norman Posted November 3, 2016 Share Posted November 3, 2016 I'm having trouble getting a Heljan class 25 (O gauge) running smoothly in both directions. In the forward direction it is perfectly smooth at low speed but in reverse at speed step 1 there is a power surge immediatley. At higher speed the surge is even more apparent. I have adjusted CV58 (BEMF intensity) and can get it to run much smoother but I need a different setting forward and reverse for best results. Is this possible to achieve? I need some good logical guidance to achieve this please. Link to post Share on other sites More sharing options...
norman Posted November 3, 2016 Author Share Posted November 3, 2016 1) first, determine if it's the decoder or the motor that needs attention by removing said decoder and run the loco on straight DC 2) if it's the motor, see if running it in for half an hour each way will improve (on DC!) if it doesn't, perform maintenance/cleaning as per instructions and try again 3) if decoder is at fault, try another decoder. HTH! Hi Dutch Master Thank for your suggestions but Before I installed the decoder I ran the loco on a DC tail chaser for over an hour and I did not notice anything of significance. The loco is new and is adequately lubricated. I would be surprised if there is a fault with the decoder that causes the symptoms I am seeing. Norman Link to post Share on other sites More sharing options...
RMweb Gold D9020 Nimbus Posted November 4, 2016 RMweb Gold Share Posted November 4, 2016 This may be stating the obvious but... Did you run it in in BOTH directions? Link to post Share on other sites More sharing options...
norman Posted November 4, 2016 Author Share Posted November 4, 2016 This may be stating the obvious but... Did you run it in in BOTH directions? Hi Nimbus Yes I did run it in in both directions and the mechanism seems smooth when turning the shafts by hand so I don't think the mechanism is stiff in either direction. Norman Link to post Share on other sites More sharing options...
Crosland Posted November 5, 2016 Share Posted November 5, 2016 Have you removed all the suppression capacitors? I would expect these to affect running in both directions, but... Andrew Link to post Share on other sites More sharing options...
norman Posted November 5, 2016 Author Share Posted November 5, 2016 Have you removed all the suppression capacitors? I would expect these to affect running in both directions, but... Andrew Hi Andrew This a Heljan O gauge class 25 and I don't think any suppression capacitors are fitted as standard. The decoder is hard wired in place of the standard Heljan board regards Norman. Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted November 5, 2016 Share Posted November 5, 2016 Not knowing the model at all, is it single motored, or motor per bogie? If the former then a Zimo decoder would be my choice for the directional trim capability. If the latter then two decoders to operate the motors independently. Link to post Share on other sites More sharing options...
norman Posted November 5, 2016 Author Share Posted November 5, 2016 Not knowing the model at all, is it single motored, or motor per bogie? If the former then a Zimo decoder would be my choice for the directional trim capability. If the latter then two decoders to operate the motors independently. Hi B&D Thanks for your suggestion. There are two motors, one per bogie but your suggestion would be very expensive. I have several twin motor Heljan locos and all apart from this one are faultless with just one decoder. regards Norman Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted November 5, 2016 RMweb Premium Share Posted November 5, 2016 I am a bit confused because on this page - http://www.rmweb.co.uk/community/index.php?/topic/102992-Heljan-class-25-in-7mm/page-6 - photo of the speakers installed would seem to suggest that it is single motored. Izzy Link to post Share on other sites More sharing options...
norman Posted November 5, 2016 Author Share Posted November 5, 2016 I am a bit confused because on this page - http://www.rmweb.co.uk/community/index.php?/topic/102992-Heljan-class-25-in-7mm/page-6 - photo of the speakers installed would seem to suggest that it is single motored. Izzy Hi Izzy No need to be confused and please take my word for it, there are two motors back to back and two flywheels. regards Norman Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted November 5, 2016 RMweb Premium Share Posted November 5, 2016 Hi Izzy No need to be confused and please take my word for it, there are two motors back to back and two flywheels. regards Norman Ah, many thanks, that's a very interesting combination not easily seen in the shot. Although I haven't played with any 7mm for a while, all mine being stored away, I do just wonder if perhaps with this particular loco the pairing/wiring of the motors (I would assume parallal rather than series) is such that in the troublesome direction one motor is affecting the current draw/bemf and skewing what the decoder produces. Often such issues aren't so readily seen under dc but perhaps with the decoder fitted it might be possible to reduce/turn off the bemf to see if this has any benificial effect. regards, Izzy Link to post Share on other sites More sharing options...
RMweb Premium Izzy Posted November 6, 2016 RMweb Premium Share Posted November 6, 2016 Ah, many thanks, that's a very interesting combination not easily seen in the shot. Although I haven't played with any 7mm for a while, all mine being stored away, I do just wonder if perhaps with this particular loco the pairing/wiring of the motors (I would assume parallal rather than series) is such that in the troublesome direction one motor is affecting the current draw/bemf and skewing what the decoder produces. Often such issues aren't so readily seen under dc but perhaps with the decoder fitted it might be possible to reduce/turn off the bemf to see if this has any benificial effect. regards, Izzy I'm very sorry, but I have only just realised that only part of my reply appears to have been posted. Haven't a clue why. Anyway, this is the rest of what was supposed to have been there, hope it makes more sense :- However, from your OP it seems you have already tried this with better results but want to try and use different motor settings for each direction if I understand you correctly. As far as I am aware this isn't possible. Directional speed trimming of speed tables is, but this won't overcome the issue you seem to face, possible differential response from two basically identical motors. It has to be wondered whether even using two separate decoders would be any better if the motors react differently depending on rotational direction. Indeed, much time and effort could be spent trying to ascertain exactly what the core problem is, whether it is a motor issue, and which one, or of a more mechanical in nature - perhaps frictional loading of (one of) the drive trains somewhere at certain RPM's. I hope you manage to solve it. Izzy Link to post Share on other sites More sharing options...
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