My guess is that customer preference, coupled with engineering conservatism, was the reason why equalized three-axle trucks were preferred under some GE export locomotives for a few years after the unequalized type became available.
The civil engineers would have been accustomed to having equalizing gear on their steam locomotives, and some may have had (unsatisfactory) experiences of earlier British export steam locomotives that, per established domestic practice, were not fitted with equalizing gear. They might though have accepted unequalized two-axle trucks, as these had a degree of inherent equalization. Add to that that many export locomotives, designed with lowish axle loadings, had a relatively high power-to-adhesive weight ratio, and so were probably thought to be more in need of good equalizing gear to help minimize wheel-slip caused by axle unloading. To some extent the locomotive makers reinforced that notion; for example a feature of the GSC 1-C truck used under the South African U18C1 and U20C1 fleets was the extra-careful attention to equalization.
EMD used unequalized three-axle bogies on its export designs from the start, and their early reputation may not have helped the general spread of the type. One example;: New South Wales regarded its 42-class Clyde-GMs as having inferior riding and tracking characteristics at higher speeds as compared with its 44-class Goodwin-Alcos, which had Commonwealth double swing-bolster equalized trucks.
Still, it seems that eventually GE was able to convince its export customers that a well-designed unequalized three-axle truck, probably coupled with improved wheel-slip control, was an effective solution and also one that was simpler than an equalized truck and so lower in both first and maintenance costs.
What kind of trucks were fitted to the early Mozambique U20Cs I don’t know. But these were ordered at the same time as the Rhodesian fleet, and in both cases the operators were persuaded by the South African experience in which GE was seen have an excellent product, and one that was very well supported. So it seems likely that those Mozambique long-nose U20Cs had equalized trucks, like their Rhodesian counterparts.
Curiously, South Africa’s first EMD locomotives, GL26Cs in 1966-67, did not have the regular EMD trucks, but rather an outside-equalized design that did look somewhat like a longer wheelbase version of the GE long-nose U20C truck. What kind of bolster springing was fitted I don’t know. It would seem that to get its foot in the door in South Africa, EMD not only had to slim and trim its G16 design to the point where it was close to being a dead ringer for the U20C, but also fit similar trucks.
Cheers,
The civil engineers would have been accustomed to having equalizing gear on their steam locomotives, and some may have had (unsatisfactory) experiences of earlier British export steam locomotives that, per established domestic practice, were not fitted with equalizing gear. They might though have accepted unequalized two-axle trucks, as these had a degree of inherent equalization. Add to that that many export locomotives, designed with lowish axle loadings, had a relatively high power-to-adhesive weight ratio, and so were probably thought to be more in need of good equalizing gear to help minimize wheel-slip caused by axle unloading. To some extent the locomotive makers reinforced that notion; for example a feature of the GSC 1-C truck used under the South African U18C1 and U20C1 fleets was the extra-careful attention to equalization.
EMD used unequalized three-axle bogies on its export designs from the start, and their early reputation may not have helped the general spread of the type. One example;: New South Wales regarded its 42-class Clyde-GMs as having inferior riding and tracking characteristics at higher speeds as compared with its 44-class Goodwin-Alcos, which had Commonwealth double swing-bolster equalized trucks.
Still, it seems that eventually GE was able to convince its export customers that a well-designed unequalized three-axle truck, probably coupled with improved wheel-slip control, was an effective solution and also one that was simpler than an equalized truck and so lower in both first and maintenance costs.
What kind of trucks were fitted to the early Mozambique U20Cs I don’t know. But these were ordered at the same time as the Rhodesian fleet, and in both cases the operators were persuaded by the South African experience in which GE was seen have an excellent product, and one that was very well supported. So it seems likely that those Mozambique long-nose U20Cs had equalized trucks, like their Rhodesian counterparts.
Curiously, South Africa’s first EMD locomotives, GL26Cs in 1966-67, did not have the regular EMD trucks, but rather an outside-equalized design that did look somewhat like a longer wheelbase version of the GE long-nose U20C truck. What kind of bolster springing was fitted I don’t know. It would seem that to get its foot in the door in South Africa, EMD not only had to slim and trim its G16 design to the point where it was close to being a dead ringer for the U20C, but also fit similar trucks.
Cheers,
