Preparing for navigation is always a balance between comfort and functionality, where every piece of equipment plays a role. boat-cartIt's a system that allows for safe transportation and storage of the powertrain, and if you're not fit enough, you can damage the lower unit, you can deform the mounts, you can even fall over expensive equipment when you're in transit, which is why it's a question of calculating accurately. trolley-size It is a priority for every owner of the boat.
It becomes obvious that there are no universal solutions in operation, because the geometry of outboard motors varies greatly depending on the manufacturer and year of production. You have to consider not only the length of the lower unit leg, but also the location of the vomiting, the height of the foot and the total mass of the device. Mistakes in the design stage or the choice of the finished design can lead to the engine being skewed, which will adversely affect the condition of bearings and os.
In this article, we will discuss in detail how to determine the optimal frame-pieceYou'll learn why the width of the base is more important than the length of the base, and how to calculate the height of the rack for a reliable support, and how to build or purchase a device that will last for years, keeping the engine in perfect technical condition.
Critical parameters of the lower unit leg
The basis for calculating any cart is an accurate knowledge of the geometry of your engine’s lower unit leg. The length of lower unit Standard values range from 381 mm (15 inches) for the short leg to 508 mm (20 inches) and 635 mm (25 inches) for the long legs used on high-speed vessels.
But just knowing the length is not enough. tilt The engine is in a transport position because it directly affects the projection of length onto the horizontal plane. If the trolley is too short, the screw will be too high, shifting the center of gravity, and if too long, the motor can rest on the ground or elements of the structure when shaking.
- 📏 Measure the distance from the plane of attachment to the transom to the lowest point of the screw in the lowered state.
- ⚙️ Consider the possibility of adjusting the angle of the trim, as in the position for transportation the motor is often fixed in the extreme upper or lower position.
- 🔩 Pay attention to the diameter of the lower unit at the point of contact with the support to correctly choose the material of shock absorbing inserts.
⚠️ Note: When measuring the length of a lower unit, be sure to consider a reserve of 5-7 cm for installing soft pads or clamps, otherwise the metal of the frame can damage the anti-corrosion coating of the lower unit.
Also an important nuance is the form. feather-reducerTwo-stroke motors often have a more compact foot, whereas modern four-stroke models have a massive, complex foot, and the cart's size should allow the motor to be positioned so that the most protruding parts of the gearbox do not touch the supporting elements of the frame when vibrating while the car is moving.
Calculation of the dimensions of the support frame and base
The foundation of a reliable design is correctly calculated support-frameIts dimensions are determined not only by the dimensions of the engine itself, but also by the need to ensure stability when parking on uneven ground, and the width of the base should be sufficient to prevent the structure from tipping over under the weight of a heavy four-stroke engine, which can weigh more than 50 kg.
For most outboard motors with a capacity of up to 15 hp, the width of the base in the range of 400-500 mm is considered optimal. If you plan to use a trolley for more powerful units, the width is considered optimal. transom-beam This will provide the necessary stability lever and allow you to place additional attachment elements.
The length of longitudinal spars also plays a role. Too short frame will make the cart unstable in the longitudinal plane, especially when climbing the curb. The recommended length of the base is 60-80 cm, which allows you to conveniently move the structure, holding it by the handle, and provides enough space to accommodate the wheel pair.
Stand height and mounting point of the transom plate
The vertical parameter of the trolley is the most difficult to calculate, since it depends on the height of the motor mounting point to the transom. transom plate The cart should be positioned on a trolley at such a height that the transport position of the lower unit does not touch the ground, but the center of gravity of the whole system is as low as possible.
When designing a vertical support, you need to be able to adjust the height of the attachment, and this is done by creating a series of holes or using a telescopic assembly. Standard height installation of the engine above ground level in the transport position should be at least 15-20 cm, to exclude screw impacts on roughness of the road.
It is also important to consider the design of the fastenerIt has to be made of a thick-walled tube or corner to withstand dynamic loads. The weak point is often the connection of the vertical rack to the horizontal base, so this knot requires reinforcement with scarves or additional ribs of stiffness.
Table of compatibility of trolley sizes and engine power
To make it easier to select or manufacture a trolley, you can use averaged data, proven by practice, and here is a table showing the dependence of the dimensions of the structure on the power class of the engine, which is the starting point for design.
| Power class (hp) | Recommended base width (mm) | Stand height (mm) | Wheel diameter (inches) |
|---|---|---|---|
| 2.5 - 6 | 350 - 400 | 500 - 600 | 8 - 10 |
| 8 - 15 | 400 - 450 | 600 - 700 | 10 - 12 |
| 20 - 30 | 450 - 500 | 700 - 800 | 12 - 14 |
| 40 and above | 500 - 600 | 800 - 900 | 14 - 16 |
Using this data, you can quickly estimate whether you will be suitable for a ready-made solution or need to use it. customizationRemember, for heavy motors, it's better to lay the margin on the width of the base, because stability is more important than compactness.
It is also worth noting that the diameter of the wheels directly affects the cross-country ability: small wheels (8 inches) are only suitable for smooth asphalt, whereas gravel roads and sand to the ramps require wheels with a diameter of 14-16 inches with a camera.
Materials and design features
The choice of materials for the trolley is dictated by the operating conditions: constant contact with water, salt and the sun. stainless steel Or galvanized pipe. Using conventional ferrous metal will require high-quality painting and regular maintenance, otherwise corrosion will quickly destroy the welds.
For elements in direct contact with the motor (plate, clamps), it is better to use aluminum These materials are inert and will not cause galvanic corrosion on the engine parts, and it is important to avoid direct contact of dissimilar metals without an insulating gasket.
- 🛡️ Use a profile tube of square or rectangular section - it provides better twisting rigidity compared to round.
- 🔧 Consider removable design elements if you plan to store the cart in the trunk of the car or a small storage room.
- 🎨 Apply powder paint for metal parts - it lasts longer than ordinary enamel in the