F3 + F7 ?

[Anonymous]

QUOTE: Originally posted by Blackfoot69

Andy,
your answer is fantastic and falls short of my requirements !
Thank you
Michel

[B)]
I'm sure Michel meant 'fulfills [his] short 'list' of requirements !
English can be such a dog....
Also the D&RGW did it, mixing all types of F's [FT/F3/F7/- F7/9] and some early GPs for xtra hp...
when gearing suited I think- they were alaredy fully MU compatible anyway
[^]
dave

[bogp40]

QUOTE: Originally posted by Leon Silverman

The faster engine would have to be on the front only if it would still run faster than the slow engine while pulling the train. If the train length exceeds the pulling capacity of a single unit, both engines will be pulling regardless of their relative positions.

Regarding where to place the faster engine. When pulling a decent length train, say 10+ cars, the faster engine should be behind. I never used to think this to be so. But try coupling the faster engine to the cars and place the slower engine uncoupled out in front. The faster(or what was faster) engine will be slowed by working as it is pulling the rolling stock. You may even notice that the out front(slower) engine will start to outdistance the rest of the train. Most times while running this way, I will watch the couplers. The lead engine is usually just going along for the ride until it is needed for a grade. Check it out, I have run my 40+ loaded coal drags for years by setting the speed placements for minimal-crunch/push on couplers between engines. Have run Stewart ABBA, P2k SD50s, mixed w/ Atlas SD35s, GP38/40s with no problems to any of the drives thus far. Many of these combinations have run during open house for 4-6 hours at a time.
There are some combinations that just won't work, due to a great difference in speed between makers and drives. For short distance running there wouldn't be a problem, but for sustained hard use the drives could be affected by being overdriven or dragged.
Bob K.

[ndbprr]

I suspect that F-3's were rebuilt by the railroads to F-7 traction motors with time making them F-7's for all practical purposes.

[espeefoamer]

In later years,at least,AT&SF commonly mixed F3s and F7s.

[ndbprr]

the PRR NEVER had FT's. When they came out the PRR was deep in the T-1, J-1 and Q-2 programs. The first road diesels onn the PRR were a set of E7's on the Detroit Arrow and were purchased in 1947. F-3's came around 1950. But the PRR NEVER had FT's. As farv as I have read they never even tested on the PRR.

[Matt1950]

Refering back to Dave's comment/question about the PRR mixing FT's and later F-Units in MU lashups -- according to a long-ago article in Trains, the PRR did some major upgrades on their FT's with modernization "kits" from EMD in the fifties to make them all compatible. I think -- and memory fades at my age -- that the Santa Fe did the same so that they could use FT's mixed in with F7s and GP's on their freights.

[Leon Silverman]

The faster engine would have to be on the front only if it would still run faster than the slow engine while pulling the train. If the train length exceeds the pulling capacity of a single unit, both engines will be pulling regardless of their relative positions.

[BentnoseWillie]

Faster one on the front. If it's in the back there will be no tension in the couplers, and therefore the slower engine will be holding back the faster engine without contributing to tractive effort. With the faster engine in front the consist will still be restricted to the speed of the slowest engine, but all the engines will be pulling the train.

Just like a tug-o-war: you put the strongest guy at the end of the rope. [;)]

[leewal]

This discussion brings a question to mind. When double heading (model) locomotives and one is faster than the other, which one should be on the point?

[TrainFreak409]

QUOTE: Originally posted by Gluefinger

I'm sure that blackfoot didn't mean to sound rude when he said "falls short of expectations"- he said in another post that he has very poor English

He says "Falls short of my requirements" not "expectations."[:p] Sorry, I just had to do that, I can be like this at times.

[Gluefinger]

I'm sure that blackfoot didn't mean to sound rude when he said "falls short of expectations"- he said in another post that he has very poor English

[jimrice4449]

The reason f-3s were the controlling unit in mixed sets was that the F-7s had higher amperage levels and if they were the controlling units coulld burn up any F-3s in the consist. There were cases where mixed models were intended. Many roads after WWII decided that they didn't need the full HP of a 4 unit FT consist and split them up into 2 unit sets w/ a new F-2 A unit (same HP as FT but looked like F-3) or F-3 A unit giving them a ABA set more in keeping w/ their requirements. I don't know how they addressed the transition problem

[davekelly]

Would the reason that some railroads didn't mix units have to do with the debate of whether an ABBA set was one or four locomotives? I seem to recall reading that the railroads wanted the set to be considered one locomotive for manning purposes while the engineer/firemen wanted it to be considered 4. Could this be why units weren't mixed?

[ndbprr]

It was important early on when mxing the two that the F3 be the control unit. I don't remember why but the F7 was obviously an improved F3 and there was a component in the F3 that was subject to damage if the F7 readings were used for running the consist. Many F3's were rebuilt with F7 compnents later so the problem was eliminated. The PRR DID NOT mix F3's with F7's until very late in their lives. They kept all calsses seprated in the early years. There were two issues of the Keystone devoted to F units recently that will tell you more than you ever wanted to know about PRR F's. They are available from the PRRT&HS.

[GN-Rick]

Gearing is a customer order item independent of the locomotive
model itself-the gearing is in the trucks and they are completely
interchangeable-as is the gearing in the individual trucks. The
owner railroad had only to change out the wheelset with its ring
gear to one of a different number of teeth and install a suitable
pinion gear on the traction motor shaft and thus change gear
ratios.

[Anonymous]

Gee, Andy's answer was pretty clear to me. I would think the only reason that there would be any problem mixing units would be a mis-match in gearing between F3's and F7's that would cause some excessive RPMs in the traction motors. You may encounter a similar "speed"/ gearing problem between your F3's and F7's, particularly if the "faster units are "pushing" the slower ones.

[dknelson]

One amendment to Dave H's post -- at one time the PRR, at least on some divisions, for some reason was strict about not mixing engines so they tended to keep F7s with other F7s, F3s with F3s and so on. By the mid 1950s they mixed things up freely.
One thing I never understood is how an FT could be mixed in with newer F and GP units sincd the FTs had a rather different transition system.
Dave Nelson

[Anonymous]

The CB&Q had some F3A-F3B-F-7A sets, and they even mixed FTs with the F-3s and F-2s.

[dehusman]

The PRR ran them mixed all the time.

Dave H

[Blackfoot69]

Andy,
your answer is fantastic and falls short of my requirements !
Thank you
Michel

[Sperandeo]

Hi Michel,

Not only did the Santa Fe freely mix its passenger F3s and F7s in the 1950s, it gradually upgraded and rebuilt its F3s until it was often dificult to tell them from the F7s except by the number series. For all you probably will ever want to know about Santa Fe F units, go to the Santa Fe Ry. Historical & Modeling Society Web site at www.atsfrr.net and look under "Online Resources."

So long,

Andy

[Blackfoot69]

Hello, [:)]
Is it possible to see F3 A/B running with F7 A/B ?
I have Genesis F3 A/B Santa Fe Warbonnet and I would like put them with the new Genesis F7 A/B and the new cars Super Chief ... I don't know if it's right or completely unrealistic and stupid ? [:I]
thanks
Michel