Jav Jup Crankcase alloy

[Keith Clements]

This picture shows some bad Jowett quality control which will need some milling. A flap of unwanted aly partially blocking the water passage.

[Keith Clements]

Various parts were cleaned today in the parts washer, with brush and rod with some cloth attached for the oilways. See the black bit just below the crankshaft. Amazing how much black stuff comes out of those oil ways.
The rocker feed unions were loosened to make sure the cleaner and rodding was doing its job.





The block was then put into its newly made stand, bearings fitted and crankshaft laid in. The two halves were then tightened up, checking the crank still rotated at each additional torque up.
All was OK and then the camshaft was tried.


The first one was an oversize one and of course would not fit , so then I tried a new standard size. A very light tap was needed to thread it through the middle housing but it turned OK and no discernable play. But we will check that as per PJGD's treatise on camshaft bend once finally assembled.


The cam came out with the fingers and then the tie bolts were removed and the bearings checked for high spots. See Photos in TOPIC Gallery here.

[Keith Clements]

Well now satisfied with the block, I thought I would think about balancing everything. Just as a bit of an experiment, but I thought I would think about how it might be done with my lathe.
I looked at a few videos and forums, and here is a good link to show what we are aiming at.

I put the crank between centres in the lathe and put a dial gauge on a bearing. It was running true when turned by hand but fluctuated when under drive from lathe. This might be lack of balance or poor adjustment. So I then looked at how to exactly align the head and tail stock. So out with the lathe manual.

I will end up with taking all the rotating bits to a professional perhaps, but I thought I would see how far I could get. I have now to sort out a set of pistons, con rods and a flywheel that I will lighten. The kitchen scales will do for initial balancing but I will also have to set up a beam on a knife edge for accurate work.

[Keith Clements]

The balancing tolerances seem to have changed over the years , probably because they found them economically unacheivable. In 2004 they were quoting static .01gm and dynamic at .02 Oz in, with final spins in the dark because the florescent lights upset the system.(photons hitting the crank )
Now the same website is .1 gm and .2 Oz in.. All for race tune 6500 to 9000 rpm.

The intermediate tune for 6000rpm was in 2004 Dynamic Balance tolerances are set to .04 oz in and Connecting rods are weighed end to end to within .05 gram, and pistons to within .05 gram.
Now the Dynamic Balance tolerances are set to .5 oz in and Connecting rods are weighed end to end to within .05 gram, and pistons to within .75 gram

So first task will be to see how we get close to the static balance requirements.

The tables in the link do give some idea as to how the imbalance puts force on the engine mountings although lbs is not the correct unit of measurement.

[Keith Clements]

Back to play after the the Christmas break, I decided to check out the lathe.
I removed the 3 jaw chuck and fitted the morse taper centre. Then checked the run out with the dial micrometer less than .005mm (.0002"). The manual said i should make centre out of a two inch bar but I had other ideas.
I replaced the tailstock and fitted a live centre, bringing this up to check alignment by eye. A screwdriver each side of the tailstock allowed lateral movement, but there was no such adjustment for vertical which I presume has to be done with shims, either in the tailsock or headtock, but this was not in the manual.
I then used a trick with a six inch ruler which is just pinched between the two centres. When the adjustment was made the ruler would move towards the desired right angles to axis of lathe.





This is the computer enhancement to the lathe. I read the manual on the computer and operate the lathe accordingly.

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There was .01 mm (.0004 ") of runout at the tailstock end and .02mm (.0008") at the headstock end. I put this down to the centre driving the phosphur bronze bush (which might be worn at the headstock end and the center going into a thread at the tailstock end. Clearly to do any balancing work the bearing surfaces need to be used to hold the crank as is used on crank balancing machines.

[Keith Clements]

After replacing back into the depths of the cellar the two Jupiter radiators that I had got out for Chris to take up to JCS for re-coring, I set about finding a flywheel for the 'new' engine. I have seen variations on lightening the Jav and Jup flywheels , some leaving the weight on the outside, others like the one below taking the majority from the outside. Any thoughts anyone?

Four factors need to be considered.
1. Strength - we do not want the flywheel disintegrating,
2. heat disipation from clutch and possible heat cracks,
3. smoothness created by the moment of inertia, and
4. dynamic balance with crankshaft.

The latter could be very significant if you think that the pistons, conrods, crank, pulley, flywheel, clutch and all the bolts form a rotating body that is to be dynamically balanced to within say .2 oz inch when we are removing well over 600 oz inches from the flywheel!

[PJGD]

Keith,

A lighter flywheel will certainly improve the liveliness and acceleration of the engine at the expense of some smoothness of running, but is almost certainly a move in the right direction.

As with any flywheel for best static weight efficiency, you want to leave as much material near the periphery as possible and remove material closer to the hub. I have simply reduced the thickness on a flywheel in the past, but that is not the best approach.

I have attached two drawings of the flywheel; one of the standard item that I have dimensioned as best I could determine, and one with my suggestion for a lightened version. Given a bit more time, I should be able to calculate the inertia of the two versions.

Philip