Need help adjusting Mikado spring rigging

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I completed my heavy Mikado about a year and a half ago and it runs very nicely with great traction but do have problems with the front truck coming off the rails on some of our less maintained curved track. When I built it, I really didn't pay much attention to adjusting the rigging on it and may be paying the price for it now. Several people have suggested that I don't have enough weight on the pilot. We have another, older, Mikado running the same track and he seems to have fewer problems than I do in those curves. I never have a problem on well maintained track.

I would be interested in hearing any comments from those who may have some experience in this and how they measure the weight on the trucks and drivers and what the proper proportion of weight should be allocated to the trucks, versus the drivers. The adjusters are in a hard to get to on the front rigging and I have tried to make special tools to reach them without too much luck so far. I'll bring the engine home this week so I can work on it in the shop where I have much better facilities than at the track.

[765nkp]

I would suggest you drop the pilot truck and machine more clearance in the pilot truck frame. The truck doesn't have enough swing side to side, and the swing links hit the frame and stop causing the wheel to lift off the track. I have built 2 of these and fixed a 3rd one on a customer's engine and problem solved.

Tim

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I have noticed, for some time, some rubbing on the pilot truck axle, and wondered what was causing it. Your explanation sounds like a good place to start. I thought maybe it was happening because I didn't have the rigging adjuster tight enough. The tips of the front springs are higher than the rest of the spring tips and the front coupler is about 1/4" lower than it should be.

[KarlKobel]

I had the same issue with the axle rubbing the frame and machined a relief. I thought that I had solved the issue.

Two weeks ago I had a 'bad' derailment, which caused me to rebuild the pilot (again), and I noticed rubbing between the pilot frame and the keeper that is supposed to retain the pilot in a derailment. I removed the keeper and had no further issues, I will go back this winter and re-think the keeper.

Karl
www.karlkobel.com

[KarlKobel]

As to you second question, our steaming bay tracks are made with real 12 pound per yard mining rail and we cut out a 2" long, 5/8" deep (IIRC) depression on both sides of the rail. The we made inserts to fill the depressions when not used for equalization testing. The rail section needs to be level.

In use, remove one of the inserts and roll each wheel over the depression. The wheel must drop into the depression and be in firm contact with the bottom of it. We have been thinking of a way to measure the down force during the test. One way may be to push up with a hydraulic cylinder and measure the pressure at the moment the wheel lifts.

Karl

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Karl,
I started my engine in 2006, two years after you, and followed your website about your build during those years. I picked up a couple of good machining tips, so thank you for putting all that on a site.

Regarding the measuring of wheel pressures, one of our members is an "electronics" tinkerer and has been experimenting with some kind of sensor buried in the rail that can measure the wheel weight directly. Says the sensors only came out about a year or so ago. He connects it to an Arduino circuit that gives him an analog reading directly. He actually put a model of it on display at one of our meets last year but says it's not rugged enough to put on a "real" track yet. He wants a special section of track that would only be used to weigh engines so the sensor isn't being run over all the time which sounds reasonable enough. I hope he gets it perfected soon.

[kcameron]

Bill Hayes (Michigan Central RR) made a great weigh scale on his basement work track. He cut a short (3-4") section of the rail out and put a vertical shaft below the rail (welded them to make a 'T' shape). The bottom of that shaft rests on a standard bathroom scale. He can pin the T in place when not weighing things.

To check springs he walks the loco or car across and measures each wheel. He turns the loco/car around and rolls the other way. That gives the weight at each wheel. Somebody was there one day with a loco which did fine until going around a particular curve the other way. When they checked, he found the pilot was something like 15 lbs on one side but 80 on the other. Making them even out cured the issue.

I've heard of others doing it with load cells (electronic scales) and end up with the same idea.

[photopro]

I got the engine home today and just weighed the drivers, pilot, and trailing truck and noted an immediate discrepancy on the 2nd driver, left hand side. It was 50 pounds lighter than the right hand drive, same axle. Turns out the front spring had come out of it's saddle. I'll replace that and do a new set of measurements. I still think the front end is too light. Here are the measurements I got today and keep in mind that these may vary from actual plus or minus 5 to 7 pounds. Starting at the pilot and working back to the trailing truck.
Left Side Right Side
Pilot 55 56
Dr 1 110 119
Dr 2 58 108
Dr 3 205 147
Dr 4 170 140
TT 130 98

Discounting the unseated spring, I think there is still a lot of adjusting to do.

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New readings with the spring back in its saddle.
Left Right
Pilot 58 56
Driver 1 110 103
Driver 2 110 102
Driver 3 175 155
Driver 4 150 130
Trail Trk 90 90

Any opinions out there about the weight on the pilot? Too light or just right?

The rigging is divided into two sections and is separated from each other between the 2nd and 3rd axles. Obviously the heavier weight is toward the rear of the locomotive where the firebox is. I know my setup using a jack and bathroom scale is anything but accurate, but it seems to be giving pretty consistent readings even if they aren't perfectly accurate.

[Trainman4602]

Fellows this is not rocket science.

I have produced two videos on the subject. The K4 was very slippery and after making some adjustments and reworking the lead truck with lighter springs it now pulls like a farm tractor.

Here are the two videos.

https://www.youtube.com/watch?v=I4q1b5KY7P0


https://www.youtube.com/watch?v=1-8eoCrobjY

[Soot n' Cinders]

What I've always heard is you want just enough weight on the lead and trailing truck to keep them from derailing. Axle loading is not a concern in this size like it was for the full size, so any excess weight on the non driving axles only reduces tractive effort. I've seen some locomotives that only have 15-20 pounds on the lead truck.

[Pontiacguy1]

I would leave it alone, as far as weight on the lead truck is concerned, and do the modifications that NKP765 recommended. Having between 110 and 120 pounds on the lead truck might be a little bit much, but it shouldn't hurt your tractive effort too much, and is enough that you won't have to worry about it not 'leading' the locomotive or not running through spring switches, etc...

Also, make sure that your locomotive lead truck has enough drop to it when it hits a dip in the track. I took my 2-10-0 and ran the lead truck off the end of the steaming bay track and measured how far down it fell. The longer the locomotive, the more it should drop down to make sure that you don't have a hump in the track actually carry your lead truck up in the air and off the track. At first mine would only drop down about 1/2" or so, and sometimes it would derail. My suspension was too stiff and there was not enough allowance for the lead truck to drop. I worked on the suspension some, modified the lead truck, and afterward it would drop down almost an inch or so, as measured above. No more lead truck derailment problems because of humps in the track.

I might would try to pull some weight off of the trailing truck... 180 pounds on that truck seems to be a little bit high. I would also get it down to about 100 or so, similar to the lead truck.