wierd problem when cold

[WIMorrison]

I have a loco, Liliput 142100 loco which is DCC ready and I have fitted a Zimo MX618N18 and it has started performing rather oddly when cold.

 

When I switch the layout on this loco causes a short on my NCE-EB1 which means it is drawing more than 2.5a, yet once it is warmed up by running on DC for 5 mins it will perform correctly for the rest of the day. What I do notice though is that does appear to hunt slightly - running freely, but occasionally sounding like it is being held back.

 

I cannot work out what the issue is, the wheels all rotate freely, but I can't check anything in the motor as it is a sealed can.

 

I am confused as it used to run perfectly, in fact the best loco I have until about a month ago.

 

Any ideas or suggestions?

 

[smokebox]

Thickened grease or oil in the gears?

[Guest Mancunian]

1 hour ago, WIMorrison said:

I have a loco, Liliput 142100 loco which is DCC ready and I have fitted a Zimo MX618N18 and it has started performing rather oddly when cold.

 

When I switch the layout on this loco causes a short on my NCE-EB1 which means it is drawing more than 2.5a, yet once it is warmed up by running on DC for 5 mins it will perform correctly for the rest of the day. What I do notice though is that does appear to hunt slightly - running freely, but occasionally sounding like it is being held back.

 

I cannot work out what the issue is, the wheels all rotate freely, but I can't check anything in the motor as it is a sealed can.

 

I am confused as it used to run perfectly, in fact the best loco I have until about a month ago.

 

Any ideas or suggestions?

 

 

How sealed is the motor...are you able to remove the brushes and springs or at least rinse the motor with IPA..??    Process of elimination... :-)

[WIMorrison]

Thanks - both good suggestions, unfortunately though the second is a non-starter as the motor is well and truly sealed , I think I will take electrical circuit board out (though that isn't a simple process either)  and have a good look at the gearing, though from the outside that looks quite well sealed also - certainly both ends are covered by a well fitting plastic covers which, as they went on, must come off - somehow.

[jamespetts]

Test with a multimeter in continuity mode with DCC chip removed and a blanking plate in place instead?

[WIMorrison]

James - I am not sure what this would prove as the motor runs when the existing setup I.e with MX618n18 in place when the wheels are powered by DC. This suggests that me that there is continuity and also once the loco is warm is runs correctly in DCC?

[34theletterbetweenB&D]

3 hours ago, WIMorrison said:

...When I switch the layout on this loco causes a short on my NCE-EB1 which means it is drawing more than 2.5a, yet once it is warmed up by running on DC for 5 mins it will perform correctly for the rest of the day.

 

You know that the current draw from cold is excessive. Something impeding that mechanism when it is cold, and the cold lubricant won't be helping it. The motor is OK electrically because it is surviving the task of getting the cold mechanism going until it frees up somewhat; but it still doesn't run perfectly:

 

3 hours ago, WIMorrison said:

...What I do notice though is that does appear to hunt slightly - running freely, but occasionally sounding like it is being held back....

That suggests that the problem is still present enough to have some intermittent effect even when warmed up.

 

I'd be looking inside at the mechanism before it has been run, disconnecting the motor to assess it separately from the rest of drive train to try and assess whereabouts the drag is located in the mechanism. Not knowing the specific mechanism design I don't have a clue what is most likely: have you tried websites where there are numbers of Liliput users?

 

[NIK]

4 hours ago, WIMorrison said:

I have a loco, Liliput 142100 loco which is DCC ready and I have fitted a Zimo MX618N18 and it has started performing rather oddly when cold.

 

When I switch the layout on this loco causes a short on my NCE-EB1 which means it is drawing more than 2.5a, yet once it is warmed up by running on DC for 5 mins it will perform correctly for the rest of the day. What I do notice though is that does appear to hunt slightly - running freely, but occasionally sounding like it is being held back.

 

I cannot work out what the issue is, the wheels all rotate freely, but I can't check anything in the motor as it is a sealed can.

 

I am confused as it used to run perfectly, in fact the best loco I have until about a month ago.

 

Any ideas or suggestions?

 

Hi,

 

If its drawing too much current as soon as the DCC system is switched on but the loco is not being given speed steps above zero then it is not likely to be the mechanism that is causing the problem.

 

One way to check that the loco has been given speed step zero is to warm it up on DC, give it the minimum speed step it will move at, then set the speed step to zero, check it has stopped moving then turn off the DCC system and repower it. If the EB1 trips it is unlikely to be the mechanism since the decoder should not be switching on the motor at all.

 

Can you measure the current draw when you start to apply DC (ideally test this by applying 12V DC immediately rather than turning up the control knob). Can you measure the DCC current (you have an NCE EB1 - do you have an NCE Power Cab as your command station?).

 

Regards

 

Nick

[jamespetts]

2 hours ago, WIMorrison said:

James - I am not sure what this would prove as the motor runs when the existing setup I.e with MX618n18 in place when the wheels are powered by DC. This suggests that me that there is continuity and also once the loco is warm is runs correctly in DCC?

 

The idea is to test for where the short occurs when cold.

[WIMorrison]

James, there isn't a short per se, the motor runs on DC when cold and DCC when warm, it is on DCC that the cutout, which trips at 2.5a, operates when the motor is cold. If there was no current limitation, or if it was higher, it may be that the loco would run on DCC also from cold (I might set the EB1 to a higher current and see what happens).

 

We know that there is continuity in the circuit because if there wasn't then it wouldn't run at all. 

 

 

[WIMorrison]

7 hours ago, NIK said:

Hi,

 

If its drawing too much current as soon as the DCC system is switched on but the loco is not being given speed steps above zero then it is not likely to be the mechanism that is causing the problem.

 

One way to check that the loco has been given speed step zero is to warm it up on DC, give it the minimum speed step it will move at, then set the speed step to zero, check it has stopped moving then turn off the DCC system and repower it. If the EB1 trips it is unlikely to be the mechanism since the decoder should not be switching on the motor at all.

 

Can you measure the current draw when you start to apply DC (ideally test this by applying 12V DC immediately rather than turning up the control knob). Can you measure the DCC current (you have an NCE EB1 - do you have an NCE Power Cab as your command station?).

 

Regards

 

Nick

Nick

 

it is only when I give the loco a command to move that the excess current draw happens - when it is sat on the layout without any command telling it to move nothing happens, It just sits there reacting to commands telling it to switch the lights off and on.

[Phil S]

It is behaving as if the motor has developed a short ... Possibly only one coil, which is temperature sensitive ( although it easier to imagine an open circuit which closed when expanded by the warming effect of other coils ) ....

 

A dc supply would overlook the occasional problem of a short term overload which a self protecting DCC decoder would not.

( .....But as you are saying that it works VIA the DCC decoder when given a DC power feed eg from a battery ??? Or DC controller ??? Or dc power supply ???     ......the only difference is the applied voltage and therefore maximum current which can be taken ....

 

If testing with a 9V battery    a max of about 7V to the motor.     Volts dropped by the internal resistance of the battery if a large current taken.

 

A smooth output DC controller variable from processor turn-on at maybe 5V (  heck with the directional lights and zero speed) .....up to probably 12V (10Vmotor), with maybe a 1A limit?     

 

A DC power supply ....eg a maplin bench unit with volt and current display and current limit is a very useful tool for checking a motor .....especially one not used for a while***.  Anything from 0-20 !

 

Whereas with DCC control  the full voltage and current capability IS there all the time ....and is showing when the motor is commanded to move.

 

You have checked both directions on DC and DCC ???? ....just in case it has blown one side of the motor h-bridge 8-(

 

Regrettably I don't think you have anything to lose by dismantling to extract the motor and test it externally. ....hand rotating with a Meter may show a coil failure or reveal a mechanical snag.

 

*** in my converting Macklin ac 3rail to DC/DCC recently, with locos never run for 20 years... Stiff at first ( and completely seized zeppelin aerotrain ).  Which all benefited from flushing and cleaning/ relubricating.  Current demand dropped from maybe 0.8A via 0.3A to 0.2A when run in a bit.

Edited November 2, 2019 by Phil S
Is to if. Meyer to meter. 8-)

[NIK]

2 hours ago, WIMorrison said:

Nick

 

it is only when I give the loco a command to move that the excess current draw happens - when it is sat on the layout without any command telling it to move nothing happens, It just sits there reacting to commands telling it to switch the lights off and on.

Hi,

 

In which case it may be a mechanical problem - my first thought is that the drive from one end of the motor to the worm is occasionally slipping. When the slip occurs one bogie locks up and the motor tries to drag the loco along so the current will rise a lot.

 

I don't have any current consumption data for working Liliput loco and I've never measured the current consumption when a bogie locks up but I could hear the motor humming.

 

Regards

 

Nick

[WIMorrison]

I have spent a good part of the morning taking this loco to bits (wasn't as hard as I thought it would be :)) and I took the grease that was on the sides of the worm gear casings and reapplied it to the worm gears and have every bearing I could see a dab of oil. Needless to say I saw no difference on DC  

 

Reassembling wasn't as straight forward as taking it apart because I could seem to get all the parts to sit in the right places whilst i put the next bit in to be able to screw bits down and the getting the top on again was painful because I hadn't seen a wire was crossing a mounting point - hey ho, back together again and running on DCC but as it is warm from DC running I won't know if I have solved the issue until tomorrow when it has had chance to cool down.

 

Fingers crossed.

[Andymsa]

Hi iain 

 

been following this post and a thought occurred to me. If you take it apart again are you able to test for insulation resistance of the motor windings as my money is on some sort expansion or the opposite in this case as there must be fractions of millimetres of movement in the windings as they warm up and cool

 

andy

[WIMorrison]

an update

 

Something I have done in the oiling has caused the issue to manifest itself more often now and the loco will stop randomly driving around the track causing a 'short' which means that the EB1 cuts the power off then after it resets loco will start and run again for a random period.

 

When i does stop if I lift it from the track and apply DC voltage then it will run without issue. I don't see it as a motor issue now as I have just reprofiled the speed and the slowest it will run is 0.4kph! (top speed is 67KPH, but that is limited by  the ZIMO CV57 setting)

 

Does anyone think it could simply be a chip problem? (Zimo MX632 which is  not as I said earlier) - I am at a loss as to what else as between the motor and the track it is the only thing i can see that would cause an issue and the motor runs sweetly on DC.

[WIMorrison]

I have decided it is actually the decoder which is at fault as when i stripped the loco down (again  ) to check that there was nothing wrong I connected a MX617N direct to the motor and the motor has run perfectly for 30 mins in each direction, never missing a beat.

 

I rebuilt the loco and connected the motor and plumbed the MX617N to the NEM660 pins and ran it, again without any issues - but no lighting as MX617N doesn't have enough functions

 

As far I am concerned this is fairly conclusive and as the decoder is less than 1 year old it is back to supplier for replacement.

 

Fingers crossed

[34theletterbetweenB&D]

10 minutes ago, WIMorrison said:

... but no lighting as MX617N doesn't have enough functions ...

Keep this in mind, as it could be significant. If whatever decoder you next install has enough functions to control the lighting and the problem returns...