Copenhagen Fields & TFW’s workshop

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Tim Watson
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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Mon Jul 08, 2019 9:24 am

I have now completed the crossheads, connecting rods and motion support bracket. Nice and chunky, but some of the clearances were a challenge!
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Tim

Tim Watson
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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Mon Jul 15, 2019 12:00 pm

After a day demonstrating fine scale stuff at the MRC, Keen House, yesterday, I now have Valour running with the connecting & coupling rods in place. The wheels and chassis are chemically blacked, so they shouldn’t need to be removed any more.
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Demonstrating wheel quartering live, on camera, is surprisingly stressful; I can demonstrate dental operative procedures much more easily.

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https://youtu.be/w1-dvt1G_c0

Tim

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Atlantic 3279
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Re: Copenhagen Fields & TFW’s workshop

Post by Atlantic 3279 » Mon Jul 15, 2019 4:47 pm

I suppose you can't really anaesthetize the audience, can you?
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Tim Watson
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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Tue Jul 16, 2019 11:16 am

I did notice one chap, overcome with the tension, close his eyes for a few moments.

Tim

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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Fri Aug 02, 2019 11:31 pm

Work has proceeded on the tender for Valour.
The 8x16mm Tramfabrik motor is mounted in a block of brass and has a hefty flywheel fitted.
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The tender chassis is obviously split frame (or will be) and the block is bolted to this, taking care not to give any shorts.
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Construction of the tender body was straightforward, needing some adjustments to the tabs & slots because it is etched in 8 thou nickel silver. Certainly faster than scratch building!
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The self trimming hopper went together with a little bit of adjustment and is currently a passive fit in the top of the tender. It will be soldered in place a little later in the build.
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The tender frames as etched in the kit have a half relief for the springs and a clever fold-up system for positioning the side valance at the same time as the frames, as can be seen at the top of the picture.
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However, I wanted to widen the distance between the frames by about 0.5mm to give the tender chassis a bit more space for freedom of movement. I was also not overly keen on the half etched ghosts of the axle boxes & springs. So I turned the frames round and cut out a strip of 0.85mm thick brass, 1.9mm wide, to make up the valance. These strips were soldered on to the running plate, giving it a bit of extra strength. The frames were then soldered on to these, again giving a much stronger structure. (The loose tender top is not quite seated home in the second picture.)
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This increase in rigidity of the tender sides has allowed me to tidy up the insides of the tender rather well.
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I may hang the tender on the back of the engine to increase traction which has caused me to think about arrangements for allowing the tender chassis to run semi-autonomously - I do enjoy working out these sort of challenges. The tender body is currently very light, but there is plenty of room for some brass or copper tungsten weights.

Tim

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Atlantic 3279
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Re: Copenhagen Fields & TFW’s workshop

Post by Atlantic 3279 » Sat Aug 03, 2019 9:29 am

Looks like excellent progress and it is very encouraging to see the etched parts for the tender going together so well.

Rather oddly, it was not until I viewed the latest post above for the third time that all of the images were displayed. I got a few more each time I re-opened the topic. Such matters are beyond my understanding.
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john coffin
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Re: Copenhagen Fields & TFW’s workshop

Post by john coffin » Sat Aug 03, 2019 10:36 am

Looking really good Tim, nice to see something designed about 10 years ago still meets the criteria for today,
albeit for a smaller scale.

What you call ghosts, I called locators for the various castings, and at that time, I am not sure we could find
any castings for the roller axleboxes. However, your solution is a good one.

Paul

Tim Watson
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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Mon Aug 05, 2019 6:50 am

After a bit of pondering, the tender and engine are now coupled up. The tender chassis is free to move up and down at the front, being restrained by a pin, but can pivot / rock at the rear. The body weighs down on the back of the engine via a very precise coupling which moves sideways easily but has very little play vertically.

The tender - engine coupling looks quite simple.
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The back pivot is a domed shape, tapped 12BA, that engages in a dimple in the PCB of the chassis stretcher - effectively a ball and socket with a bolt through it.
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Soldering this brass turning to the tender body was easily achieved using the 12BA HSS tap to locate it in the hole (this was also tapped). Soft solder will not stick to high speed steel - but as a precaution it did have residual cutting fluid on it.
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The front end pin was a 14BA bolt soldered to the body work, running in a hole in the PCB stretcher, visible in this dismantled shot. The bolt was surrounded by a shouldered tube to give a smooth surface, as can be seen. The length of the tube was long enough to give generous vertical movement of the front of the chassis.
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The shoulder is designed to just accommodate a 20thou thick draw bar and 8thou washer, with a 14BA nut and lock nut (as insurance) to hold it all together.
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The end result can be seen in this photo: holding the engine in thin air, by the tender.
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The loco has similar pivot arrangements. The fall plate from tender to engine will also be used to stiffen up the joint in the vertical axis. The tender chassis should track OK, as it has quite a bit if weight on it with the motor mounting block and flywheel, whilst the tender body will have more weight added to it to help adhesion. If it all proves unnecessary, then the fixings can be converted to a rigid system with ease; but tricky to engineer these sort of things retrospectively.

Tim

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Re: Copenhagen Fields & TFW’s workshop

Post by Atlantic 3279 » Mon Aug 05, 2019 9:30 am

A very neat coupling arrangement.
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Tim Watson
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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Mon Aug 05, 2019 9:37 pm

After cracking on with the UJs, Valour is now powered from the tender. These are the standard ? type for my locos. The end cap with the hole in it helps to keep the UJ in one end: it will be pushed fully home when construction is more complete, to be behind the coal space opening.
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https://youtu.be/FPIGSSeMdKk
It ran well enough under power and, after gapping the PCB in the correct places and connecting the motor leads, it should be good for dragging itself along the tracks.

Tim

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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Tue Aug 06, 2019 8:28 pm

Valour can now pull itself along the test track. Pickup is currently (ouch) only from the tender. The flywheel imparts about a revolution of the driving wheels when she is stopped from a reasonable speed.
https://youtu.be/4RECbgVxyEc
https://youtu.be/5zYzXAe_5ok
I am very content with the running, with the tender picking up well on its own and the body riding steady and stable. There isn’t any significant weight in the engine, whilst the tender is very rattly with little weight to bear down, so performance should improve with more weight from both.

Tim

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Re: Copenhagen Fields & TFW’s workshop

Post by Atlantic 3279 » Wed Aug 07, 2019 10:35 am

Wonderful.
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Re: Copenhagen Fields & TFW’s workshop

Post by john coffin » Wed Aug 07, 2019 11:42 pm

Who is this man, and where does he get the skills?

Looking at the moving pictures, it does not look like a 2mm scale model at all.

Fabulous work Tim, and great progress.

Paul

Tim Watson
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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Thu Aug 08, 2019 10:36 am

I wasn’t happy that Valour was noisier than it should be, but at certain speeds it would quieten down. I traced the noise down to the fact that the motor has quite a bit of end play on the shaft and the back of the flywheel was slapping the bearing face at certain speeds. The flywheel was removed (by putting the soldering iron on it at 450 deg C to kill the Loctite) and was then advanced down the shaft by less than 0.5mm. She now runs with just the rumble of the gears and also free-wheels better. Noise = inefficiency.

Tim

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Re: Copenhagen Fields & TFW’s workshop

Post by Tim Watson » Fri Aug 16, 2019 10:59 pm

It’s only a small part of the total, but getting an engine with a front bogie to track correctly requires a means of supporting and restraining the front end, whilst at the same time allowing the driving wheels to maintain traction.

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This little pin, spring and curved slot should do the trick for Valour. The bogie side frames are made up in layers from the etch and the pivot is actually a 14BA bolt, with the threads reduced in the turning areas so as to reduce friction. The slot is tapping width for the bolt, which screws through it into the shouldered brass pin which also restrains an N gauge coupling spring for downward pressure and a little side control. A washer is soldered to the spring to prevent it insinuating itself through the slot. I think it is advantageous to have the bogie slot at the bottom of the stretcher, rather than the top, as it will give better stability.

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The central brass pin is located in the PCB spacer between the cylinders and soldered to it’s top and bottom sides, respecting electrical neutrality of course.

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It is evident that clearances have had to be made for the bogie wheels, which are scale size at 7mm, but of course with oversized flanges. Experience has shown that clearances need to be far more than you might think!

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Having the bogie on the front begins to give Valour a racy look. The white muffs will be replaced with a scale axle at the front and a small black muff at the rear.

https://youtu.be/e3diA-gGHs8
The video shows the bogie in action.

Tim

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