Another MU question

[brokemoto]

I have read in many places that the main consideration when MU-ing diesels is the gearing.  The horsepower can be way different among the units but the gearing must be close.

Considering this, could you MU two locomotives if one has a 68:19 gear ratio and the other one a 63:15 gear ratio.  They work out to 3,54 and 4,2 respectively.  Is that close enough or do they  need to be closer?

[Curtis Kyger]

Actually, I believe the major consideration is with the brake systems. As example, you cannot lead a consist with a unit having a 6BL brake system if the other units have 26L.
Another consideration is transition -- a manual transition F3 cannot trail an automatic transition equipped F7.

[sd45elect2000]

I have read in many places that the main consideration when MU-ing diesels is the gearing.  The horsepower can be way different among the units but the gearing must be close.

Considering this, could you MU two locomotives if one has a 68:19 gear ratio and the other one a 63:15 gear ratio.  They work out to 3,54 and 4,2 respectively.  Is that close enough or do they  need to be closer?

Gear ratios do play a part as well as air brake compatibility . 62:15 gears are rated for a max of 68 mph. Above that speed the armatures come apart. In addition a higher ratio means that the motor will stay in the short time current ratings much longer possibly burning up the motor.. 26 L can trail 6 or 24 if equipped with an MU2A valve only, however depending on how the sanders are configured (mu electric vs air) that may not be controllable. Certainly the types of transition is important automatic transition locomotives cannot control manual transition engines making the consist worthless above 22 mph.
Another consideration is the type of dynamic brake. A train line potential engine won’t work with field loop control.
Your example gear ratios are ok to use together is the higher gear ratio engine is leading and not exceeding 68 mph. The load meter will show the more acceptable current short time rating preventing motor damage.

Randy

[brokemoto]

Thank you for the answers so far.  I did not know that there were so many factors to consider

-- a manual transition F3 cannot trail an automatic transition equipped F7.

It is interesting that you raise this example.  I had read in places that the railroads could not MU some power built in the 1930s or 1940s with some power built in the 1950s and later because the MU plugs were different.  It seems that if the braking systems were different, you also could not MU them.  F-3s were built from about 1946-1949; F-7s from 1949 to about 1953 or -54.  I would guess that some roads did update brake systems on F-3s or FTs, as time passed so that they could all run with each other.

It did take until 1958 before the builders that were left all agreed on the same MU plugs.  Before that, you could buy adapters.  When it came to Baldwins, if you wanted to run them with the others, you had to buy a rather expensive adapter.  Few roads did.  Oliver iron Mining did, as it wanted its switchers with cabs to be able to control any of the switcher "B" units from Alco, EMD or Baldwin.

The F-3/F-7 mention prompts me to mention the specific prototype that led to my question.  Can you run an FM Erie with a C-Liner?  The Eries were built from 1946-1948 (?).  The C-Liners were built in the 1950s.  The Eries had 68:19 gearing (3,54:1) wile the freight C-liners had mostly 63:15 (4,2:1).  Thus, according to what another poster responded, the C-Liner would have to lead.  You could not run an Erie A with a C-Liner B, but you could run A-A, as long as the C-Liner leads or run a C-Liner A with an Erie B.

 The freights on my pike usually run at about twenty five miles per hour, so speed is not a major concern.

[sd45elect2000]

Thank you for the answers so far.  I did not know that there were so many factors to consider



It is interesting that you raise this example.  I had read in places that the railroads could not MU some power built in the 1930s or 1940s with some power built in the 1950s and later because the MU plugs were different.  It seems that if the braking systems were different, you also could not MU them.  F-3s were built from about 1946-1949; F-7s from 1949 to about 1953 or -54.  I would guess that some roads did update brake systems on F-3s or FTs, as time passed so that they could all run with each other.

It did take until 1958 before the builders that were left all agreed on the same MU plugs.  Before that, you could buy adapters.  When it came to Baldwins, if you wanted to run them with the others, you had to buy a rather expensive adapter.  Few roads did.  Oliver iron Mining did, as it wanted its switchers with cabs to be able to control any of the switcher "B" units from Alco, EMD or Baldwin.

The F-3/F-7 mention prompts me to mention the specific prototype that led to my question.  Can you run an FM Erie with a C-Liner?  The Eries were built from 1946-1948 (?).  The C-Liners were built in the 1950s.  The Eries had 68:19 gearing (3,54:1) wile the freight C-liners had mostly 63:15 (4,2:1).  Thus, according to what another poster responded, the C-Liner would have to lead.  You could not run an Erie A with a C-Liner B, but you could run A-A, as long as the C-Liner leads or run a C-Liner A with an Erie B.

 The freights on my pike usually run at about twenty five miles per hour, so speed is not a major concern.

I don’t think the Erie engines were built with MU on the noses on some cases they were added later. The same can be said for the ALCo and EMD products of the time as well. Back in those days there was little standardization , some engines had 24 pin MU some had 27 etc.
if you wanted to run multiple engines of mixed type back in the early days, you pretty much had to use two engine crews.At least until the mechanical department came up with a plan to standardize their fleet.

Randy

[brokemoto]

I don’t think the Erie engines were built with MU on the noses on some cases they were added later.  if you wanted to run multiple engines of mixed type back in the early days, you pretty much had to use two engine crews.At least until the mechanical department came up with a plan to standardize their fleet.

I am running two locomotives per train at the most, except for switchers where I will run three.  Those are two NW-2s and an SW-9.

 The Erie will not need nose MU plugs.  I would run it only with one other FM.

If you did not want to use two crews, you had to buy adapters.  Up until the late 1950s, the railroads did avoid running units of two different builders in MU.  Western Maryland went as far as to issue orders that this or that unit could be run only with this or that one.  It allowed the operating of FA-2s with RS-3s but not F-7s.  It was not until the late 1950s that you would see the F-units and RS-3s in MU on the WM. 

Baldwins were a spacial problem due to their pneumatic throttles, although you could order them with Westinghouse electric throttles.  I have seen a video of a Pennsylvania passenger train on the NY&LB that had a Baldwin passenger shark in the lead and an E-7 behind it; both with crews.  The Penn did not order any Baldwins with electric throttles, to my knowledge.  The E-7 was in single stripe, so that would date it to the late 1950s up to the mid 1960s.  Still, you could not MU an EMD to a Baldwin due to the Baldwin's pneumatic throttle.