How Many Pounds Are We Pulling

Same thing crosses my mind at work every day when I load cars and trucks on our flatbeds. On flat ground I have an advertised 7 degree approach angle, but often I have to load a vehicle that is on a steep uphill. One day I’ll thumb thru my old Collection of Geometry and Physics textbooks and figure it out, or do like my kids and search Google

if you're flat towing the vehicle the tongue weight on the hitch is negligible. the more important consideration is the total weight of the vehicle and whether that is too much weight for the the GCWR, the hitch or your towbar.

in general, the maximum amount of weight you can safely tow will be the lesser of the following:

- the GCWR (gross combination weight rating) of the MH minus the actual weight of the MH (defined as the sum of the actual weights on each axle) as it is loaded for travel (includes fuel, fresh water, food, clothing, people, pets, supplies, etc.)

- the weight rating of your tow bar

- the weight rating of your hitch

this is why it's vital to know what your MH weighs as it is loaded and configure for travel before choosing a toad. Your MH will not collapse if it is overloaded but you will experience handling issues as well as longer braking distances and accelerated wear on suspension, brakes, steering, etc.

It's not the rolling resistance you're concerned about with winching onto the trailer, it's the lift. Compared to the distance. Say for example your front axle weighs 3,000# and you roll it 3' forward to lift it 1'. 1/3 = 1,000# line load on the winch.

In a real application you'll have little jumps in lift like the first bump up onto the ramp that will exceed the average.

PS not good to load a winch near capacity.

The amount of pull to drag a 4500 lb car down the road behind a motorhome on level ground at 60 mph is minimal.... Likely under 200 lbs. Going up a 6% grade would require adding to that number roughly 6% of 4500 or another 270 lbs. If you wanted to pull a 4500 lb car up a 45 degree incline it would require 4500/1.414 or about 3200 lbs of pull.

Delta V plus rolling resistance plus or minus allowance for slope.

If you are sizing a winch remember a winch only pulls the rated capacity when all the cable is off the drum except the last layer. As the winch drum fills with cable it acts like a gear and the drum gets bigger making the pulling power less as the drum grows in diameter and it is a dramatic difference. You could remove most of the cable to correct for this. I have done testing on a 10,000 pound winch that held about 4 or 5 layers of cable on the drum when all of the cable was on the drum and it was full the pulling capacity was just over 5,000 pounds. When the cable was payed out to the last layer on the drum leaving 3 wraps we got the 10,000#.

Why winch the car on??? Drive it on. A 1000 lb winch will pull it up most trailer ramps.

When talking about "hitch capacity" do not forget what happens during heavy braking. Now you have the momentum of the toad/trailer pushing against the hitch as well as the stress on the brakes of the towing vehicle.

Ivylog:
Sometimes things just don't run and they have to be taken to somewhere else for me to work on the problems. Such in the case with the '67 Corvette and the '53 Ford Tractor. Summer northern AZ and winter in Phoenix.

I have had one of those $49 boat winches on my open trailer for more than 20 years and with a home made "snatch block" I have pulled a full sized pickup on there that had no wheels on it.....a regular car of any size is a snap.