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Throwing the Curve Ball(bearings)

MinerChris

Entry posted by MinerChris

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The first job off my ever increasing list for this roster break was to finish off making the backscene pieces. This is to both block off the scenic area to 239x600mm as per the DJLC criteria, and to try to limit the amount of background light coming onto the layout. I’d spent a little while over the last four weeks pondering how to neatly curve the dark corners away and tie this onto the layout. In the end I opted for a piece of 1/32” birch ply (the thinnest sheet, singular, in the model shop,) which was curved around a set of plywood formers, scoring vertically along the backside of the curve to achieve the 75mm radius bend evenly. The formers are spaced using M4 threaded rod and nuts, which are inserted into holes in the baseboard top and the lighting rig, to keep the correct location tight to the back of the layout, and to stop everything from falling over. Once I was happy everything was in roughly the right place the backscene was glued onto the formers to make sure that pesky gap at the top join is permanent.

 

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The front end of the sides have also been glued onto another length of 8mm square hardwood strip, which are in turn, screwed to a couple of new front wing pieces to allow them to be held securely in place, but still be removable for painting etc. Similarly, where the ply sheet has been cut to allow the baseboards to separate, it has been secured to the back plywood support with a couple more countersunk M2 screws.

 

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Come 2020, when it’s time to extend the layout to it’s full size, there should only be 12 holes to repair in the baseboard, and a new piece of ply to cut and curve around the formers. ‘Why not 8 holes?’ you might ask (4 curved piece anchors, 4 for the front wings) that’s right, I drilled the holes with the baseboard the wrong way round the first time.

 

You’ll have noticed that there is an random extra box in front of the baseboards. This is the start of the control panel. A sheet of 'glass look,' acrylic will be bolted to this, with the layout diagram below printed out below this, in a shameless ripoff of Kylestrome’s control panel for Kyle. I’ve tried as much as possible to keep to the Southern nomenclature, as I don’t have any idea what the PDSWJR would have used. Hopefully someone will pick out what I’ve done wrong, aside from missing half the diagram out, before I get to printing this off rather than afterwards!

 

With the backscene conundrum out of the way, my attention moved onto the traintable in the fiddleyard. Unfortunately although vastly improved, my plywood cutting knife wielding skills don’t extend to curves quite yet, so these were first marked out with a big set of dividers, and cut roughly with a jigsaw, before finishing off with sandpaper.

 

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The spin motion is based around a thrust ball bearing, picked up from Cromwell tools, which was araldited onto a couple of spacers above and below to sit the top of the deck at the correct height compared to the baseboard. Those spare bits around chassis etches have finally come in useful! The holes for the attaching screws have been drilled oversize to allow for a little adjustment, to ensure that the table spins around with the minimum gap from both sides of the table. The bearing works with nearly no friction, perhaps a little too well really; I can’t resist spinning the table around far too quickly! Time will tell if rust becomes a problem, as the bearing is only mild steel, but I don’t think it’s really worth the extra effort of engineering an oil bath for it to run in.

 

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Finally I took the opportunity at the last Midland area group meeting to start cutting PCB sleepers for the pointwork, carefully avoiding disturbing all the sleepers for Lydford town glued on the reverse side of the board. Looking at this again, I can see one mistake I’ve made already!

 

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Best Regards.
Chris.

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2mmMark
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In 2mm, smooth free movement is much better than anything which has any "stiction". It's all too easy to derail a fiddleyard full of stock if  sector plate sticks then suddenly moves.

 

Just occured to me that a taper roller head bearing would make a really good pivot. Something like ebay item 270924167058.  Taper rollers are self-aligning and automatically take up any clearance.

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MinerChris
In 2mm, smooth free movement is much better than anything which has any "stiction". It's all too easy to derail a fiddleyard full of stock if  sector plate sticks then suddenly moves. Just occured to me that a taper roller head bearing would make a really good pivot. Something like ebay item 270924167058.  Taper rollers are self-aligning and automatically take up any clearance.
Your're right Mark, but I guess the key to not building up stiction will be keeping the bearings clear of grot and rust.You've got me thinking now about roller bearings too, I'd possibly look at these if I had any problems with the thrust bearing, but with deep ball races the bearing needs a good shove to separate the alignment.

 

nice progress

 

Beautifully made.
Thank you both!Chris
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