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Star Tube PTO Drive Shaft — Lemon Tube Series for Agricultural & Industrial Applications in the UK
The Star Tube — also widely known as the Lemon Tube — is a critical torque-transmission profile used across the full range of PTO drive shaft assemblies. Engineered for the demanding conditions of UK farming operations, groundskeeping contractors, and light industrial machinery, this six-lobed telescoping tube profile delivers superior torque capacity, reduced backlash, and exceptional service life. Whether you are specifying components for a new tractor implement build or sourcing replacements for worn shaft assemblies across a mixed fleet, the Star Tube series provides the dimensional accuracy and material integrity that British agricultural engineers demand from a credible supplier.
What Is a Star Tube (Lemon Tube) on a PTO Drive Shaft?
The Star Tube — referred to interchangeably as the Lemon Tube in many European and UK catalogues — describes the distinctive six-lobed cross-sectional profile of the telescoping tube set that makes up the middle shaft section of a PTO drive shaft assembly. Unlike the simpler round tube or the three-lobe profile, the six-lobe star geometry dramatically increases the contact surface area between the inner and outer tube halves. This translates directly into a higher torque-carrying capacity for a given shaft diameter, lower surface contact stress, and significantly improved resistance to wear under the variable-load, high-vibration conditions typical of tractor-mounted implements operating across British fields.
The profile geometry also ensures near-zero rotational backlash when torque direction reverses — a situation that occurs constantly during PTO engagement and disengagement, gear changes, and headland turns. For implements such as rotary tillers, slurry tanker agitators, post-hole borers, and bale wrappers, this backlash control prevents the sudden shock loading that rapidly degrades universal joints and gearbox input seals. UK operators running intensive autumn cultivation schedules particularly benefit from the additional durability the Star Tube profile provides over conventional round or lemon-profile alternatives.
Why UK Engineers Specify the Star Tube Profile
Superior Torque Capacity
The six-lobe contact geometry distributes torque loads across a wider surface than three-lobe or round profiles, enabling higher peak torque ratings without increasing outer tube diameter or wall thickness.
Minimal Backlash Under Reversal
The close-tolerance lobe fit eliminates the rotational play that causes shock loading during direction changes, protecting downstream gearboxes and universal joint assemblies from premature failure.
Extended Service Life
Cold-drawn steel tube with surface treatments — including galvanising options and grease-compatible plastic liner systems — resists the abrasive contamination and moisture corrosion common in UK field conditions throughout autumn and spring workloads.
Wide Series Range
From Series 6 compact units for small utility tractors to Series 50 heavy-duty assemblies for 150hp-plus machinery, the full dimensional range covers virtually all UK tractor makes and implements without special modification.
Smooth Telescoping Action
The precision-formed lobe geometry combined with optional HDPE inner liner profiles ensures the shaft extends and retracts freely even under angular misalignment, reducing operator effort and eliminating the stick-slip that accelerates wear on round-tube designs.
Interchangeable Dimensions
All Star Tube outer and inner profiles conform to internationally recognised CE and ISO standards, ensuring compatibility with cross kits, safety guards, and yoke assemblies from all major PTO shaft manufacturers operating in the UK market.
Technical Specifications
The dimensional data below covers the full Star Tube (Lemon Tube) series range. Each series is defined by its cross kit size, outer tube profile reference, and inner tube profile reference. All measurements are in millimetres. The outer profile designations 6.03ST and 10.03ST correspond to the six-lobe outer tube sections for Series 6–9 and Series 10–50 respectively, while 6.04ST and 10.04ST denote the matching inner tube inserts. These references are consistent with the CE-marked PTO shaft catalogue and are used by UK agricultural machinery dealers and import/export distributors when placing replacement part orders.
All dimensions in mm. Outer profile designations 6.03ST / 10.03ST and inner designations 6.04ST / 10.04ST are consistent with CE-certified PTO shaft catalogues. Tolerances held to ISO 286-1 H7/h6 fit class unless otherwise specified on custom orders.
Material, Construction & Working Principle
Cold-Drawn Steel Tube Body
Both the outer and inner tube components are cold-drawn from low-alloy structural steel to achieve the tight dimensional tolerances the six-lobe star profile demands. Cold drawing increases material density at the lobe contact zones, improving hardness and wear resistance without requiring secondary heat treatment on standard-duty grades. Higher-specification grades use C45 medium-carbon steel with induction hardening on the lobe faces, pushing surface hardness to 50–56 HRC for extreme-duty applications such as heavy slurry injection equipment operating in Scottish upland conditions.
HDPE Inner Liner System
A high-density polyethylene profile liner pressed into the outer tube bore provides a permanently lubricated sliding surface for the inner tube. This eliminates metal-to-metal sliding contact under misalignment conditions, dramatically reducing the stick-slip behaviour that causes vibration-induced fatigue in the cross kits. The HDPE liner requires no field lubrication maintenance and resists contamination from soil, grit, and crop residues — a significant operational advantage during busy harvest and cultivation periods when maintenance windows are narrow.
Torque Transmission Geometry
Torque is transmitted through form-fit between the six lobes of the inner tube bearing against the six matching recesses of the outer tube. Because the contact area is approximately 40% greater per unit length than a comparable round-bore design, peak contact pressure is substantially reduced. This means the tube set can carry the same rated torque at a lower surface stress, extending the time between scheduled replacement intervals and reducing the total cost of ownership across a season of intensive cultivation, mowing, or soil conditioning work on UK farms of all scales.
Application Scenarios — Where Star Tube PTO Shafts Are Used Across the UK
The Star Tube telescoping section is found across virtually every category of tractor-powered implement in operation on British farms, groundscare estates, and light industrial sites. In arable applications across the East Anglian grain belt and the Vale of York, Series 8 and Series 9 Star Tube shafts drive rotary cultivators and power harrows from 60–100hp tractors through highly variable soil conditions. The backlash-free engagement characteristic of the six-lobe profile is particularly appreciated by operators running high-inertia implements such as large-diameter disc mowers and drum mowers on dairy farms throughout the South West and Wales, where PTO engagement speed is critical to preventing shock overload on gearbox input flanges.
Series 8–10 for 60–120hp tractors in mixed arable operations.
Series 6–8 widely used on dairy and sheep farms across Wales and Northern England.
Series 9–10 for high-torque demand during bale formation cycles.
Series 10–50 for high-volume tanker agitators and trailing-shoe injection systems.
Series 7–9 for groundscare contractors and fencing installation across the Midlands.
Series 36–42 for light industrial drive trains in food processing and aggregate handling.
Customer Success Case — Arable Farm, Lincolnshire, UK
Challenge: Repeated PTO Shaft Failures During Autumn Drilling Season
A 1,200-hectare arable operation in Lincolnshire running a fleet of five Fendt 720 tractors was experiencing recurrent tube set failures on its Horsch Joker 8RT disc cultivator during the autumn drilling window. The existing round-tube PTO shafts were failing at an average of every 180 operating hours due to lobe wear on the sliding section, requiring emergency replacement orders that disrupted the drilling programme during a narrow weather window in October.
After consulting with our UK technical sales team, the farm manager specified a direct replacement using Series 9 Star Tube assemblies with HDPE liner inserts across all five tractors. The dimensionally identical cross-kit and yoke specifications allowed a like-for-like swap in under 40 minutes per unit without any modification to the implement driveline.
Hasil: Over the following two full cultivation seasons, no tube-set failures were recorded. The estimated saving in emergency parts costs and lost working days was approximately £4,200 over 24 months compared with the previous supplier arrangement. The farm has since extended the Star Tube specification to its Lemken Heliodor power harrow fleet.
What Our Customers Say
“We ordered Series 8 Star Tube sets for our entire mower fleet in May. Delivery to our Herefordshire depot was five working days, and the dimensional accuracy was spot on — no fitting issues at all. Our workshop foreman was particularly impressed by the quality of the HDPE liner. Solid supplier.”
— James H., Farm Machinery Manager, Herefordshire Dairy Group
“As a groundscare contractor working across golf courses and country estates in Surrey, reliability is non-negotiable. The Series 7 Star Tube shafts have now completed a full season on our Amazone flail mowers with zero issues. The price was competitive and the technical data sheet answered every spec question our engineer had.”
— Rob S., Director, Precision Groundscare Ltd, Surrey
“We import and distribute agricultural parts across Scotland and the North of England. The Star Tube range has become one of our top-selling lines because the quality-to-price ratio is simply hard to match from other suppliers. Technical support from the team is responsive and the export documentation is always complete.”
— Fiona M., Purchasing Manager, Highland Agri Supplies Ltd, Inverness
Complete PTO Drive Shaft Range
The Star Tube (Lemon Tube) telescoping profile is available as part of our complete PTO drive shaft assembly range. Each series is designed for a specific torque band and implement category, and all are CE marked and manufactured to ISO 500-1 safety requirements. Choose the correct series for your tractor horsepower rating and implement driveline specification.
PTO Drive Shaft G Series
General-purpose agricultural PTO shaft with standard safety guard. Suitable for light-to-medium duty implements from 30–80hp tractors. Popular across UK smallholding and hobby farming operations.
PTO Drive Shaft S Series
Heavy-duty series with reinforced cross kits and wider safety guard. Specified for high-torque applications including large-diameter balers, heavy cultivators, and slurry injection equipment from 80–150hp tractors.
PTO Drive Shaft L Series
Extended-length configurations for wide-span implements and offset-mount applications. The L Series incorporates the same Star Tube sliding profile for consistent torque transmission through extended telescoping ranges.
PTO Drive Shaft T Series
Torque-limiter equipped series for implements sensitive to overload — ideal for spreaders, seed drills, and precision application equipment where sudden blockages could damage implement gearboxes or tractor PTOs.
Manufacturing Capability & Custom Specification Service
Our manufacturing facility operates a dedicated PTO shaft component production line covering tube cold-drawing, profile rolling, surface treatment, and assembly. With over 18 years of export experience serving UK agricultural machinery distributors, OEM implement builders, and aftermarket parts wholesalers, the facility holds ISO 9001 quality certification and produces to CE Machinery Directive 2006/42/EC standards as standard across all series. The production team works directly with UK OEM customers to develop bespoke Star Tube specifications including non-standard series dimensions, modified lobe tolerances for high-precision drivelines, custom tube lengths, and special surface coatings — including hot-dip galvanising for corrosive environments common in coastal farming operations across Norfolk, Suffolk, and the Scottish east coast.
For UK distributors and dealers seeking to stock the full series range, we offer consolidated pallet shipping with combined packaging for cross kits, tube sets, and safety guard kits. Minimum order quantities are flexible for established accounts and initial sample orders are welcomed from new UK B2B buyers who wish to verify dimensional compliance before committing to volume stock positions. All export documentation including CE declarations, material test certificates, and packing lists is provided as standard.
Pertanyaan yang Sering Diajukan
Ready to Source Star Tube PTO Drive Shaft Components for Your UK Operation?
Contact our technical sales team with your series number, quantity, and delivery location. We supply UK agricultural dealers, OEM manufacturers, and farm machinery distributors nationwide.
edit by gzl
