Lead trucks on steamers... weighted or sprung?

Model Railroader General Discussion (Model Railroader)
1

My railroad is exclusively steam and I have done a lot of kitbashing and modifiying to improve performance.

A problem I’m having is with the some of the lead trucks. On some of my locos I can’t seem to get the lead truck to track right through switches. I’ve changed wheelsets, properly gauged and I’ve tried changing springs, but it’s hit and miss.

Would it be better to add weight to the lead truck rather than spring it, and if so, how much?

Thanks, Gary

2

I think Tony Koester has advocated weighting the lead truck. The old Mantua Pacific used a spring and tracked very well but the lead truck bolster itself was fairly large and heavy, heavier than on most brass engines. I never sensed that the Mantua/Tyco spring on the lead truck was lifting the rest of the engine chassis up, but that could be a risk with overly rigid springing.

I have brass engines that have a spring and yet still have tracking problems on the lead truck, so like Tony K I lean towards weighting, assuming you have the room for weight. I sometimes also wonder about the surfaces between the screw that holds the truck and the gap or slot that it rides in on the lead truck. Would a sleeve of plastic or teflon or some such help? I have not experimented.

Dave Nelson

3

My experiance says weight is better than a spring. And I actually remove such springs on many of my steamers - often without having to ad any weight.

Respectfully, I would ask which locos are giving you trouble and what size/brand of turnouts are giving you trouble?

Many people in this hobby have unrealistic expectations of how sharp a curve or turnout a given steam loco will run through reliably.

And many of the maufacturers don’t help but quoting minimum radius numbers that are on the edge of the locos limits.

Eample of what I do - I remove the springs from the pilot wheels on Bachmann 2-8-0’s - never had a problem, in fact I believe they track BETTER and pull more without that spring.

Also, steam locos demand very good trackwork for smooth operation. Smooth carefull track, large enough curves and turnouts, well tuned locos = no derailments.

Sheldon

4

Also put me down for weight over springing.

How much? Whatever fits. Use metal wheels, if plastic (although sometimes avoiding shorts can be an issue with that.) Wrap the axle in lead sheet. Get those titanium pine wood derby weights and expoxy 'em on. Etc.

It’s taken me multiple sessions, sometimes over seveal year’s time, before I got the right mix on some locos. Others were easy.

5

That makes sense since without the spring there is more weight on the drivers. Same reason the prototypical GN preferred the arrangements with as few leading and trailing wheels as was possible.

6

Either way works, springs or weight. In principle a spring pushing down on a pilot truck takes a little bit of weight off the drivers, thus reducing traction. But the amount is too small to worry about. Myself, I put as much sheet lead as I can squeeze in on the pilot truck, and if necessary the trailing truck. A spring interferes just a tiny bit with free side to side motion of the truck. Again, the effect is probably too small to make much of a difference. The real reason I go for weight, is that I always have sheet lead in the shop. Not so often do I have a suitable spring kicking around.

As far as amount of weight, the general rule for locomotives is “More is better”.

As far as turnouts, I find steamers are pickier about turnouts than diesels or cars. You want to check out your turnouts with the NMRA gauge, and file any rough spots smooth. Make sure the flangeways are deep enough so the flanges don’t touch bottom. Points and guard rail ends want to feel smooth to the touch. Make sure the switch machine pulls the points all the way over, every time, both directions.

7

I replaced the lead truck on all of my Athearn Mikados, using the truck from Bachmann’s Berkshire. The truck is cast metal, and tracks better due to the extra weight.

Wayne

8

Nice move, Wayne.

Shame on the manufacturers for making such lightweight, dinky pilot trucks and trailing trucks.

I actually think that the trailing trucks are worse than the pilot trucks.

Rich

9

Thanks, Rich. Those Mikes are (almost) the only locos I have in service with trailing trucks, but I’ve never had a problem with them derailing. I removed the overly-strong springs with which they were originally fitted (in order to increase their pulling capabilities), and then added a built-up loco frame under the firebox, a detail inspired by Orsonroy’s locos:

Wayne

10

Dave,

That’s a good idea. It seems to be a binding point which may force the truck to lean. I’ll give it a try

Gary

11

Sheldon

The switches are all number 6 and give me no problems with the majority of my locos. Of my 36 steamers, only 4 give me trouble. It’s not at the same turnout, nor the same area of track… seems arbitrary.

Minimum radius is 26 inches. The largest locos are two Pacifics, which never give me trouble.

Two roundhouse Atlantics (of 6), a Varney 10 wheeler and a converted Mantua 2-6-2t. The 2-6-2t is a work in progress, but I have built 2 and one is good, the other, not so much.

I do believe I’ll try weighting the lead trucks and see what happens.

12

I’ve had several issue with lead trucks in the past. In all cases I’ve removed the wheels, checked the bearing surfaces and the distance between the wheels. As a result this is some of the issues I’ve come across.

  • Wheels were not properly spaced and too wide apart (NMRA guage is a must!)
  • The hole where the pin goes through (pivot) was too tight or had burrs
  • plastic yoke was bent and had to be realigned
  • pivot pin wasn’t straight

Adding weight does help and I use 1/4 oz automotive weights that I’ve milled to allow for axle and overhead clearances and in some cases I found the Locomotive was not halanced and added extra weight to the front end