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ags
United Kingdom
275 Posts |
 Posted - 26/11/2008 : 20:33:07
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Hi all,
Over the very near future I am going to have the front and rear housings of my PB engine machined to accept modern lip oil seals. If you want to know the reason why, then Phil B-P's account of recent running with his C-type (in the latest Bulletin) may give you a clue.
Can anyone point me at specifications and tolerances for
a. the front oil seal
b. the rear oil seal
c. the dimensions needed for the recess in the front crankcase plate for the seal around the crankshaft pulley
d. the dimensions for the seal bearing surface on the pulley itself
e. the dimensions needed for the recess in the bell housing for the seal around the flywheel flange
f. the dimensions for the seal bearing surface on the flange itself.
Dimensioned sketches or even proper drawings would be extremely welcome.
A quick look at seal specifications indicates that I shall need Viton seals (ie the red coloured polymer) to get reliability with the rubbing speed to be expected at 6000 rpm on the rear seal - Comments please, as this restricts the selection of seals and the sizes available considerably.
Over to your united brains,
Andrew Smith MMM571 |
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Bruce Sutherland
United Kingdom
1564 Posts |
Posted - 27/11/2008 : 00:07:20
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Hi Andrew,
I've yet to attend to my PB's front and rear crankshaft oil seals, so when you've digested your replies, please will you pass your conclusions on.
Regarding oil seals, I've had very good help from Simply Bearings; their website is most helpful - https://simplybearings.co.uk. I've used them extensively including my new designs for the vertical drive top and bottom seals.
PS. Thanks for the elec. power info.
Bruce. (PB0564) |
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Bob Hudson
United Kingdom
67 Posts |
Posted - 27/11/2008 : 21:02:41
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Hi Andrew
I have been using (ordinary) black rubber seals on the front and rear crankshaft oilseals on the C type and they do not last long.
I am just stripping the engine which has done about 2500 miles and
find the blower drive covered in oil which must have come thru the oilseal, which is not under normal oil pressure there. The bell housing and clutch are very oily and I am sure that is also due to oilseal problems.
I am sure I need a better material and I am sure it is vital to get the correct interference fit between the seal and the surface it runs on. Help needed from any oilseal engineers out there.
Bob |
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ags
United Kingdom
275 Posts |
Posted - 27/11/2008 : 23:41:38
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Thanks Bob,
You have confirmed that I do need the higher specification seals, especially if you check the lip edges of the old seals when you have extracted them. The three faults to be expected if they have been running too fast is that the lips may be a. flattened, not sharp (essentially due to partial melting as a result of frictional heat) b. show fine radial cracks from oxidative stress cracking (also due to frictional overheating) c. or if very bad, from the same cause, may show sections torn away. The frictional forces may be quite large as I have seen figures of fair fractions of an HP dissipated in one seal at our sort of sizes and revs.
However everything that I have checked says that the shaft should be made dead to the nominal seal shaft size, and that the seal engineers have initially calculated the appropriate undersize on the seal bore to give the right contact pressure. So, to answer some of my original set of questions it seems that the upper tolerance on the shaft sizes is +0 in all cases. This does leave lower shaft tolerances and the housing tolerances still unknown.
However, Bob, you could please tell me the sizes of the seals which you have used, or else manufacturers and seal numbers, as this at least will give me a start. The sizes which I think I need for the PB appear to come in a very awkward range as far as machining the bell-housing is concerned. (Yes, I know - different shaft sizes for the C and PB). For example in Viton at the rear the OD and ID of the seal needed are only combined in a seal which is too thick to go into any recess which I can see being machined out of the casting. Oh dear - why can't life be simple!
So there are three of us here who are still looking for expertise, or at least someone who has done the job successfully - Please?
More technical ramblings from
Andrew Smith MMM571 |
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Bob Hudson
United Kingdom
67 Posts |
Posted - 29/11/2008 : 20:54:41
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Hi Andrew
Engine not yet out of car,expect to have it on the bench later this week and necessary parts of to measure seals next weekend will e-mail as soon as I have details
Best Wishes
Bob
C type not running, PB in bits!! |
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John Reid
United Kingdom
704 Posts |
Posted - 30/11/2008 : 17:07:30
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Andrew,
I have found some technical information in my Pioneer Weston catalogue on the installation of oilseals, tolerances of housings, axial runout, etc, and was going to post relevant parts on the forum.
However a quick Google search showed that Pioneer Weston were taken over in November 2006 and are now part of the Dutch ERIKS Group NV. There is a link that takes you to the latest edition of the technical manual, 28 pages of useful stuff: http://oil-seals.info/en/oil-seals/brochures/oil%20seals%20technical%20manual/ERIKS%20-%20Sealing%20technology%20technical%20manual.pdf
This should be of help in answering your questions and in planning what to do, aided by Bob's practical experience. Drop me a line if you have any problem with the link.
John R
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Edited by - John Reid on 30/11/2008 17:36:34 |
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ags
United Kingdom
275 Posts |
Posted - 01/12/2008 : 19:52:52
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Thanks John,
I had already found the Eriks NV site and downloaded their Technical Manual, from where came my advice re Viton.
However, my questions were primarily inspired by doubts as to what might be possible and practicable within the constraints of our existing castings and shafts. With a bit of luck Bob will help me in this area, but I do find it strange that no one can recall the necessary figures, given that this must be a fairly common adaptation. After all seventy year old holes in the vicinity of crankshafts are most unlikely to retain their original bore dimensions and fits.
Up till now I had been running with white metal cast into and filling the gaps in my own castings (pronounced ovality at both front and rear) to give the scroll threads a chance of working with reasonable clearances. This worked for a long time with oil consumption for the engine in the 600 - 800 miles per pint region. Eventually the rear white metal ring was spun when the flywheel worked loose at Brands Hatch, since when I have not been able to find a means of successfully retaining it, giving oil consumption about 400 mpp. (I did not want to have a new ring cast in place because this would mean scrapping a nicely running set of mains with attendant expense). However a desire to stop oil getting into the clutch area and to keep the front of the engine a bit cleaner, possibly even halve the original consumption, has led to this little project.
Further contributions welcomed, and it will all be written up eventually,
More technical ramblings from
Andrew Smith MMM571 |
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bahnisch
Australia
674 Posts |
Posted - 02/12/2008 : 09:59:18
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| For what its worth, I fitted lip seals to the front and rear of my F-type crank with 100% results. Admittedly the car is really only used for touring (although it has competed at our Collingrove Vintage Hillclimb quite creditably but without major distinction!) and in any case they do not rev like the later models! From memory I had the rear "bell housing" machined to take the seal and the front housing similarly machined (both tasks quite straightforward, "clocking" off the existing apertures). |
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George Eagle
United Kingdom
3238 Posts |
Posted - 02/12/2008 : 10:48:28
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Hi all
I recently had the mains on my L2 engine white metalled by John Kirkby Engineering in Croydon. He machined the bellhousing to accept a lip seal, and similarly Peter Gregoy's workshop machined out the front housing and fitted a lip seal.
I do not have the dimensions or lip seal reference numbers but will make enquiries.
The same work was done by both parties on my NB engine and I have not experienced any problems thus far.
George |
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Drolshagen
Germany
669 Posts |
Posted - 04/12/2008 : 11:44:37
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Dear Andrew,
1. Rear Oil Seal ID 50mm OD 58 mm H 5mm
With this seal I converted my J2 engines (two) and my
L2 engine.
If you would by a new crank from PHOENIX Swindon the rear crank
flange is mashined to dia. 50 mm
2. If you have the original pulley you have to mashine the
oil return scroll down to dia 32 mm
See www.simplybearings.co.uk,you wil find under seals dia 32mm
a selektion radial seals which wil fit to the front engine plate,
32 55 10 double lip seal will be situable if you mashine the front engine plate for that size.
But check that before.
Carl |
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