Steam & Excursion > Beyer Garrett and fuel / water consumption & TE

There is a beautiful photo on the International board of a 4-8-2+2-8-4 from Kenya. Question is this: With the water stored over one set of drivers, and the fuel over the other set, as each was consumed, how did the engineer cope with the variable weight on drivers? I would think that the tractive effort would change over time.

John Gezelius
Tustin, CA

John, Wikipedia has what I believe to be the most succinct comment on your question as can be found anywhere. I will quote it here.

"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] (Notably in South Africa - my comment) 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."

Cheers,
Jack



Edited 1 time(s). Last edit at 05/23/13 16:31 by africansteam.

John, the Wikipedia article is largely correct, but there are a couple of additional points to be noted: first, the rear tender on a Garratt is just that -- a coal and water tender, same as on more conventional locomotives, and not just a box for coal; so its weight is reduced too as water is consumed. Second, many later Garratt designs (notably the South African Railways' GMA, GMA/M and GO classes) had very small front tanks, partly to reduce the axle load, but also to limit the weight variation as the water was consumed. When the SAR used auxiliary water tank cars, the front tank on the Garratt was kept full, and only water from the auxiliary tank car was used.

Roger Lewis (airbrakegeezer)

Thanks gang

Roger, that explanation helps clear the steam from the picture

John Gezelius
Tustin, CA

Thanks for bringing this up and the answers, I always wondered myself how this worked but didn't have enough know how about steam to phrase the question.

Art Reid
Brunswick, MD
Art's Photo Squirrel Flickr pages



Edited 1 time(s). Last edit at 05/25/13 22:24 by cota1992.