Very fast running at slow throttle

[Darius43]

Hello,

 

I recently acquired a Hornby Javelin and on fitting a decoder the motor runs very fast straight from the off - even with a fraction of the lowest throttle setting.

 

Different decoders make no improvement.

 

I am using a Roco Z21 controller.

 

Any help or guidance most appreciated.

 

Cheers

 

Darius

Edited September 14, 2017 by Darius43

[34theletterbetweenB&D]

Were you able to successfully change the decoder address on programme track? (The safe test for a correct decoder installation.)

 

 

Reason for asking this is that what is described is typical for one of the pick ups still having a direct connection to a motor terminal. This will typically damage a decoder pretty swiftly, so try the programme track address change if you have not already done so.

 

 

If you have successfully made an address change to the installed decoder, then you may have a very low current draw motor in the model, and need to reduce CV2, (start volts) to a smaller value. Sometimes it is a matter of finding a decoder which has enough adjustment in CV2 to get a slow start: the Zimo and CTE brands are particularly good in this respect which I turn to when faced with a motor that starts on a breath of current. There are doubtless others, I cannot claim to have sampled every decoder brand going!

[shibushe]

Have had similar problem recently. On seeking advise from the decoder supplier he suggested this.

Turn the Loco the other way round, see if it still does it.

It did.

This proved in my case that the decoder was faulty. Its replacement was fine.

May not be your solution, just thought I would mention it.

[Darius43]

Have had similar problem recently. On seeking advise from the decoder supplier he suggested this.Turn the Loco the other way round, see if it still does it.It did.This proved in my case that the decoder was faulty. Its replacement was fine.May not be your solution, just thought I would mention it.

It does this in both orientations, however, the decoder works fine in another loco.

 

Cheers

 

Darius

[Darius43]

Were you able to successfully change the decoder address on programme track? (The safe test for a correct decoder installation.)

 

 

Reason for asking this is that what is described is typical for one of the pick ups still having a direct connection to a motor terminal. This will typically damage a decoder pretty swiftly, so try the programme track address change if you have not already done so.

 

 

If you have successfully made an address change to the installed decoder, then you may have a very low current draw motor in the model, and need to reduce CV2, (start volts) to a smaller value. Sometimes it is a matter of finding a decoder which has enough adjustment in CV2 to get a slow start: the Zimo and CTE brands are particularly good in this respect which I turn to when faced with a motor that starts on a breath of current. There are doubtless others, I cannot claim to have sampled every decoder brand going!

Making an address change is problematic and your second comment ref. the direct feed may be the issue at hand. It is all wired up to the pcb, which is where the problem may lie. I am thinking of wiring a separate decoder harness to the motor and using another decoder in the pcb to operate the lights. Not ideal but I have no idea what the pcb is doing with respect to the motor feeds.

 

Thanks to both for your help.

 

Cheers

 

Darius

[34theletterbetweenB&D]

If you physically break the motor supply connections between PCB and motor terminals, and successfully perform a check that confirms that both terminals are then fully isolated from the rails, there will be no need for a second decoder. Cut the orange and grey wires near the plug, and connect these to the motor terminals. That takes the PCB out of circuit as far as motor supply is concerned, motor supply is from the decoder alone.

 

Of course if you find that both motor terminals are not isolated from the rails even with the connections from the PCB broken, then there's the trouble. The problem described isn't necessarily on the PCB.

 

Out of curiosity, why is making an address change on programme track problematic?

[Darius43]

If you physically break the motor supply connections between PCB and motor terminals, and successfully perform a check that confirms that both terminals are then fully isolated from the rails, there will be no need for a second decoder. Cut the orange and grey wires near the plug, and connect these to the motor terminals. That takes the PCB out of circuit as far as motor supply is concerned, motor supply is from the decoder alone.

 

Of course if you find that both motor terminals are not isolated from the rails even with the connections from the PCB broken, then there's the trouble. The problem described isn't necessarily on the PCB.

 

Out of curiosity, why is making an address change on programme track problematic?

Reconnected the motor wires to the 8 pin terminals - no change.

 

All of the decoders that I have tried work fine on another loco.

 

I suspect it is a poor quality Hornby motor - it sounds like a bucket of bolts. It's the same sort that they use on the ex Lima Class 87.

 

No idea what the CV programming issue is. CV2 is set to 1 when I checked it on the other loco.

 

Cheers

 

Darius

Edited September 14, 2017 by Darius43

[Darius43]

By chance I have a spare Hornby Javelin motor that I had earmarked for an MTK GWR twin railcar kit. I have wired this motor up to an 8 pin harness and am running it in on a rolling road. It runs better than the motor in the loco but still sounds like a bag of spanners. I have lubricated the gear train and the axle bearings.

 

It needs running in so I wil, leave it for now.

 

Cheers

 

Darius

[Darius43]

I decided to junk the awful Hornby motor bogie and shoehorn in a spare Bachmann motor and bogie

 

 

 

 

 

Plan is to attach a DCC harness to the new motor.

 

Cheers

 

Darius

[Phil S]

While probably not the reason for your failure - but one which caused a working decoder to fail during test running - with a Hornby motor bogie of the modern type: they have the 2 motor terminals close together and in close proximity to the magnets ......Unoticed;  a trimmed component lead (magnetic) was attracted to the bogie by the magnet, and shorted across the motor terminals, destroying the decoder - Since then I have taken the precaution of covering the motor terminals with either insulating tape or plasticard.  Prevention is better than cure - even if the decoder had its US manufactirers 'goof proof' warranty ...  returned/exchanged via the UK dealer.  With all-black factory wiring, there is always the risk of an error during assembly:  Hornby tenders have been wired the opposite way to their locos in the past (hopefully, only  in the past)

 

As Dutch Master advocated - using a Multimeter is always the best 'prevention is better than cure'  - Some Hornby models have had the pickup wires from differing wheels soldered to different pins   (ie not just the std pair) = no problem on an analogur test, but an instant short in DCC mode!  Other failures (various makes) can occur when the pins are pushed in fully, and on the other side, make contact with metal - again a piece of insulating tape or plastic is a good preventive measure .

The most confusing I have had was a mehano iCE - 'dcc ready' with 8 pin socket - which ran in one direction only ..... in one of the pickup bogies, thay had wired the interference suppresion capacitor - so it was before the  plug, and not after it !!

Edited September 14, 2017 by Phil S

[Nigelcliffe]

I decided to junk the awful Hornby motor bogie and shoehorn in a spare Bachmann motor and bogie

 

 

 

Lots of brownie points for cutting the model and fixing the problem with new motor and bogie.

 

Now some engineering stuff - it will run massively better (quieter, smoother, lower power) if you can get the drive shaft straighter. The pictures show the shaft at quite a large angle.  Ideal is a straight line from the gear tower through the middle of the motor, so the only angle comes when the bogies turn on curved track.  

So, look at turning the motor cradle upside down, or even doing away with the motor cradle and just fix the motor to the floor.  Or, if you can, cut away into the floor to get the motor lower.  Fixings could be a strap around the motor (couple of bits of wire around it could do), or could be flexible adhesive such as bathroom sealant (can peel it away if things go wrong). 

[Darius43]

Thanks Nigel - I will re-align the motor and drive train - this will need more surgery. My home made driveshaft is not very satusfactory so I have ordered some ready made ones.

 

Cheers

 

Darius

[Darius43]

I have replaced my home-made driveshaft with one from a Bachmann Class 47 and lowered the motor to straighten the transmission path.

 

All running smoothly and quietly - well a whole lot quieter than the Hornby bucket of bolts anyway.

 

 

 

Thanks to everyone for the helpful advice.

 

Cheers

 

Darius

Edited September 24, 2017 by Darius43