tongue weight : real wt. vs. projected weight

[working on it]

From day one 'til now, I've been a great fan of Angib's works on behalf of TnTTT members. His design portfolio, comments, new ideas, and especially his files on tongue strength and my favorite: Trailer Balance. I've gone overboard on manipulating figures to try to get a perfect balance, using his basic formulae and my alterations. I guided my whole build on the projected results, not having actual weights or placement of items ready at hand.Here's an earlier post of mine that shows what I was trying to do: http://www.tnttt.com/viewtopic.php?f=21&t=48615&hilit=tongue+weight+balance. Now, having finished my build, and envious of those that started their builds about the same time as myself (but have already taken them out), I packed the trailer as if I were to travel with it (simulated ice chest containing cinder blocks, not withstanding). I then got the bathroom scale out, and measured the tongue weight using this method

tongue weight 3.xls

(172 KiB) Downloaded 31 times

. Perhaps not the most accurate way to do it, but the only way I can do it in my limited garage bay space. On first weighing it, I got only 30lbs tongue weight, which was quite a shock!. I then went over the trailer, moved a water jug from the rear to the front , lightened the fuel by one gallon (too heavy for my wife to pour anyway), and added the extra balancing weights (2x15lb barbell weights) I had initially planned to use on the tongue . (didn't actually think they'd be needed), then checked it for front to rear level and side to side level, and inflated the tires to the same pressure (tires were not the same, after 6 months, so the trailer wasn't level)...that helped. With the re-leveled and re-balanced trailer, the measured tongue weight came to exactly 100 lbs (my goal from the start). Whether or not that is really accurate, I don't know, but it feels like 100 lbs when I lift it (much better than the 30 lbs at first try). If the weighing method is in the ballpark, then can I assume that the total trailer weight is around 1000 llbs, as the described method suggests? I don't remember where I found that method, but it seems to work. And as to my using Andrew's balance equation, somewhere I put weights in wrong, or was adding weights that are already included, as Andrew suggested in the earlier post, well anyway, my latest balance sheet appears to be wrong, I hope, that my tongue/(trailer wt. inferred) weights are as measured, not as my mishandling of Andrew's spreadsheet indicates. I re-did my latest version (to reflect the re-balancing I did this afternoon), condensed it to fit this forum's sizing limitations, and included (in the lower right hand portion) the weight of the trailer when last weighed plus my best guess of the added weights (400lbs less the 12lb jack plus added weight of 601.5lbs). Also shown is the tongue weight as measured. If you compare those figures to the spreadsheet, then you'll see that somewhere I really goofed, and Andrew was correct about my over-elaboration. Here it is:

balance condensed 7-6-13.xlsx

(78.76 KiB) Downloaded 31 times

I would like your feedback on this, especially from Andrew, to see where my data/plans went awry.

[Corwin C]

Your example shows how moving a small item can make a 70# difference in tongue weight. It sounds counter intuitive, but really it is not. Aircraft pilots make this calculation/measurement/adjustment every time they load an aircraft. While our situation isn't as critical as theirs, it is important to understand how moving items changes the balance and if you have issues, you will understand what corrective measures are necessary.

Also, when using Angib's spreadsheets, recognize that any "guesses" in the data entered makes the result a "guess" as well. Actually weighing parts and determining each CG eliminates the guesses, but at that point, you've built your trailer. It is a valuable tool, and a very good one, but realize that the real world doesn't always follow the engineering numbers exactly. Don't fret about not having the exact results that you were expecting ... quite frankly, I'm impressed that you were as close as you were.

Best wishes on your build...

[working on it]

Your example shows how moving a small item can make a 70# difference in tongue weight. It sounds counter intuitive, but really it is not. Aircraft pilots make this calculation/measurement/adjustment every time they load an aircraft. While our situation isn't as critical as theirs, it is important to understand how moving items changes the balance and if you have issues, you will understand what corrective measures are necessary.

Also, when using Angib's spreadsheets, recognize that any "guesses" in the data entered makes the result a "guess" as well. Actually weighing parts and determining each CG eliminates the guesses, but at that point, you've built your trailer. It is a valuable tool, and a very good one, but realize that the real world doesn't always follow the engineering numbers exactly. Don't fret about not having the exact results that you were expecting ... quite frankly, I'm impressed that you were as close as you were.

Best wishes on your build...

I was a bit overheated, and rushing to complete the previous post, and neglected to include what must be figured in to the big picture: I left out the sidebar with the basic weight of the upper structure itself (now shown highlighted in green). in my haste to make the observed tongue weight correspond to the calculated weight, it seemed to be superfluous. but it is not. So the calculated total weight must be in the ballpark of 1360lbs, while the observed tongue weight is what it is 100lbs. So then, I must assume that the tongue to total weight ratio is only 7.3% (maybe OK in Europe?) (and will fall to less as the consumables used as front ballast are lessened, for the trip home). My conclusion is that the trailer is overweight, and the tongue too light, at this point. I can't move any more items forward, but can only add more weight to the front (and overall weight). Perhaps fill the hollow tongue or front crossbeam with ballast? Anyway, I missed my goals, won't be able to tow it with the little cars as I had hoped, but am determined to make it work.

[working on it]

Since I now believe the trailer to be 1360+ lbs, with only 7.3% tongue weight, I figured to throw "lightweight" away, and added another 32lbs to the tongue (2 more barbell weights). Positioned behind the first set of balancing weights, they added 22 lbs at the hitch, changing the tongue to total weight ratio to 8.75%. Still not there.

not pretty, but detachable, and effective

100_3479.JPG (189.02 KiB) Viewed 814 times

[citylights]

Wow, I am still agonizing over how to make my tear waterproof, I had not thought too much about the overall weight and tongue weight.

I just figured I would move the battery or the cast iron cook ware back or forward depending on what the final tongue weight ended up being. Final resting place of those can go in the kitchen (back weight), an under bed storage near the axle (almost neutral, but a little forward weight), or in the tongue box (forward weight). Between those three choices, I figure I can balance it out.

I am planning on the battery in the tongue box and the cast iron in the kitchen.

I was also planning on a 1250 lb tear, but I think I am about 75% done and it is getting real hard to push up my driveway into the garage now. I knew I shouldn't have used 2x4 sub deck, 3/4 inch deck, 3/4 inch side walls and 2x2 spars! But I just couldn't help myself. Overbuilding has always been in my nature. I think I may end up closer to 2000 lb. Is that a heavyweight tear?

So what are you towing with that the weight is so critical? Oh, and I wouldn't add dead weights just to balance things out. I would move things around to balance things out. Stick the ice chest on the tongue if you must.

[KCStudly]

My advice would be to try other means; take the extra weight off the front/stop adding weight on the front and either remove weight from the rear or think seriously about moving the axle rearward.

Either that or shift your consumable weight closer to the axle and let it be. Easy to say, but perhaps hard to do. Just seems wrong to me to add dead weight.

Also, get a real total weight and stop assuming. You know what they say when you assume, you make an ass-out-of-u-and-me.

$.02

Sorry if this sounds harsh; I do admire your work. Reality check, maybe?

[les45]

I just use my camping gear and luggage stored all the way forward to get my tongue weight. Folding table, EZ-up, chairs, tool box, and boxes of galley stuff add a lot of weight to the tongue while towing. I still have my coolers in back under the counter. Also, I left my axle in its stock location on my NT 5X8. My rig weighs about 1,400 lbs loaded with a tongue weight of 160 lbs. After upgrading my tires to 13" passenger car tires, it tows fine. Didn't do anything else to try to adjust tongue weight during construction.

[eamarquardt]

Please forgive me, in advance, for being a "Gloomy Gus". Adding weights right at your coupler to achieve the right "tongue weight" is IMHO the WRONG approach. Tongue weight is only, again IMHO, an indication that your trailer is loaded in a balanced way that will help prevent the trailer from oscillating when the "stars are properly aligned". The stars being your speed, load, road, springs, tires, trailer balance, and a host of other factors. Generally the closer all of the weight is to the axle, the better. You can't add weight much further from the axle than right at your coupler.

IMHO you need to look seriously at the weight distribution of the total load on your trailer. The closer heavy items are to the axle the better. I agree that moving the axle or serious redistribution of the weight is the right answer. Adding weights near the coupler is at best not a good solution and at at worst a recipe for potential disaster.

We were near a truck towing a trailer with a dune buggy on it this weekend. He was right on the edge at times (beginning to oscillate) and it didn't seem to phase him one bit. I passed him as soon as practical as I doubt he'd have listened to me. I have signaled others over at times and tried to explain the dangers of their behavior. Some listen, some don't.

For your own sake, fix the problem the right way, not by adding weights at the coupler which is NOT going to prevent oscillating.

Again, IMHO, the more tongue weight, the better as long as your vehicle is capable of handling the weight. The further back your axle (with attendant increase in tongue weight) the better your trailer is going to tow.

Cheers,

Gus

[working on it]

I just use my camping gear and luggage stored all the way forward to get my tongue weight. Folding table, EZ-up, chairs, tool box, and boxes of galley stuff add a lot of weight to the tongue while towing. I still have my coolers in back under the counter. Also, I left my axle in its stock location on my NT 5X8. My rig weighs about 1,400 lbs loaded with a tongue weight of 160 lbs. After upgrading my tires to 13" passenger car tires, it tows fine. Didn't do anything else to try to adjust tongue weight during construction.

Les- that's exactly the way I had planned to do it, all along, except that I was aiming for a lower tongue/total weight. I always thought that a 55% front, 45% rear wheelbased centerline worked better for a light tow vehicle (which I have), so I left the axle where it was, and added a 24" rear overhang (necessitated by the #1 priority-a generator for boondocking), and extended the front by 12". The difference in added weight for the disparate extensions was to be compensated for with the longer, much heavier, (w/extra bracing) stronger drawbar. Note the start picture versus the completed shell side views:. Still roughly the same initial balance. Then, the trailer balance worksheet was utilized on all ensuing decisions. I thought I was on the right track! And Les, if you compare the side views of your trailer next to mine

les45.jpg (7.07 KiB) Viewed 756 times

workingonit2.jpg (14.77 KiB) Viewed 756 times

, then it looks like your rear weight bias would be as great or more than mine! KC, and Gus- I appreciate what you're saying...I really don't want to add the weight that way, or any weight at all; it offends my "function first" viewpoint, since the weights serve as a bandaid not a solution, and serve no other function. They're like an albatross around my trailer's neck (so to speak). I've had to do quick-fixes before, on my other trailers, just as interim solutions, before I found the answers. Note: I made the point that they were detachable; and they will be, when I re-configure correctly. First on the agenda: a true weight of the trailer. Then I can see how much error is involved, and how drastic the remedy must be. Probably Draconian. My 2500HD will be the tow vehicle for the trip to the scales (with attached tongue weights). It can pull anything, so a little trailer "jitterbugging" (oscillating) behind it should not be catastrophic. As a further comment, I've noticed some teardrops with HUGE tongue boxes, some just barely allowing room for the coupler and tongue jack. I wonder how many of those were made as camouflage for other "quick fixes". If I built a box over my spare and toolbox, I could throw in another 100lbs of weights, unseen! Just kidding. I'm actually worried that my trailer just won't be streetable anytime soon.

[citylights]

I could throw in another 100lbs of weights, unseen!

Just make sure the weights are in the form of cast iron cook ware and you won't offend anyone's sensibilities!

[working on it]

Just make sure the weights are in the form of cast iron cook ware and you won't offend anyone's sensibilities!

I had thought about that last night, but then I'd have to carry at least the same amount of weight in Coleman equipment in my rear compartment, lest I offend my fellow Corpsmen. The opposing weights would cancel out each other, and then I'd be in the same pickle I'm in now.

[48Rob]

I'm not an engineer, but 55/45 is cutting it very, very close considering you have a (light) bed in front of the axle and a (heavy)galley behind.

Looking at your pictures, it jumps out at me that the axle needs to be moved back about a foot.

Rob

[les45]

I could throw in another 100lbs of weights, unseen!

Just make sure the weights are in the form of cast iron cook ware and you won't offend anyone's sensibilities!

FWIW - this quote is edited wrong; I didn't say anything about adding weights.

The real problem is obvious in looking at this pic:



All that weight of generator, fuel, water, and AC all way behind the axle with nothing up front plus a long tongue. I agree with Rob that you need to move the axle back at least a foot to get this load properly balanced.

[Kharn]

Working on it:
Try moving the generator from the galley to the tongue. I'd also move the fuel away from the galley if possible, gas isn't the most appetizing odor. Or, if you're set on those being in the galley, put one or two group 27 deep cycle batteries on the tongue. A group 27 battery weighs around 55lb, so they'd add weight very quickly, plus reduce your generator run time requirements, possibly allowing you to downsize both the generator and the fuel.

[working on it]

Guys- the original trailer frame was lengthened by 24" in the rear just to accommodate the 2500watt generator. My error at the start was only adding 12" to the front. As a partial concession to the difference in length (changing the bias to 45/55), the tongue was made much longer and heavier (but obviously, not enough) . I had no indications that it was unbalanced at first...when the frame and floor were done , it was taken to a scale and weighed (exactly 400lbs), and it towed and tracked perfectly. Later, as I added the upper structure, and the generator, I had a time lifting the tongue and towing it by hand when it needed to be moved...again, no indication of weight imbalance. Then came the day when I brought it home, after the doors and hatch were finished; 55 miles over a mix of bad roads and highway traffic again it was a perfect pull (and it was hard to lift onto the hitch ball (tongue was still heavy at that time). I had a booger of a time unhitching and hauling it into my garage, over a ridge of dirt and 15 degree cement apron. Still no indications of imbalance, front to rear, just heavy! Then the trim out began: I always included the generator (and the A/C almost from the start) in all my plans and calculations, and moved weights around to compensate, and everything hinged on that premise. The heavy fuel jug, and the water jug in the rear came later, as did the battery, but the calculations predicted no major problem. I may never know where my calcs went wrong, but they did. I've already moved the water jug forward for travel, and intend to move the battery and fuel jug (maybe convert to jerrycans flanking the spare tire?) to the tongue as well. The Coleman equipment weight is negligible, so that will stay put. And, I've plenty of side and rear photos in my gallery, but there are a couple that show the front mounted spare and small toolbox which should demonstrate my trying to supplement the 45/55 balance (I used lightweight angle iron to make the toolbox outriggers, not dreaming that I would have too little weight there). And as I stated before, the spare water and the ice chest were always intended to ride inside the cabin, forward of the center of gravity. I'm going to re-fit the front end, and either build a tongue box around the spare (to secure battery, and maybe fuel cans) or find one that will fit the space there. Either way, more weight will be transferred (and leave some room in the galley for "cooking gear" at last. Sorry, lightweight only, no cast iron. I may end up having to put in a heavier-duty axle, but I do not want to move it rearwards; I've grown used to the stance. Other options still exist to supplement towing stability : single beam weight distributing device, friction or hydraulic sway control, and yes "hidden tongue weights". Guys-I really do appreciate your concern, honestly, but I have to do this in my own perverse out-of-the-box way. I never wanted a "show" trailer, nor cookie cutter design, and wanted the bones and repurposed hardware and improvisations to stick out, by intention, from the first. Here's a confession: if I had an idea, and later found it being used by another, before me, I would go another direction. Just to try to live up to (or down to) my tradition of "southern engineering" (there are other terms for it). I like problem solving, and learning as I go, but I am struggling to keep a promise and a deadline here.