Serviceable vs. can motors

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

"simon" wrote in news: snipped-for-privacy@bt.com:

Of course the question arises is that 100 hours at 12" to the foot or at

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

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

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

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.

Think the 100 hours was well below MTBF, more covering themselves against use of dodgy controllers or full time flat out.

cheers, Simon

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

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

Absolutely - theres's usually a margin of 100% or more added for belt and braces.

Richard

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.

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.

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.