Technical buying guide
How to Specify Boom Arm Length and Lane Geometry
Boom barrier arm length selection starts with the entrance layout, not the longest arm in a catalogue. The arm must cover the intended closing line while leaving vehicles enough usable space and keeping its movement clear of structures. A nominal lane width alone does not tell a supplier where the cabinet, pivot, arm tip or vehicle will actually be.
For an integrator, the useful output is a marked plan and elevation that a supplier can check against a specific barrier configuration. This guide explains what to measure, how to describe it and which assumptions to resolve before an order. It complements the broader automatic boom barrier selection guide by concentrating on physical fit.
Separate clear passage from nominal arm length
Record the usable passage at the narrowest relevant point. Measure between the actual obstructions, such as a cabinet protection island and the opposite kerb, rather than between distant lane markings. Then mark the proposed cabinet and pivot position. A drawing should make clear whether an arm dimension is measured from the pivot, from the cabinet face or between another pair of reference points.
Those references matter because nominal arm length and clear passage are not interchangeable. Cabinet setback, arm attachment and tip treatment can affect the relationship. Ask the supplier to identify the reference points on its drawing instead of adding a general allowance yourself. Do not shorten an arm or move a cabinet in the field without checking the approved configuration and installation instructions.
| Survey item | What to record | Why it changes the selection |
|---|---|---|
| Clear passage | Narrowest usable opening and its reference points | Establishes the space available to vehicles |
| Closing line | Exact position where the lowered arm crosses the route | Locates the equipment relative to stopping vehicles |
| Cabinet footprint | Body, foundation, protection and service access | Prevents the equipment occupying needed passage space |
| Pivot and tip | Proposed axis and end position on the plan | Allows the supplier to confirm required reach |
| Levels and slope | Road levels across and along the lane | Helps review lowered-arm clearance and installation position |
| Overhead envelope | Beams, ducts, signs, cables and canopies | Determines whether the full movement fits |
Keep the original measurements and the proposed arrangement on separate drawing layers or clearly distinguish them with notes. This prevents a provisional cabinet position from being mistaken for an existing site constraint.
Check the vehicle path before fixing the cabinet
A vehicle approaching around a bend may need more room than the same vehicle travelling straight. Use the site’s actual vehicle mix: passenger cars, vans, delivery trucks, coaches or vehicles towing trailers. Ask the project designer to check swept paths where turning or overhang matters. A photograph of a parked car between two kerbs cannot establish that a truck can negotiate the entrance.
Plot where drivers stop and where they interact with a reader, ticket device or intercom. They should be able to reach the equipment from the intended stopping position without a late steering correction. Keep the equipment location, barrier closing line and detection layout coordinated. Moving one device after installation can invalidate the assumptions made for the others.
At logistics sites, distinguish the driver’s cab position from the rest of a long vehicle. Confirm whether the route is one-way, reversible or shared and how queued vehicles will be held. Our Logistics and Warehouse Access solution covers the operating context; the lane drawing still needs the site’s own vehicle and turning information.
Review the whole movement, not just the closed position
An arm that fits across the lane when horizontal may hit a low beam as it rises. Record an elevation through the actual pivot position, including overhead services and any nearby opening door or sign. Check both the open position and the path between open and closed. Allow the manufacturer or qualified designer to define the required clearances for the selected model.
A folding arm may be worth evaluating where headroom is limited, but it introduces a joint and a different movement envelope. Specify where that joint would sit relative to the ceiling and lane. The straight arm versus folding arm guide explains that choice. Neither an advertised folded height nor a generic garage clearance is a substitute for the actual installation drawing.
For a straight arrangement, compare the measured opening with the relevant Straight Arm Barrier Gates product page and request the drawing for the offered configuration. This article does not establish a maximum Zibor arm length or a universal clearance value.
Keep arm configuration and drive configuration together
Length is only one part of the moving assembly. The arm profile, fitted lights, hanging elements, support arrangement and other accessories may change the manufacturer’s selection and balancing requirements. State every proposed item in the RFQ. Treat a plain arm and an arm carrying additional equipment as different configurations until the supplier confirms otherwise.
Manufacturer instructions illustrate why this matters. FAAC’s B680H balancing guidance uses configuration-dependent balancing tables and control settings. That is an example of model-specific instructions, not a setup procedure for a Zibor barrier. Request equivalent instructions for the actual equipment being purchased and have competent personnel perform the work.
Also describe exposure to wind, rain, dust or corrosive conditions and the installation’s operating pattern. Ask for the suitability of the complete proposed assembly, including the arm and accessories. Do not infer that every arm available for one cabinet can operate at the same speed or in the same conditions.
Send a drawing pack that can be approved
Before ordering, give the supplier a compact pack containing:
- A dimensioned plan with clear passage, kerbs, islands, cabinet position and closing line.
- An elevation showing the pivot and every overhead obstruction along the movement path.
- Vehicle types, travel directions, stopping points and any swept-path review.
- Reader, ticket equipment, detection and pedestrian-route positions.
- The proposed arm profile, accessories and any required tip support.
- Site photographs, environmental conditions and installation responsibility boundaries.
Ask the supplier to return the offered model and arm configuration marked against that pack, with unknowns listed explicitly. Keep the approved drawing revision with the purchase order. If site work changes the kerb, island or canopy, reopen the fit check before installation proceeds.
The aim is a lane that works as a complete entrance. Send us the plan, elevation and vehicle mix with your enquiry; we can use them to discuss a suitable product path and identify the configuration details that still require confirmation.