DL&W Diesel Gear Ratios

I have seen where DL&W F units in the 650 - 660 series had 45 mph 65:12 gearing and also heard of units having a 48mph gearing.

Is there such a thing as a 48mph gearing and if so what ? Mathematically it doesn't seem to work out.

Were lower geared units eventually re-geared before the EL merger ?

I think that such a ratio did exist. I have a book about the O&W diesels, and they had the low gearing. I have heard that the Lackawanna had sets with low gearing for running through Scranton.

The DL&W did indeed own some F units with low gears. They were used as pushers in the Poconos.

Indeed I know and acknowledge they had low geared units. I understand the 65:12 ratio at 45mph BUT my question was: is there a 48mph gearing as has been implied in some roster info ? Mathematically I can't work it out, and neither can I find any EMD literature. I suspect that DL&W had a TT restriction of 48mph max on the 45mph gearing to account for an overspeed. If anyone has more clarification or data it would be appreciated.

Secondly, did the low gearing last until the merger in 1960 with ERIE or were they regeared sometime prior as advances in traction motor technology developed ?

I think what you are looking at is the difference between 40" and 42" wheels.

I have always thought that top speed for older EMDs with 40"wheels with 65:12 gears was 55mph, is that wrong?

I always thought 40" wheels with 65:12 was 45mph

62:15 is 65mph with 40" wheels

Yes that's what I have
all 40" wheels
62:15-65mph
61:16-71
60:17-77
59:18-85
58:19-92
and the 65:12--55 mph

RSD15: You may be onto something.

My EMD FT book, Manual 259 Section F (1945) equates 65:12 gearing with 45mph maximum speed with 40" wheels.

I gotta study this out more as I see on the internet 55mph. I have nothing from EMD sources on 55mph, but guess I better go back and recrunch some numbers. I am missing something ...

Now I am confused !

Working off a nominal 4.1:1 ratio for 62:15, 74:18 (GE/ Alco) ratios that tradationally have stood for 65mph speeds I then find that 65:12 = 5.41:1

The ratio between the ratios is about .759 which would be 49mph.

Maybe I am not doing this correctly or maybe the motor speed was set at a safe level below the calculated threshold due to more possibility of overspeeding and damaging the motor due to excessive rotating speed. With newer technology those imposed thresholds were increased as the motor could withstand higher rotating speeds ?

Wish I knew more.

looking at the ratio of the wheel circmferences looks to make it plausible that a 45mph locomotive with 40" wheels would be a 48mph locomotive with 42" wheels - 45 x 1.06 = 47.7

the rest of this I guess will have to be weighed in on by others who understand this better than I do.

65:12 ratio was not only very slow but expensive. 12 tooth pinion was so small it could not be sweated on amarture shaft as was conventional EMD practice on larger gears. It was instead part of the armature shaft making it non-standard and and obtainable at a large additional cost. Engrs operating units with 12 tooth pinions had to use extreme caution when starting trains to prevent break-in-twos due to the increase in tractive effort with these engines. If four units wouldn't start a train in #5 throttle position you could guarantee a train seperation when you went to #6. Conversely 62:15 (65 MPH Gears) units routinely started heavy trains in #6 & #7 throttle positions with out train seperations.