Super elevation?

[wcfn100]

  I don't think it has anything with making the climb easier.

I think it can in regards to reducing the sharpness of the curve (or at least lessen the effects of a sharp curve in regards to climbing a grade).


I've never really hammered out the numbers, but I think that super elevation effectively increases the radius of a curve.  The only way I can think to explain this is that the trucks on a freight cars will have to turn less for the same radius curve if it has super elevation.

I could be wrong or this could be common knowledge IKD.  It's just how I see it in my head.


Jaosn

[peteski]

Even if that is true (which it might be - I don't know), in our N scale world the effect is probably negligible.  Won't superelevating make the outside rail even longer, creating more wheel slippage as the wheel sets travel through the curve?  Again, in N scale this effect is probably not even worth taking into account.

[wcfn100]

Won't superelevating make the outside rail even longer, creating more wheel slippage as the wheel sets travel through the curve? 

No, in fact the opposite, it makes the outside rail shorter which goes along with effectively making the curve less sharp.


I don't know how much effect this all has, but people do always like to comment on how the curvature effectively makes a steeper grade so it must tie in at some level.

Jason

[Rossford Yard]

I recall John Armstrong, in a prototype railroad book, saying that the super elevation in effect reduces friction along the outside rail, and in a layout book he says (probably writing about O or HO) that the effects were enough to consider in model railroading.  It would probably be proportionally less important in N.

We have all seen helixes (or most curves, really) without super elevation.  We have seen them with super elevation.  If it caused some great positive or negative effect, I am sure we would have read about it somewhere by now.

Honestly, although it doesn't apply to Wyatt's fine track work, the biggest plus of using Unit track is its bullet proof nature.  Another plus, my old layout had a 3% grade semi circle looping around the water heater in the garage, an area that always got dusty.  Despite that, the Unitrak never had to be cleaned near as much or caused stalls as much at my other brands of flex track, probably due to the high quality metal in the rail.

You can't value either of those too much in a helix that is hard to clean and prone to operations difficulties.

[GaryHinshaw]

I agree with Rossford, in my experience modest amounts of superelevation have no effect on performance in N scale.  The equipment specs play a much bigger role in string-lining: long light cars with long-overhang, body-mount couplers (e.g. 89' flats) are the most prone to it (again, just my experience).

No, in fact the opposite, it makes the outside rail shorter which goes along with effectively making the curve less sharp.
Jason

This is correct.  Think about the extreme limit of superelevation: 90°.  In that case the inner and outer rails would have the same radius, and the trucks would have no yaw component of rotation at all (but lots of pitch).   On the prototype, the main reason for superelevation is to produce a nearly even load on the two rails.  The dominant load is gravity, which is straight down; but the centrifugal force adds a small component towards the outside of the curve making the net load point slightly outward of vertical, by an amount which depends on the speed of the train.  If no superelevation is present, this produces excessive flange wear on the outer rail, and adds drag.  Superelevation is designed to make the plane of the rails perpendicular to the load for average track speeds.

[C855B]

... the extreme limit of superelevation: 90°.  ...the plane... .

Uh... I believe we would then call it a wind-up turn.

[Kisatchie]

Hmm... I don't elevate
my track. I escalate it...

[Bendtracker1]

I agree with Rossford, in my experience modest amounts of superelevation have no effect on performance in N scale.  The equipment specs play a much bigger role in string-lining: long light cars with long-overhang, body-mount couplers (e.g. 89' flats) are the most prone to it (again, just my experience).

This is correct.  Think about the extreme limit of superelevation: 90°.  In that case the inner and outer rails would have the same radius, and the trucks would have no yaw component of rotation at all (but lots of pitch).   On the prototype, the main reason for superelevation is to produce a nearly even load on the two rails.  The dominant load is gravity, which is straight down; but the centrifugal force adds a small component towards the outside of the curve making the net load point slightly outward of vertical, by an amount which depends on the speed of the train.  If no superelevation is present, this produces excessive flange wear on the outer rail, and adds drag.  Superelevation is designed to make the plane of the rails perpendicular to the load for average track speeds.

Great explanation Gary! Thanks

[peteski]

Thanks for the excellent explanation Gary.  As far as the superelevation goes I remember as a kid having a Hot Wheels track which had 90 degree superelevation. IIRC, the rechargable electric cars were called Sizzlers.

[glakedylan]

Newton's law of physics and motion:
for every action there is an equal and opposite reaction

[Kisatchie]

Newton's law of physics and motion:
for every action there is an equal and opposite reaction

Hmm... then every time
you win, you're screwed...?

[Mike C]

Hmm... then every time
you win, you're screwed...?

  Thank you Ms. Dee for the laugh !!!!   OMG ROTF !!