Trailer materials Trailer design
Trailer Types Trailer mechanisms
Overall Dimensions Weights and Capacities
Wheels and Tyres Couplings
Lights Suspension Types
Hubs and Stubs Brakes
Winches W.O.F regulations
Trailer materials-Galvanized steel
In current use, the term refers to the coating of steel or iron with zinc. This is done to prevent galvanic corrosion (specifically rusting) of the ferrous item. The value of galvanising stems from the relative corrosion resistance of zinc, which, under most service conditions, is considerably less than those of iron and steel. The effect of this is that the zinc is consumed first as a sacrificial anode, so that it protects exposed steel. This means that in case of scratches through the zinc coating, the exposed steel will be protected by the surrounding zinc coating, unlike an item which is painted with no prior galvanising, where a scratched surface would rust. Furthermore, galvanising for protection of iron and steel is favoured because of its low cost, the ease of application, and the extended maintenance-free service that it provides.
Info from: http://en.wikipedia.org/wiki/Galvanization#Metal_protection
Image from: http://smsteel.en.made-in-china.com/product/qbyJFcKVrzkx/China-Hot-Dip-Galvanized-Steel-Coil.html
Trailer materials-Aluminium
Aluminium is the most widely used non-ferrous metal. Relatively pure aluminium is encountered only when corrosion resistance and/or workability is more important than strength or hardness. A thin layer of aluminium can be deposited onto a flat surface by physical vapour deposition or (very infrequently) chemical vapour deposition or other chemical means to form optical coatings and mirrors.
Info from: http://en.wikipedia.org/wiki/Aluminium#Applications
Trailer types-Single axle
Single axle trailers are made for light boats, generally up to a maximum mass of 2tones. They are very easy to manoeuvre compared to tandem axle trailers as there is only one pair of wheels that pivot around one centre point. It isn't very common for this type of trailer to have brakes as the brakes on the towing vehicle would be enough to slow this down.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.loadmastertrailerco.com/galvanized-boat-trailers/
Trailer types-Tandem axle
Tandem axle trailers have to axles with four wheels to spread the load across a larger area, meaning you can have a much longer trailer which can hold a heavier load up to at least 4-5tones.
these types of trailers have usually got hydraulic or cable brakes to help slow the trailer down when the towing vehicle brakes, instead of the towing vehicle trying to stop the trailer by itself. The carried boat size is mostly 5.5 to 8 or 9 meters.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://sandston.olx.com/tandem-axle-boat-trailers-for-sale-nationwide-2011s-iid-69609919
Trailer types-Triple axle:
Triple-Axle trailers are made for boats longer than 8 meters, and weigh more than 5tones. They aren't usually used on the public roads much as they are very difficult to manoeuvre around tight corners because of the sheer length. They are usually used to transport million dollar luxury cruisers or yachts around big boat yards. They need to have brakes because the mass of the boat and trailer would be too heavy for the towing vehicle to stop it with it's own brakes.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.realxtrailers.com/Standard-Trailer-Features/
Trailer designs: A-Frame:
The front end of the trailer goes to the coupling in an A shape. The A-frame design is made for heavy duty trailers where there needs to be more weight distribution across the trailer compared to the Drawbar design. This means you can have a longer boat to tow as you don't have a long separation between the nose of the boat and the end of the towing vehicle.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.stonehouseforge.com/our_work3.htm
Trailer design-Draw bar/Pole tongue:
The frame of the trailer goes to a point, then a bar attaches to the coupling The Drawbar design is used for trailers that carry lighter loads than A-Frame trailers. But sometimes they can carry the same load mass depending on the materials used. The trailer has a smaller area for the load/boat to sit on, thus the ability to tow smaller, shorter, and loads with easy manoeuvrability .
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://ausfish.com.au/vforum/showthread.php?149389-Extending-Trailer-Drawbar
Trailer mechanisms-Rollers:
The rolling mechanism is the most widely used style for launching, and winching boats on and off trailers. Other than trailers with the bunks/skids holding the boat, the rollers help the boat roll/glide centered properly on the trailer. They are more expensive to manufacture, as they can rock on a point to form a 'V' shape, or be flat, other than bunks which are manufactured at a permanent angle.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.watsonsmarine.com.au/boat_trailers.php
Trailer designs-Bunks/skids:
This design is mostly used for the light sport craft trailers used to carry jet skis and other small boats with a relatively flat hull that don't need accurate cantering. Although sometimes if a trailer with this design carries a larger boat,(1-2tone) there are sometimes rollers going up the centre of the trailer to keep the boat well centered, but mostly, there are bunks angled as a 'V' to cradle the bottom of the hull, when being winched onto the trailer. Bunks are cheaper to manufacture than rollers, and are made in a 'V' shape, lined with carpet or fabric to stop the hull from being scratched, and reduce friction when launching and winching up the boat.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
A bunk trailer with rollers in the centre
Image from: http://www.southcoasttrailers.co.uk/product.php?cat_id=12&sub_id=0&pro_id=79
A bunk trailer with skids angled as a V in the center
Image from: http://timnoblestrailers.com/gallery.html
Over all dimensions:
Depending on the frame configuration of your trailer. Usually, the trailer should be 1-2ft longer than the overall boat length. It will allow sufficient manoeuvring and turning clearance between the trailer and the towing vehicle, and to have enough space for items such as; winch and V block, tow bar coupler, jockey wheel, spare trailer wheel etc.
Overall dimensions-Length:
Length: If you own a boat you can tow a trailer that can be 11.5m long, assuming that the car plus the boat doesn't exceed 20m which is the limit.
Overall dimensions-Width:
The maximum allowable width for trailers is 2.5 meters (excluding side marker lights, direction indicators and the bulge towards the bottom of the tyre). The only extra width allowed is:
240mm each side for collapsible mirrors
25mm each side for ropes, lashings, straps, chains, connectors and tensioning devices that aren't permanently or rigidly fixed to the vehicle; or J-hooks (to secure stock crates or bins)
75mm for hub odometers on a non-retracting, non-steering axle on each vehicle and on the axle that minimises the extra width
75mm for central tyre inflation (CTI) system hoses.
Overall dimensions-Height:
The maximum allowable height is 4.25 metres. An additional 25mm above 4.25 metres is allowed for tarpaulins, covers and lashings, straps, chains, covers, and related connectors and tensioning devices that aren't permanently or rigidly fixed to the vehicle. The height of the body or load of class TD trailers (those with a gross vehicle mass exceeding 10 tonnes) may be restricted by stability requirements – particularly the need for the vehicle to have a minimum static roll threshold (SRT: The static roll threshold of a vehicle is a measure of the potential for that vehicle to roll over sideways. Vehicles with a low SRT are more likely to roll over than those with a higher SRT, especially when going around sharp bends and in sudden emergency manoeuvres. That means the lower your SRT the less stable your vehicle is).
Overall dimensions-Ground clearance:
The minimum ground clearance for heavy trailers (IE: those with a gross vehicle mass over 3.5 tonnes) is 100mm. The ground clearance also has to be at least 6 percent of the distance from the nearest axle to the point where the ground clearance is measured.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Suspension types-Leaf springs:
these are the most commonly used springs for all kinds of loads from 140lb(64kg) to heavy boats that requiring big springs with even more leaves. They come in two basic types: double eye, eye-and-slipper. both permit easy access for inspection and maintenance. however, these types of springs are hard to maintain because moisture can get in between the leaves/slats and start corroding them.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://automotivepartsuppliers.com/difference-coil-spring-leafsprings/
Suspension types-Spring/Coil/Shock absorbers:
This type of suspension is not usually used on trailers as this setup would seem to be too complex to manufacture. They are used for relatively light loads, often in conjunction with shock absorbers. they give a relatively soft ride and have no major draw backs. Their complexity is the reason why they are less common on on boat trailers.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.campertrailers.org/stuarts_camper.htm
Suspension types-Torsion bars:
Torsion bars are designed to support torsional motion. They are a self-contained unit so there is no need for Springs, shock absorbers or other suspension components. They can be mounted to reduce frame height, and on a tandem axle or tri-axle trailer, each wheel can independently absorb a road shock without affecting any of each other, but they cost more to manufacture than conventional axles and if water or moisture gets inside the outer tube of a unit that is not galvanized, unseen corrosion/rust can develop.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.marathonpowerproducts.com/features.html
Weights and capacities:
Trailer Weight Estimates
This chart only shows weight capacities of single axle trailers
Trailer No. Trailer Trailer Weight
Capacity Axles Length Width
1000 lbs 1 15'4" 62" 295 lbs
1500 lbs 1 15'4" 62" 305 lbs
2000 lbs 1 17'2" 88" 492 lbs
2450 lbs 1 18'2" 96" 522 lbs
2999 lbs 1 18'2" 96" 625 lbs
3500 lbs 1 19'8" 96" 677 lbs
5000 lbs 1 20'8" 96" 933 lbs
7000 lbs 1 27'9" 96" 1512 lbs
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Bearings-Hubs and Stubs:
There are two types of bearings: Ball type, and Taper roller bearings. Bearings must be well lubricated to stop them corroding, and most of all, seizing up. The ball type bearing is usually seen on the old style trailers and isn't very commonly seen on modern day trailers. The taper roller bearing is the most common type of bearings found on trailers. This type of bearing can create a lot of free-play, so it is important to keep it well adjusted to maintain it's 'long life'.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Ball type bearing:
Image from: http://www.nskamericas.com/cps/rde/xchg/na_en/hs.xsl/self-aligning-ball-bearings.html
Taper roller bearing:
Image from: http://www.skf.com/portal/skf/home/aptitudexchange?contentId=0.237932.237939.774331.774333.518442
Wheels and tyres:
It is very important to have wheels and tyres large enough so as to support the weight of the trailer, boat and equipment when travelling at open road speeds.
If the wheel and tyre combination is too small, the tyre will fail due to overheating.
Wheels and tyres-Bias construction:
Bias tyre (or cross ply) construction utilizes body ply cords that extend diagonally from bead to bead, usually at angles in the range of 30 to 40 degrees, with successive plies laid at opposing angles forming a crisscross pattern to which the tread is applied. The design allows the entire tire body to flex easily, providing the main advantage of this construction, a smooth ride on rough surfaces. This cushioning characteristic also causes the major disadvantages of a bias tire: increased rolling resistance and less control and traction at higher speeds.
Info from: http://etcentre.co.uk/pages/TyrePage.html
Image from: http://etcentre.co.uk/pages/TyrePage.html
Wheels and tyres-Radial construction:
Radial ply tyres are now the most common tyres in use on British roads representing more than 90%. Some radial ply tyres now have a run flat capability known as Self Supporting Run Flat (SST) tyres which are becoming more common particularly when fitted as an original equipment. Older diagonal (cross-) ply tyres are now very rarely seen and have effectively been replaced by radial ply tyres.
Info from: http://etcentre.co.uk/pages/TyrePage.html
Image from: http://etcentre.co.uk/pages/TyrePage.html
Wheels and tyres-Self supporting run flat (SSR)
Self Supporting Run Flat (SSR) tyres are designed to provide a limited run on period following a puncture. These are identified by the letters "RF" in the size marking. To be categorised as a run flat tyre, the minimum distance they must achieve in a run flat condition is 50 miles (80 km) at a maximum speed of 50 mph (80 km/h) and at a minimum of 80% of their maximum load capacity. It is essential the vehicle is equipped with a tyre pressure monitoring system to enable use of run flat tyres.
Info from: http://etcentre.co.uk/pages/TyrePage.html
Image from: http://etcentre.co.uk/pages/TyrePage.html
Wheels and tyres-wheels:
It is crucial to have the correct size wheel to tow your boat on, preferably 14-15" for Single axle and tandem axle, and a larger size for triple axle(15 and up) The best material for wheels would be galvanized material, same as used on your trailer. This means that there will be less components on your trailer that have a chance to corrode or rust.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Brakes:
There are tow designs for brakes and and two systems as to how brakes are made. There is disk and caliper, and the old fassioned Drum and shoe brake system. Both of them can be operated hydraulically or by cable.
Brakes-Drum and shoe:
Drum brakes are the simplest and easiest to manufacture as there are two shoes(operated hydraulically or by cable) being pushed against the inner wall of a drum type cover. This design isn't very sufficient for salt water trailers as water can get inside the drum and start corroding the moving parts.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.aa1car.com/library/drum_brakes.htm
Brakes-Dicks:
Disk brakes are more recommendable than drum brakes as they are stronger and they have less parts that can be corroded by salt water. They are mostly used for tandem axle and triple axle trailers as they have to carry a heavier load than single axle trailers. They are most commonly operated through a hydraulic tow coupling which pushes against a master cylinder when the towing vehicle brakes and sends the brake fluid to the brake callipers.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.aquaskier.com/articles/2004_boat_buyers_guide.htm
Couplings:
Couplings are the most important part of a trailer as it is the mechanism which fits the trailer to the towing vehicle. There are two different designs, one made for braked trailers, and one for standard trailers. They are usually clamped/lock onto a tow ball by a spring loaded leaver. A non braked coupling can support at least 1.5t, where a braked coupling can support up to 3.5t.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Standard coupling:
Image from: http://www.smartmarine.co.nz/trailer-coupling-lock-p-997.html
Braked coupling:
Image from: http://www.trojan.co.nz/index.asp?PageID=2145834345
Winches-Manual:
Manual winches are designed to pull small boats and large boats onto the trailer. Depending on the set up/configuration of your winch, you should be able to bring in boats ranging from 1tone, to 3 or 4 tones max. They are different from the others. Some have more pulling power, and some have less. It all comes down to the gearing configuration each manufacturer makes the winch to be.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
A manual winch:
Image from: http://www.ab1c.com/en/pro_show.asp?id=844&class1=6&class2=41
Winches-Electric:
Electrical winches are the bomb for retrieving heavy boats on really steep boat ramps. They are connected to the towing vehicle's battery supply by a wiring kit supplied by the maker. They use 12-15A with no load, and 80 amps or more with a full load. compared with the manual winches it is more expensive and requires more maintenance and watching over.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Electric winch:
Image from: http://www.aubrett.com/auction/marine/crw/powerwinch.htm
Lights:
A trailer must display lights as per W.O.F. regulations, consisting of:
Marker lights; forward facing (white/clear) = turned on with vehicle side lights
Tail-lights; rearward facing (red) = turned on with vehicle side lights
Stop lights; rearward facing (red) = activated by towing vehicle stop lights
Indicators; rearward facing (red or orange) = activated by towing vehicle indicators
Reflectors; rearward facing (red) = illuminated by following vehicles lights.
Info from: https://docs.google.com/present/edit?id=0AUMgndAxsd76ZGY1Mm45OThfMGdia2RraDY0&hl=en_US
Image from: http://www.accessconnect.com/trailer_wiring_diagram.htm
W.O.F regulations:
If you tow a light trailer (up to 3500kg when loaded), it must have a WoF. To meet the WoF standard your trailer must be in good condition (no rust around safety areas) and it must have the following equipment in good working order:
A: A safe and strong coupling and a safety chain or cable.
B: If the trailer or its load is more than 2 metres wide, it must have two white lights at the front to show how wide it is.
C: Safe tyres – the tread depth must be at least 1.5mm right around the tyre.
D: Mudguards.
E: Two red reflectors at the back (one on each side).
Your trailer will also need the following features:
A: Two red lights at the back to show how wide the trailer is.
B: Direction indicators at the back.
C: Two red stop lights at the back, if the driver's signals can't be seen.
D: A number plate light at the back.
E: A current trailer WoF issued by a WoF inspector. This must be renewed:
- every 12 months for the first six years, then
- every six months after.
F: A licence label needs to be positioned close to the number plate.
Loading your trailer safely:
To ensure the stability of the vehicle and trailer combination when towing, the trailer should exert a downwards force on the towing vehicle's towbar equal to about 10 percent of the weight of the trailer plus its load.
The load on the trailer must not:
- extend more than 4 metres behind the rear axle
- extend more than 1.25 metres on either side from the centre of the trailer.
If the load extends more than 1 metre behind the trailer, you must tie on a white flag, or a red, orange or yellow fluorescent flag. The flag must be at least 40 centimetres by 30 centimetres in size. The load must be tied on firmly and must not touch the ground.
Info and images from: http://www.nzta.govt.nz/resources/roadcode/about-your-vehicle/light-trailer-requirements.html
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