Well it seems I have come up with a solution to my problem with the Sergent coupler height on the Intermountain 19,600 gallon corn syrup tank cars. Seeing as the coupler was sitting to high and the knuckle was hitting the top edge of the resin height gauge I had to find a way to lower the coupler. I shoot for the knuckle to be about centered in the grove on the coupler height gauge. Problem was the way the draft gear box was designed on the tank car. On most freight cars when you remove the screw on draft gear box you get a flat or mostly flat lid you remove and the draft gear box is part of the frame of the car.
On the Intermountain 19,600 gallon tank car once you remove the two screws you are not removing a flat lid but the draft gear box with the open top facing up if the car was upright when you removed it. The lid is actually a flat area on the car frame. This meant that I had to find a way to shim the draft gear box down about .015” to .020”. Yes it is a lot and not every car was off the same amount. One car only needed a .010” shim at each end. I have only done 5 cars and three were off .020”, one was off .015” and the last one .010”. I am almost sure the difference in ride height is caused but the frame bolster plates the are separate parts glued to some raised parts on the bottom of the tank. Seems like on some cars the parts were pressed down properly when glued and on other they were not. On one car the frame bolster plates fell of when I removed the trucks.That was the one that only needed a .010” lid/shim as I made sure the frame bolsters fit properly before gluing them.
I ended up using some styrene to make a new lid that fits on top of the flat area on the cars frame that the draft gearbox screws to. To solve the tight swing of the coupler when the draft gear box was screwed back in place I glued a .010” bronze washer to the post in the draft gear box. This kept me from filing the coupler shank. This then meant the back end of the new lid needed a .010” styrene shim to keep things level. The good new to all this is the coupler height is fine as the knuckle is just about center in the resin height gauge. Some cars have the knuckle more toward the bottom of the slot and some more towards the top. The other good news is now that the draft gear box has a lid that is not part of the car frame it is easier to put it back on the car. Before the new lid/shim you had a draft gear box you had to turn upside down to put back on the car if you were using a jig like I have that hold the car upside down so I can work on it which meant the coupler may fall out and the little spring would fly away and vanish forever.
Yes I know my description of the new lid/shim is not very good. I have 12 more cars to do so I will take some pictures and post them to a folder in the group photo section. It is actually a very simple piece to make and is removable if one ever want to convert the tank car back to Kadee or similar couplers. There is also no filing of the truck bolster as well.
One observation I would like to mention is while the Intermountain 19,600 gallon tank car are very nice and the coupler height problem is a minor set back I was not impressed with the factory assembly job on some of the cars I have. A number of them have excess glue and parts glued on crooked as well as parts that with the slightest touch fall off. Not bashing Intermountain but I was a little disappointed as that was just the five cars I have added Sergent coupler to. Hopefully my remaining 12 cars are better as like I said they are very nice tank cars.