pre war long 4 white metal big end bearings

[Dhbangham]

I am in the process of learning how to cast new white metal bearings onto my long four big end con-rods. I have found a very convincing You Tube video by an australian engineer. https://youtu.be/siTU7Xp_qHg?feature=shared "restoring Flanders 20 motor white metal bearings"
The first attempt failed because I failed to seal all the possible holes in the Jig. This forced me to "double poor" and resulted in bubble on the bottom end of the casting. I will keep you updated.

[Forumadmin]

Daniel,
Excellent. Glad part 3 did come after Part 4.

Look, listen and learn from an old school craftsmen able to make or make do anything he requires.

I wonder how many such people are left, but glad you tube has captured for posterity.

[Dhbangham]

Preciesly following the instructions given in the video link above, I beleieve that some friends and myself successfully cast a new bearing into the jowett big end. Our first attempt failed as we did not seal all the gaps in the casting jig, this force us to make a double pore, resulting in bubble and cavitation. The video link above is so good, I don't need to give instructions here. I am going to download the video for my personal archive, I suggest other people do it too, just incase it gets deleted. What I can offer is access to the tools and equipment if you want to white metal a pre-war big end yourself.
The next step is to make a jig to fit on my lathe to bore to size. I will post pictures later

[Forumadmin]

Daniel,
Did you find a source of new white metal?

[Dhbangham]

Yes, I already had enough for one, maybe two bearings. However I thought it sensible to get a good stock in hand. The only place I found who wuold reply to emails only sold it in 3KG bars. which cost me £236 by the time carraige and VAT were added. So I have plenty of spare material to sell on to fellow Jowetters. The specification I ordered is ASTM B23 which is the same as BS WR89-B. If you want your own 3KG I used; AIM Solder UK Limited
Unit 2/3 Sedgwick Road
North Luton, Ind. Estate LU4 9DT
UNITED KINGDOM
Tel: +44 1582587210

There is a German company selling it for a similar price on Ebay.

[AmilcarJohn]

Well done - that's an amazing achievement. There are few offering white metalling these days, and the price is usually very high. A friend runs plain bronze bearings on a sprint car, because of the huge cost of white metalling (it's a 5 main bearing 6 cylinder). That wouldn't work for anything more than a minimal milage, obviously, but he's had no issues for several seasons of hillclimbs.

[Dhbangham]

Preparing for Con rod machining; sanity check ... there are no official specifications for the center to center of the con rod big end to gudgeon pin. However conrods from two different prewar cars are the same length from half shell to center of gudgeon pin. When I measure from the distance from the conrod half shell to center of gaugeon, it measures 7.6196 inch, which is not a comfortable imperial number, the closest is 7 5/16, which is just over 5 thou more. so, if I add a 10 thou shim between the shells , it will bring the centers to 7 5/16. Anyone got any better information?

Having re-measured I now believe that the correct measurement is 1/16 longer making it 7 3/8th inch.

[Dhbangham]

More on shims in big end bearings. I have a report that a prewar jowett ( that has almost certainly never had its bearing changed ) did have shims between the big end shells.
Observations of bearing design. a) Looking at the second bearing in my engine, that has not melted, it has no shims, but there has been metal removed on part of the white metal on either side of the shells. See picture. This aids the spread of oil across the bearing when it passes the pressurized oil hole in the crank.
b) When looking at the shims supplied for use on Ford model A cars, there are lobs at each end of the shim, which if pressed against the crank when assembling, will also create a close oilway or gap. As the shell split passes the pressurized oil hole it spreads the oil out across the bearing (as above), but the oil is trapped by the lobs and therefore oil pressure is not lost. On the other side of the lobs, the bearing is lubricated by splashing into the gap created by the shim. This is an improvement on the design of the re-worked shells "in a)" by an earlier white metaling. As you can see from the second picture, the Ford shims are not the correct dimensions. They are not long enough and the hole is not in the right place. The ford shims are pealable in 1.5 thou layers and start at 30.5 thou thick
I suspect that it does't matter much, but


Anyone got any experience of this?

[Nick Webster]

Your mention of shims made me think of an engine I have in a commercial vehicle which is fitted with 10 thou shims between the big end caps. These are thick wall shells, which although "removable" seem to require the same attention as cast bearings when fitting. The manual makes mention that the bearings (obtained from the factory, naturally) are machined oval using shims and then 10 thou shims are used when fitting up for clearance. Perhaps this is nonsense whan applied to a Jowett engine, but may be of interest in the theory of shims, although clearances may be different of course.

Anyway, I am following your exploits with interest.

Nick

Big-End.jpg

[Dhbangham]

Interesting, I had to knock up a drawing to understand the process, see attached. It is further evidence that shims are ovality are desired attributes.

Having re-measured and allowing for shims, I am satisfied that original specification the center to center dimension of the con rod is 7 inch 3/8th
Which equals 182.42mm

[Dhbangham]

I have now completed my first bearing. The changes I made to the instructions on the auzpete youtube are: I used an old Gudgeon pin to make the post for aligning the bores of the con-rods; I used a different type of profile tool for shaping the end of the bearings; I made the end profiles by turning the con-rod around to give easy access to the end, auzpete turned both ends in one pass; I used a digital readout to make all measurements.

The biggest problems I had were a) Guessing exactly the center of the con-rod big end when mounting on the boring jig. There are no reference points once you have cast your white metal. If I was certain that my original casting core was perfectly central, then that would have made it easier. It is something I will pay more attention too next time. b) Finding the exact ends of the con rod casting, side to side. I had to assume that the Rod was central to the shells, and also that what I could see of the ends of the shells which were not covered by the white metal, were the true ends. This was tricky and I am not sure I got it correct. I am hoping that the =/- 1mm out of center will not cause a long term wear problem. c) Making the tool to created the exact profile of the convex curve at the ends of the white metal bearing was very tricky. I have little experience or practice of fine tool grinding.
The difference between "go" and "no go" when scraping the high spots is dramatic, one last scrape can make a binding bearing into a free running one.

I am still content that the bearings should have a shim between the shell and con rod.

Notes for next time; a) Before casting the white metal, I will mount the con rod and shell on the boring jig and use the tails stock center to align the bore in all directions, then mark up the jig with index points or adjustable stops so that I can be certain of the alignment once the bearings are cast. b) take measurements for the true center of the conrod, so I can machine the ends of the bearings symmetrically.

[Forumadmin]

Very interesting and glad you shared your experience on JowettTalk.

[Dhbangham]

Earlier in the post, I mentioned that I had not machined the the ends of the white metal equally at each end, to check if this was a problem, I dry assembled the conrod and crank in the crank case and discovered that the little end was only centered on the cylinder in one orientation. This lead me to look at the alignment of the big end journal with the cylinder hole and to my surprise found that the journals offset! , both being off to the middle of the crank shaft. I therefore machined the second white metal bearing with the same offset at my first one. This was not as successful and I have now discovered the con-rods are offset too. , ie with the rods laying flat and the axis horizontal, the center of the small end is off set from the center of the big end. see picture.

It now appears that I was just lucky with the first conrod and I should have machined the white metal equally on both end of the big end, then allow the offset rods to compensate for the offset crank.

[AmilcarJohn]

I had a similar issue with an Austin 7 engine, where the rods were not sitting centrally on the crank journal. I resolved by rotating the rods through 180 degrees, which must indicate some slight machining and/or crank alignment to block issue. But these are pretty low stressed engines, so not a serious issue IMHO.

[Dhbangham]

I am curious about this offset, which I don't believe is an accident. it is so symmetrical. Google searches come up with no explanation or examples.