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Jan 12, 2017 5:56 pm
adamgentilli Offline
Member
Registered since: May 17, 2009
Location: -


Subject: Re: G9 gearbox
Well Bill. You are now on my shoulder! Gearbox is out and the internals look in very good order with no broken teeth or play apparent and no cracks in the casing. So I do not propose to take it all to pieces this time and will simply replace the oil seals. However, I have discovered a cracked silentbloc housing, which is now in two pieces, on the rear bearing housing. I propose to attempt a repair and have also asked LMB for the price of a new casting. Tin hat on! My question is whether I can remove the rear housing, without dismantling the internals. I do have the latest book but David is not too specific on partial repairs. It would be too much to ask that it might, having removed the speedo gubbins, just pull off with the bearing in situ. Any advice or comments gratefully received.
 

Jan 13, 2017 9:44 am
Colin M34 Offline
Member
Registered since: Dec 01, 2007
Location: Suffolk, UK


Subject: Re: G9 gearbox
Hello Adam

I suggest you have a word with Alan Brown, He still has some G9 bits and as always is very helpful.

Colin
 

Jan 13, 2017 10:40 am
adamgentilli Offline
Member
Registered since: May 17, 2009
Location: -


Subject: Re: G9 gearbox
Thanks Colin, will do.
 

Jan 13, 2017 11:28 am
bill Offline
Member
Registered since: Jun 08, 2011
Location: -


Subject: Re: G9 gearbox
For the benefit of others : - Adam, I have spoke to you but you should be ok to get the rear housing out. However, mine was very difficult. It needed a bit of heat on the aluminium housing and gentle prising with a knife edge tapped into the gap.
If you can face it, go further and inspect the bush hidden between the input shaft and the output shaft. If this does not get much lubrication it will, I think then cause the 2 shafts to "wobble" leading to possible breakage of the helical teeth.
 

Jan 14, 2017 10:12 am
Julian Offline
Member
Registered since: Dec 04, 2007
Location: Belgium


Subject: Re: G9 gearbox
Morning Adam,

My advice would be to go all the way now you are this far.
At least as far as stripping the main and input shafts.
A crack in any of these castings can be welded, I have done many but they do need carefull preparation first as they are usually a bit oil soaked.

Good luck and feel free to phone and ask anything, I know these boxes very very well.

Best regards,
Julian

+32 489712608
Julian Messent
This post has been edited 1 times. Last edit on Jan 14, 2017 10:15 am by Julian.  

Jan 14, 2017 10:56 am
adamgentilli Offline
Member
Registered since: May 17, 2009
Location: -


Subject: Re: G9 gearbox
Thank you Julian, The rear casting is now off with no problems and I will take it to a TIG welder next week. Too much mass for my Mapp gas!
The front horns were moving nicely, but only because of the input shaft movement. I shall reapply myself to that end and carry on with the full job.
 

Jan 14, 2017 11:15 am
Julian Offline
Member
Registered since: Dec 04, 2007
Location: Belgium


Subject: Re: G9 gearbox
Great Adam,

As Bill has said, the input / main shaft Spiggot bearing is very important, it should be moving on both internal and external surfaces but should have minimal play. The club have them in stock I believe, T8 and G9 use the same bearing.

Regards,
Julian
Julian Messent
 

Jan 19, 2017 10:16 am
adamgentilli Offline
Member
Registered since: May 17, 2009
Location: -


Subject: Re: G9 gearbox
Very happy to report that the gearbox is all apart and appears to be in excellent condition. No broken teeth, bronze bush fitting well, no blockages in the oil hole feeds to this and no apparent bearing wear. I guess it was well restored before my tenure! On the instructions of the previous owner, I have always filled with gear oil, perhaps this has been helpful. On dismantling I noticed that only jointing compound, no gasket, was used on the bearing holder and front/rear casting faces. Red hematite was used, I would use Blue Hylomar unless there are any other suggestions?
 

Jan 19, 2017 2:12 pm
bill Offline
Member
Registered since: Jun 08, 2011
Location: -


Subject: Re: G9 gearbox
Well done Adam !
I am sure Blue Hymolar is fine or a very good quality silicone ?
If you dont have a magnet in the drain plug now would be a good time to fit one ?
 

Jan 19, 2017 6:47 pm
Colin M34 Offline
Member
Registered since: Dec 01, 2007
Location: Suffolk, UK


Subject: Re: G9 gearbox
Regarding sealant, I quite like Wellseal and there is quite a good debate on the web at http://www.model-engineer.co.uk/forums/postings.asp?th=99081 I agree with the sentiments here.

I keep most types of sealants to hand, including the wonderful loctite pipe sealer but if in doubt, it's Wellseal for me. I like to wear thin surgical gloves when I use it and spread it around with thin plant label sticks which can be found in pound shops.

Thanks for your useful advice Julian.

Colin
 

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