Subject:
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Re: Draft of a new driver wheel
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Newsgroups:
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lugnet.trains
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Date:
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Wed, 29 Oct 2003 04:00:53 GMT
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Viewed:
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2010 times
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Is that something that is typically done in real trains? How about model
trains? And have people successfully implemented it in LEGO trains?
Has there been previous conversation here on .trains that I’ve misse
concerning coutnerweights? Anybody have any links?
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Counterweights were used on real steam engines to compensate the weight of
the connection to the rod, so that the wheel would be in balance again.
Without, or with incorrect counterweight, at higher speeds there would be a
significant distortion in the balance of the wheel, causing it to put huge
forces on the track and make it run very “rough” causing much wear on track,
wheels and frame.
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-some more comments-
Not all loco’s got it right- the AAR formula used for a period of time to devise
counterweight weight was out to lunch- IIRC, the Florida East Coast
suffered this badly with some 4-8-4’s.
Counterweighting and ballancing are a tremendous comprimise in full size.
Basically, you can have a loco ballanced for a specific speed, or for 0 speed,
or kind of a average, and they tend to ride rough regardless- remember, you are
talking of forces in excess of 150 000 lb on a average north american 4-8-4 from
piston thrust, and a corrisponding vertical element (particularly if the
cylinders are sloped, at even as little as 2-3% off vertical...a typical UK way
around things...). More cylinders eases things out- a 3 or 4 (or more, but not
common except on gear drive) cylindered loco has much less ballance problems
than a 2 cylindered engine.
Under the wrong conditions, hammer blow can cause the loco to literally fly off
the track. This was the case in at least one UK rail accident (Southern Baltic
tank). It is understandable that this is less than desireable :)
As pointed out, they are basically decerative in Lego (or even up to 1.5/1.6”
models), because forces are much smaller in relation to the engines...so,
ballance is far less critical (it’s a 4th or 5th power (not sure) relationship
for sure)
James Powell
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Message is in Reply To:
 | | Re: Draft of a new driver wheel
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| (...) Counterweights were used on real steam engines to compensate the weight of the connection to the rod, so that the wheel would be in balance again. Without, or with incorrect counterweight, at higher speeds there would be a significant (...) (21 years ago, 28-Oct-03, to lugnet.trains, FTX)
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