I think in theory Ed and his friend might be right, however in a
practical sense a 'weak link' is often engineered into a product. After
my father-in-law passed many years ago, I was helping to clean up the
family farm. One of the chores was to take the remaining grain to the
elevator. A screw device is used to load the grain into the truck bed.
It was powered from the tractor's PTO with what amounts to the universal
shaft similar to what we have to deal with. Well, being inexperienced,
I jammed it somehow. I was saved from ruining some main components by a
little thing called a 'sheer pin'. It's made to be the weak link and
break rather than damaging expensive stuff!
With that in mind there has to be some 'give' someplace because 'stuff
happens' inside our engines. Most of the problems we've had over the
years with slipping shafts is due to the wrong kind of plastics used.
They give up way too soon. The original AM FP-7 engines used Hobbytown
shafts and I will use them as the benchmark for durability. I
understand MicroMark sells them now.
One of our former members, went on a quest for better
shafts/universals. He found what he liked in the RC boat department. I
have one installed in my USRA Mike. It has brass couplings with set
screws and a nylon type dog bone that is 4 times thicker than the
typical model railroad product--slipping problem solved. The only
problem is that there's not a weak link and I suspect that the motor
would be damaged before the gears or the shaft would fail.
I did a stall test once on a motor, we locally called a 'Dutch can
motor'. It was installed in the Overland Pacifics. I had the motor
fastened down but couldn't grab the shaft with my fingers so I used a
pliers. The motor was so powerful or weak (depending on one's point of
view) that the motor shaft broke loose from the windings inside the
motor itself and self destructed.
Bob Werre
BobWphoto.com
ed_loizeaux wrote:
> Gents...
>
> Once upon a time, many moons ago, Mr. J. Padgett
> brought two locos with him to the mighty NYC.
> Identical in every respect save one. One loco
> had SS drivers and the other had nickel plated brass.
> Running them around the layout, it was clear that
> the SS drivers did pull a bit better. Thus, all future
> SouthWind imported locos had SS drivers from that time on.
>
>
> Regarding the breakage of drive train parts, it was
> Mr. Smith's opinion that a properly designed drive
> train would be such that all parts of said drive train
> should be able to withstand the pulling power of the motor
> used. Thus, U-joints, valve gear rivets, press fits of
> plastic parts, gear teeth, driver materials, etc., etc. should
> all be perfectly able to withstand the forces involved if
> the drive train was properly designed in the first place.
>
> Following this logic, it would seem that all the pieces and
> parts making up a drive train should be able to remain intact
> and functional well past the point at which the loco drivers
> are slipping on the rails. Some modelers use steel rail for
> even more coefficient of friction. I know both HO and O scale
> guys who do this and swear by it and have experienced no
> problems. They love their long trains.
>
>
>
[Non-text portions of this message have been removed]
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