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TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 4:09 am
by GTB
Well sort of......

This is a model of the Harman locomotive built in Melbourne for the Forests Commission of Victoria (FCV) for use on the 2' 6" gauge Tyers Valley Tramway in Gippsland. The sorry saga of the design, building and subsequent failure of the Harman to perform is documented in an article published in 'Light Railways' Issue 42, pp 12 -19, some years ago. For anyone interested, there is a free pdf available online. ... 41_044.pdf

This beast was articulated on a similar principle to Schwarzkopf locomotives and was also geared. It was the Victorian timber industry's equivalent of Bullied's Leader, as it was overweight, stopped at every water tank, steamed well only when the planets were in the right conjunction and was modified several times for better performance without much success. It survived longer though, as it was shoved into the back of the shed at Tyers Junction and sat rusting and unloved from the late '20s until it was cut up when the line was closed and the site cleared in the early '50s.

The Tyers Valley Tramway was about 70 miles west of the area where the TVT is supposedly located, so a model of a Harman loco isn't particularly relevant to the timber trams in the area, but it looked like an interesting thing to build and was extremely unlikely to appear in commercial rtr form.....

With Australia heading into the usual Christmas shutdown, I was looking for a project that would use parts and materials I had in stock and came across the Harman while reading back issues of 'Narrow Gauge Downunder'. The 'Light Railways' article has a drawing of the original proposal, which did not match the photos as built. The NGDU article had a better drawing and some additional photos of the loco as built and some photos also turned up online that had been taken post WW2 of it mouldering away in it's shed, so the die was cast.

I thought about attempting to make a live steam model, but the boiler is very small and there's not much space in the model to hide an osmotor and drive shafts. The chances were a live steamer would perform like the prototype, somewhere between badly and not at all. So battery electric was the choice. The model is built to Fn3 scale (1:20.3) and 45mm gauge. Unusually for a timber tram, the Tyers Valley line was built to 2'6" gauge, but I'm not about to lay 37.5mm gauge track.

Being basically a diesel type mech, the first part made was a basic bogie to work out the design and do some test running. The first two photos show the drive arrangements and the third shows it under test on the track.


That was interesting, as there wasn't a lot of space in the bogie for a layshaft to couple the axles and the gearmotor, even though it was a small 6V N20 type. I had planned to fit slightly larger motors, but my preferred brand of Pololu have stopped selling their 16mm size gearmotor and the data sheets suggest that the N20 size has the same power and torque output, so theoretically would do the job.

The first motor bogie tested was fitted was a 6V N20 with 1:50 gearbox. When powered with 6 NiMH cells for the test runs, it almost achieved lift-off speed on the track, being clocked at a scale 55mph. Just a little high for a prototype that was hard pressed to achieve 2mph with a load in traffic. :shock:

The motor was replaced with a 1:100 reduction gearbox and this cut the speed to 25smph with 6 cells. The plan for the model is to fit a speed control, so with the replacement gearmotors fitted it should be controllable down to the prototype design speed of 10mph.

With the speed sorted out, the second bogie was built and both were fitted with the final detail parts, before work started on the chassis. The prototype frame was fabricated from massive RSJ sections and even more massive headstocks cut from steel slab. No wonder the loco was overweight. The photo shows the bogies fitted to the frame and on a test run to check clearances, that it could negotiate turnouts and get through the sharp curve in the triangle.


That leaves the boiler, cab and bunker to fabricate and fit. All conventional construction, mostly soft soldered brass sheet. As always the last 10% of detailing takes 90% of the modelling time, but the mechanical construction is finally complete and the model is now ready for the paint shop. Wiring and final detailing will have to wait until it wends it's way through the painting queue....... :roll:

The photo show the final result in the brass, waiting for a coat of paint. There is no documentation of the colour it was painted. It seems to be generally assumed that it was plain black, but the photos of it being delivered from the factory to the VR goods yard for forwarding to Moe suggest that it may have been painted in a two colour scheme.


The prototype Harman locomotive was replaced by a Climax locomotive after it's failure, which is what the FCV had wanted in the first place.



Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 6:23 am
by philipy
Nice build Graeme. I'm not quite clear as to whether both bogies are powered?
I do like the look of that loco, shame it was so unsuccessful in real life, just hope your version gets on better. :D

Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 7:27 am
by ge_rik
Beautiful - as always with your builds.
It seems remarkable to me that such small gear motors can provide the power needed.


Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 8:36 am
by GTB
philipy wrote:
Sat Mar 18, 2023 6:23 am
I'm not quite clear as to whether both bogies are powered?
Both bogies are powered. Those little motors are powerful for their size, but I don't think only one would haul 2.8kg of loco plus a train as well. There is a plan B if two N20 motors aren't up to the job, but it's messy.
philipy wrote:
Sat Mar 18, 2023 6:23 am
just hope your version gets on better.
You and me both.....


Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 9:40 am
by philipy
I thought only one motor would be pushing it a bit!

With my penchant for oddball loco's I was tempted to have a go at this once I read the article, but at over a foot long it's too big for my line. I've always fancied a Shay and this has that look without the outward complications, but... :roll:

Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 9:45 am
by Trevor Thompson
That is a very nicely made loco. I am particularly impressed with the motor drive system. I am following your example with geared motors. I have bought some to try and I'm amazed how quietly they run.


Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 10:08 am
by BertieB
That’s terrific. It looks great.

Re: TVT - Down in the Forest Something Stirred

Posted: Sat Mar 18, 2023 10:41 am
by Peter Butler
Absolutely stunning work and so well thought out.