Advice on building 2-axle rolling stock

[Benjamin Maggi]

As my Sweet William engine is slowly being constructed my mind sometimes wanders to other subjects, such as building freight cars (wagons) to pull behind it. My engine is 3.75" scale to run on 7.25" gauge track, so the prototypes are roughly 24" gauge. I say roughly because many of the real Welsh slate railways were gauged slightly over (Talyllyn Railway = 27"; FFestiniog & Welsh Highland Railways = 23.5").

One gentleman in the UK built quite a rake of freight cars and displayed them at an Exhibition there. I may eventually build something similar and wondered if there was anything in particular I needed to pay attention to regarding tracking and suspension. In the USA we typically have 4-axle cars instead of the short 2-axle ones that were prevalent in the UK. Bobber cabooses at the end of a train are one thing, but a whole consist of them is something else entirely.

Anyone have any advice? Thanks.

http://www.worldrailfans.info/GardenRai ... te2003.htm

[bill4227]

3 point suspension? One set of wheels fixed, the other set pivot on the center of the axle. Some 0-4-0 British steam engines do this.

[Fender]

I built a four-wheel sugar cane car, and had trouble with it derailing, until I softened the springs above each journal box. With the springs mostly, if not completely, compressed, then the journal boxes can move downward to accommodate dips in the track better.

[Glenn Brooks]

3 point suspension? One set of wheels fixed, the other set pivot on the center of the axle. Some 0-4-0 British steam engines do this.

So how does this work exactly? Does the pivoting set of wheels have a split axle at the center, or do they just pivot on one bearing hanging down from the center of the bolster? I've never been very clear on how this could work - and would like to build a couple of 4 wheel 'Jimmies' to carry ballast.

[chooch]

If you look close at the photos in the Link, you might get a good idea from the tank car, the gondola with the big log and one other I forget.
The look like Pedestals on a bobber caboose. Their pretty easy to make. Flat stock bolted to the frame, springs and journals. You could make a wheel set with square tube, axle all the way through and a bracket in the center of the tube attached to the frame. But, something still has to keep the tube axle and car upright properly--so some kind of spring rigging OR one axle sprung, one solid, 3 point suspension.
I have done the One axle sprung, one solid using Pillow block on a speeder--Plain looking wheels.
My Bobber caboose--same method But with Non working outside pedestals.
You might think what has more work, looks the best, easiest to make for you.
chooch
I copied the pedestal from a Live Steam mag article on building a Bobber caboose. Can`t think which one right now--maybe about the 1973 issues.
chooch

[Erskine Tramway]

My cars are half-scale "Heywood" wagons with rubber springs. The 18" wheelbase tracks just fine, loaded or mty. There may be a little twist in the mortise and tennoned wooden frame. They might not "stay on" rough track, but with reasonable cross-level, they work fine.

Mike

[DianneB]

I have been running my variation on a Densmore tank car for two years with not a single derailment and I agree that soft springs are the key. Mine carries a propane cylinder and was sprung for that weight but even with another adult riding on the aft tank, it still tracked well. My version isn't detailed but was very quick and easily built from shop scrap (except for the wheel/axle sets).

[Harlock]

Jim Sabin and I each built substantial 3" scale bobber cabooses, and used real leaf springs on each pedestal, calculated correctly so as not to be too stiff or too loose. These have turned out to have excellent tracking with no problems. Jim's caboose is far heavier due to the method he used for constructing the body (MDF) as well as the fact that his has a completed interior. Thus his has more leaves on the springs than mine.

Start here and scroll down: http://www.chaski.org/homemachinist/vie ... 38#p328838

You can also use coil springs, just be sure they are the right stiffness. Build your car first, then figure out the weight on each spring. If it's a ride car, approximate the average load.

There is no need for cross equalization or anything like that on an unpowered four wheeled item. You CAN get away with one fixed axle and one sprung, but I don't recommend it for lighter rolling stock. If everything is independently sprung it will take all kinds of track.

I will say that leaf springs are far more damped than coil springs, it's like having modern shock absorbers on your car. Gives a very smooth feel. We also did careful calculation for the Chloe's independent leaf springs on the drivers and it never came off the track.

I should mention that in the end I went with roller bearings with a barrel shaped outer race so they could rotate easily inside the journal box when one side of the track dips. The suspension in this way is very flexible.

[Benjamin Maggi]

Thank you all for your helpful replies!