Mark Posted February 14, 2016 Share Posted February 14, 2016 Here some images of a couple of Malcolm Mitchell King Kits I have working on intermittently over the last year or so. The idea is to build them in P4 with the Split Axle current collection with full springing. I used Dave Bradwell springing units and double sided PCB sandwiched between them and the frames to keep everything electrically neutral. I used a Finney Tender for both with some extra bits added to accommodate the motor and some etches for the spring carriers. I have had to do replacement etches for the cab sides, roof and smoke box because I felt the rivet detail was a little over etched and prone to vanish under paint. The boiler assembly has been made removable. I have also made new turnings for the smoke box door and front. The kit includes the fire iron tunnel but not the top that fills the gap between the fire box and outside edge so this had to be fabricated to fit. The bogie has almost no clearance for the outside of the leading axle even after thinning it down so I got a new one etched with a half etch recess to provide a little more clearance. I also took the opportunity last summer to go and measure the coupling rods at Didcot and then machined two sets of replacement rods. Hopefully I can get the majority of it completed before the Hattons version appears. Photo's below: Coupling Rods Locos Pipework on front frame extension Smokebox Fire Iron Tunnel Tender motor and mount. The motor sits on a rubber pad and will be strapped down to the same bolts that hold the mount. The gearbox is a High Level Tender Riser. Drive shaft from front of tender under footplate. Drive shaft enters loco under cab and runs through a universal joint into a shaft. Forward of the shaft which runs through a machined block, another universal joint carries the torque to the middle axle. This keeps the lateral movement of the shaft between the loco and tender to a minimum. The drive shafts are Branchlines. Home made gearbox which will use a set of Ultrascale gears. Hornblock assembly shows clearly PCB under the hornblock. Chassis frames. Note I used a Chassis Squared Jig to accurately locate the hornblocks. The dots on the brass indicate which bearing belongs to which guide. 3/4 view still some tweaks to make to the body yet. None of the cab parts are not soldered together yet and the boiler sections are still separate at this stage. Regards Mark Humphrys Link to post Share on other sites More sharing options...
Guest Lyonesse Posted February 14, 2016 Share Posted February 14, 2016 Very neat work. I especially like the representation of the pipe work in front of the outside cylinders. The mogul in the background looks special too. Surprised you didn't feel there was enough room in the boiler and firebox to keep the drive system entirely in the loco. Or is the loco itself full of lead? Link to post Share on other sites More sharing options...
Mark Posted February 14, 2016 Author Share Posted February 14, 2016 Very neat work. I especially like the representation of the pipe work in front of the outside cylinders. The mogul in the background looks special too. Surprised you didn't feel there was enough room in the boiler and firebox to keep the drive system entirely in the loco. Or is the loco itself full of lead? Thanks for the compliments. I once built a 28xx many years ago and put the motor in the boiler and the gearbox in the firebox. It wouldn't pull anything so ever since then I like to get as much weight in the loco as possible. This helps with the springs as well, but the plan is to fill the entire space above the drivers with lead. The front part of the boiler and firebox will remain empty so as not to make it front heavy. Trial and error will dictate the final position for the weight. Regards Mark Humphrys Link to post Share on other sites More sharing options...
Guest Lyonesse Posted February 14, 2016 Share Posted February 14, 2016 And also --- just curious, you understand --- is it really quicker and better to get parts etched for a single loco, or pair of locos, rather than cut them out of sheet metal? At least if you cut the parts yourself you can use a decent grade of nickel silver and get a properly finished edge. Link to post Share on other sites More sharing options...
RMweb Premium ullypug Posted February 14, 2016 RMweb Premium Share Posted February 14, 2016 Very nice indeed Mark. Like the mogul on the bench too! Link to post Share on other sites More sharing options...
Nimbus Posted February 14, 2016 Share Posted February 14, 2016 I'm interested to know how you machined the coupling rods, and particularly the workholding technique. They do look very crisp! The Nim. Link to post Share on other sites More sharing options...
Mark Posted February 14, 2016 Author Share Posted February 14, 2016 And also --- just curious, you understand --- is it really quicker and better to get parts etched for a single loco, or pair of locos, rather than cut them out of sheet metal? At least if you cut the parts yourself you can use a decent grade of nickel silver and get a properly finished edge. I had several other things on the sheet at the same time. Also to get a consistent appearance etching was the best solution. I have included a recess in the window frame on the outside for glazing onto which I have a outer frame to get a better glazing effect that putting the glazing in the cab. Also if I scratch built the sides, I would have had to solder on separate beading along the front edge, so all in all etching was a lot easier and more accurate. Regards Mark Humphrys Link to post Share on other sites More sharing options...
Quarryscapes Posted February 14, 2016 Share Posted February 14, 2016 That's some lovely machining on the rods! Might use that as justification for upgrading my milling facilities Link to post Share on other sites More sharing options...
Mark Posted February 14, 2016 Author Share Posted February 14, 2016 I'm interested to know how you machined the coupling rods, and particularly the workholding technique. They do look very crisp! The Nim. There was an article in MRJ several years ago on CNC machining where the author used araldite to bond the metal to a piece of MDF. I tried this and it worked fine. I made sure I put two reference holes in the sheet when I started to ensure the front and back profiles were in register and then started by CNC machining the profile on the back. Once this was done, I removed the Nickel Silver sheet from the MDF using a blow torch being careful not to overheat the metal and the differential expansion results in a clean break of the bond. I had to flatten the metal again before I could glue it down the other way up as it curved as a result of the other layer being machined away. I then set it back on the CNC machine and used my reference holes to datum everything and then formed the profile on the front. In both cases this was done using a 6mm end mill using small steps to define the profile. This allowed me to produced different radii curves without having to change the tool if I had used a bull nose cutter. After that it was just a case of slot drilling the profile after having drilled the holes for the crank pins. I was writing the CNC code as I went and making sure that I eliminated all the backlash by compensating in the code. Once the profile for all the rods had been cut I heated then again to remove them from the MDF. After this it was just a case of slotting the forked joint. I have a Sherline CNC machine, which with a bit of care and planning can produce some quite impressive results. Once the rods were removed it was just a case of gently cleaning them up. I removed the steps from the profile machining in situ on the machine. Regards Mark Humphrys Link to post Share on other sites More sharing options...
Mike G Posted February 14, 2016 Share Posted February 14, 2016 The word 'amazing' is used far too frequently, the word I'd use for this type of work is extraordinary! Really raising the bar, Mark. More power to you. Can't wait to see further updates. Mike Link to post Share on other sites More sharing options...
Horsetan Posted February 14, 2016 Share Posted February 14, 2016 .....3/4 view still some tweaks to make to the body yet. None of the cab parts are not soldered together yet and the boiler sections are still separate at this stage. DSC01483_reduced.jpg Is that a Springside chimney? If it is, they haven't produced any in years. Same goes for their safety valves - still listed, but permanently unavailable. Link to post Share on other sites More sharing options...
Mark Posted February 15, 2016 Author Share Posted February 15, 2016 Is that a Springside chimney? If it is, they haven't produced any in years. Same goes for their safety valves - still listed, but permanently unavailable. Yes it is the Sprinside chimney. I managed to get another one last year from Ebay for the other King. I will probably replace the copper cap as it is plated and the plating is coming away, so I may turn up a replacement from some copper bar rather than mess around trying to plate copper plate it. Regards Mark Humphrys Link to post Share on other sites More sharing options...
Horsetan Posted February 15, 2016 Share Posted February 15, 2016 Yes it is the Sprinside chimney. I managed to get another one last year from Ebay for the other King. I will probably replace the copper cap as it is plated and the plating is coming away, .... Yes, I remember looking at that eBay one as well. Link to post Share on other sites More sharing options...
Guest Lyonesse Posted February 15, 2016 Share Posted February 15, 2016 I don't know about on a whitemetal/brass hybrid, but it is fairly easy to plate a brass chimney. Link to post Share on other sites More sharing options...
Loconuts Posted February 16, 2016 Share Posted February 16, 2016 I don't know about on a whitemetal/brass hybrid, but it is fairly easy to plate a brass chimney. I plated a whitemetal chimney several years ago and it worked well. However turning a copper cap up from copper is always the best if you can afford the copper. Loconuts Link to post Share on other sites More sharing options...
Mike G Posted February 17, 2016 Share Posted February 17, 2016 Mark Going back to the photo of the tender - showing the motor and gearbox - you've got a rubber seat but what have you designed for the seating to rest on? Is that something you've done or is it commercially available. I have an 8f in the pipeline and these pics of yours may have pushed me over the edge for tender driven engines. Also... The coupling rods are exceptional I dare say they're scale, I'm just wondering how you're going to get room behind the crossheads? regards Mike Link to post Share on other sites More sharing options...
Mark Posted February 17, 2016 Author Share Posted February 17, 2016 Mark Going back to the photo of the tender - showing the motor and gearbox - you've got a rubber seat but what have you designed for the seating to rest on? Is that something you've done or is it commercially available. I have an 8f in the pipeline and these pics of yours may have pushed me over the edge for tender driven engines. Also... The coupling rods are exceptional I dare say they're scale, I'm just wondering how you're going to get room behind the crossheads? regards Mike Hi Mike, The rubber is basically a piece of inner tube between the motor and the metal plate. The motor will have a strap which will be bolted down to the two bolts on either side of the plate. I will probably put another strip of rubber between the strap and the motor before it is clamped up. The idea is that the rubber will primarily damp the vibration from the motor and hopefully stop the tender from becoming a resonance box. The machined coupling rods are actually thinner than the etched rods supplied in the kit, so I don't think there will be any more clearance issues than normal. I noticed on a Castle at Didcot that the front of the crank pin and the back of the crosshead would actually foul if they passed each other, but it seems the crosshead passes the crank pin within the throw of the crank, so the crank pin is either above or below the crosshead but never directly behind it. At the horizontal extremes it is always forward of the crankpin, so the only thing to make sure is that there is enough clearance behind the connecting rod for the crank pin. Regards Mark Humphrys Link to post Share on other sites More sharing options...
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