I remember seeing a picture in Trains Magazine of (I think) a UP SW-9 Cow and Calf lined up for pusher service on some grade (I don’t remember which one). The article said without explanation that UP’s experment with switchers in pusher service proved unsuccessful.
I am sure that is an accurate representation. But, why? Given switch engine’s suitability to low-speed drag work, I would think they would be ideal for this.
Gabe
The UP TR5 sets were equipped with dynamic brakes for use as pushers on Cajon Pass. Horsepower is less of a factor in low-speed service but even a TR5 set would have less low-speed tractive effort than a pair of SD7’s or a three-unit set of GP9’s. There were probably other factors involved in the unsuitability of the TR5’s as pushers. Maybe some other members can weigh in on this issue.
In the steam era, switchers were often used as pushers on short grades that were near the yard to which they were assigned.
There’s low speed, and there’s low speed.
With a cow and calf unit the very low speed tractive effort is quite high, but over 10 - 15 mph the TE drops off significantly (due to the single prime mover powering all those traction motors). And the point of pushers is to try and keep the train’s speed up as much as possible.
Generally but not always pushers are cut off on the fly. If there is too great a differential in top speeds the pusher can’t get slack to pull the pin. The PRR had that problem with the GN motors they bought for use as pushers.
Mabee they couldn’t due without a toilet. Gabe, did they say when they tried this?
Thanks for this answer–as well as everyone else’s response. This seems to make a lot of sense.
Gabe
Keep in mind they were also used as head end helper power, (I believe UP had a rule against shoving from the rear on occupied passenger cars)and the dynamic brakes on the TRs were a small, home shop built affair…they burned out quite often in this service.
UP later rebuilt the majority of their TR5 Cow and Calfs into SW10.
Ed
Yard engines EMD SW’s and TR’s for the most part were constructed with coupler pockets that permit a wide slew from side to side so the engines can couple to cars on yard and industrial trackage that has a high degree of curvature. While the wide ranging movement of the coupler is a benefit in yard service it becomes a distinct detriment to operation in road service, especially in service where high Buff loadings are possible (rear end helper service and on the rear of head end engine consists as trains are decending grades). The wide slew of the coupler, if not limited, can create angularity that with the Buff loads will lift the locomotive off the track. (The terms that are used in the movement of trains DRAFT is the pulling force to move a train. BUFF is the compressive forces that are generated by braking the train from the head end or shoveing the train from the rear end).
The way the radiators air intakes are set up , unless the SW’s are facing forward in the lead they will overheat . It’s not a big deal to put coupler alignment blocks in , in fact alot of older engines have detachable coupler stops . EMD corrected this problem with the MP-15 series , low air intakes and top mounted fans, a true multi purpose engine.
Your question brings back a memory. Back in the later 1960’s when I was a student at Florida State, the Seaboard track went right in back of my rooming house. Just about every night there was an eastbound freight that had the local switch engine helping to push it up the grade for approximately 3 miles. Other than this one nightly freight, I never saw any others getting help so it makes sense they used the switch engine. That’s the only experience I’ve ever had of seeing a switcher regularly used in helper service in my 50+ years of train watching.
Hugh’s response implies that only the cow had a diesel engine, that is not true. Both the Cow (TR5A) and the Calf (TR5B) have their own engine. So you would have 2400 hp. available, still with 8 motors TE. would drop faster with this setup due to back EMF (they also lack transition).
Holycow, you are right.
The schematics I have clearly show that the engines had transition
Well what’s it called when they have the thing with no engine, just the taction motors and a load of weight as I was obviously thinking of something else???
That would be a slug.
I am not sure about the UP thing but here in Chattanooga I regularly see MP15DC Norfolk Southeren engines added into the consist to pull lookout mtn just saw one today with 3-big GE units An MP15 and a geep
Thanks,
Of course it is, silly me…