bertiedog Posted April 17, 2018 Author Share Posted April 17, 2018 (edited) The wheels are here, aren't they small! The castings look good, starting the machining before weekend and in meantime making the counter weights and crankpins etc. Machine by griping the tyre, running as true as the casting allows, then drilling and boring the centre, reversing on a mandrill, and fixing with superglue and pressure from a live centre with a cup. The tyre is turned flat.and the root radius machined in one op,, then the wheel is removed after machining the flange and front face, a spot of heat breaks the glue. Each wheel in turn, and then grip on flat tyre to machine the back, with recess to expose the spokes. Then all are re-mounted one by one on the mandrill and the taper is cut on locked settings for all four, Then all are cleaned around the back of the spokes. Whilst on the mandrill the tyre can be polished to high finish, and by gripping on the flange the boss can be finished with a satin surface. The back of the wheel is not flat, a raised central boss is know left to prevent running on the frames. Axles are made to just the bored holes and pressed on with loctite..... As the wheels are cast iron, slow lathe speed should be used with carbide tools or inserts. i do not turn between centres, it requires pre fitted drop in bearings and this method with care gives great accuracy. and ease of assembly and quartering by a simple jig. The vital point is that all wheels must be identical diameter. no tolerances. the same or the wheels will not pull. Stephen Edited April 18, 2018 by bertiedog Link to post Share on other sites More sharing options...
bertiedog Posted April 18, 2018 Author Share Posted April 18, 2018 The main outer frames are all cut ot and reduced on belt sander to size as a pair, and the final details will be filed to shape. The axle holes are drilled to size, 3/16th, 4.7625, but then opened up to allow for the floating action of the axles at 2mm bigger at 6.7625, in practice the drill was 3/16th and 6.7mm The inner frame is drilled 6.7 and the bearing inserted after drilling just under 3/16 and teaming to 3/26th size. The outer diameter of the bearing is 8mm, non critical, and it has a step machined on one end to insert into the 6.7 hole, leaving the outside flush and the rest inside the frame. This leaves a gap for the gearbox. All sizes are nominal only critical one are reamed, and I use both mm and imperial to give a bigger choice of drills. Whilst on the bench the coupling rod blanks, (as a pair) are spot drilled with the 3/16tth drill to allow further drilling later to crank pin size, usually I use 3mm in O gauge.. 3mm crankpins can be drilled and tapped 6Ba and take a washer and nut to retain the rods. The bolts used can be reduced in size across the head to 8Ba size. It gives a strong reliable crankpin assembly. The washers are made in the lathe from brass bar. The side coupling rods are made from nickel silver., or mild steel. tinned with pure tin solder and wiped away whilst hot, leaving a rust proof and corrosion proof, finish. Next issue is the bogie, plain box and bolster type, with axleboxes and springs. Each profile milled out on a bar and separated into four blanks in the lathe. The outer axle box face and the springs are silver soldered together for strength. the springs are turned grooves on a plate, and cut into four, with the spare spring ends filed away. the top spring has its end split to take a hanger rod, again soldered on solid. The axles boxes will be kept slim to aid clearances. A bronze bearing for the axle stub will be drilled in the lathe and soldered into the back of the axle box 2mm axle stub on 3/16th axles. The box of the bogie has a stout bolster bar added across the frames. in 1.2 mm hard brass. This can be drilled and tapped to take centering springs and the bogie pivot hole The hole will slotted to allow side movement and pivoting. the amount measured on assembly and test on curves. Stephen Link to post Share on other sites More sharing options...
N15class Posted April 18, 2018 Share Posted April 18, 2018 (edited) 6BA is a bit large even for 7mm. 12 is fine but most use 10. 6BA would only leave you just over 0.1mm wall with using a 3mm crank pin. any pictures of progress? Edited April 18, 2018 by N15class Link to post Share on other sites More sharing options...
bertiedog Posted April 18, 2018 Author Share Posted April 18, 2018 (edited) The 6ba crankpin bolts are not normal head dimensions, but milled on a rotary table across the flats to reduce the head to just be able to fit on the washer. Or it can be milled to leave a washer formed from the head in Bugatti style. Commercially hex headed bolts in the BA series are available from Model Engineers suppliers in one head down sizes as well, ie a 6 BA with an 8 BA head, but by milling away you can get 9BA head on a 6BA bolt. If the Bugatti method is used the head can be as small as 12BA In the Bugatti style the edge is rounded in the lathe after milling the flats The Bugatti was design not to just reduce size and weight, but to eliminate the washer and make all sizes have just one spanner to fit them all. I usually use the Bugatti on steam engines for boats, but they look good on connecting rods as well. You may have to make a spanner or use a quality adjustable spanner to fit. Also the best tighteners are tool makers clamps The crankpins are 1/8th stock or 3.1750mm and leaves thick enouth wall, and the thread goes in 3mm depth. The crank pin is stainless steel, the bolt is mild steel, the washer if fitted, is made in stainless steel. Stephen. Edited April 18, 2018 by bertiedog 1 Link to post Share on other sites More sharing options...
bertiedog Posted April 18, 2018 Author Share Posted April 18, 2018 (edited) Awaiting arrival of new camera, I can use a phone camera but results are awful. They use flash but it blurs due to camera movement unlike a real true flash. Just not sharp enouth, and I am not buying an Apple just to take better pictures, Phones make calls, cameras make pictures. Edited April 18, 2018 by bertiedog Link to post Share on other sites More sharing options...
bertiedog Posted April 19, 2018 Author Share Posted April 19, 2018 After a rethink, the PC etched pickup mount will not be needed, with the inner frames bottom filled with a machined block of sheet bakelite, 6mm thick, fixed with countersunk 8Ba screws The block will have the spring bolted to it direct, and power taken from one of the bolts via an electric washer. It will need a bit at the rear cut way to fit over the gearbox. The 6mm thick plastic will add to the strength pf the frames. Link to post Share on other sites More sharing options...
bertiedog Posted April 19, 2018 Author Share Posted April 19, 2018 The arrangement of the bakelite block within the inner frame to support the third rail pickups. The suppressor circuit can be added to the other bolt for connections, and earthed to the chassis. Stephen 1 Link to post Share on other sites More sharing options...
bertiedog Posted April 20, 2018 Author Share Posted April 20, 2018 (edited) The build coming along faster than thought, a few templates in card to check fits and the bodywork soldering will be underway over the week end. Got in supplies of 145c solder and 60/40 solder paste from Cupalloy. The chassis mainframes are complete and drilled for frames pacers, also used to take bolts for the body retaining. The inner subframe is also complete with ends but no spacers except the Bakelite bottom block to take the pickups. Still to decide whether brass or copper pipe is best for the boiler barrel. Copper can be awkward to solder to as it soaks up the heat, and risks spreading heat to other joints that could melt. The gears need no modification at all apart from a covering gear case. It will need a small brass cradle made to take the motor to fit the sub frame. Stephen. Edited April 23, 2018 by bertiedog Link to post Share on other sites More sharing options...
bertiedog Posted April 23, 2018 Author Share Posted April 23, 2018 Finalising the chassis by fitting the inner frames in place and fitting the bogie, although the outer bearing details are not ready. With the wheels on, and foot plate level, the size of the bolster pivot over the bogie can be measured, and a PTFE sleeve bearing can be cut out on the lathe. The PTFE is near friction free. Brass could be used as well. The bogie pivot is a turned 4Ba stud bolted to the frame spacer above the pivot point and through the bolster slot on the bogie, which has a coil spring around it to remove any slack above the pivot point. The loco rests its weight on the spacer and bolster, it is not sprung, it does not ride on the spring. A separate straight wire spring will be added to return the bogie to centre running on a straight track section. As the loco is three rail, the bogie is electrically earthed, but to make sure of contact the bogie will have a jumper lead to the loco frame added, all hidden away behind the bogie frame sides. There is a brass cover and gear case to make today as well, which will have the motor mount added as well. The case will be filled with Labelle brasilicon grease. Link to post Share on other sites More sharing options...
bertiedog Posted April 27, 2018 Author Share Posted April 27, 2018 Lots done on an expanding bench full of parts most in finished profile for soldering up into screw together units. The boiler is being made from flat brass as the right size is not made. and the nearest is far too expensive for the short length needed. It will be in 20thou brass and rolled. As several parts have been duplicated as test fits etc. I have decided to make a second model as well, of No35, but in 2 rail fine scale, for myself. It can use the same wheel castings, scale width frames, and no pickups. The wheels on one side will require Tufnol bushes. GOG standards suitable for Peco points. It will have the same pivoting chassis design, but may have a tower type gearbox, and the same motor, but bigger flywheel in the boiler space available. It's just as easy to make the extra parts for two locomotives as one. Most material bought in was more than needed due to minimum order size, or stock sheet size considerations. Stephen 2 Link to post Share on other sites More sharing options...
bertiedog Posted April 29, 2018 Author Share Posted April 29, 2018 Most of the parts are duplicated now, spare wheels made for the bogie. The driving wheels will be ordered tomorrow, cast iron as before, but after drilling & boring the centre hole a bush will be fitted to the larger sized hole, made in reinforced hard grade Bakelite, which can be glued in with epoxy resin. The bush will be flush at the front but stick out about .5mm at the back This provides insulation from the brass mainframes. Only the two wheels will be insulated, the other side picks up power, the bogie returns it to the other rail. This does mean an insulated bogie, the bolster can be made from Tufnol, Bakelite or perspex plastic. The wheel bushes can be done in perspex, but the Bakelite is stronger. The wheel has to be a press fit on the axle, and perspex has too much give in it and can slip on the axle. The axle ends can be rolled against a needle file to micro knurl the surface for the epoxy to grip against. The non-insulated side is a simple press fit with a drop of Loctite for security. the axle end is turned and papered to just fit the hole, then the end is rolled on a file to "raise" the surface and should be a hand pressure fit, the final bond is made by the Loctite. Too slack and it will wobble, too tight and there is no space for the Loctite. A traditional press interference fit could be used, but getting it right needs experience, too tight and the axle can bend or worse the cast iron break. Final quartering is done by twisting before the Loctite sets hard. The side rods for both versions are made from N/S 0gauge track section with silver soldered bushes added at each end, a bit oversized and filed to final profile, before drilling the holes using the frame as a jig. A Tower gearbox is being developed for mine, with helical gears and spur gears, about 40:1 ratio. This should allow the loco to freewheel or run on with the flywheel. Slaters do some crossed helical gears which may suit. The whole geartrain will be enclosed in a full casing in brass, half filled with a grease and oil mix, (LaBelle PTFE plus silicon oil) The three rail version has a simple one stage worm drive. Stephen Link to post Share on other sites More sharing options...
bertiedog Posted April 29, 2018 Author Share Posted April 29, 2018 The Slaters cross helical is 2.9; 1 so freewheeling may not really occur but coasting under light load and low power should be excellent. The spur gears should be about 14:1 total. I will have to work out a set to be smaller in diameter than the drivers and for the middle of the box gear to clear the driving axle. The shafts can be ball raced with sealed races. I can cut the spur gears, but ready made are available quite cheaply. Stephen Link to post Share on other sites More sharing options...
N15class Posted April 30, 2018 Share Posted April 30, 2018 Why after all the machining etc that you are doing. Why make up the coupling rods from rail. Which will always look like rail. Machine the they will look so much better and you can even get the rebate ends correct. Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 The 0 gauge rail is used as it is to hand and the right dimensions once the bullhead profile is removed. It is just a strip of nickel silver, no fluting is required, the side rods are flat faced. The rail section is also better quality NS grade than most strip is. The rail has the bullhead profile removed on a power bench belt sander. The N/S bosses, (from bar stock or castings), are added to the ends with silver solder, which will not show after papering and polishing. If fluting on the outside is needed, I run a 2 thou slitting saw into the profile top and bottom and bend and form the end of the fluting before the solder is applied. which fills the gaps from the saw and forms a neat fillet with the boss blank before further machining and filing. Quite often when N/S was not available in the past I used mild steel and the very carefully tinned the lot with pure tin solder. This was heated up afterwards and "wiped" with damp paper towels to remove any excess and leave a good "plated" surface. Prevents any rust. Stainless steel can be used but machining is more difficult, it is hard and wears files out. The N/S castings are home cast from rail scraps, by an ordinary gas torch. The mould is hard wood which is charred first to prevent too much burning, or into a plaster of Paris mould. They are cast oversize to allow full machining to size. Stephen Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 Back to the sisters, No 34 and No 35, the new set of four cast iron wheel castings are ordered from Walshall Industries tonight. The same 4-foot driver with the crank pin through the spoke. The counterweights are made from brass discs, cut into segments and fitted with Epoxy glue. The trailing bogie wheels are made from stainless steel bar machined in the lathe. I never use any wheel material which will rust. The axles can be mild steel or silver steel, or stainless steel. The bogie axles will be fully painted as well on the bogie wheels faces. in Indian red.colour. Stephen Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 As can be seen from the photo the rods are smaller than rail section and the fillet on to the boss would be formed from the solder or filed from the boss material. The coupling rod would be about 2 1/2 inches thick and about 5 in high, slightly fish-bellied form in profile.. About 1.5mm by about 3.5mm in the middle of the rod fishbelly.in model sizes, so well within machining from the Peco rail section. To save filing down 00 rails for the can edges I have ordered in some fine N/S strip. and also strip for brake rods etc. Stephen. 1 Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 Just cut out, sanded flat the rail section, and soldered on the bosses for the coupling rod ends. The shape of the ends can now be milled, after the bearing holes are drilled using the chassis as guide jig. A steel pin is mounted vertically on the mill in the machine vice, to match the bearing size, and a carbide burr sided end mill of 2.5mm diameter is set in line with the pin. The table is advanced towards the pin with the rod on it and a rotary movement of the rod end is allowed as the tool touches the rod end. The rod is held firmly by the other end and moved in an arc to allow machining to take place. The cuts are kept small. If there is a lubricator on top of the boss the cut is halted and skips the next part leaving the lubricator base. The cutting bit speed should be high, the cuts slight each time or snatching can occur. The whole cutting could be set up on a rotary table but this takes far more time. After the basic cutting, the final shape is finished with needle files, all de-burred, and then fine emery paper and then wire brushed and finished with fine grade scotchbrite foam abrasive pads. The top of the rod boss left for the lubricator can be drilled to take a brass lubricator cap, retained with loctite. The front of each boss can counter drilled into the boss to the thickness of the crankpin head. With this loco the crankpin head can be plain with two pin holes for a pinhead spanner. This duplicates the appearance of the real crank pin. The counter drilling is done with a slot drill to get the hole with a square bottom, as an ordinary drill leaves a coned cut matching the drill bit ground tip. 2 Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 The crankpins are made of stainless steel and the end is threaded 8ba or 7ba to match the hole in the cast iron wheel boss. If no milling machine or lathe then a hex headed head can be used, filed down to half thickness, and no counter-boring the holes. All the shaping of the ends of the rods can be done by hand, using a filing button on a pin to match the coupling rod hole. The filing button is made from silver steel and hardened fully to resist the files. The diameter matches to the final required diameter of the rod boss. Stephen 1 Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 (edited) Sets of rods done for both locos, just need finishing applied. They fit dummy axles through the frames with ends turned to match the crankpin diameter, so as long as all the crank throws are correct, the wheels, once finished for both, should quarter100%. The bearings are on the inner frame unit, and the holes of the outer frame are enlarged to an oval to allow for the movement as the inner chassis pivots. The pivot position is halfway between the wheels at the top of the chassis. The pivots are 8ba bolts with washers to space the inner and outer frame from rubbing. The nut is loctited in place after assembly. Standing on the track the inner subframe is invisible. Moving on to the bogies next. one insulated. one plain Making a brass block profile bar of the axleboxes, so that the individual boxes are sawn off the blank. Details are added with solder. The blank is machined in the milling machine as a solid block. The bearing holes can be added before sawing up, and each axle box can have the end cover soldered on to cover the hole. The axle stub can fit direct or each hole counterbored to take a ball race. The whole side frame can be attached to the bolster bar by an 8ba bolt and left slack to allow a small movement. The ends of the bogie side plates are joined with a .5mm brass wire, which will flex a bit allowing all four wheels to be firmly on the track. Stephen Edited April 30, 2018 by bertiedog Link to post Share on other sites More sharing options...
bgman Posted April 30, 2018 Share Posted April 30, 2018 Whilst I am enjoying your commentary Stephen will you be able to post any photographs of this build in the near future ? Regards Grahame Link to post Share on other sites More sharing options...
bertiedog Posted April 30, 2018 Author Share Posted April 30, 2018 Saving for a new camera at present should have one soon. Stephen. Link to post Share on other sites More sharing options...
bertiedog Posted May 2, 2018 Author Share Posted May 2, 2018 Mass production of the bogie parts underway on the milling machine, then the lathe to part off each item. The bar for the wheels is stainless steel at 25mm to machine to 20mm. They are disc wheels with no spokes and a ring of rivets on the outer face. A recess can be left to take a brass ring with embossed rivet heads, rather than drilling the wheel in a pattern. The axles are 3/16th, with 2mm stub ends. One set is solid, one set is fitted on two wheels with insulation bushes made in Tufnol. Bit more bodywork assembled, only the boiler section to roll and fit. The second motor has arrived, The castings for the wheels are due soon. Stephen Link to post Share on other sites More sharing options...
RMweb Premium Michael Edge Posted May 2, 2018 RMweb Premium Share Posted May 2, 2018 The bogie wheels were Mansell type with wooden centres, the ring of "rivets" is the bolt heads which held the wheel together. Link to post Share on other sites More sharing options...
bertiedog Posted May 20, 2018 Author Share Posted May 20, 2018 Even in 7mm the Bolt heads are not going to look much different to an impressed rivet on a brass ring. A one-inch hex head would be .6 mm approx., far too small to do as a hex nut or bolt. The iron wheel castings are all done, just waiting for balance weights in brass sheet to be glued on with epoxy glue and filler in the gaps. The trailing wheels are stainless steel bar turned in the lathe. Stephen Link to post Share on other sites More sharing options...
bertiedog Posted July 16, 2018 Author Share Posted July 16, 2018 Due mainly to ill health the 3 rail version is dropped and work is being resumed on the two rail No 34 as I get better. Most parts are made so just assembly and insulating the wheels to do next. Stephen. Link to post Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now