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E-PROPS : Extended Hubs


E-PROPS has developed an innovative system to replace the usual spacers in aluminium (heavy, expensive and difficult to assemble) : the EXTENDED HUBS.

1- Description of the E-Props extended hub system
2- Existing extended hubs
3- Does your aircraft need an extended hub ?
4- Length of extended hub and spinners : measures
5- Special notes

1- Description of the E-Props extended hub system



In leisure aviation, there are not large series as in the automotive industry. Aircraft manufacturers are used to change somes details on their aircraft, particularly engines covers. Sometimes the engines come outside the covers, and sometimes are inside. It depends on the versions... and it is impossible for propellers manufacturers to know all versions of all aircraft.

Usually propellers manufacturers propose aluminium spacers if the engine is inside the engine covers, in order to space the propellers from the engine fairings.
The E-PROPS solution is lighter, stronger, more secure and cheaper.
For the moment, this system is available for the 3-blade tractor propellers for Rotax serie 9 engines.



presentation video

ADVANTAGES OF THE EXTENDED HUBS SYSTEM

- Weight reduction
weight of the spacer (carbon extended hub) = 3.5 gram * Se in mm (including screws)
it means 3.5 gr/mm
To be compare with 20 gr/mm of a usual aluminium spacer (with screws)
Example for the spacer of a Savannah ultralight :
- weight of an E-PROPS extended carbon hub, length 115 mm (including screws) = 0,4 kg
- weight of an usual aluminium spacer, length 115 mm (including screws) = 2,4 kg
it means a reduction of 2 kg !

- Less weight on the gear box
A too big weight hanged to the gear box is reducing its lifetime.
The heavy propellers generate a significant risk of breakage of the gear box.
Reducing the weight of the spacer allows to limit this risk.

- Lower cost
The extended hubs are at the same price as the standard hubs.
No need to buy a spacer in addition. Considerable savings !

- Less vibrations
With an extended hub, the propeller centering is direct. No need of spacers and screws stacks, which can generate vibrations.
A very simple system strongly reduces vibrations risks.

- A reliable and durable system
The E-PROPS hubs, standard or extended, are extremely strong.
Material : 100% carbon + epoxy resin high T°
Injection with RTM process (Resin Transfer Molding)
Compact hub for minimum drag and to optimize engine's cooling.
No life limitation. Recommended major periodic inspection : 2.000 hrs

- Simple assembly and reduction of the parts number

E-PROPS hubs

A : 6 Screws + 1 central nut (for the central screw of the hub)
B : 7 Nord-Lock washers
C : Flange in anodized aluminium
D : Upper Half Hub
E : Lower extended Half Hub
F : Option : 5mm counterplate to adjust the length of the hub (a 5 mm step)
G : Reducer flange (part of the engine)
H : 6 Rotax drive lugs (threaded)


3-blade propeller with extended hub : 3 blades, 2 half hubs, 1 aluminium flange, 7 Nord-Lock washers, 6 screws, 1 nut
=> It means 20 parts
3-blade propeller with aluminium spacer : 3 blades, 2 half hubs, 1 aluminium flange, 7 washers, 6 screws, 1 nut , 1 aluminium spacer, 6 drive lugs for spacer, 6 washers, 6 nuts, 6 screws and 6 washers for spacer.
=> It means 51 parts
The "Extended Hub" solution allows to reduce of 61% the number of parts necessary for the propeller's assembly.

E-PROPS hubs
hub with integrated spacer 115 mm (for Savannah, for example)
and on the right with a 250 mm spinner


2- Existing extended hubs



For the moment, this light, strong, secure and cheap solution is available for the 3-blade tractor propellers for Rotax serie 9 engines (DURANDAL range).
Lengths available : from 0 to 115 mm, on 5 mm increments

E-PROPS hubs
some examples of E-Props extended hubs


3- Does your aircraft need an extended hub ?



Sometimes it is necessary to have a spacer between the propeller and the reducer flange, whan the engine is far inside the engine cover.

It exists 3 configurations :

A) the gear box side plate is outside the engine cover
=> you don't need any spacer. Please indicate He = 0 in your order.

B) the gear box side plate is just at the edge of the engine cover
=> you don't need any spacer. A 5 mm spacer is usually enough to space the propeller from the engine cover.
A picture of your present propeller assembly, taken above the engine and from the side, could help the E-PROPS team to see if a 5 mm spacer is necessary.

C) the gear box side plate is outside the engine cover
=> you need a spacer. An extended hub as proposed by E-PROPS is a very good solution : light, strong and cheap.
To know which extended hub, please see § 4.


Please note :
If your aircraft need an extended hub and if you want a spinner, you must have a spinner assembled by front of the propeller. If your spinner is assembled between the propeller and the gear box side plate, il would not be possible to use it, because the extended hub is a one-piece carbon part, and it is prohibited to cut it (see § 5).

In this case, you have 3 solutions :
- you order a complete set : E-Props propeller + extended hub + standard spinner.
- you take a mini-spinner (diameter 130 mm), which is available for each E-Props propellers, tractor or pusher. Simple, very light and cheap solution.
- you order an E-Props with a standard hub, and you keep the aluminium spacer you already had before, and your spinner. You just have to check : first, if your spacer has a drilling patern 6M8d101,6 ("big" Rotax drilling patern), and then if your spinner is a 3-blade model. You probably woud had to adjust your own spinner, so E-PROPS does not recommended this solution.

4- Length of extended hub and spinners : measures



The thickness of the standard DURANDAL hub is 80 mm.
Then it is necessary to add the good thickness to replace a spacer.

E-PROPS hubs

To order an extended hub, you just need to take a measure. It is very simple.
Procedure :
- remove your current propeller and all its accessories, particularly the aluminium spacer if any
- put the engine cover back
- take two metal rulers : one to be put between the 2 external sides of the engine cover, the other to measure
- out the ruler 1 against the engine cover, in front of the gear box plate, where will be the propeller
- put the ruler 2 perpendicularly to the ruler 1, side which measured staying visible
- note the measure M as on the picture below
- then add between 5 mm and 10 mm to this measure M to define the thickness of the extended hub which necessary to your aircraft. 5 mm or 10 mm : it depends if you prefer to have the propeller close or far from the engine fairings. Be careful to keep enough place to dissamble the covers. See below.

E-PROPS hubs



E-PROPS STANDARD SPINNERS


The E-Props spinners are assembled on the flange of the propeller, so they are adapted to all hubs configurations.
Note that the back of the spinner arrives just in the back plane of the hub, near the blades feet.
The plate of the spinner is adjusted on the middle of the spinner.
More information on the E-Props spinners : page SPINNERS

E-PROPS hubs

The standard gap between the spinner and the engine cover is usually between 5 and 10 mm.
If you need a larger gap between the spinner and your cover, then add more mm to your M measure.

E-PROPS hubs

5- Special notes



In case of mistake on the M measure (length of the extended hub) :
- we can change the extended part of the hub
- for this, please send back to E-Props the complete propeller : the 3 blades, the 2 parts of the hub and the screws (you can keep the accessories, protractor, covers, spinner and its plate)
- please indicate the He you want
- we change the extended hub, and we balance the propeller again with the new extended hub
- cost of the change : 95 euros HT / 114 euros TTC + shipment costs (balancing and administrative costs)
- within about 1 week
- to order this change, follow this link : Extended Hub : exchange


NEVER cut an E-PROPS extended hub.
The extended hubs are designed and manufactured for a defined length.
Cut them is similar to destroy the mechanical strength of the hub. This would be very dangereous.
It is absolutely FORBIDDEN to fly with an E-PROPS extended hub which would have been cutted.

There is no risk to do this by accident : it would be very noticeable that a hub has been cutted. If the hub is cutted, it is destroyed.
If you have no the good length, please contact us to find a solution.


E-PROPS hubs
extended hub on a ROTAX's reducer with a spinner





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