Javelin/Jupiter gearbox

[Forumadmin]

I will let those who have used the batch of crankcases outline their experiences. But it is not fair to say they were inaccurately made, but that some work was needed, just like there would be with any pair of cases.

As for the availability of good serviceable sets of cases, clutch housing and timing case, then I wish there were. Perhaps those who have them may like to put them on the market.

The JCC ones will certainly be stronger.

[PJGD]

It is quite amazing what can be done nowadays with modern machine tools. All we need is a proper CAD drawing of our crankcase and the right machine shop. . .

http://www.youtube.com/watch?v=QsmiIeAkE-o

Philip

[p.p.]

impressiv
and the price?
peter

[Edmund Nankivell]

My understanding is, with at least two of the new crankcases, the main bearing housings and the camshaft housings don't match well enough to be used without re-machining. So perhaps CNC may not be accurate enough for this application, or is it "garbage in, garbage out". Many purchasers of these crankcases have put them on the shelf as an insurance policy against future need.

[Forumadmin]

The Scottish rebuild team have detailed what had to be done on the set they used. My point was that any set of clutch housing and block halves, perhaps even if they had come out of a 'working' engine will need checking for alignment and probably will need some work. This is especially true if the set of aluminium was not the original set from the factory (and even then there are cases when the alignment was poor).
Most blocks these days will need some welding done to them and so will need line boring not only of the main bearings , but cam shaft and possibly liners as well.

The 60 year old metal may not have cracks or significant oxidisation around the water jacket to make them obviously unusable, but there may be stretching around the head faces or poor mating around the two halves caused by bad torqueing up or dirt between the faces in one of the many rebuilds the metal will have been put through.

Whilst a CNC might look easy when it is doing its final cut, getting it to that stage requires a considerable amount of programming. My guess is the cost of just using the machine for an hour that it might take to do a Javelin block would be more than the cost of the blocks JCS produced. That is without the 1000 hours it might take to get the machine to that stage which is about the same number of hours needed to create the casting molds and set up the ordinary machine tools. The drawings will exist for the blocks just made, so has anybody access to a CNC machine? Just like any machine it only does what it is told by the operator so what goes in comes out (unless there is a fault with the machine like there was when they made Jowett gearboxes)!

[Leo Bolter]

The drawings will exist for the blocks just made, so has anybody access to a CNC machine?

The answer from me is "Yes (maybe!) . . two largish CNC machines in fact".

But, I say "maybe" because they reside at the Massey University School of Engineering and Technology (SEAT) where they are usually being used for teaching . . . the thought pops up, if students were involved, crankcases may be too complicated for students to make, (although the senior students have made (full sized) robot parts).

I'll have a word with the technician to see what they do with the machines during non-term time these days and if they still take on short runs of "outside community service work" as they used to do . . . and also, hopefully, a ballpark idea of the costs involved. Tooling, drawing and programming needs to be taken into account . . .

One problem that I foresee is that as the "as cast" crankcases are in the UK, shipping to and from NZ could be expensive.

Of course someone may very well be able to make contact with Apprentice(?) Teaching Polytechs etc. over there . . . .

In closing, I would suggest that no one gets too excited . . and I'd certainly advise against holding one's breath in anticipation of this "going somewhere!!" . . . but it's a thought . . .

I have/had a image of the CNC Machines somewhere . . . but I fear that's gone missing along with the other records I left behind at SEAT when I retired

Leo.

[Chris Spencer]

My understanding of the latest method of CNC production of a known / physical patten is not that one that takes anything like 1000's of hours to programme - in fact - less than 10 hours - you however require a very good if not perfect patten - the patten is digitised automaticly by laser - any adjustments are then manually entered to the programme - the block is placed in the CNC machine - and within an hour of CNC cutting you have the final product.

[Forumadmin]

How does a laser see inside the waterways? MRI or Xrays?

[Leo Bolter]

How does a laser see inside the waterways? MRI or Xrays?

For some reason I am under the impression that there's sets of castings in the UK that require machining to complete. I'm no expert, but I would have expected that if that were so, those castings would have the waterways cast in. The rough and un-machined crankcases would then be finished in a CNC machine . . . no need for the whole caboodle to be machined from a solid block (as shown in the YouTube video - http://www.youtube.com/watch?v=QsmiIeAkE-o).

It may very well be that the finished cases made in this combination method will work out to be a similar overall price compared with using a huge block of Alloy (and using a much longer time) to machine most of it away . . . Who knows at this stage!

So to summarise: Use the old fashioned method of casting with cores where necessary and using better material than original, then use the modern CNC method to do the finishing, holes and threads etc. I assume the UK Club has the casting patterns . . .

NEW CRANKCASES 014.jpg

[Alf Heseltine]

If the re-machining of the main bearing housing makes them larger than standard, then my info. is the bearings may not be
available to use the normal oval web crankshaft.
When Jowett line-bored the 'Mains' from standard size they used thicker bearings in over-sizes & the crankcases were renumbered & stamped N/S
The bearings Jowett used were L5389/1, the white metal rear main being dropped & shim adjustable thrust fitted. If anyone knows of bearings that can be used for
a crankcase with over sized housings please let us know.

Regards, Alf.

[PJGD]

I have got a listing of all the bearing shells with sizes and materials that were in the Clevite catalogue about 8 years ago. Clevite absorbed Vandervell bearings and possibly Glacier too. Clevite is now owned by Mahle AFAIK.

The file is in my Gallery here: xls