Wrenn 08 shunter running problem

[Dan Griffin]

Hi all.

 

i have refurbished a Wrenn 08 Shunter. I have re magnetised the magnet using a Ronald Dodd machine,  leaned it thoroughly and got it running.

 

however when i tested it, it seemed to run and then gradually slow down, so i pit it on my rolling road, and it ran fine for about 4 minutes then gradually stopped. After a minute or two it starts again. After prolonged running ( say 6-7 minutes) the metal chassis is warm (not hot) to touch. 
 

has any else had this? And can anyone point me in the direction of a cure? I’d like to DCC fit this shunter as it has alot of sentimental value. But it needs to be performing better that it is before i do.   
 

thanks

 

Dan

[BrushVeteran]

I would imagine the armature windings are probably life expired. I had this problem with two Wrenn shunters I once owner and managed to get replacement armatures at the time. However the magnets by then were also very weak so I sold them on. They do consume quite a lot of current so are probably at the top of their power limit.

[locomad2]

Basically the same as the Hornby Dublo one and well known to over heat due to poor ventilation, its even mentioned in railway mags in early 60's. I've a few and on the whole good strong locos providing you don't run them continuously. So just use them as shunting engines.

 

Even the Hornby Dublo are prone to burn out the armatures and they do get warm or even hot within minutes and tend to be high on  current at least 0.60 amp.

 

Worth checking armature nut is not too tight especially if hot and checking bottom bearings has not gummed up with certain oils or dried out I've had a few problems like this recently, 

[DCB]

These are kids toys and all the  Ring Field motored  H/D locos ( and Wrenn)  are generally absolutely fine if run fast  which is faintly ridiculous with the Diesel Shunter.   Running slow they overheat.   Especially on PWM controllers,  The H/D controllers were only 12 volt  10VA a lot less than Duettes etc.    My new Wrenn  Shunter overheated the first time I ran it 40  odd years ago,    Overheating smears the inside of the magnet with plastic from the armature which slows the armature more and the magnet gets weaker as it heats until smoke erupts etc.   I am careful not to run my Castles and 8Fs slowly for long periods.
In a  worst case scenario running slow with a heavy load the heating gets so severe  that the wires melt off the commutator and the motor won't restart.  I have soldered them back on. when I had a steadier hand and better eyesight.  
I suspect the  magnet needs replacing,  I have never had a ring field magnet fail or be remagnetised.  but the   block  magnets  I had e remagnetised  soon faded away again.
I did cure my Wrenn  shunter by fitting Romford  60:1 gears so it revs its head off and goes  everywhere  flat out at a scale 20mph or so,  and likewise geared  a Castle chassis with a Ringfield down  with a single start worm to fit a 56XX.   Again it runs fine but at  at high revs at normal speeds.      My unaltered  Hornby Dublo Shunter still  runs great after 60 years but  I never run it slowly or heavily loaded,  but I don't need to as the low geared  one can'r be stalled  as it will slip its wheels  and will run all  afternoon with no issues.   

[34101]

I had some HD locos serviced by

http://www.scalespeed.co.uk/

He rewound the armature with new wire and remag the magnet within the chassis.

Made quite a difference and still running nicely.  Maybe worth a try.

No connection other than happy customer.

[locomad2]

Following this post decided to "test" a Hornby Dublo 0-6-0 diesel shunter to possible destruction since i now can rewind armatures.

 

Quite surprised with results,  took a boxed HD circa 1964 out of box,  last used 2018 and run it, at first .60 amps @12v, then reoiled, it not easy as access is difficult. Load dropped to 0.30amps @12v free running, stayed like that after 20 minutes running both ways. Motot did get warm but thats common with HD, so did that smell.

 

Then added 15 HD diecast wagons and ran slowly for about 15 mins each direction, no problems at 0.45 amps @10v , so learnt something they are quite strong, reliable motors and good on insolfrog points too, with no stalling, motor still warm with that usual smell of run in motor in the room. Prehaps they just need running in like instructions state.

[cypherman]

Hi,

I have 2 of the Wrenn 08s. Never had any problems with them. One of them I have had since 1973.