Poor-running Heljan 47

[bunjy76]

I have had this problem with many of my Heljan locos in the past and it is really the "Achillies heel" of their mechanism design. I have found that the only way to resolve it with any degree of success is to clean up the spindle and the plastic cup then glue it back on to the spindle with Araldite. By far the worst offender for this problem is the Hymek. All four of mine have suffered drive loss from either one or both bogies requiring the above solution to be administered. Purchasing a new part from Gaugemaster is also a solution but then you run the risk of the same thing happening with the spare part eventually. Araldite has proved itself (on my models at least) to be a far more permanent solution to what is in fact a very irritating problem.

So I’ve removed the bogies and cups and there does indeed seem to be two very minor cracks on the bogie end of the cups. So you are saying to glue these to the spindles, by which i’m guessing these are the shiny metal parts that stick out from the bogie housing, right? Then just reassemble everything?

[Peterm]

It could be either end of the cardan shaft that has the dodgy cup. Only you can find which it is. Did you try the method I suggested to hopefully diagnose the problem?

I had a faulty Heljan mechanism where the worm was offset to the gear on both towers. Whether it was a one off or a manufacturing fault, I don't know, but if yours turns out to be like this, I'll tell you how to fix it.

[Metadyneman]

Any chance that these are simply the ones you run much more than whatever other Heljan models you own, because they are such good looking machines?

The theory is sound but in reality I can say that the problem seems to be very much luck of the draw. This may sound surprising for me but the my Hymeks don't get as much running as you suggest.
You are right in that it is just an irritating problem and that it is easy to rectify for those who know what they are doing, but for anyone who is not as technically minded as you or I would find it a little more than irritating to have to do "open driveshaft surgery" on a loco every time it fails in this manner.
Incidentally the Heljan locos I've had the same problem with are the class 47, class 33, Class 52 and class 35. So far it has not happened to my Kestrel, Lion, Falcon or DP2 and hopefully wont!

[bunjy76]

It could be either end of the cardan shaft that has the dodgy cup. Only you can find which it is. Did you try the method I suggested to hopefully diagnose the problem?

I had a faulty Heljan mechanism where the worm was offset to the gear on both towers. Whether it was a one off or a manufacturing fault, I don't know, but if yours turns out to be like this, I'll tell you how to fix it.

Hi Peter, the small cracks on the cups only appear on the bogie ends of the shaft. Do the cups on these ends just need gluing in to fix the problem?

[Peterm]

I'd only be glueing the cup to the shaft if it's slipping, but I'd play safe if it/they have cracks and fit new ones from Guagemaster. Did you try the test I suggested to see if any of them are slipping?

[Metadyneman]

I'd only be glueing the cup to the shaft if it's slipping, but I'd play safe if it/they have cracks and fit new ones from Guagemaster. Did you try the test I suggested to see if any of them are slipping?

Whilst buying a new part is a good solution, it doesn't stop the same thing happening with the replacement part which I have had happen to me in the past. The only effective solution I have found to be very sturdy and fail safe is the Araldite method I described above. It worked for me (and still is). I have only ever had one work loose and I put that down to an unbalanced mix of hardener/adhesive resins when making up the epoxy mix.
As Pete has suggested though, it is best to make sure the loco is actually suffering with the problem first. If it isn't then no action is required at all.
Incidentally, it should be noted, some of the the cups will work even with a split in them, it's only if they work loose they will need gluing or replacing.

[Bigmet]

...
As Pete has suggested though, it is best to make sure the loco is actually suffering with the problem first. If it isn't then no action is required at all...

We can be pretty confident that slipping in the drive line between motor and worm is the problem, from that original description:

...recently it has suffered a loss of power/traction, it’ll run for a couple of feet and then come to a standstill even though the motor seems to be running at full power. If i give it a little nudge it will move of again but then do the same thing again...

Unfortunately, what we haven't had is any report of whether the suggested tests were performed, to first locate which side of drive line the fault(s) lay, and with what result: but now appear to be at ''part dismantled and I see cracks in components'.

[bunjy76]

So, the cups have been glued in and everything reassembled (i did realise afterwards that i should have glued the cups in-situ rather than when bogies dropped out the chassis, it was a real headache to get back in, forced it back in). It’s now been run on track and seems to be moving about fine in both directions. Job, done i’d say. Thanks to everyone for sharing their knowledge with this, it’s greatly appreciated and has saved another 47 from going to the scrappers yard! : ))

[Metadyneman]

So, the cups have been glued in and everything reassembled (i did realise afterwards that i should have glued the cups in-situ rather than when bogies dropped out the chassis, it was a real headache to get back in, forced it back in). It’s now been run on track and seems to be moving about fine in both directions. Job, done i’d say. Thanks to everyone for sharing their knowledge with this, it’s greatly appreciated and has saved another 47 from going to the scrappers yard! : ))

Glad to hear the glue method worked for you. I don't know what glue you used as you didn't mention it but I have found Araldite fast setting epoxy resin to be the most effective adhesive for the job. I tried Cyanoacrylate (superglue) but that worked loose after a while. Hopefully yours will be a permanent solution.
Incidentally, for future reference should it happen again, It is possible to extract the worm gear spindle without dropping the entire bogie from the housing. You simply remove the clip that covers the top of the bogie then prize apart the two bogie halves enough to extract the worm drive spindle. Assembly is a reversal of the procedure.

[bunjy76]

Yep, i found out about the top clip whilst trying to re-assemble, it was the only way to piece it back together. I used superglue, not the epoxy that you suggested as that’s what i had to hand, however if it does work loose again then i’ll go with your method. Cheers for everything.

[Bigmet]

... has saved another 47 from going to the scrappers yard!...

That's good, and now you know the symptoms of the problem, you will be able to analyse and fix failures on other models with this style of drive linkage.

And not to the scrapper : there's a steady demand for 'spares and repairs' models, what with the unreliability of manufacturer's spares supply.

[bunjy76]

Definitely, thanks for the walk-through’s. : )