Rotary mixer STR4

Quick Answer: The Rotary mixer STR4 is a Stuart rotator drive unit: a motor housing and an end support joined by horizontal bars, between which interchangeable drums, bottle holders or plates are mounted to turn samples end over end.

A Drive Built Around Interchangeable Holders

Unlike a rotator with a fixed disc, the STR4 is a drive. The photo shows a blue motor housing with controls, two parallel bars running out from it and a tapered end support at the far end. A holder chosen for the job is fixed between the drive and the end support, so the same motor can turn two large bottles one day and a drum full of tubes the next.

Several holders designed around the STR4 appear in this range. The drum for two 250 mL bottles turns bottles end over end; the drum bottle holder with adjustable tilt sets its drum at an angle for a rolling motion; and a vertical support plate holds a row of tubes upright on its face. Choosing the holder decides the vessel format and the mixing pattern.

Because the rotary mixer STR4 is sold as a drive, check whether a holder is included in the order you place; the title names only the drive. Speed range and maximum load also depend on the supplied unit.

Jobs for the STR4 and Its Holders

• Mixing 250 mL bottles of suspension or extraction mixture end over end
• Rolling a tilted drum of tubes for gentle, continuous blending
• Rotating tubes upright on a support plate during long incubations
• Tumbling solid samples with extraction liquid in closed bottles for leaching tests

Specifications

Care & Handling

• Fit the holder with the drive switched off and tighten every fixing before starting.
• Balance bottles and tubes across the holder; an uneven load strains the drive.
• Keep the support bars clean and dry, and wipe spills from the housing straight away.
• Run the drive at low speed first after changing holders to check alignment.

Why Choose LabEquip

University practical labs, environmental testing benches and research groups buy the STR4 when one motor needs to serve several vessel formats. The holders and the drive are listed together in General Lab Products, and a full set can be planned through the contact page.

Frequently Asked Questions

Does the STR4 come with a holder?

The title names the drive unit, and the photo shows the drive with its bars and end support but no holder fitted. Drums, bottle holders and plates are listed separately, so ask us to confirm what is included when you enquire.

How is a holder fitted?

With the drive switched off, the holder is mounted between the drive and the end support and secured with its fixings. Turn it by hand to check it clears the bars before switching on.

Which holder should I choose?

Choose by vessel and motion: a bottle drum for 250 mL bottles, a tilting drum for rolling tubes at an angle, or a vertical support plate for tubes that should tumble upright. Each holder suits one format.

Can the drive turn bottles containing solvents?

The drive only turns the holder, so the limit is the bottle and its cap. Use sealed, solvent-resistant bottles, run in a ventilated area, and keep ignition sources away from flammable contents.

Why does the holder knock or vibrate?

The load is uneven, a fixing is loose or the holder is not aligned with the end support. Stop, rebalance the vessels, tighten the fixings and restart at low speed.

How is the drive cleaned?

Unplug it, remove the holder and wipe the housing and bars with a damp cloth and mild detergent. Dry the bars before refitting holders so they do not corrode or slip.

Last Updated: September 2026