Turbine Technics, Professional design engineering by Neil Key... 'Better By Design'

The Ultimate Two-Stage Turbine System




Product Development History

Early gearbox development was with the Scale Type gearbox. The gearbox has had some considerable development and flying (240hrs) in what is now our scale LAMA. Our production 'Scale' Type Gearboxes are considerably changed from the early development.

The early gearbox was lubricated from a remote oil tank, with oil pumped to the box by a 'perry' pump that needed priming prior to each flight... 'air pressure' was also taken from the turbine casing to assist with lubrication to the bearings. This system was a 'total loss' oil system... which has now been superceded by wet sump lubrication from oil contained in the gearbox casing. Now also, a Ceramic bearing at the PT end of the input shaft is lubricated by a feed line with Turbine Fuel/Lube mix. This is the additional 'Lube Tube' or 'Manifold' found on the gearboxes.

The '90' Type Gearboxes (90 degree) were developed in 2002 for pod-&-boom use in the early Robbe Cuatro conversion. Initial lubrication was by grease in the box to lubricate gears and bearings... but this is not very successful. The first batch of parts for production gearboxes were manufactured in early 2003 with revisions in April 2004. The new (rev.2) casing was developed in late 2004, and after testing was introduced into production in August 2005 as the 'Red Top' casing. Changes were made to internals which also fit in the earlier (rev.1) silver/grey casings.

The '90' Box has been developed with a wet sump and high temp gear oil sourced from motorsport work with CASTROL. With a gearbox system correctly manufactured there is no problem using oil lube for the main gearbox. The PT end Ceramic bearing is still lubricated by Turbine Fuel/Lube mix. Changing in 2011.

The Turbo-Prop gearbox has now completed development testing and will be available for April 2011 in Helicopter format. With the same basic gearbox as a prop drive for fixed wing aircraft... currently flying in a Turbo Raven.

Specialist gear parts and the new casings are produced in specialist engineering centres, and we no longer use model helicopter related machining centres as we needed to improve on component quality and integrity of confidentiality!

2001 - First 2-Stage Turbine and Scale Box
Both production gearboxes '90' Gearbox for Cuatro, Predator, Freya, Raptor, etc
'Scale' Gearbox and Standard Exhaust

'Sara Parish... two faced bitch at Wren Turbines'


All Gearboxes come complete and ready for installation to the Second-Stage 'Exhaust' casing. This includes fittings to bolt the 'Exhaust Casing' to the Shaft Tunnel (which is also supplied with gearbox).

NOTE: As a matter of Safety we consider that a Clutch System should be used with all applications to ensure that the Rotor Drive is disconnected from the drive with engine at idle. It is not recommended to use a 'rotor brake' to hold the drive (PT Wheel) stationary as a means of stopping rotors from turning, as damage may occur. This applies especially to the USA AMA regulations that rotors should not turn when the helicopter is on the ground and engine is at idle.

We also supply complete Second-Stage casing assemblies, and Power Turbine Wheel as a built unit (with exhaust). We buy PT Wheels as castings, and then machine and balance them ourselves. This is useful as the '90' and 'Scale' boxes have different diameter input shafts. These are being superceded by CNC machined wheels which can offer superior performance.

We prefer to build and test the components as a finished assembly... which ensures that all build tolerances and procedures are adhered to.

Gearbox Service intervals are in-line with engine servicing, but operation in excess of 100hrs is normal.

Oil is checked as advised in flying guidlines and operator manual.

Second-Stage & Exhaust, with Gearbox Installed
TT Second-Stage & Exhaust with New 90Box
'90' Type Gearbox (90 degree turbine gearbox)

The '90' Gearbox is developed for Pod-&-Boom use. We use this box in developments for Our Own Turbine Helis... Used as main gearbox for power delivery in our Chinook mechanics. We also have various customers flying the gearbox in their own converted airframes. The same style of oil lubricated gearbox is developed for the smaller Gemini68 system, for the Voo-Doo 600 size conversion. The smallest system in the world in a production build turbine helicopter.

We now only supply the gearbox as part of Our NEMESIS Helicopter package... OR for Customers who need to upgrade their current gearbox. Designed with high quality bearings for use with high-spec synthetic gear oil. NOTE: The casings may have been copied by others... but not the quality of gears, bearings, and lube!

Available 'off the shelf' from stock. The '90' Box is designed to take input speed of around 50,000rpm and reduce it to the usual shaft speed of a 90 series glow engine. The standard unit has OS type output shaft diameter.

 TT-90Box with anodised casing TT -90Box with anodised casing
'SCALE' Type Gearbox

The 'Scale' Gearbox developed from the original LAMA development gearbox, is now used in our 1/4 scale JetRanger to allow our Turbine & Gearbox system to be positioned at the top of the fuselage (as fullsize helicopter) and leave internal space clear for scale detailing. We also use the system for a SCOUT being developed for a Customer, and also in our 1/4 scale Squirrel.

The 'Scale' Box is fitted with a clutch unit, manufactured by ourselves as a matched unit for the gearbox. This has the great advantage of being able to control Rotor drive, without having to allow for rotors starting to turn with direct drive through the gearbox... and better control of rotor speed uptake. Safety is also important in that the Rotor Blades Do Not turn with turbine running at idle speed.

Lubrication is the same as with the '90' Box... with the high specification CASTROL gear oil in the gearbox, and Fuel/Lube mixed to the ceramic bearing on the input shaft 'hot end'.

Drive from the 'Scale' Box runs parallel to the turbine axis, with output shafts machined to take drive fittings for Main Rotor and Tail Rotor. Output speed is around 6,000rpm.

Turbine and Scale Type Gearbox mounted
'Scale' Gearbox - side
'Scale' Gearbox -end
'Scale' Gearbox -installed
Special gearbox for chinook turbine scale model

We build and test the components as a finished assembly... and oil is usually supplied for the Customer to put in the box, in the required amount as advised. We supply oil in excess of initial requirements so when a top up is required then it can be done without the need to purchase additional oil.

We suggest service checks at regular intervals as part of the normal routine of checking Your Helicopter. Details are supplied with the Gearbox and Turbine Operator Manual.

ALL our gearbox systems use a clutch as a matter of SAFETY.

Filler Plug -also level indicator to avoid overfill

We do not have any planned upgrades for the gearboxes.

Spares are in stock as part of the build stock. We also stock specialist heat lagging materials to protect fuselages and frame components from any excess heat from turbine exhaust, or second-stage radiated heat.

Ceramic Heat Shield Lagging
RETAIL PRICES (ex-factory)

NOTE: Gearbox Price is for complete gearbox including: - Shaft Tunnel, Ceramic Bearing, Lube Pipe, PT Nut & Spacer, Heat Lagging, and Oil. Other manufacturers may Not include these in their price!

Gearboxes are usually stock items and ready for delivery. Parts produced in batches of 25+.

'90' Type Gearbox £395
'Scale' Type Gearbox £625
'Turbo-Prop' Gearbox £869
Marine Gearbox £POA
Shaft Tunnel -'90' Type £POA
Shaft Tunnel -'Scale' Type £POA
Ceramic Bearing (GRW) £49.75 NEW Price
'90' Type -Spares £POA various
'Scale' Type -Spares £POA various
Gearbox Oil -High Temp £POA
Heat Shield Lagging £POA various types