Looking for a few to try out a WDH spreadsheet

[dznf0g]

Originally Posted by guskmg

Like I said before, it is the same as weight and balance calculations for an aircraft before flight. as far as the longitudinal axis is concerned. The TV is one part of the problem the TT is the second part of the problem and the third part is the combination. What to do: weight both TV & TT empty or full, but separately, then calculate where the center of gravity (CG) is for each. If you weigh the TV & TT full then you do not have to calculate the additional weight and distance of things you later add. Think moments = weight X distance (or torque if you prefer). Pick a datum like the TV front bumper and the tip of the TT coupler for measuring distances. Make your measurement from that point for each vehicle. On the TV it is somewhere between the axles and on the TT it is some where between the coupler socket and the center of the axle(s). Everything always must be level or else the distances used for calculation wii be in error. Once you have the moments calculated you can add or subtract them, depending on weight added or subtracted to reach a final moment. Moment divided by weight = distance. If that is your final moment then that is your CG. Do that for both TV & TT. Remember Airstream recommends a TT tongue weight of 10-12% of GW as an acceptable range for towing. Is your CG within this range?
Now the TV: weight axles and calculate the TVs CG. Take the numbers off the door placard and figure that CG. It may vary greatly because that is aft maximum CG. On pickups that CG will be very far aft. On the tow vehicle the CG you compute should be further forward or you will experience understeer. Too far forward and you have oversteer. Now Connect the two together, tighten up the equalizer bars and recalculate the TV CG with the TT attached. To recap: figure the TT CG, then when it is with in the 10-12% range add that weight to the tow vehicles calculation and see how much the TV CG shifts forward. The TV's forward CG (with driver and minimum fuel (as close to empty as you can get and still drive) verses the maximal allowable weight CG would be the TV operating CG range. Bear in mind that at either ends of this range are under and over steer conditions that may not feel comfortable on long trip. Once you make a diagram of the above basics all you have to do future weight changes is weigh the item and measure the distance, multiply then add or subtract the moment, divide the new moment by the new weight for the new CG.
guskmg

All that is true, and was used for the development of the sheets. The point here is to end up with a simple tool to use (not to develop though) so that if you are one who: uses varying amount of gear/toys on different trips; buys a new TT or TV; substantially relocate things in the truck or trailer; take guests (grandkids,etc.); or just develop "load creep" over time (we all do); there is a tool to pretty quickly see where your are without taking time and money out of your schedule to go and weigh. (Although I still recommend weighing every few years or so to verify your load.

We haven't talked about it yet, as I still have some cleaning up to do, but a PPP hitch changes Colby's sheets somewhat. The PPP adds both weight and distance characteristic differences to the calculations. I was kind of questioning some of the math, so got out the Sherline to measure the receiver weight. at the point of receiver insertion, with the stinger installed. I found some very interesting conclusions.

More to come on that sheet, if anyone is interested after trying Colby's calculator above.

Yes, this seems complicated, and it is to develop....but after it is done, one only has to plug in a few numbers and you get a pretty accurate picture where you are.

[xrvr]

This is all beyond me but, please keep the discussion going as it is interesting and has relevancy. I'm staying tuned.

[dznf0g]

Originally Posted by avionstream

This is all beyond me but, please keep the discussion going as it is interesting and has relevancy. I'm staying tuned.

That's just the point of developing this sheet. For those who feel it is beyond them, a simple plug in of a few tt and tv specs, as well as a scale ticket can spit out your results without racking your brain. It will, when polished up, answer so many questions about your particular setup, help with purchase decisions (ie, 1/2 ton vs. 3/4 ton, etc) and take a lot of ambiguity out of many of these thread discussions.

[slowmover]

The ambiguity comes by believing weight to be the foremost consideration. It isn't.

The majority of vehicles that can pull an Airstream have plenty of capacity at the axles to handle the thing.

The differentiation is only for those who carry too much junk with them.

Someone who is a vacationer towing about 5k miles annually is better served by a daily driver vehicle safer than a pickup by design.

A tow vehicle which cannot stop as quickly or maneuvers slower than an AS has made a step backwards in his family's safety. This describes probably every pickup.

Increased cargo capacity doesn't make a safer vehicle, but one which is worse.

Quality of the lash up is the reason for using the scales. Concerns about tongue weight, etc, are misplaced. They're minor.

In general, put the load in the trailer. Work the lash up from there.

[dznf0g]

That's you're opinion and that's fine for you, but as an industry professional I respectfully disagree with much of your statements, but I won't argue them here, as they have little to do with the purpose of these sheets and this thread.

[slowmover]

Originally Posted by J. Morgan

Attachment 262053

If I only had a truck scale....

(Yeah, that is a scale in the foreground, less than 50 feet from me as I type this)

I have at different times taken down different weights, some axle weights, some unit weights, and some cargo weights on my Airstream Combo, but never a true tongue weight or all of these at the same time.

Who knows, maybe I might do all of that next time I move it. .

Numerical value for each wheel position. Solo, hitched, and with WD applied

. (Also tells which tire on an axle end of the TV is the one which determines TV tire pressure minimum for that axle).

One learns how well that hitch receiver is applying the load. The usual weak link is today's poorly designed receivers. If some diagonal bracing means less force needed to achieve a given TW distribution, one has gone the right direction. IOW, just because one can hit the mark it is not the same as "best".

If one can do 1/3 - 1/3 - 1/3 TW distribution where the final 10% is on the TV rear axle, one has nailed the formula. What we did with the custom hitch receivers in the 1960s and 70s.

Better said, it's proven the usual weak links aren't present. This is past best hitch head angle, etc.

What someone chooses to run past this is another question entirely. My father and grandfather always opted for maximum transfer to the TT for best braking from that unit. The final test was being able to stop more quickly hitched than solo. It's been my guideline as well.

On a Hensley, hitch head tilt is cutting the stinger and rewelding for more initial force. See Thomsons comments about the Hensley.

Etcetera.

[dznf0g]

Originally Posted by slowmover

Numerical value for each wheel position. Solo, hitched, and with WD applied

. (Also tells which tire on an axle end of the TV is the one which determines TV tire pressure minimum for that axle).

One learns how well that hitch receiver is applying the load. The usual weak link is today's poorly designed receivers. If some diagonal bracing means less force needed to achieve a given TW distribution, one has gone the right direction. IOW, just because one can hit the mark it is not the same as "best".

If one can do 1/3 - 1/3 - 1/3 TW distribution where the final 10% is on the TV rear axle, one has nailed the formula. What we did with the custom hitch receivers in the 1960s and 70s.

Better said, it's proven the usual weak links aren't present. This is past best hitch head angle, etc.

What someone chooses to run past this is another question entirely. My father and grandfather always opted for maximum transfer to the TT for best braking from that unit. The final test was being able to stop more quickly hitched than solo. It's been my guideline as well.

On a Hensley, hitch head tilt is cutting the stinger and rewelding for more initial force. See Thomsons comments about the Hensley.

Etcetera.

That's exactly why I have an adjustable tilt stinger for my hensley. Sean built a handful for forum hand raisers a few years back.

[slowmover]

So do I as you know. But I'd rather cut and re weld an original stinger to get shortest length. The adjustable is good for the changes to the height of either of these vehicles. Once repairs and upgrades are done, the adjustable piece is less desirable. I've called it my insurance on getting out of town ahead of a hurricane. Hasn't mattered where I am via a vis vehicle changes as the adjustable can compensate.

[dznf0g]

1/3, 1/3, 1/3 is a myth as being necessary and physically impossible unless tv wheelbase is very close to the distance between ball and trailer axle. There are some other variables in there as well, but that's the big one. TV manufacturers don't even discuss the 3rd, 3rd 3rd split anymore.

[J. Morgan]

What I do is to set it up in a way that I think is good, test drive it a bit and adjust if needed.

When it feels really good, I leave it alone and try to put it back the same way next trip and then repeat the process.

I do this this way even though I own my own truck scale that I can use whenever I want.

What I have found in my experience is that if I try to set up WD "by the book", this method takes too much weight off of the rear tow vehicle axle.

My combination tows MUCH better with just a little squat on the back of the tow vehicle.


Superat stultitia.

[slowmover]

Originally Posted by dznf0g

1/3, 1/3, 1/3 is a myth as being necessary and physically impossible unless tv wheelbase is very close to the distance between ball and trailer axle. There are some other variables in there as well, but that's the big one. TV manufacturers don't even discuss the 3rd, 3rd 3rd split anymore.

You let us know once you've tried it. The minimum is still front axle load restoration. If you can't get past that, then you've still a starting point.

1/3 is a guideline. If you want worst, try the 50% crap. That sells pickups to the unwary. It doesn't designate best lash up.

[slowmover]

Originally Posted by J. Morgan

What I do is to set it up in a way that I think is good, test drive it a bit and adjust if needed.

When it feels really good, I leave it alone and try to put it back the same way next trip and then repeat the process.

I do this this way even though I own my own truck scale that I can use whenever I want.

What I have found in my experience is that if I try to set up WD "by the book", this method takes too much weight off of the rear tow vehicle axle.

My combination tows MUCH better with just a little squat on the back of the tow vehicle.


Superat stultitia.

1/3 is difficult. And pickups tend to be too light on rear axle. Thus why one leaves the final 10% or so on that axle.

The earlier suggestion has little to do with exactly how "you" run yours. But it would help the spreadsheet developer (past what you may wish to change, if anything).

[dznf0g]

Originally Posted by slowmover

You let us know once you've tried it. The minimum is still front axle load restoration. If you can't get past that, then you've still a starting point.

1/3 is a guideline. If you want worst, try the 50% crap. That sells pickups to the unwary. It doesn't designate best lash up.

Use the sheet and make up fictitious wheel bases and axle to ball and ball to trailer axle and use actual math to back up your statements. 3rds would only be possible if your wd was AT the rear axle, there was no overhang, axle and truck wb and trailer ball-to-axle were equadistant. Doesn't matter much whether it's a truck or car.

[slowmover]

Wrong. Done many times with long overhang cars.

[dznf0g]

Originally Posted by slowmover

Wrong. Done many times with long overhang cars.

Not unless you had a very short trailer. Work the math and prove me wrong.

[J. Morgan]

Originally Posted by slowmover

1/3 is difficult. And pickups tend to be too light on rear axle. Thus why one leaves the final 10% or so on that axle.

The earlier suggestion has little to do with exactly how "you" run yours. But it would help the spreadsheet developer (past what you may wish to change, if anything).

My comment was just a general comment, I wasn't really addressing any specific post at all, but just throwing something out there that works for me.

My goal is a combination that tows excellent, kinda like a class 8 tractor trailer is an excellent benchmark.

As for me, my setup reaches this benchmark and maybe even a little more. (And I know that is a bold statement. )


Superat stultitia.

[J. Morgan]

Fwiw, next time I hook or unhook I will endeavor to get you some information for your spreadsheet.

I think what you guys are doing is cool and worthwhile.

I have a lot of weight data from my last unhook, but I did not unhook and measure tongue weight. I never have done that. But I will before I leave NM.


Superat stultitia.

[dznf0g]

Thank you Morgan. And also I was a bit short in #35. I mean prove in the mathematical sense of proof, not in the playground sense. We need proof checkers to make sure there are no errors in the application on the indesputable theories of physics and math.
I still say, unless you make up a vehicles dimensions which don't exist, you can't achieve a 3rd 3rd 3rd split of added rear axle weight.

[dznf0g]

Originally Posted by slowmover

You let us know once you've tried it. The minimum is still front axle load restoration. If you can't get past that, then you've still a starting point.

1/3 is a guideline. If you want worst, try the 50% crap. That sells pickups to the unwary. It doesn't designate best lash up.

I don,t disagree with you here relative to the "restore 50% of the original ride height" thing...and it brings up a slightly off topic head scratcher for me. I've read on here repeatedly, that folks have difficulty restoring even 50% of the ride height with a long hitch bar or a Hensley/PP stinger. I have no problem, with a maximum load or a minimal load restoring a front ride height well past the original loaded TV ride height.....with still 1 notch of pull left on the HAHA jacks. I mean hiked up in the rear and nose dived in the front. I am not in the camp of believing that the length of the stinger has any appreciable effect on that issue. I think something is off in the setup if that is occurring. It certainly has an effect on the amount of force required on the spring bar ends, but not past the range of adjustment available. The sheet predictions seem to verify this, but I do have some additional work to do on the spring bar force exerted at various settings to be confident of the values of those predictions. When my setup is balanced per the sheet and verified by scales, (this was my "baseline" weighing with not much in the truck) the rear of the truck was squatted 2" and the front was at it's original unladen ride height with WD hooked up. With WD hooked up at the third notch and 900#s of receiver weight.
With WD relaxed front is up 1/2" and rear is squatted 2 5/8".

[clamb]

Originally Posted by J. Morgan

What I have found in my experience is that if I try to set up WD "by the book", this method takes too much weight off of the rear tow vehicle axle.

My combination tows MUCH better with just a little squat on the back of the tow vehicle.


Superat stultitia.

J.M. ( and Slowmover), thanks for joining the fray! I must admit, I was a bit intimidated by starting this, being a relative newbie and all. And I knew I would be getting input from some, if not many, who have towed for many years and have set their rigs up by feel, by eyeball, or by 6th sense. And there is really nothing wrong with that. Whatever works for you and gets you safely to the next campsite is what it's all about.

In my situation, with a new F150, Ford recommends putting 25% of the weight back to the front axle, thus the section of the spreadsheet where you can input the % to return to the front and see how many lbs. that is. This seems to agree with your comment about squatting a bit in the rear end.

I hope that you will give it a try and help us find out if there is something about the spreadsheet that needs to be tweaked. You can post your filled in sheet here and we can review it. I have protected all cells in the sheet except user inputs, so the formulas and basic structure can't be changed.