slipstream Posted January 10, 2015 Share Posted January 10, 2015 I use the standard NCE Powercab. I have 2 X Bachmann class 37's both fitted with ESU V4.0 with sound, running in a consist. With CV 5 set to 255 for both. One completes a lap in 24 secs at full speed and the other just 20. Is this normal behaviour? Link to post Share on other sites More sharing options...
Wherry Lines Posted January 10, 2015 Share Posted January 10, 2015 I would imagine so. Like anything 'mass produced', there would be slight differences between identical. I have several Dapol class 66's, and each one runs slightly differently. Link to post Share on other sites More sharing options...
RMweb Gold BoD Posted January 10, 2015 RMweb Gold Share Posted January 10, 2015 As Wherry Lines says. There are so many variables. A tighter set of gears. A bit more lubrication. One of the wheel bearings causing a bit more friction. No two motors are identical. It is not uncommon to have to speed match locos that you are going to run in a consist. One way is to lay out a simple oval of track and have one following the other without coupling them. Change the CVs until they maintain a fixed distance between them over several laps. Changing the top speed may do it. You may have to change the mid voltage too. If you are really unlucky and there are variations over the speed range you may have to get into changing the speed curve. Hope it doesn't come to that. Link to post Share on other sites More sharing options...
slipstream Posted January 10, 2015 Author Share Posted January 10, 2015 Yes done all of that Bod. Have them running fine together. Just thought that 4 secs over 20 was a vast difference. Link to post Share on other sites More sharing options...
Sunnysa Posted January 11, 2015 Share Posted January 11, 2015 In 38 yrs in MR hobby I have yet to see any two locos perform exactly the same. Even two locos same brand and type. More often than not most locos will be faster in one direction than the other. Some decoders use CVs 66=forward & 95=reverse to adjust this To overcome speed difference in locos either do a full 28 step speed curve being CVs 67 thru 94 which is easiest done with JMRI Decoderpro or the easier way is CV2= start speed, CV5=top speed, CV6=mid speed.. Adjust CV2 so loco is just moving on speed step 1 then adjust CV5 to desired top speed, then CV6 between half to 2/3 of value in CV5. Cheer Ian Link to post Share on other sites More sharing options...
slipstream Posted January 11, 2015 Author Share Posted January 11, 2015 I can only assume that the slower of the two's motor is not receiving the same amount of current as the other. Very peculiar considering they're identical decoders. Of course there are variables to take into consideration such as gearing, lube etc, but 4 seconds slower over a 20 second lap is a huge amount. I actually had to buy a higher performance AC adaptor for my NCE Powercab as all my loco's were very sluggish. Using the 'modelspeed' app the slower class 37 has a top line speed of 60mph. The faster just over 70. I'm not one for playing scalextric with my layout but surely each loco should be able to, at least, make their prototypical top speed? Link to post Share on other sites More sharing options...
RMweb Gold pheaton Posted January 12, 2015 RMweb Gold Share Posted January 12, 2015 Not necessarily, it could be the magnets in one motor are weaker than the other. very difficult to match to trains speed together Link to post Share on other sites More sharing options...
Sunnysa Posted January 13, 2015 Share Posted January 13, 2015 Exact same current can power 2 identical locos and, like I said, very rarely will both locos perform exactly the same. There is many variables in mass production. I said before, most locos will go faster in one direction than the other. That is why many decoders have compensation for it by adjusting CVs 66 & 95. Cheers Ian Cheers Ian Link to post Share on other sites More sharing options...
Crosland Posted January 13, 2015 Share Posted January 13, 2015 I can only assume that the slower of the two's motor is not receiving the same amount of current as the other. It's more to do with the motors and mechanisms being made down to a price which results in natural variation between seemingly identical units. Andrew Link to post Share on other sites More sharing options...
slipstream Posted January 14, 2015 Author Share Posted January 14, 2015 I don't know what I did but the offending loco has now increased its top speed. I'm lost, really but happy. Thanks for your suggestions. Link to post Share on other sites More sharing options...
The Bigbee Line Posted January 14, 2015 Share Posted January 14, 2015 Has the offending loco now "run in" and maybe a tight bearing has eased? Link to post Share on other sites More sharing options...
RMweb Premium newbryford Posted January 14, 2015 RMweb Premium Share Posted January 14, 2015 I don't know what I did but the offending loco has now increased its top speed. I'm lost, really but happy. Thanks for your suggestions. I had a couple of locos that were perfectly matches last year. They normally run as a pair, but I've done a couple of exhibitions where I ran only on of them - so presumably it's loosened up a bit more. Now they need tweaking to re-match them. WIth DCC - it's a simple task. Cheers, Mick Link to post Share on other sites More sharing options...
RMweb Premium newbryford Posted January 14, 2015 RMweb Premium Share Posted January 14, 2015 very difficult to match to trains speed together Not using DCC. Easy to adjust basic settings such as start voltage, mid and top speed to get them near to each other. Quite a few decoders also support speed profiling where a specific "curve" can be programmed in. Cheers, Mick Link to post Share on other sites More sharing options...
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