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KevinH
United Kingdom
156 Posts |
 Posted - 10/04/2008 : 07:37:57
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Would anyone have any reccomendations as to the best oil to use to lubricate the gears at the rear of a Marshall blower?
I was planning to use ordinary engine oil, but have heard that auto transmission fluid offers better resistance to dilution should the seals be slightly leaky.
Thanks,
Kevin |
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George Eagle
United Kingdom
3240 Posts |
Posted - 10/04/2008 : 11:49:24
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I think most users of the Marshall feed the blower from the offside front of the cyclinder head, the plug is removed and a union fitted, coupled with a drain pipe leading down to the sump.
George |
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kimber
United Kingdom
1529 Posts |
Posted - 10/04/2008 : 17:10:47
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| You will inevitably receive a variety of answers to this question as there are several proven methods. I have used both gear oil and engine oil. The final arrangement was as described by George above with a sight glass 'drip' in the oil feed. I had no problems. I personally think that this is the best method as you can more or less forget about checking oil levels inside the (blower) gear casing. |
Edited by - kimber on 10/04/2008 17:11:16 |
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John Reid
United Kingdom
704 Posts |
Posted - 10/04/2008 : 20:51:00
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The blower manual produced by Sir George Godfrey and Partners recommends SAE 30 oil for the gears, so I guess engine oil is fine. I have also used the sight glass drip feed system described by George; works perfectly.
John R |
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Gerhard Maier
Germany
873 Posts |
Posted - 11/04/2008 : 17:12:56
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When we speak about the Marshall 85 type blower, as originally fitted to MG's pre war, we must tell apart if it is the genuine model or a nowadays copy, which are hardly to distinguish in appearance from each other.
The genuine model needs a constant supply of 5 to 8 drips of engine oil per minute.
This oil is taken from the cylinder head and is metered by a adjustable tap fitted to the front of the Marshall.
After entering, the oil is vaporized by the spinning gears, which are in the front(different to the Volumex for instance) casing of the Marshall 85.
Part of this vaporized oil reaches the rear casing through the hollow driven shaft. In the rear casing are only the two bearings, which need lubrication.
The other part of the vaporized oil is sucked into the vane compartment of the Marshall, as we donĘt have modern oil seals in the pre war type, but only a labyrinth-system, which allows to pass sufficient oil to give some lubrication, which also is important to maintain a good boost pressure.
The not used oil assembles at the bottom of the front and rear casing, from where it is sucked away by a pipe system into the big carburettor.
So with the pre-war Marshall 85 we have a "total loss system" using some drops per minute.
The "new" Marshalls (personally no experience with them) have, as far as I know, modern oil seals, and therefore, as long as the seals are doing their job, the once replenished front and rear casings, should not need a constant supply, same as with the Volumex.
So perhaps a thin gear oil is preferable to a engine oil.
Gerhard
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Amilcar John
United Kingdom
25 Posts |
Posted - 14/04/2008 : 12:06:35
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I have also heard of using racing two-stroke oil, as this does not reduce the octane of the mixture as much if it gets into the inlet (which without modern seals it inevitably will)-it seems like a sensible solution, but I haven't tried it and was advised to use engine oil by my car's previous owner -which I do.
John |
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David Allison
United Kingdom
665 Posts |
Posted - 14/04/2008 : 13:22:58
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I agree with Gerhard.
The NA still has its original meter feed from the cylinder head and collection of assorted plumbing feeding the oild between the two end casings - then the carb sucks the excess away on an open throttle.
As an aside it is also a usefull way to deter close following modern traffic - back off the throttle and then open it wide to cover the follower in a thin cloud of oil smoke - tee hee!
The NB always had gear oil in the end casing of the modern blower - this worked fine until the seals blew at Donnington - to the relief of evryones ears the big blower has now been replaced by a Volumex (I only hope it is more reliable than my old Alfasud VX) which I think uses engine oil (my Alfa did so I guess this will be the same).
As long as the blower is well lubricated I dont think you can go far wrong (Unless you have a Zoller) the blower is probably the least stressed component on the car.
Two stroke oil might work ok (Bel Ray do one which would smell nice) but like TQF will work out much more expensive than engine oil.
I dont think TQF is the right kind of lubricant (not sure where the dilution comes into it either)- engine oil is better in my opinion.
Keep it simple I always say
Regards David |
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George Eagle
United Kingdom
3240 Posts |
Posted - 14/04/2008 : 19:01:57
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From my own experience lubrication for vane blowers is a headache.
I had an original Zoller installation for the P type and I used this in the PB ARY614, now owned and raced by Mike Dowley, and I ran the bearings in it during a race at Silverstone. The oil supply was total loss and was adjusted via a sight glass, it had to be X number of drips per minute at 1000 revs. Eventually gave up and opted for a more reliable Marshall!
I sold the Zoller to someone in Germany. The only other Zoller blown P type I saw was the one owned and used by Alan Bentley.
George |
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David Allison
United Kingdom
665 Posts |
Posted - 15/04/2008 : 15:37:48
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Jean Temple runs a Zoller blown P type in VSCC sprints and hillclimbs - the car is pretty reliable.
The blower is a belt driven unit fitted under the bonnet.
The most common Zollers are on the Q and R type cars prepared by Tom Dark - both running at 25+ psi.
The biggest problem with a Zoller is getting the oiling right - too little and the blower siezes - too much and the car looks like a 2 stroke and oils plugs.
The works used to pay lots of attention to the set up on the oiling and there are all sorts of ways to set them up.
The works ran the K3 with powerplus blowers in 1933 and tales of oiled plugs were legend.
The Zoller was a later and improved design but was still short of the reliability enjoyed by cars running the simpler rootes blowers.
The Centric and Shorrock blowers used after the war were improvements of the Powerplus and Zoller designs - effectively compressors rather than "blowers".
Most modern superchargers are derived from either the roots or the centrifical (belt or exhaust driven turbo).
The rootes blowers built now are quite different to the pre-war units.
Much tighter tolerances and better seals, three, four and five bladed vanes allowing higher shaft speeds and boost output without lost efficiency.
The latest superchargers are all screw compressors (derived from compressed air pumps), these allow even higher boost and shaft speeds.
Almost all of these call for engine oil to be used to lubricate the gears and all seem to run the main casing dry.
It would appear once again that the chaps at the Abingdon factory did know what they were talking about and achieved miricles with very little in the way of resources.
Their knowlege was gained from "learning from their mistakes" so I guess they had their problems too.
Henry Stone told me that setting up the blower lubrication on a R type was done on the rolling road "the noise was ----ing murder boy!"
The critical this is to over oil and cut back a little at a time - rather than to under oil and sieze the blower.
Regards David
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MDP
United Kingdom
35 Posts |
Posted - 15/04/2008 : 16:37:55
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Tom did some mods to the Zollers last year & we got the lubrication right quite easily (running much leaner than before). Use Castrol M or R. They now run quite reliably at about 30 pounds boost.
On Volumex's I used EP80 gear oil which works fine in the sealed gear casing.
Mark |
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tholden
United Kingdom
1638 Posts |
Posted - 15/04/2008 : 16:53:18
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David you are very right about the Zoller lubrication. It is very difficult to get it right. Having spent some considerable time last year setting up an original Q with an original Zoller I know only too well the trials and tribulations of getting the oil supply right. Even with the benefit of modern plugs it was a problem so it must have been much harder in the thirties with original plugs.
A good sysyem on a J is the later Shorrock type oil tank and total loss system with the restrictor valve built in to the oil feed in the tank. This system worked extremely well on my J3 which has a Centric 240 giving up to 15lbs boost and is the same system that Colin Tieche used on his J4. I had some fun in the early days adjusting the size of the restrictor hole but once sorted the supply was fine. The only problem was when you stopped the oil in the casing tended to settle to the bottom of the blower which resulted in a good sized clowd of oil smoke on re-start. I lived with that on the basis that it proved that the supply was working well but it has created some funny moments over the years! Ever seen those films of supercharged cars at Brooklands with clowds of oil smoke pouring from their exhaust ??
All part of the fun of running a blown car.
As an aside did many people get to the Brooklands do last weekend when we had the snow ?
Terry Holden |
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