Subject:
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Re: BBB wheels + availability?
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Newsgroups:
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lugnet.trains
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Date:
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Sun, 21 Dec 2003 23:52:04 GMT
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Viewed:
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1259 times
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In lugnet.trains, Teunis Davey wrote:
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In lugnet.trains, Jason J. Railton wrote:
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In lugnet.trains, Teunis Davey wrote:
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Would it be good to just have a hole in the middle of the wheel to put a 2*4
modified plate with technic clips?(like the modified plates that hold the
wheels on the Lego soccer buses).Or was it a technic axel for a reason ?
Chain drive?
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I’m eager for mine to arrive, too!
I think the axle fitting is important. If you want to add coupling rods
between wheels, you MUST have opposite wheels turning together on an axle,
you MUST have at least two pairs of wheels like this, and you MUST have the
connecting rods on either side 90° (not 180°) apart (called ‘quartering’).
Anything else will drift out of line and lock up.
The only thing you can do with separate free wheels is a single rod from one
wheel to a cylinder somewhere on the body of the engine.
Jason R
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Has anyone worked out how to get the push rods to work perfectly ??
On these combo’s ,4 4 0 , 4 6 2 , etc ??
I’ve had a look ,at a real steam train, at a local park. And I found that the
push rods are in the same position, on both sides. But ,in my lego versions
they work better 90D apart. Is this what the counter balance on the wheels
fixes in real life ? Or is just the downward weight on the wheels?
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Like lar says, I’m sure that it is not the case that the quartering is the same
both sides.
However some points to consider
A: like cars, steam locos come with different amounts of cylinders, the most
basic being two (I think there were some with one, using a flywheel and indirect
linkage to the wheels), one on each side. There are also
three and four cylinder ones. (there
are some with more, but the cylinders are split between different sets of drive
wheels as in, for example, a mallet) This means that the quartering may not be
90% but it is unlikely to be positioned the same on both sides.
B: unlike a car piston the expansion force is applied on both sides of the
piston, however in a two cylinder loco there is a ‘dead’ spot at the extreme end
of each stroke while the valve is transitioning from power to exhaust. For this
reason, most engines had a cylinder on each side of the engine, arranged 90
degrees out of phase, so the engine could start from any position
Without wishing to sound patronising I have written a key for the parts in the
diagram
The red rod connected to the wheel is the Coupling Rod
The blue rod is the Connecting Rod (the ‘big end’ is the end connected to the
wheel)
The red rod in the cylinder is the Piston Rod
The end of the piston rod is supported by a Crosshead (also in red) which slides
along; and is supported by the Slide Bar or bars (in this case in black)
The
rest of the linkage is the Valve Gear, this takes many forms and is sometime
inside the wheels/frames and sometimes on the outside
(I am assuming that the names are the same in the US)
Tim
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Message has 1 Reply:
 | | Re: BBB wheels + availability?
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| (...) you didn't! (...) I think for the most part, yes. That animated diagram (and your concise explanation of it) is pretty nifty. is it at a stable location? It seems worth linking from the header, or if ti's embedded in an info page that could be (...) (21 years ago, 22-Dec-03, to lugnet.trains, FTX)
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Message is in Reply To:
| | Re: BBB wheels + availability?
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| (...) Has anyone worked out how to get the push rods to work perfectly ?? On these combo's ,4 4 0 , 4 6 2 , etc ?? I've had a look ,at a real steam train, at a local park. And I found that the push rods are in the same position, on both sides. But (...) (21 years ago, 20-Dec-03, to lugnet.trains)
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