Trailer modification

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Hopefully I can explain this so it is some what understandable...First is a 48 foot Wabash single drop trailer (Commercial trailer)My goal is to pintle hook it to my custom coach (Freightliner FLD120)First we would remove the king pin.  Mostly this is to just save weight.  The I am looking at using 3x8 .125 wall rectangular tubing (thinking about 4x12) to construct a tongue from under the upper deck.  The upper deck is 10 feet long.  We would place to rails down either side the entire length (this gives me more contact/connection then the king pin plate).  We would then come out 4 feet in a typical tongue A arm design (should be enough for a 102 wide trailer).  I would then using the same tubing run a a piece from the lower deck where the frame is back up to the tongue just where the upper deck begins.  I would then cross brace the structure at the furthest point back, the furthest forward point under the trailer where the pieces from the lower bracing come up and meet.I guess what I am looking for more or less is input as well as other suggestions/ideas on how to tackle this project as this is about as custom as you can get.The trailer is used solely for pulling a race truck, thus the trailer will never carry its rated capacity.  Scaled it weighed about 30,000 lbs.  The pintle hook being used is a Holland rated for 100,000 lbs pull 20,000 vertical as well as an air snubber. My current setup is very similar but utilizes a dolly between the trailer and coach making it double pinned.Looking forward to hearing your ideas ...Steven
Reply:I have my easy chair, I have my popcorn, and  I have my reading glasses.  Ok let the fun begin.Lincoln Power MIG 215Lincoln WeldPak 3200HDLincon ProCut 25Lincoln WeldanPower 225 AC/DCIf all else fails... buy more tools
Reply:I need pictures. both of the towing combo and the trailer, as well as the planned mods just to understand what you're trying to do.That being said, Papa pass the popcorn, and do you need a beer while I'm up? this is going to get interesting.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:First off, make sure to equip yourself with one of the high quality 120V MIG welders from Harbor Freight before starting, not one of those cheapo Lincoln, Miller or Hobart, only the best will do for this project.  excuse me while I go to the restroom and grab another beer and get some cheese covered popcorn.
Reply:how qualified are you as a welder?Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:Originally Posted by turkhow qualified are you as a welder?
Reply:so you are not new to welding, that is what most of the above comments are taking as an assumption.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power tools
Reply:While building a moster truck is impressive. Pulling simething that big down the hiway at highway speeds causes concerns. Is this going to be a straight out hitch or are you going to make a drop hitch. I wouldnt think the ride height would work going from fith wheel to pintle.Millermatic 252millermatic 175miller 300 Thunderboltlincoln ranger 250smith torcheslots of bfh'sIf it dont fit get a bigger hammer
Reply:If I picture this right, that would put weight a good deal back in respect to the tractor center. A dolly (under the drop trailer) to pintle would seem to make more sense. I do think that over time the vert load on the pintle (if I see this right) would make me nervous.Pics of the setup now with a peek at your tractor could help.Matt
Reply:It depends on what you call a 48 foot Wabash single drop trailer (Commercial trailer)
Reply:The current configuration is a coach (coach meaning the back is flat like a bus, no deck)  Conencted to a dolley via pintle, then king pinned to the trailer.  This makes us double pinned.  A company called Switch Quick makes locking bars for commercial dollies allowing tandoms to back up and has given us one to use.  The axle spread between dolley and the coach is 9 feet so even using the locking bars we scrub tires and are still limited in being able to back up.  By doing this modificaiton we are hoping to:  Be able to back up normally, shorten the rig, place more weight down on the rear axle giving us more traction (currently we are pulling the weight)In the past we have cut off 8 feet of the upper section of the trailer and A frame it from the under side to a pintle connection.  I have also done the same but used a stinger hitch.In this case we are going to leave the upper deck in tact and A frame off of that.  The pintle will be much higher then your typical setup.The pintle on the coach is much higher then the norm already becuase of the dolley.  Think of a FedX tandom and the height of the bumper where the dolley connects.  That is the height of where the pintle is for me so the drop will be very minimal in any at all.My only concern actualy is the torsional stress on the extended Freightliner chasis and we have already made plans to box that section of frame.I will scan some scetches I made that should give a better idea of this.In terms of warantee on the trailer, it well beyond that in years so no worries there.As for saving weight on the king pin removal the few hundred pounds is technicaly a none issue but I am attemting to save every bit off the of the toungue weight as possible.There is very little that surprises me these days in terms of fabrication...  Ever see a Honda tracked snow blower made into a electric over hydrolic jack?  Even better mounting a altenator to recharge the battery and power some lights so you can change tires in the dark?  Now place an inverter on it and power 112v items?  Yep were that crazy
Reply:Originally Posted by 1QuickSIQualified?  Hmmmm....  Does building and campaigning a professional monster truck rate in terms of fabrication and ability?
Reply:To illustrate a point, this is a quick snap of Jurassic Attack at a local show.  Some of the "Welding" on this rig is just NASTY.  Yes, it flies and jumps and holds together, but I wouldn't attest to the quality of the craftsmanship.I do not know what team you work with but Frank owns several rigs for TV and stadium circuits... This work is less than stellar. Attached ImagesLater,Jason
Reply:Originally Posted by 1QuickSI ... Ever see a Honda tracked snow blower made into a electric over hydrolic jack?  Even better mounting a altenator to recharge the battery and power some lights so you can change tires in the dark?  Now place an inverter on it and power 112v items?  Yep were that crazy
Reply:wow, we really are putting the cart before the horse here aren't we? I would think that for simplicity and liability reason either 1) sticking with the set up you have, or 2) replacing the tractor with something that was meant to haul that trailer would be a much easier prospect. that's leaving the engineering, and liability of modifying said trailer to fit a Pintle hitch.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:Originally Posted by Black WolfIn terms of being competent to work on Class 8 Tractor Trailer units that run up and down public highways? Ummm.... No.  Not even close.  Since you refer to Monster Trucks as your "Credentials"  I have seen some high-end monster trucks up close and personal and some of the welding was enough to make me throw up on my mouth a little.  Same thing on stock cars.  Just because it holds doesn't mean you are doing it properly.I DO apologize if the above comment is offensive, such is truly NOT my intent, but building a Monster Truck does not "Qualify" you to do much of anything.I look forward to seeing how you go about your modifications - I have not worked with a "Coach" unit so it will be interesting to see how you deal with things.  Personally, with my background building and driving Class 8 Trucks in the oilpatch, I cannot see how you are going to eliminate the convertor dolly without overloading the drive axle and taking too much weight off the steering axle making the steering sketchy at best.It'll be fun to watch.Have a Good One.
Reply:The thing I would be worried about with getting rid of the dolly is puttng to much weight on the rear axle of the tractor. If I remember right on a truck on the interstate you can go 12,500 on your steer axle, 34,500 on your drives (which would include the dolly on yours), and 34,500 on your trailer axles. If you do away with the dolly axle You cut the amount of weight that can be on your drive axles because you anly have one axle in that area now. With a 5th wheel set up it is centered over the drive axles which allows enough of the load weight to be transferred to the steere axle. On a 5th wheel (Unless it is a fixed 5th wheel and cant move) you can slide it forward and backwards in approx 4" incriments which shifts 250lbs of load weight per incremint either forward or back according to the direction you move it. This would make about 750 lbs per foot of movement. If you relocate the place where the trailer hooks up from the 5th wheel over an axle to a pintle hook you are shifting the attaching point forward by several feet and removing an axle that the trailer hook up point is centered over. I may be wrong in my line of thinking but you would be over weight on your drives real quick.
Reply:bingo bhardy501, and thanks Thors I appreciate the thought.I suppose it is because the monster truck is taller/higher that we could not simply replace the trailer with one which would correctly support the load in the first place?  Or replace the semi with a double axle unit and a  slider 5th?  Either way problem solved and safe.  My good friend takes two modifieds and a lot of gear with him...It's a  5th wheel slider setup on a gorgeous F600 rig.. the 40 foot 5th wheel trailer has a small sleeper, kind of like a toybox.I look forward to seeing you in Yuma someday, we  get several monster truck events per year.  Very exciting, grandsons  like it a lot.Lincoln Power MIG 215Lincoln WeldPak 3200HDLincon ProCut 25Lincoln WeldanPower 225 AC/DCIf all else fails... buy more tools
Reply:My concern would be how to attach the tongue to the trailer. The trailers frame will be designed to put it's load on the point of the fifth wheel, it may not be strong enough after you extend the frame with the tongue. If you extended the whole frame out to the pintle, maybe, but it still may have never been designed for that much stress. I think you need real engineering on this one. Attached ImagesIan TannerKawasaki KX450 and many other fine tools
Reply:bhardy501:Thank you for the informative post   Your right except I have a single rear axle thus can only support 20k lbs on it.  If I had twins then yes you are right.  I actually did not know how much weight shifted during the incremental move.  This will be helpful when I come up with the actual length of the tongue.  I'll pass this to my engineer.PapaLion:This trailer can absolutely support the load.  In fact there were only a handful of purpose built trailers by Fetherlite for this industry (I know of 3)  The rest use converted commercial trailers such as this.  Even though they are rated to carry more they will never reach their rated capacity in their new life.  The 48' 102" wide single drop is typical, but the more desired trailers are triple drops.  Two truck teams utilize 53' trailers.  Some trailers even have living quarters in the front but you need a twin screw then to handle the weight.fortyonethirty:You hit the nail on the head with this.  With the upper deck being 10' we will bring the rectangular tubing the entire length as well as bringing a piece from the lower deck frame up to support it.  I will scan some hand drawn images tonight which should give you a better idea of the basic design.  Also as noted I do have an engineer working with me in the design as we are past the issue of the trailer being bale to handle this but on to the stress of the Freightliner frame where it was extended to make it into a coach.  Based on the engineering numbers we will need to box in at least 3 feet of this section of frame.  these numbers were just sent to me.Like everything we do, this will be built with overkill in mind.
Reply:In the pic. (I assume this is your rig) there is a dolly under the front of the trailer. When combined with the drive axle of the truck you should be at 34,500. When you remove the dolly from the equation then you drop to 20K gross axle weight. You are going to be shifting weight off of your steering axle and moving it backwards putting more weight on the drives and trailer axle. This in turn is going to make your truck pulling more than carrying it. Its easier to tote a load than drag it. I used to haul a lot of cotton out of West Texas, I always tried to get my load distributed to where I had the more toward the front (but not over legal limit). With my load shifted forward my truck pulled and handled better and got better fuel economy. I could tell if the load was trailer axle heavy it didnt pull as well or hadle as well.
Reply:Why dont you make truck twin screw 5wheel and use trailer as is? Proven and safe.
Reply:Originally Posted by Old DougWhy dont you make truck twin screw 5wheel and use trailer as is? Proven and safe.
Reply:Originally Posted by 1QuickSINo offensive at all.  In fact I agree 100%  However if you compare the welds on my truck to that, it is purely night and day.  This is not something I am just going to the shop to do on a weekend.  I do have a friend who is a mechanical/structural engineer and each piece of of the puzzle is being going over and over and over (we are 3 months into looking and piecing this together).  In terms of class 8 and on the road, a friend of mine is licensed to re-certify these vehicles for the road after a rebuild and he is also weighing in on his thoughts.  So as you can see I am just not throwing this together and heading down the road and doing this safely is paramount.  But I still like to get others input as when thinking out of the box like this more is always better.
Reply:I personally wouldn't be willing to touch this project with a ten foot pole, I would either extend the truck frame or stick with the dolly. 20k+ is a lot of weight on an extended frame pintle hitch.Dynasty 200DXPassport plus w/ spoolmate 100victor 315c oxy/(act and prop)Miller digital elitemilwaukee power toolsActually the tongue weight is roughly 7500 lbs.  We are at least 1500 lbs under the axles rated capacity fully loaded and well under the pintle hook rating.  Anyways here is a VERY rough scetch of the idea (I only do stick figures and even those are not very good).  My freind who is an engineer has a much better diagram with where each piece of tubing needs to go.  Tomorrow we will be putting all the final numbers into CAD and the frame calculator to see just where we are exactly and making sure the numbers on the paper jive with what the computer says.
Reply:I too am watching this with interest. I'm with everyone else on the geometry and its my opinion that the .125" wall tubing is way too light to begin with by halfThermal Arc Fabricator 2101970 Lincoln RedfaceMiller 150 STLStill need a Syncrowave and a plasma and a milling machine and a lathe and a bigger shop and a....
Reply:How high are you putting the pintle on the tractor? It seems to me that if you're trying to come off the raised deck you're going to be above the frame when the trailer gets to the tractor. It would seem to me that coming off the dropped section and creating some storage area under the raise portion would be better than coming off the raised area and having the pintle so high. not to mention reducing the materials used. because you'd just come straight back and have a couple pieces coming straight down off the front of the raised section. No need for the long diagonals from the front of the lower section to the front of the raise section. As the support for the raised section is already built in.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:Originally Posted by 1QuickSIActually the tongue weight is roughly 7500 lbs.  We are at least 1500 lbs under the axles rated capacity fully loaded and well under the pintle hook rating.
Reply:Canoe2fish You are absolutly correct and my typo.  The curent spec is 1/4 or .250 not .125ThorsHammerThe pintle in the coach is a the same hight as the deck of a standard non-drop trailer.  If you visualize a FedX tandom and where the dolly connects to the first trailer that is the hight.  It is already set.  There is a very minimal 4-6 inche drop necessary coming off the upper deck.DSW Based on CAT scales we know what each axle is currently holding and have calculated the approximate new weight with the addition/removal of material.  The pintle is roughly 3 feet from the rear axle.  The interior of the trailer was re-configured to optimize the tounge weight knowing we were coming close to its maximum rating.  We also have some ideas on how we can lessen it even more but waiting on what the computer tells us as until then everything is conjecture.Again this is not a throw together as 3 months of going back and forth with people like yourselves has given us what we think is a final design.  A few posts were rather informative and gave a little more insight (the more the better).  Tonight we will know for sure as it is all being entered in to a CAD program and placed on a frame calculator.  Once done we will have real number to work with and know if we need to make adjustments.
Reply:Have you considered bringing the support that comes from the front of the drop down all the way to the Pintle plate and doing some truss type support between it and the upper section? I would think you would end up with a stronger structure. Potentially reducing materila sizes making the added materials weight compairable to the current design.There are no problems. There are only solutions. It's your duty to determine the right one.Hobart Handler 210Airco 225 Amp MSM Stinger
Reply:My concern would be the leverage the long trailer would place on the frame extended behind the truck rear axle.  If it were me I would look at moving the truck rear axle as near to the back of the truck as possible.What comes to mind as most similar to what you are doing (long trailer, A frame hitch) is a mobile home hauler rig.  Typically they are also single axle with the rear axle as far back on the frame as possible."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Originally Posted by noriteMy concern would be the leverage the long trailer would place on the frame extended behind the truck rear axle.  If it were me I would look at moving the truck rear axle as near to the back of the truck as possible.What comes to mind as most similar to what you are doing (long trailer, A frame hitch) is a mobile home hauler rig.  Typically they are also single axle with the rear axle as far back on the frame as possible.