Serviceable vs. can motors

There is currently a very heated debate on the Hornby.com forum about the type of motors used in Hornby loco's. The battle lines are drawn
between those who would like a return to serviceable motors like the old X.03 & X.04 but in a modern version and those who feel the can motors are a sign of improvement and typical of our 'throw away' society.
I can see both points of view but :-
People who use these forums would probably attempt to repair / service a motor but for the general 'toy' buying public they would not.
Constant changes to specifications help no one and prevent a solid future market for 3rd party manufacturers to offer replacement motors.
Let's face it no company these days will go back to 'old technology' even if the customer wants it. It would be like admitting to making a mistake ... NO CHANCE !
I assume modern can motors are cheaper to manufacture and requires less time / skill to replace by a service agent. They say the life of a can motor is about 100 hours so that's 52 weeks @ 2 hours use per week .... the guarantee period !
Yes some models from the 1930's & 40's are still going but that kind of product, I fear, is no longer acceptable in today's market.
Our hobby is a strange one in the sense we have loco's & rolling stock using old moulds but we are looking at things like DCC etc. to run them.
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Hornby documentation says their motors will last for 100 hours, but I'm sure I read somewhere that this is a very, very conservative figure. with 'normal' use they will last a heck of a lot longer.
Cheers, Simon
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Of course the question arises is that 100 hours at 12" to the foot or at 1/76 scale?
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All the best,

Chris Wilson
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On Fri, 05 Oct 2007 23:17:02 GMT, Chris Wilson

Uh? Please spell this in thick letters!
Were you thinking (100/76) or (100 x 76)?
My 30 year old Cl25 says it all.
Regards
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The 100 hours is probably the Mean Time Between Failures - some will fail earlier (i.e. under warranty), the vast majority will exceed the 100 hours, with occasional failures (sort of bad luck, mate), then failures will increase towards end-of-life - but some will go on forever. This is the "Bath-Tub Curve", used during design to make sure the most cost effective components are used. There's no point in putting a resistor in a TV that has a MTBF of 10 years and costs 50p, when one that will last 3 years (that may be the design requirement these days) and costs 0.05p will do. Generally speaking, price is exponential to reliability.

Richard
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beamendsltd wrote:

Your "bath-tub curve" works for passive components and even active electronics components, but the discussion is about a mechanical device with wearing parts. The distant end of the curve is unlikely to be much beyond double the mean, unless the commutator segments are accidentally fitted perfectly and the brushes are accidentally made of overly hard carbon and ... and .... OTOH unless the motor is faulty it's 99% certain to reach the 100 (or whatever) hours.
Greg.P.
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Think the 100 hours was well below MTBF, more covering themselves against use of dodgy controllers or full time flat out.
cheers, Simon
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I have a couple of engines that fuction on a stop- run flat out system, so not much option there! (Yes I know, sort them out, and I will, one day . . .)
Regards
Mike
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Absolutely - theres's usually a margin of 100% or more added for belt and braces.

Richard
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The railway industry is going to be disappointed to hear that ;-) The curve was used in a presentation by the Derby Technical Centre at MISRA (there's no difference between a car and a train when it comes to software) to state the (obvious) fact that software reliability was not the same... but electro-mechanical faults in software controlled equipment could giive the appearance being so.
On an more impirical note, I see it applying to car components of all types on a daily basis - even fabricated assemblies (duff welds).

Richard
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beamendsltd wrote:

Let's take an example - brushes. Most conventional mr motors have brushes. IF these are designed for 100 hours of operation, then the failure rate might well follow the "upturned bathtube curve" at the beginning through faulty materials, incorrect fitting etc etc. The actual hours running they last will vary around or beyond the 100 design hours depending on such factors as purity of materials and the usage they are subjected to, but the upper end is not going to be particularly far beyond the 100 hours. There will not be, as there would with electronics, a few examples still in operation after say 1,000 or 10,000 hours of usage.
Regards, Greg.P.
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My 'gut' feeling on this is that the older models motors were built to last in a time of 'make do & mend' whilst today's motors are built to a price.
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Dragon Heart wrote:

The original Rovex motors and particularly the gears were way better than anything else on the toy/model market at the time. Romford survived because they offered more poles and greater reduction ratios. The quality of Rovex/Tri-ang motors possibly improved fractionally over the decades and were still "good enough" when they were discontinued. If they had made a 5 pole version and used the TT version worm they would have been the best.
Greg.P.
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On Fri, 05 Oct 2007 11:55:26 -0700, Dragon Heart

The Ringfield motors mounted in modern County & castle locos are dopplegangers of those used in mainline models and slightly quieter (don't know how noisy a new mainline was 'cause I was away at sea during that era). I have replaced several Hornby and Bachmann "flat" motors but have yet to have any problems with "can" motors. As my professional assessment of the X04 and its clan was = crap. The smoothness of my Bachmann Jubilees always cheers me but the pulling power of my Castles makes up for their whinging gear wheels! Regards
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