machin wrote:The way I do the inertia is to equate the inertia of the engine and transmission to an equivalent inertia at the road wheels...by taking into account the relative rotational speed of there components compared to the road wheels... U need to work out the inertia separately for each gear therefore since the relative speeds are different... My program does that all for u, and I've created my own system for estimating the inertias of there parts based on a load of different factors and a survey of many real parts (I'm by geek, what can I say!)... Or I can individually add in actual values if they're known...
Convinced I know what I'm talking about now?!
Ok, just checking to see if you really know what you are doing. But the best direction to go initially is to find the net force on the car first, subtract the drag and rolling resistance from the wheel force at that speed (assuming C.O.P is at wheel centre height), to get the net torque on the wheels. It wont change the relations, just the acceleration.
I am doing it now. Now remember as i said, there is something that is not being accounted for, i think it could be the initial slip. I have already taken note of the single gear ratio with constant power, and yes i can see where you said 1 gear works
The only issue is the first movement from idle.
This is based on an idle speed.
However both multi and single gear solutions are the same if both start at an engine speed of zero
. Otherwise the multi gear has an advantage.
The reason, both are equal from zero, is that coming from an infinite torque nothing can really prevent one from not moving. Only in the case of starting from a cut off point with an initial resistance, will there be a need for a threshold force to start motion.
In the case of an arbitrary engine idle speed, the lower gear could mean the difference between moving off and stalling. Maybe on a slope i suppose. Rolling resit, isn't so great to make that difference.
And as i mentioned the slip already, the higher gear has a bigger wheel speed and and road speed differential as the clutch is let in compared to the lower gear, given an idle speed.
The wheel will slip for an amount of time; this artificially gives the multiple geared car a head start.
In my data my first gear gives 7m/s at 1000 rpm, my 7th gives 38m/s.
Going off throttle would aleviate this as you say, but off throttle defeats the purpose of constant power.
This is also why i realize constant power doesn't make sense.