Trains.com

36" Dynamic Brake fans on SD38

8053 views
48 replies
1 rating 2 rating 3 rating 4 rating 5 rating
  • Member since
    December 2006
  • 1,879 posts
Posted by YoHo1975 on Tuesday, November 28, 2023 12:26 AM

Pictures of SD38s with 36" dynamics fans exist. They don't appear to be retrofits. 

 

Perhaps the exhaust stack change was an enhancement to the 38 because of the fan size restriction. 

  • Member since
    November 2021
  • 211 posts
Posted by JayBee on Saturday, October 28, 2023 11:38 PM

You are correct, Backshop.

  • Member since
    July 2016
  • 2,631 posts
Posted by Backshop on Saturday, October 28, 2023 3:34 PM

JayBee--just a small correction.  It used to be the McCloud River, now it's just the McCloud.

  • Member since
    November 2021
  • 211 posts
Posted by JayBee on Saturday, October 28, 2023 3:03 PM

All the SD38, SD38AC, and SD38-2 locomotives built for US Steel railroads, DM&IR, EJ&E, B&LE, and Orinoco Mining. were built with dynamic brakes. Also the 3 SD38s built for McCloud Railroad (now McCloud River RR), have dynamic brakes.

  • Member since
    April 2007
  • From: Bridgman, MI
  • 283 posts
Posted by bogie_engineer on Sunday, October 22, 2023 11:49 AM

Randy Stahl

 

I do not believe the 48inch fans will  fit between the exhaust stacks on some stack arrangements. Obviously the smaller 36 inch fans are lower horsepower so I assume that there is at least two brake grids for the lower HP fans, different than the higher HP . I dont have my 190 book with me or I would look it up but I think this is the case .

R Stahl

 

SD38's and SD38-2's had a unique exhaust manifold system where the stack was moved to be over cylinders 1 and 8 rather than over 2 and 7 as on GP's. With the stacks moved, two 48" fans will fit between the stacks. EMD Master Parts Catalog 190 Volume 2, Parts list D3110, Pages 12 &13 confirm the SD38-2 uses the same 18HP 48" fans as all the SD-2 variants. Here's the parts list:

https://www.rr-fallenflags.org/manual/emd-mpc-3110.pdf

Interestingly, there is no parts list shown for SD38 dynamic brakes - does that mean none were built with DB, seems doubtful?

Dave

  • Member since
    June 2004
  • From: roundhouse
  • 2,747 posts
Posted by Randy Stahl on Saturday, October 21, 2023 4:07 PM

cv_acr

 

 

 
YoHo1975
The question I had was why they would build it this way. When the SD39, SD40, SD38-2, SD39-2 all have 2x48" As noted the smaller fans absolutely does change the capacity of the dynamics. 

 

You'll also note that the GP38, GP40, etc. all have 1x48" fans. Almost like it has more to do with the number of axles or something........

 

Of course it does. It's one 700 amp grid per motor for 10K lbs of braking effort per axle. 

In dynamic brakes the control power comes from the AR10 alternator providing 975 motor field amps and 50(ish) motor field volts. Obviously the locomotive can create this low control power at idle, remember that the prime mover RPM increases only to provide traction motor cooling air. 

I do not believe the 48inch fans will  fit between the exhaust stacks on some stack arrangements. Obviously the smaller 36 inch fans are lower horsepower so I assume that there is at least two brake grids for the lower HP fans, different than the higher HP . I dont have my 190 book with me or I would look it up but I think this is the case .

Maximum braking effort occurs only when grid current is 700 amps and traction motor field amps is 975 amps period.

It is noteworthy that locomotives that have higher current grids have different braking characteristics.

 

R Stahl

  • Member since
    July 2016
  • 2,631 posts
Posted by Backshop on Monday, September 25, 2023 8:45 AM

With some of the big terminal roads buying used SD40s and removing the turbos, there may be more "SD38s" out there now than were built new.

  • Member since
    December 2006
  • 1,879 posts
Posted by YoHo1975 on Friday, September 22, 2023 3:30 PM

Well and given that our Resident former EMD engineer has not found any info on the subject. I'm content to leave it as unknown.

 

I didn't even know they were smaller until someone corrected me on it. I always find the engineering knowledge interesting.

  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 13,892 posts
Posted by wjstix on Tuesday, September 19, 2023 2:37 PM

Since nothing definitive has turned up, it could be there really isn't an answer - at least not an answer beyond "because an EMD engineer in the 1970s did some calculations and determined that was the size it needed to work properly".

Stix
  • Member since
    October 2008
  • From: Canada
  • 1,820 posts
Posted by cv_acr on Monday, September 18, 2023 2:02 PM

YoHo1975
The question I had was why they would build it this way. When the SD39, SD40, SD38-2, SD39-2 all have 2x48" As noted the smaller fans absolutely does change the capacity of the dynamics. 

You'll also note that the GP38, GP40, etc. all have 1x48" fans. Almost like it has more to do with the number of axles or something........

  • Member since
    September 2023
  • 1 posts
Posted by GWRR on Friday, September 15, 2023 9:29 AM

Dave, 

Can you send me a PM at Nicholas.longshore@gwrr.com

Nick

  • Member since
    July 2016
  • 2,631 posts
Posted by Backshop on Saturday, September 9, 2023 12:36 PM

Whatever the size of their dynamic brake fans, the SD38-series have always been my favorite diesels.

  • Member since
    December 2006
  • 1,879 posts
Posted by YoHo1975 on Saturday, September 9, 2023 10:38 AM

The drawing clearly shows 36" fans.

And yeah, the SD38-2s had 48" fans so unless the 38-2 has a physically longer car body, it makes sense they would fit. 

 

I know the dash-2 was longer, but I don't personally know if the carbody is longer or if it was just the porches 

  • Member since
    April 2007
  • From: Bridgman, MI
  • 283 posts
Posted by bogie_engineer on Friday, September 8, 2023 1:51 PM

timz

Looking at the drawing on the last page of the link below, I wonder if two 48-inch fans would fit between the SD38 exhausts

I can confirm that two 48" fans will fit between the exhaust stacks on a 16-645E engine. In the 1970's, I had design responsibility for roots blown engine exhaust manifolds and designed the spark arrester-silencer exhaust manifolds that were required on locos built starting 1-1-1980 to meet EPA noise regs. Those manifolds had 10" round exhaust stacks rather than the oval stacks on prior manifolds and were designed to fit between two 48" fans on the SD38-2, even though no SD38-2's were built after 1979.

Dave

  • Member since
    February 2005
  • 2,366 posts
Posted by timz on Friday, September 8, 2023 10:56 AM

Looking at the drawing on the last page of the link below, I wonder if two 48-inch fans would fit between the SD38 exhausts

EMD Locomotive Specification Book SD38-SPEC8058-01JUN65.pdf (wildapricot.org)

If anyone has an SD38 service manual, it likely will show whether it can absorb 3800 horsepower in dynamic, like the SD40.

 

  • Member since
    January 2002
  • 4,612 posts
Posted by M636C on Thursday, September 7, 2023 8:57 PM

The Victorian Railways purchased 24 locomotives that were basically SD38s.

The first four units were built with 16-567E engines, 645E engines fitted with 567 power assemblies and the next two were built with 16-567C engines recovered from wrecked cab units. These were model G16C. The next eighteen units were model G26C with 16-645E engines. All of these had SD38 radiators with two 48" cooling fans.

However, they all had export type dynamic brakes mounted forward of the engine, with a single 48" fan. These had shorter but deeper grids behind a basically square ventilation grille. I understand for radiator fans, two 36" fans are equivalent to a single 48" fan.

So these must have had similar limits on dynamic braking to an SD38 with two 36 DB fans.

Several of these locomotives were rebuilt with 16-645E3 engines and larger radiators, but retained the single 48" dynamic brake fan. Strangely, a number of new locomotives were built to this design with the 16-645E3 engine.

So clearly, even an SD40 could operate with the smaller dynamic brake capability.

Peter

  • Member since
    November 2021
  • 211 posts
Posted by JayBee on Thursday, September 7, 2023 7:57 PM

Here is a link to a photo of B&LE 862, an early SD38 that predated the air filter box and never received one. It is also taken from a high enough elevation that you can clearly see that it has one older style fan and one newer style fan. Using 48" fans would bring the fan shroud 6" closer to the exhaust stacks.

B&LE 862

  • Member since
    February 2005
  • 2,366 posts
Posted by timz on Thursday, September 7, 2023 6:21 PM

Far as we can see, the two grid fans on B&LE 865 are the same diameter. But they're clearly smaller than the 48-inch? radiator fans.

Was there room for two 48-inch grid fans between the two engine exhausts of an SD38?.

  • Member since
    July 2016
  • 2,631 posts
Posted by Backshop on Thursday, September 7, 2023 4:12 PM

I wonder if it could have something to do with the later units having shorter radiator grilles.  They got rid of the middle partition and shortened it. That would allow room for the bigger fans.

  • Member since
    December 2017
  • From: I've been everywhere, man
  • 4,269 posts
Posted by SD70Dude on Thursday, September 7, 2023 2:37 PM

Here is DMIR 200 during its earlier life as Bessemer & Lake Erie 865.  Look at the DB grid, the two fans are different. 

http://www.rrpicturearchives.net/showPicture.aspx?id=4177352

Greetings from Alberta

-an Articulate Malcontent

  • Member since
    April 2007
  • From: Bridgman, MI
  • 283 posts
Posted by bogie_engineer on Thursday, September 7, 2023 1:59 PM

YoHo1975

No need to defend EMD's honor here. Nobody is questioning whether this would work. The question I had was why they would build it this way. When the SD39, SD40, SD38-2, SD39-2 all have 2x48"

As noted the smaller fans absolutely does change the capacity of the dynamics. 

 

No doubt EMD had a reason. What was it?

 

I have no answer for why if EMD built them this way. I checked the parts catalog and there is no listing for SD38 with 36" fans. Could it be these were delivered without dynamic brake and the RR added it later with parts from an earlier model?

Dave

  • Member since
    December 2006
  • 1,879 posts
Posted by YoHo1975 on Thursday, September 7, 2023 8:33 AM

wjstix

 

 
cv_acr

 wjstix

 

 

I think the bottom line is that EMD knew what they were doing, that they determined the SD38 would work fine with the fans they used. Since the SD38s have worked for decades without any problems relating to the dynamic brakes, I'd have to assume EMD was correct.

 

 

No need to defend EMD's honor here. Nobody is questioning whether this would work. The question I had was why they would build it this way. When the SD39, SD40, SD38-2, SD39-2 all have 2x48"

As noted the smaller fans absolutely does change the capacity of the dynamics. 

 

No doubt EMD had a reason. What was it?

  • Member since
    December 2017
  • From: I've been everywhere, man
  • 4,269 posts
Posted by SD70Dude on Wednesday, September 6, 2023 3:54 PM

On the other hand, some railroads would have sought a lower HP six axle unit (same high tractive effort at low speeds) for service on steep grades.  Northern Alberta's four SD38-2s are an example, they were purchased specifically for heavy trains between CN's Great Slave Lake Railway and the NAR terminal at McLennan, this run involved descending and then climbing out of the Peace River valley, with long 2% grades in both directions.  Dynamic braking was definitely a bonus here. 

Greetings from Alberta

-an Articulate Malcontent

  • Member since
    January 2001
  • From: Atlanta
  • 11,971 posts
Posted by oltmannd on Wednesday, September 6, 2023 3:03 PM

Backshop

I don't think the majority of SD38-series locomotives had dynamic brakes anyways. Many were bought for hump and transfer service.

 

Yes.  PC bought U23Cs and SD38s for yard service w/o DB.  The SD38s got six axle slugs in their Conrail years.

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

  • Member since
    July 2016
  • 2,631 posts
Posted by Backshop on Wednesday, September 6, 2023 12:39 PM

I don't think the majority of SD38-series locomotives had dynamic brakes anyways. Many were bought for hump and transfer service.

  • Member since
    January 2001
  • From: Atlanta
  • 11,971 posts
Posted by oltmannd on Wednesday, September 6, 2023 12:06 PM

YoHo1975

Looking at pictures,

SD39 appears to universally have 48" Dynamics fans. I would expect SD38 and SD39 to match on this.

 

Yes.  Six D77 traction motors should need 2 48" fans on the DB hatch to provide standard amperage for DB.  If you plop 36" fans up there, your max amperage for full DB would be reduced.

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

  • Member since
    February 2002
  • From: Mpls/St.Paul
  • 13,892 posts
Posted by wjstix on Tuesday, September 5, 2023 2:31 PM

cv_acr

 wjstix

It would make sense to me, since an SD-38 had much lower horsepower, it's motors would generate less heat, so would require smaller fans?

 

The HP is of the diesel prime mover, not the electric traction motors, which are probably exactly the same as an SD40. So quite against what you're suggesting, it makes more sense that the DB capacity is the same, since it's the same set of traction motors, so that's based more on the number of axles/motors and irrelevent to the engine HP.

 

Both used a V16, but the SD40 was turbocharged, as was the SD39 and SD45. Wonder if that has anything to do with the different fans? 

I think the bottom line is that EMD knew what they were doing, that they determined the SD38 would work fine with the fans they used. Since the SD38s have worked for decades without any problems relating to the dynamic brakes, I'd have to assume EMD was correct.

Stix
  • Member since
    December 2006
  • 1,879 posts
Posted by YoHo1975 on Thursday, August 31, 2023 3:47 PM

Looking at pictures,

SD39 appears to universally have 48" Dynamics fans. I would expect SD38 and SD39 to match on this.

  • Member since
    January 2001
  • From: Atlanta
  • 11,971 posts
Posted by oltmannd on Wednesday, August 30, 2023 7:11 PM

Hazy memory...  SD40 in N8 160 gal/hr.  SD38 in N8 120 gal/hr perhaps?  (I should look it up.)

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

Join our Community!

Our community is FREE to join. To participate you must either login or register for an account.

Search the Community

Newsletter Sign-Up

By signing up you may also receive occasional reader surveys and special offers from Trains magazine.Please view our privacy policy