I am wondering if modern diesel locomotives are artificially made heavier than they are as built to have better traction and pull more cars without wheel slippage?
The average locomotive weigh is 415,000 pounds.
Rodney
intersesting topic ge’s website explains some of the weight issues balancing weight, tractive effort fuel economy, track structure, wheel wear all play into there decisions, but I believe the number one reason for weight limitations is that at some point there just tooo large
Yes. Example CNW first order of there C40-8 weight 401,000 their second order weight 420,000 the deference was more concrete was added to make it heavier.
Average locomotive weight is 415,000 pounds? I think not. Not even in North America, where the typical 4-axle locomotive is in the 240,000 lb range, and many six-axles are in the 360,000 lb. range. In Europe and Asia few locomotives exceed 250,000 lbs.
The original question asked if locomotives are built heavier than necessary to improve adhesion. Yes and no. Yes, from the perspective that for purely structural reasons you could accompli***he necessary robustness with a 240-300,000 lb. locomotive. No, because the customer wants to hang the biggest fuel tank possible beneath the locomotive, and that drives weight right up to the maximum possible loadings the track structure and bridges can accommodate without excessive wear.
Here’s a link on CNW roster. that gives there weight.
http://utahrails.net/cnw/cnw10.php#8501-c40-8
Same school of thought when you throw a few hundred pounds of sandbags in the back of your pickup during winter. More weight=more traction.
It depends on the number of axles. Given a maximum axle load of 35 tons then a 2 axle loco can weigh no more than 140,000 lbs, 4 axles no more than 280,000 lbs and a 6 axle unit no more than 420,000 lbs.
There is pressure though to raise the axle load to more than 39 tons which increases the maximum weights to 157,500 lbs, 315,000 lbs and 472,500, which will not make mud a happy chicken.
Locomotives are sometimes ballasted with concrete (or even steel as it’s denser), but not always, it depends on the state of the infrastructure and the type of service the unit will operate.
On CSX, typical 4 axle power weighs between 280,000 - 300,000 lbs, and newer 6 axle power 432,000 lbs.
Hate to bust you guys bubble…right off the builders sticker on a BNSF Dash 9 we used today…weight loaded 415,000 lbs.
Our MK1500Ds weight 256,000 lbs…thats a four axel or BB switcher.
And after 10 years working with them, I have yet to find any concrete, extra steel, or sandbags hidden on them…
Ed
I remember when CSX forst got its AC6000s, the idea was to couple them to a fuel tender, which would keep their fuel tanks filled–the weight difference between the full and empty tanks would be enough to throw off the tractive-effort rating.
C&O used to have some SD40s that were up over 400,000 pounds. I wouldn’t be surprised if just about everything built today exceeded that weight, since locomotives are longer and larger nowadays (couple an SD40-2 to just about anything newer, and it looks like an old Geep!).
Can’t cite specifics, but I’ve seen numerous references over the years to specially ballasted locomotives. As mentioned, it’s usually done for a specific reason, like a grade, or perhaps hump engines. You won’t see them out roaming the system.
I’ve been on many GP9’s & GP7’s that had a big round piece of concrete in the short hood. Some locos had the end plate made of thicker steel than was necessary to add extra weight.
If by “end plate” you mean the pilot plate…on GPs and the rest of the road switcher designs, 1" thick and up is the norm…on anything used in yard switching where by-passed couplers happen on a regular basis you better have a thick pilot plate…and I would suspect the railroad who’s locomotive where the round concrete plug was in the short hood used that to replace the old steam boiler for passenger car heating, and they were trying to keep the weight displacement on the locomotive pretty close to what it was when they had the boiler in there.
I have been on SD40s, SD40-2, GP30s, GP9, GP7, MK1500D, MK2000Ac, GE Dash 9s, GE Dash 8s, B30-7As(cabless B30s) and the new GEVO units, MK5000, GP38-2, SW7, SW9, UP’s SW10, Amtrak Genesis units, the UP’s E9s, (pretty neat rebuild inside), the UP3985 Challenger, an BN SD9, and SP SD9, along with an assortment of F units, and several of the Santa Fe Cleburne CF 7 rebuilds, which were the only units where the addition of steel was obvious, due to the structural modification when the car body was removed and more support was needed.
None of them had sandbags, extra steel, or concrete added.
On the other hand, almost every yard slug I have seen has had concrete added where the diesel engine was removed, to keep the weight for tractive effort, or the fuel tank filled with sand if it was just a slug unit.
UP has three slugs working Englewood with the fuel tanks filled with sand.
They also have a pair of road slugs, with the diesel units intact, looks like they were built on older GE frames…those have ballast weights in the form of huge sand boxes added to replace the missing weight when the hoods and cabs were removed.
With two decades plus of wheel slip technology already in use, the need to “add weight” is long gone…Most of the GE Dash series have excellent tractive force balancing systems, even our simple MK1500Ds can slack off or juice up individual traction motors to prevent wheel slip.
Ed
CNW bought 30 C40-8 weighting 401,000 Lbs in 1989. 12 more in 1990 & 32 units in 1991 the last two orders weighting 420,000 Lbs. they must used something to make it weigh 19000 more.
BRC’s first GP38-2’s (490-495) were ballasted up to 280,000 lbs. since they were intended as hump pushers. All of BRC’s 4-motor power was ballasted and as a rule was heavier than the norm.
Ballasting ins’t always obvious since it often involves a heavier than normal frame with thicker deck plates and other parts.
There is a nice balance between locomotive weight, tractive effort, prime mover power, traction motor gearing, short term current ratings and sundry other items. The short of it is that, in general, the manufacturer will get it pretty close to right, so that at maximum short term current and lowest speed and prime mover wide open on dry rail and sand the thing will just barely slip, if at all. Any heavier, and you’re wasting fuel carrying the weight around. Any much lighter and you don’t have the tractive effort you want. You do want to be well balanced – I’d agree about the round plug of concrete in the old GPs. You can see the principle in older six axle passenger units (A1A trucks) where you had less power and didn’t need to motor all six axles. They were built for speed, not hauling (that’s the gearing part of the equation up there!) and were heavier than they needed to be for traction.
It would not be that hard to build a lighter locomotive with a given power rating, but slipping wheels can ruin your whole day…
Paul and Jamie…
Both are true…but read the original post…in essence do railroads “sandbag” their locomotives to increase tractive effort…as a rule of thumb, no they don’t.
For a special purpose, as in the hump yard power, or the CF 7 rebuild program, yes, and you can order locomotives built heavier from the builders for specific use, as in unit train power for coal hauls and such.
Our MK1500Ds were ordered heavy, because we use them as flat yard switchers, we also ordered clasp brakes and big brake pistons to stop it all with…yet the CEFX fleet of GP15 and 20s (MK1500 and MK2000Ds)that UP leases are lighter, because they intended them to be road/switcher power.
As was pointed out, beefier frame parts, extra thick deck plate and pilot plates can increase the weight dramatically, but unless you have a good back shop, the only way to get that is to order it built that way.
For the most part, the carriers themselves do not do such modification on the motive power, except when they home build stuff…such as yard slugs, the Santa Fe’sCF7, or the UP SW10 rebuild program.
But to answer the original question, railroads themselves do not modify weight wise entire classes of locomotives.
Ed
Thanks everyone for their insight! This pretty much answers my question. I was mainly interested if locomotives as built are maybe already heavy enough by design or if weight is taken into account when designing it to make sure it is not built too light.
Thanks again folks!
No matter how good the wheel slip technology a locomotive cannot produce tractive effort without sufficient weight. The new systems are pushing this to the limit and frequently fail to produce anywhere near their rated output when rail conditions are less than ideal. All that these systems do is decrease the output down to a level that will prevent the wheels from spinning wildly. The lower the weight of the locomotive the lower this output will be. If you are depending on the full output to climb a grade you are stuck.