Your own garage is not just a parking place, but a full-fledged workshop where every square meter should be functional. For a full-fledged repair or regular maintenance often lacks access to the bottom of the body. A full observation pit requires capital earthworks, waterproofing and is often not possible in garages with high groundwater levels.
The perfect compromise becomes metal-overpasswhich can be collected on its own. It takes up less space, does not require a deep pit and can be dismantled or moved if necessary. In this article, we will take a detailed look at how to design and weld a reliable structure that will support the weight of your car.
Self-manufacturing allows you to save a significant amount compared to the purchase of finished industrial designs. You also control the quality yourself. metal and the reliability of welds, which is critical for safety.
Selection of design type and calculation of dimensions
Before purchasing material, you need to decide on the type of overpass. For passenger cars and light trucks, a two-level design is most often used. It consists of two parallel platforms (gauges), on which the wheels drive, and support racks. This scheme provides access to the bottom, suspension and exhaust system from any side.
The key parameter is overall width and the length of the race zone. The standard gauge of passenger cars varies from 1400 to 1600 mm, so the internal distance between the sides of the overpass should be at least 800 mm for a comfortable arrival. The length of the working part is usually 3-4 meters, and the length of the race ladder is 1-1.5 meters.
It is important to consider the height of the lift. The optimal height for comfortable work is 1000-1200 mm from ground level. This allows a person of average height to work standing up without leaning too hard. If the ceiling is low in the garage, the height will have to be reduced, but then you will have to work lying on a cart.
Required materials and tools
For the manufacture of a durable overpass will require high-quality rolling-out. The base of the supporting frame is best made of the channel No. 10 or No. 12, which withstands serious loads on the bending. For crossbars and stiffness elements, a 50x50 mm corner or a profile pipe with a thick wall is suitable.
The surface on which the wheels will move should be non-slip. For this purpose, a grooved sheet (notch) with a thickness of at least 4 mm is used or rebar bars are welded to a smooth sheet. Support racks are made of profile pipe 80x80 mm or 100x100 mm.
Of the tools you will definitely need a welding machine (inverter capacity from 200 A), a Bulgarian with metal discs, roulette, a coal mine and a marker. Do not forget about personal protective equipment: welding mask, stings and tight clothes.
- 🛠️ Schweller 10P or 12P - for longitudinal beams (strength base).
- 🛠️ Corner 50x50x5 mm - for crossbars and edging.
- 🛠️ Sheet grooved 4 mm - for the deck of wheels.
- 🛠️ The profile pipe 80x80 mm - for support poles.
- 🛠️ Electrodes ANO-3 or UONI-13/55 - for reliable welding.
⚠️ Attention: Do not use a thin-walled profile or residues of pipes of unknown origin for load-bearing elements. When a car weighing 1.5-2 tons arrives, the dynamic load on the structure increases many times, and weak metal can burst.
Drawings and basic dimensions
Designing starts with a sketch. Standard single overpass for passenger cars has the following parameters: the total length of about 5 meters, the width of each platform (gauge) - 400 mm, the distance between the inner edges of the platforms - 800 mm. The height of the lifting of the working area is 1100 mm.
The raceway shall have a smooth angle of inclination. If you make it too steep, the car with low ground clearance will touch the "bellied" or bumper. The recommended angle of inclination is no more than 20-25 degrees. The length of acceleration of the ladder is calculated based on the height of the lift: the higher the overpass, the longer the race should be.
Calculation of the beam load
The bending moment formula is used to calculate the strength of the channel. For channel No. 10, the maximum load per span of 3 meters is about 3 tons with a uniform distribution, which gives a sufficient margin of safety for a passenger car weighing up to 2 tons, taking into account the dynamic coefficient of 1.3.
Below is a table with approximate dimensions of elements for the overpass under the passenger car:
| Element of construction | Materials | Number (s) | Length (mm) |
|---|---|---|---|
| Longitudinal beam (base) | Schweller 10P | 4 | 4000 |
| Cross-section (link) | 50x50 corner | 10 | 800 |
| Support post | Pipe 80x80 | 6 | 1100 |
| Flooring of the wheel line | Floated 4mm leaf | 2 | 4000x400 |
| Limiter (bortic) | 50x50 corner | 4 | 4000 |
Step-by-step instructions for assembling the frame
Assembly begins with the manufacture of frames for wheel lines. Two channelers are stacked parallel at a distance corresponding to the width of the track of your car. Between them with a step of 500-600 mm, crossbars are welded from the corner. This gives the design rigidity and does not allow the channelers to "screw".
Then the trails are welded to the ends of the longitudinal beams. They can be folded on hinges to save space in the garage when the overpass is not in use. In the lowered state, the ladder should lie tightly on the ground, and in the raised state it should form a single plane with the working zone.
The next step is to install the support racks. They are welded at the angles of the structure and in the middle of the span. To increase stability, the racks from below are connected with each other by lintels, forming a rigid spatial frame. All welds must be boiled on both sides.
☑️ Testing of the geometry of the framework
It's important to keep an eye on geometry at every stage. Distortions can lead to the fact that the car will stand crooked, which is dangerous when carrying out work. Use a building level and a long flat rack to check the planes.
Flooring and safety installation
After the assembly of the frame, we move to the flooring. The rifled sheet is painted in size and welded to the upper shelves of the channelers. Welding is better to perform points every 10-15 cm, so as not to lead the metal from overheating. If a smooth sheet is used, bars with a diameter of 6-8 mm across the movement of the wheels are necessarily welded to it.
On the outer edge of each platform, it is necessary to weld a side of 50-70 mm height from the corner. It's limiterThis will prevent the wheel from slipping off the overpass during the race or repair. The bortices should be solid, without tears.
Pay special attention to fixing the car. On the working part of the overpass (at the end of the race ladder), it is necessary to provide stops for wheels. It can be welded sections of the pipe or corner, which will not allow the car to spontaneously roll back.
⚠️ Attention: It is strictly forbidden to operate the overpass without installed stops for wheels and recoil shoes. Even on a flat floor of a garage, the car can come into motion due to vibration or accidental jolt.
Anti-corrosion protection and painting
Metal in garage conditions is subject to corrosion due to temperature and humidity changes. Before painting, it is necessary to clean all welded seams with a Bulgarian petal disc, remove slag and rust. The surface is degreased with a solvent or white spirit.
For protection, it is best to use a primer on rust, which converts the residues of oxides and creates an adhesive layer. After drying the primer, 2-3 layers of alkyd or acrylic enamel-mastics for the floor are applied. It is better to choose light (grey, white) color, so that you can see the details under the car better.
To improve safety, paint the ends of the overpass and wheel stops in a bright contrasting color (red or yellow). This will help to visually assess the boundaries of the design when reversing.
After the paint is completely dry, the overpass is ready for operation. The first few races are better done with caution, controlling the behavior of the structure and the absence of creaks or deformations.
High-quality corrosion treatment extends the life of the overpass by 10-15 years, protecting the metal from garage moisture and reagents brought on wheels.
Frequently Asked Questions (FAQ)
Do I need to concrete the base under the overpass?
Concrete is not strictly mandatory if the floor in the garage is made of a durable concrete slab. However, if the floor is made of rammed earth or asphalt, it is desirable to put concrete slabs or wide metal "fives" under the support racks to prevent pressing of the soil and distortion of the structure.
Can we make the overpass break down?
This is a great option for small garages. In this case, the connections between the racks and frames are not performed on welding, but on bolts of high strength class (not lower than 8.8). You can also make folding or removable raceways.
What is the minimum gap between the tracks?
The minimum distance between the inner edges of the platforms shall be at least 800 mm. This will ensure the arrival of most passenger cars. For SUVs with a wide track, it is better to increase the distance to 900-1000 mm.
Do I need to make lighting under the overpass?
Very desirable. In advance, provide the possibility of supplying electricity (cable channel under the floor or suspension system). For lighting, use only LED lights with a voltage of 12V or 36V and a degree of protection not lower than IP54, since working under the machine is associated with the risk of damage to the wiring.