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...................Teardrop Trailer Page 14
..........................................................-- Thoughts about safe construction --
I really hope that what I have to say on this page will contribute to your safety and to the safety of others that share the road with you. In the fall of 2003 returning to Utah from a trip to Calif. and Oregon the tongue on our teardrop cracked on a section of rough road by Salt Lake City. Lucky for us and others it cracked across the bottom of the tongue and up both sides of the tongue. It didn't crack across the top so even though the front of the trailer went down on to the pavement at speed it slid on the bottom of the tongue near the front of the body and I was able to get off the interstate and onto the shoulder with the trailer still attached to the truck.
Even though the road was rough there and caused it to fail there it would have eventually failed somewhere else. I was also lucky to find a place with a portable welder that came to the trailer and welded the tongue back in place and we were on our way in about an hour.
At the time this happened the trailer had about 40,000 miles on it with no problems, so if I was someone who didn't put on very many miles per year the problem might not have occurred for many years.
I would like to show how I constructed the tongue in the first place and let you know what probably caused it to fail so that you might not make the same mistake.
My frame is .120 X 2 X 2 square tubing and I wouldn't change that. I made the tongue out of the same material. When the trailer was finished it ended up with a lot of tongue weight with the kitchen in the front and the wheels shoved back. This led me to reinforce the tongue with 2 pieces of .250 X 1 X 1 square tubing under the 2 X 2 tubing (see the sketch above).
The point a tongue is most likely to fail is normally right at the front of the body. As you move out the length of the tongue from the body it can decrease in strength as you near the coupler on the end. Think of the strain the tongue is under. If you grab the tongue at the body it is very hard to lift. If you grab the tongue where it hooks on the car it is much easier to lift, so the largest stress on the tongue is at the body.
I re-enforced that part of the tongue with the 1 X 1 thick wall tubing. But what I did was transfer the weak spot further out on the tongue. It cracked (see sketch) right in front of where the 1 X 1 ended. I'm sure though that without the 1 X 1 it would have failed long ago at the point just in front of the body.
To fix the problem I temporarily cut the two diagonal braces where they attached to the tongue. I then widened that cut area between the tongue and the diagonal braces enough so I could slide two pieces of 3/16 X 3 inch steel strap along the tongue from under the body along the sides of the tongue to in front of the first gusset where the tongue steps up. Also when we repaired the tongue on the road we had welded a piece of 1/4 X 2 inch strap from the body forward on the bottom of the tongue over the cracked area.
Next I re-welded the diagonal braces back to the tongue and onto the new piece of strap.
I now was worried that the weak link in the tongue was going to be just ahead of the new bracing I had welded onto the sides of the tongue in the previous step.
So I welded a piece of rectangular tubing from up near the coupler back to the newly re-enforced area. That piece was also tied into the section of the tongue going back to the body with a gusset.
A picture of the finished repair. I feel very good about this tongue now!! One thing that I also learned in this is to not weld vertically on your tongue as that will induce a weaker point. The new strap that goes along the tongue and under the body is cut at an angle under the body and welded at an angle. Also at the front of that piece it is welded at an angle to the tongue.
Notice also that the gussets I had welded in are diamond shaped so that the welds will go at an angle to vertical.
My tongue is more complex than most since I wanted the trailer to sit low and the tongue has to come up to the ball height on my pickup. Still if the tongue would have been a straight one it would have failed in the same place. Notice it didn't fail at the step area, but behind the first set of gussets.
The moral of the story is I would never build a tongue out of .120 (1/8 inch) square tubing again. Don't build your tongue out of anything less than .250 square tubing and if you have any concerns at all about what you are doing structurally have a competent welder/builder check it. Remember this tongue didn't fail for over 40,000 miles so don't think you are safe just because everything appears fine right now.
This might be mute for a teardrop in the 600 to 800 lb. range, but a lot of you are building 5 X 9 and 5 X 10 teardrops and it is going to be very hard to keep your weight down with these, especially when you consider having water, a battery and all the other items you are going to haul in your trailer. I figure my dry weight is about 300 lb. less than my loaded weight on a trip.
The weight difference in a tongue made from 1/8 vs. 1/4 inch material is probably less than 30 lb. and I can guarantee that even with the smallest car this added weight won't cause a difference in pulling the trailer.
I constantly see efforts from new builders to make everything, including the frame, as light as possible. Please don't jeopardize your safety and the safety of others that share the road with you in the process.
I would like to also bring up one other point. A number of you are using frames that are bolted together. Some of you, and it might be something I would also do, are welding that same frame together. I have mixed feelings about that.
Forces are transmitted through trailer frames in a similar manner to bridges and other structures. Some structures are designed to be pinned and/or riveted together. The way a riveted or bolted joint transmits stress and forces is totally different than a welded or glued joint. If the bridges that are now pinned and riveted together were welded they would fail as that is not the way they were designed.
I'm sure that the designers of these trailers had to deal with a couple different factors. One was design them so they bolt together and so they can be shipped from China or where ever in as small a package as possible. Two, that they are made from the minimum materials for the weight they will have to carry to keep prices down. I'm also not sure of the grade of steel they are using and how it reacts to welding. These trailers have been designed to carry their rated load when they are assembled to the designed specs. Moving crossmembers and axles and welding them is not how they were designed. The welding might make them stronger, but then again who knows for sure except the person that designed the trailer in the first place.
There again this is probably not relevant on a light weight trailer, but some of you are building 5 X 9's and even larger teardrops on these frames. By the time you make the modifications most of you are making to these frames you could of had a custom made frame for slightly more money. Money that if you figured it over the life span of the trailer would be minimal.
I'm sure some of you feel I'm really being an ass about this, but I think this will save some a lot of heartache down the road. For what it is worth I had a couple years of engineering courses in college (and I stayed at a Holiday Inn last night). I would sure like to hear discussion on this from some mechanical/structural engineers.
A little on A-Frame type tongues. First I think the A-Frame type tongue (see next picture) has a lot going for it. It is stronger than a single tongue, like mine above, if built with the same thickness of materials since basically you have two tongues. The design also has built in sideways structural stability that I had to add with diagonal side pieces to mine.
The two drawbacks I see is that you can't "Jack-knife" the trailer as much in a parking situation where it is handy to have the trailer 90 degrees to the tow vehicle and that it is harder to mount a jack that swings up, like in the above pictures. I like these jacks as they swing completely out of the way and are not the lowest thing on the tongue. I see people with A-frame tongues that mount the jack just behind the coupling point, but since it doesn't swing up, just cranks up, this often results in the bottom of the jack potentially dragging on the ground in sever dip type situations. To help this a lot of people remove the wheel except when they are using it. Still the tube hangs down and I've seen a number of the tubes on these bent.
I bought a car-hauler type trailer a couple years ago and the way they designed the jack does away with the problem of the jack being a low point on the tongue. In the above picture you can see how they added a jack support off one side of the A-frame that mounts the jack in the middle of the A-frame on a round tube so that the jack can swivel.
When the trailer is attached to the tow vehicle you pull a pin in the support and swing the jack up out of the way and re-pin it. This is a slick solution to the problem, and I wish I could say I came up with it, but I didn't. I would definitely do this if I had an A-frame type tongue.
c ya, Sum
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