Tecnical questions and answers
Why is grease lubrication better than oil lubrication for tiltrotators? This is a controversial qustion since the different tiltrotator manufacturers have choosen different alternatives. We therefore let the experts in triboloby (the field of knowledge that deals with the design, friction, wear, and lubrication of interacting surfaces in relative motion) answer the questions. Source STF AB.
“Is grease better than oil? In order to answer the question one need to start by understanding what grease can not do. Grease may be not used for cooling because of its poor thermal conductivity. It can neither be used as brake fluid or power transmission due elasticity, but as lubricants it is superior to oil”
Rototilt, Rotortilt or Tiltrotator, what is the difference?
Tiltrotator is the normally used generic name, but many of our customers say colloquially either rotortilt or rototilt when they mean the same thing. In reality meening a product with a rotating and a tilting movement used on an excavator. The rotation is accomplished with a worm gear which is the heart of the product that makes it possible to rotate endlessly. This combined with the tilt cylinders for tilting. There are products without tilt cylinders but it has the great disadvantage of a considerably weaker tilt motion and higher building height. Also, a tilt cylinder an extremely cost effective way to achieve very high tilting torque.
Why is casting better than welding?
The big advantage is that you can place material where needed for strength and it is possible to take away where it is not needed. This leads to a lower weight but provides an added strength. Then it depends on what meterial that is used in the casting process. Steelwrist is the only manufacturer that cast in high tensile steel while all other manufacturers cast using a type of ductile iron (Ductile Iron and Austempered Ductile Iron). The disadvantage with ductile iron is that it is more brittle and is very difficult to weld. The advantage however is that it is cheaper and easier to get a nice outer surface.
Why not not all manufacturers use castings?
The difficulty with casting is that there is a different way to design the product. The Steelwrist development engineers have extensive experience in casting technology and it takes a long time to learn how to. Another difficulty is that it takes a long time to start production, many months, and if something goes wrong then you must restart from point zero. Moreover the moulding forms are very expensive which makes it necessary to produce a large volume in order to make it competitive. Look at just any excavator and you will find that the component with really high need for tensile strenght normally are steel casted.
What kind of tilt cylinders do Steelwrist use?
We only use double acting tilt cylinders for maximum strength. The advantage with double acting cylinders is that when one cylinder press down while the other simultaneourly pulling up in order to obtain a uniform torque on the transmission. Since both cylinders are pushing and pulling, they become significantly stronger than single action that is often perceived as “spongy”. Additionally, we use hardened piston rods for maximum durability and ruggedness. A bonus effect we have with our design is that the cylinders are more “upright” than other brands thanks to the tilt cylinder ears sitting on the rotor body widest point.