Newsgroups: rec.models.railroad

I'd like to respond to some of those who offered opinions and answers to my
questions...

    From:  swist@doodly.mcc.dec.com (Jim Swist)

    18" for whatever reason is the magic number for most HO
    equipment.  Probably 95% of the stuff on the market will
    run at this radius.   The longer stuff looks pretty ugly -
    you get not only overhang on engines, but underhang
    on long passenger cars, i.e., you need significant clearance
    on not only the outside, but also the inside of the curve.

That's fine.  As I said, the helix is hidden, so appearance isn't a
problem, and I can construct it with plenty of clearance.

    From andradee@woods.ulowell.edu

    You left out some info that would be helpful, like what type of
    engines are you going to most likely run.

Not really.  Maybe I'm doing things backwards, but I'm trying to
establish my operating standards based on available real estate and
terrain, rather than decide on engines and trying to design my
landscape to suit.  Come to think of it, what I'm doing is probably
more prototypical.  :)

    You would have to shop around and ask or read literature but out
    by the manufacture of the engine you are looking at as to the mim
    radius.  They do vary.

Do manufacturers really put out literature documenting minimum radii
for their engines?  This is news to me.  How do you obtain these?

    From: ggg9y@poe.acc.Virginia.EDU (Garth G. Groff)

    Would it be possbile to make your bottom level a bit lower to avoid
    the head clonking problem and those 18" radius curves?  I think you 
    will be sorry if you drop to 18" radius.

This is an option I have considered.  Another possibility that
occurred to me after I posted the original article:  stop the helix
short of the upper level, bring the track back into the train room,
but continue the grade.  The level to level spacing will be minimal at
the portal, but will increase as the track ascends around the room.
This is the solution I currently favor.

    From: macman+@pitt.edu (Dennis H Lippert)

    18" is too tight for almost anything...  even small diesels
    (Geeps) look somewhat out of place here.

Remember that I don't care about appearance on the helix.

    Another thing to consider is that an 18" HELIX will have a much
    steeper grade than a larger one, so you'll be pulling a tight
    curve and you'll also have a lot of side-forces from the extra
    weight of the train.

So far I agree with you.

    The grade would be what?...  56" per loop, at least 3" rise per
    loop, so it's a 1 in 18.84 rise, or 5.3%...  MINIMUM.

Huh?  18" radius = 36" diameter = 113" circumference.  A 3" rise per
cycle is 3/113 or 2.65%.  The rest of your post makes more sense if I
substitute "diameter" for "radius" throughout.  Is this what you
meant?

    From: markbr@radian.UUCP (markbr)

    I have really tight turns - a small area in a small garage, and at
    least one of my curves, at one point, is definitely just under
    18".  My Tyco/Mantua Mikado has to take it slow; on the 18"
    curves, no problem.  Also, this same engine runs ok up a slope of
    about 5.5% (about 2" in 38") pulling about 8 cars.  The Bachman
    Spectrum K-4 also has little trouble pulling a 3-car passenger
    train (yeah, well, 72-footers) up the hill.  The dual-flywheel
    Athearn F7 takes 10-12 cars up the same hill with no slipping, and
    no problems on any of my curves.

This is encouraging, though I hope I can avoid grades like yours.
Newsgroups: rec.models.railroad