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Aster JNR B20-3 0-4-0T

a review by Nick Wantiez


Aster Hobby Corporation has recently introduced a beautiful 1/24 scale 0-4-0 shunting locomotive known as the Japanese National Railways, (JNR), B20.  Configured in late 1943, when shunting locomotives were desperately needed to support the war effort, the B20 was envisioned to be a simple, low cost, yet rugged design, which was to be produced under time and tooling restraints which most nations would have considered impossible.  Undaunted by the difficulty of the assignment, the locomotive design committee set to work and soon developed a viable prototype.  


The 0-4-0 B20 had a simple coal fired non-superheated boiler. Its plate frames supported two conventionally mounted outside cylinders with piston valves driven by Walschaert valve gear.  Side tanks provide an ample water supply while coal was carried in the rear bunker.  The first B20 went into operation in 1944 - it lived up to all of its requirements and the design was so successful that production continued into 1947 almost two years after the war’s end. 


The Aster B20 is a 1/24-scale model of the third production locomotive.  It is a faithful representation of the original and was scaled from the B20-3, which is currently on display in Japan.  It operates on gauge 1 track and is size compatible with G scale equipment – I am currently hauling two Bachmann passenger cars fitted with knuckle couplers, which match up perfectly with the B20’s couplers.


Specifications of the Aster B20-3 are as follows:

Scale:        1/24

Gauge:       1 (45 MM)  (1 ¾ in)

Length:       302 MM over couplers  (11.8 in)

Width:        106 MM  (4.1 in)

Height:        148 MM  (5.8 in)

Weight:       2.8 KG  (6.2 lb)

Wheel Arrangement:  0-4-0 35 MM drivers (also called an 0-2-0 Four Wheeler B) 

Cylinders:    12 MM bore x 20 MM stroke with Walschaerts Valve Gear

Boiler:          Center flue butane fired 120 cc water capacity 80% full

Working Pressure:  2 kg/sq cm  (approximately 30 psi)

Fittings:  Two safety valves, pressure gauge, water gauge, regulator, check  valve filler plug.

Lubricator:   Roscoe displacement type

Minimum Radius:  0.55 M


The kit is typical of previous Aster products.  Parts are neatly packed and identified.  All hardware is provided, as are some special tools, however it will be necessary to have some other tools, such as nut drivers and pliers, at hand to successfully assemble the kit.  These are identified in the instructions.   


Aster’s Ms. Chihiro Kawasaki, who once lived in the United Kingdom and has excellent English language skills, is responsible for customer service and  assuring that the drawings and instructions are satisfactory for English speaking builders.  I found them to be clear and easy to understand.  


My kit went together in about fifteen hours without any difficulties.  There were a few tricky assemblies but the instructions gave sufficient guidance to make them seem routine.  Being a senior citizen whose eyes have seen better days, I found it necessary to use 1 ½ power reading glasses during most of the assembly.


While locomotive building is fun, my first love is operations so even though the Seattle weather was dark and gloomy at the time, I cleaned off my track and steamed her up.  Photos 1 through 8 show various shots of the B20 - it is a handsome little engine with excellent performance.


Operating the B20 is easy.  First the chassis is oiled with a light machine oil and the lubricator, which is located in the right hand side tank, is filled with steam cylinder oil.  Next the boiler is filled to 80 % full using 120 CC of distilled water.  I fill through the upper fitting, which is located in the sand dome, although a check valve fitting is located on the lower left hand side beneath the cab, which will accommodate a trackside pump.  


The butane tank is located in the cab and is filled through the top using a removable fitting which screws into the tank.  The burner is easily lit.  While photo 5 does not clearly show this, to light the burner one merely opens the smoke box door, inserts a flame source and cracks open the burner valve.  The burner quickly lights, the door is closed and the valve adjusted to provide a flame with a “mild” roar.  Steam is up in a few minutes.  


She will be a bit stiff for the first few hours but soon loosens up and runs like a dream.  I have only been able to put a few hours on my locomotive and have found it to be user friendly and very powerful.  You will note in the photos that the cab roof is not in place.  Aster provides hinges for the roof but I decided to leave it unhinged since it is much easier to refill the fuel tank and there is less chance of damaging the cab.  When these photos were taken, the cab roof was resting safely on my workbench.


Aster is also in the process of designing a butane utility car, which will carry a large supply of butane and water.   The car will contain a battery driven water pump.  The butane supply will be attached to an existing lower fitting in the B20’s butane tank.  Aster expects that the new car will be available later on this year.  While there are no specific instructions provided, the B20 can be radio controlled if desired.     


In summing things up, I found the Aster B20 to be an excellent small-scale locomotive, which is easy to assemble and operate.  It is rugged and reliable - much like its full size prototype several of which continued in service as late as 1972.  I believe that it will be a good first project for newcomers to the hobby as well as an interesting addition to the collections of experienced builders and I recommend it without qualification.


This article originally appeared in (Vol. 36. No. 4) (July / August 2002) issue of Live Steam.  Appreciation for permission to reproduce it on SouthernSteamTrains.com is expressed to Nick Wantiez, author, and to Clover McKinley, Editor of Live Steam.


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