Four wheel pilot trucks...Help.

[Robert]

Ok follow me a little, and I will try to explain what I'm after here.

I want to learn how to optimize a four wheel pilot trucks function. For example...Is it ever worthwhile adding axle weight (like solder wrapping the axles) to a pilot truck to enhance it's trackability?

Is the coil spring always used or can it be eliminated perhaps? If a spring IS used I know the potential of causing reduced pulling capability can come into play because it takes some loading off the driver(s)...in that situation should the balance point be biased towards the engines traction capability or is an over sprung pilot to enhance it's trackability preferred ? If a balance point is important exactly what exactly should I be trying for?

Speaking of the spring is a mushy spring more desirable that a firm one?

A pilot truck can often exhibit the tendency to climb the rail and cause a derailment...it is the fault of track work or what can be done to the truck to correct this?

If you really know the subject I'd like your expertise.

Thanks

Robert

[Jay Criswell]

Robert,

I, like many others here, have spent a lot of time dealing with this issue. The fact is there are too many variables to give you a one size fits all answer.

I will say, the 4 wheel lead trucks made by KTM for Max Gray, US Hobbies, and West Side Models worked as well as any. Their design was about as simple as it gets.

Wish I could be of more help to you.

Jay

[E7]

Guessing that things vary depending on the specific locomotive in question. You already have a fair amount of possible fixes. Might be best to experiment with them to see which works best. Probably not the answer you hoped to hear, but maybe the best route to go.

Rich

[bob turner]

You might want to check out the All Nation two axle truck and springing system. It is simple and effective.

I personally mill out a very heavy slug of brass, then bore axle holes dead center between it and a 1/8" thick one-piece keeper. No need for springs there.

I occasionally have to spring a single axle truck - like the rear engine on a Cab Forward. Difficult to get them balanced properly.

[rrjjf]

Four wheel pilot trucks can be a pain in the butt. First, be sure that the wheel sets are not contacting the cylinder heads or pilot on curves. This is a problem for sure. I do not think springing the truck is necessary if it has some weight to it as Bob says above. Lobaugh pilot trucks are not sprung and stay on the rails. The original sprung Varney 4 wheel pilot truck is a very clever design and also works very well. I have made pilot trucks at times for some locos and I do not spring them and they have worked OK. Some pilot trucks swivel on a tongue attached to the trucks rear, others pivot from a slightly curved slot centered between the pilot wheels with a coil spring on the pilot truck screw (Max Gray, US Hobbies). You will have to experiment but the simpler the truck assembly can be made that works well on a particular model the better off you will be.

Joe

[Robert]

Well I appreciate the feedback. Once you fellows with the major league locomotive experience stated that the 4 wheel pilot was indeed a PIA, I dug back in and finally got back to good running.

I did several things...I pulled a wheel off each axle and loaded about 24 steel washers 3/8" dia x 1/32" thick on each to assure the wheels were biased DOWN. I became suspicious of the relatively small diameter spring intermittently hanging up on the mounting screw. To resolve that I used a section of brass tube over the screw and then rummaged through my coil springs to find a larger diameter spring to fit over the new fat configuration. It is what I'd call a pretty soft spring, but enough to keep those 4 wheel down along with the weight of the washers. I'm running a test now and will continue for the afternoon...no derailments allowed. Fingers crossed. Thank you!

Robert