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So you just use the second stage liquid for blackening and clean/polish, dip then rinse? It says not suitable for brass but I trust you. 

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None of the non-ferrous metals really blacken, Rich, but at least they go brown. 

 

Tim

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Posted (edited)

I wasn’t quite happy with Valour’s coupling rods as, on filing away the etched cusp, they came out too skinny, especially when compared to the beefed-up connecting rods. 

4BCF56DC-5D47-432F-8DE9-216D2FE8B77D.jpeg.b36921ce9cfaa9568be7b8c87b99bc9e.jpeg

 

So I have fitted strips of 5thou nickel silver to the top and bottom of the rods.  

 

3A665B1B-6C91-48E2-A3D3-9CCDBCA5A1D9.jpeg.078158a1580cab371c788a6dbc8b6566.jpeg

This makes them much stronger; especially over the pivot joint and also closer to the chunky GC appearance. 

 

C84433BC-A690-428C-B6DC-B6980A14A9F5.jpeg.fac389bff1b52424a2caa5603ec9d564.jpeg

 

Much happier now.  Anyone who has the etches from me could avoid this extra work by filling the cusp with solder and being less fastidious with the filing. 

 

Tim

Edited by CF MRC
Trimmed coupling rods further & better picture.
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On 04/07/2019 at 23:13, CF MRC said:

Crossheads are always quite fun to make.  Silver soldering is a good way of ensuring that at least the piston and inner crocodile are nice and solid.

The starting point is a piece of thick metal (0.7mm thick) to fit between the slide bars with a notch at one end to accommodate the 0.5 mm diameter piston. This also benefits from having some flats filed on to it to give a more precise location. 

http://i64.tinypic.com/2gv3qqs.jpg

 

The silver solder was in a paste form and very easy to flash the joint with a little gas flame.  

http://i68.tinypic.com/16kta1j.jpg

 

This was then placed in the vice and the socket for the piston filed into the end, rounding off the corners, taking advantage of the safe sided file.

http://i63.tinypic.com/10ygjdl.jpg

 

Alignment in the slide bars was then checked: at this point - it should be a tight fit. 

http://i66.tinypic.com/3535yqp.jpg

 

Followed by a 1mm diameter hole to accommodate the little end of the connecting rod. 

http://i66.tinypic.com/33nwazb.jpg

 

This was then opened out rearwards to be able to take the connecting rod. The outer face of the cross head can also be seen resting against the slide bars. 

http://i64.tinypic.com/289lzs3.jpg

 

Making two of anything can be easily achieved by sweating two pieces of metal together and roughing out the shape, just once, then separating them. The little end pivot hole is 0.3mm diameter. 

http://i67.tinypic.com/16arwxl.jpg

 

The two components were soldered together using a tapered stainless steel pin (Jim will recognise it) to stabilise the outer face by holding it on a charcoal block whilst the inner face was held onto it with downward pressure on the piston.  This assembly was joined with electrical, relatively high melting point soft solder, as I didn’t fancy my chances at the whole lot not melting down into a blob if I tried to hard solder it.  I normally use steel for valve gear - which would be less likely to melt, but as this is kit is etched nickel silver, that is what I have used here. 

http://i68.tinypic.com/359igj9.jpg

 

A tight but smooth fit is what was aimed for at this stage.  Subsequently, the mating surfaces of the cross head slippers were filed using a slotting file to give a running clearance with the groove locating the cross head on the slide bars. 

http://i63.tinypic.com/1hicz.jpg

http://i64.tinypic.com/24eqr2w.jpg

 

The outer cross head face was filed to represent the prototype and the piston socket dressed to look more convincing.  The little end of the connecting rod will have a pin silver soldered to it and the round outer boss of the cross head will be represented by a washer soldered onto this pin to hold it in place. 

http://i63.tinypic.com/14xfas5.jpg

 

It never ceases to amaze me what you can do with a phone camera. 

 

Tim

 

 

 

 

 

 

 

It never ceases to amaze me how you make such excellent models.

 

Don

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The self trimming tender for Valour has made some progress over the last few days in Cornwall. The etched components fit together reasonably well, assuming that the slots are opened up a little and the tabs thinned down. 

AFC17F35-4058-4415-B109-C122EB846E23.jpeg.ccf790eeeaa88d78dfe56bcb2e173120.jpeg

The top of the sides are soldered up from two components to give the beading - this is quite clever,  but a little bit tricky. 

A23EBAE7-66A4-40FB-B6C4-331F31B9690F.jpeg.928edba778d3cdd065bea4f53a5771e7.jpeg

I have cut out various parts of the tender internal structure to make room for the motor and flywheel, which will be attached to the chassis.  It was probably easiest to solder the side sheets on at this time. 

F10B7DF8-AA72-48DB-B61B-FD4F8F1E88A6.jpeg.4a32f26701b1ef7cada44cd2319455ed.jpeg

The tender top will have a variety of details  added such as the water scoop mechanism covers, bulkheads and toolboxes. 

31E172FF-3B9E-491F-9A2D-8159228BF061.jpeg.d176e5c42ad520669240f6836ece41c1.jpeg

 

Tim

 

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Posted (edited)

The self trimming tender is designed to make the fireman’s job easier by the use of gravity.  A better name might be a ‘hopper’ as it looks rather like a grain store.  The etches make up this complicated structure with a bit of judicious filing and fitting, certainly nothing a bit of solder won’t sort out. 

E4732729-5959-4EF2-B47A-C7BBA83A523B.jpeg.d129860496454d223b339cf4663693e6.jpeg

The top is still loose and is a good passive fit. It will probably stay that way until I have  the chassis and motor in place.  

C13CC1F6-BF53-4A1A-85D2-E6FF671F3BD8.jpeg.0393f3a16fd9da20043d9467e9052241.jpeg

It is really easy these days, working with small 8mm diameter x16 mm long motors.  Quite a far cry from 40 years ago when we started squeezing Portescap 1219s into tenders. 

 

Tim

Edited by CF MRC
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The tender chassis and motor mount have made good progress this week.  

B77CA98F-C304-4C8A-B9AA-5C8E5ABFA0C6.jpeg.dfcd2735d72667d1d055aea37fec7851.jpeg

The 8mm Tramfabrik motor has an old fashioned ‘stay alive’ brass capacitor on the end.  The outer shroud of the UJ has not yet been made for the  ? shaped drive shaft. 

A6C9F4D8-7322-4AE9-9E6E-55DED2AAB5E6.jpeg.c3d5ae2bad90a4c5f38987c4c8b4502f.jpeg

The motor mounting block is bolted to the chassis, taking care, of course, to avoid shorting out on the frames.  The reason for the strange shape will become apparent. 

2648F2FD-4363-40E1-BFC6-2C4528BC8A8D.jpeg.9fa051b1627d161528a42629984f5466.jpeg

 

D15B0DC3-8DEA-4507-A958-C41DC82DCFD5.jpeg.69c5f647b67f4afa7273b57a7f14b861.jpeg

Obviously, the coal space will have a cover over the motor & flywheel.

 

Tim

 

 

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I can’t see any wires to your capacitor, Tim. Are you sure it will work? I don’t want you getting all in a spin later on... :rolleyes:

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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.

242ei4y.jpg

 

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.)

124aamd.jpg

2wfmxjr.jpg

 

This increase in rigidity of the tender sides has allowed me to tidy up the insides of the tender rather well.

vh6ckw.jpg

 

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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Does anyone make transfers for Great Central tender lettering?

 

Tim

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Posted (edited)

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.  

2vuevt1.jpg

 

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.  

33ttbo0.jpg

 

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. 

2uiuibm.jpg

 

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.  

28l4zrc.jpg

 

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. 

amywz6.jpg

 

The end result can be seen in this photo: holding the engine in thin air, by the tender.

34eymxk.jpg

 

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

 

 

Edited by CF MRC
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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. 

2hdbbmc.jpg

2bd0yc.jpg

2ivzdx4.jpg

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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Looks like she'll get up a good turn of speed too!

 

Jim

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Posted (edited)

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.  

 

 

 

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

Edited by CF MRC
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Great stuff Tim.  A loco that runs that sweetly with power just from the tender is certainly something to aspire to!

 

Simon

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Posted (edited)

Fascinating reading how you've dealt with all this Tim, and the end result runs superbly.  Great!

 

Rich

Edited by MarshLane
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The test track looks very interesting too!

DrDuncan

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Thanks for the comments.  I try to make the posts useful, showing techniques and ways of doing things. There are obviously many solutions out there, and mine are by no means the best, but CF engines are probably the hardest-worked in 2mm scale.  Recording all this activity has been revolutionised by the use of the iPhone camera.  Not a patch on Nick’s video though.  

 

The test track has to be at least 20 years old and is used when we are at exhibitions.  It has A Pentroller and a straight DC controller built in. It also has a patent Stewart Hine wheel cleaning machine that makes more noise than an angle grinder and is guaranteed to take wheels out of quarter...

 

Tim

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10 hours ago, CF MRC said:

.......It also has a patent Stewart Hine wheel cleaning machine that makes more noise than an angle grinder and is guaranteed to take wheels out of quarter...

The old Minitrix wheel cleaner can be rather good at that too!:mellow:

 

Jim 

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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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Tim, using Loctite to fix a flywheel is overkill. Pritt (the heavy duty version if you have a choice) will do the trick just as well, and it is much easier to get the flywheel off again if it ever becomes necessary. Push a cocktail stick into the Pritt so that the sharpened end of the stick gets a good loading of the adhesive, and then push the stick into the hole in the flywheel from the side that the motor/gear shaft will pushed into, then mount the flywheel. The Pritt will take the strain immediately but the joint will become stronger over the next few days as the Pritt dries out.

Pritt isn't strong enough for gears, of course, because of the load they carry, but a flywheel is very different.

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I recently used Pritt to attach a paper template to a piece of ribbing to cut sections out of the latter. (More on that elsewhere later) It was easier than the cyano I had used before and worked just as well. 

 

Jim 

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On 07/08/2019 at 21:32, CF MRC said:

Thanks for the comments.  I try to make the posts useful, showing techniques and ways of doing things. There are obviously many solutions out there, and mine are by no means the best, but CF engines are probably the hardest-worked in 2mm scale.  Recording all this activity has been revolutionised by the use of the iPhone camera.  Not a patch on Nick’s video though.  

 

The test track has to be at least 20 years old and is used when we are at exhibitions.  It has A Pentroller and a straight DC controller built in. It also has a patent Stewart Hine wheel cleaning machine that makes more noise than an angle grinder and is guaranteed to take wheels out of quarter...

 

Tim

 

I do not expect to get anywhere near your skill level but do appreciate the notes and ideas on how to do things. For instance the way you have arranged the tender weight to bear on the loco. I would probably have thought about letting the wheels move up and down in the chassis. I assume with your approach the chassis has enough weight to give reasonable track holding while the body weight is shared  between the loco drawbar and the pivot at the tender rear. I would have worried that the weight being taken behind the rear wheel of the tender could lift the tender front wheels. I presume the weight is distributed to put maximum pressure at the drawbar end.

Thanks for taking the trouble to document all this

 

Don

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David: I am happy using Loctite as it flows well and is easy to place. With a 1mm diameter shaft, getting Pritt in the correct place might be challenging.  This flywheel is not running passively as it is also transmitting the drive through the UJs.  Pritt is certainly an under-rated adhesive: especially for paper and card. 

 

Don:  90% of the tender body weight will be ahead of the rear wheels so they won’t lift, whilst the tender chassis with motor mounting block and flywheel is quite heavy in its own right.   Certainly seems to work OK so far and the front pivot arrangements will get further stability from the fall plate resting from tender to engine. 

 

Tim

 

 

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