I'm new to this but enticed by the details of the engineering marvels of steam engines. As such, I've just received a new Lionel scale Berkshire and was noticing the Baker valve gear. For anyone with experience, on the engineer's side of the engine, the reverse shaft arm is perfectly vertical. On the other side, the fireman's side, the corresponding reverse shaft arm is slight forward by about 5 to 10 degrees. Is this accurate or were both of these pieces supposed to be cast in identical positions? It's not just my engine, it is all the engines cast for this particular model. If this is inaccurate, I'm open for suggestions for model refab, if anyone has experience.
im jes' a plain-dirt civil engineer but this sure sounds like a die-casting mistake, both links should be at the same angle unless some mechanical problem has torqued the shaft between the arms, which would adversely affect the operation of the locomotive. angled slightly forward would be the normal setting for anything other than a long, hard uphill slog or a backup move. my own pet peeve on models is the eccentric crank on the main driver, which is often set at 180deg. from the main drive-rod crank. it should be set 90 deg. behind the main pin, so when the side rods are at bottom quarter, the eccentric pin should be as far forward as its rotation takes it. . . unless the lokey has outside admission valves when everything is backwards, or unless the RR has chosen to have the radius rod 'up' for forward movement, as some elderly B&M pacifics did.. -big duke
Yeah, I'm a stickler about engineering accuracy...do it right the first time. So, it appears my option for accuracy is to pop the gear reach arm off, fashion a new shorter one and adjust accordingly the reverse shaft arm forward the equivalent position as the other side.
Here are some photos that should help you out.
http://www.rr-fallenflags.org/nkp/nkp-s712.jpg
http://www.rr-fallenflags.org/nkp/nkp-s725dsa.jpg
http://www.rr-fallenflags.org/nkp/nkp-s726lba.jpg
selector http://www.rr-fallenflags.org/nkp/nkp-s712.jpg http://www.rr-fallenflags.org/nkp/nkp-s725dsa.jpg http://www.rr-fallenflags.org/nkp/nkp-s726lba.jpg
Now they're hot!
Mike
Mech Engineer I'm new to this but enticed by the details of the engineering marvels of steam engines. As such, I've just received a new Lionel scale Berkshire and was noticing the Baker valve gear. For anyone with experience, on the engineer's side of the engine, the reverse shaft arm is perfectly vertical. On the other side, the fireman's side, the corresponding reverse shaft arm is slight forward by about 5 to 10 degrees. Is this accurate or were both of these pieces supposed to be cast in identical positions? It's not just my engine, it is all the engines cast for this particular model. If this is inaccurate, I'm open for suggestions for model refab, if anyone has experience.
The two sides of the locomotive should be mirror symmetric for identical positions of the main crank, but the main crank positions are 90-degrees different between the two sides.
I have gone around looking at all of the steam engine models at model train shows and noticed a variety of liberties with valve gear, perhaps because the valve gear is a mass of rods, links and levers to the model maker without perhaps having an understanding of what these things do.
One biggie is that the gear is almost almost in neutral. I suppose on a non-live steam model it is a lot to ask for that the reverse lever actually operate, but since we operate (most of the time) with locomotives in the forward direction, would having the gear in forward with some partial amount of cutoff be a reasonable depiction of the valve gear on a model?
The next biggie is that people get the return crank in the wrong phase, the thing attached to the axle driving the valve gear. The return crank is almost always 90 degrees in relation to the main crank driven by the piston, apart from some bizarro gear designs. I have seen models with all manner of angles, including 180 degrees on this.
As a "Mech Engineer", you may be interested that the Baker valve gear, where the "gear" itself is the linkage connecting the eccentric rod (attached to the return crank) to the valve rod (attached to the valve), that "gear" may be understood as a four-bar linkage from mechanism design theory.
Think of the valve rod being attached to the "crank link" of the four-bar linkage, in the form of a bell crank to "turn the corner." Think of the eccentric rod as being attached to the "coupler link" of the four-bar, and think of the reverser as changing the "ground" end of the "follower link" in the four-bar. The reverser changes the location of the grounded revolute of the follower link to effect the change in geometry of the four-bar in order to change the amount (and direction) of valve rod motion (crank link) in relation to the ecccentric rod (attached to the coupler link, whose motion in relation to the crank is determined by mechanism geometry).
After what is known as the Arnold-Kennedy Theorem of instant centers, the instantaneous rotation center of the coupler link is at the intersection of the lines through the crank and follower link. Operating the reverser moves the ground revolute of the follower as to change the location of that intersection point. From the location of the instantaneous center comes the relative mechanical advantage between coupler and crank and hence the percent cutoff of the gear.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
OK, this definitely helps. All of the cranks appear to be at the prototypical angels relative to one another. My concern is more with the symmetry of the reverse arms (the arm on the engineers side is actuated by the power reverse link) on either side: one is completely vertical, the other, which I am assuming is supposed to be also, is forward about 5-10 degrees suggesting a casting flaw for the available models. My next question now is if anyone has experience in working with models to fix such "flaws" for accuracy.
Thanks for your effort on my behalf, Mike. I am using Fire Fox because IE8 is so slow to load all the crap here. For some reason, FF won't make the links active, no matter what I do. I tried adding url in square brackets, but when I posted it just posted the url with those brackets and code...nothing active, like it used to do.
What a royal pain.....
-Crandell
Mech Engineer OK, this definitely helps. All of the cranks appear to be at the prototypical angels relative to one another. My concern is more with the symmetry of the reverse arms (the arm on the engineers side is actuated by the power reverse link) on either side: one is completely vertical, the other, which I am assuming is supposed to be also, is forward about 5-10 degrees suggesting a casting flaw for the available models. My next question now is if anyone has experience in working with models to fix such "flaws" for accuracy.
What makes this "The World's Greatest Hobby" is that you get to do anything you want with that model, provided however, that you have the OK from your spouse that bought you the thing for your birthday.
Our culture has this thing that the spouse gets to give the final OK. More universal across world cultures is the concept of the artistic imperfection. The idea is that such a flaw may be deliberate so as to not offend one of the jealous minor deities and bring punishment down on yourself, your spouse, your children, and your children's children down to the 7th generation. Or at least that is what I tell my wife when I build something with a flaw in it and don't want to redo it.
My thinking is that in the scale-model HO world, people do a lot of mods -- weathering, super detailing, kit bashing, and so on, so fixing the reverse lever is an interesting project. Lionel O-gauge, whether old stuff or the recent product, is more in the line that you acquire it to collect it, and the non-scale proportions, getting stuff wrong on the valve gear, and so on, is part of the "charm" of the semi-scale "toy" trains, and leaving it makes the locomotive a conversation piece, where you can show off your knowledge about prototypical valve gear.
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