Why 4 axle RDMTs and not 6 axles?

When the RDMTs were made, why did CSXT use 4 axle GP30s and GP35s? Why not use SD35s, SD35Ms, or SD40s? Could CSXT have gutted a U Boat ballast it and make it a G.E version of the RDMT?

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Terry C:

Let's start with the basics:

1. CSX wanted extra tractive effort for use on local freight train operations. The objective was to have increased tractive effort on train start-ups and stoppings. Most of these freights operated on secondary lines, and often had to access sidings with light rail which, in most cases, were not in the best of shape. 6-axle power is not the best machines to use in places where such things as light rail, minimal line maintenance, and sidings with wobbly rail are often encountered. 6-axle power can do real damage to the rail alignment on the secondary lines, not to mention a few derailments! Thus, 4-axle power was an obvious choice. And, overall unit weight was also an important factor.

2. CSX had plans to build a lot of Road Slugs for use all over the CSX system. They ended up building somewhere around 150 RoadSlug units. Thus, a lot of retired or about to be retired units were needed for the Road Slug project. Timing was such that a lot of GP30 and GP35 units were being retired in the same time period--4 axles, relatively lightweight units, lots of them--PERFECT!

3. CSX didn't have a lot of SD35 or SD35m units, --and they were 6-axle units, --and they were important "niche" use units, having found important uses in heavy yard switching and in the coalfields. So, why remove them from what they were doing best, and tear their guts out? Nope, wasn't gonna happen!

4. SD40 units? No way! Again, besides being 6-axle units (see above), the SD40 units were considered by CSX to be much more valuable than to have their guts ripped out and make them into traction motor jobs. Remember, CSX added dash-2 technology and major overhauls to most of their SD40 units, making them SD40-2 units and giving them around 10 - 15 more years of life. Not only that, but CSX acquired other SD40 units and had them upgraded to SD40-2 specs. Most of these upgraded SD40 units are happily hauling freight and earning $$$ for CSX today! And, probably will continue to do so for some more years! CSX currently has over a hundred upgraded SD40 units roaring along the rails today--with their prime movers still intact and functioning!

5. GE units? Again, weight was a concern, even if it was on 4 axles. (SBD/CSX wasn't peachy keen on the U18B units, and wanted them off the property!) And, most of the GE units were still in funtional use when the Road Slug program was initiated. Again, the logic of why tear up a funtional unit prevailed in terms of CSX decision-making. TRIVIA POINT: Did you know that CSX still has a currently operable U36B unit? Yep, it started out as SCL # 1776; re# to 1813 so that # 1813 could be painted in the Bicent. colors and re# 1776; then SBD/CSX #5764; and is currently Waycross Locomotive Operations (WLO) #1! And, in a fresh YN 3 paint job! If you ever get down to Waycross, GA, take a lot at her! She's still very much a beautiful-looking lady!

ACLfan

i just have a question, what does RDMT stand for?

Good question!

In my response to Terry C., I assumed that he meant "Road Mate" when he used the initialed reference "RDMT", since that is CSX's terminology.

Based on the details he mentioned in his question, I realized that he was referring to Road Slugs, which is what CSX called the road slug units that were produced from former GP30 and GP35 units (and several other types) before finally changing the name to Road Mate a few years ago.

Heard that some CSX "head-shed types" got a little miffed about the unsavory connotations associated with the word "slug". Consequently, the message was received, and the name "Slug" was changed to the more high-fallutin' "Mate". Just a little touch of "class" there!

The term Road Mate (RDMT) originally referred to the factory-built cabless slug units that came with a U36B order for SCL back in the 1970's. Those Road Mate units are long gone! I don't believe that any examples were preserved for posterity.

In the latest go-around of remote controlled "drone" units, both 4 and 6 axle units are used, since they are primarily intended to be used in yard service and on drag freights.

ACLfan

It seems to me that six-axle slugs would create an unfavourable hp per axle ratio for road use.

THANK YOU EVERYBODY. CSX now has more locomotives with out any prime movers.
http://www.rrpicturearchives.net/locoList.aspx?mid=347
http://www.rrpicturearchives.net/locoList.aspx?mid=680
http://www.rrpicturearchives.net/locoList.aspx?mid=346
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So they don't like the connotation of "slug", but roadmate is ok? Roadmate sounds like one of those truckstop hookers (lot lizards). Gotta love some brass with too much time on their hands.

there are 3 reasons why they didnt use 6 axle units

1. they didnt have any 6 axle units they wanted to get rid of at the time

2. 6 axle units are not good on industrial lines and private sidings because of the sometimes tight radius curves and turnouts, not to mention they are usually heavier than 4 axle units. They would have derailed more on sub-par industrial sidings and team tracks.

3. For the most part, they were paired up with GP40's. That gives you 3000 HP to use between basically 2 4 axle locomotives (or 8 traction motors). Or 375 HP per axle, assuming proper loading and ideal conditions. If you used a 6 axle unit, you would have 3000 HP to use with 10 traction motors or 300 HP /axle. It would give you more tractive effort, but you would never get the train moving fast enough to get to the point where the slug cuts out (30MPH I believe).

there are some 6 axle slugs used in yards which were inherited from conrail, but they are just used for pushing cuts of cars over the hump at yards. That is a good use for them, but that is about it.

About the only thing they had at the time they could have used were some SD35's anyway. Everything else had been retired or sold off (like the C&O SD18's). And it would have been a waste to use an SD40 for this. Most of the SD40's got rebuilt into SD40-2's anyway around this time.

Good points Nip, just one item, the roadmates continue to operate at road speeds. They are basiclly a 3000 hp 8xl engine, created to work mostly locals were sharp curves prohibited 6 xl use but needed tractive effort, and remained gear for road speeds. The roadmates don't cutout at speed. We have utilized them many times on local service which often runs between points at timetable speeds of up to 50 mhp along the Albany Div.. The Slugs that Conrail used in hump service with the SD 38's they were mated with were specifically geared lower for more tractive effort for this duty.

roadster wrote:The Slugs that Conrail used in hump service with the SD 38's they were mated with were specifically geared lower for more tractive effort for this duty.

Is this true? I didn't recall top-end limits on these units that would indicate lower gearing.

Re; speed restrictions on Conrail slugs left me scratching tho old noggin so I had to dig up one of my old Conrail employee timetables. According to Conrail Eastern Region Timetable No. 2 in effect 12:01 A.M., Sunday October 25,1981 Unit numbers 1000-1023 class MT-4 and Unit numbers 1100-1128 class MT-6 in multiple unit consist.... speed lite 60 MPH and With Train 65 MPH. Note 5 refers to these units as " Motor Trailer Units ( Slug Units )." BTW the 4 and 6 following the MT stood for number of axles. Any of you CSX employees on the forum know the speed limit on your units ?