What are the differences between SD50 and SD60.

Whats the difference between an SD50 and SD60 the units look the same.

If you think they look the same YOU AREN'T a TRUE FANATIC! There are a few subtle differences in hood doors etc. (Grin!)

The serious differences are that the SD-50 had a 3500 hp (3600 in later production) 645F engine and (except for a few testbeds for the SD-60's stuff) a control system similar to that on an SD40-2. The SD-60 had a 3800 hp (4000 in later production) 710G engine (one-inch longer piston stroke: first DIMENSIONAL change in the EMD engine since the introduction of the 645 in the mid 1960s) and microprocessor controls.

Since it has a 645 engine, you can convert an SD-50 into an SD-38-equivalent by removing the turbocharger and installing Roots blower, using parts that are widely available. Roots blowers for a 710 engine don't exist (they could, in principle, be produced, but it would involve new engineering design and couldn't be done affordably for the small likely number of customers), so an SD-60 can't be down-rated in this manner.

I can tell you on Conrail SD50s, the horns were over the cab just above the headlight. On their SD60s, the horns were mounted on top of the long hood, halfway back on the units.

Charlie

Operational wise the SD-60 far outshines the SD-50. the SD-50 were prone to excessive wheel slip due to the radar type system they had. I have found memories of them just quitting (shutting down)out on the road on sub freezing nights ,and let me tell you the cab gets cold very fast at 50 MPH when the lead engine is dead,but all the trailing units are fine. You just keep going to the terminal. This was Conrail in the 1990's.

RDGTransMuseum--
Thanks for that! Reminiscences from people who actually worked with the locomotives are one of the things Railroad.com forums provide for us railroad enthusiasts who otherwise know them only from the outside: it is much appreciated.
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Interesting that you should mention wheel-slip problems. The SD50 (and GP50, and GE locomotives from the later part of their Dash-7 production) were the first that tried to use sophisticated control systems to give much higher adhesion (25% or more instead of the 18% that railroads counted on in the 1950s/1960s/early 1970s). My guess is that the radar system was fine... if working perfectly. And that the chances of that sort of high-technology working perfectly with typical railroad maintenance weren't anything you'd want to bet on.
...Conrail also had many of its SD50 built with "Flexicoil" trucks from traded in early SD units, instead of the standard HTC trucks the unit was designed for: can't have helped, since the HTC was designed for better adhesion (I ***think*** the first two letters of the designation are for "High Traction") than the older truck.

Allen Hazen wrote:If you think they look the same YOU AREN'T a TRUE FANATIC! There are a few subtle differences in hood doors etc. (Grin!)

The serious differences are that the SD-50 had a 3500 hp (3600 in later production) 645F engine and (except for a few testbeds for the SD-60's stuff) a control system similar to that on an SD40-2. The SD-60 had a 3800 hp (4000 in later production) 710G engine (one-inch longer piston stroke: first DIMENSIONAL change in the EMD engine since the introduction of the 645 in the mid 1960s) and microprocessor controls.

Since it has a 645 engine, you can convert an SD-50 into an SD-38-equivalent by removing the turbocharger and installing Roots blower, using parts that are widely available. Roots blowers for a 710 engine don't exist (they could, in principle, be produced, but it would involve new engineering design and couldn't be done affordably for the small likely number of customers), so an SD-60 can't be down-rated in this manner.

You can also convert a 50 Series locomotive to an 40-2 equivalent by changing a couple of electrical system modules and adjusting the fuel system settings...

It is correct that the HT means High Traction in th HTC designation. It isn't so much the capability of the bogie but it refers to weight shift characteristics, which are greatly improved compared to the SD Flexicoil - adhesion efficiency (the percent of static axle load on the lightest axle calculated at 25% adhesion) is about 78% on the SD Flex versus about 93% on the HTC. This is the result of the motors all on the same side of the axle and the stiff secondary vertical suspension.

Dave

I believe all our SD40-2 and SD-50's had the HTC? All i'm really shure of is that the SD40-2's could out pull an SD50 by a long shot.

I ***think*** that all Conrail SD40-2 and most if not all Conrail SD50 had the older, flexicoil, truck and not the newer HTC design (which was otherwsie standard on SD40-2 and SD50: just WHY Conrail specified the older truck I don't know: it may have been cost, if they used trucks from old SD that were being traded in, but also Conrail's first big locomotive orders were made about the same time as the kerfuffle about derailments of Amtrak's SDP40F locomotives, which used a version of the HTC).
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This means (if I'm right in remembering that Conrail ordered the same trucks on its 40-2 and 50 SD units) that the running gear was the same: both classes used a truck design whose weight-transfer characteristics, as Bogieman points out, made them "slipperier" than SD40-2 and SD50 on other railroads with the HTC truck. So, if SD40-2 pulled better than SD50... it sounds as if the SD50's sphisticated, radar-based, wheelslip control system was ... counterproductive!

On CSX we have 171 SD50 units and 91 SD60 units. Two of the SD50's are prototype SD60 units 8525 & 8526. 8526 has been upgraded to an SD50-3 unit. All of our SD60 units are basically the same except for two of these units, 8710 & 8711 which has the same Dynamic Braking Configuration as the SD50 units which has a 36 Horsepower Brake Blower Motor with .86 ohm Grids considered to be Low Capacity Grids and is rated for 750 amps of Braking Grid Current. In Dynamic Braking on the SD50, you will excite the Traction Motor Fields with 880 amps for Dynamic Braking for the Low Capacity Grids.
89 of the 91 SD60 units has a 100 Horsepower Brake Blower Motor with .632 ohm Grids considered to be High Capacity Grids that are rated for 945 amps of Grid Current. On the SD60 units with the High Capacity Grids, you will excite the Traction Motor Fields with 1100 amps for Dynamic Braking.
Some more differences is the obvious difference in the engine. The SD50 has the 645 engine and it was rated for 3500 HP on CSX units 8500 thru 8603 with the LC114 module. The 8604 thru 8643 was rated for 3600 HP and it had the LC118 module. The SD60 units have the 710 engine and it is rated for 3838 HP.
The SD50 & SD60 units both make Main Generator Transition. The AR11 will start out in Parallel and when making transition, the SGC contactor will put the AR11 into Series. The SD50 will make transition in the area of 22 to 25 mph. The SD60 will make transition at 27 mph.
Both of these units have what is called Super Series Controlled Excitation System with the SD50 using a card rack full of modules and the SD60 has the same system but it was broken down into three computers. The computers are Excitation, Display, and Logic.
The AR11 Traction Alternators in both the SD50 & SD60 are set and limited to produce 9900 main generator amps. If you take the 9900 main generator amps and divide it by six for the six traction motors that are in Full Parallel operation at all time you will arrive at the 1650 amps that you will see on the loadmeter on the control stand. The AR11 on both of these units have a Generator Ratio of 86.086/1. What this means, is for every Fied Amp that you pump into the Main Generator Rotating Fields of the AR11, you will get out 86.086 amps out of the AR11 for power in motoring. Both Excitation Systems are set for 115 Main Generator Field Amps.

WVU--
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More information there than I know what to do with! Thanks!
?? So (I think) both EMD and GE went to Main Generator Transition (with traction motors in permanent full parallel) at about the same time, in the late 1970s: EMD with the AR-11 generator used on the 50 series (replacing the AR-10 used on the 40 series), GE with the GTA-24 used on B36-7/C36-7 (replacing the GTA-11 introduced in about 1969). ??

Allen, I might be wrong, but I think The SD50 came out around 1981 with Generator Transition. For what I know, my experience with working on GE locomotives they came out with Generator Transition around 1985 with the B36-7 and the C36-7 with what I call CHEC 2 Excitation. (CHEC stands for Constant Horsepower Excitation Control). With the SD50, they also came out with Super Series Wheelslip Control that replaced the WST's that allowed 4 to14 % of wheelslip while GE came out with there version called Sentry Wheelslip that replaced the CMR wheelslip system. In my opinion both systems are good. Allen also with the SD50, to my knowledge is when they came out with the Super Series Excitation Control. EMD people don't want to hear this, but the SD50 was the closest thing ever, that EMD built that was like a GE unit.
The reason I say this is, for years GE had the CHEC excitation which monitored Volts, Amps & KW. This system is refered to as a perfect excitation system which is basically still used by GE and it is called Micro CHEC today. EMD had a great excitation system called Static Excitation used on the popular Dash 2 units and the Straight GP40 & SD40, but EMD will even tell you that it was not a perfect excitation system so when the SD50's came out there excitation system monitored Volts Amps & KW also. Today this system is still used on EMD units.

Thanks again! I didn't know that about the excitation systems.
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As for dates... I think sales of the new technology types took off slowly: a few were built a bit earlier than you remember. The first SD50 (prototypes, on short -- SD40-2 length -- platforms) were built toward the end of 1979: for units for KCS. (EMD's new control system may have been on the road for two years by then: the first "GP40X" -- GP50 prototype -- was built at the end of 1977.) On the GE side, the first B36-7 (B30-7 on the builder's plates, but rated at 3600 hp and ***I assume*** with the control system that became standard on the B36-7) were four built for Cotton Belt in January 1980. (Dates from Withers, "Field Guide to Diesel Locomotives".)

You were at CSX. I'm not sure when SCX got its first SD50. (Some time about 1982 or 1983 or 1981 CSX cancelled an order for GE units and got EMDs -- GE apparently felt there was something underhanded (bribery? threat of traffic retaliation?) about EMD's success : there was a press-release from GETS complaining about how the competition had "somehow" induced CSX to cancel what had seemed like a firm order: the only time in all the years I have been interested in railroads that I have seen one locomotive builder come out publicly and accuse the other of dirty pool!) ... B36-7 didn't sell well at first, but Conrail bought 60 in 1983 and CSX, as you remember, bought 120 in 1985. ... Though, come to think of it, CSX's B36-7 had improvements over earlier orders: perhaps they were the first with the full "package" of control and generator upgrades. Though I am pretty sure earlier B36-7 had GTA-24 main generators (one source for that being "Extra 2200 South" reports when the B36-7 was new).

Allen, thanks for all the interesting information on GE & EMD from the late 70's and early 80's. Allen, I started working for the old Chessie System in October of 1978 when I was 19 years old. At that time we had an assortment of "U" Boats and a new order of GE B30-7 units. Allen, I work at the CSX Huntington Locomotive Heavy Repair Shop in Huntington West Virginia. Chessie System at that time had a predominantly EMD fleet. We would see GE's in Huntington, but most GE work on Chessie was done at Clifton Forge Virginia. Chessie and Seaboard merged on November 1, 1980 to form CSX. Seaboard had a much heavier fleet of GE units then Chessie had. Even though the two railroads merged into CSX, we did not start seeing more GE work in Huntington until CSX closed and moved the L&N South Louisville Shops to Hunitington in 1987 & 1988. Still at that time, most of the GE work was done at CSX Waycross Georgia shop. I cut my teeth on EMD units and working on GE units was kind of foreign to me. I loved troubleshooting EMD units. It took a while to get use to working on GE units, but I got to the point that I enjoyed working on them and I found them to be a challenge to repair and it was a challenge that I enjoyed. Allen from what I remember, the SD50 started showing up on CSX around 1982. And the B36-7 & the C36-7 did use the GTA-24 Main Alternator that made generator transition. Allen a lot of technology that was in the CHEC II B36-7 and C36-7 was put in a computer on the very popular Dash 8 unit. Allen, I would like to talk about the SD50 units. I know that the SD50 units had several issues that rail companies had to deal with. CSX hung in there with the SD50 units and in my opinion ended up making a pretty good unit out of it. The horsepower had been dropped down to 3000 but looking at it through the eyes of a troubleshooter a lot of the electrical issues had been resolved. I know that will raise some eyebrows and some people will say that I am blind, and maybe I am, but to me the SD50-2 is now a pretty good unit. I have noticied several SD50-2 units with governor rack problems. The rack should run at .88 but I have been noticing SD50-2 coming into Huntington running a .92 or .94 Rack with the Load Regulator running at 9 to 9:30 with only 24 to 2500 HP. I will not mention the name of the company that has remanufactured the governors, but they are not getting them set right. We have to adjust the balance point to .88 and we then get our load regulator running in maximum field and the unit will make the 3000 HP. EMD to me corrected the problems with the SD60 and to me, I think the SD60 is a good unit and I love troubleshooting them also. But in closing, I never seen a locomotive that I did not love to work on. Allen I have been Loading, Calibrating and Track Testing all types of Locomotives since 1992.