Building A Race Car Trailer Part 1

Sometimes we bucks-down racers spend all our money on the race car andthen have to borrow a trailer to get it to the track. This is an all toofamiliar scenario, so I sat down to devise a simple open trailer thatwill safely transport my beloved car at an economical cost. In thisfirst article, we'll cover the basic construction of the frame andrunning gear.

GETTING STARTED

The guidelines called for a 16-foot-long bed with adovetail rear to lessen the need for long or steep ramps. The objectivewas an open bed with runners on each side, because often I don't unloadthe car to change the oil and check for loose bolts. With this setup,you can also lie under the trailer and scan the bottom side of the carfor damage.

It is my belief that a trailer needs springs, two axles, andbrakes, although many are built without them. Keeping cost in mind,mobile-home axles work very well. In many parts of the country, they areabundant, but you should check with local agencies to make sure they arelegal to use in other applications. Several states have laws to theeffect that a mobile-home axle can be used only for its intended purposeon a mobile home. Most often, mobile-home axles are left intact by theinstallers.

The axles on this trailer were obtained by crawling under afriend's mobile home and cutting them out--with his permission, ofcourse. All the mobile-home axles I've encountered have a capacity of6,000 pounds or greater and have matching springs. That's 12,000 poundsof capacity for two axles, more than enough for a 3,000-pound car on a1,100-pound trailer. In choosing mobile-home axles, you will find somewith brakes. Get at least one of these if possible. You'll be glad youdid if you find yourself in a tight spot.

Next, find five 14 1/2-inchmobile-home tires and wheels (one for a spare). The tires are made ofbias-ply nylon for trailers. Their load capacity is greater than 15-inchsteel-belted radials, and they tow better, according to those who know.If your budget allows and you feel you must have 15-inch wheels, tandemaxle assemblies with springs and brakes are available from severalsources. There should be at least one trailer-axle dealer in your area.Be prepared to spend $350-plus for a pair of 2,500-pound axles (more forheavier ones), and then put on some good used tires.

In many cases, themobile-home trailer tongues are also underneath. If you don't mind usinga 2 5/16-inch ball, one of these can be made to work. That will save afew more bucks. I like high, forward-mounted brake lights andtaillights. The lights on this trailer are up high on the tire rack.They are visible from any angle and don't get knocked off, a constantproblem when mounted low and at the rear. It's a good idea to usereflective tape on the rear of the trailer. In Texas, where this buildupwas done, there has never been a problem with this arrangement. If thegendarmes in your area are more critical, add some lights at the rear,protecting them as best you can.

Some tools and equipment will be neededfor construction. A cutting torch, a 14-inch cutoff saw, and a welderare the basic items. A hand-held angle grinder will let you clean up alot of rough edges, too. You will need excellent welding skills. If youdoubt yours, hire the welding out.

A list of materials needed toconstruct the trailer appears with this article. There may also be a fewpieces of scrap in your shop you can use. Now let's build it.

THE AXLES

For our purposes, the outside width of the trailer is 98inches. This allows a bed width of 78 inches with a tire clearance of atleast 1 inch. Mobile-home axles are too long in the beginning, andnotice the crown in the center of the axle. This flattens out with theweight of the mobile home. Cut out this section to achieve the properoverall width. With this accomplished and the ends rewelded, the axleshould be straight. Weld it back together after grinding a bevel on bothends. This will aid in weld penetration. Before you weld the axle backtogether, don't forget to align the spring pads with each other. I used0.030 wire in the Millermatic (see sidebar) for this entire project. Imade two weld passes around the axle to fill the bevel and leaving abuilt-up bead.

Using the piece removed from the center of an axle, maketwo 8-inch, half-round pieces. One of these was welded to the bottom ofeach axle joint for additional strength.

Remove the springs and turnthem over so the spring will be below the axle. This will lower thetrailer about 31/2 inches. Hopefully you found axles with the shacklesand pivots to make it easier. The axles are finished for now.

FABRICATING THE FRAME

The perimeter frame is made of 4x4x1/4-inch steelangle on the sides and front. The pieces are cut to make outsidemeasurements of 16 feet by 78 inches. Cut the corners at a 45-degreeangle so they fit together smoothly. A piece of 4-inch channel forms therear-most crossmember. It is installed flanges-out.

The frame will bebuilt upside down so there won't be any overhead welding. Set theframerails flange-down on cinder blocks. This gets them off the floor.Measure corner to corner in an X pattern. Tap the pieces around untilthis measurement is equal both ways. Now the frame is square. Put a goodtack weld in all four corners before welding it solid. Check thecorner-to-corner measurement again. If it is off a little, rap it with ahammer.

Cut seven pieces of 11/2-inch square tubing to 771/2 inches tofit inside the frame. The inside of the 4-inch angle, as with all angleiron, has a radius. The tubing can be cut straight and then radiused ona grinder for a good fit. Willing to take a short cut, I cut the tubingto 77.25 inches and did not grind a radius. The Millermatic sewed up thegap like Betsy Ross putting stars on a flag. Notice the photo showingthe locations of the square-tube crossbars. The center crossbar is onthe centerline between the two axles. This should be 18 inches behindthe center of the trailer bed. The next two are away from the centerunder the mounting points of the spring hangers. One more should beplaced halfway between the front spring mount and the front of theframe. In the rear, 40 inches from the rear would be about right.

Nowthat the basic frame is together, it must be notched for the dovetail.The dovetail is the drooped section at the rear of the trailer. Thisenables the use of shorter ramps. The dovetail line should be 48 inchesfrom the rear end of the trailer. There needs to be a drop of 6 inchesmeasured at the rear. Using the torch, cut the vertical flange of the4-inch angle 48 inches from the rear. Remember, the frame is stillupside down. I placed two jackstands 6 inches higher than the cinderblocks under the rear channel. Standing on each side of the frame at thenotch, my weight bent it down properly.

From scrap, cut a diamond-shapedpiece 4x7x1/4 inches thick. Place it on the outside of the frame overthe notch. Weld it inside and out. The remaining piece of 4-inch channelshould be cut in half. The two resulting pieces will make the tongue. Bythis time, you should have selected a hitch. Some are made at differentangles. The tongue sides should be at the correct angle for your hitch.Consider it a minimum to have 36 inches from the front of the trailer tothe center of the trailer hitch ball. More would be better. Some goodwelds here will give you peace of mind for a long time. With the basicframe done, set the axles on the frame and hook up the spring linkage.Place a 2-inch block between the axle and the frame to set thebump-travel limits.

Measuring carefully, align the axles parallel toeach other and square to the trailer frame. Weld the spring hangers inplace. Next, the axles must be removed so the frame can be turned overmore easily. Turning the frame over is an operation that requires greatcare. Use an engine hoist to raise one side of the frame to about a70-degree angle. At this point, attach safety chains to heavy objects onboth sides of the frame.

I used the rollcage of our race car for oneattachment point. The other chain ran from the trailer frame to thetrailer hitch on the tow vehicle. Step by step, I let one out andtightened the other. It gets a bit dicey when the frame goes over-centerand the tension goes from one chain to the other. Keep yourself out fromunder the side coming down. Use the engine hoist for the final loweringjust like the initial pickup. If you don't, the frame will skid sidewaysduring the last few feet of lowering. This sort of surprise will makeyou wish you had taken those dancing lessons when you were young. See below for the photos where the frame is flipped over

Withthe trailer right-side up, weld all those places that will be covered upby the purling before you forget.

THE RUNNERS

Two 8-inch purlings need to be cut to fit on each side. Thismakes a 16-inch-wide runner. Purling is commonly available from metalbuilding suppliers. It is roll-formed from sheetmetal in the shape of a"C." Measure inside the frame from front to rear and add 1/4 inch to thetotal. You will have to cut a V notch for the dovetail to take up thedifference. This V notch should be 5/16 inch wide at the flange side andnear zero at the top face. When bent, it will fit right down in theframe. Weld the first purling in next to the outside of the angleflange. Weld it to the angle flange and also to the 11/2-inch squarecrossmembers. Then add the next purling, welding it to the first purlingand to the crossmembers. Depending on your purling supplier, it mightstick up slightly over the angle. Mine did, so I got some 3/4-inch angleto cap it off at the front.

The purling can be slippery at times. Mycure for this is to rake it with the welder. Medium amperage and amedium wire feed works well. This leaves small weld beads similar tovery coarse sanding paper stuck to the surface. Foot traction is muchbetter than it is with diamond plate, and it's a lot cheaper.

At thispoint, your trailer should look like a trailer. Next month I will showyou how to build a pair of $12 fenders, a slide-in Superwinch mount, anda tire rack with a deck. We will also be mounting the M&R tie-downs. AndI won't forget to show you the lightweight, swing-away ramps that stayattached to the trailer. Have fun building. Contact Sleepy at:sleepy.gomez@ primedia.com.

RIGHT WELDERLet's take a moment to talk about the welder. I have built several racecars with a 110-volt, 130-amp wire-feed welder. This unit is notrecommended here because the duty cycle is too short in the range youneed. You'll spend too much time waiting for the welder to reset. An arcwelder can handle parts of this project, but some of it will still be aproblem.

The solution turned out to be a Millermatic 185 welder. It is awire-feed, or MIG-type welder. It can be turned up high enough to weldthe axles back together and low enough for the 0.065-inch-thick runners.You can use 0.023-, 0.030-, or 0.035-inch wire and control it properly.Don't let the 220-volt current bother you. An extension cord can be madeeasily from hardware store parts. It can be plugged into the dryerconnection at your home if necessary. The Millermatic 185 will performall the welding chores necessary on this trailer. It will do just aboutevery welding chore in your shop, too. With the optional spool gun, youcan weld aluminum for race car seats and other parts. Since it is builtfor industrial use, this welder will last forever. If you fabricatemetal in your shop, the Millermatic 185 could be the best investment youever made.

The Millermatic needs to have a shielding gas for the bestwelds, as do all similar welders. Flux-core wire is available and isused outside in the wind, but it is more expensive than plain weldingwire. I'm told a flux-core wire weld has less impact resistance thanshielded gas welds. For a shielding gas, carbon dioxide or carbondioxide plus argon can be used. For the best welds, always use thecarbon dioxide/argon mix. Selecting a wire speed and weld heat is a bitsubjective. The video and print instructions that Miller went to greatlengths to produce are invaluable tools for getting started. Afterreading the book and watching the accompanying video, I removed thewelder from its box and ran the first weld 23 minutes later.

MATERIALS LIST

*4x 2 1/2-inch channel; one 20-foot piece; tongue, rear crossframe

*4x4x1/4-inch angle; two 20-foot pieces; main frame, sides and front

*11/2x11/2x1/8-inch angle; one 20-foot piece; ramps, battery box, etc.

*8-inch purling; five 20-foot pieces; runners, ramps, fenders

*11/2x11/2-inch, 11-gauge square tubing; five 20-foot pieces;crossmembers, tire rack sides

*1x1-inch, 11-gauge; two 20-foot pieces;fender mounts, tire-rack crossbars square tubing

*Cost of materials other than wheels, tires, and axles was $306 atEagle National Steel, Hutchins, Texas. This price may have increasedsince publication.

For Parts 2 & 3 of "Building A Race Car Trailer" click links below:

Building A Race Car Trailer Part 2

Building A Race Car Trailer Part 3