Super Mini Size Motorized Chassis TU-KOPPEL A - Tsugawa Yokou #14036 (N scale)

[HLT 0109]

I bought the motor bogie identified above, for a DCC layout i am building and then discovered that it is designed to run on a 4 volt system.  Clearly I cannot run it as it is, using Power Cab but I have seen a video of someone fitting a resistor in the power supply to the motor of this bogie, for a DC 12v system but I don't know how to work out what resistor would be required for my DCC system (I don't remember the video giving the rating for the resistor used in the 12 volt DC system).  Can anyone please tell me what I would need? 

 

A separate issue which may prove impossible to overcome - the wheelbase of the bogie is 10mm - the frogs on two of my points are about 13mm long, and there may not be enough room for a stay alive as well as a DCC decoder in the loco body.  Perhaps I am seeking the impossible but I don't want to give up without giving it a try.

 

I should appreciate advice - many thanks,

Harold.

[Phil S]

If you have a multimeter you can make the measurement yourself ....aided by you having the motor in front of you 8-)

A typical 00 motor is about 10 -20 ohms ..... If measured on a meter and rotated by hand, you will see the value vary as the next coil is switched in.

V=IR tells us that.  12volts = 1.2 Amps x  10 ohms.   12V = 0.6 Amps x 20 ohms.    12V = 0.3 Amps x 40 ohms.

 

If you had a multimeter and 4 to 5 Volts in batteries you could also measure the current of the new 4V motor ..... Perhaps only 1/4 Amp (250mA)

Guessing from these calculations  I would suggest trying a 33 ohm resistor in series ... Perhaps reducing to 27 ohms ( 'preferred values' avaíable )

The Power Rating for these resistors comes from P=IV.   So P (watts) =  1/4 A x  ( 12- 4 ) volts across the resistor = TWO WATTS.

 

Another method is to limit the 'maximum speed'  using CV 5 to about 1/3 of the default maximum.  Perhaps 85 instead of 255.

With high frequency 'silent drive' from the decoder, the pulses will be averaged and smoothed by the iñductance,

 

Perhaps a combination of the 2 approaches ....the resistor providing some protection against an accidental reset of the decoder, and the lower Vmax reducing the possible the need to drop so much across the resistor

Eg 6V  Vmax = half default ( 127 instead of 255). and  P=IV.

P =  1/4A x ( '6' - 4 =2V across resistor) = 0.5 Watts nstrad of 2watts for the resistor.

A worthwhile reduçtion

 

 

Edited April 26, 2019 by Phil S
adding combined option...

[Nigelcliffe]

As Phil implies, its heat (watts) through the resistor which is the problem. A 2W resistor is fairly fat, and the heat still has to go somewhere. 

 

Some decoders have more than CV5 available to turn down the apparent voltage (by altering the PWM pulse widths).  This is likely to be more effective. 

Or, there are a handful of decoders for low voltage motors - I know there is an example in the CT Elektronik range.

 

Over-volts to a motor isn't usually a problem, so long as its not stupid.  There are plenty of small 2mm scratchbuilds running around on nominally 12v supplies (analogue and digital), yet using motors rated at 8v, 6v and even 3v.     The danger is in stalling a mechanism, then the heat (and damage to the motor) happens quite quickly.

 

 

- Nigel

 

[HLT 0109]

Thank you Phil & Nigel - very informative indeed.  I will see what I can do.  I would need to use the smallest available decoder and thought of usding the Zen Nano 2 function from DCC Concepts (ZN8H).   I see it is supplied with a Stay-Alive - I wonder if that has sufficient capacity to take the bogie over a dead frog.

 

Thanks again,

Harold.

 

 

[Phil S]

I've just fitted a Zen 60 /68 into the Heljan L&B 009 Manning Wardle ... with the stay alive diagonally across the cab floor below 'waist height'.

Not had time to test it across pointwork yet.

[HLT 0109]

18 minutes ago, Phil S said:

I've just fitted a Zen 60 /68 into the Heljan L&B 009 Manning Wardle ... with the stay alive diagonally across the cab floor below 'waist height'.

Not had time to test it across pointwork yet.

 

Interesting!  I look forward to reading the results of your test in due course

[TWG]

15 hours ago, HLT 0109 said:

Thank you Phil & Nigel - very informative indeed.  I will see what I can do.  I would need to use the smallest available decoder and thought of usding the Zen Nano 2 function from DCC Concepts (ZN8H).   I see it is supplied with a Stay-Alive - I wonder if that has sufficient capacity to take the bogie over a dead frog.

 

Thanks again,

Harold.

 

 

 

If you want the smallest possible decoder I suggest that you look at the CT Elektronik DCX65, which measures 6x5x1.8mm (compared with 15x7x2.7 for the Zen Nano). This is the decoder for low voltage motors mentioned by Nigel Cliffe above.  Despite its astonishingly small size, it has a full specification (see www.tran.at) and will withstand a track voltage up to 21V. 

 

A low voltage alternative is the Döhler & Haass P006A. 

[HLT 0109]

That's amazing TWG.  Many thanks.

 

Does that mean that, If I were to use the DCX65, I wouldn't need a resistor to reduce the voltage - or does the danger of a reset decoder still cause a problem when the motor stalls?

[Nigelcliffe]

The DCX65 is designed for 5v motors, so that is close enough to not be an issue with the models motor rating.

 

CT is a mixed bag.  The decoders are superb pieces of miniature work; much smaller than anyone else makes by a large margin, and with superb motor control of small motors (with the right settings, on very small motors, they're better than Zimo).      But, documentation is patchy, support is patchy, there are rogue versions around which behave badly or fail.   They're used a lot by 2mm scratchbuilders (I've used them for at least a decade).  When they work well, they are fantastic.  But, use them accepting its not like Lenz or Zimo or ESU. 

 

The DCX65 has two solder pads for decoder positive and ground, so a DIY Stay-alive, or a unit like the Zimo SACC16 could be attached (with the caution that I've not tried it on that decoder, so what works in theory applied to the published manual, may or may not work in practise ). 

 

From some testing I've been doing on closely related CT decoder, I'd say that you'll need quite a few of the Tantalums recommended for the SACC16 - just one 220uF Tantalum won't give the run-on you've said you need. 

 

The alternative might be to extend the pickups using some metal skids, but that's a different level of metal-bashing skills. 

 

 

 

- Nigel

 

 

[HLT 0109]

Many thanks Nigel for such a detailed and well-reasoned reply.

 

I calculate that I need a stay-alive that will last for a distance of 5mm (to be on the safe side) at a scale 10mph.  Now, if my schoolboy maths is correct, that requires a stay-alive that will last for one-twelvth of a second - assuming good pickup function by the motor bogie,  I did muse on the possibility of skids as pickups but then realised they would need to follow curved track and not short on points.  Beyond my abilities I think.

 

In order to test the motor bogie I am awating delivery of a switched battery box that will take two AA batteries - I can then see how it works on 3v DC.

 

Harold

[HLT 0109]

After some procrastination, (and failure to get any response through Shapeways from the designer) I took a chance and bought the 3D printed body for my tiny motor bogie - see attached picture for the two elements assembled temprarily.  The gap between the saddle tank and the chassis measures 19mm long x 3.3mm high and the available width is about 15mm - this appears to me to be sufficient to accommodate a suitable voltage reducer and a decoder (eg the voltage regulator shown in this link: https://www.kitronik.co.uk/46113-5v-step-upstep-down-voltage-regulator-input-25v-18v.html and the Zimo MX617N decoder which measures 13mm x 9mm x 2.6mm.  As already pointed out, a smaller decoder is available if necessary.  The motor on the bogie is neaty concealed in the "firebox" of the body.

 

Behind the firebox is the cab space which measures approximately 18mm x 11mm x 13mm high to the top of the firebox casing - I really need to accommodate a driver in the cab too - but I wonder if the space would be sufficient to accommodate an adequate stay alive.  Having had a closer look at the curved points that are the problem, I find that the frog is actually 20mm long so, I need a stay alive to cover (say) 11mm.  Again, my schoolboy maths suggests a time of about 0.25 of a second.

 

Is what I am proposing seem sensible?

 

Harold.

 

Edited July 26, 2019 by HLT 0109
insert a proper link

[HLT 0109]

Just found this old thread:  I wonder how things worked out for Black Sheep?  I realise that my proposed decoder needs to be wired rather 6pin.  There is access through a slot under the tanks to space for the wires.

 

 

[Grovenor]

An alternative would be to build some proper live frog points and eliminate the gaps, track building is not so hard.

Rgds

[Nigelcliffe]

On your first of two posts above, the 5v regulator.   The first problem will be whether the DCC chip actually runs at 5v, its pretty marginal whether it will run.   A stay-alive on that design has advantage of lower operating voltage (5v), but a risk that any small voltage drops over components linking the capacitors to the chip will result in the decoder going below operating voltage.   So, lots of bench tests to find out if it might work, or if the volts are too low.

 

Of the second posting, that might work. 

 

Stay-alive within 18x13x11 mm  could give the required run time. 
Tantalums (16v rated) could yield 9,400uF in the space. But would cost £100 for the 20 capacitors needed.

 

 

I'd favour Keith's "build proper track" approach, rather than adding more electronics to a loco which is already very short of weight. 

 

 

[HLT 0109]

NIgel,

 

Wouldn't the voltage regulator be inserted between the decoder and the motor?  I would like to think I could build suitable points - perhaps someone at the club can help/guide.  Might it be possible to modify the Peco set-ttrack curved points?  I did read a thread on the subject.

 

£100 wouold be a costly solution.  I think I would ignore prototype and permanently attach a short carriage with pickups.

[Nigelcliffe]

The regulator quoted gives 5v constant DC output. It can't handle reversed voltage.  So, useless for controlling a motor (5v in one direction, dead in the other).  Its also pretty much useless for direct inserting between DCC signal and the decoder, but there might be a way of using it there. 

 

There are some decoders from CT for low voltage motors used in T scale.  But supply from CT is erratic, and many UK retailers have given up with the difficulties of working with the company, so you may have to source from Germany or Austria.    But, unless you've got a really high DCC track voltage, I don't see a normal decoder killing the motor.  Your problems will be weight of loco and lack of pickups if persisting with dead frog turnouts. 

 

You might not need 20 capacitors for the run time, but will need something.  Without bench tests its impossible to say how many are needed for the loco in question. 

 

Track building is simple - needs rail, sleepers and you're away.  Or there are turnout kits in N from "FineTrax / British Finescale".    
Hacking Peco turnouts is hard work.  

 

 

[HLT 0109]

Thanks again Nigel.

 

Simpler to avoid a voltage reducer so a CT DCX65 would seem to be the answer (GS Model Supplies in Somerset is advertising it for £37.50) but, if the Zimo MX617F is safe using Power Cab, I might as well save £17.50.

 

Using two AA bateries to power the track, the little unit copes satisfactorily with the electrofrog points, though it has occurred to me that lack of traction could be a problem with pulling coaches.  Perhaps i should stuff some weight into the chimney.

 

Harold.

[RobjUK]

All you need to do is set the maximum Back EMF voltage of the decoder to 4V, or the maximum speed to the level that gives 4V to the motor.

 

Anything connected between the decoder and motor, other than possibly a low value resistor, will mess up the decoders ability to control the motor and properly measure the voltage / back emf from the motor.

 

The input to the decoder can be normal DCC 12 - 15V range without any harm to the motor; just increase the controller speed very slowly while you are setting it up and monitor the motor voltage until you have a suitable maximum speed value set in the decoder.

 

[HLT 0109]

Progress has been made!  I decided to dispense with resistors and stay-alives and opted for reliance on setting the maximum speed in CV5 to 30, which gives an input voltage to the motor of a little over 4 volts.  CV 6 is set to 15.  I was unable to find a CT DCX 65 decoder so have used a Gaugemaster chip that was spare - a young member of my moddel railway club kindly did the soldering for me.  I have made a small coach with pickups that will be wired permanently to the loco and that should get the loco over the dead frogs..  There is however another issue - that of the weight of the locomotive and its distribution.  As can be seen from the attached photo, the cab sits outside the wheelbase and I need to add weight in the boiler; to this end I have bought some Liquid Gravity.  My question is, what weight should I aim for?  It needs to be sufficient to ensure the front wheels remain in contact with the rails and to provide as much traction as possible without straining the motor.  Using rather imprecise kitchen scales, the loco as shown in the photo weighs a mere 10 grams and I have to press the loco down on the rails on the test track in order to read CVs.

 

Would 25 grams of Liquid Gravity in the boiler be a sensible amount?  I have been unable to find the weight of of RTR 009 or N Gauge 0-4-0 locomotives.

 

Thanks,

Harold.

 

 

[Phil S]

If you run the loco on dc, via the decoder, you should be able to measure the current the motor is taking - and as you add the load it will increase..   if you have the motor spec you should be able to remain under its limit .... don't forget to allow for an incline or training load

[HLT 0109]

Thanks Phil.  I wasn't able to do that but I managed yesterday to get about 15 grams of Liquid  Gravity into the forward area of the boiler and ran some dilute PVA in afterwards.  I did it by drilling out the little mound on the boiler top and setting the loco about 45 degrees to the vertical on its nose.  By carefully drilling the nozzle of the bottle to match said hole, I was able to "squirt" the Liquid Gravity in gradually without spilling any!  I was concerned about getting the granules and/or the glue into the motor or the mechanism - the motor stands vertically in the firebox.  This morning the loco wouldn't work at all and I feared the worst.  However, I discovered that the side plate on each side to which the pickup wires are soldered (visible behind the wheels in the picture) were loose and this was affecting electrical continuity.  Each plate is fixed in place by a single screw at the top, between the wheels and I was able to tighten them with good effect.  The loco now runs satisfactorily until it reaches the dead frogs and readily triggers the reverse loop module.  It remains to be seen what haulage power the loco has but I don't want to attach the pickup coach until I have added some detail to the loco and painted it.  If necessary, I think I could get more weight into the boiler - or I could put some weight in the gap between boiler and frame.

 

Harold.