Help required to diagnose poor running Hornby Class 50

[alexross42]

Hi,
I'm looking for some help/advice with a Hornby Class 50 that has recently started running very poorly so all ideas are gratefully received!

The loco had been running fine for approx a year and then suddenly started juddering/struggling and became unresponsive to commands, sometimes taking a few seconds to apply changes sent through the controller. Also, it's speed capability now seems quite limited (at max it reaches about step 35 out of 126).

 

I've checked everything I can think of - there is no excessive build up on the gears, nothing caught within any mechanism, no dirt on the wheels and the contacts are fine. I've had the bodyshell off and swapped out the DCC chip but the behaviour is the same. One thing I have noticed is that both the chips I've tried get very hot during running, to the point where I could feel the heat through the roof of the body and the chip itself can barely be touched.

Is there anything else that's recommended to check before I disengage the worm gear and run it as a 'dummy' in some double-headed consists?!

 

Many thanks,

Ross

[pheaton]

sounds like the motor is faulty, there not too difficult to swap out, give that a try before you consign it to dummy status

[johnb]

How old is the loco and how much work does it do?

What about checking all the bearings on gears and motor for gunging up, if it is grease lubricated then that can become very sticky. So it's a strip down clean off all the gear bearings and relube with a fine lube.

 

[Clagsniffer]

I had bother with the rotating fan on mine, removed the mechanism and worked fine after. Worth a shot.

[royaloak]

Which one is it, some suffered from mazak rot of the chassis.

[pheaton]

As far as i know the mazak rot was confined to the cab floor plates on the 50s i wasnt aware of them suffering an iffy chassis.....

 

 

[34theletterbetweenB&D]

2 hours ago, alexross42 said:

The loco had been running fine for approx a year and then suddenly started juddering/struggling and became unresponsive to commands, sometimes taking a few seconds to apply changes sent through the controller. Also, it's speed capability now seems quite limited (at max it reaches about step 35 out of 126).

 

I've checked everything I can think of - there is no excessive build up on the gears, nothing caught within any mechanism, no dirt on the wheels and the contacts are fine. I've had the bodyshell off and swapped out the DCC chip but the behaviour is the same. One thing I have noticed is that both the chips I've tried get very hot during running, to the point where I could feel the heat through the roof of the body and the chip itself can barely be touched.

You have determined there is high power consumption (motor and decoder hot).

Decoder swap doesn't fix it, so it is the loco mechanism where the fault has to be looked for

The change in performance was sudden, and now it goes slowly and judders or struggles (difficult to see speed changes in this state).

 

Most likely cause: one of the drivelines between motor and worm slipping a lot, so one bogie being driven normally, the other only getting intermittent drive so braking the loco. (With half the weight on each bogie it barely moves when drive stops on one, intermittent loss of drive leads to slow speed, much juddering. The decoder's BEMF gives the motor lots of power in an attempt to reach the speed step, and motor and decoder start to heat.)

 

Put dots from a spirit marker on each tyre side and watch them. One end will rotate normally, the other end will be slow, and there's your trouble. Take it apart, find and stop the slipping wherever it is located. Cannot give precise guidance because I have not seen this problem on  a Hornby mechanism.

[smokebox]

Has it been cleaned and lubed?

[alexross42]

Thanks for all your suggestions, appreciated!
To answer some of the questions....

- I bought it 2nd hand about 18 months ago so not sure how heavily it was used before, it's probably done less than 24 hours running since I've had it but will take a closer look at the bearings/motor situation.

- It's 50046 'Ajax' - maybe it's trying too much to be as realistic as it's namesake is these days.......!

- On this model the fan was one of the static types, so isn't connected to the motor (and was subsequently removed to make space for the speaker).
- I'll try the approach as described by 34theletterbetweenB&D to determine if one of the drivelines is at fault.

Cheers,
Ross.

[pheaton]

The parts the 34th is talking about... 

 

 

This is the bogie after removal from the loco, but note the retaining clip at the top of the tower is still in place

 

 

This is the bogie with the retaining clip removed the part your interested in is the worm, it will lift out but beware the rear bearing may come off as it will be loose on the shaft. 

 

 

This is the worm, the part 34th is describing is the plastic part on the right, you should not be able to rotate it independently, if it does rotate inspect carefully for cracks if there are none pull it off the shaft clean the shaft with some ipa to get the grease off it, I roughen it slightly with a file, but that's my method, and then superglue it (making sure the bearings are still behind it ) light oil after its dry and reassemble, if its cracked you might want to try epoxy if you have not got a spare.

 

Sorry about the post if it reads odd I'm in my phone. 

[34theletterbetweenB&D]

18 hours ago, pheaton said:

...This is the worm, the part 34th is describing is the plastic part on the right, you should not be able to rotate it independently, if it does rotate inspect carefully for cracks if there are none pull it off the shaft clean the shaft with some ipa to get the grease off it, I roughen it slightly with a file, but that's my method, and then superglue it (making sure the bearings are still behind it  ) light oil after its dry and reassemble, if its cracked you might want to try epoxy if you have not got a spare. 

And there is the other end where the shaft drive is coupled to the flywheel or motor shaft. Never having seen this type of trouble in my limited experience of the Hornby drive line, I don't know if that end is vulnerable to failure.

 

(On Bachmann twin bogie drive models, in my experience when the juddering slow/no-go problem is seen, it's always been the plastic coupler insert slipping in the flywheel. But as ever, with a different construction the part vulnerable to failure may be different.)

[alexross42]

Thanks again for all your help & suggestions. I ended up removing both drivelines/worms and cleaning everything ensuring that all parts were moving freely and free of any gunk or excess lube, it did then run a little better but still had a restricted speed and was still subject to judder and occasional speed 'lunges'.

Then I removed everything again so that the motor would turn but wasn't connected to anything - at speed step 1 it was juddering/struggling to turn but beyond this it performed smoothly and seemed to be increasing speed in line with the controller. (This also gave the opportunity to run some interesting double headed consists as it freewheels along the track very well!)

 

Next I'll reassemble everything and reassess. If it still isn't right then a replacement motor will be the next step.

 

If nothing else this has led me to learn and appreciate a lot more about the mechanics of these locos which I'm sure prove to be useful knowledge to recall and use throughout my modelling adventures....!

 

Cheers,
Ross.

 

[Guest JiLo]

Try the motor on straight DC - wires straight to the motor rather than through the circuit board and see if that helps.  If the motor still judders then that is the def the problem, if not the fault is in the chip/circuit board

[alexross42]

2 hours ago, JiLo said:

Try the motor on straight DC - wires straight to the motor rather than through the circuit board and see if that helps.  If the motor still judders then that is the def the problem, if not the fault is in the chip/circuit board

 

Good idea, thanks.

I feel it's definitely time to invest in a soldering iron and start learning these skills too!

[34theletterbetweenB&D]

Being able to perform electrical soldering confidently and reliably makes a world of difference in my opinion. You'll be ripping out and replacing flaky wiring, and soldering up clip on or push fit electrical connections in next to no time.