Weighting for 2 rail pilot trucks

How about a spring between the pilot and the chassis or a piece of lead on the pilot?

Yves

I machine them out of two very heavy pieces of brass.

Austin Bill,

Assuming you are having derailment problems with a 2 wheel pilot truck, there can be several things going on with it.  Have you checked the wheel gauge with an NMRA gauge?  It the tongue that attaches the truck to the frame too short to allow the truck to pivot properly?  Is there some lateral motion in the axle where it goes through the truck frame?  There should be.

Rather than a weight, I would suggest getting some 0.008" phosphor bronze sheet and cutting out a flat spring that can be attached to the frame over the truck and then adjusted to apply pressure down on the truck frame.  This is very adjustable and easy to do.  Phosphor bronze sheet can be cut with a pair of sharp scissors, drills easily and is easy to shape.  A piece about 1/4" to 3/8" wide should do the trick.

Joe Foehrkolb

Hi Joe,

Where does one obtain some 0.008 phosphor bronze sheet?  Are you going to attend the Strasburg show tomorrow?  If so, and if you have any extra material for sale, could you bring it?

Thanks in advance,

Steve

when looking for suitable material to fabricate electrical pickups, I came across bronze metal weatherstipping that is very similar to the phosper-bronze material. it is easily worked with and will hold a spring to it. it usually is package in a +-1" wide roll with a corrugated edge that needs to be cut off. one package will last a lifetime or two.

Phosphor bronze sheet is available from McMaster Carr.  They have a website you can order from.  Several years ago I purchased a roll of this material.  The roll was 6" wide and 50" long and I think I paid less than $20.00 for it.  I will bring a small piece of it to Strasburg tomorrow but if you work on model locomotives with any regularity, I suggest buying a roll.  It makes great pickup wipers.

Joe Foehrkolb

Hi Joe,

Thanks.  Looking  forward to seeing you tomorrow.

Steve

I rarely spring- load a lead or trail truck, but when I do, I use the spring to center the truck as well as force it downward.  I find that Northerns need guidance into curves, especially my superelevated ones.  The Varney method is good, but even better is a way to pivot the truck from just ahead of the front driver axle, adding a coil spring aft of the pivot point that tends to force the truck to go straight.

I don’t like springs because they take weight off the driving wheels. I don’t like weights, as there is no damping, and the truck can bounce up when it hits a discontinuity in the track.  I use layers of N Scale Foam roadbed. Poke a hole in it so it is held by the pivot screw.

Just put enough foam to keep the truck in contact with the rails, but not enough to provide a downward force. 

Because the foam has a high spring constant, the truck encounters a lot of resistance if it tries to bounce up. Because the foam is not putting any downward pressure, all the locos weight is on he drivers

Bill,

You never told us what the problem is/was.  What is the pilot truck doing that is inappropriate?

Ed

The engine is a Sunset 4-8-4 Northern UP 844.  My track is Atlas O (code 148 therefore) which tests in gauge with my NMRA guage.  My curves are minimum radius 60 inches some eased and some not. None super elevated. 

The pilot truck lead wheel set rides up over the railhead in the middle of one and only one 60 inch curve which is not on a grade.  Engine is completely on the curve when this happens.  One direction (west to east) only.  When moving forward in the opposite direction it does not derail.  There are no derailments either direction on any other curves.

The pilot truck on this engine as delivered has no spring loading and so is just at the mercy of gravity, centripetal force and friction to stay on the track. I've seen this situation before on Sunset engines -- even on 3 rail engines.

Evidently there is some sort of track/engine interaction at that place on the layout that is different than on any other curves and is so slight that I have not been able to detect it.  Just makes sense to me to "cut and try" by using one of the methods above to add stability to the pilot truck before re-engineering the track at that point.

Remove the pilot truck from the loco and roll it across the trouble section.

Reverse the wheelsets in the pilot truck.

Replace the wheelsets in the pilot truck.

Drop the pilot truck on the floor and try again.

Okay - Opinion here.  Your lead truck functions well on a big Northern, 60" radius, except at one particular point on your railroad, and only in one direction, and you think there is something wrong with the lead truck?

Do not mess with that lead truck.  Any scale 80" drivered Northern that can get around a 60" radius curve is already quite well set up.  Your track has an anomaly, and at that radius I suspect it is almost invisible.  Look for a rail joint that decreases the radius, or a kink.  My Northerns have trouble with 70" radius, and that is because the lead truck wheels touch the cylinders and the trail truck wheels hit the tailbeam.

Opinion!

 I agree with Bob that in most cases it is better to correct a isolated track anomaly than altering a locomotive to accommodate it. If you've checked that the track and wheels are in gauge, and there is no rail joint kinks or obvious vertical curves, check to see if the radius is not slightly tighter than the surrounding curve.  It is possible at that one point you have exceeded the limit of lateral travel of the leading truck.  (Radio throttles are worth their weight in gold when you need to test track/locomotives  at distant points).

  With regard to springing the leading truck - I prefer them to be lightly spring.  All my 4 wheel leading truck locomotives use a center mounting machine screw through an elliptical slot to provide lateral swing.  I use a very soft spring over the screw between the top of the truck and the frame. With respect to John's point, an overly strong spring or insufficient vertical travel will effect tractive effort.  Worst case - a friend was testing a mint $4k KTM northern that couldn't pull it's own weight up a slight grade due to insufficient travel on the lead and trailing trucks!  I play with my leading truck springs so that they are soft enough that I can easily lift the truck wheels over the rail head without feeling the weight of the locomotive or #1 driver lifting.

Ed Rappe

Thanks for the excellent inputs and keep them coming if you have them.  I'm going to proceed on both fronts if necessary -- pilot truck and track improvement/mods.  But, track first.  

Ed mentions DCC.  I use NCE DCC and I recently installed a QSI Titan Magnum decoder in the Sunset Northern.  So, I can really creep thru that curve and be there to observe it -- with added task lighting, too. 

Thanks again.