[thegasguy]

I have one of the orange coloured B and C lightweight alternators on my D117 Jodel, it's a C90-14F engine.
It functions perfectly,no oil leak from accessory case or odd noises coming from it and it's bolted on firmly.
However we found today that if you push and pull on the case then it ' rocks' slightly.
It may be failed bearings, if so - has anyone changed them
or had this done in the UK?
If it's something else, any ideas?

[riverrock]

I think these guys are the UK distributor: http://sandalwoodservices.com/alternato ... -245-c.asp who have some parts available - but doesn't sound like they have what you need on their website. I don't know anything about them - worth giving them a ring to ask for advice.
I see the manufacturer does overhauls and have some other parts available to buy from the states.

[Flying_john]

The orange bit is the case top - you dont say whether its moving on the mounting plate or whether its just the orange bit that is moving. Normally these generators utilise the drive and couplings from the original engine (they are a retrofit to save weight) and so it could be the elderly parts that were on the original that have failed or are failing, or it could be the single bearing that is pressed into the main plate that is bolted onto the engine thats worn and if so it will need measuring up and a replacement sought from someone like Brammer bearings, or perhaps LAS may be able to get them from Spruce in the US.

[thegasguy]

Thanks guys, the bearing has failed and i have sourced a replacement unit.
Amazingly the gear (cog) on the end of the shaft is over £1000!
Luckily my supplier will take the old one off and fit it to the new unit.
This destroys the old unit so no money back there.
Hopefully this will bring to an end the soul destroying saga I inflicted on myself just because I wanted a bit more leg room; which led to a total panel re-build and re-wire.
Completely new brakes somehow got into the mix plus a new Avmap EFIS.
I hope it's worth it when I eventually get to fly again !

[cockney steve]

@thegasguy said

Amazingly the gear (cog) on the end of the shaft is over £1000!
Luckily my supplier will take the old one off and fit it to the new unit.
This destroys the old unit so no money back there.

I'm really struggling to make sense of this, - This drive -gear must be made of Unobtanium , If, indeed, it destroys the old "core" in the process of removal, without, itself, being damaged.
Back when Lucas alties were fitted to most UK cars, ** exchange units just lost a proportionate surcharge for a broken-off mounting-lug. they were totally uninterested in whether any part was functional.......I suspect the idea was to restrict independent rebuilders. a friend who was in that business, did well with "get a free rebuilt unit for every 3 dead-un's you hand in." - the junk pile shrunk and 20 newly- recon'd units on the shelf
Bearings are standardised, pretty-much..they are given a code- number...ie "6202" (a very common type) which embodies the outer and inner diameters,width and type, eg, ball/roller....then , sometimes, z or zz (single or double metal dust-shields) rs/ 2rs = rubber seals etc. what a lot of people don't know, is there are also tolerance-grades. IIRC, "a" is the most precision, low -play coding.
This is why the "same" bearing can be different prices from different suppliers. commonly, under 4cm od ballrace, under a tenner. taper-roller a bit dearer.
Many electric-motors in washing- machines, etc, have shrunk-on pulleys. With the right gear, these can successfully be removed, a new bearing fitted and the pulley reused. Have you asked -around, just to confirm you're not being fleeced?

[Clive Richards]

Have you tried Sandelwood Services they seem to have taken over b & c parts from air world.
I would have thought you could remove the drive assembly as I recall whey we changed from a generator this part was removed from the generator and fitted to the alternator as I think a new assembly is more than double the cost of the alternator.
Clive

[thegasguy]

Indeed the 'cog' would seem to be very expensive.
At the end of the day something is worth what you can get for it, not what it costs to make plus a bit of profit - and they have a monopoly.
Having looked at it this morning prior to parcelling it up it, and also peering at websites, it's 5 components in total- a gear wheel plus a shock absorbing coupling consisting of two 'dogs' interlocked with a bit of rubber and a locking nut.
Turning the shaft shows why a shock absorber is needed, the super strong magnets only allow rotation in 'jerks'.
As for changing the bearing ourselves, frankly I'd be too worried about the total engine destruction if it, or the drive coupling, failed later in flight.
It would drop a steel gear wheel and some marbles sized bits into and between the gears that drive the magnetos and the camshaft.
Id rather cough up a chunk of money than ride an engineless French coffin downhill.
Paying for a new unit will allow me fool myself that I've reduced that chance, by at least a little bit.

[Jodelman]

a gear wheel plus a shock absorbing coupling consisting of two 'dogs' interlocked with a bit of rubber and a locking nut.

Aircraft Spruce show the various parts here and the complete gear unit is available from LAS Aero here for £1083.75 plus VAT!

[thegasguy]

Thanks Jodelman, that is the £1000 cog I found as well.
Luckily it seems mine can be removed and re-used.
I haven't had the aeroplane that long, but I'm beginning to suspect its worth a lot more as spare parts than I paid for it !

[cockney steve]

The metal bits are unlikely to break up without warning, but the rubber cush-blocks will deteriorate with age. . Misalignment between the driving and driven-members, especially a parallel -offset can very rapidly heat and soften the rubber , which can then disintegrate. Where this is enclosed, by the time you strip it down, the rubber's cooled down and you just have a pile of apparently overstressed bits.
Well worth a modest investment in replacements.

Still curious as to why and how your old unit is damaged beyond re-use, yet the drive-assembly isn't .

[Clive Richards]

Note jodelman did give you a link to individual parts at Aircraft Spruce In case you missed his link
Clive

[thegasguy]

I saw the link, it looks as if the tiny rubber bit is still $370 .
I'm hoping mine is ok.
As for why I didn't just replace the admittedly cheap bearing?
I have been told by the (semi -retired now) agent in this country that the drive coupling has to be very carefully removed to avoid damage and he has kindly agreed to do the job for free. This is the £1000 quid bit if it goes wrong.
I felt happier having a brand new alternator unit and the coupling work done by an experienced firm.
Just personal choice really, if I do the bearing change and damage something then I could cost myself the extra £1000 - or my life maybe if the engine self destructs a few hours later.
Fingers crossed it all works out before the flying weather ends.