JohnBS Posted April 12, 2013 Author Share Posted April 12, 2013 Meanwhile, I haven't been totally idle . . . . I've made progress in putting together a simple chassis. The techniques are very much as in the 2mm Scale Association handbooks and no machine tools (other than a Dremel) were harmed in the making of this. Starting with the components - Wheels are split axle, from the late Mike Bryant's range, which I guard jealously.These are N-gauge, with flanges turned down slightlly, but 2mm SA sets would be even better. The frame material is 0.5mm hard brass and rods are from scrap lengths of old Peco nickel-silver track, yet to have the flanges and bullhead filed flat. The worm, gears and the axle muffs (green packet in lower right) are 2mm SA components. The motor is a Mashima 1215. At the top is the primed 3D printing of the loco superstructure and backhead and, to the right, is the invaluable gear-meshing tool from the 2mm SA The background drawing is the CAD product that the 3D printed superstructure derives from, drawn at 4mm :1 ft First stage Pairs of tender frame (upper) and loco frame (lower) blanks were sweated together and a pair of coupling rod blanks were soldered to the latter. The wheel centres were carefully marked out on the rods and drilled right through to crank pin size with a pin chuck. A drill press would have made life easier but at least I didn't break any bits. The next stage I then separated the rods from the loco frames and opened out the holes to axle diameter (1.5mm) with a tapered broach, I also drilled a couple of holes beyond the ends of the frames for temporary bolting through tube spacers to aid assembly. I used a black spirit marker to increase contrast and marked-out the frame profiles. Then it was down to marking-out the intermediate gear centre, using the gear meshing tool, drilling through and the tedious business of cutting out the frames with a piecing saw and dental burrs in the Dremel. The frames After final shaping of the frames, the pairs were separated and joined using soldered gapped double-sided PCB spacers.This is where the tube spacers and bolts come in useful as everything can be trued-up before soldering. The tender chassis is relatively simple as the wheels will eventually be permanently fixed in their muffs but the loco chassis has a separate keeper plate, made in the same way as the frames. The bogie is a separate assembly from the excellent N-Brass range. The worm is mounted in a simple cut tube bearing on a block of brass, to be fixed to an upstand on one of the frames. The intermediate gear is on a sleeved muff housing short split axles to preserve the frame insulation More to follow. John Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted April 13, 2013 RMweb Gold Share Posted April 13, 2013 A good lesson on chassis building there. The jump from the basic drilled frame to to all the parts laid out is a bit 'blue peter here's one I made earlier' a fair bit of work between those two shots. Don Link to post Share on other sites More sharing options...
JohnBS Posted April 13, 2013 Author Share Posted April 13, 2013 A good lesson on chassis building there. The jump from the basic drilled frame to to all the parts laid out is a bit 'blue peter here's one I made earlier' a fair bit of work between those two shots. Don Sorry, Don, I didn't take any further stage photos. Happy to post further details of the construction as it stands.John Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted April 13, 2013 RMweb Gold Share Posted April 13, 2013 That quite ok John I was just interested to see how you went about it. It is surprising what you can learn from how others do the job. Don Link to post Share on other sites More sharing options...
RMweb Premium Kris Posted April 13, 2013 RMweb Premium Share Posted April 13, 2013 Very nice John. Do you intend to blacken the wheels or paint them? Link to post Share on other sites More sharing options...
JohnBS Posted April 13, 2013 Author Share Posted April 13, 2013 Kris, Thank you. As to the wheels, probably both!! - but that will be a few sessions down the road. John Link to post Share on other sites More sharing options...
JohnBS Posted April 16, 2013 Author Share Posted April 16, 2013 Hi all, The 3.500 gal tender is now almost good to go - Shapeways software reckon that it is printable so it should be with them in the next couple of days - see renderings below: The top of the tanks and the coal space is to be a separate printng - if it is omitted : Space for a motor op to a maximum of a Mashima 1215 and flywheel (gold preferred but brass if that is all you can afford) BTW the tank between the frames is also a separate printing, Link to post Share on other sites More sharing options...
RMweb Gold queensquare Posted April 16, 2013 RMweb Gold Share Posted April 16, 2013 Superb stuff John. I didn't realise you utilised a keeper plate on your locos. Is that your standard practice? Jerry Link to post Share on other sites More sharing options...
JohnBS Posted April 16, 2013 Author Share Posted April 16, 2013 Jerry, Yep, I like to use some form of keeper plate for locos. I find it very difficult to resolve all the fettling necessary for wheel back-to-back, quartering, crank pin clearances and rods without lots of handling. When that gets to a free rolling chassis, I like to be able to strip everything out except the driven axle and intermediate gears, then carefully mesh the worm and power-up with a mini-drill and polish up with toothpaste (tip from a well-known dental practitioner, I think). This also means that I can paint or blacken the frames and wheels independently, after all the mechanically tweaking has been completed. As you can see, I don't usually bother with a keeper plate for the tender as things are so much simpler. How was creepy Crawley? Melksham was a great success in that I managed to source all the materials and bits I needed, and succumbed to a second 2884, from Dave. John Link to post Share on other sites More sharing options...
RMweb Gold queensquare Posted April 17, 2013 RMweb Gold Share Posted April 17, 2013 Jerry, How was creepy Crawley? Melksham was a great success in that I managed to source all the materials and bits I needed, and succumbed to a second 2884, from Dave. John Thanks for that. Must admit I never use a keeper plate but I can see the logic. My predominantly MR stuff has a lot less to fettle being, in the main, inside motion. Crawley went very well, once youngest son drove up with the cassettes for Highbury. I had managed to perform the same trick you pulled off with the Ashburton stock box at Aylesbury a couple of years ago!! Jerry Link to post Share on other sites More sharing options...
Rabs Posted April 18, 2013 Share Posted April 18, 2013 Fascinating project, thank you for sharing your progress. For the uninitiated of us who want to learn: what do you mean by a keeper plate? Link to post Share on other sites More sharing options...
JohnBS Posted April 18, 2013 Author Share Posted April 18, 2013 Rabs, In general terms, a keeper plate is something to keep the wheels from falling out of slots in the frames. Often it can be just a simple piece of metal but, for the split frame construction that I am using, something more complicated is needed. Firstly, the insulating axle muffs have to be accommodated and secondly, the left and right sides must be electrically isolated from each other. In the bottom picture of post #75, you can see that the frames (shiny bit of brass at the top) have three slots in the lower edge for the axles. The keeper plate is the lower bit and has some indication of springing and compensating beams included. After quartering the wheels in insulating axle muffs, they can be fitted and the keeper plate attached to the frames with a couple of small bolts. I will post a couple more photos which may explain this a bit more clearly. Hope that this helps, John Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted April 18, 2013 RMweb Gold Share Posted April 18, 2013 If you fit some bearing to the axles the keeper plate only needs to hold the bearing up and doesn't have to deal with the wheels rotating in which case a bit of pcb might suffice. John's solution where the keeper plate is more sophisticated and also carries additional details rather more than the original keeperplate idea. Quite impressed John but then I was most impressed with the Bulldog. Don Link to post Share on other sites More sharing options...
JohnBS Posted April 21, 2013 Author Share Posted April 21, 2013 Hi all, Progress on the chassis. The easy bit - the tender frames The two frames are 20-thou (0.5mm) brass, joined with double-sided PCB, suitable gapped to provide insulation. The heavy wires at the top are the motor connections, they double as motor mounts, being thick enough to take the toque. The thin wires at the left hand end of the frames are for electrical continuity from the loco. They simply rub on the inside of the loco frames so no need for difficult mini-plugs or for fixed soldered wires. The frames with wheels The split-axle wheel sets are inserted into plastic muffs Note the holes in the frames for future brake rigging. View of underside. For the tender, I used lengths of plastic tube of 1.5mm bore. When all is finished and the frames and wheels are painted, I will introduce a little CA adhesive to the transverse holes drilled through each of the muffs to fix the half axles. Phosphor-bronze wire springs pressing down on to the first and second axles are visible inside the frames. With vertically slotted axle holes in the frame, these provide a degree of suspension and improve electrical pick-up. Coming soon, the loco frames. John Link to post Share on other sites More sharing options...
JohnBS Posted April 22, 2013 Author Share Posted April 22, 2013 Hi all, Moving on to the loco chassis components. The left hand side of the frames, showing the axle slots, the intermediate reduction gear pivot and the mounting holes for the worm assembly. complete with a bit of masking tape as insulation The worm assembly, a simple lump of 1mm thick brass plate with a length of 1.5mm bore tube soldered to it. The tube was carefully reamed out to be a rotating fit to a shaft of approx 1.6mm dia pivot steel. Then the tube was cut to form a front and back bearing and the 1.mm brass plate was drilled and ground to provde space for the worm. The worm itself was similarly reamed out, but this time to be an interference fit on the shaft. Then it was a blacksmith job (small hammer) to assemble the worm and pivot in the bearing. The excess length of shaft was ground off. a slotted section of tube soldered to the rear for the cardan shaft and a loose brass sleeve added. The brass plate was insulated with a thin piece of double-sided PCB and tapped to take a pair of countersunk 12 BA set screws. The keeper plate, basically another piece of split frame construction with a simple profile of compensating beams and springs. The ash pan is of thin PCB The ash pan weight. I had enough space to put in a 5mm wide slug of copper tungsten beneth the axles and gears - always useful to add weight, particularly at the rear of a 4-6-0 Next, the assembly of the parts. John Link to post Share on other sites More sharing options...
D869 Posted April 22, 2013 Share Posted April 22, 2013 Good to see this progressing John. As I'm pondering doing something similar, I'm curious about the tender sides - how thick (thin) are they? Do you think they will be strong enough? Regards, Andy Link to post Share on other sites More sharing options...
JohnBS Posted April 22, 2013 Author Share Posted April 22, 2013 Andy, The loco boiler/sokebox/firebox and other main structural wall thicknesses were 1.0mm and are really robust in 2mm scale, such that I was happy not just to drill them with a pin chuck but also, to Dremel out (with dental burrs) for gear clearances. The tender is similarly a 1.0mm thick main structural box, with tapered coal sheets, etc. As to your final question, my answer is that I sincerely hope so. I am expecting the results from Shapeways in the next day or so and will post some photos straight away. John Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted April 23, 2013 RMweb Premium Share Posted April 23, 2013 Very interested to see you use the slotted axle/keeper plate chassis construction. Do you allow a bit of downward axle movement in the loco chassis to aid electrical pickup as with the tender? Izzy Link to post Share on other sites More sharing options...
JohnBS Posted April 23, 2013 Author Share Posted April 23, 2013 Izzy, I have only deliberately allowed vertical movement of the front and middle tender axles - after all, with a tender-mounted motor, it is the tender which is crucial for current collection. The loco has one-piece coupling rods and the driving wheel axles are (or should be) just a rotating fit in the slots. With any luck, at least three driving wheels will be in touch with the track at any time, to add to the six tender wheels. John Link to post Share on other sites More sharing options...
Atso Posted April 23, 2013 Share Posted April 23, 2013 Hi John, Fantastic progress there with the Saint! It is very interesting to read and see how you've gone about building an N gauge chassis (sorry I know its 2mm but you do use N gauge track!) and this is something I might well try later using your example! Re the tender body. Be careful with largish unsupported areas in FUD, especially when there is the potential for some heat to be generated near the print. The part may experience some warping (not a problem at 1mm+ thicknesses but less than that could be a problem). I've made a few FUD bodies which all use a wall thickness of 1mm without problem. My J50 body however is only 0.75mm wall thickness and suffered terribly from minor warping which interfered with the coupling rods. This was solved by backing the FUD with a shaped piece of 0.25mm nickel silver sheet. I've had no further warping problems since. Hope this helps and I'm looking forward to seeing more! Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted April 23, 2013 RMweb Gold Share Posted April 23, 2013 This is a great thread John so many useful ideas for chassis construction. Don Link to post Share on other sites More sharing options...
JohnBS Posted April 23, 2013 Author Share Posted April 23, 2013 Hi all, Hot off the press (well, it is called 3D printing) is the 3500 gal tender. Printed by Shapeways in FUD, completed in Eindhoven on Monday at 10.41 am, shipped via Cologne, Castle Donnington and Bristol; and arrived in Somerset today at about 1:30 pm. Straight out of the box -- A quick clean and misting with grey primer - no sanding. The front is the roughest bit - luckily as that is the least visible and easiest remedied. The separate coal space insert fits!! Various scratch marks are where I grabbed the bits with tweezers before the paint was dry, in my haste to get them photographed. Underside - zoom in and count the rivets and spring leaves The tank is a separate printing, either to clip between the frames or fixed to the chassis. Chassis construction postings will resume as soon as possible. John Link to post Share on other sites More sharing options...
D869 Posted April 24, 2013 Share Posted April 24, 2013 Glad to see this has come out well John. Very encouraging... although it will be a while before I do anything in this direction - it looks like a lot of work at the computer before getting to this stage and I may figure out another way to source a decent model of a 4000 gal Collett tender before then. Regards, Andy Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted April 24, 2013 RMweb Premium Share Posted April 24, 2013 Izzy, I have only deliberately allowed vertical movement of the front and middle tender axles - after all, with a tender-mounted motor, it is the tender which is crucial for current collection. The loco has one-piece coupling rods and the driving wheel axles are (or should be) just a rotating fit in the slots. With any luck, at least three driving wheels will be in touch with the track at any time, to add to the six tender wheels. John Thank you John, that's quite logical. I was interested to learn you generally use this construction, as having played with/rebuilt several times some 2mm SA etched chassis recently I have now concluded that a slotted axle chassis even without spring pickups or bearings seems to provide better/more reliable current collection. Izzy Link to post Share on other sites More sharing options...
-missy- Posted April 24, 2013 Share Posted April 24, 2013 That tender looks really good John. Fingers crossed you are planning on selling them onto other members? Its seriously asking for an etched chassis to go with it, hmmmm... It will also be interesting to see how the motor fits into it as well, what are your plans? Missy Link to post Share on other sites More sharing options...
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