Colin Wrote :Just for the record I will say this is foolish and potentially catastrophic ---------------------------------------------------- This is a reply from Ron Slender VW Engines,
Phill, I would like Colin to have a look at the article on oils I sent you. Agreed that the refining processes are much more advanced from years gone by however that applies to all viscosities of oil including single viscosity. The reality is that single viscosity oils handle a higher heat range better than a multigrade. Additionally a multigrade was primarily developed so that an auto engine could start at a relatively cold condition and gradually reach operating temperature which in most vehicles is around 160/180 degrees. Multigrade oils have a lot of polymers and additives to give the oil the viscosity but do nothing to help lubrication, in fact they break down in high temp conditions. Single viscosity can handle the higher temps better. Additionally the oil tends to "cling " better for cold starts much like the sticky Shell oil used for aircraft because not all aircraft are used every day. Some oils can drain off providing high friction starts until oil pressure is there. I believe that you have to know a lot about the environment the aircraft is operating in and recommend the oil according to the application. Additionally Phil's engine is basically new and oils that have friction modifiers and high range of viscosity will effect the running in of that engine. After Phill has reached 50 hours then he make look at alternative oil options. However we have used straight 30 ; 40 ; & even 50 (very hot conditions) and the Shell oil for aircraft for air cooled engines. We do not use multigrade because of the fear that friction modifiers are often used in these types of oils which inhibit running in. Colin, your article on HP and how it effects speed was very good demonstrating that hotting up an engine can only increase overall speed marginally. Without going into elaborate equations the power difference was 35 HP and the actual Torque increase using 2500 rpm as a constant the extra Torque created by adding an extra 35 HP was only 63 ft lbs and that was at full power. Same goes for our gear drive engines. We have the Torque that say a 100 hp creates at 4200 , the reduction drive multiplies the Torque by the ratio on top of this. As long as a respectable size prop can be used to benefit from the extra Torque gain then the advantages of a reduction drive is clear. Because of the extra torque gain take off roll is reduced particularly when loaded, climb out is great and cruise is probably achieved at a lower throttle setting because of the prop diameter and available torque. A reduction drive will not necessarily provide a higher speed because this is a character of the aircrafts drag as Colin explains. The propeller has not even been discussed. Fixed pitch is a compromise, that we all except as being the norm because anything else is expensive. Why not fit a suitable in flight adjustable propeller then you will see some performance. Trouble is the cost of one of those, but ...I would rather spend money in that direction then spend lots of $`s trying to squeeze out a few extra HP out of an engine for very little gain. Not quite with you on oil Colin but I did like your thoughts on HP and drag. Ron Slender Phillip Matheson 0408665880 (cell) VHPKR Australia. [email protected] NEW WEB PAGE www.philskr2.50megs.com http://www.vw-engines.com/ OLD WEB PAGE http://mywebpage.netscape.com/flyingkrphil/VHPKR.html
