R751 class 37 conversion to dcc

[Zapper]

Hi

I'd love to convert my late 70’s R751 class 37 loco to DCC but having looked at the motor and wiring I have no idea where to start. Anyone out there in Hornby land got any suggestions. A replacement motor and or bogie ?

Phil

[Going Spare]

How the conversion is achieved will be dependent upon the type of motor bogie your model has. R751 was used for 3 versions of the class 37, two of which (D6830 in green or blue) had the twin-worm motor and the last (37130) was fitted with a ringfield unit. If yours has the twin-worm motor, it is not possible to upgrade to the ringfield motor as different main chassis frames were used.

[Fishmanoz]

GS has it spot on. The question is which running number do you have (D6839 or 37130)? Both were produced in the later 70s.

The former with the twin worm motor is the easier conversion. There’s a whole recent thread on it.

The latter with the Ringfield appears to be the type where it is necessary to isolate the LH brush holder from chassis. Google Brian Lambert and he covers conversion of all types on his DCC pages.

For either, best to do a DC stallcurrent test to see how beefy a decoder you need. Brian L covers this too.

[Cathurga]

Dredging up another older thread, but thought to keep everything on the same topic, maybe others can benefit.

I have recently acquired an old 37 and am going to run it DC for a while, and then eventually convert it to DCC. I have a few questions in both regards.

I would like to service it after an initial, cursory inspection and will clean and lube it, hopefully it will run decently. I have noted that the Service Sheet 92 is the correct one. It has the 4-wheel powered bogey with the double worm drive, and the second bogey is acting as a pickup and is wired to the powered bogey. I am going to avoid removing the main magnets as I am not sure how to have them seperated and apply a keeper, so will just polish pickups, wheels and try to clean the comm as best possible, in-situ. Will lube as best possible. I am running mostly new track so not sure whether the magnatraction system will be of any benefit, but will leave it in place.

My first question is regarding the pickup bogey..from what I can see, the pickups are connected to the rear axles and I cannot see how both wheels can be in contact with both tracks, and yet have a single pickup on the axle, surely this is a short circuit? Are one set of wheels insulated in some way? On one of my tender drive loco's, the one side of the wheels has insulation in the form of a plastic hub. Is this setup the same as that?

The second question is regarding the stall amps on one of these loco's, has anyone measured it? I am going to try and standardise on guagemaster decoders and am acutely aware that a high stall speed is likely to let the magic smoke out. I will test it while in DC format, but was hoping someone else had some previous experience.

Thanks and regards

[Going Spare]

Your track will have nickel silver rail, which will not attract the magnahesion magnets. These relied upon steel rail.

The non-powered bogie has a mixture of steel and plastic wheels on the pick-up axles, one steel wheel on each rail.

Others will be able to comment with more authority, but if the power bogie wheels have serrated treads, performance under DCC control may not be very good and, if those wheels are of the early type with deep flanges, the loco will probably struggle to pass through points (on DC or DCC) as they are now made to finer tolerances.

[Fishmanoz]

Looking at the sevice sheet and adding to GS’s comments:

• yes, the bogie has insulated wheels on one side. They don’t appear to be serated
• only the power bogie is shown with pickups. You would improve running by fitting pickups to the non-powered bogie, making sure the insulated wheels are on the same side in each bogie and the pickup wires are not swapped between insulated and non-insulated from each
• conversion is pretty much only a matter of insulating the non-insulated side of the brush spring, connecting decoder orange and grey to the brushes and decoder red and black to the pickup wiring each side. Discard the suppression capacitor across the brushes
• you will need to do your own stall current test as it depends on the condition of your motor, particularly the magnet strength which decreases with age. You can get them remagnetised. We do know that this type of motor draws more than modern motors in any condition so unlikely a 500mA decoder like the R8247 will survive.

[Cathurga]

Excellent! Thanks for the responses! I have received the loco and have had a cursory look at things. It's clear now that it does have the pickup bogey, and the insulated wheels are quite apparent, and outside of needing some cleaning, it looks to be quite serviceable. There are a few decent videos on cleaning and servicing these locos so that will be my first activity. Will try to get it running well on DC and make sure everything is functional and then look to convert to DCC. I believe the sapphire decoder is probably my best bet regardless of the stall speed.

Since the magnadhesion system is going to be superfluous, I may remove the magnets and add them to the main magnet, I've see reports that this helps 'boost' a failing older magnet.

[ColinB]

If it is a ringfield motor I would recommend using the Zimo decoder, I found these work quite well with the ringfield. No, I don't have shares in Zimo, I tried quite a few of them (Gaugemaster, DCC Concepts, Hattons) and found Zimo to be the best and most reliable. Their normal current limit is about 0.8 amps, although I think the maximum is a bit more which should be enough for a Ringfield. I had them running in all my Ringfield based locos. If it is the dual worm drive, Zimo do a 2 amp version, there is also someone on EBay that sells a 2 amp variable limit one. The only issue I had with the dual worm drive, is though conversion to DCC is quite easy, it is quite easy for a short to occur between the pickups and motor wires, taking out the decoder. It did that to mine on my EM2. In the end with the EM2, there was a guy on EBay that converted the bogie to take a modern class 66 motor, so I paid him to convert it. With my second one, I saw what he did and did the conversion myself. For DCC operation I would recommend picking up the power from as many wheels as possible.