The extinction of 4-axle units?

[ajmiller]

QUOTE: Originally posted by Limitedclear

QUOTE: Originally posted by Junctionfan

The only decent 4 axle GE units are the P-42 which is designed for passenger service. GE sells nothing else from what I have seen on GE's website. I would imagine that the P-42 would be excellent roadrailer power.

Andrew -

As usual, you are WAY off base.

.....

You might want to try some reading again, before blundering into a new area...

LC

Is there really any point for ripping someone about a post made a year and a half ago?

[Sterling1]

QUOTE: Originally posted by Overmod

Mook sez

quote

Will they ever go to something bigger than the 6 axel? Or have they reached their limit in length and axels?

/quote

DD40s worked fine on UP, probably wouldn't cut it on most other railroads with that long rigid truck wheelbase.

Steerable trucks work best with a 'center' axle, which a D truck doesn't have; swingout on longer trucks (i.e. "E") would be mechanically uneconomic... we won't go into what would be needed for proper bolstering and weight transfer on such a thing.

Future of anything larger than C-C units would, of course, involve span bolstering of 'conventional' truck sizes -- B-B for four axles (as on the more successful version of double-engined GEs around the time of the DD35s and DD40s) and C-C as on the Norfolk and Western turbine 2300. Allows full interchangeability of parts, underframes, etc. with regular locomotives.

Why bother with anything else? Centipede underframes were demonstrated to be less effective than separate trucks a half-century ago. Interestingly enough, America hasn't embraced a B-B-B configuration under a single carbody (instead of C-C) even though units both here and abroad have been tried.

B-B-B config on a diesel would require the fuel tank placed within the carbody of the locomotive. On an electric unit maybe, it could work, but what are the benefits of that?

[mackb4]

NS's 7100 emd units was bought to run with raodrailers or intermodal trains that were light in tonnage.I can remember having about 12 of them all together on their first run over the Poca.divison here in 91 or 92 .They are geared for higher speeds(not for pulling heavy loads).They have a high horse 12 cyl.engine (I think 3000 hp.).They get around here occasionally on run thrus,and are sometimes used in Portsmouth Ohio on a local road switcher that requires a 4 axle.I don't know of any newer 4 axles being ordered by the NS.But because of business requirements,they will be around for sometime.

[daveklepper]

As for the statement that 6-axle diesels were intended for lighter weight on tracks, this was true of the RS-1's that were converted from B - B to A1A - A1A, keeping only four motors and having an idler axle betwen each two powered axles, for WWII service in Iraq, and then similar road-switchers available as a catalogue item from Alco. But generally, the C - C six motor six axel jobs are heavy enough to provide adhesion for tractive effort and thus are not any lighter on the track than 4 axle units of about the same period. Some of the early rigid truck C - C diesels were harder on track structure.

[samfp1943]

This is from the web site www;gmemd.com/en/home:
GP20D
Home > Locomotive > Switcher > GP20D

Performance Specifications
2,000 THP locomotive equipped with GM16V170B20-T2 engine
Tier-2 EPA emissions certified
Tractive and braking effort capability
65,000 lbs. continuous TE
97,000 lbs. starting TE
38,000 lbs. peak dynamic brake

Maximum speed 70 mph
Performance Impact
40% increase in adhesion over older model switchers
One GP20D is equivalent to a GP38-2
Cost Savings 10-15% improvement in fuel efficiency over 1st and 2nd generation switcher locomotive
Significant reduction in sand usage over 1st and 2nd generation switcher locomotive
Reduced servicing
2,550 gallon fuel tank
Simplified maintenance
Safety Aspects Cab design with 360° visibility
Heated front and rear windows
Low cab sound and vibration levels
Collision posts and anti-climbers that comply with the latest AAR/FRA regulations

Could not get the photo to print as shown on website. But about a year or so ago there was a southbound movement of about 10 of these engines (GP20D 'S) moving dead in a UP Train out of Parsons. They were painted blue with white trim and no lettering. Apparently the GP-20D is the only four axle offered by EMD now.

Sam

[CSSHEGEWISCH]

The GP15D and GP20D are actually engineered and built by MPI with some modifications to conform to EMD engineering requirements. EMD only markets these locomotives. The truckers in our midst might recognize this as an arrangement similar to that between Freightliner and White prior to about 1977.