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Noel's DCC Conversion Bench

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Noel
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It's many many years since I dissected, repaired and serviced locos, and I'd forgotten how much I enjoyed it? All the different and sublet ways of getting bodies off, bogies out, wheels off, steam running gear off, etc.

 

I've started servicing and evaluating my 15-50yo collection of Locos for suitability for DCC. Basically I'm giving each one a basic service so I can test run on DC and decide if they run smoothly enough to bother putting a decoder in. I have already ruled out the Hornby-Dublo and Triang locos, but some of my older Hornby steam locos from 1980s onwards might be ok, and I hope most of the early 90s Bachmann, Hornby and Dapol will run smoothly enough to warrant fitting decoders. I've already added power pickups to some of the bogies on 2-6-2 tank engines which seems to have made a huge difference running over points.

 

Tonight after the Lima class 33 thread, I took my pair apart and serviced them. Both running a lot better, but those late 1970s Lima power bogies are very basic motors, so I don't think I'm going to convert them to DCC unless I re-motor them and add flywheels, or buy modern replacement bogies that they used in their later 90s models (bo-bo). I'd prefer bogies that don't use friction tyres so power pickup is possible on all eight wheels (i.e. four axels), rather than two wheels on opposite sides of powered and non powered bogies as was the custom in the 70s and 80s.

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Noel, I have four Lima Class 26 & 27 locos, which are mechanically identical to the Class 33 loco. I have remotored them with motors taken from CD-ROM drives. The difference is phenomenal, much smoother and quieter, and no real need for a flywheel. All that is required is a drive gear for the motor. The original Lima armature and magnet are removed, and the motor secured in place. I have used small screws through the housing to allow for position adjustment of the motor for minimum gear noise. I have found that the smaller the gear is, the better, as the motor runs much faster than the original. Speed can be fine tuned by adjusting the appropriate CVs in the decoder.

Getting rid of the tyred wheels is also quite simple. All you need is two plain insulated wheels. The wheelsets are removed from the bogie, and the moulded gear is sliced off the back of the tyred wheels with a craft or Stanley knife. The uninsulated wheel is drifted off the axle, and the raised boss on the back of the wheel is filed flat. The wheel is refitted to the axle and the gear pushed on flush with the back of the wheel. The gear is a good fit on the axle, and to prevent it from spinning, I drilled a 1mm hole through the wheel and gear and inserted a 1mm brass pin, which, with luck, will be an interference fit. Fit the wheel and axle back on the bogie and fit the new insulated wheel. The reason for fitting the gear to the uninsulated wheel is that there is no room to fit a pickup on the gear side of the bogie, so the driven wheel is now picking up via the original pickup. For pickup on the other side, a piece of phosphor bronze strip is fitted to the bogie on the new insulated side. Because the original pickup is now picking up from the gear side, the polarity is now reversed, requiring the original wiring to be changed to the other motor brush.

Fitting an extra pickup to the trailing bogie is also just a case of a piece of phosphor bronze strip fitted to the insulated side, and wiring as appropriate.

I have used this method of removing tyres and fitting pickups for many years on Lima locos. The motor conversion, however, is only suitable for 4 wheel drive units, as the CD-ROM motor is much wider than the original pancake motor, and will foul the centre wheels of a 6 wheel unit.

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Noel, I have four Lima Class 26 & 27 locos, which are mechanically identical to the Class 33 loco. I have remotored them with motors taken from CD-ROM drives. The difference is phenomenal, much smoother and quieter, and no real need for a flywheel. All that is required is a drive gear for the motor. The original Lima armature and magnet are removed, and the motor secured in place. I have used small screws through the housing to allow for position adjustment of the motor for minimum gear noise. I have found that the smaller the gear is, the better, as the motor runs much faster than the original. Speed can be fine tuned by adjusting the appropriate CVs in the decoder.

Getting rid of the tyred wheels is also quite simple. All you need is two plain insulated wheels. The wheelsets are removed from the bogie, and the moulded gear is sliced off the back of the tyred wheels with a craft or Stanley knife. The uninsulated wheel is drifted off the axle, and the raised boss on the back of the wheel is filed flat. The wheel is refitted to the axle and the gear pushed on flush with the back of the wheel. The gear is a good fit on the axle, and to prevent it from spinning, I drilled a 1mm hole through the wheel and gear and inserted a 1mm brass pin, which, with luck, will be an interference fit. Fit the wheel and axle back on the bogie and fit the new insulated wheel. The reason for fitting the gear to the uninsulated wheel is that there is no room to fit a pickup on the gear side of the bogie, so the driven wheel is now picking up via the original pickup. For pickup on the other side, a piece of phosphor bronze strip is fitted to the bogie on the new insulated side. Because the original pickup is now picking up from the gear side, the polarity is now reversed, requiring the original wiring to be changed to the other motor brush.

Fitting an extra pickup to the trailing bogie is also just a case of a piece of phosphor bronze strip fitted to the insulated side, and wiring as appropriate.

I have used this method of removing tyres and fitting pickups for many years on Lima locos. The motor conversion, however, is only suitable for 4 wheel drive units, as the CD-ROM motor is much wider than the original pancake motor, and will foul the centre wheels of a 6 wheel unit.

 

Thanks Dhu Varren. There may be life yet in the old 33s. :) Not sure if I'm tooled up to handle the wheel job.

 

"All that is required is a drive gear for the motor" - Any suggestions for a source for the drive gear?

 

Noel

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No special tools required for the wheel job, just a light hammer and an old 2mm axle to drift out the Lima axle from the wheel. The axle can be refitted with the hammer and a piece of brass over the axle, to ensure the end of the axle does not get damaged by the hammer. Just make sure the axle goes in straight. It is a shame we are so far away from each other, otherwise I could do the wheels for you.

Sourcing drive gears can be a bit of a problem. I don't know of any retail source. However, the old Airfix Loco tender drive unit has four idler gears in it which are of a suitable size. These tender drives can be picked up for very little at exhibitions, or model shops that have a junk box, maybe even eBay.

Another option is to cut the gear off an old Lima armature, in a drill, with a razor saw. The only problem there is that the hole in the gear is too big for the CD-ROM motor shaft, and would need to have a sleeve fitted to fit the shaft.

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I replaced the Ringfield motor in a Hornby HST with one form a CD drive a while back. Like Dhu Varren said the result is far better.

 

Here's a link to my workbench thread that shows it running - http://irishrailwaymodeller.com/showthread.php/77-Graham-s-Workbench/page12 Scroll to the bottom of the page.

 

As Dhu described the gear off the old motor shaft is to big so I cemented a small piece of brass tube over the shaft for a tight fit.

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Got a 25yo BR Class 25 diesel done today, and in the middle of converting a 30yo Hornby GWR Pannier tank (TMS 9pin). Put a Digitrax 126D in the old diesel and wasn't satisfied with the running, but then read up a bit more on some of the CVs that assist older motors and wow what a difference it makes with settings like pulse frequency and BEMF - all new to me. A different loco! The more I learn about setting up DCC decoders the more I realise how very much I have to learn! :) Enjoying fiddling around with locos, soldering iron and wires again after such a long break. A good service and DC test run seem essential before fitting decoders. Four done, more to do! Got three cab bus sockets wired up around the layout with RJ12 crimping tool and some cable.

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Got a 25yo BR Class 25 diesel done today, and in the middle of converting a 30yo Hornby GWR Pannier tank (TMS 9pin). Put a Digitrax 126D in the old diesel and wasn't satisfied with the running, but then read up a bit more on some of the CVs that assist older motors and wow what a difference it makes with settings like pulse frequency and BEMF - all new to me. A different loco! The more I learn about setting up DCC decoders the more I realise how very much I have to learn! :) Enjoying fiddling around with locos, soldering iron and wires again after such a long break. A good service and DC test run seem essential before fitting decoders. Four done, more to do! Got three cab bus sockets wired up around the layout with RJ12 crimping tool and some cable.

 

It is certainly an eye opener, but very satisfying, when you start delving into the inner workings of decoders.

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Hi Noel

I have yet to do this so I'm going to be watching your thread carefully I had no idea what back EMF was either so I literally looked it up yesterday.

Apparently it makes a huge difference by monitoring the output from the motor and constantly changing the signal to the loco to keep it running smoothly instead of stops and starts particularly at low speed and even with slightly dirty track. Of course that's no excuse for not cleaning your track but it seems that back EMF is hugely advantageous with older motors and three pole motors which would not be as smooth as five pole or double flywheels.

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Hi Noel

I have yet to do this so I'm going to be watching your thread carefully I had no idea what back EMF was either so I literally looked it up yesterday. Apparently it makes a huge difference by monitoring the output from the motor and constantly changing the signal to the loco to keep it running smoothly instead of stops and starts particularly at low speed and even with slightly dirty track. Of course that's no excuse for not cleaning your track but it seems that back EMF is hugely advantageous with older motors and three pole motors which would not be as smooth as five pole or double flywheels.

 

Well I'm very much still in the learning process myself. Got an old Hornby Pannier tank sorted with a TCS T1-LED decoder.

 

It is certainly an eye opener, but very satisfying, when you start delving into the inner workings of decoders.

 

These old Hornby locos with X04 motors have the chassis grounded with the motor, so needed to isolate the second motor bush pickup.

A491F516-B85B-49FA-90CB-C8C9594D5C61.jpg

 

Not much space inside, so fitted the decoder in the coal bunker.

38041B32-FA16-40CC-B374-D722B62D0929.jpg

 

Will make a proper fitting coal cover later.

FF2F677A-F146-42F4-A8FB-EBD4032A39A6.jpg

 

Just discovered my ancient Hornby BR blue class 37 and its rake of BR Mk2s coaches won't run over Peco code 100 points. I probably haven't run this loco or coaches since I was a child, so will have to replace the coach wheels with smaller depth flanges and machine down the flanges of the diesel bogies. She was a nice runner so a shame to retire her without trying.

Edited by Noel
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Good work, Noel. Thanks for the photos. I'm thinking of trying to equip a Bachmann J18 with a decoder when I acquire one. As far as I know the chassis is isolated from the motor. Hope I'm right about this or I'll be referring to your photos when I open her up. Good solution to your space problem. I was also wondering if I'll have room.

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Aha, there is a little bit more to DCC track wiring conversion then I had thought. Crossings and double slips!!! Now do I use isolating switches, or electronics (ie reversers)?

 

I've been testing DCC on the layout for a few weeks now with DCC drops to the middle and upper levels working ok. Haven't gone near the terminus yet which is still DC. However I noticed the crossing linking the dual track incline linking the upper and middle level is causing intermittent shorts as metal coach wheels run over the plastic frog briefly bridging the circuit. Temporary solution has been to isolate the incline using the existing old block section wiring switch, but a more permenant solution may be needed. Any suggestions from experience?

 

Glad I have left permenant track ballasting until the layout is totally finished and went with foam underlay initially. Makes pulling track up for wiring changes easier.

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Sourcing drive gears can be a bit of a problem. I don't know of any retail source. However, the old Airfix Loco tender drive unit has four idler gears in it which are of a suitable size. These tender drives can be picked up for very little at exhibitions, or model shops that have a junk box, maybe even eBay.

 

Have just completed a repair to an Airfix/early Bachmann tender drive as fitted to the 2P and 4F. This type of tender drive does not have the small idler gears mentioned above. It would appear that it is only the longer wheelbase tender drive, as fitted to the Stanier type tender that has the small gears.

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Aha, there is a little bit more to DCC track wiring conversion then I had thought. Crossings and double slips!!! Now do I use isolating switches, or electronics (ie reversers)?

 

I've been testing DCC on the layout for a few weeks now with DCC drops to the middle and upper levels working ok. Haven't gone near the terminus yet which is still DC. However I noticed the crossing linking the dual track incline linking the upper and middle level is causing intermittent shorts as metal coach wheels run over the plastic frog briefly bridging the circuit. Temporary solution has been to isolate the incline using the existing old block section wiring switch, but a more permenant solution may be needed. Any suggestions from experience?

 

Glad I have left permenant track ballasting until the layout is totally finished and went with foam underlay initially. Makes pulling track up for wiring changes easier.

 

The short is usually caused by the tread of the wheel bridging the gap between the rails at the frog of the point on insulated points. Are you using live or insulated frog points?

 

Also, are the coaches causing this problem older models? The wheels on Lima and older Hornby MK3's have a very wide thread which bridges the gap easily. The best option is to change the wheelsets, easy enough with Hornby but the Lima wheels have a shorter axle. Replacements can be found but they're not cheap.

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The short is usually caused by the tread of the wheel bridging the gap between the rails at the frog of the point on insulated points. Are you using live or insulated frog points?

 

Also, are the coaches causing this problem older models? The wheels on Lima and older Hornby MK3's have a very wide thread which bridges the gap easily. The best option is to change the wheelsets, easy enough with Hornby but the Lima wheels have a shorter axle. Replacements can be found but they're not cheap.

 

Thanks irishthump. The main culprits are metal wheels on Bachmann loose coupled mineral wagons (steel coal wagons), and some old lima BR Mk1s in Blue/Grey 70s livery (possible donors for IR EGVs). By thread do you mean the thickness of the flange, or the depth of the flange or other?

Thanks. Noel

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Thanks irishthump. The main culprits are metal wheels on Bachmann loose coupled mineral wagons (steel coal wagons), and some old lima BR Mk1s in Blue/Grey 70s livery (possible donors for IR EGVs). By thread do you mean the thickness of the flange, or the depth of the flange or other?

Thanks. Noel

 

By the thread I mean not the flange but the part of the wheel that actuallt touches the rail. If these are are to wide (or thick if you like) they will easily cause a short. Like I said the old Lima's are notorious for this....

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Noel, two questions. 1. What make of crossing are you using. 2. Can you provide a sketch, or photo of the track in the vicinity of the crossing.

 

Noel, the reason I asked what make of crossing you are using, is that I have been using Peco crossings for years with DCC, and never had any problems with short circuits caused by wheels, and I have plenty of Lima metal wheels still in use. The sketch or photo was to have a look to see what, if any, problems there might be with the track, or track layout, and try to work out a possible fix.

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Hi Noel,

Your terminus has very complex trackwork with lots of crossovers and double slips etc. if I remember correctly. You may want to post a shot of this for Dhu Varren and consider what the solution is for the whole layout, just in case (say) rewheeling everything solves your problem here only for it to recur when you hit the terminus conversion. Just a thought

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Hi Noel,

Your terminus has very complex trackwork with lots of crossovers and double slips etc. if I remember correctly. You may want to post a shot of this for Dhu Varren and consider what the solution is for the whole layout, just in case (say) rewheeling everything solves your problem here only for it to recur when you hit the terminus conversion. Just a thought

 

HI DC

 

Thanks. Yes the double slips and cross overs may pose a problem unless adjusted for DCC, but I will do some test runs over it next weekend with various rolling stock. It was wired for DC block sections 19 years ago so I may just have to leave all sections switched on for a DCC test. I was about to start scenery filling this weekend (i.e. foam + plaster) but have put that on hold until any wiring adjustments needed for DCC have been completed (i.e. 1st fix electrical).

 

Noel

 

Pic as requested. Track work approaching terminus platforms.

DSC_6537.jpg

Edited by Noel
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Its funny what you learn all the time. Nearly gave up on an old X04 Hornby 0-6-0 Panier Tank DCC conversion. Had a TMS T1 decoder installed, but very shaky running, in fact worse than I remember on DC. Put it back on DC but it was running quite well for it's vintage. So did a full decoder reset and now its running as well on DCC as it had on DC. Bizarre. The only settings I remember changing 1st time around after I fitted it were standard CVs 2,5,6,3,4. I guess the BEMF somehow modifies its algorithm based on these CVs and it didn't suit the old X04 motor. Might try another decoder in her to see if that make a difference even though she is well enough ok now for an old chassis.

 

Any words of wisdom or suggestions for those who have already been in these 'pot holes'? :)

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Its funny what you learn all the time. Nearly gave up on an old X04 Hornby 0-6-0 Panier Tank DCC conversion. Had a TMS T1 decoder installed, but very shaky running, in fact worse than I remember on DC. Put it back on DC but it was running quite well for it's vintage. So did a full decoder reset and now its running as well on DCC as it had on DC. Bizarre. The only settings I remember changing 1st time around after I fitted it were standard CVs 2,5,6,3,4. I guess the BEMF somehow modifies its algorithm based on these CVs and it didn't suit the old X04 motor. Might try another decoder in her to see if that make a difference even though she is well enough ok now for an old chassis.

 

Any words of wisdom or suggestions for those who have already been in these 'pot holes'? :)

 

Noel, it might be worth switching off the BEMF, and seeing how the loco runs. I have had similar issues myself, and switching it off did make an improvement. You can always switch it back on again if there is no improvement.

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HI DC

 

Thanks. Yes the double slips and cross overs may pose a problem unless adjusted for DCC, but I will do some test runs over it next weekend with various rolling stock. It was wired for DC block sections 19 years ago so I may just have to leave all sections switched on for a DCC test. I was about to start scenery filling this weekend (i.e. foam + plaster) but have put that on hold until any wiring adjustments needed for DCC have been completed (i.e. 1st fix electrical).

 

Noel

 

Pic as requested. Track work approaching terminus platforms.

 

Noel, thanks for posting the pic. Nice track layout. My first thoughts were that the slips could be the problem. Unfortunately, I don't have any slips on my layout to examine, as I try to avoid them where possible, although there are some in my local club. However, I am going away for two weeks, so I can't do anything until I return.

My second thought was that perhaps there are wheels on some of your vehicles that have not got the correct back to back measurement, and are causing a short by the back of the wheel touching the switch rail. I know it should not happen, but even new vehicles can be incorrect. A friend of mine bought a new Bachmann loco recently which continuously kept derailing at certain places. He blamed the track on the layout, even though all other locos ran fine, and got a little upset when I asked if he had checked the back to backs. He eventually did check, and lo, the back to backs on a number of wheelsets were incorrect. Opening out the wheels just a fraction cured the problem. I always make a point of checking the back to back on any wheels, from any source, that I fit.

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Noel, thanks for posting the pic. Nice track layout. My first thoughts were that the slips could be the problem. Unfortunately, I don't have any slips on my layout to examine, as I try to avoid them where possible, although there are some in my local club. However, I am going away for two weeks, so I can't do anything until I return.

My second thought was that perhaps there are wheels on some of your vehicles that have not got the correct back to back measurement, and are causing a short by the back of the wheel touching the switch rail. I know it should not happen, but even new vehicles can be incorrect. A friend of mine bought a new Bachmann loco recently which continuously kept derailing at certain places. He blamed the track on the layout, even though all other locos ran fine, and got a little upset when I asked if he had checked the back to backs. He eventually did check, and lo, the back to backs on a number of wheelsets were incorrect. Opening out the wheels just a fraction cured the problem. I always make a point of checking the back to back on any wheels, from any source, that I fit.

 

Thanks Dhu Varren for both replies. I will check the wheels and the BEMF settings. On the TCS T1 decoder there is a setting CV182 to adjust the BEMF to suit 3 pole motors which I will also try. I swapped the TCS with a Digitrax for a test run as they use the same 9 pin harness but not much difference, so I am going to focus on the wheel pickups. There is no doubt the Bachmann 0-6-0s are in a different league to the Hornby 0-6-0s as regard mechanical build quality and decent electrical pickup on all 6 wheels. I'm just fond of my 25yo old GWR pannier tank, but won't even attempt to DCC my 37yo 0-6-0. If I get the wheel pickup working better I may change the X04 to a 5 pole motor I salvaged. The Bachmanns are split chassis so I need to get a few tools so I can tab screws into either chassis metal halves for soldering the red/black decoder pickup wires, and then insulate the enclosed motor from the chassis.

 

PS: Re the terminus track layout, preliminary tests with MM 071 and MM 141 have proved successfully running over the point work and double slips at crawl speed. Again a problem may be outsides metal wheels on some rolling stock as you suggest. Some of my ancient Lima BR Blue/Grey have very deep flanges and may need rewheeling with plastic or shallower flanged metal wheels.

Edited by Noel
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OK two simple old Hornby’s converted to DCC so far (Pannier Tank + Class 25), now to tackle some of my more difficult Bachmann steam locos. Most are about 20 years old and none are DCC ready. So I have decided to start with the most difficult:

 

A Bachmann 31-901 BR Pannier Tank loco with the awkward split chassis. Space is tight and the split chassis is grounded to both rails!!!

 

F09BD2A9-121A-43D3-AE17-CAC68CFFF2E1_1.jpg

 

Power pickup on all wheels due to split chassis

EBDE4ADE-02D9-4BC9-8834-BB7C9AD29210.jpg

 

Bachmann split chassis have a clever arrangement where the split axils transfer power separately to each side of the split chassis. Each chassis half connects directly to the motor bush on the same side using a sprung metal tab the connects one side of the motor with the opposing chassis half.

 

Chassis sandwiches the motor with power pick up on all wheels via split axils

F26B127B-14A9-435B-B7B7-A1CB8DD71913.jpg

 

There isn’t a millimetre spare between the chassis and the inside of the loco body, and no part of the chassis that can be cut off without destroying it’s functional integrity.

AD9BF8A7-305C-4921-A414-2E51A3B88E5D.jpg

 

1st task is to establish where the decoder might fit. There is no space inside the boiler area and no metal I can cut off the chassis to squeeze it in, but there will be plenty of space in the coal bunker once I remove the coal bunker from the rest of the model and extract the cast iron weight that fills the bunker space.

 

The coal bunker that contains a weight comes off the back. Carefully remove a metal railing the connects the removable aft coal bunker to the roof section before pivoting the bunker backwards.

9DAF4E93-C34F-479B-A3C6-E3276FE5D018_1.jpg

 

Remove the cast iron weight to make space for the decoder

DFA03CF9-7DFC-453E-9A07-58EB8B33C1E5.jpg

 

FD38CCAB-559E-4FBF-A539-C74D69F3D702.jpg

 

Next is to explore how these split chassis locos are built. Basically the motor is sandwiched between the two halves sides of the chassis that are electrically isolated from each other by plastic bushing separators. Three screens into plastic receptors hold the two chassis halves together. There are NO wires, the two motor bushes touch each side of the chassis with a sprung metal strip. These have to be isolated from the chassis for DCC.

 

On RHS side of motor you can see the metal sprung tab the would contact the missing chassis half on this side. This has to be isolated and soldered to decoder.

E195FB2A-33E8-463D-BCBC-DB73D941F798.jpg

 

You can just make out the sprung metal strip at the bottom of shot that normally connects the motors bush to one side of the chassis.

8ce88adb-33be-4314-96f6-10d2487c98db.jpg

 

Motor removed. Bend sprung tabs inwards and solder grey/orange decoder wires to each using heat shrink and insulation tape for added measure to fully isolate the motor pickups from the live chassis.

 

Solder decoder grey/orange wires to the two motor bush contact strips

93F18E9F-DE2B-4CAE-9AA4-18A8FD0DB31C_1.jpg

 

Use heat shrink plus insulation tape to ensure motor is totally isolated from both chassis sides.

AB22E1AC-DCFA-475B-8E4D-304C48B0336F.jpg

 

Motor soldered to decoder grey/orange wires, sprung contacts isolated with shrink wrap, and some insulation tape added for good measure. Ready to attempt to reassemble the two chassis halves

8CD3C39E-C86E-4277-A34E-2F87BB246372.jpg

 

Motor connected to decoder grey/orange wires reinstalled in the chassis sides. It was like putting a swiss watch back together with all the plastic bushes and separators. Careful not to over tighten the screws or the two halves will compress the motor too much leading to binding.

CE2822E7-41E5-4662-B174-47798798AE98.jpg

 

First I connected the decoder to the test track using jump leads to verify the connections to the motor were working ok. Then I had to do a test run of the motor back inside the chassis adjusting the three chassis screws so the motor and gears could run freely (ie not compress the two halves too close together).

 

Final step tomorrow is to connect the decoder’s black and red wires to each half of the chassis. I have elected to do this using sprung contacts squeezed between the gap between the chassis sides isolated using a piece of plastic card. I don’t have the tools to drill and tap the chassis for screws to solder the red and black wires, and they will not solder directly to the chassis block. More to follow as soon as I get the contact strips installed between the two chassis sides . . . TBC

 

This is all very fiddley but enjoying it :)

 

Good night

Edited by Noel
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Noel, this is really great detailed step by step on how to do something that seems somewhat enigmatic to the novice:confused: What a great series with photos of every step :-bd I am looking forward to the final installment whenever that will occur. Maybe a moderator will think this worthy of a sticky when it is done:tumbsup:

Edited by DiveController
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Excellent work there Noel, just one point, the warranty is void on the chip when you cut the plug off. But given the very tight squeeze in that loco you would have no other way of doing it. Looking forward to seeing it finished.

 

Thanks Dave et al. That particular TMS decoder comes with a wires only harness, no plug at the loose end only the 9 pin plug that mates with the decoders pcb socket. AAMOI I bought a few extra 9 pin harnesses so I can wire more locos to the harness before committing them to a specific chip, and so I can swap decoders to match the motors in different locos. Many of the main decoder vendors seem to have variants of their decoders with 9pin pcb sockets.

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Thanks Dave et al. That particular TMS decoder comes with a wires only harness, no plug at the loose end only the 9 pin plug that mates with the decoders pcb socket. AAMOI I bought a few extra 9 pin harnesses so I can wire more locos to the harness before committing them to a specific chip, and so I can swap decoders to match the motors in different locos. Many of the main decoder vendors seem to have variants of their decoders with 9pin pcb sockets.

 

Careful, not all makes of decoder use the same size 9 pin plug. I have decoders from Gaugemaster, DCC concepts, Digitrax and Lenz and they all use different size plugs!

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Ok got back to 'split chassis' DCC conversion this evening. All that remained to be done was connect the decoders red and black wires to each side of the chassis!!! Hmmm - that was not the easiest as there is nowhere to anchor the wires, and not a 1/2mm spare between the chassis and the loco body, so couldn't sandwich the wires between the chassis with insulators on one side and could not run the wires back inside the body as no room above or either side of the chassis which completely fills all space inside the boiler.

 

Solution was to file a small front section of both chassis sides clean and drill a hole in each chassis half into which I could directly solder the wires.

IMG_4302.jpg

 

It took two attempts to successfully solder to the chassis sides and I had to use the big soldering iron to create enough heat so that the solder was taking to the chassis metal in the hole. The hole was about 3mm deep. View of the rear of the chassis halves. These ends will be in the loco cab with the wires running to the decoder in the coal bunker. WARNING - When soldering to the chassis halves remove all other heat sensitive components (i.e. the motor, plastic insulator grommets, spaces, and the white screw lugs).

IMG_4304.jpg

 

Putting the chassis sandwich back together again is fiddly but with care positioning the three plastic separating insulators and the two white screw anchors. Three screws hold the chassis halves together. These screw into the plastic isolators which go through a plastic shim. The three shims theoretically separates the two chassis halves at the exact distance to allow smooth running of the gears.

IMG_4305.jpg

 

Temporarily hooked up the chassis halves to the rails via clip leads to test the smooth running of the motor and gears before final reassembly. This is where the three chassis screws may need a little loosening to barely widen the gap between the two chassis so that the motor runs freely. This bit was trial and error until I got smooth running.

IMG_4306.jpg

 

I made the mistake at first attempt to put the wheels back in the chassis and screw back the under plate before I had reinserted the chassis into the loco body. It was much easier to fit the bare chassis back into the body and feed the four decoder wires aft into the cab without the wheels and under frame on.

IMG_4307.jpg

 

A little detail. Two small notches cut in the cab floor so that the new solder joints to the chassis do not get pulled out when refitting the chassis into the body.

IMG_4308.jpg

 

At last done - put 5796 on the rolling road for a test run. These split chassis Bachmanns do not like to be disturbed, and I had to make one more small adjustment to the chassis screws before she would run freely again. Effectively though this loco will need to be 'run in' again.

IMG_4309.jpg

 

Finished - BR (ex-GWR) 5796 Pannier tank loco with TCS T1-LED decoder. Needs a final bit of tidying up by painting the visible wires inside the cab black.

IMG_4310.jpg

 

I have to say it was quite a lot of bother, and trial and error, probably because it was my first attempt at a split chassis tank loco, and I nearly got fed up with it. Hopefully as I learn more about the different loco chassis/body combinations future conversions will take less time. How anybody puts sound decoders and a speaker into a 0-6-0 tank loco is a mystery to me unless they are watch makers! :) I think I will pass on that one. There is actually enough space to put a small speaker in the cab but it would be partially visible.

 

Anyway she is running well, but needs another 45mins running in time to really loosen her up. I had greased the gears and lubricated her before putting her back together.

 

What have I learned about fitting DCC to a non-DCC ready split chassis Bachman?

 

  • Ensure the loco is a smooth runner on DC before conversion - DCC won't make a poor runner any better
  • If a new loco, run it in for an hour on DC before conversion
  • Recommend using a decoder that comes with a removable harness (e.g. 9pin harness). Saves wires breaking off the decoder and means you only have to feed the decoder plug through gaps in the loco during assembly (i.e. rather than the decoder)
  • Ensure the motor is 100% electrically isolated from the chassis and track. Only the orange and grey wire should connect with the motor pickups.
  • Be patient and very very gentle when taking apart. Make a note of where different length screws were used on the chassis.
  • When soldering to chassis ensure you don't melt any plastic components on the chassis (i.e. remove all plastic bushes, lugs and spacers). Using an Iron hot enough to solder to the chassis metal generates a lot of heat in the chassis.
  • Test the decoder on your DCC test track (i.e. see if it can be read). If you made a booboo with the wiring the decoder will not read, but at least it won't be fried if you use the test track (i.e. it uses low power).
  • At stages of reassembly test the motor and gears are running freely before putting the wheels and body back on
  • Buy DCC ready locos in future. :)

 

Next up another 0-6-0 Bachmann 5700 tank loco, but the next one is not a split chassis model so it should be a lot quicker, but I expect I may have to cut away a piece of the chassis if I want to locate the decoder completely out of sight in the boiler (i.e. not in the coal bunker with wires through the cab). Alternatively I might do one of my 20yo Hornby tender drive Princess class. Good Night.

Edited by Noel
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