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Author Topic: Weight that an a Gauge loco can/should pull  (Read 809 times)

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Offline NeMo

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Re: Weight that an a Gauge loco can/should pull
« Reply #30 on: July 09, 2017, 11:56:02 am »
I might do this with my locos and publish the results.

As has been said though, Chris, unless someone's track layout, cleanliness and every other variance is the same as you then it can only be your experience and not generally accepted as fact.


Plus, this has been done at some length in the N Gauge Journal in the past year or so. So while I'd certainly find anything @Chris Morris has to say interesting, I'm definitely with @newportnobby so far as the repeatability and validity of the results go.

As a scientist, I can tell you that that it's crucial to be able to control all possible variables other than the single one being tested. This would have to include the cleanliness of the track, the age and maintenance of the loco, the frictional drag of the wagons, the consistency of the output from the controller, and so on.

Cheers, NeMo

Online njee20

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Re: Weight that an a Gauge loco can/should pull
« Reply #31 on: July 09, 2017, 01:14:18 pm »
And of course all of those variables are wholly controllable, it's simply their relevance to 'real world' where it's an issue.

Offline NeMo

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Re: Weight that an a Gauge loco can/should pull
« Reply #32 on: July 09, 2017, 01:31:22 pm »
Some steam outline locos, usually the ones with traction tyres are good and others are pretty hopeless.

Generally agree. But with steam, you've got to deal with the limited volume on the inside of the loco, which means there's usually less weight directly on top of the powered axles.

What we don't seem to agree upon is the order of priorities that N gauge (steam) loco designers need to work around. Specifically, something like this...

  • Haulage
  • Low-speed running
  • Price
  • Detailing
  • Resilience to wear and tear
  • Ease of servicing
  • On-board electronics for things like DCC and sound

For someone with limited space (say, less than 6' for an oval, or 4' for an end-to-end), absolute haulage ability isn't important. Even 'Flying Scotsman' on such a layout will probably only be hailing 3-4 coaches! Indeed, someone with a shunting plank will be far more interested in low-speed running than haulage. A modeller with a DC controller couldn't care less about DCC or sound, and such electronics will be, at best, an unwanted expense, and at worst, an extra something that could go wrong, preventing the loco working completely. And so on!

Each of us will prioritise these differently, which is why we go round-and-around whenever these discussions arise. The fact is that for reasonable cost, a manufacturer can't prioritise ALL these features, hence some sort of compromise ends up being forced upon the model. Sure, you can choose a Union Mills loco with great haulage, but likely mediocre low-speed running and poor detailing. Conversely, the Dapol 9F has outstanding detailing and a good price, but the lightweight plastic used results in indifferent haulage and the tiny details offer little resistance to casual wear-and-tear.

Cheers, NeMo

Online njee20

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Re: Weight that an a Gauge loco can/should pull
« Reply #33 on: July 09, 2017, 01:53:42 pm »
My only 'kettle' is a Tornado, which luckily hauls the 9 mk1s and a dummy 67 I ask of it with no issues at all! Hadn't really considered how much less some would haul.

Online Rowlie

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Re: Weight that an a Gauge loco can/should pull
« Reply #34 on: July 09, 2017, 08:11:31 pm »
Thanks Chris for posting your review, looks like there maybe a need for a banking engine for the castle.

Offline Dr Al

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Re: Weight that an a Gauge loco can/should pull
« Reply #35 on: July 09, 2017, 09:56:01 pm »
As has been said though, Chris, unless someone's track layout, cleanliness and every other variance is the same as you then it can only be your experience and not generally accepted as fact.

I would agree here.

But there's also another factor - namely variability of manufacture. I've just bought 2 Castles. One ran perfectly straight from box; the other had wobble and grind (and less haulage) that took some adjustment to rectify and get the same performance as the first. Therefore, even nominally identical models can perform notably differently - had I obtained the first only I'd probably have a very different opinion of the model had I obtained the latter only. As it is, I've seen both ends of the spectrum.

Therefore one single verdict obtained from testing of one particular model is not definitive at all, even if all testing methodology is maintained - as well as the variation nobby says, there's this aswell.

As for traction tyres - they do help a lot; but the number of models I've seen with dire running, wobbles or the likes because of wonky tyres (expanded due to oil, stretched due to handling or just poorly manufactured) is vast. Therefore I can see why Farish try to get away from them if they can.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Online njee20

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Re: Weight that an a Gauge loco can/should pull
« Reply #36 on: July 09, 2017, 10:19:46 pm »
No need to be so defensive, it's been discussed extensively that two obstensibly identical models can have wildly varying performance characteristics.

By all means share your results, but as has been said, they're likely not that applicable to anyone outside of you, on your layout. 

Offline Webbo

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Re: Weight that an a Gauge loco can/should pull
« Reply #37 on: July 10, 2017, 12:28:03 am »
I won't bother to do any more comparative testing because we have experts who tell us the results are meaningless. I'm sorry to have wasted everyone's time on this.

Chris, I liked your comparisons and I certainly think they are worthwhile. To be sure there is going to be some variation between 'identical' locos but I believe that traction is mainly about weight over driving wheels and the fitment of traction tyres; that is, about design. As for transferability of results to other layouts, though actual traction may very well depend on track cleanliness etc. to some degree, the traction relativities of one loco model versus another would remain. A good puller on one layout is certain to be a good puller on another.

I have a 1.8% incline on my layout and traction has only been an issue for me in one case. My Farish class 5 could not haul 6 coaches up the grade without slipping so I sold it on to someone who had a level layout or fewer coaches (I hope). It could not pull what I wanted it to. Conversely, I have an Atlas old-style American 4-4-0 that makes a Dapol Terrier look large. It's not a strong puller, but it can manage 3 lightweight excursion coaches up the hill so for me it's haulage capability is just fine.

Webbo   


Offline Dr Al

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Re: Weight that an a Gauge loco can/should pull
« Reply #38 on: July 10, 2017, 09:26:20 am »
Quote from: Chris Morris on Yesterday at 10:07:12 pm
I won't bother to do any more comparative testing because we have experts who tell us the results are meaningless. I'm sorry to have wasted everyone's time on this.

No need to be so defensive, it's been discussed extensively that two obstensibly identical models can have wildly varying performance characteristics.

By all means share your results, but as has been said, they're likely not that applicable to anyone outside of you, on your layout. 

Interesting the original post now deleted....this is another problem we tend to have with reporting - opinion can be driven by emotion if the model doesn't perform - we've all been there and done it when we obtain a model that we find disappointing .

Been there and done it myself with the first Dapol 9F I got as I was looking forward to a Minitrix replacement and it underperformed!! I posted on this emotionally rather than factually back in the day - as time's progressed though I realise that one should report one's findings objectively and factually in a quantifiable manner - saying "it runs well" or "it's terrible runner" or such, like the old Railway Modeller reviews used to do with *every* model isn't useful to anyone as it's totally subjective - one person's "bad" is another's "ok", is another's "that's good". As such, posting measurements is the more useful thing - even then, these need to be take collectively over as many folks experiences as possible to really obtain the true picture.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Offline Dr Al

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Re: Weight that an a Gauge loco can/should pull
« Reply #39 on: July 10, 2017, 09:37:29 am »
I won't bother to do any more comparative testing because we have experts who tell us the results are meaningless. I'm sorry to have wasted everyone's time on this.

the traction relativities of one loco model versus another would remain. A good puller on one layout is certain to be a good puller on another.

I see the point, but it's liable to be skewed heavily by the particular examples being tested - if I compare the poorer of the two Castles I got with a very good (say for arguments sake) Dapol Hall, then the disparity may be large. However, if I compared my better Castle with a poorer Dapol Hall then it could be completely different - and by a large margin. The variability I've seen between identical models has been very large in some cases, without a large sample size. This is always going to be the problem with this - adding variability in the testing scenario (i.e. the layout, trains being pulled etc) and the info, whilst very useful as a broad guide, can't be taken as totally definitive.

Ironically, this is prototypical with steam - drivers often said there were particular locos of some classes that were poor steamers no matter what; others were absolutely fine. So it happens on all levels, not just ours!

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Offline Webbo

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Re: Weight that an a Gauge loco can/should pull
« Reply #40 on: July 10, 2017, 10:17:12 am »
An interesting point Al. What you are saying, I think, is that these locomotives of the same model are not really being manufactured in an identical manner or, to put it another way, to the same standard. I have not enough experience with multiple purchases of the same locomotive to comment on this (by a long shot). But, your comments do suggest to me that quality control in the manufacturing process is suspect, a hoary old chestnut that has been raised many, many times and has caused a lot of angst on this forum from both apologists and from unhappy customers.

Webbo   

Online Yet_Another

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Re: Weight that an a Gauge loco can/should pull
« Reply #41 on: July 10, 2017, 10:21:41 am »
Hmm. I can see an idea of 'testing days' forming. This would be an open invitation to attend a layout on a particular day, but just bring locos of the nominated brand/model.

They would all get run on the same layout, the same load could be used, and it would provide a much broader spectrum of results to enable a better statistical analysis of the performance of the loco (or locos) being tested.

If a standard layout configuration was used, say a large oval of Kato track, and the same controller, then the same test could actually be repeated in several locations.

As I say, just an idea  :)
Tony

'Things are not done by those who count the cost of every thought or deed.'

Offline Dr Al

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Re: Weight that an a Gauge loco can/should pull
« Reply #42 on: July 10, 2017, 10:23:30 am »
An interesting point Al. What you are saying, I think, is that these locomotives of the same model are not really being manufactured in an identical manner or, to put it another way, to the same standard.

Precisely.

The two Castles I have are a prime example of that - one with no issues, the other with wobble, grind (related) and a tender that leaned back. Down to variability in manufacture - I think the component that often causes this for Farish are the plastic axle insulators being moulded with some variability in precision of the holes leaving imperfectly concentric wheels. Tender was due to the pickup bearings - I just bent them straight so it sits level.

Another factor is aging, wear or the likes of the tooling - not relevant for a new model like the Castle - but a good example is possibly the Dapol 9F - I've seen a number of the most recent production models with non concentric wheels/axles and bowed main chassis (making the model see-saw about its central wheel), giving wobbly running. I've not seen the same on earlier production; though of course there may be some out there.

Cheers,
Alan
« Last Edit: July 10, 2017, 10:24:48 am by Dr Al »
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

Offline Webbo

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Re: Weight that an a Gauge loco can/should pull
« Reply #43 on: July 10, 2017, 10:36:45 am »
A very interesting and worrying notion, Al. I suppose I'd always assumed that axles and bearings etc. of model locomotives were all stamped out on a mill that would produce pretty much identical results.

I might add that I have 6 Kato SD-40s and these all run and pull pretty much identically as I would expect. Perhaps the Japanese can manage such manufacture and the Chinese have a bit more trouble with it?

Webbo

Offline Dr Al

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Re: Weight that an a Gauge loco can/should pull
« Reply #44 on: July 10, 2017, 10:55:34 am »
A very interesting and worrying notion, Al. I suppose I'd always assumed that axles and bearings etc. of model locomotives were all stamped out on a mill that would produce pretty much identical results.

I suspect the metal parts are fairly consistent - perhaps the ones that are least likely to be are castings (and I think this is how steam loco wheels are now done by both the main manufacturers, but may be wrong). I've seen a few Dapol wheels (57xx) with non-concentric bosses, and these are a single component, so solely down to the manufacture of that component.

Plastic moulded parts seem to have more variability - plus any flash can cause issues (I've seen this on some couplings that were stiff due to flash on the coupler head or NEM socket). Having pulled a few new tool Farish wheels off their axles and rotated the central insulators, they definitely can be non-perfect too. I don't actually understand this - we don't see it on cosmetic mouldings (bodies etc) - but perhaps that's simply because failures in this respect will be immediately obvious and weeded out during manufacture process. A tiny insulator with a fractionally misaligned hole won't be seen until its effect is seen on the running of the finished model.

Of course at the sizes we work build up of tolerances can also be an issue - I suspect this can be a factor in variability between nominally identical models also.

But it's not all so bad as all this might make it sound - the reality is that the quality seems to continue to improve substantially - this is evidenced by a reported significant reduction in returns from Bachmann that was reported in another thread.

Cheers,
Alan
Quote from: Roy L S
If Dr Al is online he may be able to provide a more comprehensive answer.

 

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