Usually my conversions assumes that the loco is in good running order, many Mainline locos are not, even if they have had little use since new, this one had many faults so I have written up all the issues. If you are lucky and have a sound loco then just the motor mofifications and the final part of this tale is all you need. This one was bought used from Hattons some years ago, unfortunately it had suffered from Mazak rot, although not visibly distorted it had become brittle. This embrittlement was not a one off, as such this loco chassis can be a difficult one to convert due to its age and embodies most of the grief one can have when converting a Mainline loco. Motor fixing screw lug and idler stub axles were both brittle and disintegrated. This one is not for the feint hearted or sane person to convert and became more of a restoration project than just a DCC upgrade. I have split this task into parts Dismantling and assessing what needs to be fixed or restored. Creating new stub axles for the idler gears Decoder installation, testing and summary Part 1 - Dismantling and assessing what needs to be fixed or restored Outlne of Work Required Ideally, most of the work is to dismantle this complicated assembly of a loco chassis, make minor modification to the motor, modify the chassis to fit a decoder and re-assemble it all again. First Attempt On my first attempt by just loosening screws to ease out the motor one of the motor support lugs broke off. But worse was to come, dismantling further I found that two stub axles supporting the idler gears were broken effectivey writing-off the chassis. It appears that this chassis had suffered the dreaded 'Mazak Rot' As luck would have it I came across a used wreck on eBay which looked at though it had been dropped nose first and all that was really of use was the chassis and motor, which was all I needed. So in a moment of madness I bought it, not exactly cheap but okay. So on with the work. Second Attempt This time in more detail. Remove body, retained by screws through each end of the baseplate, body can be a tight fit near the middle drivers due to burrs on the cast chassis fouling the inside of the boiler moulding. Release the cylinders from the chassis, they are a push fit in place but requires care to remove them without damage. There are plastic shims between the cylinders and the block they are mounted on, one each side, They appear to provide a flat bearing surface for the pistons, shown more clearly in second image on. Remove baseplate. Remove the driving wheels, coupling rods and valve gear as one assembly, taking care not to lose the two small springs loosely fitted in the chassis and bear against the centre driving axle. Carefully remove these springs and place somewhere safe. The shims. Remove the single cross head screw that holds the two lower parts of the chassis together. Remove the 2 screws that retain the motor to the left hand chassis half. Loosen the two large screws on top of the chassis. With the chassis laid on its right hand side the left half can be eased off leaving the motor and gears in place, the two chassis parts may be difficult to part due to flaring of the end of the tube which retains the lower half of the chassis together. Once apart it could be seen that the plastic cylinder from which the screw which holds the two lower parts of the chasssis together has flared out where the screw was tightened into it. This results in one of two options depending on the state of this part. If the head is still square and the tube not split then the flared edge can be skimmed off before refitting. Or as with this one the square end has partly broken up so replacing may be a better option, see how it sound it is on re-assembly, if poor I will print a new part. The large metal block which the cylinders were mounted on will also be freed. Oh dear! On removing the chassis half the lower idler gear fell out of the chassis with its spindle, it's spindle had crumbled adrift from the chassis just like the first one. I had this problem with a Class 03 conversion too which meant fitting a metal axle into the chassis, I have not got the details of how I did that but it was relatively straightforward. Before I do that the motor can be lifted out after removing the screws on the right hand chassis part and modified. As I lifted out the motor the lug which broke on the first chassis just fell away. So two of these chassis have failed in succession, both have shed a motor support lug and the lower idler stub axle. Lower Idler Stub Axle As the idler axle is part of the cast chassis, it is cast with a slight a taper by necessity of the casting process, the hole in the idler gear is similarly tapered. Possible options, all requiring a hole drilled in the chassis through which to insert the new stub axle. Machined or printed tapered axle, push or screw fit into the chassis Parallel sided axle made from brass rod or tube, push fit into the chassis Parts starting off as screws with turned down shanks could be screwed into the chassis. Parallel sided axles would also require the opening out of the idler gear bore to accept it for true running. The length of the new lower stub axle must not exceed the thickness of the lower idler gear otherwise it would foul the upper idler gear. Upper Idler Stub Axle At first glance this looked okay and is firm, however closer examination with an eye-glass reveals it has multiple hairline cracks along its length. The image below shows the two crumbling chassis halves. The upper one is my original, bought online from Hattons a few years ago, and the lower (donor) one which was bought second hand via eBay. Both were as described, the sellers were lucky that they sold them when they did. So I have a time bomb waiting to go off on the second chassis, what I will do is measure the cracked upper axle stub before it crumbles away completely. The upper idler gear wobbles freely on what little axle stub there is, i.e. the smaller diameter part, the lower thicker part is just a support pillar. What to do next? Chassis #1 Flatten, centre locate, drill 1.8mm (to match gear bore diameter), spot through to other half. Rot half difficult to drill, gritty, knocks driil alignment, otherside easy and smooth. Did not need to spot through for lower idler as larger upper idler is in the way. Problem The position of the hole to fit a new upper stub axle is too far out of position to use so I need to offset the axle to the hole in the chassis, a 3D printer job as to machine up a part is rather too much for my skill set. The design and development of the idler stub axles using 3D printing can be found in Part 2, in the 3D Printing Projects forum. If the details are of no interest, just skip on to Part 3 below.
DCC Loco Conversions - 53 - Mainline 43xx Mogul 1978 - Part 3.1 Replacement Stub Axles Printed. CAD Drawing The result of the final printing is difficult to photograph, so here is the prototype part in a bright colour but in a material (PLA) which is not tough enough for actual use. The slotted sector allows the position of the stub axle to be more precisely set and is locked in position by a 1 mm self tapping screw. Service parts printed in a black nylon. The upper idler gear was a little too stiff on the stub axle but some Labelle106 PTFE grease and some low speed running changed it to a good running fit. This grease was also applied to the lower stub axle. Motor Modification Very Important - Both brushes must be isolated from track power otherwise the decoder is likely to be destroyed. With the motor converted according to article 51, Mainline Class 03 & 43xx Mogul Motor, attention is turned to fitting a decoder. As I already have a modified motor from the first attempt I will use that. Re-assembly Re-assembled chassis, reverse of dismantling. But in a moment of clumsiness while DC testing the loco hits floor, dangling momentarily by test leads attached to the brush arms which bend and cause the brushes, springs and a metal brush holder to fly off in all directions, grrrr .... Can't find the brush holder and one brush spring is damaged, got spares, but want to find the ring first, meanwhile continue with the donor loco motor. Also the suspect gear tube on the drivers split completely, so replaced wheel set with that from the donor loco whose tubes and wheels are in better condition. However one driver started to slip on the geared tube even though no splits or cracks were present, with the quartering re-set spots of Deluxe Materials Hot (AD43), a thin penetrating quick setting cyano glue was applied which has proven to be quite effective. I find it easier to use this than applying thicker cyano glue to the parts and re-assembling them, if I had a jig to apply the wheels quartered then it would not be an issue. Moving On With the nylon parts fitted and the chassis now running satisfactorily on DC on with the DCC conversion. The decoder was initially programmed on ESU test board with JMRI Decoder Pro before fitting. Decoder Fitting The Digitrax DZ126 is used again, it is a very good option for Mainline loco conversions, compact, with long wires, and although for Z scale locomotives its 1A capability and 1.5A peak rating is more than adequate for 00 locos typically taking approximately 0.25A. Options, fit decoder On loco chassis - preferred In tender - power pickup from loco In tender power pickup in tender Option 1: There is little space for a decoder so space would have to be cut into the chassis to fit even a small decoder like the DZ126. But, as it has traction tyres fitted to one pair of drivers it probably needs all the chassis weight it can keep hold of. Reducing the chassis weight will make traction and power pickup worse so in this case it is probably better to fit the decoder in the tender. A loco with tyres is always a warning that it is underweight for the trains it is to pull. Option 2: After looking at how and where to squeeze the decoder into the loco body attention was turned to the tender. Plenty of space there but very difficult to get 4 wires from loco to tender from the loco end. Option 3: The loco already has limited traction so adding pickups to the tender would add unwanted drag and reduce the amount of traction available for hauling rolling stock. Chosen Option After much deliberation I decided that cutting metal off the forward loco ballast weight was the only viable option, but approx a 4mm thick slice had to be removed even to fit a DZ126. mounted with a double sided sticky pad. This loco was likely to be low on traction even with old but serviceable tyres, so I performed a gradient test with tender and 2 B Set coaches in tow, it appeared to be able to start this small train on a 1 in 40 easily and okay approaching 1 in 30. So it looks as though I can trim a bit of weight off the ballast weight, If necessary some lead could be squeezed in behind the smoke box door to compensate, lead being denser than Mazak, so less volume required. In practice this loco is likely to be restricted to short pickup goods and an alternative to a small prairie tank on the B-Sets. As I had two of these ballast weights I could afford to try reducing one of them with one as a fallback, by the time I had cut one of them the weight of this ballast was reduced from 43 gm to 39 gm so not so bad. This picture shows the difference, the notch for the wires circled. Whilst on the topic of ballast weights, the one in the tender was unnecessarily heavy at 48 gm so that was reduced to 23 gm, three pieces of steel replaced by one of lead, the steel ones were strongly glued together. This was done before the gradient test. Wiring Routing of the wires was still a challenge, a notch cut at the top of the ballast weights nose gives access to the gap between the two chassis halves. The red and black wires are attached to each chassis half by 'solder tags' formed from 32 SWG tinned copper wire, which are held to the chassis parts by 1.4 mm self tapping screws on two very convenient ledges. This also makes for easy release for maintenance or re-work. The pilot drill size is critical, in this case 1.2 mm, the mixed boxes of small screws from Amazon are intended for use in plastic, one false move and they shear, yep got that tee-shirt now! It was also better to use one screw for the cutting the thread in the metal and another for the job as the thread can easily get clogged, tricky unclogging a 1.4 mm diameter screw thread. The orange and grey wires are routed around to the brush retaining arms onto which they are soldered, I always retain service loops which is why my routing is rarely done minimally, i.e. point to point. Initial testing on my short test track, tweaked decoder speed settings and set operation to reverse mode as installation was arranged to minimise wire routing, so far so good. Fitted with donor body to minimise handling of the good body shell, the burrs which made body removal difficult filed off of the upper part of the ballast weight/chassis halves, which made re-fitting easier, confirmed wire routing does not foul body fitting. Layout Track Testing #1 Here I wanted to see how it performed with a pair of B Set coaches, in particular on the 1 in 40 inclines. Traction test showed that it could pull a pair of B-Set coaches without any apparent slip up a 1 in 40 incline. Speed control is not that good, this has been the case with some conversions, they behave differently on the layout to the rolling road or short test track. The speed of the loco pulsates but not with any apparent relationship to the driving wheels or gears. It could be partial loss of power, e.g. a grey out, to the decoder and it re-accelerating each time, then, when it reaches a certain speed it loses contact again, this could also be power pickup but not convinced. Alternatively the wires attached to the chassis halves may not be making good enough contact via the screw heads, so I have scraped paint off of the chassis so that the 'solder tags' are squeezed against chassis metal to eliminate that as a possible grey out source. Layout Track Testing #2 Little smoother but not enough to say paint was the problem. Another Decoder Swap out the Digitrax DZ126 for a Rails RoS-6D as that is a better decoder for suspect power pickup up and where fine tuning of BEMF is much easier. Fits in the same space as a DZ126 but requires addition of wires to the 4 pins required for loco driving, pins 5 & 6 cropped off, 1 to 4 shortened and bent downwards slightly. PTFE insulated wire is used as that is easier to work in tight spaces than PVC. Orange and grey wires swapped at the motor to avoid programming the decoder for reverse direction operation. Some Kapton tape is applied to avoid any pair of the pins touching the ballast weight although it is isolated from the live chassis halves by the plastic block between them. Initial testing on the test track it displayed smoother operation and the start voltage step reduced from 12 to 0, top speed retained, mid setting adjusted to suit. Much improved slow speed operation, crawls well even at step 1 of 28. The body amplifies gear noise well, especially forward. But, what about on the layout? Layout Track Testing #3 The pulsating speed fluctuation gone, runs smoother, but still noisy, typical of my Mainline locos with their coarse gear teeth, quieter in reverse, mid and top speed settings increased by 25%. Reducing the tender weight has not had any adverse effect on running tender first. The RoS-6D decoder was the one for this loco. Concluded in Part 3.2
Update to Part 3.1 above - Whoops, missed out some pictures, slapped wrist Four extra images added covering ballast weight modifications and decoder wiring. Jim
DCC Loco Conversions - 53 - Mainline 43xx Mogul 1978 - Part 3.2 Easing Body Fit Removal and fitting of the body has been difficult most of the time so during the work I used the damaged donor body rather than the good serviceable body of the original loco. The pinch point is as circled below, which to make matters worse there were burrs on both sides of the chassis acting as hooks, these burrs were filed off. There was still insufficient clearance between the inside of the body near the front splashers and the chassis. I then took a flat file to the donor body to remove some plastic from both inside faces of the body. Now the body was an easy fit, which saves pulling on the wheels and potentially damaging the quartering and the delicate piston slides from the cylinders, this modification was then applied to the good body. It also reduces motor noise a little as the contact surface area with the chassis is reduced. The area where plastic was removed from the good body is highlighted in red by image processing, same applies for the other side of the body. Traction Finishing up I tried to find the limit of its traction, the minimum acceptable was a pair of B-Set coaches, in practice it could do far better than that. A standing start on a 1 in 40 incline it started the B-set pair plus 3 Mainline (brand) Mk1 coaches without issue. This is more than I would load it with anyway as my mainline train length limit is 6 BR Mk1 coaches and local services 4 suburban coaches. All the coaches are re-wheeled with modern Hornby wheel sets but the Mk1s are still quite heavy, it could probably take more but I do not want to overload the original serviceable traction tyres or my printed axle parts into premature failure. Summary Overall this conversion was barely worth the effort, the two loco chassis had significant issues with Mazak quality in the major half of the chassis, the other parts were sound, to get one is unlucky, two means the problem is likely to be widespread. Just about every fault a Mainline loco could have was present, plus repairs due to accidental damage by the previous owner, and me! I cannot recommend converting one of these locos or ones with similar chassis to DCC, if it runs on DC you are lucky and should leave as is, they can be too fragile to dismantle even for routine maintenance. If you should want to convert one of these to DCC running I would advise a total strip down of the loco chassis before even ordering a decoder, be prepared to a have a pile of scrap or an extensive restoration task on your hands to obtain adequate DC performance. How long this loco will last as a runner is unknown, however I have too many locos relative to the amount of time available to run them all for a significant amount of time, if I am able to cycle through them all a few times I doubt I will wear any out before I am composted! But, on the plus side I have found out much more of what I can do using a 0.2mm nozzle on my Raise3D E2 printer including printing small parts in nylon, so not a total waste of time and I have added another loco to my vintage fleet. Discussion always Jim P.S. the missing motor part turned up when I did a deep tidy up of the model shop, it was well hidden behind a mains lead under my work bench Return to Index