I pinned this as top comment. You are welcome to add this kind of insight to any videos, it was well written and articulated.

@@djstrains thanks brother, just love sharing all things trains and your channel is one of the best sources for the entirety of the railroad topic. You cover it all DJ, Cheers Rob hope maybe someday to hear one of those air starters. The big old C series Alcos had them, the sound neat 😁😁

The OP isn't entirely accurate. The key point is that power equals force times speed. A four-axle unit can't exert a lot of force on the rail. Not particularly because of the limits of traction motors but because of the limits of adhesion. If you compare a GP60 and an SD60, both have 3800hp, and the SD60 is about 50% heavier and has 50% more axles. Both have the same weight on each axle, which means that both have the same friction (grip) per axle. But, overall, there's 50% more friction between an SD60 and the rails than a GP60. And, by Newton's third law, that means the SD60 can exert 50% more force on the train. It's this increased ability to apply force to the rails (aka, tractive effort) that allows an SD60 to get a heavy train moving, or to haul it uphill. GP60s can do the same thing, except that you need 50% more of them. If your train needs two SD60s to get it moving, it would need three GP60s, even though the GP60s would have 11400hp vs the 7600hp of the two SD60s. If you try to put all 3800hp through the four axles of a GP60 at low speed, the force will exceed the friction between the wheels and the rails, and the wheels will spin. (Power equals force times speed, so high power and low speed means high force.) Indeed, for this reason, many four-axle locomotives have a control system that limits the power at low speed to about the same power per axle as a six-axle unit. This is why slugs are a thing -- instead of being unable to use the extra power at low speed, you put it into another locomotive's traction motors. At speed, putting all that power through four axles is fine, because the force generated is relatively low -- but still enough to keep the train moving. A six-axle unit could do just as well at those speeds, but there's no point hauling all that extra weight around. At least, that used to be the philosophy. Now they figure they may as well just use six-axle units for everything and save the inconvenience of having multiple types of locomotive. And you can't use a slug at high speed, because the mother-slug pair doesn't have enough power to generate enough force at high speed to keep the train moving.

@@beeble2003 Sincerely appreciated for the thorough explanation!

@@beeble2003 Correct! As speed increases, the load which the diesel and traction alternator can produce is reduced. An alternator feeding 4 motors can provide more power to each. This way higher speed can be sustained by a 4 axle. This is why high powered 4 axle power, like GP40/50/60 B30/36-7, B40-8, C430 used to be preferred in time sensitive service. With PSR this thought has largely gone away. More effort is put into high tractive effort and maximum tonnage.

we are so similar!!!

I have a lot of videos in my "life as an engineer" playlist that you might enjoy. More to come also.

This made my day!!

My uncle was an engineer there. He liked the GP38-2 best. I’ve logged thousands of miles on GP38s to. My uncle was right about their superiority.

Sounds like you have Maryland Midland close by... I love that they have the Sd45 carbodies with Sd40-2 guts. But it makes me mad they lost their Corporate identity

Glad it was helpful!

I sincerely appreciate your thorough explanation! Thanks!

@@djstrains I'm trying to offset the bad foamers! Lol!

That is awesome!

I appreciate that

I appreciate that!

Hello there!

That's the great part about the hobby sharing ideas and learning new ideas from other people to improve our Channel.

THIS IS SUCH VALUABLE INFORMATION!!! Thanks for sharing!!

Conrail also had tones of GP-38's that they ran on the main line up in Canada. why I fell in love with them as a kid, 4 or 5 GP-38 pulling over 100 cars. see this about 25 times a day. In St Thomas Ontario we had the Conrail main engine shops and Chessie had their main engine shop as well. their yard was full of GP-9

I’ve seen pictures of single SD50’s on Chessie coal trains.

OR MAYBE WE FILL THE TOILET WITHA BAG OF ICE TO KEEP THE SMELL DOWN.

Some do have engines. In my yard we have one proper slug without a diesel prime mover, and 3 that do.

Some may keep the prime mover as traction weight, but a slug by definition doesn’t use the prime mover for power. It gets it’s power from the mother unit.

Glad to help

Thank you! You too!

@@djstrains Your welcome and thanks also.

Love it!

You bet!

How many have the derailed in yard or customer facilities on less than perfect track?

I saw one yesterday, I'll watch more. Here is the only one I had recorded back with Brady Fry and also Jimmy Warren.kzfaq.info/get/bejne/eJymodKVqK2-m40.html

I do too

Thank you very much!

Glad it was helpful!

More to come.

hahahaha

How well does a "track-mobile" perform?

@@williamh.jarvis6795 very good actually. It's an old TM900. The sanders have been removed but it still pulls good. Don't get much trackage because only have about 200 yards to work on. But even with out sanders I'm pulling on fully loaded hoppers up a grade on a curve. It's awesome.

Glad you enjoyed it

in storage, lol.

I'm not DJ and he may have a different answer, but honestly the 4 axles can be rebuilt until the end of time. On the railroad where I work and it maybe the same with CSX, we have 4 axle EMD's that were built in 1968. All the parts are renewable from the traction motors, to the switchgear, rad fans, main generator and diesel engine. And all the parts are still available from EMD and other suppliers. On a side note, parts are big business and as long as the railroads need parts for 4 axle locomotives, they'll remain available. So you are correct and just my opinion but the largest locomotive you'll ever see on a local or yard service is a SD40-2, otherwise that type of service will remain the domain of the 4 axle EMD's. Sadly the 4 axle GE's were very slippery, an issue GE has since correct with it's 6 axle power. EMD hit it out of the park early with their IDAC Wheel Slip system introduced in the late 1960's and then they added to what they achieved with IDAC with the introduction of their "Super Series" Wheel Slip system, but that's a discussion way beyond this video. Sorry for being so long winded but I hope I answered your question? Cheers, Rich S.

@@RWSBaden excellent answer, thank you. I guess we will see if the market dictates new models. Rebuilts available or not there might come a time when the supply available outstrips the demand and new ones needed or the bean counters can’t justify an expense on something over 60 years old…..

CP rebuilt their GP9 fleet into GP20eco. BNSF had the GP28, with modern bodies and -2, which were rebuilt from GP9, the GP39 program rebuilt from GP30/35, and they had many rebuilt GP38s too.

million dollar question that I also want an answer.

HI DJ @@djstrains If I was to make a guess, Any new 4 axles would come from a third party supplier like the National Railway Equipment, Brookville, Railpower Technologies or MotivePower. My reasoning is based on what has happened over the past 40 years in the locomotive market. During the 1970's, a railroad could purchase a GP38-2, SD38-2, GP39 GP40-2, SD40-2 and SD45-2. Move forward 10 years and your choices from EMD were a GP50 and SD50, which ended up with 645 diesel engine trouble. Next came the GP60 and SD60. Yes there were a few odd ball test beds during the time that were only purchased by a few railroads like the Southerns GP49's and GP59's. Move to the 90's and what was the locomotive choices, SD70 and variants but with no 4 axle offered. Today you have two choices from EMD, SD70Ace or they will rebuild one of your older SD70's from DC traction motors to AC traction motors. Just the way I see it, but I don't see GE or EMD getting back into the 4 axle market, unless you consider EMD's rebuild programs will they'll take a older locomotive like a GP38 and convert it into a ECO locomotive with a Caterpillar 12 cylinder diesel engine and updated electronics. Sorry for the long answer DJ, but that is how I see the locomotive market over the next 20 years. Cheers Rich S.

on my patreon site I made a review video. KZfaq wont let me play it because I used too much footage.

New video at noon tomorrow you may like

Glad it was helpful!

I personally dont have any footage. Also, I did not get the opportunity to drive it, and the security around it makes it challenging. The management wont even talk to us peons.

Dont know if you seen this. Pretty interesting at least for me. kzfaq.info/get/bejne/auCKhNeJm9nMYmQ.html

You too!

also a "Depature test" on our positive train control.

Depending on the type of operation, there are different classes of tests that need to be done, and in some cases we don't have to perform any tests at all. Some tests require that all the brakes on every car set up, remain set for a certain length of time, and all release. Some tests only check that the brakes set up, but not release. There are separate types of tests that must be done on locomotives and not cars, and all of the tests required are determined by when you do them. If I'm just swapping crews on a road train that's already been air tested, I don't have to do any tests. Just get on and go. But if I pickup cars and/or locomotives, or setout cars enroute, there are air and equipment safety tests to do.

Glad you enjoyed it

Thank you kindly

gensets are garbage, lol.

Glad you liked it!

Yes. But there was none in the yard that day and no "ground air" lines in Neville island yard either, sigh.

There’d be less chance of another unit, jumper cables, or a welder being available if a junkGE had dead batteries.

Glad you enjoyed it

Man, KZfaq acts up all the time. I miss comments and sometimes up to a year before I catch it. Go watch the other 399 videos, lol!!

no, we have a few already.

Glad you enjoyed it

I know there's one, the crews treat it like the short straw when it comes to power. I remember I was getting off a transfer job up there and having to wait for a track to be shoved back in before I crossed the yard from my motor. I see a cut creeping by consisting well cars, loaded ballast cars, then a lone MP15 absolutely screaming as it tried to move the train. I was riding with some old head engineer who just grunted and said "And they wonder why their s**t breaks" under his breath

@@intermodalman123 yep, that's about how the operations were going when I was able to observe while the i-10 bridge was being placed over the yard.

Honestly, I get asked often, but have no interest in simulators, sorry.

@@djstrains what? You don't want to pretend to be back at work - and not getting paid!? grin ...

Thanks buddy!

Appreciate it

Glad you liked it!

Yes, on many occasions. Problem is many big engines dont have rear ditch lights. That means only 20 mph over a road crossing which may make for a very long day.

@@djstrains on some occasions the crew had brought portable ditch lights. Union Pacific doesn't have rear ditch lights on their big engines but I thought most CSX engines have ditch lights on both sides. Maybe im thinking of Norfolk Southern.

Most welcome 😊

HUMBLED AND GRATEFUL!!! THANK YOU SINCERELY!!!

You are very wise! Yes, the auto pilot feature sometimes has the dpu shoving while lead is in dynamic braking! I hate this, makes me feel like we gonna pop a car off on a curve!

It's like trying to compare a 2022 Ferrari with a 1970 Volkswagen Beetle. Which do you think they are going to invest this technology into? Even when we had manned helpers we used huge 6 axle engines. I was hoping this video explained what these 4 axle engines are used for.

@@djstrains That makes sense - The GP’s just don’t have the tech. My local RR, a short line, uses mostly GP’s for power.

@@djstrains It's also like comparing my truck to a bigger one. I have a 2020 F150 and compare that to the same year for the Super Duty. My payload and towing capacity is lower than that of let's say an F250 or even an F350 SRW or even a Dually

Glad it was helpful!

More to come!