Are large gas motor Rv's underpower?

DanTheRVMan wrote:

Mr.Mark wrote:

d1725829 wrote:
My opinion, does it really matter how fast you get there as long as you get there ? I go for the thrill, I am in no hurry !

What my concern has been is that when we get stuck behind a very slow moving semi and we fall to their speed of 35 mph going up a steep hill, will I have enough 'umpth' to pass him without causing a major slow-down in the passing lane.

I'm not wanting to race anybody, I just want the ability to pass within reason instead of being stuck behind a very slow truck.

MM.

You should read http://prevostcommunity.com/PDF/Motor%20Home%20Fuel%20economy.pdf

max speed up hill is determined by weight/hp

torque is not a factor for steady state velocity up hill

GETTING to max velocity is determined by how fast you accelerate

For the same mass the more Torque the faster you will accelerate (F=MA)

So torque will get you to accelerate faster around a slow moving truck.

But the max velocity up hill is still only governed only by weight/hp as you are not accelerating so torque is not an issue.

How fast you accelerate to that max velocity up hill is a function of torque and weight.

I am sure you will love your new toy.

How exactly does torque figure into the F=MA formula?

Torque is neither mass nor acceleration by itself.

To convert Torque to force, you have to divide by the length of the arm (or factor in the gear ratios).

Just to keep the math simple, lets assume:
- Diesel with 600ft-lbs torque at 1500rpm
- Gas Engine with 300-ft-lbs torque at 3000rpm.
- The gas engine is run at half (or is it twice) the gear ratio of the diesel, so the steady state speed is the same.
- Assume the engine torque for the diesel directly translates to the torque at the wheel and the wheel has a radius of 1 ft (no it's not realistic gearing but keeps the math simple)

The diesel has 600ft-lbs of torque at the wheel and when you accound for the length of the moment arm (1ft), it provides 600lbs of force pushing the rig forward.

The gas engine is only putting out 300ft-lbs of torque but the gearing doubles that at the wheels, resulting in 600ft-lbs at the wheel, which provides exactly the same 600lbs of force pushing the rig forward.

So for a given HP output (torque X rpm), F=MA turns out to be the same for both engines.