faulty motors

[SMR248]

Daedalus, please give us all the benefit of your superior knowledge and give us a more detailed explanation in simple language that we can all understand. I suspect that you can't...

[Daedalus]

I thought I was already over simplifying. Once you start winding wire in tight coils and applying voltage you create magnetic fields and the coil is said to be an inductor and has inductance mesured in Henrys usually mH. Once you start adding cores, magnets and rotation it gets very difficult to calculate.

It is pointless just measuring the resistance with a multimeter and implying anything unless it is O/C and you can assume it is a duff motor.

Otherwise you have to rely on Hornby or their suppliers to have done their maths.

[ColinB]

Yes you right Daedalus but you can use Ohms law to get a rough indication of the stall current, I am sure years ago it was one of my lab experiments on a very large dc motor. Some of the electrical descriptions I have read on these two threads I find amazing. The thing that does intrigue me though is how are they getting blown up, the only way I know to blow them up is to stall them or put too much voltage on them. AC seems to be able to kill them but generally the loco doesn't work, it just buzzes. Hornby don't use coreless motors as far as I know, so it is not that. Unless of course there is just a bad batch, they are Chinese and from Hornby, both of which have dreadful Quality Assurance.

[SMR248]

Daedalus,

Ok, so what you're saying is that it's complicated. No doubt it is but sometimes to understand a problem you have to simplify it a bit. I still believe that when a loco is running at more or less constant speed (no sudden changes in speed, no starting currents, no stalled currents) then Ohm's law is good enough to understand the relationship between voltage and current.

[SMR248]

Colin, you just mentioned Hornby and quality - I think you're in trouble now... (not from me)

On a large electric motor (45kW, I think) the locked rotor current was approx 7x the starting current, which in turn was more than the running current. In locked rotor condition it would take about a minute to burn out the motor. In comparison these motors are tiny so they won't last long if they're locked solid...

On the other hand I've had some problems with Fleischmann n scale motors. These started by smoking so you get some warning but they have proper carbon brushes and are open framed. Thinking about it, this might have been oil on the commutator but they were open rather than closed so you get some warning...

[ColinB]

No SMR248 you can't, you are into Flemming's laws if I remember rightly. As I said before the only time you can use it, is for the stall current. Either way, none it it matters in this instance, you put the loco on the track and it draws what current it needs. I am at a loss to figure out what is blowing them up, track layout definitely shouldn't, perhaps a better solution is to ask Hornby.

[ColinB]

Yes SMR248 you are right about the stalled motors, I watched Sam of Sam's Trains demonstrate how to burn out a Hornby 0-6-0 motor, even he was surprised how quickly it melted. As to Hornby and quality, there is no secret there there are loads of posts about the lack of QA on their models that is why Sam has a field day, it is very difficult to do remote QA. The Chinese think 10% failure rate is good. Years ago when I first started in Engineering you would test a part for ages to see how long it lasted, very few people do that anymore. All of this brings it back to something must be getting stuck in the loco, causing the motor to fail.

[Daedalus]

@SMR248

V=IR + E where E is the back-emf. So we can work out the value of E by instantaneously measuring V and I but how do we know the value of E is correct or the motor has a problem? All we really know about E is it is proportional to the speed of rotation, everything else is motor design.

[96RAF]

Yes SMR248 you are right about the stalled motors, I watched Sam of Sam's Trains demonstrate how to burn out a Hornby 0-6-0 motor, even he was surprised how quickly it melted. As to Hornby and quality, there is no secret there there are loads of posts about the lack of QA on their models that is why Sam has a field day, it is very difficult to do remote QA. The Chinese think 10% failure rate is good. Years ago when I first started in Engineering you would test a part for ages to see how long it lasted, very few people do that anymore. All of this brings it back to something must be getting stuck in the loco, causing the motor to fail.

 

 

Part of my job in a previous life was to monitor reliability of aircraft systems and components. There was a rigorous ISO QA approval system invoked at any sub contract manufacture including 100% then batch checking then supplier trust.

Regardless thru’ life we collected in service failure data, made analysis and recommended maintenance adjustment and if necessary lifing of items.

Failure rates typically followed a bath tub curve where initially many items would fail - infant mortality/burn in failure - then quickly dropped to a predicted level for failure until end of life when the failure curve went exponential again.

I doubt any of that happens in the hobby industry.

 

 

[SMR248]

Colin, you've really done it now - you've just mentioned S*m. I was referring back to the start of this Tt120 forum when any mention of QA or, worse, S*m, caused a lot of upset.

I don't think that S*m is quite as daft as he pretends to be but he certainly seems to annoy a lot of people!

I agree that Hornby are probably relying too much on the Chinese factories but, unfortunately, that seems to be how things are now.

[96RAF]

I was thinking of having Sam 🤡 added to the profanity filter 😵‍💫

[SMR248]

If it's true that the average person who buys an electric drill only ever uses it for a total of half an hour then perhaps it's also true of the average Hornby loco?

On that basis Curly is doing quite well...

To be honest I've used my drills much more than my trains. It's time to change that - just one last baseboard...

[Fishmanoz]

Curly, RAF has hit the nail on the head here with his bathtub curve but not in a way that will help you. Unfortunately, the fantasy index in these topics often follows the bathtub curve:

• initial high index as the OP provides insufficient detail
• settles to a low level as detail supplied and, usually, a solution found. Not so here.
• as the thread gets longer, posters stop reading the thread and the detail/evidence supplied in it, run out of useful ideas and the index rises again.

So to those trying to help, could you please read what has been said about mains spike suppression, use of two different controllers, both almost new, track voltage and polarity testing and isolation, and occurrence in different locos on multiple occasions intermittently.

And to Curly, the only suggestion I have left is that you lockup the layout leprechauns at night please. The ones putting their spanners in the works and jamming the motors.

To the mods - nothing useful happening here, threadlock time. To Rob, I’ll tell you a bathtub curve story separately, not always what they seem.

[Daedalus]

Surely people can discuss what they want on the forum. That someone has the arrogance that they should be able to dictate what is worthy of discussion and it will be complied with is appalling!

[LTSR_NSE]

Surely people can discuss what they want on the forum.

 

 

Nope - only topics/language/content that Hornby deem appropriate & in compliance of the rules, is allowed.

Furthermore unless the initial topic is opening/inviting general discussion (& especially if it is a request for help) - then off-topic discussion is naturally unhelpful to the OP.

[Daedalus]

So in what way does discussion of motor failure not fall into the topics that may be discussed?

The trouble with this forum is a clique thinks it should exist solely as their private mutual admiration society.

Why is 96RAF constantly posting about his boring RAF reminicences anything to do with a Hornby forum?

[LTSR_NSE]

Personal criticism of a moderator (who hasn’t even suggested that your posts aren’t in compliance) really seems the most productive way of getting your point across? 🤦‍♂️

[ColinB]

Virtually everything in life follows the bathtub curve, unfortunately even the life of a human being. Either way, I would really like to know what is killing the shunter motor. I suppose the thing is, it is obviously a design fault, as unless the user is doing something silly it should not be possible to break it easily. I imagine that the user doesn't really want to send back again because I know I would get embarrassed doing it, but it sounds like that is what they are going to have to do. It flags up to Hornby that there is an issue with these models, as nothing I have read in the posts says that they are abusing the loco.

[Silver Fox 17]

I suppose the thing is, it is obviously a design fault, as unless the user is doing something silly it should not be possible to break it easily.

 

 

I would like to know what design fault you think it is?

The owner has had 3 locos and burnt out 6 or 7 motors and melted some plastic bodies yet out of the thousands (maybe hundreds of thousands) sold of locos no one else has had this issue.

Some people have had a motor pack in but not the frequency as from one individual. Certainly I have never heard of anyone having a melted body.

I have 40+ locos and not had one motor issue. I know someone with more than me and only had a couple of noisy motors, certainly nothing like what is happening here.

With all the successful running locos around the world I cannot see there is a design issue in this department.

 

 

[96RAF]

@Silver fox.

This will end up as expected when we finally get to the bottom of it. When fault finding look for the common denominator, and in the case of serial failures it is never usually the failed items at fault, except in the case of a genuine batch problem and this is definitely not in that category.

[ColinB]

Well Silver Fox 17 I am not a Hornby Engineer so I don't know what the design fault it is. What I do know is that when you make a product it is meant to withstand normal use. Now from all I have read all the guy has done is put it on the track and run the loco. It may be his controller gives out 24 volts that would definitely kill them but then he would notice that as they would run considerably faster. I suppose if it was PWM then it might happen but you still have to get enough energy into motor coils to burn them out. The favorite is the gearing gets stuck and before the user notices the motor has burnt out. As I said before we know how quickly these motors can burn out and I have seen a dcc decoder fry on a point where the loco got jammed because the back to back spacing was wrong. It could be the motors, as I said I found that Railroad Pendolino motors were extremely bad, one in three failures is not good. The only person that will find out is Hornby, if they have to replace enough motors, they will look a little deeper into their product and find out how it can fail.

[Hobby11]

I agree with that (RAF's comment above, new post arrived too quickly!), hence I suggested the back to basics single loop solution. I know Curly said that since he'd done that he hadn't experienced any more issues, is that still the case?

Someone did ask many moons ago about his location as well, connected with the "spike" suggestion, TBH an electricity spike is not something I've ever had here in the UK but it could be if he's overseas or somewhere remote, did he ever clarify that as well?

[Silver Fox 17]

ColinB,

Well tell me why no one else has burnt out that amount of motors individually and melted bodies?

As I mentioned there are literally thousands running without issue.

Maybe, and I say maybe, there does seem to be far more issues with DCC models but not just specific to this problem. I don't know if these are DCC or plain DC analogue loco issues.

Having reread the start these do seem to still be analogue so the DCC issues will not apply.

[ColinB]

All I can do is advise, I have been down this route many times on this site, so I am not going to argue. I doubt it is a "mains" transient because sitting in between is a piece of relatively sophisticated electronics namely his controller. Long gone are the days of just a transformer and bridge rectifier, so generally the controller electronics would go first. I doubt he lives next door to an industrial arc welder that can generate those sort of transients. I would be interested to know though when the fault gets fixed.

[Fishmanoz]

I am none the wiser on this problem but I have read the thread and know what it isn’t.

Colin, why would you suggest an 08 design fault when Curly’s issues are also in an Easterner?

Colin and Hobby, have you not noticed that Curly has connected his controllers via a suppressed extension cable.

Hobby, would it not be more useful if you read what’s in this and the related thread rather than asking others to tell you?