RSS Feed for This PostCurrent Article

T&T SRRL No 24, Disassembly and installation of a DCC decoder

From Peter Smith

Initial ImpressionsSRRL No 24
This brass loco is made by Art Hobbies Inc in Korea. Everything about it is superb and it is beautifully finished in SRRL black with a Tuscan red cab roof. Straight from the box it ran both forwards and backwards but there was some hesitation and intermittent shorting between the rear truck and the body under the cab.

I could not be sure where and suspected the tender coupler which passes current from one side of each of the tender trucks.

My impression was the loco was only a few tweaks short (no pun intended) of being a superb runner.

Disassembly
I put the tender to one side and put the engine upside down in my loco cradle. There were no instructions or exploded diagram with the loco so I carefully studied the underside. Most parts are fixed with small hex head screws and I tried to identify those that might release the body from the chassis. I first released the 4 screws under the cab and removed it. This did not release the body and was not necessary ; it later went back without problems.

Next I removed both trucks carefully noting the order of assembly of the springs ( Iput all removed screws, parts etc on a small sheet of double sided tape and leave space round all 4 sides to mark the parts and any relevant notes)
Note, having read Chris McChesneys Hon30 loco handbook I did in fact try the loco without the rear truck but the hesitation was still there so I decided to reverse Chris approach and tackle each component on reassembly.

With the trucks removed it was easy to note the screw under the smokebox in line with the stack . When this was removed the front of the body was released and the smokebox support rods only rest on the footplate.

There are three screws left under the cab , a central one which I suspected fixed the motor support bracket (which it did) and two under the rear of the cab. Removing these released the body without any problems of pipes etc and the small wire harness had enough free play to allow separation of body from the chassis.

There was a small circuit board securely wrapped in masking tape. Removed of tape the circuit board only connected the front light (with two wires of course) to one of the motor terminals and to the motor fixing bracket. The other motor terminal was connected to the isolated tender draw bar
As I was installing a DCC decoder I abandoned the circuit board and never fathomed out exactly what it did or how the loco side of the pick-up system worked; I removed the wire from the motor terminal to the draw bar. I cannot therefore help anyone who wants to get perfect DC running.

Installing the decoderTender floor
After much thought I decided to replace the tender floor with one made from styrene (insulated) and to simply reverse one truck set. Thus the loco does not provide pick up. This was mainly because the loco drive wheel set and drive train are superb components, fully sprung and with a floating gearbox. There was not a trace of “glitch” and the free-running chassis is perfect. Messing it up with pick ups or solving the conundrum of the current f low of the loco were not options for me. My switches are all wired for DCC with powered frogs and my track kept scrupulously clean so I do not need multiple pick-ups.

The tender body comes away from the base with 4 screws and it is modelled with a prototypical coal space giving room for a decoder. I could have maybe done sound but decided against it as I had a small “N” scale decoder salvaged from a failed loco which fitted perfectly.

A hole through the base and tender bodies allowed wires from each truck to reach the black and red decoder wires. These were soldered to the truck pivot screws so no pick-ups were needed. This is best seen from the photos.

To be honest I am not big on lights so I decided on just two wires only between loco and tender and this was a wise decision as the rear truck is a formidable obstacle if not a real pain in the neck!

I carefully routed wires from the motor terminals under the chassis to the orange and grey decoder wires making sure the body would go back without problems. I secured the motor bracket with double sided tape rather than replace the screw because the screw disappeared though the hole in the chassis under the cab and had previously been “ ledged” to one side of the hole and tightened.

I easily replaced the body and front truck which incidentally has given no problems of shorting, derailing etc.
The rear truck was another matter. In removing the fixing screw I had stripped the thread from the hole in the chassis. I rethreaded it with two part epoxy ie epoxy in the hole and the screw very lightly oiled. This has sufficed. I carefully routed the two motor wires outside the trucks orbit and tested the loco. It was fine but I was plagued by shorts from that rear truck. It tracked just fine but oh those shorts. I covered every part of the chassis under the cab with tamiya masking tape and ended up doing the same to the truck frame as in the end I think the problem was with the wheels shorting on the truck frame. I have solved the problem but considered insulating the truck from the chassis with a nylon screw and insulated bushes or even running No 24 as a 2-6-0! Unfortunately 24 was never a 2-6-0!

Conclusion
I now have a fine running No24. BUT it has all the shortcomings of its prototype and I can only run it happily on my “main” line. It does not like radiuses less than 18 inches and it is fortunate I use the new large radius Peco OO9 switches. The old tight radius switches would be impossible so this is not a loco for micro layouts or tight curves. Also the combination of sprung front and rear trucks and fully sprung drivers make it easy to spin the wheels and it is not a prodigious hauler. Heavy coaches could be a problem but I only have one “bashed” coach (from a standard gauge one) so far so that is for another day. I added a quarter ounce of extra weight in the tender to ensure the trucks made good contact with the rails and compensated by adding the same under the cab roof. Maybe I could add weight in the boiler space vacated by the circuit board but at the moment I do not want to disassemble it again.

When I re-read Chris McChesneys experiences with the Car Works SRRL No 23 I feel quite fortunate as disassembling the valve gear would have been a definite no-no.

To be continued..

Peter Smith

You must be logged in to post a comment.