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Articles By Mike Rooth

Just Rambling

Well,all right,but I'm stuck for subject matter for a story. It had to happen some time,so I'm jus' nattering.
While I was building the loco,and more particularly when I started the next one,in some cases where I had used cast iron, I used Gunmetal instead.Now what irritates me is to read an otherwise well researched novel that suddenly refers to"A gunmetal grey sky" or some such.I dont mind "a gun*barrel* grey sky" but NOT gunmetal.Gunmetal is a bronze,a nice golden colour.Its full title is Admiralty Gun Metal.Its a specific mix of copper,tin and zinc that produces an alloy that machines beautifully(though I prefer cast iron),and is a very good bearing metal.The disadvantage is that as a bearing metal you have to use dissimilar metals.But then only with cast iron can you use the same metal for both bits,if you see what I mean.

The stuff was formulated originally for the casting of bronze cannon,hence the name.Of course such cannon promptly got called "brass cannon".Sods Law.The advantage of using gunmetal for a loco's cylinders,is of course,that the stuff doesnt rust.But its expensive to have cast,and means you have to use soft packing for the piston, rather than the tiny piston rings that can be bought for an iron cylinder.Plus,it is not advisable to use high degree superheat with a gunmetal assembly.The steam is just too hot,and neither the piston packing,nor the bore will stand it.

The ideal from my point of view,is if you are going to use gunmetal have either a saturated engine,or low degree superheat(in reality nothing much more than a stem drier)and then you can also get away with a displacement lubricator,which,having no moving parts,with the possble exception of a tiny needle valve,is easier to make. Such a lubricator was widely used on Victorian loco's and works like this.It is a tank,with a connection to the steam chest of the cylinder.The tank is pressure tight and is filled up to the level of the steam chest connection with steam oil.The connection is typically halfway up the tank.Steam from the steam chest enters the lubricator via the connection,and condenses into water.The oil floats on top of the water,and finds its way *back* down the connection into the steam chest,wherein it lubricates the valve, before getting blown out of the exhaust.The needle valve,if present, is to restrict the connection to the steam chest,and to regulate the suplly of oil.The disadvantage of this simple device,is its tendency to "gulp".When the throttle is closed,even partly,the pressure in the steam chest drops,and the piston tends to act as a pump.This sucks oil out of the lubricator,and if you've got your face over the chimney,you get liberally coated with dirty water,soot,and oil.And,yes,I *have* done it myself.Cant see a bloody *thing* afterwards if you wear specs!So before you peer down someones chimney ask him what typre of lubricator hes fitted.
One disadvantage of the displacement type is that you cant do an awful lot of testing on air.The diplacement does work on air(nothing to condense)so you got to plonk some motor oil down the exhaust hole.Of course the damned machine spits it right back in your face,and in this case you are more than likely setting the valve timing,which means you've *got* to have your face in the way,so you've just got to put up with it.And its cold!You dont get thses troubles with a pump lubricator,becuase it forces oil into the steam chest,even on air,but it is a little swine to make.Talk about watchmaking. It wasnt,in fact,until the invention of the mechanical lubricator in full-size work,that superheating became a viable proposition, since displacement lubricators just couldnt hack it.Until then enginners wanting increased efficiency mucked about raising boiler pressures and all sorts of weird and wonderful compounding setups. Similarly the invention,at the Derby works of the Midland Railway Company,by a man called Holt of steam sanding(actually *air* sanding at first)brought a brief resurgance of the very elegant "single wheeler"loco.This was a type with but one driving axle.Originally a 2-2-2 the type was reborn as a 4-2-2,superheated and with steam sanding. The basic prblem with gravity sanding is simply that the sand put down nominally on the rail for starting traction(critical with a single) more often than not landed anywhere *but* on the rail,and even if it did,it was udually a godd inch or two ahead of the point of contact between rail and tyre.The steam sander *blew* the stuff exactly where it was needed.However,rapidly increasing train weights,requiring double headed singles soon got rid of the type.I have an as yet unfinished example of this type at home,this time in 2 1/2" gauge. Gauges and scales may be interesting,just in passing.

The largest elevated track gauge in this country is 5".Usually driving trucks and passenger wagond are biult to this gauge for stability, regardless of the gauge of the loco.Elevated lines are laid multigauged, and it doesnt seem to bother a loco pulling off centre.In the states and Canada this gauge becomes 4 3/4".this is because,sensibly,if you are building to 1"=1ft scale,and you apply that to 4ft 8 1/2" it works out at about 4.75".Over here,some clown decided on five inches as a good gauge,then proceeded to use 1" to the foot.Which gave you a bit of a "squat" looking engine.So instead of going to 4.74" they altered the scale to the incredibly awkward 1 1/16"=1ft.
Which means that visiting Americans cant bring their locos for a run on our tracks,and vice versa.A 5"g loco is truly a hernia job to lift,even a tank engine needs two people,and I've seen as many as four struggling with a medium sized express engine.
3 1/2"g to 3/4" to the foot scale is lovely.As it equals 1/16" per*inch* you can include as much detail as you like,the engine isnt a pig to lift,can be kept in the house,and even a small example will easily pull its driver.Plus it is truly international. everyone uses this scale and gauge.

2 1/2"g at 17/32" to the foot(if you are a purist,most folk arent and use 1/2"scale) is a dinky little scale,but still capable of real work.The trouble is,the smaller the scale,the more your working clearances shrink,almost to vanishing point!In fact, in 2 1/2"g a miss is as good as...well,a miss.You can carry even a large express engine under one arm,and the cost of building such,both in terms of material,and,just as important,the capacity of the machine tools required is within most poeples reach.Despite this,and the many good designs available,the gauge fell into disfavour,but fortunately has seen a revival in recent years. The odd scale/gauge relationship doesnt matter much in this size, since its too small to include a lot of detail.Indeed,if detail is included,you can be sure it will damn soon get knocked off in working conditions.This is my favourite scale.There are others,both larger(ground level track)and smaller(watchmaking) but these three are the main ones.

Dixon has put forward the suggestion that an article entitled "Making Land Rover headlamp buckets out of Rose Planters"might go down well.Hum,I dont think I could go*that* far,but as a model Engineer you press some funny thing into use.The handrails attached to the boiler on English loco's are prominent so have to go into a 3/4" scale model.Mine are made from wire coat hangers.Its nice steel wire,and doesnt rust.

The boiler is lagged with felt,over which is a sheet of stainless shim steel.The stainless came from the scrappy,a lucky find,but the felt had to be bought:-( from the local craft shop."What colour,sir?" "Ah um,well doesnt matter,really"."But sir,it MUST matter".Me,redfaced"Oh well *that'll* do,there".

Another project under way(stalled) is a 3/4"scale diesel outline electric powered pre war shunter.The idea is to carry the battery on the driving truck.These little pre war diesel shunters were made before "designers" stuck their oar in,and,in consequence, make an attractive little model,which is safe for kids to drive. this one has a bonnet made from a bit of three inch square electrical trunking,the cab from a bit of steel shelf out of one of those horrible industrial steel cupboards(I had to re-arrange my filing system around the lack of one shelf at work),and the motive power is a permanent magnet windshield wiper motor,geared down.The Ammeter in the cab came from a prehistoric break-out box,data comms for the use of,one. Its actually a milliammeter,but a wire shunt soon fixed that. I'm not happy with the gearing though.Its worm and wheel drive, which means as soon as you take the power off,the wheels lock solid.So my intention is to relocate the motor,and use round belt drive.The belt will be from a vacuum cleaner.MORE red faces in the domestic appliance shop.It really *is* impossible to explain!They just dont understand.This little chap is,of course painted Deep Bronze Green,and will acquire a Limestone cab roof and interior.Diesel outline shunters are quite popular, but mainly in 5"g(the battery can be carried in the loco in this size)but I dislike 5" gauge.Father built one,an absolute monstrosity,with a lawn mower motor,which became the only one of his four models to get used.Takes two people to lift it. Mine,on theother hand,is only a foot long,is carried under one arm and on a crude test,pulled me quite happily,though slowly,(that gearing) up and down my own track in the garden.Oh yes,I've got my own. Eighty feet straight up and down,all three gauges.Construction isnt hard.The supporting pillars are brick.Secondhand when they knocked down next door's garage.The "trackbed" or longitudinals are *real* railway sleepers(ties).The local power station still has wooden sleepers,and the coal trains rip the track up summat shocking,the curves are so tight.The Electricity people dig up the sleepers and bury the things!Well,I knew a chemist at the Power Station, who said"How many do you want?"Nuff sed!

The miniature ties are inch square lenghts of packing case timber soaked in creosote and notched for the "rails" which are lengths of 1/4" by 1" black mild steel.Total cost at the time,about sixty quid.I've yet to put up "Station" signs either end.I thought "This End" and "That End" would be appropriate.Mind you,a set of buffers at either end might help,particularly when reversing from That End to This End.This End has a rather nasty bed of nettles...........
Enough!enough.Go on like this I'll send you all to sleep.

   
Copyright Dixon Kenner, 1995-2010. Last modified April 30, 2005.
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