a treat along with charcoal soaked in paraffin then once alight just charcoal, to keep it running as already been said needed constant attention

H

Paul Lousick07/03/2022 22:06:47
2019 forum posts
712 photos

Nigel,

A friend of mine has a home railway with 7-1/4" locos and uses old computer fans to fire the engines. They get covered in soot which has to be shaken off and they have to be replaced on a regular basis.

morgan loco.jpg

The mechanical water pump is normally driven from the crankshaft or layshaft, which on a traction engine is near the hornplates at the rear end of the boiler but on a portable steam engine, the crankshaft is at the front of the boiler as on this Marshall Britannia at our club.

marshall brittania 1.jpg

Mechanical pumps are not affected by hot water and some engines have heat exchangers that use steam to pre-heat the water before it is pumped into the boiler. Others have water tanks mounted on the side of the boiler to capture heat.

Edited By Paul Lousick on 07/03/2022 22:09:34

duncan webster08/03/2022 00:54:47
3946 forum posts
63 photos

Paul should have said pumps are much less affected by hot water, if it gets very hot you can get cavitation on the suction. I think the feed water heaters would have the heat exchanger downstream of the pump, but I'm open to correction

Paul Lousick08/03/2022 01:19:43
2019 forum posts
712 photos

You could be right Duncan. The tank locos with water storage at the side of the boiler are separated from the boiler so would not get overly hot and not have cavitation problems. My experience has been mainly with traction and portable engines and not so much with rail locomotives. The Case traction engine is fitted with a heat exchanger but I am not sure of how it is piped.

Dave Halford08/03/2022 12:23:19
2015 forum posts
23 photos

try this thread model enginering clearing house note the water pump issues

Harry Wilkes08/03/2022 16:46:09
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1329 forum posts
65 photos
Posted by Harry Wilkes on 07/03/2022 20:56:15:

I once owned a 2" TE and had great difficulty getting it to steam in the end I tried a small fan which I purchased off ebay it worked a treat along with charcoal soaked in paraffin then once alight just charcoal, to keep it running as already been said needed constant attention

H

Today talking to a friend he said that when he had his Minnie he used a cheap air pump the one used for blowing up inflatable he made a pipe to fit in the chimney to this he added a second piece of pipe at 45deg to which he could attach the air pump using this method he generated enough draft to light the engine

H

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