Converting the Flying Scotsman to DCC

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Flashbang
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Re: Converting the Flying Scotsman to DCC

Postby Flashbang » Thu Apr 26, 2018 5:20 pm

Hi

If you're going to read the DC current that the motor uses when powered by DC and the stall current too, I would use the 10A meter range for both tests. Ringfield motors will almost certainly draw more than 200 milliamp running. You risk blowing the internal fuse in the meter if you exceed 200ma when the meter is in that position.
Disconnect all decoder wiring.
Set red meter test lead into the left hand socket and black lead in the Com middle socket, turn dial to 10A (just past the quarter past position). Disconnect, if not already removed, the wire from the motor that goes to the coupling pin and connect the red meter lead to the end of this removed wire and the black lead to the right hand motor terminal. Ensuring the left hand terminal has the wire attached that connects to the chassis. Apply DC power to the coupling pin and the metal chassis connection and the motor should turn and the meter give a reading. Note this as its the normal load current. While the motor is turning stop it from turning by hand and quickly read stall current. DONT ALLOW THE MOTOR TO BE STALLED FOR MORE THAN A COUPLE OF SECONDS!

Now remove DC power and meter leads. Move meters red lead to meter right hand socket. As a double check... Switch meter to its 200 Ohm range (6 o clock position) which appears to have a buzzer sounder too. Touch meter leads together to check a full short is displayed and perhaps a buzzer sounds too. Remove both wires from the motors two tab terminals and then clip one meter lead to the left hand tab and test with the other meter lead to metal the tenders chassis and then to all wheels. No reading or buzz should be obtained. Repeat with meter lead on right hand motor tab and to chassis and wheels again, no reading should be noted. Assuming all is correct then obtain a decoder that has a rating exceeding the running current measured. Turn meter switch to Off.
Broken? It was working correctly when I left it.

Bramshot
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Re: Converting the Flying Scotsman to DCC

Postby Bramshot » Thu Apr 26, 2018 10:20 pm

So what is wrong with simply running the loco with a rake of coaches around the track and inserting the meter into the dc supply to the tracks? That will give true indication of the current while running. Hold the loco stationary to get stall current.

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Flashbang
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Re: Converting the Flying Scotsman to DCC

Postby Flashbang » Fri Apr 27, 2018 10:50 am

Bramshot wrote:So what is wrong with simply running the loco with a rake of coaches around the track and inserting the meter into the dc supply to the tracks? That will give true indication of the current while running. Hold the loco stationary to get stall current.

Nothing is wrong with that way at all and if the loco is a DC only one it is the normal way to proceed. See .... Link to stall and normal current test
But this loco has a decoder inside it, therefore it has to be opened to remove it and its wiring, so while its open and the decoder is disconnected it is far easier IMO to do the test directly to the wires that feed the motor!
Broken? It was working correctly when I left it.

Bramshot
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Re: Converting the Flying Scotsman to DCC

Postby Bramshot » Fri Apr 27, 2018 5:39 pm

According to the thread, the OP has removed the decoder at this point to do the dc testing.

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Flashbang
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Re: Converting the Flying Scotsman to DCC

Postby Flashbang » Fri Apr 27, 2018 6:55 pm

So the loco body is off then, so it is open! Don't see the point of your comment at all in this case?
Broken? It was working correctly when I left it.

Bramshot
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Re: Converting the Flying Scotsman to DCC

Postby Bramshot » Sat Apr 28, 2018 3:48 pm

According to the OP the loco is now running fine on DC with decoder removed and original wiring restored, which I took to mean was running on the track on DC, so easier to monitor the supply current to the track to connect to the motor wires ( the body might be back on again for all we know), than disconnect the motor wires. Also gives truer indication of on -load current to monitor while running on the track and pulling a rake, than by connecting to the motor terminals while running light in your hand.
However , I must add that I do not disagree with anything you said in your original post, which was a full and correct description of what to do if the loco had been in the state you assumed it to be in.

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dazamccoy
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Re: Converting the Flying Scotsman to DCC

Postby dazamccoy » Wed May 09, 2018 11:44 am

I contacted Hornby to let them know what was happening, they asked me to send it in for repair. I'll hopefully have it back soon.

I got some crocodile clips and some extra wires for my multimeter hooked it all up and the stall current is 450ma, well within the 500ma limit of the decoder. I also got some new carbon brushes, I had a hell of a time getting the old ones out. They'd pretty much turned into mush.

IMG_6922.JPG


Can you guess which one's the old one? Hahaha.

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dazamccoy
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Re: Converting the Flying Scotsman to DCC

Postby dazamccoy » Sun May 13, 2018 6:55 pm

I installed the replacement decoder today and I’m very disappointed by the quality of the soldering to the chip! The green wire was hanging on by a single strand of wire and came away within seconds of handling the chip. All the other connections have very long bits of bare wire dangerously close to one another. Not impressed in the slightest. I had to splay the wires in opposite directions then insert a piece of sellotape to make sure nothing touched.

IMG_6926.jpeg



Theres a good 5mm of bare wire from every contact!!!!

TTS wiring nightmare!.jpeg


Initially the slow running was very jerky but I did some research and changed CV151 = 255 and CV152= 1. This sorted that and I now have very nice slow running.

The only remaining problem that I have is... The loco seem to reach its top speed about half way up the speed scale. I have tried changing between 14/28/128 and is the same for each. Once I go faster the loco stops (the sound continues so it's not an electrical problem) then starts again but seems to reset where zero is in the speed scale.

It's easier to watch a video. I'm using a Bachmann Dynamis Pro. I have another loco with a DCC concepts 6 function decoder which works flawlessly.

https://youtu.be/dDe9QRs0O1o

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dazamccoy
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Re: Converting the Flying Scotsman to DCC

Postby dazamccoy » Sun May 13, 2018 7:52 pm

I do like the slow running after changing the CV values.

https://youtu.be/7x_RLJ-du24

Bramshot
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Re: Converting the Flying Scotsman to DCC

Postby Bramshot » Sun May 13, 2018 9:54 pm

That is really awful soldering!
Very strange behaviour too. I don’t know anything about those decoders, but do they have the facility for a user defined speed curve? It is almost like it is running one that has been set up in a most peculiar way. What do those CV s you mention claim to do? How is CV 29 set up?

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RAFHAAA96
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Re: Converting the Flying Scotsman to DCC

Postby RAFHAAA96 » Mon May 14, 2018 9:22 am

You can switch the motor algorithm between roughly linear and logarithmic and also use the associated CVs to tune the PI characteristics of each algorithm, i.e. the way the motor reacts to acceleration and decelleration. You can also adjust the bemf CV10 which has an effect on these algorithms.
Rob
RAF Halton Brat - 96th Entry
http://www.halton96th.co.uk

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dazamccoy
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Re: Converting the Flying Scotsman to DCC

Postby dazamccoy » Tue May 15, 2018 7:10 pm

Do you know of any guides? It all seems very hit and miss.

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RAFHAAA96
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Re: Converting the Flying Scotsman to DCC

Postby RAFHAAA96 » Wed May 16, 2018 12:20 pm

https://tonystrains.com/download/BEMF_PID_Intro.pdf gives the gist of it, Especially the three graphs on page 2.
RAF Halton Brat - 96th Entry
http://www.halton96th.co.uk

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Roger (RJ)
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Re: Converting the Flying Scotsman to DCC

Postby Roger (RJ) » Wed May 16, 2018 12:31 pm

dazamccoy wrote:I installed the replacement decoder today and I’m very disappointed by the quality of the soldering to the chip! The green wire was hanging on by a single strand of wire and came away within seconds of handling the chip. All the other connections have very long bits of bare wire dangerously close to one another. Not impressed in the slightest. I had to splay the wires in opposite directions then insert a piece of sellotape to make sure nothing touched.



Theres a good 5mm of bare wire from every contact!!!!


Initially the slow running was very jerky but I did some research and changed CV151 = 255 and CV152= 1. This sorted that and I now have very nice slow running.

The only remaining problem that I have is... The loco seem to reach its top speed about half way up the speed scale. I have tried changing between 14/28/128 and is the same for each. Once I go faster the loco stops (the sound continues so it's not an electrical problem) then starts again but seems to reset where zero is in the speed scale.

It's easier to watch a video. I'm using a Bachmann Dynamis Pro. I have another loco with a DCC concepts 6 function decoder which works flawlessly.

https://youtu.be/dDe9QRs0O1o


Was that's new decoder?
If at first you don't succeed - cheat
Anyone who is willing to stand for political office isn't fit to be in political office

Rog (RJ)

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dazamccoy
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Location: Moira, Northern Ireland

Re: Converting the Flying Scotsman to DCC

Postby dazamccoy » Wed May 16, 2018 1:17 pm

Yes. That’s the new replacement TTS decoder.


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