4-11-21 more on the impact of trucks & wheel material and N scale freight cars

the work on the test track continued. The PVC plank was successfully secured with chalk. Opening the way to begin the N scale test work. The truck and wheel set activity is the beginning. Engine tests will follow in short order.

Focusing on the rolling characteristics tests, the plan is as follows:

1. using three nearly common freight cars, that are near to the average car.
2. examine at least three truck types, Arnold, Atlas & MTL.
3. examine at least four wheel types, generic(Arnold?) plastic, generic metal(Atlas?), MTL plastic & ESM metal.
   
4. the study may be expanded to vover additional truck types and wheel sets depending on availability & availability.

The process for this user is to assemble one of the freight cars with a set of the trucks & wheel sets. This car will be placed in a run of N scale track. For this testing Atlas code 80 flex track will be used. The grade of the track will be set at 2.5%. The car will be released at the high end and will roll accelerate down the grade. Near the lower end of the track the car velocity will be measured. The height difference between the release point and the measurement point will be measured. From this testing the rolling friction drag will be determined for each variation.

this rolling friction drag is derived below:

To calculate the drag due to the friction

We can use the energy relationship:

The potential energy + the kinetic energy  + rolling friction loss = constant any where along the track

There are also some effects of vehicle drags. However because the comparisons are being done with the same car, those can be ignored.

So the the following equation results:

Potential energy at the starting point(PEo) = the kinetic energy at the measurement(KEm) point + the rolling friction loss(rfm)

So:

PEo = KEm + rfm

And

rfm = PEo – KEm

Further  

rfm2/rfm1 = (PEo – KEm)2/(PEo-KEm)1

PEo = Wt x ho

where: Wt is weight & ho is height difference

KEm = 1/2 Wt/g (Vm)^2

where: g is gravitational acceleration, 32.174 ft/sec/sec, Vm is the velocity at the measuring plane, in ft/sec.

Thus:

Ratio of rfm= ( Wt ho – 1/2 Wt/g Vm^2)2 /

(Wt ho – 1/2 Wt/g Vm^2)1

Simplifying:

Ratio = Wt2/Wt1 (ho – 1/2 Vm^2)2/(ho – 1/2Vm^2)1

Thus the rolling friction can be determined through this equation. These measurements need to be in the same reference. These calculations will be in the full scale.

Should start this testing soon.