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Truck and Trailer Equipment – Attaching a Semi Trailer to a Road Tractor
How is a road tractor connected to a semi-trailer? The attachment between the tractor and the trailer is made by two connecting devices. One is the “fifth wheel” that is mounted on the rear frame of the road tractor. The other is called the “kingpin”, which is located on the front end of the truck trailer.
What is a Fifth-Wheel?
Originally, a fifth wheel was a steering mechanism resembling a wheel that enabled the front axle of a horse-drawn wagon to rotate when making turns. Around 1910, John C. Endebrock invented a device for coupling trailers to motor vehicles. In its initial use, trailers were towed by Ford Model “T” passenger cars. This coupling scheme required three men to hook to and unhook the trailer from the automobile. In 1918, Endebrock designed a new coupling devise that allowed a single driver to easily connect the tractor and the trailer. The new fifth wheel design used a jaw with a spring locking device mounted on the fifth wheel plate that was attached to the tractor frame.
Today, the fifth wheel serves as a coupling device that attaches a road tractor to a semi-trailer. A fifth wheel is a heavy metal disc with a “V” shaped slot. It is attached horizontally to the chassis above the rear axles of the road tractor. The “V” slot is located at the rear and it contains a locking device. The fifth wheel mechanism used to connect tractors and trailers today is very similar to Endebrock’s design from the early twentieth century.
What is a Kingpin?
A kingpin is a heavy metal cylindrical pin that is located underneath the front end of the trailer. The kingpin is the mechanism on the trailer that locks it to a road tractor. It is typically positioned between 18″ to 48″ from the trailer nose. A greased metal grid plate surrounds the kingpin. This grid plate allows the fifth wheel to slide underneath the trailer. When the tractor is backed into the nose of a trailer, the fifth wheel pivots and slides underneath the trailer’s grid plate. The fifth wheel then locks onto the trailer’s king pin.
When coupled to the kingpin, the fifth wheel enables the semi trailer to rotate at the point where the fifth wheel and kingpin are joined. The rotating attachment allows the tractor-trailer combination to make turns and provides stability and maneuverability on the road. When the load is delivered, the driver disconnects the tractor from the trailer by rolling down the trailer’s dolly legs. He then pulls a lever to disengage the fifth wheel locking mechanism and drives the tractor away from the trailer.
For more information about semi-trailers, see American Trailer Exchange
About the Author
Greg Pratt has enjoyed a 33-year career in the semi-trailer sales and leasing business. He developed and managed a 20,000 unit trailer leasing company; managed a multi-branch trailer marketing firm; and, successfully liquidated trailer lease portfolios for investment firms, banks and equipment leasing companies. He founded American Trailer Exchange in 1992. Greg is considered by many in the trucking and equipment finance industries to be an expert in his field. He is often consulted for equipment valuations and industry market trends.
Greg has an M.B.A degree from Roosevelt University-Chicago, and a B.S. degree from Ball State University.
Greg lives in the Atlanta, Georgia area with his wife and five children. He has lead worship bands, and plays the trumpet. He has taught courses on conflict resolution, leadership training and team building. He enjoys playing basketball and running in 5K and 10K races.
For more business information visit: www.amtrex.net
Collins Hi Speed Dolly Instructions
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2 CAMO 13-17 DEMCO Basket Straps LOOPS Tow Dolly, AXLE $39.58 |
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Jig Welded 3/4″ axle size Go Kart / Dolly Steering Spindles with nylon inserts $15.99 |
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Jig Welded 5/8″ axle size Go Kart / Dolly Steering Spindles with nylon inserts $22.99 |
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13″-35″ TOW DOLLY STRAPS FOR, AXLE STRAPS, FREE SHIP $33.49 |
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Milwaukee 43-40-0300 Rear Dolly Frame W/Axle $23.10 |
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AXLE STRAP, FOR TOW DOLLY, RATCHET, TIE DOWN, TRUCK $7.25 |
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Conveyor Belt Wheels Axle Dolly Mover House Trailer $1,500.00 |
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4 – GATOR 15″-20″ DEMCO STYLE TOW DOLLY STRAPS AXLE $99.97 |
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4 – GATOR 13″-17″ DEMCO STYLE TOW DOLLY STRAPS AXLE $98.97 |
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12″-18″ TOW DOLLY STRAPS plus RATCHETS AXLE SHACKLE SLING CLEVIS AUTO TRANSPORT $57.97 |
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13″-35″ TOW DOLLY STRAPS plus RATCHETS AXLE SHACKLE TIE DOWN CLEVIS SLING AUTO $57.97 |
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AXLE DOLLY Auto Restoration Tool Rotisserie Car Truck $150.00 |
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3/8 X 10FT GRADE 70 15″ HOOK GRAB HOOK TOW DOLLY AXLE $61.37 |
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3/8 X 10FT GRADE 70 15″ HOOK GRAB HOOK TOW DOLLY AXLE $113.37 |
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3/8 X 10FT GRADE 80 SLIP HOOK TOW DOLLY AXLE STRAP $68.37 |
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3/8 X 10FT GRADE 80 SLIP HOOK TOW DOLLY AXLE STRAP $128.37 |
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5, MID LINKS, 7/16-1/2 FOR TOW DOLLY, AXLE, STRAPS $29.99 |
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Blue Fontaine Lowboy w 6 Axle Hydra-Steer Dolly & Tri-Axle Peterbilt DCP 1/64th $155.00 |
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RECOVERY STRAP TOW 10″ DOUBLE PLY 20FT TOW DOLLY AXLE $233.49 |
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E-TRACK 2″SHORT END FOR RATCHET ASSY, tow dolly, axle, sling, shackle, clevis $6.97 |
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2 SOFT Cycle Tie Down Quad Honda Harley Tow Dolly Axle Straps 4 PAIR Choice $15.92 |
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AXLE DOLLY PLANS ULTIMATE auto cart rotisserie 12 10 bolt ford 9 inch rear end $9.99 |
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AXLE DOLLY PLANS ULTIMATE cart 12 10 bolt ford 9 inch rear end car rotisserie $9.99 |
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Single Axle Car Dolly Travel Dolly Bidadoo $51.00 |
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(4) 21″ PREMIUM Axle Straps Auto Tie Down Tow Dolly R $26.99 |
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12,000lb. Tow Strap Recovery Pull Rescue Dolly Axle $21.99 |
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2 DEMCO Auto Basket Straps Tow Dolly Wheel Net Axle B $42.98 |
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2 DEMCO MINI Basket Car Straps Tow Dolly 13″-15″ Axle B $42.98 |
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4 Premium Axle Strap COMBO Kits FREE SHIP Tow Dolly Yel $84.98 |
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MACHINERY MOVING 20,000LB. 3 AXLE SKATES DOLLIES ROLLERS MOVERS MICE *SEE VIDEO* $1,500.00 |
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10-E-TRACK 2″SHORT END FOR RATCHET ASSY TOW DOLLY, AXLE $59.97 |
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(2) 21″ (2) 31″ Axle Straps FREE SHIP Tow Dolly Blue $27.98 |
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A-BRACKET FOR RATCHET (EACH) FOR TOW DOLLY, AXLE STRAPS $4.99 |
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TOW TRUCK FUNNEL 8 PK FOR TOW DOLLY AXLE STRAP CLEVIS $19.95 |
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SIDEWAYS HOOK FOR RATCHET (EACH) FOR TOW DOLLY, AXLE $4.99 |
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STEEL CORNER PROTECTOR (EACH) FOR TOW DOLLY, AXLE $3.99 |
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PEAR LINK G43 21,600 LBS FOR TOW DOLLY AXLE CLEVIS $14.67 |
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DCP SILVER SINGLE AXLE CONVERTER DOLLY 1/64 $0.99 |
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DCP SILVER SINGLE AXLE CONVERTER DOLLY 1/64 $0.99 |
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TOW DOLLY, AXLE STRAP, HDWD COMBOS, R, J, T, GRAB, NEW $6.99 |
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RATCHET PAIR CHOICE FOR TOW DOLLY AXLE STRAP CLEVIS $21.47 |
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2 Demco Kar Kaddy Tow Dolly Straps Rugged Weave Axle B $44.98 |
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2 Demco Kar Kaddy Tow Dolly Straps Rugged Weave Axle S $44.98 |
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2 Demco Tow Dolly Straps 2 Ratchets Rugged Weave Axle S $59.98 |
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4 INCH RATCHET, TOW DOLLY AXLE STRAP TOWING CLEVIS $26.63 |
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Playmobil Horse Transporter Race Car Trailer Red Dolly Wheel Axle 3927 $1.99 |
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10 CLEVIS SLIP HOOKS W/LATCHES 5/16 FOR TOW DOLLY, AXLE $51.20 |
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12 – 10FT Lasso O Ring Flat Bed Tow Dolly Axle DOT B $98.57 |
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TRANSPORT CHAIN 5/16 G70 TOW AXLE STRAPS SLING SHACKLE CLEVIS Tow Dolly Tie Down $2.15 |
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8FT LASSO W/CHAIN GRAB CAMO X-TREME Tow Dolly, Axle $19.85 |
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2X30 RAT ASSY W/PEAR GRAB CAMO X-TREME Tow Dolly, Axle $35.99 |
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CLUSTER HOOK R J T RATCHET AXLE STRAP TOW DOLLY SHACKLE $29.97 |
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Ratchet W/CHAIN GRAB CAMO X-TREME Tow Dolly, Axle Strap $19.85 |
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8FT LASSO W/R,T,J, GRAB CAMO X-TREME Tow Dolly, Axle $24.85 |
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(8)-8FT CAMO X-TREME Lasso Straps, Tow Dolly, Axle $69.93 |
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CLUSTER HOOK R J T RATCHET AXLE STRAP TOW DOLLY SHACKLE $39.95 |
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1) Utility Box Tow Dolly Tandem axle Trailer Tire 8ply $88.29 |
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(4) 31″ CAMO X-TREME Axle Straps, Tow Dolly, Tie Down $31.00 |
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2-21, 2-31 CAMO X-TREME Axle Straps, Tow Dolly, TieDown $27.54 |
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(4)-21, CAMO X-TREME Axle Straps, Tow Dolly, TieDown $26.99 |
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(4)-8FT CAMO X-TREME Lasso Straps, Tow Dolly, Axle $44.93 |
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8 LASSO, STRAPS, SLING, TOW DOLLY, AXLE STRAPS, CHOICE! $59.99 |
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2″ TOW DOLLY LASHING WINCH FOR TIE DOWN, AXLE, STRAP $6.99 |
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(12)- CAMO X-TREME Axle Straps, Tow Dolly Tie Down Sling Shackle Clevis Auto $97.99 |
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4 – 2″ TOW DOLLY LASHING WINCH FOR TIE DOWN AXLE STRAP ROLLBACK SHACKLE CLEVIS $42.91 |
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6 – 2″ TOW DOLLY LASHING WINCH FOR TIE DOWN AXLE STRAP ROLLBACK CLEVIS SHACKLE $56.91 |
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(2) 21″ (2) 31″ Axle Straps FREE SHIP Tow Dolly Tie Bla $27.98 |
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DCP1/64 SIX AXLE BEAM DOLLY $26.00 |
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3 INCH RATCHET, TOW DOLLY AXLE STRAP TOWING CLEVIS $21.45 |
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2 Premium 2″x8 Lasso Straps FREE SHIP Tow Dolly Axle Y $23.99 |
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2″ TOW DOLLY LASHING WINCH, TIE DOWN, SHACKLE, CLEVIS, AXLE, STRAP, RATCHET $6.99 |
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3/8 X 10FT, GRADE 70, GRAB HOOKS TOW DOLLY AXLE TIE DOWN CHAIN SHACKLE CLEVIS $46.49 |
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5/16 X 20FT, GRADE 70, GRAB HOOKS,FOR TOW DOLLY, AXLE, $49.97 |
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E TRACK WITH O RING (EACH) TOW DOLLY AXLE SLING CLEVIS SHACKLE TIE DOWN AUTO $6.98 |
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3/8 X 6FT, GRADE 70, J HOOK, END PC, TOW DOLLY, AXLE, $79.99 |
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DEMCO STYLE 13-17 LOOP STRAPS ,FOR TOW DOLLY, AXLE,BLUE $14.99 |
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NYLON SLING EN1-901×4′, FOR TOW DOLLY,AXLE STRAP COMBO $5.62 |
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12″-18″ TOW DOLLY STRAPS CLEVIS TOWING AXLE FREE SHIP $33.49 |
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2 Premium 2″x8 Lasso Straps FREE SHIP Tow Dolly Axle BK $23.99 |
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2 SHORT RATCHET HANDLES TOW DOLLY STRAPS AXLE $22.99 |
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NYLON LIFTING SLING EE4-904×20′ AXLE STRAP TOW DOLLY CLEVIS SHACKLE HEAVY EQUIP $168.80 |
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NYLON SLING EN1-902x12ft LIFTING SHACKLE CLEVIS TOW DOLLY AXLE WRECKER AUTO $21.48 |
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NYLON SLING EN2-902x6FT LIFTING SHACKLE TOW DOLLY CLEVIS HEAVY EQUIPMENT AXLE $23.32 |