Stage One Kit Fitted
Posted 12 October 2015 - 02:01 AM
Just received mine back from a mini specialist - has had both bushes changed.
top hat bush (furthest from block) needs to be machined out now
the other one closest to block... is just sitting in there... falls out etc. I'm led to belive its a magical floating bush, however having dropped the whole lot off at an engine reconditioners today, the old fellow who runs the place isnt happy with this bush at all. Are they lubricated when in use, and should i go ahead with this floating setup??
Karl
Moved Into The Garage
Posted 12 October 2015 - 02:13 AM
Sounds like a 'floating bush'. They seem to be popular, but can't be used with the A+ Primary Gear. Sorry, I am not a fan of them at all. I think it was someone's solution to a problem caused by not really understanding the who process of replacing the bushes the correct way. The Primary Gear was never designed to run on a bush. From what I've seen of these bushes, they are not kind to either the crank or the gear. In any case, the front bush needs to be fitted the old fashioned way and machined to size.
I recently received a PM on this. I'll dig it out and post up.
Moved Into The Garage
Posted 12 October 2015 - 02:20 AM
OK, here's how I do them and it's also the way the factory recommends to do them;-
Primary Gear Bushes;-
I've found the last few bushes I've fitted to be a little tighter than those before, so turn up a mandrel that you can use to push them in to place, though by all accounts, this shouldn't be needed, but ,,,,,,
I machine the old ones out, but I don't go 'all the way' only make them thin enough to get something soft-ish behind them and bend the front one in and the back one (top hat) usually cracks.
Clean the tunnels of the gear, I find Paint Thinners really good for this, then don't touch them.
Freeze the new Bushes in Dry Ice (and this is also the advice of the factory). I get my Dry Ice from BOC Gases (not sure who you may have near to you), it's fairly cheap and they sell it by the KG. Depending how far away you are from your supplier, in part will determine how much you should but, just take an Esky. Of course, don't handle it with the bare hands either! The Freezer is no where near cold enough.
Bag up (separately) the bushes in plastic bags (the press seal ones are ideal) and cover them in the dry ice. The factory say 10 minutes is enough, but I leave them in for at least an hour. If you've made Mandrels, put them on ice too. While they are getting cold, I boil up some water and put the Primary Gear in that to expand it a tad.
When everything is ready to go, fit the bushes in. They should litterally drop in, need to be square on and they will be a neat fit, but as I say, the last couple I had to shove in (I do them in the press, but next to no force is needed), you need to have everything set up to go and have a couple of practice runs as you have about 30 - 40 second of working time!
I tend to do 3 or 4 primary gears at a time, to get the most from the dry ice. The others that I'm not fitting, I leave until needed, but then it's a matter of machining to size.
Once they are in, leave them overnight as a minimum to normalise.
I machine the bushes to suit the crank they are actually going on to. Factory Running Clearance is 0.003 to 0.0045". I do aim for 0.0035" but under the hat part of the back (top hat) bush, I now put a small taper on them, just so it's about 0.004" under the hat itself. Reason being, as there is more material here, and the thrust face, this part of the bush expands more (both outwards and inwards) and I've noticed on a few that they show signs of just starting to pick up but only under the hat. I like to run the tighter clearance as it gives the most bearing area to to crank then.
After machining, soak the gear in Hot (~800C) Oil (I use a 20W40 for this) for at least 4 hours, though I tend to leave them on all day! I use a small deep fryer for this, but don't let it sit on the base as with some of them will have high spot temps! I just sit them up on a couple of head studs. After the hot oil treatment DO NOT de-grease the gear ever - if you do, re-do the hot oil treatment again. I wipe down the outside of the gear with paper towel and then stand it up (in a bag usually) while I do the rest on the engine build, fit it up and only once the transfer housing is in place, then de-grease the splines for the clutch. I do that with paper towel and thinners, a few goes and you'll get it dry.
Some of this is in the Aust Factory Workshop Manual, though strangely, I've not yet read it in any UK manual.
I know doing the bushes this way is a bit of mucking about, however, I've found by doing them this way, they just don't wear. The longest running one that I've done was in a friend's Moke and that was ~25 years and ~300 000 km ago. While we haven't had it out for check, it's showing no signs of any problem.
Stage One Kit Fitted
Posted 12 October 2015 - 02:34 AM
thanks mate, i might try and get an original bush and go from there. I am running a pre A+
novice question - are the bushes provided with lubrication during use? they must be....hence the clutch oil seal....
Moved Into The Garage
Posted 12 October 2015 - 02:39 AM
novice question - are the bushes provided with lubrication during use? they must be....hence the clutch oil seal....
No. The only lubrication they ever get will be from i) the hot oil treatment and ii) the smear of oil that you'll put on the crank tail on assembly.
Stage One Kit Fitted
Posted 12 October 2015 - 02:48 AM
ok.. the floating bush isn't looking so great. Might be good if you didn't have access to machines/machinist etc. But the tophat bush needs to be machined regardless...
Edited by karlnz, 12 October 2015 - 02:49 AM.
Gearbox Guru
Posted 12 October 2015 - 09:23 AM
novice question - are the bushes provided with lubrication during use? they must be....hence the clutch oil seal....
No. The only lubrication they ever get will be from i) the hot oil treatment and ii) the smear of oil that you'll put on the crank tail on assembly.
and all the hot oil which is being thrown about the transfer case and works it's way between the primary gear and the thrust washer, and the holes around the primary gear just behind the oil seal...
Moved Into The Garage
Posted 12 October 2015 - 09:36 AM
novice question - are the bushes provided with lubrication during use? they must be....hence the clutch oil seal....
No. The only lubrication they ever get will be from i) the hot oil treatment and ii) the smear of oil that you'll put on the crank tail on assembly.
and all the hot oil which is being thrown about the transfer case and works it's way between the primary gear and the thrust washer, and the holes around the primary gear just behind the oil seal...
Sorry, but I'd beg to differ on that.
There's no oil feed in to the gear and given that the bushes are on the inside of it, with it spinning, Oil can't work it's way in, centrifugal force sees to that! The holes that are in the gear are there as vent holes. Maybe just after a run, a drop or two of Oil may find it's way in, but at best, that's about it.
If Oil was to work it's way in, then given there is no internal seal, we'd all have slipping clutches in short time.
<Edit: It took BMC Engineers some time to resolve the issue of finding a 'dry run' bush for this job, as you'd know, the early ones were pressure fed. Why? Because no Oil 'works' it's way in. When they eventually found the right material, they did away with the Oil feed as they are dry run bushes>
Edited by Moke Spider, 12 October 2015 - 09:42 AM.
Moved Into The Garage
Posted 12 October 2015 - 10:04 AM
The Bushes are made from a Trade Marked material known as 'Deva', I think back in the day BMC started using it, it was owned by GKN, but these days, Federal Mogul own the rights to it.
Some basic facts about Deva as a bearing material;-
Where to use deva.metal®
deva.metal® is a self-lubricating bearing material manufactured by advanced powder metallurgy. It is fully compacted, unlike oil-impregnated porous bronze materials that are weak by comparison.
deva.metal® is provided with an evenly distributed solid lubricant throughout its metallic matrix.
deva.metal®, which is suitable for dry running at slow sliding speeds and high loads:
Installation
The recommended method for installing bushes is freeze fitting.
Tolerances
Other installation tolerances are possible provided that a safe fit in the housing and the necessary running clearance are maintained.
http://www.deva.de/e...ange/deva-metal
<Edit: New Genuine Primary gear with the Deva Bush;-
PRIMARY GEAR GENUINE 850 998 1100 PRE A PLUS
http://www.minispare...|Back to search >
Edited by Moke Spider, 12 October 2015 - 10:10 AM.
Gearbox Guru
Posted 12 October 2015 - 10:21 AM
Super Mini Mad
Posted 12 October 2015 - 10:30 AM
Moke Spider said : No. The only lubrication they ever get will be from i) the hot oil treatment and ii) the smear of oil that you'll put on the crank tail on assembly.
The Bushes are made from a Trade Marked material known as 'Deva', I think back in the day BMC started using it, it was owned by GKN, but these days, Federal Mogul own the rights to it.
Some basic facts about Deva as a bearing material;-
Where to use deva.metal®
deva.metal® is a self-lubricating bearing material manufactured by advanced powder metallurgy. It is fully compacted, unlike oil-impregnated porous bronze materials that are weak by comparison.
deva.metal® is provided with an evenly distributed solid lubricant throughout its metallic matrix.
deva.metal®, which is suitable for dry running at slow sliding speeds and high loads:
- has high resistance to temperature and corrosion.
- will tolerate contamination and edge pressures.
- can be easily machined if required.
Having just been through all of this on a A+ 1293cc build I'm now very confused..........
So on the one hand I realise immersing it in a bath of hot oil for a week (sic) won't do the bearing any harm, it seems that if it's "genuine" Deva material it will make no difference either ??
Phil.
Edited by phil hill, 12 October 2015 - 10:31 AM.
Moved Into The Garage
Posted 12 October 2015 - 11:09 AM
Moke Spider said : No. The only lubrication they ever get will be from i) the hot oil treatment and ii) the smear of oil that you'll put on the crank tail on assembly.
The Bushes are made from a Trade Marked material known as 'Deva', I think back in the day BMC started using it, it was owned by GKN, but these days, Federal Mogul own the rights to it.
Some basic facts about Deva as a bearing material;-
Where to use deva.metal®
deva.metal® is a self-lubricating bearing material manufactured by advanced powder metallurgy. It is fully compacted, unlike oil-impregnated porous bronze materials that are weak by comparison.
deva.metal® is provided with an evenly distributed solid lubricant throughout its metallic matrix.
deva.metal®, which is suitable for dry running at slow sliding speeds and high loads:
- has high resistance to temperature and corrosion.
- will tolerate contamination and edge pressures.
- can be easily machined if required.
Having just been through all of this on a A+ 1293cc build I'm now very confused..........
So on the one hand I realise immersing it in a bath of hot oil for a week (sic) won't do the bearing any harm, it seems that if it's "genuine" Deva material it will make no difference either ??
Phil.
Phil,
From their technical manual;-
Material structure
Solid lubricants used It is additionally possible to apply an initial surface film
to support running-in phases in which the running
conditions are purely dry. The thickness of the running in-
film is not considered in any bushings bore tolerance
because it will be consumed during the running-in period.
Where used with conventional lubricants, the graphite containing
deva.bm sliding layer can be impregnated with oil.
<Edit:A couple of things they conveniently neglect to add is that there are many grades of Deva material. The type used in the Primary gear Bushes doesn't release lubricant when cool / cold. If unsure on that, sit an old bush on some paper for a week, see how much lubricant comes out, then warm it and sit it there for an hour,>
Also, following machining, no matter how good the finish is done, the peaks left from machining tend to be folded over, in doing so, 'seals' materials like these that are loaded lubricant, to initially they can (and often do) Pick up. Loading with conventional oils generally prevents this and by doing them hot, helps the peaks (or paws) relax and open up.
As I mentioned up ^^^^ I been doing them this way a long time and I'm yet to wear one out. I was taught much of this by Borg Warner Transmissions.
Edited by Moke Spider, 12 October 2015 - 11:12 AM.
Well I'll be buggered if I can find it
Posted 12 October 2015 - 12:39 PM
just take an Esky.
Translation: just take a coolbox 
Well I'll be buggered if I can find it
Posted 12 October 2015 - 12:53 PM
I have to say, I built my box to Spider's spec and, apart from second gear when the engine is cold, it is dreamy.
Stage One Kit Fitted
Posted 12 October 2015 - 08:23 PM
really appreciate this discussion
with regards to the top hat bush i have been specifically told to have it honed out to size, surely this will preserve the integrity of its lubrication releasing properties?
on that note, if you heat them up and leave them on paper for an hour, will you really see some sort of lubrication released???
here's a link to the floating bush, better description than minispares
http://www.minimania...--Full-Floating
doesnt actually say what its made of???
im pretty torn on what to do - use it or not???
my engine man is a bit gutted, he's put a lot of love into it all, i think he'd be dissapointed if i ignored his advice and used the floating bush
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