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My 4'x7' Trailer Build Thread

aka Larry

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What started this build was the purchase of my 2006 Mustang GT. I track my car at local HPDE events and I like to run DOT race tires for the awesome grip and extra fun they provide. Since the Mustang wheels are a good bit wider than the ones on my old Z-24, they are not even close to fitting on my my old tire trailer. It was time to either buy or build a new and bigger one.

After a lot of searching, I finally concluded it would be better to build my own trailer. Anything I would have bought would have needed to be modified for my purpose anyway, and besides, a lot of the parts I had could be re-used. I determined I could re-use the wheels, tires, hubs, bearings, toolbox, leaf springs, spring hangers, axle mounting plates and u-bolts. I started a spreadsheet to track all the costs involved and to have a source to go back and locate the various parts I may need later.

Next was the design. I wanted to be able to use this new trailer for trips to Lowes to haul stuff when needed. After a few days of tweaking the design, I came up with a plan. Once I had all the data, I made the drawings and started ordering parts, the first of which was the steel for the basic frame which is 2"x2”x3/16" thk angle. The same size material will be used to form the perimeter railing which is more for overall rigidity than anything else. I also picked up the material for the tongue (2-1/2" square tube) and the axle (1-1/2" square tube) from another local steel fabricator.

Below are the pics and notes from the fabrication:

First up was to cut all the members to length with the bandsaw. Here you can see one of the miter cuts in progress. All four corners were mitered. BTW, Pennzoil 10W-30 will work as a cutting lubricant just fine in a pinch. :)


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The members that are used as cross braces need to be notched so the flanges will fit flush to form and even surface for the decking material. I did all of these with the band saw also to make a nice clean cut.


P1020879.jpg




Since this material is 3/16" thick, I needed to bevel the edges to ensure full penetration of the welds.



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I’m a planner and some pre-planning is always a good thing. Here I'm making a 1/2" hole in the cross members to run the wiring to the rear tail lights.



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If you don't have a set of Rotabroaches...get a set! These things rock and make a drill bit seem obsolete. Do they make a pretty hole or what? Fast too!



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Here I'm using clamps, a jig, and a level to make sure the whole thing is square.




P1020886.jpg



The outer perimeter of the frame is complete.


P1020888.jpg




Remember those notches? Here I've clamped the cross braces in place for a flush fit on the top side of the angle. Without the notches this would not be possible.



P1020889.jpg




The main frame is now fully welded and complete.



P1020890.jpg



Without the railing, the perimeter 2"x2" angle members aren't rigid enough to keep the frame from "racking". I used jack stands and shims to get it all square before welding on the railing to stiffen it all up.




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Here the railing is all finished.



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One thing I didn't really account for was the weight of all the steel. Yes, I knew how heavy it would be in the end, but until it's a roller it's all dead weight that needs to be moved around. Luckily I bought a small yard kart last year to use around the yard to haul stuff too heavy for wheel barrow. I spaced out a couple pieces of 1" square tubing and sat the entire assembly onto the kart. The kart made it easy as pie to roll outside where it sits now under a tarp waiting for the next round of fabrication.




P1020897.jpg
 
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aka Larry

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I disassembled the my old HF trailer to scavenge the wheels, tires, hubs, leaf springs, spring hangers, fenders, and toolbox.


Here is one of the spindles inserted into the axle tube ready to be welded. The tape is to keep weld spatter off the machined surface (where the bearing will go), as well as to mask it for painting.


P1050022.jpg





After the spindles were welded in place, I cleaned the axle assembly so it was ready to be primed and painted. I used the Dupli-color self-etching primer on the bare metal then used Dupli-color low gloss black engine enamel for the top coat. You can see the freshly painted leaf springs in the shot also.



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Locating the spring hangers


P1050027.jpg




Front spring hanger is clamped in place ready for welding


P1050028.jpg




Hanger is welded


P1050029.jpg




All the spring hangers are in welded in place


P1050030.jpg



Springs are bolted to the hangers and are ready for the axle


P1050031.jpg




The axle is bolted to the springs and the suspension is done


P1050033.jpg




Here I'm triangulating the axle to the tongue. Sorry about the dark pic.


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Ok, time for a little tongue action. Once it is square with the axle, I clamped and then welded the tongue in place.


P1050036.jpg




Here I'm adding reinforcement to the tongue


P1050037.jpg




With the tongue fully welded it's time to add the coupler. I removed the zinc coating in the areas to be welded and clamped it in place


P1050038.jpg




I did a couple of stitch welds on the under side and then used rosette welds in the four holes on the sides.


P1050039.jpg
 
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aka Larry

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To make sure none of the wires will be hanging, and without drilling unsightly holes for using a zip-ties, I tack-welded four washers in place along the rear frame.



P1050041.jpg




Here I've pre-drilled the holes to mount one pair of the new LED tail lights.



P1050042.jpg




Hubs are bolted in place ready for the wheels



P1050047.jpg




Wheels are finally on.


P1050048.jpg




Finally it's a roller!



P1050049.jpg


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Since one of the main reasons to build this trailer was to haul my tires, I worked on the tire rack next. This is made from 1” square tubing and will be bolted to the trailer deck so it can be removed for hauling other stuff.


After cutting all the angles on the bandsaw, here you can see I’m jigging up the pieces on the workbench using magnets and tape as guides.


P1020899.jpg



P1020900.jpg




Here the members have been tacked in place and allowed to cool before final welding to prevent warping.


P1020901.jpg




Final welding is done. The **** welds on the tubing now need to be ground flush for a finished look, but I ran out of time.


P1020902.jpg



Foot plates will be welded to the bottom of tubes also, but I didn’t have any flat bar at the time.


I ground all the **** welds flush first, and then drilled holes and cut flat bar for the foot plates.


Here I’m setting up a jig to keep the plate spacing equal before welding.


P1050055.jpg




After the foot plates were welded in place, I tested the height with two of the Mustang race wheels


P1050057.jpg




In this side view you can see how the aluminum rod slides through the end pieces to keep the tires in place. There will be a plate added to the ends to keep the rod at the right height (so the wheels don’t bounce up and down) once it’s installed on the trailer. Also there will be a plate welded on one end (so the rod doesn’t pass right through) and a lock on the other just like my old tire trailer had. In addition there will be two tubes added between the ends to make the whole thing one removable assembly.



P1050056.jpg




Time to connect the sides together with the two cross members. When you are working by yourself you have to be creative with jigs, clamps, magnets, or whatever to hold stuff in place for tack welding. Here's how I arranged the clamps and magnets:



P1050060.jpg



P1050059.jpg




All the welding is done and assembly is complete. It will be easy to swap on and off the trailer as needed since it weighs less than 10 lbs.



P1050061.jpg




Time for some paint! I cleaned all the bare metal with laquer thinner and primed it with Dupli-color Self-Etching primer. For the top coat I used Dupli-color Engine Enamel in Low-Gloss black. Here are the in-process painting pics.


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Next I worked on the wiring. This is another one of those tasks that seem quick and easy, but take forever. I opted to solder and heat-shrink all the connections, which at least doubled the time it took to hook everything up.


Installing one pair of the LED tail lights.


P1050075.jpg





The right side pair is done.


P1050076.jpg




Rubber grommets are used for a neat appearance as well as to protect wire chaffing


P1050077.jpg




Installing one of the five LED strip lights.


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Here you can see the LED strips are almost invisible against the black trailer in the day time.


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To route the wiring harness through the hollow tongue I'm using compressed air to blow a string down the tube.


P1050080.jpg




Once the string is through, I tied it to the wiring harness and pulled it down the tube.


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After a lot of soldering and heat-shrink, the wiring is done


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Once the sun went down it was time to see the LEDs in all their glory. Yes, I love lights!


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For the flooring I decided to use 5/4” pressure treated decking boards secured with self-tapping screws


P1050134.jpg



Here I added metal sleeves through the wood. The tire rack bolts to the nuts welded underneath.


P1050135.jpg



The way the toolbox was mounted on my old trailer previously (with inadequate support) plus lots of bumps over lots of miles, the floor of the aluminum toolbox was damaged.


P1050137.jpg





Here I'm reusing some old diamond-plate from the old trailer to reinforce the floor of the toolbox.


P1050138.jpg





This aluminum diamond-plate is at least twice as thick as the toolbox so I secured it to the bottom with sheet metal screws.


P1050139.jpg





Since the toolbox was home to the trailer's tail/brake lights before, I had to plug the holes in the toolbox. Again I reused some of the old diamond-plate. I cut the pieces with a jig-saw and pop-riveted them in place. They are also sealed with RTV to prevent leaks.


P1050140.jpg





Here I positioned the box at the front of the trailer and marked it with tape. I attached it with bolts and nylon lock nuts to the trailer floor.


P1050141.jpg





The toolbox and tire rack are now both in place. You can see I used aluminum end plates to locate the rod through the wheel so they don't bounce around.


P1050143.jpg





Stick a fork in it...it's done!


P1050142.jpg
 

Piper

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that trailer looks great! Ditto on the thank for posting! Question for you, did you feel that your welder had enough umph to carry you thru the project? I've got the Lincoln 140C which is very similar to yours. Just wondering about penetration and your thoughts regarding building a trailer. I feel pretty comfortable with my welder for 1/8" material and maybe 3/16" but honestly I think the 3/16" is pushing it a bit. I'd be interested to hear your thoughts.
 
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aka Larry

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that trailer looks great! Ditto on the thank for posting! Question for you, did you feel that your welder had enough umph to carry you thru the project? I've got the Lincoln 140C which is very similar to yours. Just wondering about penetration and your thoughts regarding building a trailer. I feel pretty comfortable with my welder for 1/8" material and maybe 3/16" but honestly I think the 3/16" is pushing it a bit. I'd be interested to hear your thoughts.

As I noted, I beveled the edges of the 3/16" material before welding. However, with it turned all the way up, I think my Lincoln 140A works just fine on 3/16" thk material.

My little Lincoln works great for most everthing I do, but I do plan to get a 220V welder in my new shop though...if I can ever get the damn thing built!
 

DCarr

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453
Good job and Thanks for all the pics !

A friend and I are always picking up or moving Bridgeports, Lathes or other heavy machines w/ small footprints and I am thinking of building a smaller ( than a car hauler ) heavt duty trailer with tandem axles to make transporting them easier.
 

theoldwizard1

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A couple of questions

  1. Did you weigh it when you were done ?
  2. What is the load rating on the axle/spring/tires ?
  3. Just from the pictures and what you plan on hauling (at least most of the time) don't you think 1/8" steel would have been adequate ?
 

SteelArt

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Cool build great to see something coming togeather.

One quick point for you if I may. You have actually welded your spring hangers on the worse way possible and if you get the chance to build another make sure you put the weld down the side not across the chassis rail as such.

Think of a weld bead like an angle grinder cut path, by doing it the way you have got the fatigue are is in a bad place.

This is the one I am talking about

P1050029.jpg
 
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aka Larry

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Thanks for the kind words everyone.

Nicely done. Can we see it now behind the tow vehicle ?

Actually I do need to get a picture of that! I'm headed to the track this weekend so I should be able to get one before I leave.

In the meantime here's my other trailer and tow vehicle :shocking:

P1050315.jpg


P1050316.jpg
 
OP
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aka Larry

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A couple of questions

  1. Did you weigh it when you were done ?
  2. What is the load rating on the axle/spring/tires ?
  3. Just from the pictures and what you plan on hauling (at least most of the time) don't you think 1/8" steel would have been adequate ?


I did not weigh it, but I need to just for reference.

The axle / spring combo is rated for approx. 1200 lbs IIRC

1/8" steel would probably have worked just fine, but I do like to overbuild things.



very nice write-up. Not counting the used parts what was your cost for material?


Not counting all the bling lighting, I think I had about $700 in materials. A lot of that was using the rattle can paint, which I wouldn't do again. At least 50% if not more was wasted with overspray.
 

koditten

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Cool build great to see something coming togeather.

One quick point for you if I may. You have actually welded your spring hangers on the worse way possible and if you get the chance to build another make sure you put the weld down the side not across the chassis rail as such.

Think of a weld bead like an angle grinder cut path, by doing it the way you have got the fatigue are is in a bad place.

This is the one I am talking about

P1050029.jpg

Disagree.

There is nothing wrong with the position of this weld. The strength of the frame is not comprimised in this fashion.

Putting welds on the other sides will cause the trailer frame to look as if it is sagging. With 4 long welds(2 on front hanger,2on rear hangar), you actually shrink the metal as the weld cools and arc the frame. This makes a brand new trailer look like it was overloaded at some time. When you work with mild steel, shrinkage will be a big factor in how things look. I did this many times before I figured out what I was doing wrong.

Secondly, welding in front and rear of the hanger is just easier than do than welding the sides of the hanger.

Lastly, if you have decided you need to reposition the axle because the trailer is not balanced to your satisfation, it is a hell of a lot easier to cut these welds to remove the hanger.

KO
 

Kevin54

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Nice trailer for sure. That should last for years and years.

One question...is there a reason that you went with 4x7 instead of 4x8? At least if it was 4 x 8, you could carry drywall, plywood or whatever without anything hanging over
 
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aka Larry

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One question...is there a reason that you went with 4x7 instead of 4x8? At least if it was 4 x 8, you could carry drywall, plywood or whatever without anything hanging over

As strange as it may sound, yes, I actually wanted it as small as possible to haul what I mainly wanted it for, which is the stuff I take to the track. The extra part behind the tire rack was added for a future project I plan to build.

You should have seen the look on the guy's face at Lowes when I asked him to load 20 bags of mulch and I pulled up with this trailer behind my Miata. He said he had never seen a Miata pulling a trailer before.

So thus far I have hauled mulch with it, but no lumber or plywood sheets yet.
 

SteelArt

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Disagree.

There is nothing wrong with the position of this weld. The strength of the frame is not comprimised in this fashion.

Putting welds on the other sides will cause the trailer frame to look as if it is sagging. With 4 long welds(2 on front hanger,2on rear hangar), you actually shrink the metal as the weld cools and arc the frame. This makes a brand new trailer look like it was overloaded at some time. When you work with mild steel, shrinkage will be a big factor in how things look. I did this many times before I figured out what I was doing wrong.

Secondly, welding in front and rear of the hanger is just easier than do than welding the sides of the hanger.

Lastly, if you have decided you need to reposition the axle because the trailer is not balanced to your satisfation, it is a hell of a lot easier to cut these welds to remove the hanger.

KO

No probs it is your build, but I must admit I have never considered look and ease or removal when fabrication something such as a trailer chassis
 

GreyOwl

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How much wear will you have on the wiring running through the washers? I have always used lengths of 1/2" emt conduit welded to the frame for wire protection and not having wiring sagging between attachment points.
Great looking trailer and really like the lighting.
 

Mmfh

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One thing I'd like to know, how do you know where to put the axle? How did you figure out where to put the spring shackles? Did you look at another trailer for a sample?

Mm
 

evildky

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I'm an autocrosser, I've seen more miatas with trailers than you can shake a stick at

you see guys, the miata is a great driver oriented car with the potential to be raced in many venues, unfortunately it does nto have the space for much of anything, so you either get a tow vehicle or you tow a trailer with your race rubber, jack, air can etc
 

V-10 Killer

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Very nice job on the trailer, but I have a question on your tire rack. Have you thought about putting some type of anti-scuff protection along the sides between the face of the rim and the tire rack? I'd hate to see you turn a corner and have the tire slide sideways and ding the rims.
 

tpwalsh

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Nice work.
I have to agree with the guy at Lowes, that is the first time I have seen a Miata tow vehicle.

Very nice work. Yep, Miatas pull little trailers all the time. Friend of mine used his Harbor Freight trailer/miata to move a couch or 3 during his last move.

Here's my 40x48 trailer when it was in tire trailer mode. Worked great to support 2 people for a long weekend away from home in the Miata.
main.php



It's now been converted to a kart trailer.
main.php


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aka Larry

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One thing I'd like to know, how do you know where to put the axle? How did you figure out where to put the spring shackles? Did you look at another trailer for a sample?


From my research a 'basic' rule of thumb for reasonable tongue weight is the axle is 1" per foot behind the center of the bed. 8' trailer would have the axle 8" aft of the center of the bed.

Actually I found an online Excel spreadsheet that allows you to put in how much load you plan to put where on the trailer and you can adjust the weight on the tongue by moving the axle, lengthening the tongue, or shifting the load. PM me if you would like me to send it to you.


How much wear will you have on the wiring running through the washers? I have always used lengths of 1/2" emt conduit welded to the frame for wire protection and not having wiring sagging between attachment points.


Actually the wires are held up by the the washers, but they are all zip-tied to them as well so the wires don't really move or sag.


Very nice job on the trailer, but I have a question on your tire rack. Have you thought about putting some type of anti-scuff protection along the sides between the face of the rim and the tire rack? I'd hate to see you turn a corner and have the tire slide sideways and ding the rims.


The rack is actually about 4" wider than the wheels so the face of the wheels are never close. Besides, I usually load them with the wheel faces inward, not like that pic. Also I strap the wheels together and friction keeps them from contacting the sides of the rack. I've been using it for almost a year now with no issues.

How many hours do you have in the project?

Damn, I'd hate to guess! I'm a slow poke so it probably took me twice as long as it would anyone else. Also having to work off the garage floor vs. a nice welding table didn't help either.

I actually didn't really save any money in this case building it myself, but it was built better than most pre-built ones so I have the piece of mind knowing it was built right.
 

Mmfh

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From my research a 'basic' rule of thumb for reasonable tongue weight is the axle is 1" per foot behind the center of the bed. 8' trailer would have the axle 8" aft of the center of the bed.

Actually I found an online Excel spreadsheet that allows you to put in how much load you plan to put where on the trailer and you can adjust the weight on the tongue by moving the axle, lengthening the tongue, or shifting the load. PM me if you would like me to send it to you.

Thank you for that info. That's a rule of thumb I will carry with me. I have a converted travel trailer that doesn't feel that good when loaded with a car. I'll check to see where the axle is compared to the rule of thumb.

Thank You!

Mm
 

Journaler

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I actually didn't really save any money in this case building it myself, but it was built better than most pre-built ones so I have the piece of mind knowing it was built right.

That is the #1 reason to do things yourself (if you know how).
 

iron_worker

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Mar 15, 2011
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Is it standard practice on small trailers to use leaf springs that are solid mounted on both ends? On cars/trucks the leafs are mounted on directly to the frame on one end and to a shackle on the other to allow the spring to flatten out as it's compressed and vice versa.

Or maybe I missed something? ha

IW
 
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aka Larry

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Is it standard practice on small trailers to use leaf springs that are solid mounted on both ends? On cars/trucks the leafs are mounted on directly to the frame on one end and to a shackle on the other to allow the spring to flatten out as it's compressed and vice versa.

Or maybe I missed something? ha

IW

Take a look at this pic:


P1050033.jpg


The left side is fixed, but the right side is allowed to flex over the bolt. It's a called a 'slipper spring' and used on some light duty trailers like mine.
 

musgofasta

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Corona CA
I've been reading this wondering how you intended to fit your track car ON a 4x7 trailer...but this is even better.

I'm sure the Lowes guy went back to his buddies and wondered aloud if you were even going to make it home with that much mulch!
 

koditten

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Im glad im not the only one recycling my posts. I really enjoyed this again. Thanks, Larry. By the way, your shop is way, to organized. Im jealous.

Kirk
 
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