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Old 05-06-2016, 06:21 PM   #15
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It is some work up front, but when it's done one time, that $16 three-pete ends. Plus the time and miles to get it done properly.
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Old 05-06-2016, 06:24 PM   #16
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Btw, ypu can probably find automakers cog of drivers position online. It's about 5" forward of the seat back at the cushion level.
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Old 05-06-2016, 07:00 PM   #17
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[QUOTE=A W Warn;1787484]I'm withdrawing my offer to participate. For me, that is too much measuring to get exact weight placement of every item added to the vehicles so that the results will be accurate. I'm not willing to take the time to do it.

No problem- I appreciate your looking at it. I myself am not too fussy about being exact, and if I am off by 50 lbs or so on the axle weights, I'll be happy because I'll shoot for being under my ratings anyway.
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Old 05-06-2016, 07:28 PM   #18
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AW, also the placement of items has an additive effect and isn't as crucial as the dimensions of the vehicle and AS. That's where the multiplication effect comes in. The formulas are all based on TV wheelbase, tv overhang, AS ball to axle, ball to receiver, distances. If these are off, every item placed anywhere is inaccurate by a multiplier. Add together each item which is off and you get a big number. I'm like clamb, axle weights Tha are off by a dozen pounds and the whole rig off by 150 pounds is fine. That's within the accuracy of the cert scales and works for me.
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Old 05-07-2016, 12:38 AM   #19
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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.
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Old 05-07-2016, 01:53 AM   #20
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Looking for a few to try out a WDH spreadsheet

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ID:	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.


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Old 05-07-2016, 06:56 AM   #21
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Quote:
Originally Posted by guskmg View Post
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.
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Old 05-07-2016, 07:07 AM   #22
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This is all beyond me but, please keep the discussion going as it is interesting and has relevancy. I'm staying tuned.
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Old 05-07-2016, 07:51 AM   #23
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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.
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Old 05-07-2016, 01:48 PM   #24
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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.
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Old 05-07-2016, 02:02 PM   #25
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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.
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Old 05-07-2016, 02:14 PM   #26
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Quote:
Originally Posted by J. Morgan View Post
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.
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Old 05-07-2016, 02:31 PM   #27
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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.
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Old 05-07-2016, 02:35 PM   #28
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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.
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