Grade too steep

Add weight to the trolley.

MELGAR

Adding weight is the first thing to try.  Is there an easement on the beginning of the grade where the level track meets the upward track?  A gradual beginning of a grade can make a difference. 

I remember something from years ago in one of the magazines suggesting scoring shallow notches across the rails to  give additional traction in HO. Might work with the traction tires, of course shorting their life. But if it gets the trolley up the hill--

I remember that" filing a course tread tip" on HO track,  it worked for me decades ago  while in Jr High.  I could drag almost any string of cars up that steep grade, but it could possibly add strain to the drive train over the long run.

What is the rise of your grade in how many feet of run?  Don't think of it as messing up but rather trail blazing!

A good vertical easement may help.

Is the grade on a curve?  Steep grade + tight curve = twisted railhead which can cause loss of traction.

Hal

Ideal grades less than 2%.  2" rise for 100" of run.  I managed 3.8% grades, with a lot of work, on a small layout.  

You need corrugated wheels.   This is what happens when you run on Tom's track!

For really steep grades you need a funicular train! I didn't know what that meant either, but they have a really cool one that goes up the side of lookout mountain in Chatanooga. Very neat ride, but it can get crowded on nice days. 

Rod

I have seen trolley lines with really steep grades (5 percent or greater) work just fine.  How steep is steep?  Can you provide a measure like elevation change and length of run?

PONIAJ has the answer.  See above.

Ed