Why was the Garratt design never adopted in North America?

Wesley

What, if any, advantage did a Garrat have over a regular articulated, either simple or compound?

If you can't come up with a good answer for that, or if the answer is applicable to situations that weren't common here in North America, i.e. small gauge railways, then you'll know why they were never adopted here.

The principal benefit of the Garratt design is that the boiler and firebox unit are slung between the two engine units. This frees the boiler and firebox from the size constraints imposed where they are placed over the frames and running gear, as in conventional designs and other articulated designs such as Mallets. Garratts can have a boiler with a greater diameter, which increases heating area and aids the production of steam. The boiler can also be shorter than other designs with the same heating area. In some loco designs, the boiler is so long almost no heating of the water occurs at the smokebox end of the boiler. A larger firebox promotes more efficient combustion of fuel and also increases the heat available to the boiler.[citation needed]

Garratts enjoy an advantage over the Mallet system, because of the geometry of the design. When swinging around curves the boiler and cab unit move inward like a bowstring in the bow of a curve and this reduces the centrifugal force that would overturn a normal locomotive and which in turn permits faster running. The Mallet's forward articulated unit tends to throw out as the loco rounds curves. While most Garratts were designed for freight or mixed traffic, there were a number of passenger Garratt classes. A Garratt holds the world speed record for an articulated locomotive.[citation needed]

Garratts have several advantages when used on light and narrow gauge railways. They are tank locomotives and can easily be run tender-first, thus eliminating the need for expensive turntables or wyes. They do not need to be run through to terminals, increasing operational flexibility. Because the engine units are separated by the boiler unit, the weight of the locomotive is split over the two units, and they can run over bridges or line sections that might not be able to support conventional or Mallet locomotives of similar weight.[citation needed]

While at the end of the steam locomotive era most conventional steam locomotives had reached their maximum in "critical dimensions", the Garratt still had some way to go, with larger driving wheels, larger boilers and greater output still achievable.


The major disadvantage of a Garratt (shared with all tank engines) is that the adhesive weight decreases as the water is used from the front tank and coal from the rear bunker. As the weight on the wheels decreases slipping occurs. To reduce wheelslip, a wagon containing water was attached behind the Garratt, and this practice also permitted the engine to operate over longer distances.[where?][citation needed] The weight of the water in the locomotive's tank and weight of coal in the bunker (necessary for the factor of adhesion) was predicted in advance, and this problem was not normally an operational issue.[citation needed]

Good question. Here's a sub-question, did any of the North American locomotive builders license the Garratt design from Beyer-Peacock?

In 2011, I was able to fulfill a bucket list item by riding behind a Garratt on the Welsh Highland Railway. They are wonderful machines.

Ira Schreiber
Aurora, CO

What if the Pennsylvania Railroad's T-1 duplex had been a Garratt instead?

I've always wondered if the DRG&W narrow gauge had continued to develop motive power beyond the 2-8-2 if a Garratt or something similar may have been a possibility. We'll never know, but it's fun to think about!

What, if any, advantage did a Garrat have over a regular articulated, either simple or compound?

If you can't come up with a good answer for that, or if the answer is applicable to situations that weren't common here in North America, i.e. small gauge railways, then you'll know why they were never adopted here.