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988G-988B compare for superior loader design!
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One other thing about variable dispacement hyd systems I have read is that Deere uses 3 pumps on the 844J like an excavator has for years. One feeds steering and brakes at all times. The other 2 split between boom and bucket depending on which one requires the most flow, thus giving them an advantage on break out power. I believe you will see all larger loaders go to that style system in the future. Cat used vane pump on 980G and switched to gear pump on 980H. I hear them called lead sleds and fuel sucking monsters most of the time. Eugene
John C.
Senior Member
Wheel loader hydraulic systems can be set up any way you can think of and all the manufacture's do it different and claim their is best. The problem with their claims is that it always takes a certain amount of horsepower to move a specified amount of oil at a specified amount of pressure. In short there is always a minimum amount of horsepower needed with the corresponding fuel use.
An example is that it might take one horsepower to move one gallon of hydraulic oil per minute at 1,000 PSI. If you are using fixed displacement pumps, your back pressure is usually at least a couple of hundred PSI and you are always putting out 50 to 100 gallons per minute. This is wasted fuel going up in smoke. Return lines to tank are big to reduce line pressure going back to the tank. Hydraulic return filters are large and usually in mulitple elements to take as much of the oil with as little restriction as possible. The basic stratagy over the years was that a wheel loader is always supposed to be in motion moving material and if it wasn't it was supposed to be shutdown.
Usually brakes are put on their own system. Steering is usually put in combination with other systems such as brakes or implements. Usually there is also a pilot pump involved. I haven't seen any wheel loader hydraulic systems that separate the bucket tilt function and boom up function. They are normally on the same pump and control valve. There could be something new out now that I haven't seen yet. Ride control is usually on the implement system also.
As I said earlier when you go to variable displacement pumps you save fuel by not moving oil unless it is needed. The problem with variable displacement pumps in loaders is that they are very expensive. I have thought that the piston units would be too expensive for small to midsize loaders but should become cost effective in seven yard machines and larger.
At any rate the real fuel issue I believe is in the engine. If the engine isn't efficient at producing horsepower, you have wasted fuel going out the stack and usually blow by gasses coming out the breather tube. Again the only way to measure efficiency in wheel loaders is by the amount of dirt moved per gallon of fuel.
An example is that it might take one horsepower to move one gallon of hydraulic oil per minute at 1,000 PSI. If you are using fixed displacement pumps, your back pressure is usually at least a couple of hundred PSI and you are always putting out 50 to 100 gallons per minute. This is wasted fuel going up in smoke. Return lines to tank are big to reduce line pressure going back to the tank. Hydraulic return filters are large and usually in mulitple elements to take as much of the oil with as little restriction as possible. The basic stratagy over the years was that a wheel loader is always supposed to be in motion moving material and if it wasn't it was supposed to be shutdown.
Usually brakes are put on their own system. Steering is usually put in combination with other systems such as brakes or implements. Usually there is also a pilot pump involved. I haven't seen any wheel loader hydraulic systems that separate the bucket tilt function and boom up function. They are normally on the same pump and control valve. There could be something new out now that I haven't seen yet. Ride control is usually on the implement system also.
As I said earlier when you go to variable displacement pumps you save fuel by not moving oil unless it is needed. The problem with variable displacement pumps in loaders is that they are very expensive. I have thought that the piston units would be too expensive for small to midsize loaders but should become cost effective in seven yard machines and larger.
At any rate the real fuel issue I believe is in the engine. If the engine isn't efficient at producing horsepower, you have wasted fuel going out the stack and usually blow by gasses coming out the breather tube. Again the only way to measure efficiency in wheel loaders is by the amount of dirt moved per gallon of fuel.
Operator / Fuel
I think alot of fuel usage is in the operator's hands...We have guys that take longer and cover more ground to load a truck and we have a few that run a tight V pattern...The guys that run the tight V always load the same amount faster and alot more efficient,the engine isnt full throttle as long...I run our 992G production loader,they figure my fuel usage by Loads crushed weekly...That gives them cost per Ton and also Per Ledge...The funny thing is,its never the same Per same Ledge...
Kind of funny what John said about Hyd system's,I ran our 988F for a while with the engine on its last leg,it wouldnt hardly lift a full bucket...They ordered a new one and they also put in a new pump...It was like getting a new machine...My fuel usage dropped at least 30%...
I think alot of fuel usage is in the operator's hands...We have guys that take longer and cover more ground to load a truck and we have a few that run a tight V pattern...The guys that run the tight V always load the same amount faster and alot more efficient,the engine isnt full throttle as long...I run our 992G production loader,they figure my fuel usage by Loads crushed weekly...That gives them cost per Ton and also Per Ledge...The funny thing is,its never the same Per same Ledge...
Kind of funny what John said about Hyd system's,I ran our 988F for a while with the engine on its last leg,it wouldnt hardly lift a full bucket...They ordered a new one and they also put in a new pump...It was like getting a new machine...My fuel usage dropped at least 30%...
992G
Well-Known Member
There is a 3.6m boom that is offered in a bulk loading arrangment. Also they offer a 10 yard bucket to go with it. Beware, for some reason this set up does not have the break out force as the other boom options. If the operator has never ran a H model, and gets on this bulk loading machine, there will be no problems. If another one comes in with the different set up, a big difference in performance will be noticed. Also, when running these machines, make sure to use the throttle lock. It does help.
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