A scissor gear perhaps? Or perhaps nothing,n smikle wrote:We know f1 cars use narrow face width gears on the front of the engine to drive the camshafts unlike road cars that use high inertia belts and chains. Since valve opening needs to be even more accurate at high rpms in these engines How is backlash controlled with These gears?
Toyota uses a scissor gear in the front of some camshafts.... The Toyota Starlet GT. I have pulled down that engine.autogyro wrote:Why does 'backlash' need to be controlled?
Belts and chains use 'tensioners' to maintain timing under load.
There is no need to do this with gear sets as the timing will only change under load due to tooth wear.
In some non F1 engines a dual floating idler gear is used to reduce 'backlash'.
I do not know what current F1 engines use.
In a well designed gear driven cam engine, the camshaft will not be allowed to overrun the crankshaft to over advance the cam timing.
n smikle wrote:Ok, we all know why F1 tolerances have to be tight.
BUT
Why are the clearances between moving parts so tiny?
Even as close as requiring the engine fluids to be warmed up before the engine can be started!
Through very accurate gear tooth hobbingn smikle wrote:We know f1 cars use narrow face width gears on the front of the engine to drive the camshafts unlike road cars that use high inertia belts and chains. Since valve opening needs to be even more accurate at high rpms in these engines How is backlash controlled with These gears?
would there really be any backlash to speak of in the valve train drive? assuming the crank has higher inertia thatautogyro wrote:'Gyro' (hmm) backlash does occur at very low rpm, i.e tick over on some gear drive output designs.
It is why Ken Wallis always uses a direct drive prop on the Wallis autogyro designs. (no problem with electric drive of course)
A high reving engine that needs a reduction gearbox to slow the prop always gives excess wear due to backlash vibration, it can be very bad and even lead to breakage.
Weslake designed a one off prototype engine for Ken that suffered from this problem as did the Norton Wankel prototype they gave him but to a lesser extent. The engine designed and built for Ken by Hewland was not as bad and had a damper fitted.
On light aircraft it is useful to use 'boxer' and long stroke engines to keep rpm to 4000 or lower with a direct drive.
It may be why there have been almost no real development in light aviation engines since the 1930s.
There are modern high reving engines in drones where the regulations dont seem to matter, no idea how reliable they are.
Cosworth do one as do Ilian.
This same problem can occur at very low rpm in gear driven cam engines including F1.
However, F1 engines dont usualy run at very low rpm.
It might also be a reason for 'blipping' the throttle at idle to keep the revs up and the gears driving.
backlash is often seen as the cause of the problem when it is just the symptom (removing backlash doesn't cure inadequate design)langwadt wrote:I can see why it might be problem for an engine driving a propeller where the propeller might have bigger inertiaautogyro wrote:'Gyro' (hmm) backlash does occur .......
It is why Ken Wallis always uses a direct drive prop on the Wallis autogyro designs. (no problem with electric drive of course)
A high reving engine that needs a reduction gearbox to slow the prop always gives excess wear due to backlash vibration, it can be very bad and even lead to breakage.
Weslake designed a one off prototype engine for Ken that suffered from this problem as did the Norton Wankel prototype they gave him but to a lesser extent. The engine designed and built for Ken by Hewland was not as bad and had a damper fitted.
On light aircraft it is useful to use 'boxer' and long stroke engines to keep rpm to 4000 or lower with a direct drive.
It may be why there have been almost no real development in light aviation engines since the 1930s.
However, F1 engines dont usualy run at very low rpm.
It might also be a reason for 'blipping' the throttle at idle to keep the revs up and the gears driving.
than the engine itself
Airscrew reduction gearing is a result of using over square high reving engines.reduction gearing is both pointless and worse than useless below 300 hp
(variable propellor pitch though is usual above 120 hp, and is very compact, very light and very reliable)