Bike Trailer

8/6/2019 Bike Trailer

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Chap te r 12

FreighterT HIS TOUGH, LIGHTWEIGHT BICYCLE TRAILER ISideal for hauling groceries and laundry (Fig. 12-1).It is strong enough for the heavier stuff: bundles ofnewspapers, furniture, and loaded garbage cans (Fig.12-2), It can take up to 100 kg (222 pounds) withregular 20-inch bicycle wheels. The load limit can beupped to an amazing 150 kg (333 pounds) withmotorcross-type 20-inch wheels.

The secret to such strength is a steel frame that isSUrprisinglyeasy to bui ld, even in a home shop (seeTable 12-1). Variations of this same metal bed can beUsed to build any number of strong, versatile carts forvarious uses.

B E N D I N G T H E S T E E L F R A M EThe cart's undercarriage is fashioned from three 10-footlengths of EMT conduit (electrical metallic tubing).This lightweight pipe is available inexpensively athardware stores and comes pregalvanized, so it wil lneed no extra finish. The EMT is easily bent by handW i t h anelectric ian's pipe bender, a tool with a curvedmetal head that's screwed onto a pipe handle. Al-though this tool only costs about $20, you may preferto borrow one for the few minutes you'll need it.

The first step isto bend two lengths of :V4-inchpipeto form the part of the frame that supports the box andalso curves upto form the tongue. Mark both pipes asin Fig. 12-3 for the starts of the three bends. Cut thepipes with a hacksaw or pipe cutter at 228 cm (7%feet). For the first bend, line up the arrow on the pipebender (this arrow indicates the start of the bend) withthe mark 13 cm ( 5Va inches) from the end of the con-duit. With one foot on the bender, bring the handledown to make a gO-degree bend-as checked againsta door frame or square (Fig, 12-4).

Turn the bender around for bend B, so you'll bebending the pipe toward bend A. Make this secondbend at almost a right angle to the first. I 've found theeasiest way to dothis isto put my foot on the first bend,with the tip of the pipe blocked slightly off the floor by ascrap of V4-inch plywood, and then make the secondbend perfectly vertical, raising the far end of the con-duit up in the air until it's about 80 degrees from thefloor.

For bend C, the final bend, hold the conduit intheposition it wil l have when it's in the cart. Turn the pipebender upside down, with the end of its handle on thefloor and the arrow onthe head matched with the third

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.;"Fig. 12-2. Large loads t ie down easily to the bumpers of this tough bicycle cart.

mark on the conduit, as in Fig, 12-5, Remember thatthe two sides of the cart's tongue have to come to-gether at the hitch, so aim the bender slightly towardwhat will bethe center. Bend the end ofthe pipe downuntil it's level withthe floor whenthe restof the frame islevel.Because the second half of this frame is a mirrorimage ofthe first: you'll make all the bends inthe sameplaces, 8e sure the end of the conduit faces the oppo-site direction when you make bends 8 and C.Don't worry ifthe bends aren't perfect; you can stillbend them a little bit either way by hand, To checkthem, join the two pipes with an EMT coupling andseparate the two sides of the frame with a spacerbar-a wood scrap exactly 53,3 cm (21 inches) long.The tips of the pipes that will be the cart's tongueshould almost touch, centered 58 cm (23 inches) offthe floor when the frame is resting on the ground.To finish the tongue, take the two frame halvesapart. Pound the front ends of the pipes flat so they fit

Fig, 12-1. The Freighter.

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T ab le 1 2- 1. F re i& ht er M a te ria ls .Lum ber1 4' x 8' sheet exterior y," plywood4' 1 x 3 lumber (for molding) or

14' 1 x 1 moldingB ik e S ho p2 20" x 1.75 front wheels2 reflectors

Hardware4 washers (for wheel axles)some scraps of 26-gauge sheet metalsome *" wood screws and short nai lst ire sidewall or neoprene (for hitch)B olt ed F ra m e3 10' lenglhs of :;'4" EMT pipe2 * " EMT couplings4 4" x 4" square electrical boxcovers (without "knockouts")5 1/4" X 2" bolls8 V 4 " x 1W' bolts

1 V4 " wing nut4 1W' sheet metal screws with washersW eld ed o r B raz ed F ram e2 10' lengths of :;'4" EMT pipe1 10' lenglh of V 2 " EMT pipe1 each, * " and W' EMT couplings4 4" x 4" square electrical boxcovers (without "knockouts")1 y." x 2" bolt with wing nut4 1" sheet metal screws with washers

together for the hitch (Fig. 12-6). This will create sharpsquare corners that have to be removed, either bybendingthe t ips of the corners aside with pliers or bygrinding them round, so they won't cause wear on therubberconnector. Dril l8-mm (5/16-inch) holes for thehitch about 2 cm (%-inch) from the tips of each half ofthe tongue. Fasten them together with a V4-inch x2-inch carriage bolt and wing nut (Fig. 12-7).

BE ND IN G THE BU MP ER SThe wheel housing is nothing more than a piece of4-inchconduit bent into a rectangle. Ifyou plan toweldth e frame instead of bolting it, you can use V2-inchEMTand save almost a kilo (2 pounds) from the cart'sweight.

In either case mark for the four bends as in Fig.12-3 and cut the pipe at 266.5 cm (8 feet 9 inches).Lineupthe arrow on the bender with your marks on thepipe,make each of the four bends in the same direc-tion, and all to just 90 degrees. The final bend shouldbringthe ends of the pipe to touch, where they can be

joined with an EMT coupling. Check the inside dimen-sion of the rectangle against Fig. 12-3 and set the pipeaside while you make some axle plates to attach thewheels to the frame.A X LE P LA TE S

You' ll find the material for these plates with the otherelectr ical supplies at the hardware store. They're 4-inch x 4-inch square conduit box covers. Get the oneswithout "knockouts" for holes inthe center (Fig. 12-8).Avoid Steel City brand (they won't bend). Most plateshave lit tle slots in the corners for screws, but you caneasily clip these off with tin snips or a hacksaw.Cut slots in the plates for the axles. Make theseslots 4 cm or 1V2 inches long for bolted frames and 6.5cm or 2V 2 inches long for welded or brazed frames. Tocut them out, dril l a t-ern (3/a-inch)hole in each plate.Saw down to the hole on either side of the slot (Fig.12-9).For bolted frames only, clamp the edge of theplate in a vise against a piece of 4-inch conduit. Bendthe plate over the pipe with the palm of your hand untilit curls snugly three-quarters of the way around thepipe (Fig. 12-10). Repeat for all four plates.Ifyou're planning on welding or brazing the plateson, bend them dif ferently. For the inside axle plates,clamp 3 mm (V a inch) of the edge of the plate in a viseso the slot is pointing up. Bend the plate over to a45-degree angle. For the outside units, clamp 15 mm

( 5 ! 8 inch) of the edge in the vise and bend them all theway over to a gO-degree angle (Fig. 12-11).G E TTIN G THE FR AME TO G ETHE R

To clamp things down for welding or bolting, it'seasiest to layout the main part of the frame upsidedown on a table. Position the wheel housing on top (itwill be on the bottom of the finished undercarriage).Center it front to back and check that the gaps for thewheels are the same on either side, but not less than8.5 cm (3V2 inches) nor more than 10 cm (4 incheswide).Posit ion the axle plates on the side of these wheelgaps. Center them exactly and check to make surethere wil l beclearance for the wheels. Align them all sothe wheels won't be crooked. Dropping a straightedgeinto all four slots (as in Fig. 12-12) may help.If you're bolting the frame, dri ll Y4-inch holes anduse Y4-inch x z-lnch bolts to secure the wheel housingto the frame. Each ofthe axle plates gets two V4-inch x1V2-inch bolts mounted horizontally. This way each

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BEND B8 0 " = 1o 13crY' l(SY8") 1S7CYY1(5'2.'')122.C1('I')

"sTOP VIEW

.----.--~f,- ..-1- ....I t : : : . . .U 53.3 em ...-'10" (2.1 "),IA

SIPE VIEW

WH EEL H OU SIN Gf3END 6r: BEND c.r : 2 . 1 8 . 5 C Y 1 1 2.6h. 0 > 1 3 f [ f 'o f W I )(7'Z") (e'l/")o ~~

f 3 E N D Ar :Io 2.7crnD O Y L ' ?

8S5cn-.(33%")BEND Br :7c,""(3< l Y , / ?

15ec.Yl?(5'2Y')I3ND c.r :/60.5cYh(S'3U(.'')

TOP VIEW

Fig. 12-3. Frame, wheel housing, and axle plate details.

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Fig. 12-4. A pipe bending tool makes curves without kinks-here, the first bend of the frame.

Fig. 12-6. The end of the frame that wil l form the cart's tongueis pounded f lat for the hitch.

bolt goes through the inside of an axle plate, the frame,and the curled-over outside part of the same plate.If you're welding, use a low setting and keepmoving to avoid burning holes inthe thin conduit (I setmy arc welder to 50 amps and use 3/32-inch 6011welding rod). Welding galvanized metal gives off zincoxide fumes that can cause nausea, so only work in awell-ventilated area. Wear a filter-type respirator. Afterwelding, remove the slag with a wire brush and paint allthe welds to prevent rusting.B I K E C A R T B O X

A good bike cart box should be both strong and light.The Freighter is built from %-inch exterior plywood (cutas InFig. 12-13) and secured onthe edges with specialtrimmed-down molding. If you have access to a table

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Fig.12-5. For the third bend ofthe frame, turn the pipe benderupside down and pull on the conduit.


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Fig. 12-7. The finished hitch is strong, yet flexible. It 's made of a strip 01 tire sidewall or neoprene belting and is clamped with abolt and wing nut.

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Fig. 12-8. Make plates for the wheel axles from conduit boxcovers like the one at upper right. Pass up round plates orthose with "knockouts" (top center). and avoid Steel Citybrand (upper left). Finished plates, ready tor welding, are atlower right and center .

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saw, rip 1-inch lumber to make the molding asspecified; if not, use 1 x 1 stock and shorten the sideand end pieces 8 mm (V 4 inch). See Table 12-2 .

Glue the molding to the sides and ends. Assemblethese parts and use %-inch screws to clamp the glue(in predrilled 3.5-mm or 9/64-inch holes through theplywood). Glue and screw the bottom in place. Add theli ttle frame support blocks 5 ern (2 inches) from eitherend, where they'll brace the box against the frame.Sand and stain the box or paint it a nice bright color forvisibility at night.

C OR N ER M E TA L P R OT EC TO R SAn optional touch that wil l strengthen and protect thebox involves folding some simple corner guards out ofsheet metal (Fig. 12-14). You can buy suitable scrapsby the pound at sheet metal shops. Cut them to theshape shown in Fig. 12-15 with a pair of tin snips. Foldthe metal by clamping it lengthwise between twoboards ina vise; you can easily bend it 90 degrees withthe palm of your hand. Use pliers 10 bend the two tipsofthe metal guards so they fold over the top of the cart's


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Fig, 12-9, Dril l a t -ern ('J1!- inch)hole in each axle plate and saw a slot down to i t.corner post. Punch tiny holes with a nail or prick punch,Secure the units with 3/4-lnch wire nails. I like to addsome hefty 1 1/4-inch galvanized nails-two into themolding at the very bottom, and one straight downthrough the top of each corner post.

Fig, 12-; 0 For a bolted frame, bend the axle plates around a~Iece of pipe in a vise, Drill for bolt holes,

Add some rear reflectors, Attach the box to th eframe with t-inch sheet metal screws (if the frame'swelded) or 1 1/4-inch screws (if there are bolts in th eway). You may have to angle the 3.5-mm (9/64-inch)pilot holes for the screws to really sink into the frame

Fig. 12-11. Bend axle plates for a welded frame by clampingthem directly in a vise,

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F ig. 12-12. Position and clamp the frame when it's upside down. It's easiest to line up the axle plates by dropping a straight stickin to the s lots.

Fig. 12-13. Plywood cutting details.

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T ab le 1 2-2 . M old in K D e ta ils .M ol d i nK

1.5 em x 1.5 em (W' x %")4 corner posts. 30 em (12")1.5 em x 1.9 em (%" x 3(4")

2 side molding, 77 em (30~")2 end molding, 55.7 em (22")1.9 em x 2.3 em W4' Xl")

2 frame support blocks, 6 em (2")

O P TI ON A L C O I< N E RP I< O 'e C7 0~(26 GAUGE SHEET METAL)_j_ ~ 30.5


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Fig. 12-18. End view.

bumps (and take them head-on). Make sure the bike'sbrakes are in good shape before you take a heavyload downhill.

The Freighter is an almost indestructible work-horse. Its clearance of 25 cm (10 inches) means youcan haul it up curbs or over uneven ground. The bum-pers on three sides make it easy to tie on bulkyloads-even sheets of plywood. Because theFreighter only weighs 14 kg (31 pounds), it seems tofollow a bicycle almost by itself (Figs. 12-17 through12-19).

Fig. 12-19. The Freighter is both l ight and strong whether it has a bolted frame and stained box, as at left, or a weldedframe and painted box, as at r ight.

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