Concrete Vibrators

This is the first decision, and it is not about power. It is about access to electricity and how the work is done.

The electric STORM 2300 needs a 230 V supply and draws 10 A, so on a site with a distribution board, or inside a building, it is the obvious choice: 5.5 kg, no engine noise and no exhaust, which matters when pouring floors indoors. It is also modular — one drive takes different shafts and pokers.

The Power-Bar, with its Honda GX 35, needs nothing but fuel. It weighs 16 kg but is a complete portable unit with the poker on a 0.5 m hose — the operator carries it along a trench or across an open site where a cable would be the main obstruction. Rated output is up to 25 m³/h.

That short 0.5 m hose is also its limit: it will not reach the bottom of tall formwork the way a 4 m shaft on the electric drive does. It is a tool for footings, trenches and elements where the operator stands beside the concrete rather than above it.

The two speeds quoted for the electric drive describe one motor in two states: 17,500 rpm free-running and 12,000 rpm with the poker working in concrete. The second is the one doing the job — the first only tells you how much reserve the motor has before the mix pulls it down.

A poker works in a radius, not at a point. The accepted figure for effective compaction is 8–10 poker diameters: about 30–38 cm for a 38 mm head and about 38–48 cm for a 48 mm one. Insertions are spaced so those radii overlap — otherwise a band of uncompacted concrete is left between them, invisible from the outside.

Time at each point is counted in seconds, not minutes. The signal to withdraw is that air bubbles stop rising and a film of cement paste appears around the head — carrying on past that does harm, because heavy aggregate settles while paste collects at the top. That is segregation, and it shows up later as a weak, dusting surface layer.

The poker is withdrawn slowly and still running, so the hole behind it closes. Pulled out sharply, it leaves a void down its whole length.

Three things a poker is not for: moving concrete along the formwork (it separates the mix), leaning on the reinforcement (vibration through the bars loosens their bond to the concrete) and touching the formwork (it marks the face and opens the joints).

The housing is polyamide 6.6 with 30% glass fibre — a material that survives a drop off the formwork and does not conduct. Together with double insulation and an IP 34 rating, that gives a drive you can hold with a wet hand next to wet concrete, which here is a basic condition rather than a feature.

The shaft changes without tools, through a 7 mm square socket. That is the same standard used by flexible shafts from several manufacturers, so the drive is not tied to one range of shafts and swapping a worn shaft on site takes moments rather than a trip to a service centre.

The motor is single-phase with carbon brushes shielded from dust. Brushes are a consumable, and in practice it is they, not the windings, that set the first service interval.

Poker diameter follows the element, not the site

A 38 mm head passes between closely spaced bars and works in walls, columns and ring beams, where access decides. A 48 mm head has a larger radius of action and more energy, so it suits strip footings, slabs and mass elements where the thinner one would need twice as many insertions. In congested reinforcement the thicker head will not reach the bottom; in a wide footing the thinner one doubles the work.

Shaft length follows depth

The shaft has to let the poker reach the bottom while the operator stands clear of the formwork: 3 and 4 m for walls and columns, usually 2 m for footings and slabs. A longer shaft is not a safer "just in case" choice — the longer it is, the more is lost in torsion and the harder it is to handle.

Check the supply before buying electric

A 2300 W drive draws 10 A and has to get it throughout the pour. On site that means a distribution board and a cable sized for the run, not a thin extension reel — voltage drop shows up as lost revs, and lost revs mean worse compaction for the same time in the mix. Where there is no supply, the right answer is a petrol unit rather than a generator bought for one tool.

Buy drive and tooling separately for a long life

The drive never touches concrete and lasts; the shaft and poker work in the mix and wear out. That is why the STORM 2300 is sold both complete and as a bare drive, and why shafts and pokers are a category of their own.

Flexible shafts, poker heads, hoses and couplings are in vibrator shafts and poker heads. Slabs up to about 150 mm are compacted from above with vibratory screeds, and the surface is closed afterwards by power trowels. Where there is no site supply, power comes from inverter generators.