Running Hot
Well, first question, are we all talking about the Keystone conversion or other MDC shays and Keystone converstions.
Cam, what can motor are you using in the Keystone?
In answer to both, none of my motors run hot. See items 1, 2, 3, below for investigation of the hot motors.
Three major items that will cause excessive heat build up on these engines.
1. Binding of the motor shaft to the gearbox if no interfacing driveshaft is used. Never connect the u-joint of the bullgear directly to the shaft of the motor. Especially, the Keystone. No matter how precise one is in aligning the motor to the bullgear, there is always misalignment. Build a short independant shaft between the motor shaft and bullgear. This will reduce any type of binding in this area that creates heat. Remember, binding creates extra stress on the motor and it becomes overworked, notibly in smaller motors. If using the open frame motor supplied with some of the NWSL Keystone shay conversion kit, trash it a go to an A-Line 12-20 or similar size can motor. Also, if you can not get both trucks to spin freely by turning the u-joint on the upper part of the bullgear using your fingers, you have a bind. Take a smaller motor, hold the shaft between your fingers and increase the voltage. You'll understand the binding theory.
2. Drive wheels not square to the frames. White metal does have a tendancy to bend, etc. The NWSL replacement axle/gear set needs to be honed into place. If you cannot easily spin the two axles on each truck with you fingers, then there is also binding. This is probably the greatest area of concern. Water soluable valve grind compound is needed to hone the worm. spur, and bevel gears. NWSL does great work in machining these gears, however, no two are matched. Pack a little valve grind compound in the bevel, worm and spurs gears, hook a small T shaft to the shaft u-joint on the truck and begin turning by hand. Back and forth until it begins to spinn freely. Then take the small T shaft, insert it into the chuck of a small drill (not the 24 volt puppies) and then begin slowly spinning the shaft once more, increasing the revolutions slowly. Make sure you hone the gears in both directions.
3. Just as in the MDC shay, the line shaft needs to be timed. If the timing (alignment) of the shaft gears between the front and rear trucks are not aligned properly, they cause binding and also will cause the motor to run hot.
As a note, all of these items apply to the MDC shay and climax, except for the sideshaft since the climax runs off the center shaft.
I would suggest drilling small holes in the tenders for some ventilation. I am a wood burner, so the holes are decoyed by the wood. Oil burners would need a little more care in finding areas to drill the holes so not to be noticed.
The Keystone shay does have a tendancey to want to crawl the rails (what prototype shay didn't). This is more than likely due to the timing of the side shafts or the truck frames not at a true 90 degree angle to the drive wheels. You may want to check the gauge of the wheels also. Shays are a little more sensitive running backwards than forwards.
One last note, the lenght of the center drive shafts from the bullgear to the trucks is quite critical. The shaft should have a small amount of longitudnal play between the bullgear and truck when the wheels are aligned straight.
Hope this helps answer some questions.