Kings Langley garage meet

[Keith Clements]

Looks the right place.
https://bassetdownbalancing.com/balancing/
They do knife edging as well.

[PJGD]

EN40T was good stuff back in the day, and I suspect that it still is. I agree that materials, heat treatment and forging practice has advanced in the interim, however whether we would get those benefits in the sort of small batch that the club could justify having made is another matter.

Here is a picture of the Subaru crank for their petrol engine; note the very thin webs in comparison to the Jowett webs. I think that we are obliged to have thick webs due to the fundamental dimensions of bore spacing and bearing locations, plus being a 3-bearing crank, we have a flying web which the 5-bearing Subaru does not.

Some other points to note about the Subaru engines: Assuming that the Subaru engine rotates clockwise when viewed from the front, you can see that the crank pin oil holes break out on the leading side of the pin (as do virtually all modern engines), not on the trailing side as the Jowett crank has. Grandfield moved the breakout to the trailing side believing it to be the best location, but there is a reason that no modern engines are like that.

Also note that again like all modern engines, the Subaru diesel has graphite coated piston skirts to minimize friction, plus the skirt is heavily relieved on the sides where the gudgeon pin bore is, again for low friction.

[Keith Clements]

Thanks Philip.
The three to five bearing difference is significant as there is more unsupported mass and strain on the webs from the piston stroke.
Yes there is more space for the web in the Jowett but its thickness is huge in comparison.
Do we have an example of a more modern three bearing crank, preferably boxer?

Harry is calling Bassettdown on Monday so will see if they have relevant experience.

[Srenner]

This link displays the Repco F1 motor from the mid 60s. The unit on the left has a 1/4" thick plate visible sticking out above the cast block.
https://primotipo.files.wordpress.com/2 ... 768&h=854

I have run a 1/2" thick aluminum plate between the bottom of the block and the sump for 30 years. The concept was to stiffen the case structure and the side effect was lowering the sump to gain extra oil capacity.

The plate is held by double ended studs with a central shoulder (resembling one long stud with a washer in the middle). The plate is countersunk on the sump side to a depth matching the shoulder, a .030" flat washer and a lock washer, leaving the stud shoulder at or below the surface of the plate when tightened into place. Might get away with a thinner plate, but 1/2" was easy to source. Oil drain slots and rectangular areas for the crank throws were machined in the plate.

I have a second plate somewhere and will try to post pictures.

The sump also has a "coffee can" on the bottom. It is a well about 1.5" below the true bottom of the sump. A modified oil pickup from a 1275 A-series motor nests inside the well, as this pickup has a strainer and a large flat top, creating a baffle for the oil underneath. This position is constantly flooded; any oil motion sloshing about leaves it filled. The original Jowett baffles are in place and IIRC, I added a short baffle between the leading edges of the two longitudinal ones. Inspired by the deep sump kit for Porsche 356 motors.https://www.thesamba.com/vw/gallery/pix/594283.jpg

I will also dig out a piston for a SOHC Ford that incorporates a lot of the recent race designs.

[Nick Webster]

I'm coming in a bit late to this because I had not previously looked to find Tech bits under the heading of UK Events & Rally!

I have previously posted a bearing query in another section though this did not stimulate the debate I had hoped. I am interested to see the bearing shell photos from a little while back in this thread. These appear to be the Perkins bearings without any additional oil holes towards the end of the bearing to match with the oil hole in the block. Am I right then that the only mod therefore is the middle hole for the locating spigot? For some months now I have been contemplating that provided one has a block with the oil groove behind the bearing it might not be necessary to put extra holes in the bearings merely in order to line up with the gallery holes. JCS supply bearings drilled with 4 oil holes, presumably because they cannot be sure what kind of block they are going into. I am rather of the opinion that the less holes the stronger the shell and there are other down sides with subjecting the bearing to several machining processes. Comments on the need for the oil feed to be on the leading or trailing edge of the bearing seem to reinforce my view that the existing Perkins holes are adequate. I'm interested to hear any views.

Nick

[Srenner]

Nick:

The Jowett block comes in two flavors. The mother tunnel of the case can be smooth (early cases) or have an oil groove (later).

The original bearing had an oil grove in the bearing surface.

The case groove allows the oil to travel around the backside of the bearing.

The Perkins bearing needs to accommodate one or the other. Smooth needs the bearing to have a groove carved into it; grooved case leaves the bearing surface smooth, but large slots are machined into the mating edges so the oil enters from behind the bearing.

Pictures to come.

[Srenner]

Video of NASCAR motor build for a street car. View of underside of piston at 7:03. Note the small wrist pin and the architecture of the piston to support it. Also, almost no skirt.

At 13.29 is the roller lifter (tappet). Perhaps a version of this would be adaptable to the Jowett.

https://www.youtube.com/watch?v=W6fTZnVtMNY&t=20s

[Nick Webster]

Scott,
I am aware of all the construction variations you are describing. My question was primarily regarding the position of the oil feed holes in the bearing relative to the crankshaft and supply holes in the block. Since the position of the holes was considered and changed by Jowetts themselves in their quest for reliability, how much importance should we attach to their position these days in the light of different bearing material and improved oils?

Nick

[Keith Clements]

Some more pics as I am in discussion with Basset Balancing.

[PJGD]

Keith,
Re your post from last Saturday about other 3-bearing flat fours, the problem is that all modern engines are 5 bearing and so not directly comparable; see for example the Porsche engine here:

lenz16_01_04_Porsche_Wasserbaech_e New Porsche Boxer Turbo 4 and 6 copy.pdf

(3.43 MiB) Downloaded 19 times

An engine that is a little later (perhaps 10 to 15 years?) than the Jowett engine is the Lancia Flavia which also had a quite fat flying web:

[Keith Clements]

Those are both great inputs into the discussion and make me wonder where the Jowett engine would have gone with the same amount of development.
I think there is a danger in copying a modern crank web design based on looks without understanding the relevant differences in the Jowett set up.
The pdf article shows how so many aspects of the design are inter-related. I would only start trying to copy a three bearing crank design and ignore any 5 bearing one. I would also err on the side of caution because of the known flexibility of the block as this must put greater strain on the crankshaft.
But counter to that is that a lighter crank might reduce such stress. I say 'might' because a much deeper analysis is required. Maybe the weight makes no difference to strains if the crankshaft is balanced and the metal is taken off in the right places where it is not stressed.
You can see some knife edging (or at least change from the flat web) in the Laystall Jowett crank. You can see some interesting shapes on the Lancia where the webs are asymettric.

crank.PNG (44.49 KiB) Viewed 364 times

But this would be a massive change to the existing crank!
What I think this shows is that the dynamic balance is achieved by mass applied by opposite imbalance at each end of half the crank. This should balance out the unsupported weight of the web in the middle. The unsupported web also looks to be much thicker than those next to the main bearings suggesting it requires much more strength to withstand the twisting forces between the two big ends.
If only I had access to a CAD system.......my 1960's engineering training and aged brain cannot do all the calculations.

bal_f8.jpg (14.7 KiB) Viewed 361 times

In the attempt to reduce the offset in the plane of the pistons, the cylinders can be located on opposite sides of the crankshaft, as in the Jowett "flat twin", and use a two-throw crank so that the pistons move in opposite phase. It is not usually desirable in practice to place the two cylinders in exactly the same plane, so that there is usually a slight couple as shown but it is much less than in the side-by-side arrangement, and balance, on the whole, is fairly satisfactory.

bal_f12.jpg (18.61 KiB) Viewed 360 times

The orthodox four-in-line engine can be quite well balanced if the cranks are arranged in pairs at 180 deg., each pair being opposed to the other to cancel out the individual couples, as shown. This arrangement is sometimes termed " mirror" balance, as each half of the engine resembles a reflection of the other as seen in a mirror. If the pistons and other working parts of such an engine are of uniform mass, the engine is capable of working smoothly, and with very little vibration.
It should, however, be noted that the stiffness of the crankshaft, and of the engine structure generally, has an important bearing on the success of such engines, 'as the cancelling of the two opposed couples has a tendency to bend the crankshaft in the middle.

There are, however, other forces of the second, third and further orders where a connecting-rod of limited length is used to link reciprocating and revolving parts! This is where the art of balancing takes over.
https://en.wikipedia.org/wiki/Engine_balance

Flat-four engines typically use a left–right–right–left crankshaft configuration and have the following characteristics:

Primary imbalances are caused by the rocking couples of the opposing pistons being staggered (offset front to back). The intensity of this rocking couple is less than a straight-four engine, since the pairs of connecting rods swinging up and down move at different centre of gravity heights.
The offset distance means that the equal and opposite forces from each cylinder pair produces a rocking couple. The resulting vibration is not usually high enough to require balance shafts.
Secondary imbalances are minimal.

In this research I noted that many manufacturers label their cylinders 1 and 2 on the right and 3 and 4 on the left, rather than the Jowett way of 1 and 3 on the left and 2 and 4 on the right.

1100959.jpg (21.52 KiB) Viewed 356 times

VW FIRING ORDER.
Add to this the Jowett firing order of 1,4,2,3 which equates (when you use the VW position of cylinders) to 3,2,4,1 against the VW beetle 1,4,3,2. But also bear in mind you are looking at the VW engine usually from the rear and the Jowett from the front! Confused? Right and left in both cases are when you are looking from the rear of the car.

This firing order difference alters the order of the rocking couples generated, but I do not think their magnitude, so probably has no affect on the crankshaft design. Using the Beetle layout, the largest rocking couple on the Jowett engine is when cylinder 3 fires after cylinder 2 (or in the Jowett layout when cylinder 1 fires after cylinder 4). On the Beetle the largest rocking couple is when cylinder 4 fires after cylinder 1.

This display of different Beetle cranks shows some variation, I think mainly caused by the metal used and manufacturing technique,
https://www.coolairvw.co.uk/category/sh ... ankshafts/

[Srenner]

Piston picture: Those are cast or hypereutectic (squeeze cast not forged). That is sub-optimal for a racing motor.
Also, the rings appear tall, but it is a little hard to judge from the pictures. Thinner rings are less friction. Top ring can be as thin as 1.15mm and 2nd around 1.5mm. The oil ring would be around 3mm. Gapless style rings can be used in either 1st or 2nd to lessen blow by.

Clutch: Loads of rotating mass can be shed by going to a modern 7.25" racing clutch cover. Requires re-drilling the mounting bolt pattern and depending on stack height, might need a bobbin in addition to the throw out bearing.. This cover will allow the use of a sintered metallic disc which is the standard in most club racing. No modern racing clutch has cushioning springs.

I have to agree on being conservative. A motor development program can get expensive.

[Keith Clements]

I have just learnt this flywheel is experimental so incorporating the clutch you suggest might be sensible to do at the same time. Then maybe we see if it is possible to balance both a standard (or less lightened flywheel) and this clutch, as well as the new flywheel and racing clutch so that the two combinations can be swapped.

More research on piston and liner will be required as I hope the ones I have are matched. Swapping both over to a new piston/ liner combination is another decision that will delay the balancing!!!

[PJGD]

Keith,
To add to the confusion that you mention in your lengthy 01 December post above, I am confused about the correct firing order anyway.

I have always taken the firing order to be 1-4-2-3 and that the distributor rotates anti-clockwise when looking at it from on top (such as viewing the rotor with the cap removed).

Both you above, and the Bill Boddy/MotorSport Technical Development article, and claim that the firing order is 1-3-2-4, and the Bob Jones JCC information also claims that the distributor rotates clockwise, page 29. If it were to rotate clockwise, then 1-3-2-4 would be correct (or if one were to view the distributor from the drive dog end.

Elsewhere, JCL states that the firing order is 1-4-2-3 (Jowett Jupiter Technical Information, January 1952), as does the JCC "Technical Information for the Jowett Javelin" (Bob Jones, 2001) page 24.

So, some clarification is needed!

[Srenner]

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