TVT - The Skylark That Couldn't

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TVT - The Skylark That Couldn't

Post by GTB » Sat Jun 19, 2021 1:52 pm

This project grew out of the frustration experienced making a series of small steam loco projects perform satisfactorily. It can be done, but the performance of very small live steamers is on a knife edge and I don't have the patience to spend more time trouble shooting/reworking a model than the time it took to build it.

Hence this project...........


Model Notes

I've known of the existence of what Bill Russell referred to as the 'little' engine for many years and it was on the list when I took up modelling timber tramways in large scale. These Skylarks are only little takkers and having determined that getting one to work well as a live steamer in 1:20.3 scale was going to be a struggle, thoughts turned to battery electric power.

The first job was to build a basic chassis and power train and do some tests. These were successful and pointed the way forward to being able to fit adequate battery power in the limited available space and getting good running and speed performance.

The photo below shows the finished chassis after all the detail like headstocks, cylinders etc. had been added to make it look like a steam loco and not a diesel with a very strange wheelbase. General construction is based on my normal live steam chassis design. Like the old Mortein adverts said, 'When you're on a good thing stick to it'.

The motor is a 6V Pololu 20mm gearmotor with a 29:1 reduction and a 1:1 final drive using 0.8mod Hostalen mitre gears. The large diesel I built last year uses the same gears with a larger Pololu motor and this chassis runs just as well as the diesel. Quiet, smooth and plenty of power.

The motor is mounted at an angle to leave space under it for a chassis stretcher and the spring on the trailing truck. It sticks up out of the cab floor by a few mm, but is hidden by the firebox when the cab interior is fitted.

Skylark-11.jpg
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Bodywork is built the same way as I build live steamers. Normally I use 0.5mm brass sheet for bodywork, but this one is 0.6mm. The model is small and the more weight I can build into it, the better it will perform. Current calculations are that it will weigh about 1.8kg.

Kerr-Stuart must have owned a rivet factory, as their locos have more rivets than you can poke a stick at. On this model the rivets on the headstocks are individual 3/64" brass rivets, but those on the brass bodywork are punched out in the usual way, using the rivet press I made to use with my small mill.

The only real difficulty building the bodywork was due to Kerr-Stuart. Why their designers thought a cheap and cheerful industrial loco needed rounded cab and tank corners escapes me. Getting all the corners in the right place for the parts to fit together neatly was not easy. It can be done by making flanging plates and various jigs, but I draw the line at spending a lot of time making jigs for a one-off model. As usual I resorted to traditional bending bars and much bad language.

The photos below show the model cosmetically complete. It also emphasises how small a Skylark was, as the engineer figure scales out at 5' 8" which isn't tall by Aust. standards and he barely fits under the roof.

Skylark14-15.jpg
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That is now where the project stands. The control system is partly complete and will be manual, but due to our 4th lockdown and other reasons, it will be a while until I can get the electronics necessary to complete the model. Like the O&K completed recently it will then sit in the paintshop queue until the weather improves. The sun was out today, but it was as cold as charity outside. I'm not complaining though, at least I have a roof over my head and electrical power.


Prototype Notes

At the start of the 20th century, Kerr-Stuart built two of their little Skylark class locos and shipped them to India, which was only the start of their travels. A couple of years later they were shipped back to Kerr-Stuart, rebuilt and sold again for further service to Australian buyers.

K-S no. 742 had been named Lukee and no 743 had been named Rajah while in India. No. 742 was sold to a silver mine at Zeehan in Tas. and no. 743 to a copper mine at Pine Creek in the NT.

742 stayed in Tassie until after WW1, when it was sold to the SA Govt. and used at the pumping station at Cobdogla on the Murray River. A couple of years later it was sold again to the SR&WSC in Victoria and put to work moving coal skips from the VR mainline at Red Cliffs to another pumping station on the Murray River. There it stayed, being withdrawn in the early '50s and 'preserved' by spending many years plinthed in a local park. It was eventually rescued by local steam enthusiasts. Restored to running condition and renamed Lukee, it still runs trips for visitors to the area.

743 travelled even further in it's working life. After a few years at Pine Creek, it was sold to machinery merchants in Melbourne who then sold it to a copper mine at Whim Wells in WA, where it joined two older Skylarks. At the start of WW1 it was sold back to the same machinery merchants. After the war it was rebuilt in Qld. and sold to a gold mine on Misima Island off the coast of New Guinea. This mine folded a couple of years later and it was sold back to the machinery merchants, regauged to 3" gauge and sold to Bill Russell at Gembrook near Melbourne for his new timber tramway. It was purchased to haul sawn timber traffic out of the forest along the Black Snake Creek to the VR ng terminus at Gembrook, but it did not do well. It was too small to pull a useful load on a timber tram with sharp curves and a 1:16 gradient and it was also described as derailing at the first hint of a curve. It was left in the back of the engine shed at Gembrook and at first replaced with a couple of petrol rail tractors, until the work was taken over by an articulated loco built in Melbourne and based on the Heisler principle. The little Skylark sat in disgrace until after the war and was cut up for scrap when the timber tram closed and the site was cleared in the early 50's.


Regards,
Graeme

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Re: TVT - The Skylark That Couldn't

Post by -steves- » Sat Jun 19, 2021 2:22 pm

Very imformative post and a really good read.

As for the Skylark, well what can I say, perfection as always from yourself Graeme, it looks superb! :thumbup: :thumbleft: :salute:
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Re: TVT - The Skylark That Couldn't

Post by philipy » Sat Jun 19, 2021 2:25 pm

Admiration and envy in about equal parts, Graeme. :D
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Re: TVT - The Skylark That Couldn't

Post by ge_rik » Sat Jun 19, 2021 4:17 pm

Another great build of a fine looking loco, Graeme. I can understand why you decided to make this one electrically powered.

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Re: TVT - The Skylark That Couldn't

Post by Lonsdaler » Sat Jun 19, 2021 11:18 pm

That looks a beautiful loco Graeme - from looks alone you can't tell it isn't steam powered. I'm in admiration of your engineering skills. Sorry to hear you're experiencing yet another lockdown - it's hard when the weather is poor :salute:
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Re: TVT - The Skylark That Couldn't

Post by 11thHour » Sun Jul 04, 2021 8:58 am

Hi Graeme,
The design has a fair amount of weight behind the fixed wheelbase . Did you weight up the front or rely on the springing of the trailing truck to balance it up.
Tim

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Re: TVT - The Skylark That Couldn't

Post by GTB » Sun Jul 04, 2021 10:34 am

11thHour wrote: Sun Jul 04, 2021 8:58 am The design has a fair amount of weight behind the fixed wheelbase . Did you weight up the front or rely on the springing of the trailing truck to balance it up.
The weight distribution of the model is pretty iffy even with the trailing truck spring and the centre of gravity at the moment is just forward of the driving axle. When I get around to wiring it up, the battery will be in the smoke box and forward part of the boiler, which will move the CofG further forward between the drivers. I think it will be a model that will always pull better when running cab first though........

Graeme

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Re: TVT - The Skylark That Couldn't

Post by GTB » Sun Sep 05, 2021 6:52 am

About the time I wrote the first part of this build story, we were in shutdown again and getting some of the electrickery to finish this project got a lot more tricky. Normally I just drive down to the local Jaycar, but that's more than 5km away and probably closed anyway.

The plan was to use the speed control circuit that was removed from the motor mule when it was converted to r/c. The fly in the ointment was fitting the battery pack into what is a very small model by Fn3 standards. The battery cells would fit, but the available battery holders didn't.

Jaycar used to sell long life NiMH cells with solder tags, which could be made up into a battery pack, basically these were Eneloops clones. I prefer the genuine Eneloops cells, but these aren't available in Oz with solder tags. Of course when I went looking online, Jaycar no longer sell their version and the nearest source of Eneloops with solder tags was in the Netherlands.......

There was a supplier of a suitable battery pack in Sydney, but they didn't supply direct, only through agents. I finally ordered one off a small company on the NSW South Coast, who were able to make up a suitable battery pack using genuine Eneloops.

A couple of weeks ago I was waiting for materials for another project to arrive, so I dug out all the parts needed for fitting the speed control in the Skylark and started making the various cosmetic bits that were needed to hide the electrickery and also stop the magic smoke from escaping.

The first photo shows the parts laid out along with the loco body, dummy firebox and various electrical bits. From left to right, the battery pack with a JST plug fitted, the little perfboard with the active components fitted to the cab front (which provides additional heatsinking for the power transistor) and at the front the switch panel with charging socket, switch and PTC resistor for overcurrent protection. On the right is the dummy firebox with the reversing switch and speed control potentiometer fitted inside.

The second photo shows the chassis with the motor wiring and the backhead showing the speed control (throttle) and reverser, along with some rudimentary details to make it look more like a boiler backhead and less like an electronics enclosure. The wiring is fitted with miniature plugs so that the electrical parts can be removed if necessary without having to try and wield a soldering iron in the confines of the cab.

Skylark-16-17.jpg
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The third photo shows the boiler with the battery pack, which just fits inside the boiler/smokebox assembly. With the battery weight in this position, the loco is much better balanced and is no longer tail heavy.

Skylark-18.jpg
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All of this was eventually fitted in place, with much stress and bad language. Tested, repaired, tested again and finally the loco was bench tested.

The weather cleared enough yesterday for the first test run outside with a train and the next two photos show the Skylark emulating her sister loco with a string of v-tippers. The first photo is running along the back straight and the second shows the train being pushed back into the yard. This worked only because the loco is pushing funnel first. The very short coupled wheelbase and long overhang makes this impossible if the loco is running bunker first, due to what amounts to buffer lock.

Skylark-19-20.jpg
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The lat two photos show it on a run today emulating it's prototype on Russell's timber tram, taking a load of sawn timber on it's way to the VR interchange at Gembrook. Unlike the prototype, there were no derailments and three pairs is well within it's haulage abilities. The first photo shows the train made up in the yard and ready to go. The second photo shows it coming off the bridge.

Skylark-21-22.jpg
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Now all I have to do is wait for the weather to warm up a bit so I can get the model painted and off the list of things to do.

To be continued.........

Regards,
Graeme

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Re: TVT - The Skylark That Couldn't

Post by Peter Butler » Sun Sep 05, 2021 10:57 am

A lovely little locomotive and so beautifully constructed. It will look superb when painted.
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Re: TVT - The Skylark That Couldn't

Post by philipy » Sun Sep 05, 2021 1:44 pm

Peter, has said it all. Lovely little loco.
Philip

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Re: TVT - The Skylark That Couldn't (Part 3)

Post by GTB » Wed Dec 01, 2021 12:16 pm

This model has been in the paintshop queue for several months, but the rain has been getting warmer here and with a few dry days, the paint job has been completed.

The original intent was to paint the model in the usual faded black colours, but I recently bought a WW2 vintage US made drafting instrument set. Research suggested it was of good quality and it didn't appear to have had much use. Some tests were run on a painted test panel with the ruling pens and the spring bow pen and the results were better than I've been getting with a more modern German ruling pen.

The plain black colour scheme looked a bit dead, so the decision was made to line it using the new (to me) drawing instruments. Lining is a simple 0.020" red line, using Humbrol #60 vermilion. This was the only tin of bright red I had and while I'm not a fan of Humbrol paint since Hornby took over, the results are OK.

I've been having ongoing model painting problems in recent years, but a change in airbrush a while ago and a lot of experimentation seems to have ironed out most problems, even when using Humbrol. This time around it looks like the varnish has worked OK as well. Of course this varnish formulation is no longer available, so time will tell if the problems return when this tin runs out and I have to use the new version............

This paint job went well enough that I'm now encouraged to put the O&K, that I built earlier this year, through the paintshop next. .... 8)


The first photos show the completed model sitting for it's family portrait in late afternoon sunshine, just before the storm clouds returned. The storm missed us though.

The primer used is an industrial etch primer and the top coat is the usual mixture of three different shades of black mixed from various ratios of Revell satin black, grey and red oxide. The lining, as previously mentioned, is Humbrol #60 and the satin clearcoat is an Aust. brand sold by the big green shed.

Skylark-23.jpg
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Skylark-24.jpg
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The last photo shows the loco pushing a train of timber bogies into the TVT exchange sidings just before the storm hit. I've found with this loco. that it is best to run trains cab first, which minimises issues with the excessive side play at the rear and also increases traction, as the load on the front coupler transfers weight onto the drivers.

Skylark-26.jpg
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.......Although as it happened, the storm hit the suburbs to the north and missed us.

Skylark-25.jpg
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Regards,
Graeme
Last edited by GTB on Fri Dec 09, 2022 4:25 am, edited 1 time in total.

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Re: TVT - The Skylark That Couldn't

Post by Andrew » Wed Dec 01, 2021 12:48 pm

A beautiful loco, and a VERY nice finish!

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Re: TVT - The Skylark That Couldn't

Post by Peter Butler » Wed Dec 01, 2021 12:54 pm

Just gorgeous!!!
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Re: TVT - The Skylark That Couldn't

Post by LNR » Wed Dec 01, 2021 12:57 pm

Glad your getting some positives from painting again. Nice Job, specially on the lining.
Grant
PS, still waiting on my delivery!!

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Re: TVT - The Skylark That Couldn't

Post by philipy » Wed Dec 01, 2021 3:28 pm

Superb as always.
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Re: TVT - The Skylark That Couldn't

Post by ge_rik » Wed Dec 01, 2021 4:02 pm

Excellent!!!

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Re: TVT - The Skylark That Couldn't

Post by GTB » Wed Dec 08, 2021 4:15 am

Eighteenth Steam Run 6.jpg
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"When I grow up, I'm going to pull passenger trains, just like my Dad." .............

Regards,
Graeme

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Re: TVT - The Skylark That Couldn't

Post by LNR » Wed Dec 08, 2021 7:02 am

Don't know about the engine, but the trees sure have grown!
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Re: TVT - The Skylark That Couldn't

Post by ge_rik » Wed Dec 08, 2021 2:57 pm

GTB wrote: Wed Dec 08, 2021 4:15 am "When I grow up, I'm going to pull passenger trains, just like my Dad." .............

Regards,
Graeme
Seems to have plenty of puff, Graeme.....

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Re: TVT - The Skylark That Couldn't

Post by GTB » Fri Dec 10, 2021 4:49 am

ge_rik wrote: Wed Dec 08, 2021 2:57 pm Seems to have plenty of puff, Graeme.....
I haven't tried it, but the drawbar pull measurements suggest it would be able to pull ten bogie wagons. Not having grades helps......

Graeme

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