Towing our Escape 21 - real world stats

[Posttoasties]

We took a four-day trip to Itasca State Park (where the headwaters of the Mississippi River is located) last week. On our previous trip we started with 2/3 tank of fresh water and ended up having to carry water on the last morning so for this trip I filled the fresh tank full. It’s only a 100 mile trip and Clara would rather use our own water so I figured what the heck, we’ll tote it. We took our bikes – our two bikes and bike rack weigh just over 100 pounds but we also took our daughter’s bike. (We were babysitting our granddaughter and our daughter was going to meet us so we added her bike with attached infant seat – I’m guessing another 30 pounds.) So with three of us in the vehicle (it’s amazing what a kid, car seat, and some toys weighs) I wanted to be sure we weren’t overloaded.
There’s a truck stop about a mile from our house and I had previously talked to them about weighing our vehicle and trailer. The ladies at the fuel desk were very helpful and told me exactly what I needed to do. So we drove over and got the Durango and Escape on the scale. The scale has three pads so I parked with the Durango front wheels on the front pad, the Durango rear wheels on the middle pad and the Escape wheels on the back pad. I called the fuel desk told the lady who answered who I was and she told me she had the weight and I should come and get the ticket. We parked and I went in, paid my $11 and told her I wanted to do a re-weigh to get just the trailer. (They had told me to do this and since it was a re-weigh it would only cost an additional $2.)

I drove back onto the scale and had just gotten out to unhitch when I noticed a semi had pulled up behind us. Not wanting to hold him up I jumped back into the car and drove off the scale, let him on (it takes those guys about 15 seconds to drive on, get weighed and drive off) and then drove back on. I lined up so the tongue jack would be on the middle pad and the trailer wheels were on the back pad. We unhitched the trailer and drove the Durango off the scale and I called the fuel desk. When I told the lady who I was she chuckled and said, “We’ve already got you weighed – come on in and get your ticket.” (I found out later they have a camera on the scale so I guess they were having a good chuckle watching us making sure everything was lined up correctly.) So we hitched back up, parked and I headed in and paid my $2 and got a second weigh ticket.

Now, I feel better – it was worth the $13 for my peace of mind. All the weights are within the limits of the Durango and the Escape. I did notice a discrepancy – on the first weigh the trailer axle weighed 4,100 pounds (attached to the Durango with a WD hitch – in case that makes a difference). On the second weigh the trailer axle weighs 3,940 (not attached to anything). What happened to the other 160 pounds?

[jxoco]

The weight distribution hitch put 160 lbs of the tow vehicle onto the trailer.

The third measure would have been just the Durango to see how it changed.
It should have been 160 lbs lighter.

[cpaharley2008]

My 21 was close to your numbers, but I did not have 3 bikes on rear. 3800# axles and 500# tongue weight/4300# total

[Bill and Earline]

Paul,
Here's my non-engineer comprehension of the effect of a WDH:
Before the WDH is put in place, you have 440lbs on the trailer post (tongue weight). When you connect up most WDHs you raise the front of the trailer a few inches, then connect up the bars or chains or whatever makes up your variety of WDH. This essentially makes an arched bridge upon which you will be placing 440lbs of tongue weight. When you retract the trailer post, that weight is distributed between the ends of your arched bridge, which has two points to distribute that weight, the attachment points of the bars or chains on your trailer's frame rails and then also on the tow vehicle's ball.

The result in your case is part of that 440lbs (your 160lbs) is put onto your trailer's frame rails and therefore its axles. That's why the axles show 4100 when attached to the tow vehicle with the WDH, but only 3940 when the trailer post is supporting the 440. The other part of the 440 goes on your tow vehicle, causing it to show a higher weight than it would be unattached, but importantly much less than without the WDH, which has shared some of load with your trailer's frame rails/axles.

It helps me to draw two pictures of the tow vehicles and the trailer. The first can be while attached and the recorded weights, and the second as separate vehicles and weights.

If you had been able to re-weigh the tow vehicle, you would have found some, but not all, of that 440 had shown up on the tow vehicle. That's the point of the WDH, it shares the load and makes the vehicles feel more connected when going over dips, due to that bridge you have constructed.
Bill

[cpaharley2008]

Great explanation Bill, in layman terms....

[gbaglo]

Even I can comprehend that description.

[dave macrae]

I weighed ours @ 2100 kg , the Yukon was 3320 kg . we were loaded pretty heavy for a longer trip with bikes and generator on the back of the trailer and full tank of fresh water.

[Brian B-P]

Originally Posted by Posttoasties

I did notice a discrepancy – on the first weigh the trailer axle weighed 4,100 pounds (attached to the Durango with a WD hitch – in case that makes a difference). On the second weigh the trailer axle weighs 3,940 (not attached to anything). What happened to the other 160 pounds?

Part 1:

Originally Posted by jxoco

The weight distribution hitch put 160 lbs of the tow vehicle onto the trailer.

Part 2:
When the WD system is applied, it forces the trailer axles and the tug's front axle to carry more load, and the tug's rear axle less. The Durango's front axle is 10 feet from the rear axle, and the trailer's axles (the midpoint between them) are about 14 feet from the Durango's rear axle, so the front axle gets a larger share; the front axle probably got 225 pounds (think of a teeter-totter which one shorter end, balancing with a bigger kid on it than the kid on the long end). The point of a WD system is to relieve the tug's rear axle of load, and in this case it would carry about 385 pounds less than without WD (160 pounds to the trailer, and about 225 pounds to the front axle). This assumes that the trailer is towed level so its axles are loaded equally, which might not be true, so the numbers could be a bit different.

And a qualifier:
The tongue jack is behind the ball location, so it carries more load than the hitch would... and so with the trailer on the tongue jack the axles are carrying very slightly less than they would when hitched (and with no WD). This is a tiny effect.


Transferring 225 pounds to the front axle with the WD might a bit excessive for a tongue weight of 440 pounds, but it's in the right vicinity. All of those scale readings are to the nearest 20 pounds, and might be a bit further off than that, so the data isn't accurate enough to really know.

[Posttoasties]

Thank you all for the replies. I thought it had something to do with the WD hitch - I just didn't know how or why. I appreciate the elementary level (my level) explanations and now I think I may even understand how a WD hitch does what it does....