I’m running a Bachmann Li’l Big Hauler baggage car in my short passenger train, and found that it has a very long 4-wheel rigid frame that derailed on my friends rocky track. I decided it needed suspension, and there were a few options: make one axle pivot, add springs to each axlebox, or elongate the axleboxes so the axle can drop if necessary.
The latter is an old UK trick, as many UK wagons are long and 4-wheeled. ( Suspension is not needed on a couple of short 4-wheel trucks, typical of a US wagon. ) Here’s how it works.
At the top is a regular frame with 2 axles. If the track is not level, the wheels and axles will lift and possibly derail. The middle drawing shows one axle hole elongated downwards, which has no effect on plain track. However, if the track is not flat, as you can see on the bottom drawing, one axle end can drop and keep the wheels on the rails. As you can see in this next photo, it is quite effective:
There’s only one extra consideration. On its own, the axle won’t just drop down the slot - it needs encouragement, so some form of a spring is needed to give it a gentle push. Here’s the few mods.I made to my my Li’l Bug Hauler.
I found the wheel bearings behind the molded axleboxes are separate, presumably as they are molded from a slippery plastic. They are just a push fit in the frame - squeeze the ends and they pop out.
I cut off the ears that hold it in the frame, and the bearings can move move freely up and down the slots behind the axlebox.
No need to actually modify the bearings at all - the problem I was left with was how to stop them falling out when you pick the car up, and how to add a little springiness. I did play with some small springs under the bearing carrier - you can see the tops of them at the blue arrows in the photo. Too complicated, I decided.
Some package staples were lying in a stash of bits, so I bent one to fit over the axle and screwed it into the bottom of the frame. That stopped the axle falling out.
To add the spring, I found a spring (from an Accu coupler package) that fit under the axle, and a 20mm bolt which is fastened to the frame and sticks down to keep the spring in place. A U shape from a package staple was squeezed in to the top of the spring, and the axle fitted on top.
If you look closely, you can see the bearings lifting out of the axlebox slightly due to the spring. The idea is that all 4 wheels sit flat when on level ground - the spring needs to be weak enough to just push the axle down if it isn’t level.
The spring is resting under the axle, so I expect it will wear over time and I’l lhave to craft something a bit more permanent - probably a 1/2 brass tube with a pin on it for the spring, but it will be fine for the few times I run this car.
