Equalizers

[Lithonia Operator]

In simple, basic layman's terms, what is an equalizer? Maybe a better question is what does it do? What is it equalizing? How does it work? Is it only a railroad thing?

My understanding is that railroad cars (or perhaps railroad car trucks) have equalizers. My impression is that it relates to springs, and my guess is that it has to do with weight transfer and/or balance.

Who can help me out on this?

[Paul of Covington]

   This is a discussion about equalization on locomotives from "The American Railway", a 1988 reprint by Castle from a compilation of articles by different authors from about 1889 as near as I can tell.

https://archive.org/details/americanrailwayi00thom/page/114/mode/2up

   Page 124 shows the suspension on a consolidation, where the three rear axles are equalized, and the front drivers are equalized with the leading truck.  Expand the picture a couple of notches to see it better.  (Ctrl +) or zoom in using the icons at the bottom right.

[Electroliner 1935]

Lithonia Operator

In simple, basic layman's terms, what is an equalizer?

From Wikipedia: An equalising beam, equalising lever or equalising bar (German: Ausgleichshebel or Ausgleichhebel) links the suspension of two or more adjacent axles of a vehicle with more than two axles, especially railway locomotives.

Or in other words, it is a system of "levers" or suspension parts arranged to try to distribute weight equally on the axles.

 

[tree68]

The equalizers also help keep the wheels on the track on rough track.  Even a small vertical change could be enough to cause a fully rigid system to lose contact.  This isn't necessarily a problem on a steamer, where the drivers are coupled, but on a three axle Diesel truck, that could leave a wheel free to spin.

The same could be said for three axle car trucks.

The springing may take care of some of that, but the equalization takes care of the rest.

[Victrola1]

It does remind one of a Hendrickson walking beam suspension used on tandem axle semi tractors. 

 

[MMLDelete]

Thanks, guys.

Paul, I'll revisit that link when I'm on the computer (not phone) and can see things better.

[Overmod]

Keep in mind that the equalizers don't provide 'suspension', they distribute the load dynamically and generally smoothly across the axles and, ideally, the wheels.

In the English designs that eschew the added cost and weight of equalizing levers, the idea is to provide wheel springs with adequate travel and use diligent maintenance to keep longitudinal journal-box play in the 'horns' or pedestals to a minimum while allowing a bit of cross-level skew (up to what rod clearances will allow).  Their idea is that allowing all the wheels to 'find their own level' approximates what the levers will do (it really doesn't, but it can be hard to convince many Englishmen of that).

Note that equalization patterns often follow 'conventional wisdom' for stability: the arrangement on a lead truck is to the pin or center, not the truck suspension, to give tripod stability; at the rear it is carried into a later Delta-type trailing truck (sometimes from close to the pivot, sometimes with levers further outboard) because the rear outer ends of the truck frame are essentially pinned and guided by the centering arrangement and guiding-stability requirements are much different with 'trailing' geometry.

Note that on engines with longer rigid wheelbase there is a benefit in dividing the equalization, for example between the second and third driver axles in an right-coupled locomotive.  (In the bad old days this was done simply with pinned hangers; more modern practice uses snubbed coil springs or elastomer/composite blocks.)  If you have access to a Modrl Railroader 'cyclopedia' you can easily see the various arrangements -- and how the distributed springs actually provide the suspension action.

I should probably mention that many designs of equalization are metastable: road shock or accident can cause the equalizers to assume tilted positions that do NOT work right.  The only real 'fix' is to jack the locomotive up far enough to realign all the levers (!) 

It can be surprising how far some of these arrangements can get misaligned.  Many pictures of PRR P5a electrics show really, really screwed up tilt on the long beam equalizers... and you wonder why sometimes they had riding 'issues' while in general they rode like "baby carriages"...

[Jones1945]

Overmod

Many pictures of PRR P5a electrics show really, really screwed up tilt on the long beam equalizers... and you wonder why sometimes they had riding 'issues' while in general they rode like "baby carriages"...

Two examples:

[Overmod]

The real 'whopper' I've seen is a picture in Volkmer's "Pennsy Electric Years", a ¾ shot where both equalizers are fully back-tilted, leaving the impression of Wile E. Coyote frantically backpedaling to avoid one of his traps or a canyon.

Once you know what to look for you see lots of P5a shots with dramatic tilt.  Leads you to speculate on whether pins are broken in the hangers.

 

[BaltACD]

[Euclid]

I have read somewhere that the condition of the equalizers over-rocking was referred to as "going ornery."

[Deggesty]

BaltACD

 

Yes! there's the Equalizer at 2:10![:)]