Hi folks! What is the difference between an equalized truck and a one that is not? (on loco or car). YM
As I understand it, equalized drivers on a steam locomotive move with the normal rise and fall of the rails to keep a uniform distribution of weight on all drivers, thereby reducing loss of traction and the likelihood of derailment. I can only assume equalized trucks serve the same function, other than to maintain traction. Anyone else have more reason(s)? Watash??
Bill, that's my understanding also. On all trucks (car and engine), it's very important to have all wheels in contact with the rails at all times, equally sharing the load. On trucks with three or more axles, the side-frames are hinged so that the truck can flex up and down and also twist, allowing all wheels to remain in contact with the rail, in spite of any track deformities. If the truck had rigid side-frames, the outside wheels could be suspended in mid-air when the truck went over a hump, or the center wheels could lift off the rails when the truck went over a hollow .... NOT a good thing when the truck is trying to support a Hundred Ton load [ 02 February 2002, 16:55: Message edited by: Hank Coolidge ]
Thanks guy! This make sens. But my only problem is I saw this (EQ truck) on 2 axles truck, under a streamliner car... Watash? Slimjim? Anyone? YM
This is my understanding of the subject. On 'rigid frame' 2 axle truck each axlebox would be sprung to the frame. So if one wheel rises up a bump (like your car mounting the curb) the spring at that wheel is compressed. Not a great problem but due to the way springs work that wheel (and the one diametrically opposite) will now be carrying more load than the other two. The effect is to try and twist the frame (which is rigid). In extreme cases the entire load could end up on only two wheels, and the lightly loaded wheels would become supended. Since on a train these are heavy load springs and therefore quite stiff, the travel available to absorb 'bumps' is quite limited, which means your track needs to be reasonably smooth to avoid trouble. On a simple 'equalised' 2 axle truck the two side frames are actually allowed to swivel up and down vertically relative to each other. They are usually attached together only by springs onto the central beam. If you look at a typical freight truck you'll see there are no springs at the axleboxes - they are fixed solidly to the sideframe. This means that when one wheel rides up a bump the load remains equally shared by all wheels, due to the theory of beams. However equalisation also appears in other guises - as mentioned in a previous post - but usually still in the form of beams. Look at some loco trucks and you'll see the axle boxes are fitted in vertical slots in the main frame, but with no springs there. A flat U shaped beam runs along the bottom of the truck and up over the top of the axle boxes. The springs are sandwiched between the lower beam and the main frame. The loco sits on the main frame and its weight goes down through the springs to the centre of the beam. From there it is shared equally by both wheels/axles. I think the passenger trucks YM refers to may be like this too.
An excellent explaination Mike .. it clearly paints a 'mind picture' for me, and I can see your points without any problem at all. Thanks.
All above is correct for real equipment. Back when good trucks were available for models, one company had shouldered screws that allowed the truck side frames to ossillate about the bolster so one wheel could move up or down (theory of beams) but had no springs. Lindsey and Central Valley, and now Kadee (I am told) have tiny real coil springs that allow the side frame to ossillate as well as provide softer ride. I had one pair of 6 wheel Lindsey trucks that had all that and the center wheels had a flat spring that rode on the axle to push it down into a sag. The side frames were slotted for this axle. I have never had any of these derail, and my track looked more like real rail does. Put your face down close to real rails and sight down the track. If your track was that bumpy to scale, none of today's cheapo plastic trucks could stay on the rails. That is why the extra long toy like flanges come on your "Scale" wheels. Have you ever noticed how a box car will jitter when one wheel drops into the long gap at the turnout frog point? Well, the trucks above will ride right over it, no problem. In real life, the flange actually rides a fillet in that part of real switch frogs. You can't do that fillet in your switches, because the flanges are too long. If all flanges were RP-25 like they used to be, then you could fillet your frogs and stop the bouncing that way. The long flanges are a holdover from making toy trains for kids in HO size.
Wayne .. haven't those spring loaded trucks been around for a long time? I have some old metal trucks, (don't know who manufactured them) that have tiny springs in them. The springs are about the same size as those on a Kadee coupler.
Yes those kind of trucks have been around since 1939. They were expensive though, they cost $4.95 a pair! Wow! Any other trucks only cost $.50 cents a pair. When the cheapo plastic trucks came out, they cost the same, and we started writing the manufacturers to complain, and they went down to 30 cents a pair. Today you might find some for under $16.00 freight, and $20.00 pass. 6 wheel on Ebay. Still expensive, but as prices go, they far exceed the cheapo plastic for running. Turn the truck upside down, and get a magnafying glass to look on the bolster for a manufacturer's marks. [ 05 February 2002, 14:17: Message edited by: watash ]
