Our Complete Guide to Specifying Trailer Cranes
This guide explains everything you need to know about specifying a Penny Engineering trailer-mounted crane, from design considerations to the information we require and how we help you get the right solution for your needs.
This page is a guidance document for Penny Engineering products only. For full regulatory detail, always refer to the original HSE and DVSA documentation.
Trailer Mounted Cranes: An Overview
Fitting a crane on a trailer can be an effective way to handle loads while keeping your towing vehicle free to carry its full payload. Trailer cranes are often used where lifting is required intermittently or where flexibility across vehicles and sites is important.
Penny Engineering is a leading provider of trailer-mounted cranes for a wide range of sectors, including rail, recovery, utilities, industrial pumping, and forestry. With safety at the forefront of everything we do, we guarantee that no unfit or untested trailer crane will leave our facility.
Specifying a Trailer Crane
Because trailers are not originally designed to carry cranes, correct specification is critical. Stability, weight distribution, and towing limits must all be assessed together to ensure the crane is safe both in use and on the road.
In most cases, the safest and most efficient solution is to use the smallest, lightest crane that can comfortably handle the task. Overspecifying a crane can reduce payload, increase stability challenges, and limit your choice of trailer and tow vehicle.
When specifying a trailer-mounted crane, you should first consider:
- What is being lifted or moved, including weight and dimensions
- How far the load needs to be lifted from the crane base
- How frequently lifting will take place
- Where the crane will be used and how it will be operated
Once these requirements are clear, the trailer and tow vehicle can be assessed as part of a complete system.
Choosing the Right Trailer
Once you understand what you need to lift, the next step is selecting a suitable trailer. All calculations must include the weight of the crane system and mounting frame, as well as the intended payload.
Key trailer considerations include:
- Overall trailer size and usable deck space
- Maximum permissible laden weight (MAM)
- Number of axles (multi axle trailers improve stability but are more sensitive to hitch height)
- Whether the trailer is braked
- Maximum permissible nose weight (the lowest value between the trailer and towing vehicle always applies)
- Hitch height and compatibility with the towing vehicle
Incorrect nose weight is a common issue (this value, “S”, can be found on the trailer data plate), particularly when cranes are mounted at the front of a trailer. Exceeding limits can make the trailer unsafe and illegal to tow.
Assessing Your Tow Vehicle
Your tow vehicle places further limits on your trailer crane specification. Manufacturer data is essential and can usually be found on the vehicle load plate or VIN plate.
You should confirm:
- The maximum combined mass of the vehicle and trailer
- The vehicle’s maximum towing capacity
- The maximum permitted loading on the vehicle tow bar (often 80kg-150kg)
- The maximum permitted nose weight from the trailer that the vehicle tow bar can handle (often under 100kg)
- Tow ball height when the vehicle is laden
UK and EU regulations require the tow ball height to be between 350mm and 420mm when loaded. This is especially important for multi-axle trailers, which must sit level so each axle carries its share of the load.
Factors to be Considered When Mounting the Crane
Fitting a crane on a trailer presents a unique set of design challenges that directly influence performance, compliance, and long-term usability, from managing nose weight to ensuring safe lifting and operation.
Trailers are designed to have a small nose weight when empty for stability. Adding a crane, particularly at the front, can easily push this beyond permitted limits for both the trailer hitch and the towing vehicle. As per UK law, the nose weight MUST be below 150kgs at all times.
Possible solutions include rear mounting, central mounting, or counterbalancing. Counterweights can be effective but reduce payload and increase cost, so they are not always the preferred option.
A trailer crane must never rely on the hitch or jockey wheel for stability. These components are not designed for lifting loads.
Most installations use:
- Two stabiliser legs alongside the crane
- Two additional support legs at the opposite end of the trailer
In some cases, additional ballast beneath the trailer floor may be required to achieve acceptable stability. This will affect both payload and cost.
Power requirements vary significantly by crane size:
- Smaller cranes (up to ~1.0 tonne): Can be powered more easily by the tow vehicle battery due to lower energy demand.
- Larger electric cranes: Can draw over 200 amps at peak load, requiring long cable runs with high energy consumption (a second deep-cycle battery must be considered here).
- Petrol-powered pump: Often the most practical option for larger cranes, although some electrical power (typically from the tow vehicle) will be needed for safety circuits.
Where possible, we can design trailer crane systems with onboard batteries to allow limited operation without the tow vehicle connected.
The operator must always be positioned in a safe zone, clear of the load and crane boom. Mechanical stops can be fitted to limit crane movement and prevent operation into unsafe areas. Understanding where and how the crane will be used helps us design appropriate controls and safety features.
Information We Need to Specify Your Trailer Crane
To ensure the crane, trailer, and tow vehicle work safely as a complete system, we need accurate information. These details allow us to specify the correct trailer crane and confirm the installation will be compliant.
- What is being lifted and how heavy is it?
- What are the load’s overall dimensions?
- What lifting radius is required from the crane base?
- How frequently will lifts take place (duty cycle)?
- How do you intend to power the crane? (Vehicle batteries are not suitable for high or frequent use.)
- Where would you like the crane to be positioned on the trailer? (Larger cranes are often not suitable for front mounting.)
- Where will the operator stand when using the crane?
- What is the make and model of the trailer?
- What are the trailer’s overall dimensions and, if available, its centre of gravity?
- How many axles does the trailer have?
- What is the trailer’s empty weight and maximum load capacity
- What is the nose weight when empty, and what is the maximum permissible nose weight?
- What is the hitch height?
- Does the trailer have front and rear drop-down support legs for loading?
- Will the trailer be towed by a regular vehicle, and if so, what is it
- What is the tow ball height when the vehicle is laden?
- What is the maximum load permitted on the tow ball?
- What is the maximum permissible combined mass of the vehicle and trailer?
Need advice on fitting a crane on a trailer to enhance your lifting operations? Our team is here to help.
Get in touch with the Penny Engineering team.
Understanding Trailer Data Plates
Trailers are fitted with a data plate that sets out their legal weight limits and loading constraints. These values are used to confirm whether a trailer is being used safely and within regulations, particularly when additional equipment such as a crane is fitted.
Line 5 is extremely important, as it shows the maximum nose weight the tow hitch can safely handle. In this example, the value is 100kg. This figure is usually preceded by a “0” and is commonly referred to as the “S” value. Both may appear on the data plate.
Nose weight measurements can vary, particularly on multi-axle trailers. To obtain an accurate reading, the trailer should be level so that all axles share the load evenly. For UK and EU compliance, the tow hitch should be between 350mm and 420mm above the ground.
Lines 6 and 7 show the maximum permissible load for each axle. In this case, the trailer has two axles, each rated at 1000kg. To legally reach the trailer’s maximum all-up weight of 2000kg, care must be taken to ensure that neither axle exceeds its individual load limit.
Calculating a Vehicle’s Towing Capability
Towing capacity figures found in owner’s handbooks, manufacturer websites, or third-party sources should be treated as guidance only. The only legally valid towing capacity for your vehicle is the figure stamped on the Vehicle Identification Number (VIN) plate.
What the VIN plate typically shows:
The VIN plate displays either three or four weight figures. These are the figures used by DVSA, VOSA, and other enforcement authorities to determine whether a vehicle and trailer combination is operating within legal limits.
- ‘A’ is the Gross Vehicle Weight (GVW), also known as the Maximum Allowable Mass (MAM), including the vehicle, occupants, fuel, and payload.
- ‘B’ is the Gross Train Weight (GTW), expressing the maximum permissible weight of both the vehicle and trailer combined.
- 'C’ and ‘D’ are the maximum front and rear axle loads, respectively.
The manufacturer’s recommended maximum towing capacity is calculated by subtracting the GVW from the GTW. For example: 4200kg – 2505kg = 1695kg. This calculation assumes the vehicle is fully laden.
Note that some hybrid and battery electric vehicles cannot be fitted with towbars. In these cases, no value will be shown in position ‘B’.
This information is based on guidance from the National Trailer and Towing Association.
The manufacturer’s recommended maximum towing capacity for your vehicle is the gross vehicle weight subtracted from gross train weight. (4200kg – 2505kg = 1695Kg). This calculation is based on a fully laden vehicle. Note that some hybrid and battery vehicles cannot have towbars fitted and so no figure will be entered in position “B”.
We have used information from The National Trailer and Towing Association for this section.
Why Choose Penny Engineering for Trailer Cranes?
Maximise your vehicle’s payload with a trailer crane from Penny Engineering – easy to operate and compatible with most trailer brands. We’ll help you specify the perfect crane, trailer, and tow combination, enhancing the efficiency and safety of all your material handling operations.
What sets us apart:
- High-quality, custom-made trailer cranes built for performance, safety, and reliability
- Complete in-house service: design, manufacture, installation, and ongoing support
- Safety-led approach with rigorous testing before any system leaves our facility
- Full lifecycle support, including refurbishments, upgrades, and crane transfers
- Comprehensive servicing contracts for long-term reliability and compliance
- Sustainable business practices combined with durable products that support long service life