Four axle dash 7's and transition speeds

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Four axle dash 7's and transition speeds

Postby Spur44 » Mon Apr 23, 2018 4:03 pm

Hi everyone! New to the group here and looking for a little information, mostly on the GE -7 line. Surfing through some old threads, I saw where the GTA11 alternator was used on the B23-7, B30-7 and early B36-7s. Then around '84 or '85 they received the GTA24. One of the big orders I can think of that would have gotten the GTA24 would have been the Seaboard System B36s that came along in the mid 80s.

Anyway I read that the GTA11 made traction motor transition and here lies my question. At what speeds were forward and backward transition made for the GTA11, specifically for the B30, B23 and early B36s.

Since the GTA11 was a carry over from the old U boat series, did the -7s and U boats have the exact same transition speeds?

With the GTA24 being a transition alternator, at what speeds did it make transition as well?

Thanks in advance! Any help would be greatly appreciated!
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Re: Four axle dash 7's and transition speeds

Postby WVU » Mon May 14, 2018 9:22 pm

The B23-7, B30-7 & C30-7 would make Traction Motor Transition from Series to Parallel (Forward Transition) at 23.9 mph and would make (Backwards Transition)
Parallel to Series at 22.5 mph. These units were equipped with CHEC I Excitation.

The B36-7 and C36-7 would make Main Generator Transition. The Alternator starts out in PARALLEL and at 31 mph it makes Transition and the windings are changed to Series through the pickup of AS1 & AS2 Contactors. At 29 mph the Generator changes back from SERIES to PARALLEL. These units had CHEC II Excitation Systems.

I still to this day miss working on and Troubleshooting the GE Series 7 Locomotives. We use to work a lot of them at CSX Huntington Heavy Repair Shop. We would hook these units up to our Loadcells and give them a good loadtest and Calibrate them and give them a good Track Test against our SD45-2 HLS1.
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Re: Four axle dash 7's and transition speeds

Postby Spur44 » Sat May 19, 2018 9:25 am

Thank you for that information! Good stuff!

Since the B30-7, B23-7, U30B, U23B and U36B all used the GTA11 did they all share the same transition speeds or did that vary between model?

How did testing against the HLS1 work?
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Re: Four axle dash 7's and transition speeds

Postby WVU » Sun May 20, 2018 2:47 pm

The B23-7, B30-7 & C30-7 shared the same transition speed. I will have to investigate the "U" Boat Series, for now not sure about them. You asked about HLS1. HLS1 is a True SD45-2 still with a 20 cylinder block that cranks out 3600 Horsepower. HLS1 is on our Test Track at the Huntington Heavy Repair Shop. What we do is we hook them up together, that being the Locomotive that has just been repaired and we run it against HLS1. One Unit will be in Dynamic Braking while the other unit is in Motoring pushing and pulling. And then we change things around and put the unit we are testing in Dynamic Braking and let HLS1 push and pull it. It is a very good test to perform.
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Re: Four axle dash 7's and transition speeds

Postby WVU » Mon May 21, 2018 7:40 pm

I got to checking into Transition Speeds on the U23B, U30C and U36B. For now I still cannot come up with data for the U30B.

U23B that the Chessie System had was Units 2300 thru 2326 forward Transition was at 20.5 mph and Backwards was 19.0. Chessie System U23B units 2327 thru 2329 had Forward Transition at 24.0 and Backwards Transition at 22.5 mph. The L&N U23B made Forward Transition at 25.0 and Backwards Transition at 23.5 mph.

The U30C made Forward Transition at 24.0 mph and Backwards Transition at 22.0 mph

The Seaboard Coast Line U36B made Forward Transition at 29.2 mph and Backwards Transition at 27.7 mph. The B36-7 with CHEC II Excitation made Generator Transition at 31 mph.
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Re: Four axle dash 7's and transition speeds

Postby Spur44 » Mon May 21, 2018 8:52 pm

Ok pardon my ignorance since the inner workings are greek to me but what I gather is the generator had absolutely nothing to do with determining the transition speeds since you had three different U23B orders, with completely different sets of transition speeds but all had the GTA11. So what exactly in the electronics made the difference?

I was really surprised to see that much difference in the same loco model.

Thanks again for sharing your knowledge!
Last edited by MEC407 on Tue May 22, 2018 12:10 pm, edited 1 time in total.
Reason: unnecessary quoting
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Re: Four axle dash 7's and transition speeds

Postby WVU » Tue May 22, 2018 8:20 pm

I don't know what to tell you about the difference's in Transition on the U23B. I am sure you noticed that on the Chessie System U23B we did have two speed differentials one making at 20 mph and the other at 24 mph. I will admit that is a big difference, my guess without truly knowing is that they were ordered from the factory that way to the specifications that the Chessie System wanted. You have different types of Speed Event Panels for different units. You maybe able to tweak Transition settings slightly, but you will not be making huge changes in when Transition will occur. The one that made Transition at 24 for the Chessie System and the one from the L&N were close together at 25 mph. Maybe those two units were made in the same time frame and the one for Chessie which made it at 20 mph might have been a much earlier model.

The U36B would make Transition at 29 mph and the more modern version the B36-7 would make Generator Transition at 31 mph. I got to looking at some information on the B23-7 that made Generator Transition at 29 mph.

Let me mention something to you about EMD Main Generator Transition with the SD50 and the SD60. These two units had the same AR11 Main Alternator. When the 50 was built the earlier models were 3500 HP and the newer 50's were 3600 HP and these units were designed to make Transition at 25 mph. The SD60 was a 3800 HP unit and it made Transition at 27 mph. My point is the same Alternator but different Transition Speeds.

The SD40-2 unit has an interesting Transition Circuit. It is controlled by Voltage/Current. Even though E/I controls it, it usually happens around 23 mph. Lets say you got a SD40-2 pulling a bunch of coal cars and it makes Transition at 23 mph but the load is so great that it pulls your train speed back down and you make backwards transition, what will happen is a Transition Delay Circuit will kick in and allow Transition to happen at 28 mph. EMD figures that the added speed will get you over the hump and keep you in Parallel.

The U Boats were a Locomotive that I did work on a few but not very many. I am not as up on this class as I am the GE Series 7 units that had CHEC I and CHEC II Excitation.
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Re: Four axle dash 7's and transition speeds

Postby Allen Hazen » Thu May 24, 2018 9:08 pm

I think Chessie 2300-2326 and 2327-2329 were part of the same order, delivered to C&O in 1969: the first U23B built with AC/DC transmission.
Why the difference? Two possibilities: in service modifications, or ordered that way at the outset. Since the three with the higher transition speeds are together in numerical order, at the end of the series, my bet would be on C&O ordering them that way. Maybe they thought the lower speed transition was PROBABLY the best for their needs, but wanted to experiment. Or maybe GE said "We've got a new idea we'd like to test. Would you be willing to let us test it on the last three units of your U23B order?" And C&O, for whom GE's were a bit of an experiment anyway (they bought lots more EMD units, and their subsidiaries B&O and WM were exclusively EMD in the 1970s) agreed.
(But those are guesses.)
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Re: Four axle dash 7's and transition speeds

Postby Engineer Spike » Fri May 25, 2018 1:40 am

It may be off topic, but I noticed the CPR SD40-2 made forward transition at 23 mph, but backward at 18. Maybe this is a customer specified option, just like the different transition points between the Seaboard and Chessie units. Sometimes the gearing may be different, or even the use of 40” vs 42” wheels.

I read about BN using run through power and changing PF cards. This was so the foreign unit behaved the same as their own in a consist, and loaded along the same power bands.
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