Rotating Mass, Available Horsepower, and Acceleration

[TRDxB2]

This thread is to be about "How engine and drive train modifications effect vehicle, acceleration, top end speed and power(ability to climb steep grades". It was triggered by another discussion about water pumps.
As a base line lets assume a 1917 -1926 perfectly tuned engine that runs perfectly well on magneto or 6volt battery, perfectly adjusted coils and uses a timer; has standard running gear and ratios. Also when discussing things like the effect of removing magneto magnets and replacing with oil slingers please refrain from mentioning the effects on the electrical system. Added accessories like HP drain from adding a water pump should be mentioned as well. If possible the horsepower difference in using a generator vs alternator.
I found this on the INTERNET https://www.w8ji.com/rotating_mass_acceleration.htm that discussing the effects and could be a good start:
Several common questions about rotating mass are:
Use a lighter crankshaft, how much power is gained?
How does flywheel weight affect acceleration?
How much acceleration can be gained from using lighter wheels?
Does a lighter driveshaft speed up my car?
A rotating mass does not really consume or dissipate energy. A rotating mass stores energy. The rotating mass eventually either returns energy to the system in a useful way, or something converts the stored energy to some other form of unwanted energy. The conversion might be with a friction, converting to heat. The energy stored also might not do anything at all, or the stored energy can even be harmful, reducing acceleration or braking.
Accelerating an unnecessary rotating mass requires energy, and the acceleration process saps some of the horsepower we have available to accelerate our vehicles. Reducing available horsepower affects acceleration in a very predictable manner, and the horsepower amount needed to spin something up gives us some feel for how important a part change might be (Think water pump).

[Jeff Hood]

As you said, the heavy rotating mass stores energy. My touring with a high mileage but good running engine has no magnets. It is pretty easy to stall this engine when starting from a stop, especially when I have a full compliment of passengers. The low pedal needs to be somewhat feathered to get the car moving before fully pressing it down. On the other hand, my old truck with a very worn and tired engine with magnets never stalls even with some weight in the bed. Just stomp the pedal down and go!

[jab35]

Frank: That's a good article. If you knew values of the parameters for Model T flywheel, driveshaft and crankshaft, wheels, etc the calculator programs in the article would answer your questions.

I think the common sense summary at the end of the article is worth reading. There is an effect, and exchanging 'stock' rotating parts with parts having a smaller moment of angular inertia will allow the system to spin up faster, storing less energy in the process (and 'give back' less energy when decelerating). Quantifying the effect and the difference achieved with 'lighter' parts can be computed using the programs in the article. The examples in the article are based on heavier components and higher rotational speeds than the Model T, so when examining the magnitude of energy required, the analysis should include the % of instantaneous engine HP that is being utilized just to accelerate the rotation parts, along with time it takes.

Again an excellent post, thanks for sharing. jb

[Mark Gregush]

In the Model A world, loosing weight off the approx 63lb flywheel (36 vrs 63), you gain acceleration and top speed but lose at the bottom end, easier to stall. Must be a flat head V8 owner, because he talks about K member.
I think you could take the crankshaft and driveshaft off the list re reducing weight, as it has no application to a T.
When it comes to the flywheel, you would also have to plug in the oil that it is slinging around, which might be robbing power not to mention type of bearings and gears between the flywheel and wheel road contact, all will put drag on the engine HP output. So the question might be; what is the loss between engine HP at peak torque/RPM and road HP at same, of lets say a stock touring with driver to get a base line? In the attached report, remember you are talking about a dry clutch/flywheel along with the rear axle load being carried by the housing not the axle shafts.

[TRDxB2]

.... When it comes to the flywheel, you would also have to plug in the oil that it is slinging around, which might be robbing power not to mention type of bearings and gears between the flywheel and wheel road contact, all will put drag on the engine HP output. So the question might be; what is the loss between engine HP at peak torque/RPM and road HP at same, of lets say a stock touring with driver to get a base line? In the attached report, remember you are talking about a dry clutch/flywheel along with the rear axle load being carried by the housing not the axle shafts.

Very good points - wondering if the oil once in motion would have much of an effect, but lots of little t hings add up quickly. Has anyone Dyno'd a stock Model T engine or is 22HP accepted per the literature.

[Mark Gregush]

http://mtfctulsa.com/Tech/power_and_torque.htm

[TRDxB2]

http://mtfctulsa.com/Tech/power_and_torque.htm

VERY Informative ! Thank You
Note: It mentions a Bosch 600 Distributor equipped with an electronic ignition module and not stock points/condenser.
Here is a link explaining the conversion of antique distributors to electronic ignition
https://mtfctulsa.com/Tech/distributors.htm