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A CR 670 Class part 3

Dave John

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I am awaiting some parts for the engine, so I thought I would push on with the tender.

 

The kit does provide all the spacers and a basic compensation beam for the tender chassis. But as usual I have odd ideas about these things. So the chassis sides are adapted for High Level hornblocks and then connected by a length of double sided copperclad. This gives two large lands on the top for pickups and suppression components.

 

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The semi circular compensation beam would be visible through the tender cutouts, so I fabricated this one . Good steel pivots to reduce friction and adjustable for ride height by means of an easily accessible  screw underneath. Yep, completely lockdown madness, but why not.

 

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A pic of the chassis made up with wheels and brakegear. The pickups are gold tips from scrapped relays soldered to 12 thou spring steel guitar wire. Hopefully this will produce a low drag 6 wheel pickup to aid good running. Might need a bit of a tweek, but all seems to meet the pushing round the track and through points test.

 

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The tender body went together fairly smoothly. This class of engine ran with a bewildering array of tenders during their lives, so I have tried to work closely to a known period photo, some slight variations from the kit.  Forming the top flare with its flared corners is a time consuming task, but I think I got it about right. Probably a bit of filling will be needed along the joint, but that will be easier to see after a coat of primer. As ever I see things on photos I missed before, a few bits of tidying up needed. 

 

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For a while the CR used a strange style of handbrake with a vertical capstan wheel geared to a vertical shaft. I can only assume the gearing gave some mechanical advantage, but having a finer pitch on the threaded end might have been simpler. Anyway I have a tin of watch gears. So I had a go at fabricating the mechanism. The horizontal shaft is actually a tube so you can spin the handwheel round. Did I mention lockdown madness?

 

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Hope everyone is keeping well.

 

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@jwealleans recently posted a link to his method of making tender flares:

Not something I've actually tried, I'm afraid.

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Northroader

Posted (edited)

My understanding is soldering gold is not recommended as it rots it?

Edited by Northroader

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Thats pretty much how I do it compound, bit of old rubber sheet from something rubbery.  Old wellies or something. The straight bits are ok, the corners are the fiddly bit.

 

The gold contacts are I think gold plated onto something and then bonded to a brass Northroader. I solder the wire to the other side of the brass.  Its something I have tried on the last few builds, but if it does cause problems longer term I'll have to go back to pb strip. Worth a try, never know til you try it. 

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It's allways nice to see some chassis compensation done in the Sharman tradition. I've not thought of using the gold contacts of relays for pickup contacts before, so I'll definitely give that a try. Think I must have a fettish for brass and nickel silver, looks really nice.

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Great handbrake! It is somehow exactly what I would expect of the CR :)

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Fabulous. So much more like engineering than mine!

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Just a thought - having gone to the trouble of putting a piece of double sided pcb material in there, did you not consider making it "structural" and "splitting" the frames, then you wouldn't have needed to bother with the pickups?

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It's possible Richard, but that would mean using a conductive wheel ( special order ! ) and a split axle with an insulating muff. Then you have the muff bearing on the compensation beam, so the muff would need to be accurately sleeved in something hard like tufnol. I have in the past made conducting wheels by making a ----O shaped brass bit and soldering it to the rim of the wheel with the O bit lightly against the face of the bearing, but that means you have to be careful about sideplay, especially in a small tender like that. Works ok on a 4 wheeled loco bogie, but needs careful setup so that you can pick up from the sides of the bogie, have a pivot and get the compensation beam  to work nicely. 

 

I am watching the way the 2mm fs folk make split frame chassis, with side rather than central compensating beams. Might have a go one of these days. 

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26 minutes ago, Dave John said:

I am watching the way the 2mm fs folk make split frame chassis, with side rather than central compensating beams. Might have a go one of these days.

A technique commonly used in Split-frame Scale:

92CDCAEA-4B27-476A-A3BC-85C38DD3D9B9.jpeg.261026756c08e4f1f97f63b7bcb461f0.jpeg
 

Crossbeam from PCB:

E3A83E9C-4A33-46E0-B3D5-98924590A317.jpeg.6aad1d4f18c83eb81a7fd35891f82efe.jpeg

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2 hours ago, Regularity said:

A technique commonly used in Split-frame Scale:

 

Hi Regularity, I notice from your images that the axles have insulation close to each end, do you know what material is used for this ?. I have tried styrene in the past, but the fit becomes loose very quickly,  thought about trying acetal or nylon but not got round to that yet.

 

Regards Pete

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3 hours ago, snitzl said:

 

Hi Regularity, I notice from your images that the axles have insulation close to each end, do you know what material is used for this ?. I have tried styrene in the past, but the fit becomes loose very quickly,  thought about trying acetal or nylon but not got round to that yet.

 

Regards Pete

That’s fabric, not paper, grade Tufnol, force-fitted in a Myford.

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