David Siddall Posted March 16, 2012 Share Posted March 16, 2012 As a total 7mm scale (O Gauge) beginner I am now the proud owner of my first loco, a Heljan Hymek, a superb model of which I propose to ask no more than it shuffle up and down a small end-to-end layout, at modest speeds, hauling a few wagons on a strictly one-engine-in-steam basis ( ...or its operational equivalent in the infernal combustion era anyway). However... My previous (OO and N) layouts were more than satisfactorarily served by an NCE 'PowerCab'... a great little piece of kit (IMO) which I'd quite like to continue using because the budget won't stretch to anything with more grunt just at the minute. Heljan's seven mil Hymeks apparently have a prodigious appetite for amps and the PowerCab is a bit lacking in that department vis a vis output (...or so several folks who'd be very happy to sell me alternative units are suggesting). Advice please... Since I don't need a loco with the sort of tractive effort that'll pull a house down I'm thinking of reducing the Hymek to a single motor... is that likely to reduce its draw to something the PowerCab is more capable of handling? Think a little light shunting and max of 25 mph scale speed over a layout 18' in length? With only a single motor will a good quality function-only standard decoder intended mainly for OO locos do the job - I have a couple of Lenz Silvers to hand? If I need to rethink my decoder strategy, what would people suggest? Traction and lighting control only at this stage and preferably not too expensive. Sound is definitely on my wish list but isn't a short-term prospect. If anyone can help I'd really appreciate your insights. David PS: It has been pointed out that a function-only decoder would be about as much use as a chocloate fireguard in providing traction and lighting control (duh). I've amended question 2 so that I don't appear to be such a complete dimwit ;-) Link to post Share on other sites More sharing options...
Willy Posted March 17, 2012 Share Posted March 17, 2012 David. I can only offer my limited experience of using an NCE 'PowerCab' to drive a Heljan Hymek. It worked very well for a few months and then the Power Cab died. It was the handheld unit where the problem manifested itself and apparently it was the high current draw from the Hymek that blew the board. It only lasted as long as it did because I only used it to shunt a few wagons on a small layout. I too had thought of removing one of the motors and I don’t see why it wouldn’t work on a small layout. Willy Link to post Share on other sites More sharing options...
David Siddall Posted March 17, 2012 Author Share Posted March 17, 2012 Sorry to hear about your unhappy experience Willy and thanks for sharing it. I'm hoping that the single motor solution is the way forward? D Link to post Share on other sites More sharing options...
Ron Ron Ron Posted March 18, 2012 Share Posted March 18, 2012 2. With only a single motor will a good quality function-only decoder intended mainly for OO locos do the job - I have a couple of Lenz Silvers to hand? 3.If I need to rethink my decoder strategy, what would people suggest? Function-only at this stage and preferably not too expensive. David, a "function only" decoder won't be able to power your loco as it has no motor drive. I suspect you mean a regular non-sound loco decoder? As for power handling, I don't think you can avoid the need to upgrade the output of your PowerCab. This system is designed as a starter, or lead-in to purchasing the full NCE system and while it can be used as a stand-alone unit, the low power output specification has been determined so that upgrading is never far away. Fortunately NCE offer a halfway house route to upgrading. The SmartBooster beckons. . Link to post Share on other sites More sharing options...
David Siddall Posted March 18, 2012 Author Share Posted March 18, 2012 Thank you Ron, for both the advice and the correction. My misdescription of the sort of decoder I'm after would, I suggest, confirm my almost legendary lack of detailed knowledge on the subject of DCC. I shall investigate the 'SmartBooster' forthwith... David Link to post Share on other sites More sharing options...
mikeg Posted March 18, 2012 Share Posted March 18, 2012 David, I think that the way the Heljan loco is wired makes the motor draw the same for only one motor. They are quite big motors and draw about 1.5-2amps when starting but run at under 1amp once going. I have not yet chipped my hymec but have done the 47 with a sound chip and that runs on my prodigy but it is 3.5 amp so able to cope with the power. When I tested the hymec on DC the ammeter on the power supply only showed 1amp max and I could not stall it, it just slipped but still only drew 1.5 amps so I think that the locos vary as one of our club members hymec drew 2.5 amps under similar conditions. I also have class 20's and they also appear to draw only 1amp on DC and run on a H&M 1 amp hand held with no cutting out on my 20ft long test track. One way that I have seen used was to install 2 chips one to each motor and address as one unit, the chips were TCS T1 or might have been M1's but the unit run on a Hornby select! it was a class 47 but without sound. regards mike g Link to post Share on other sites More sharing options...
David Siddall Posted March 19, 2012 Author Share Posted March 19, 2012 Now that's an ingenious solution Mike, thank you! Your advice suggests to me that to completely dispensing with Heljan's circuitry and hard wiring the motor (or motors) and lights direct to the decoder(s) might be a way forward? David Link to post Share on other sites More sharing options...
Ron Ron Ron Posted March 19, 2012 Share Posted March 19, 2012 One way that I have seen used was to install 2 chips one to each motor and address as one unit, the chips were TCS T1 or might have been M1's ...... Now that's an ingenious solution ...... Forgive me guy's, I don't have any experience of 7mm or larger scales, but I can't see how cobbling together a solution based on decoders not suited to the task, can be any sort of sensible route. Some (but not all) decoders designed for use with H0 & 00 models are perfectly able to power some 0 gauge models, provide their power demands are relatively modest and loads they are expected to pull are not excessive. For more demanding applications, the obvious solution is to use decoders specifically designed for 0 gauge (and larger) models. There are many of these available from all the leading decoder manufacturers. Regards Ron . Link to post Share on other sites More sharing options...
mikeg Posted March 19, 2012 Share Posted March 19, 2012 David, Ron I conceed that the best solution is to use the higher rated chips but as most cost in the £35-40 mark and are quite large there is not a lot of room in the Heljan models due to the cast chasis. The use of two say £10-12 chips that are more than powerful enough for the motors seems a good way of getting the best at a reasonable cost. I have a sound chip in my class 47 that is for O and one in an 08 that is for OO as the motor draw is 0.3 amps so I say use what works and is the least cost to get the best results, as money is generally in short supply for most people to spend on hobbies. regards mike g Link to post Share on other sites More sharing options...
Tim V Posted March 19, 2012 Share Posted March 19, 2012 Speaking of the 4mm Heljan Hymek, I had to re-motor it, the motor as supplied wouldn't pull a reasonable load, and used a lot of amps (for a 4mm model). The loco had two speeds, fast and stop. Replaced it with a Canon, and the loco was transformed. Have you looked at replacing the motor with a different one? Link to post Share on other sites More sharing options...
David Siddall Posted March 20, 2012 Author Share Posted March 20, 2012 Lots of food for thought here gentlemen, thank you, it's much appreciated. Whilst I appreciate that I 'am' ultimately going to have to bite the bullet and both upgrade my PowerCab with a booster and buy dedicted O Gauge decoders, options which won't knock such as big hole in my scarce modelling resources are very appealing in the shorter term. The Hymek is the only loco I'm planning to include in my roster that's dual-motored as-built and, as such, it's the one that I gather is most likely to exceed the standard PowerCab's capabilities (and possibly fry it!) ...hence I'm looking at whether it's possible to apply a loco-specific solution. Other motive power on my wish list will be built from kits: an 03 (DJH), a 121 DMU (Westdale) and maybe a 'Baby Warship' or 'Teddy Bear' (there are new etched kits for both the latter due out later this year). As I understand it all four would seem to be able to perform the tasks required of them more than adequately on what appear to be the sort of motors you'd fit to a large 'OO' kit-built loco ...which I believe might be considerably less power-hungry than the Hymek? The whole question arose in my mind after talking to a layout exhibitor at the recent Bristol O Gauge Show. He told me that his Bachmann Brass r-t-r steam locos were equipped with OO gauge Bachmann decoders controlled by what he described as a 'basic' Lenz handset (the one with the rotary speed control). He was displaying a short end-to-end terminus layout similar to what I'm proposing and have just starting to build. The superb performance he was achieving sowed a seed of hope that I might be able to achieve something similar with the PowerCab... David Link to post Share on other sites More sharing options...
Willy Posted March 20, 2012 Share Posted March 20, 2012 Most of the Bachmann 7mm RTR should be fine with the Lenz Silver decoders that you have as indeed should any small 7mm loco with a mashima type motor and a free running chassis. Be wary of fitting a decoder to each motor of the Hymek and giving them the same address as apparently they will not perform well unless the motors are perfectly matched and that is unlikely with mass produced motors as fitted. I am not an expert on this but I have read it on a number of occasions and I do believe that there was a thread on the subject on this forum so search it out if you can. Willy Link to post Share on other sites More sharing options...
David Siddall Posted March 21, 2012 Author Share Posted March 21, 2012 Cheers for that Willy. I coming to the conclusion that reducing the Hymek to a single motor is at least 'a' solution which I can impliment relatively easily in the short term (and will be reversible if required). Mike g's assessment of the 7-mil Hymek with dual motors is that it: "draw(s) about 1.5-2 amps when starting but run(s) at under 1amp once going" (though he does acknowledeg they vary). So on a single motor I'd hope all will be OK. A possible concern is that suppliers quote the PowerCab as outputting at variously 1.5 or 2amps max! NCE themselves quote it as a 2amp system. Hmmmm...???? David Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted March 22, 2012 RMweb Gold Share Posted March 22, 2012 I think you need to either re-motor the loco or upgrade the DCC system. In theory the system should shut down if the load is too high however it can probably take a short period ssmall overload and therefore will run at peak current but cannot sustain it without overheating. Motors can vary considerably two very similar mashima locos one drew 0.4A the other 0.9A there seemed to be no difference in the mechanisms it just seemed to be the motor. Best practice for any loco is to measure the stall current before fitting a decoder then fit one which can deliver the stall current otherwise the decoder can become an expensive fuse! I would therefore try measuring the stall current for one motor on the Hymek and see what the demand would be. Don Link to post Share on other sites More sharing options...
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