On the NYC FM C-Liners, the rear of the roof houses four fans. Does anyone know how these four fans function? Do all four run at the same time? Do some kick in at a later time depending on the heat of the locomotive prime mover? Do they run at different speeds depending on the heat or are they either on or off? Thanks in advance.
Note that the number of fans varies with the engine horsepower (some have only three) which will give you some assistance. I do not know if all the fans ran together with carbody shutters assisting in regulating cooling ā someone here will know this or have a source such as an operatorās or service manual that describes it.
My instruction book on the Pennsy FF3 (1949) shows that the fan motors are actuated by a switch on the shutter control lever. There are three shutter servo motors operated by the engine oil pressure. Two operate the radiator shutters, one for each side. The third operated the rear heat exchanger.
When the shutters are partly open the fan switch closes the slow speed switch and as the shutters move to fully open the cam in the motor control switch contacts the high speed motor control.
There are also manual override switches in the engine compartment plus recommendations for fan speed selection based on ambient operating conditions (outside air). If you want I can scan the full document. Thereās considerably more here than simply the fan operation.
I hope Larry is still with us after eleven years 
Regards, Ed
Ed, the post was on the new forum in December 2024; the software was only commenting that it was his first post in 11 yearsā time. He would still have been very much with us five months ago.
Thank you, all, that expressed concern over my health and increased my knowledge about FM roof fans. Yes, I am still here but my health in the past was much better. I wrote a long response to Woke_Hoagland only to realize that the return email address was a ādo not reply to this email addressā. Remember, Iām a newbie! I will re-write my response to Woke, if I may call you by your first name, and hopefully start a hot discussion on FM roof fans. I have designed a circuit that controls each fan for an AHM/Rivarossi O scale C-Liner and want to duplicate the fan function as best as I can. I have to go to a doctorās appointment so I will continue this later, hopefully tonight. Thanks, again, for your concern over my health. Itās appreciated and welcomed and yes, I did write that book review on the L&HR!!!. Lar P.S. I have also designed a circuit that lights a sleeper/slumbercoach that could be used in HO and up PLUS I am working on a test track that the industry has never seen.
I have been trying to find my copy of the PRR early diesel manual ā Ed and I may have the same one; it uses the old PRR diesel scheme before they started using the manufacturer/service - horsepower scheme.
Mine is a booklet assembled with what I remember as screw posts, so it might be involved to get pages to lie flat for scanning without a book scanner.
I donāt remember how the early FMs drove the fans. If I remember correctly the āoil pressureā moved the shutters, but the control was electric valves controlled thermostatically, not a proportional control based directly on something like a wax motor. The āoverrideā and seasonal controls are going to be important details ā iirc some makers advocated blanking some of the available shuttered area in severe cold conditions, for example.
Un-screw the posts and remove the needed pages? Thatās how our steam turbine instruction books were assembled.
Thatās why theyāre designed that way, and what Iād do to scan them if the posts havenāt seized.
Iāll scan the FM pages tonight. Right now I have to get firewood stacked. Winterās cominā you know!
The book I have is titled:
The Pennsylvania Railroad
Diesel Electric Road Locomotives
Operating instructions
For Locomotive Enginemen, Firemen and Helpers
1949 Approved by none other than H.T. Cover; Chief of Motive Power
Cheers, Ed
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Meanwhile, look through this:
WOW! Thanks for all the info everyone. Where were you all in December as I was dying? {8^) Are any of you into models or just the prototypes? If you didnāt get the reference I made to the L&HR book, thatās OK. Itās not you. From what Iāve gathered so far, and I havenāt yet read everything that was posted, my circuit has two fans running off of the DC current and two fans running off of a 555 timer chip. All four fans run at different speeds and some cut in and out but they all run clockwise no matter the loco direction. Iāve never seen anything like it but it really can only be done in O or larger due to the 4 motors and their size. Thanks again.
Maybe Iām the only one who got this notification?
It told me you havenāt been around for 11 years? What am I missing?
Anyway, here are the pages concerning the operation of the fans on the Pennsyās FF-3s:
The FF-3 (Later FF-20) was the āErie Builtā on the PRR but I imagine the fan arrangements would be similar.
Good Luck, Ed
Thank you, so much, for the fan info. To set things straight, I am not near death nor have I ever been. The reference, I believe, is to a book review I did on the L&HR in the early 2000ās. I sent the review to the author who then used it to promote his book on a forum of which I was not a member and did not know he had done that. A forum member accused him of making up the review and that I did not exist. Flash forward, I found the post, joined the forum and announced that I really did exist. Iāve chaired over 20 train shows and the 2013 National O Scale Convention.
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