ive noticed that as much as scrapers have gone foeward! im curious about them having two power sources ,and still needing some push!im sure it was never cheap to have some d-6s, or d-8s around to make things happin!were these machines ever built with enough power to do there job! many of them had the "pull-me-push -me arrangement! and that still was not enough!
Its not a mater of horse power, as it is a matter of tractive power. Tires just simply do not put the power to the ground. I have run many Terex Ts14s, and many Cat 627s. All of them had enough power to move the load, and they also had enough power to self load, but it takes a long time to get that full load. By adding a push cat, it cuts your load time in half. Not only do you load faster, but you load more. Not only cubic yards, but as you get pushed, it packs material into the bowl. Weigh a load that was self loaded, vs a load that was push loaded, this assumes that both are full completely to the top. The load that was push loaded will weigh more.
Dirt doesn't just jump up into the bowl by itself.
Tires aren't cheap, and like turbo said, you wont' get teh traction with tires that you do with tracks. So the added push from dozers is sometimes prefered, specially in shales where the rock is sharp, then you really don't wanna spin tires in that.
I'm not a scraper person, but even I can't escape the obvious. The thing counter is failing to consider is; by design, the scraper isn't necessarily designed to "dig dirt" as much as it is designed to "move dirt" from point A to point B. Although they are more than capable of loading themselves in ideal conditions, they aren't designed with loading themselves in specific. Their primary role is to haul material in a rapid manner, spread (not dump) the material quickly, then rapidly return to reload. The push dozer concept is by design as well, as has been previously mentioned. The scraper is all about speed in moving material. Why make it labor to load itself, eating time, when a push dozer can be utilized to shove that bowl full and get it down the road. After all, it's all about "moving" material.
you need dry ground to make a scraper efficient.Any scraper no exceptions.My wabco C-pull takes about 200 feet to get a full load.But it has to be dry to get traction.
thanks for clearing me up!
It's all about loads per hour in big production jobs. It used to be that it took a minimum of ten loads per hour for a 651B to just break even cost wise. If that same machine could get more than that, it was considered gravy. Having a D10, D11, or a pair of 9's hung onto the stinger would make the loading process much faster, the only place really where a cycle could make the most gain in time. Better and smoother haul roads, shortest distance to fill, load in direction of fill only are some other ideas that helped. Other factors to consider are the tires. We always wanted to never spin a tire as you could practically count the dollar bills coming off in terms of rubber lost whenever a tire lost traction. A TS24 can self-load in topsoil or plain dirt in about 15-20 seconds. Putting a tired D9G behind it could decrease the load time to 8-10 seconds, and it would be a larger load. A TS14 could self-load in about the same time, but putting a 9 behind it meant it could load in 5-6 seconds, barely enough time to drop the can in the dirt and immediately pick it up again. 627's, because of the angle to their moldboard, have never loaded as easily as a TS14, same with TS24's vs. 637's. The Cats are faster on the haul road, a little, but can not dump as fast as the Euc's. In granular material like loose sand or gravel, a push cat is a requirement if you want production. Even then, some materials can be very tough to load, like volcanic mixed material on the western slope in Colorado. Hard pan or clay are two other toughie's to load. You also have to remember that as soon as the pan hits the ground, the tires immediately lose some traction because the weight is off them. As the load builds up in the bowl, the traction available becomes even less on the front, though it does increase a bit on the rear. If you try to pump a load into the bowl, all you have going for you is inertia, not traction. There just is no substitute for a push cat with a good operator.
Wanna put money on that? You're forgetting a unique class of scraper, the auger and the elevating scraper =) Augers definately are the tool for muddy conditions.
Elevating and auger scrapers are no better in slick or muddy conditions than any other self-propelled model. The tires have to have traction and in wet clay or other low traction materials, it just isn't going to happen. These types of scrapers are marginally better at loading the bowl, but are a lot more expensive to operate and much slower in the cut and the fill. They do not do well in hard materials. Under wet or slippery or other poor traction conditions, there simply is no suitable substitute for a couple of pushcats banging on the stinger.
thanks for the replies!!! ive also noticed in the pics,that the people who own and bid on jobs ,for the most part,will run scrapers, wheel loaders,and graders, on nearly bald tires!im sure these huge tires are mega-buck! and hard to come by! at the same rate ,there using up big buck undercariage on the track machines as a band-aid!im only guessing here!
Elevator type scraper- ideal application The place that elevators out shine open bowlers, is on hard ground (clay) in land levelling, cut & fill. A single machine & one operator. They are a versatile & quite often, a very underated & under utillised piece of equipment in the earthmoving industry, being able to self load, carry, spread/dump, grade & compact. Housing subdivision developers are returning to using elevating scrapers over excavators & moxy (6WD artic' trucks) as conditions dry out. Simply put, in the hands of a competent operator, they are one of the best production tools around. :cool2 As someone else put it on this forum, " The funnest way to shift dirt " :notworthy