Materials Used
Boat trailers are generally made of galvanized mild steel or aluminium. When using mild steel the trailer is painted with a protection paint coating to stop it from corroding away. Generally boat trailers should be made out of metals which doesn't not rust easily and strong enough to hold the boats weight. Galvanized mild steel is most commonly used as its the cheap. Its strong and rust resistant. Galvanizing is a process in which the steel is coated with a layer of zinc to protect it from rust. Mild steel is also easily fabricated and welded. More easier to make than aluminium.
Aluminium is not that common because of the cost. It is also hard to fabricate and weld. Although aluminum is very strong, light and corrosion resistant it comes out to be more expensive. Bellow is a boat trailer mad out of aluminum.
Single Axle Trailer
Boats less than 6 meters and less than 2000kg are carried on a single axle boat trailer. Single axle trailers can me moved very easily and more easier to backup than double axle and triple axle.
Double Axle Trailers
Double axle trailers provides better weight distribution on the trailer. Used for boats longer than 6 meters or over 2000kg. It is also harder to reverse and harder to move with hand. Tyres and bearings get worn out quicker that single axle. An advantage is that if you have a flat tyre and do not have a spare tyre you can take the flat tyre out and continue driving to the nearest tyre shop. Try that with a single axle!
Triple Axle Trailers
Triple axles are used with boats more than 10 meters and heavier than 4000kg. These include cabin crusiers , sport yachts and racing style power boats. These types of trailers provide a bigger foot print and geat stability. There are other muli axle trailers used for bigger applications and what the customer wants.
Trailer Designs
Trailer designs vary to the need of the customer and purpose of the design. These are normally a A frame or a single drawbar.
Single Drawbar
This type of trailer is used for small boats example jet skies and small dingies. It is not as strong as the A frame type as all the weight is on the drawbar and sometimes breaks at the joining of the frame and the drawbar.
A Frame Draw bar
The A Frame design is stronger than the single frame as the weight is evenly disributed around the trailer. This design is used for bigger boats and is more reliable than the single drawbar.
Bunk Type Trailer
This type has two bunks of wood to support the keel. One bunk on each side supports the keel. They are padded with a materal to prevent scrathing or damage to the keel. Good for flat bottom boats.
Roller Type Trailer
This type uses plastic or rubber rollers to support the boat. The rollers make the boat easier to launch and pullin. The boat easily slide on the rollers. This type is more expensive than the bunk type but way better to use. This type is more in use these days.
Dimensions and WOF
You can tow a trailer that's up to 2.5m wide, 4.25m high when loaded, and 11.5m long, as long as the combined car and trailer length does not exceed 20 metres. The driver of the car towing a trailer (not another driver, and not the owner of the trailer) is responsible for any damage that happens while towing. If the trailer has a safety problem, such as an expired WOF, the driver of the towing car is responsible. The weight depends on the vehicle and type of trailer regarding the types mentioned previously on the blog.
Warrant of Fittness
All trailers must have a current warrant of fitness and registration to be driven on the road. To meet the WoF standard your trailer must be in good condition and it must have the following equipment in good working order:
- A safe and strong coupling and a safety chain.
- 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.
- Safe tyres – the tread depth must be at least 1.5 millimetres right around the tyre.
- Mudguards.
- Two red reflectors at the back (one on each side).
- Two red lights at the back to show how wide the trailer is.
- Direction indicators at the back.
- Two red stop lights at the back, if the driver's signals can't be seen.
- A number plate light at the back.
- 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.
Suspension Types
Good suspensions on the trailers will extend the overall life of the trailer. This will also protect the boat from jumping around and keep in place.
Leaf Springs
Leaf springs are the most comon type used in standard trailers. The spring is dependent on the amont of leafs (metals) there is and how it is configured. The leaf springs are noisy on the road and weight on these types should be considered.
The strut type (shock absorber and spring)
These are a very rare type of suspension used in boat trailers. It is generally expensive but a good suspension with a combination of a spring and shock absorber. Custom trailers use this when the customer wants this type of suspension used in their trailers.
Torsion Axle Suspension
This type is a a step away from the leaf type but less expensive than the stut type. Torsion bars are cushioned and held in place in the axle housing by a block of rubber or individual rubber chords. The hub of the wheel is mounted on a leaver arm on the outer end of the torsion bar. This is generaly used in small boat trailers.
Wheels and tyres
Trailer wheels are generally galvanized steel and also alloys. Its up to the customer and application it is used for. Some heavy boats might need heavy duty wheels to compensate the weight. Choosing the wheels can be for looks as well. Its all about what the customer wants.
When looking at tyres. First of all the thread on the tyre should be WOF acceptable which is a thread depth of 1.5mm minimum. The type of thread is also considered as to where it is being used. Example there is a different thread for snow. You can choose what type of tyres you need for the purpose. Radial tyres are best considered for everyday use as it is cheap and haas a strong construction which can handle a bit of dings and dangs. You should also check the load rating on the tyres to which how much weight it can handle. Always check your tyres for cracks and bubbles regularly.
Hubs and Stubs
Hubs are designed to support the axle and provide a base for the wheels ot be mounted on. They are usually galvanized steel to protect from rust. They also have a weight rating which should be taken in consideration when choosing the hub to be used on the trailer.
Stubs are where the wheels get bolted on. The wheels should fit in correctly and the wheel should be secure in place with the wheels tighten to the right torque specification.
Brakes
Elecctric
These brakes are electronically operated when the brake pedals are pressed in the vehicle. It is ocnnected with the brake lights. When the brakes are applied the control unit sends a signal back to the brakes in the trailer and starts breaking. If the trailer detaches itself the breaks will lockup and the trailer will stop. This is a
good safety feature for this type of breaking on the trailer.
There is also the disk and drum type breaks which like the ones in the cars. It is alctivatd by hydrloc pressure to put pressure on the disk or the drum to get the wheels to stop. Below is the disk type with break pads.
Hydrolic Surge
Hydraulic surge brakes are a totally trailer self-contained braking system, requiring no electrical, hydraulic or other connection of brake sensing components to the tow vehicle for automatic operation of the trailer brakes. In a hydraulic surge brake system, the inertial differential pressure developed between the tow vehicle and the trailer, during the braking process, creates a mechanical pressure which is applied to the push rod of the master cylinder in the hydraulic surge brake coupler. This mechanical pressure is proportional to the difference in pressure between the two vehicles and therefore, the hydraulic output of the brake coupler, and resulting brake operation, is automatic, regulated, and proportional to the amount of braking being applied to the tow vehicle.These systems can use disk or drum or sometimes both for parking and breaking capabilites for heavy duty trailers.
Bellow is a Drum brake assemply
Lights
Lights are ma must on trailers as to let others know when you are breaking and turning etc. The trailer will not pass a warrant of fitness test if the lights were not working. You should always check the lights as its a very important thing. Lights not working properly can cause a lot of crashes and problems with other drivers as they will not know what you are doing and cause major problems. And its a rule that the trailer should also be fitted with a set of reflectors in each side.
These days there are LED lights used which are brigher and uses low power. So in consideration LED lights is the way to go.
Winches
Boat winches come in two types. The manual type and the electric type. It can be made up of cabe, rope or different types of chains and strapings. The rope and strap type are the best used in the marine industry as it will not rust.
Electronic winches are more expensive but easier to use. Again winches will be choses as what the customer wants and how much he is willing to spend on the trailer. Winches should be mounded properly.
Couplings
This is the non braked type coupling. This is located at the end of the drawbar and gives a secure connection with the trailer and the tow bar of the vehicle pulling the trailer. Also weight and force rating of the couplings are considered when choosing what size boat trailer it will be used for.. This non braked coupling us mainly used in small application example a trailer for a jet ski or dingy where the vehicles braking is sufficient enough to brake the trailer.
This is the braked type coupling which has a master cylinder and brake lines that will create hydrolic pressure when the towing vehicle slows down. The pressure is applied to the brakes in the trailer wheel which also brakes the trailer. Read Hydrolic surge system on top of the page. This type is being used in big applicaitons
and now days coming in most trailers used.
References
http://www.trojan.co.nz/
http://www.voyagertrailer.co.nz/
http://www.consumer.org.nz/reports/towing-rules
http://www.nzta.govt.nz/resources/factsheets/13d/trailers-light-simple.html
http://www.nzta.govt.nz/resources/roadcode/about-your-vehicle/light-trailer-requirements.html
This is a remarkable post! Where did you get those images? The different kinds of boat trailers are incredible. How ingeniously designed are they?
ReplyDelete- Delena Millener