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Perry's Revolving Fiddle Yard. - Scratchbuilding. - More Practical Help - Your Model Railway Club
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 Posted: Mon Oct 15th, 2007 04:50 pm
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Robert
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Article written by Perry on the previous forum.

Dated 18th. August 2007


This thread is hopefully going to be the story of how I succesfully built a Revolving Fiddle Yard or Train Turntable. By that I mean a turntable that will hold several complete trains; not just the locos, and turn the whole lot through 180 degrees without needing to handle any of the stock.

The story started out as a plan for a 6-road traverser but after a suggestion by my wife, it was modified to become the current plan. The search then started for a suitable pivot. This had to take into account the weight of the table itself plus the weight of any stock on it. It took a while for me to find the ideal thing, but this is what I ended up with:

[size=The Pivot Mechanism:]

The turntable plates themselves are made of pretty heavy-duty pressed steel and - get this - it runs on ball bearings! The label shows the name HAFELE which I think may be German, but the centre boss of the things bears the name 'TRENDLER. CHICAGO. IL. USA'

The mounting plates are described as 170mm square and it can handle 360 degrees of rotation. It is substantial enough to handle a big piece of MDF, so as soon as I have slightly modified the baseboard frame it should be 'full steam ahead'.

It comes in a plastic bag without any fancy packaging or labelling:





Top (or bottom) view:





and edge on, just showing the ball bearings:





There was nothing on the packaging, such as it was, or on the shop shelf to suggest it's proper function. It was labelled as a 'Revolving Fitting 360 Deg 170mm' and that's about all the information there was. I guess it's just a strongly made universal turntable base plate on which to mount and turn pretty much anything - within reason, but it looks very strong and is quite heavy. There were only two on the shelf and I think they may have been there for a while; the label bore the date 26/05/2005.

Here is the link to the manufacturer's website (Thanks, Tim):

http://www.trendler.com/prod-swivel.html

It set me back nearly �15 but it should do the job well and last for years.

The next step will be the modification of the baseboard frame that will support it.

Perry                                                                                                                                                                  B                                                                                                                  



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 Posted: Mon Oct 15th, 2007 05:03 pm
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Perry continued on 19th. August 2007

I have been giving this project a bit of thought and have come up with the following list of things to be resolved along the way:

1. The table top will be 4 feet long. Will it flex too much, allowing the extreme ends to drop below the optimum height for the rails to line up? If so, some form or guide or support will be needed at th ends. I have some small rollers that might be used for this.

2. I don't think I will be able to cover the MDF top with cork. The reason for this is twofold. Firstly, a cork covering makes the drilling of accurately placed holes difficult. Being soft, it allows the drill bit to wander before it bites into the MDF. Secondly, I will probably need most of the 3.2mm that the cork would have taken up to allow for the top to clear the frame.

3. Track wiring. Whilst being fully aware that uner normal circumtances all track is 'live' when using DCC, this won't be the case here. I only want the road in use to have power. This will prevent any errors in loco selection causing trains to be run off the end of the table accidentally. I intend to fabricate a hand-operated latching system that not only locks the road in use in place, but also transmits power to the rails. I have a design in mind and will describe it in detail later.

Perry



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 Posted: Mon Oct 15th, 2007 05:11 pm
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Dated 19th. August 2007


Further to my 3-point post above, I have realised that the geometry of the track on the table itself is going to have to be sorted out.

I hope you don't mind me laying out the thought processes for all this, but I think it will help show why things are done the way they are. :?

Obviously the tracks can't simply be parallel because the table will now rotate rather than sliding straight across. That means that they will need to curve away each side of the centre line of the table to enable them to line up with the single feeder road. The number of roads will have to be an odd number; 5 or 7 probably, because only the middle road can be completely straight.

As the rolling stock won't now need to be 'crane shunted' (lifted off by hand) as would happen with a plain traverser, the track spacing can be closer than I had planned; probably back to 2" centres or thereabouts. Depending on the radius of the curves needed to align the roads, this clearance may need to be eased a little.

I plan on using some old scrap lengths of track and a piece of scrap MDF (See? - Never throw anything away. It will come in handy eventually!) to produce a mock-up of one end of the table, so that I can get the measurements, radii and layout sorted out before I start using the good stuff.

I have purchased some brass tube and rod, making sure that the rod slides snugly inside the tube, with which to make the latches. The plan is to solder some shortish pieces of tube to small rectangles of PCB (Printed Circuit Board) and use the brass rod to form the 'bolts' that will hold them in alignment. The PCB bolt and keeper assemblies can easily be drilled and screwed into place beside the tracks and have the additional advantage that it is very easy to solder the wiring to them, thus providing power to the selected road. This should become clearer when I get around to making and photographing them.

O.K. Enough thinking 'out loud' for now. I hope you can see where this project is going. If you can't, please ask and I will try to clarify it for you. Otherwise, just wait and watch as the build progresses, and hopefully all will become plain. :grin:

Perry



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 Posted: Mon Oct 15th, 2007 05:20 pm
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Dated 19th. August 2007


The baseboard frame was modified this evening. All I had to do was remove the middle cross-member (4 screws) and install two new ones (8 screws). The new ones are made from the same nominal 2" x 1" planed timber (or whatever they call it these days) but are positioned 'flat' between the side members instead of on edge. Set with their outer edges 7" apart, the pivot plate will sit firmly across them. I need some particular sized cheese-headed bolts to hold the pivot plate in place, so the job is on hold until I can get some - probably tomorrow.

I worked out the height for the new cross-members by laying some 3.2mm cork - the same stuff I used for the track base - on top of the baseboard frame. I then laid the 12mm MDF top on top of that and offered the pivot plate up from underneath. I marked where the bottom of the plate came to and took it all apart again. The pencil marks were at 21mm from the bottom of the framework (although this will vary if you are using different sized timber to me). I lined the top of the new cross-members up with these marks, and the ones 7" part, and screwed them into place.

The top of the pivot plate is 3.2mm above the top of the baseboard frame providing plenty of clearance for the rotation. The top surface of a piece of 12mm MDF mounted on top of this should therefore be level with the top of the cork underlay on the adjacent baseboard.

Blimey! Re-reading that makes it sound complicated, but is wasn't. :shock:

When the pivot plate is bolted in place I'll post a couple of photos of the progress.

Perry



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 Posted: Mon Oct 15th, 2007 06:51 pm
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Dated 20th. August 2007


At about 4am today I had a sudden thought! The pivot plate mounting holes are actually slots to allow for adjustment. They are aligned corner-to-corner. I may therefore need to mount the bottom plate on the frame at an angle of 45 degrees, rather than square to it as was planned. I reason that any adjustment of the actual pivot point will need to be made at the bottom plate. If it was made at the top plate, the table would not revolve in a true circle.

I will have a closer look at this later because if the adjustment needed is only a millimetre or two, the clearance of the mounting bolts in the plate slots may take care of it. I don't want to modify the frame again if it's unneccesary.

So, it may already be time for the first modification. :roll: It probably won't be the last. :roll: :grin: I hope that by pointing these things out as I go along, it may help others to avoid the same pitfalls.

Perry



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 Posted: Mon Oct 15th, 2007 06:51 pm
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Dated 20th. August 2007


I went out into the workshop (my garage :roll: ) at about 7:30am and set about sorting the baseboard out. My nocturnal epiphany was right; I did need to slew the pivot plate through 45 degrees. Rather than moving the cross-members already in place, which might have weakened the structure, I decided to strengthen the whole assembly by putting two more cross-members in alongside those already in situ, plus another one in the middle to allow for the adjustment across the baseboard frame. I think this may turn out to be a good move as all the rotational stresses will centre on that area. I managed to get some nuts and bolts this morning but don't have time to fit them today. :sad:

Perry



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 Posted: Mon Oct 15th, 2007 06:52 pm
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Dated 20th. August 2007


Hi Les,

The table will be 4 feet long and will therefore hold a large loco and three coaches, or the equivalent, on each road.

I can't claim to have invented this, so I won't be applying for a patent. :roll: :grin:

Here is a very rough plan - NOT TO SCALE.





The circle is the theoretical 4-foot circle of MDF with the cut-out sections at each side shown in blue. The red lines within the remaining section of the circle are the fiddle yard roads; each about 4 feet long. The red line to the left is the feeder road on the adjacent baseboard. The black rectangle is the base frame of the rotating fiddle yard. The only things visible will be the white portion with the track on it, and the framework that supports it and the associated pivot. In practice, the 4-foot circle of MDF would not exist. The table section of the circle would be cut from some MDF less than 2 feet wide, but I have included the circle to try to explain the concept.

Hopefully it is apparent that if the fiddle yard table is revolved about it's axis, each of the red roads will eventually line up with the feeder road in turn.

So, line up an empty road on the table, drive the train onto it from the feeder. Rotate the whole thing to line up the other end of the road holding the train and you can drive it out again - facing the opposite direction.

When the table is swung round, it should only project about 12 inches either side of the base frame and front and rear. No good if your baseboards are tight against a wall, but mine is out in the middle of the room, so I have the space to turn it.

Perry



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 Posted: Mon Oct 15th, 2007 06:53 pm
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Dated 21st. August 2007


With the new cross-braces sorted out, the pivot plate was fitted in place.




I used 6mm pan-head bolts to mount it. (Or cheese-head - I can't remember which is which :? ) I first drilled pilot 3mm holes, then counterbored with a 16mm spade bit, before finishing the clearance holes with a 7.5mm bit. This allowed me to recess the nuts and washers.

The gaps between the cross-braces will allow me to get a screwdriver in to tighten the slotted-head bolts when I mount the table. :wink:




Here is close-up of the underside of the mount showing the counterbore:




The bolts had a plain washer fitted beneath the head and under the nut.




I laid an offcut of 12mm MDF on top of the pivot to get an idea of how it was all coming together. The 'proper' table will probably be a bit wider and be shaped at the sides to reduce weight.:




I then rotated the MDF to illustrate how much of an overhang there will be when it is turned:




Having run out of 6mm MDF to finish the backscene board of the adjacent baseboard, I am not able to fit the latches at present. My intention is to take exact measurements for the table with the baseboards latched together. That way I should be able to allow for a clearance of perhaps a couple of millimetres at the ends. If I measured this without having the baseboards latched together, the lack of compression of the joint between them could throw that measurement out considerably.

Perry



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 Posted: Mon Oct 15th, 2007 06:55 pm
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Dated 21st. August 2007


I disappeared for an hour or so earlier this evening and got some 6mm MDF and other oddments from my local B&Q. Providing it isn't raining when I get home from work tomorrow, I'll get the table-saw out and cut the MDF for the backscene board and trim strips to size. I have to do it outside otherwise everything in the garage gets coated with MDF dust - not nice stuff to breathe in, apart from the mess it makes. :sad:

As long as I get the pieces of MDF cut to size and screwed to the framework, I can easily take them off again later for painting. I just want to get the latches fitted soon so that I can make more progress with this project.

The Health & Safety bit: For anyone else contemplating using MDF, please be aware that you should use a face mask and eye protection when cutting or sanding it because the dust is nasty stuff. Also, I think it is still advisable to paint or seal all MDF surfaces because it can allegedly give off harmful chemicals over time if left in it's raw state.

Perry



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 Posted: Mon Oct 15th, 2007 06:56 pm
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Dated 22nd. August 2007


The plan is to drill a small pilot hole in the centre of the table, then use a router with a long trammel arm to cut the correct radius on each end. I've got a long piece of 8mm / 5/16th steel rod that I can use for the arm. This should should give me the required degree of accuracy. It worked on a smaller scale when I cut the Peco turntable well. The slotted holes in the pivot plate will give me plenty of room for the fine adjustment of the table position.

Perry



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dated 23rd. August 2007


I feel I'm starting to see this project really taking shape now. I've got the rest of the job planned out - partly on paper and partly in my head. I'm bound to hit a snag or two along the way and if I do, I'll be sure you let you know - no matter how daft the mistake. :shock: :roll: It's silly little details that usually catch me out. Fortunately, one thing that didn't do so, but could have done quite easily, was the cutting of the MDF trim strips. If I had cut them to the same width as those used on the rest of the layout, they would have fouled the rotation of the table by about 3mm. :? I reduced the height by 6mm to make the top edge flush with the top of the baseboard frame, thereby leaving myself the 3mm or so clearance that the table should have. Some photos later should make all this clear.

Perry



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 Posted: Mon Oct 15th, 2007 06:57 pm
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Dated 24th. August 2007


The trim strips, last backscene board and baseboard latches were fitted this afternoon. :-)

Over the forthcoming weekend I plan to cut the table to shape and length using my router. As I can't get my head round any way to lay out the geometry for the tracks at the moment - even though I know how they will eventually look - I'm going to cut the end curves of the table first, leaving the width of the table at a full 24 inches. I think the best way to sort it out after that will be to lay the centre road first as it will be the only straight one, then lay the two either side of that parallel to it in the middle of the table, curving out to line up with the feed road, and so on with the remaining roads. Each road can then be aligned with the table rotated the appropriate amount. I guess it'll just have to be done by eye. As the table is four feet long and lengths of Peco flexible track are only about three feet long, I may need to lay the curved roads in two pieces of about 2 feet long each, allowing a little more for the curves. That way I can keep the join in the straight middle section to ensure the best chance of keeping the curves smooth and even. Once one end of each of the roads is secure and lined up with the feeder, I can rotate the table to do the same with the other ends.

After all the track is laid I should be able to trim the waste material from the sides of the table with an electric jigsaw to reduce the bulk and weight. If you look back on this topic to the rough plan I drew, the final result I am trying to achieve should be a bit clearer.

I haven't forgotten the photo's. There just isn't much difference to see at the moment. As soon as I start on the table itself I'll get snapping. :wink:

Perry



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Dated 26th August 2007


Right chaps!

Here is the next stage in the building of the Rotating Fiddle Yard.

It's a bit of a marathon post, I 'm afraid, but with loads of pictures. (That should keep Jeff happy! :wink: )

The trim strips were previously screwed to the baseboard frame, ensuring that their top edges were flush so they won't foul the table when it rotates.





The 12mm MDF table material was carefully measured (three times! :shock: ), marked out, and the centre point drilled with a 3mm bit. A steel rod was fitted to the router and a trammel point screwed on the end. I also taped it in place on the rod to make sure it didn't move. When using this set up, it would be handy to have a helper to steady the trammel point and make sure it doesn't jump out of it's hole. I was working alone so I had one hand on the trammel point and the other operating the router; not ideal! :shock:





I did all the cutting from the upper face of the board, taking four passes increasing by about 3mm each time to reach the full depth. This image shows one of the first passes.





After completing the first cut, I moved the waste to one side before taking taking this picture, just for clarity. The cut was actually only a few millimetres wide. I chose to leave a large piece of waste at each end of the table so that the router had something to slide on. I didn't fancy having it hanging over the edge of the material as it would have made the router much harder to control. All the passes with the cutter were made anti-clockwise so that the cutter was drawn into the workpiece by it's rotation, and not forced away from it.





The router and trammel were then relocated to the other end of the workpiece ready for the second radius to be cut.





Once this had been completed, the table was offered up to the base and measurements for drilling double checked.




The bolts were indentical to those used to mount the pivot plate. I drilled 3mm pilot holes, then used a 16mm spade bit to recess the bolt heads and washers, finishing off with a 7.5mm drill bit to allow clearance for the bolts.




Turning the whole assembly over, I rotated the table until the gaps I left in the framework gave access to the bolts. Nuts and washers were fitted but not overtightened. Slight fore and aft adjustment may be needed when the unit is connected to the layout. This will be simple as the mounting holes in the pivot plate are slotted.

The last four pictures need a little bit of imagination on the part of the viewer. :? Imagine if you will, that the section of track I have laid on the table is the full length of it. Also imagine that there are two other roads either side of that one. It can then be understood that a train can enter at one end, the whole table rotated 180 degree, then it can be sent back in the direction from whence it came. :grin:












All that remains to be done now it sorting out the track laying, ascertaining if I will need to put some little supporting rollers under each end of the table - dunno yet :roll:, fabricating the bolts and keepers that will hold the table in alignment as well as transfering power to the road in use, and possibly trimming the table sides to lessen the weight. This might not be necessary; I'll decide on that later.

So there you are gentlemen. :wink: The main contruction has been completed. The work involved in cutting out and drilling the table, plus bolting it all together, took about an hour and a half. The baseboard obviously took longer but once this had been prepared it was plain sailing.

I'll continue this soon when the above-mentioned processes get underway.

Perry



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Dated 27th. August 2007


After due deliberation, I decided that supporting rollers at each end of the table would be a good idea. Not too much work for a considerable gain in functionality. :grin:

I had some small rollers made of pressed steel with polypropylene wheels in stock, so these were the obvious choice.

I decided to use three rollers, two at the feed end of the table and one at the other, working on the theory that contact at three points should remain fairly constant - using the three-legged milking stool concept. :wink:

I used some offcuts of baseboard framing timber to make the assemblies. (See? I told you not to throw anything away! :roll: :lol: )

I cut six 2" long pieces of timber, then cut a shallow concave into three of them with a sharp chisel to make room for the rollers. This was necessary because the rollers project through the metal frames by small amount and would bind against the wood otherwise.





The pairs of timber blocks were screwed together at right angles and the roller mounted using small self-tapping screws. I found it necesary to open out the fixing holes on the roller frames to 3mm to allow the use of these screws. There is just enough room to go out to 3mm, but not much more without weakening them.




Sorry about the poor focus on this image. :oops:

The single roller at the end of the baseboard frame was sited centrally along the frame crossmember, with the roller at 90 degrees to long axis of the table.

I used pieces of cork tile, offcuts from the track-laying, to make spacers between the table and the baseboard frame when screwing the roller assemblies in place. This is to ensure that the rail heights on this and the adjacent baseboard will match.

This picture, and the following one, were taken with the table inverted for clarity. Obviously the table rides on the rollers when it is the right way up!




The two at the feed end of the table were set equal distances either side of the centre line with the rollers set at an angle to allow for rotation.




I may still consider fixing some strips of ply along the edges of the table to prevent it drooping during rotation but it needs a bit of 'testing' first. :grin:

I'm looking forward to getting the track laid now. :wink:

To be continued.

Perry



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 Posted: Mon Oct 15th, 2007 06:59 pm
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Dated 5th. September 2007


Some 25mm x 25mm aluminium angle has been fitted to the sides of the table to give it some support whilst it is being turned and thus not in contact with the end guide rollers. The aluminium angle gives strength without increasing the weight too much. The strips will also provide something to get hold off to turn the table.

The aluminium was drilled with a 4mm bit at 12 cm intervals. The top outer corners of the strips were cut off and filed to a rounded profile so there are no sharp corners to catch your hands on.

Some scrap pieces of cork tile left over from tracklaying were used as spacers between the framework and the table. I did this so that there was no chance that the support strips would be screwed into place whilst the table had any 'droop'.

The strips were then clamped in place with a couple of G-clamps and 2mm pilot holes drilled through into the MDF.

The strips were secured with some 12mm No.8 self-tapping screws, this length being chosen so there was no possibility of the screws breaking out of the MDF beneath the table.








To be continued.

Perry



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Dated 5th Sep. 2007


In readiness for track laying, ten pairs of screws were inserted into pre-drilled pilot holes near the curved ends of the table. I used half-inch No.6 brass countersunk head screws because they won't rust and have flat heads. Being brass also makes them nice and easy to solder the rails to.

I marked the curved edges of the table at three-and-a-half-inch centres, then marked out the track widths centred on these marks. I allowed 18mm, bearing in mind that OO gauge is 16.5mm.





Using a short piece of scrap track, I put the screws into the MDF until the lower surface of the rail just slides over the tops of the heads.





Obviously when the actual track is laid the rails will protrude a short distance beyond the screw heads.

I will align the rails carefully, adjusting the height slightly if need be by means of the screws, before I solder the rails in place. I intend to work from the outer ends of the table towards the middle when I'm laying the track because alignment with the access road is all-important. I should be able to sort out any slight misalignments in the middle of the table without any problems.

Perry



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Dated 12 Sep. 2007


I tackled the laying of the track on the rotating table today. As the table is made from 12mm MDF I decided to use Hornby Track 'Pins' (more like small nails!) as they are strong enough to be tapped into place with a small hammer after pre-drilling the sleepers.

The brass screw heads that had previously been adjusted for height, were tinned with solder. Then the first five track sections were laid. I started with the middle road, for the simple reason it was the only straight one. Having that in place then gave me a visual reference when I laid the rest.

Working from the table end, I trimmed the sleepers and soldered the rails to the screw heads, using a large spring clip to hold one rail in alignment whilst I soldered the other.









When all five roads were in place at one end of the table, I cut the tracks to length at roughly the mid-point of the table. I avoided doing it exactly in the middle because the bolt head holes would prevent pinning at that location. The next picture shows the track before being cut to length.





After trimming the chairs from the end sleepers, I fitted metal rail joiners to all five roads, then working from the middle of the table outwards this time, I connected up the remaining track and led it out to the screw heads at the other end of the table. These roads were pinned in place to ensure a smooth transitional curve and the rails cut very slightly overlength (by a millimetre or so) to allow squaring up with a metal file. I chose to cut the rails with a miniature disc cutter, but a small hacksaw or razor saw would work just as well. It just saved me time! :-)





All the track was then complete.


Although I still have to fabricate the locating and power transfer mechanisms, I loaded the table with random rolling stock just to illustrate the capacity of it. Power tranfer mechanisms! Doesn't that sound grand? :roll: All they will be are small bolts made from brass rod sliding into brass tube keepers. Wires attached to both sides will transfer power to which ever road is locked into place by the bolts. There can't be any 'accidents' by selecting the wrong loco then!








Then the table is turned by hand.





And finally, after a 180 degree turn, the previous 'arrivals' are ready to 'depart' - and all without being touched by hand.



That's all for now. The bolt mechanisms are next - but not today... :sad:

Perry



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 Posted: Mon Oct 15th, 2007 07:01 pm
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Robert
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Perry continues...

I have been giving some more thought to the bolt mechanisms today. I only need one pair of bolts but I will need ten pairs of keepers for them to slide into. I'm going to have a hunt around a hardware store or two tomorrow to see if I can save myself a lot of work - even if it will cost a little more.

Perry



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I saved myself a lot of time, material and effort today when I made a couple of mock ups for the bolt keepers I need to install on the RFY table. I wanted to see if I could get away with making the PCB bases three-quarters of an inch square as this would give me heaps of room to put a pair between each pair of adjacent roads. All looked OK at first. I marked and drilled two 4mm holes in each keeper plate to take the 12mm No.6 self-tapping screws I will use to secure them to the table. It was then that I realised that the heads of the screws would not allow the 9/32" tubing to be soldered in place; they were marginally too close together. :sad: I therefore mocked up a pair of one inch square bases. These have plenty of room for the tubing and screw heads but not much room for lateral adjustment between the table roads.

I think I may just try a 7/8" square base tomorrow and hope that's an acceptable compromise. If not, I will have to use the one inch bases and just be really careful I don't get any short circuits between them.

As I need to cut 20 bases out of PCB (plus a few spares :wink: ) I will make up a small cutting and drilling jig out of scrap timber. It saves a lot of measuring and marking out and ensures uniformity. It also saves a lot of time. As each base will need a wire soldered to it for connection to the table road, I will drill two small holes in each base, one near each of two adjacent corners. I can also do these using the jig. The reason I need to drill two holes in each is to make them interchangeable. Otherwise I'm going to need to make them 'handed' which doesn't really seem necessary.

Here is a rough sketch that I hope will convey the general idea.





Perry



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All 20 (+spares) of the PCB parts of the bolt keeper bases were cut out and drilled today.

I made up a cutting and drilling jig from an old piece of plywood and some offcuts of baseboard frame timber. Basically it works like a mitre block with an end stop, ensuring that all the pieces are cut to the same length. One 'spare' base was then drilled for the fixing screw and wiring holes. This was used as a drilling template so that the bases could be drilled four at a time with the PCB squares held snugly in place in the jig. It's difficult to hold small parts such as this when trying to drill freehand so I felt this was the best approach.





I used a 7/8" square base this time as 3/4" was too small and 1" was too big. (Sounds like Goldilocks all over again! :lol: ) A 7/8" base gives room for the screw heads and for the 9/32" tubing to be soldered into place. There is also room for some adjustment when fixing them into place between the tracks.

The next job is to cut the tubing into appropriate lengths and then to solder them into place. The cork tile squares that the PCB bases will sit on will be added when they are fitted to the RFY table.

Perry



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