Rotax E Type Gearbox

[boleropilot]

g'day All,

 

just discovered that the C box that has been sitting in a cardboard box (attached to an old 582 - came with the aircraft) is in fact an E

 

from what I can gather they are fairly rare so I am keen to find out as much info as possible before I fit it up to my 582/99

 

in particular I would like to hear from anyone who has had anything to with the sprag clutch fitted to the E gearbox, especially the pros and cons of this system compared to the RK400 centrifugal clutch that is available as an aftermarket add-on for C gearboxes (doesn't fit E boxes)

 

already it looks like I may have some 'fiddling' to do re. connecting the radiators at the bottom due to the location of the starter motor?

 

all comments appreciated

 

regards

 

BP

 

 

[boleropilot]

seems there is virtually zero knowledge of E gearboxes and/or sprag clutches? I'm getting to the conclusion it's just a damper kind of thing and not related in any way to the RK400 centrifugal clutch

 

on another note, I will soon be bolting my 'new' 582 back together - apparently the barrel/cylinder head alignment tools cost about $150 for the pair - crikey !

 

I have been told that if the tools are not available that by bolting up the exhaust manifold nice and tight, the alignment is 'almost spot on'

 

not sure I really like the concept of 'almost spot on' in relation to something that flies (with me in it)

 

the tools in question appear to be quite small plates with lots of holes in them - if anyone can bear to part with theirs for a week or so I'd be only too happy to pay the post both ways plus whatever is regarded as a fair fee

 

BP

 

 

[fly_tornado]

I'm missing something, are parts 17 and 18 the clutch?

 

 

 

[boleropilot]

yes that's spot on m8 - # 18 consists of a heap of loose 'sprags' that are held in place by a cage and then the circlip (# 19) holds all the parts loosely inside the housing (# 17)

 

so - starter motor turns gear # 40 which turns gear # 20 but no drive will proceed past the sprag clutch until the revolutions force the sprags to expand outwards, therefore transferring drive to # 17 which then turns shaft/gear # 23 which then drives the larger gear, sending drive to the prop hub...which of course will then turn the crankshaft for starting the motor (gear # 20 rotates on bearing # 21 and must rotate the sprag cage until X revs force the sprags out to engage the sprag clutch housing # 17)

 

obviously I am no engineer ! I think I have worked out how things turn and mesh and go click and stuff but I'm not 100% sure what the damn thing does

 

from my dumbass perspective it just means that drive from the starter motor does not go to the prop hub until X amount of starter motor revs engages the sprag clutch

 

if I am right (who knows) then the benefits (or otherwise) are = you tell me !

 

btw, one thing I recall from various reading is that sprag clutches don't operate correctly when battery power is low at start-up...that makes perfect sense to me due to a resultant lack of rotating power needed to expand the sprags out enough to ensure contact with the housing # 17

 

cheers

 

BP

 

 

[Downunder]

I thought "E"'s were common. Aren't they fitted to the 582's on Airborne trikes?

 

912's also have the sprag clutch and yes, you do need a good battery and cables.

 

You want to get the starter up and running at full power as fast as possible to get the clutch engaged and not just turning/slipping on the crankshaft.

 

It is like a bearing, but turns in one direction and locks in the other.

 

It locks when the starter drives through it but spinns freely when engine runs.

 

I don't think it has anything to do with a centrifugal (prop) clutch.

 

A 912 is at least a few thousand dollars and engine removal for repair.

 

 

[fly_tornado]

doesn't the sprag clutch just extend and engage under centrifugal force, once the prop strikes the ground the centrifugal force stops and the clutch disengages?

 

 

[JimG]

The sprag clutch is just for the starter motor , has no effect of the power transmission from the engine to the prop shaft.

 

JimG

 

 

[M61A1]

Exactly, Jim. The sprag clutch is just a "one way" bearing, it doesn't need centrifugal force, turned in one direction it engages, turned the other, it disengages In the case with a starter, it allows the starter to drive the engine, but does not allow the engine to drive the starter.

 

 

[fly_tornado]

oh that is convoluted why not just use a conventional starter? its only for a 600cc two stroke

 

 

[M61A1]

You would have to ask Rotax. B andC gearboxes have no built in starter, but use a Bendix type or a pull start on the mag end. A lot of engines with an E box still have the pull start on the mag end.

 

 

[phonetic]

A general question how much power & torsion loading can a Rotax E gearbox handle ??

 

 

[Aero28]

Looks like the starter gear is permanently engaged to gear 42, unlike a conventional solinoid activated starter.?

 

 

[Downunder]

Looks like the starter gear is permanently engaged to gear 42, unlike a conventional solinoid activated starter.?

Yes, and it looks like 42 drives gear 20. These connect to the sprag clutch, 18. The clutch only engages when driven by the starter. The gears don't turn when the engine is running.