Thanks to all who gave me the great suggestions earlier. I have a Atlas 50’ hopper that continually derails after I install kadee couplers. I did an experiment where I unscrewed the trucks and had the car rest on the trucks w/o screws. The car ran fine. This is also truve of the coupler, which easily swings and is aligned per NMRA standards using the various testing tools.When I put in the 2/56 1/8" screws, the car derails on straight and curved track. Should I just run the car w/o the trucks screwed into the body or just declare the car a loss?
You may be tightening the truck screws too tight – leave them loose enough that there is some free play in the trucks. It is usually recommended that one truck be more loose than the other.
I leave the Trucks fairly loose BUT still have the screws in the body.
While some believe one truck needs to be slightly tight - I have found that to be a problem at times!
Also make sure that the hole in the truck bolster is not too small and when the screw is inserted makes the truck not want to pivot easily on the bolster!
If it is just ream it out a bit.
Atlas cars never really have any tracking problems that I have found!
BOB H - Clarion, PA
I tend to have one truck tighter than the other but in this case from what you say I’d just have the screws in just enough to hold the trucks on if you remove the car from the track.
Good Luck.
The system that I been using for over 55 years is a simple system and easy to follow.
I start by tighten the truck’s screw completely down(the truck will not move) and then back the screws off 1-1/2 turns,I then proceed to check wheel gauge, trip pin and coupler height…This procedure gives me a car that will be derailment free.
Make sure the head of the screw fits into the counter bore of the truck bolster. Some 2-56 screws have too large of a head- mainly the self tapping kind
Many freight car kits I’ve built have a bit too long bolster sleeve that receives the screw. When fully tight, the truck can still be too loose as the screw is tightened to the sleeve. I file the sleeves shorter a bit so the screw tightening range can be from too loose to too tight. I follow the advice above and tighten one truck a bit loose and the other one tighter but still able to rock somewhat. If they are both very loose the car may rock unrealistically over crossings, etc. If too tight, derailments are more likely.
A contributing issue could be car weight if way off standard, but that’s unlikely the primary issue.
One other comment on weight- first, assuming the car weight is appropriate (either NMRA or greater), is it distributed equally from one end to the other, along a centerline axis? If you have put additional weight in, that should be balanced and centered.
Cedarwoodron
One truck should be tightened sufficiently so that it rotates freely, but will not swivel - this one keeps the car steady on the bolster. The other truck should be adjusted so it rotates AND swivels freely. This truck compensates for uneven-ness in the track work.
Mark.
Thats what MR magazine has called the 3 point method. Personally I always tighten the screws down so the trucks won’t swivel, and then back them out just enough to get them to swivel freely but not rock. Usually one of the ends up rocking a little anyway so I end up with the 3 pt suspension in the end.
I’m curious about the coupler installation. Did the car work well before you swapped couplers? Sometimes I’ve had situations where the wheels or trucks are blocked by replacement draft gear boxes and can’t turn the way they could with original equipment. In particular, the problem showed up with the little semi-circular “ears” on the sides of some Kadee boxes.
I will agree, though, that overtight screws need to be backed off a quarter-turn or so.
I had this same problem. Turned out it was whe wheels. Even now if I look at the old wheels, they look fine but on the car with the added new Intermountain wheels, no derailments!!! Yes this was an Atlas car, their best!