Javelin/Jupiter oil pump

[MichaelHoyle]

Hello everyone
I'm puzzling over what is the function of the chamfers on the Jupiter/Javelin oil pump gears and why they should be fitted at the lower ends of their spindles as in my Maintenance manual page 30.
The only reason for them that I can think of is that they are an identification so that gears will be refitted in a similar way as they were before dismantling.
However, if that were the case I would have expected them to be fitted at the upper ends of the shafts so that the snap ring on the lower end of the drive shaft had a decent bearing area in the right place (ie near the shaft) rather than at its extreme edge.
Having looked inside two oil pumps I found that in both cases the chamfer was at the upper end as I would expect.
I know that my grey matter does not function these days as well as it used to, so what have I missed?

Also does anyone know of a supplier of these square section snap rings/circlips (50670) as mine were already fairly sloppy on their shafts and have rubbed on the side of the bore in the base. They can be squeezed to the right size but appear to be quite soft and will not return to an acceptable diameter when carefully fitted over the shaft. Having seen these I am reluctant to refit a used one if I can get a new one. I have tried various local suppliers and some manufacturers to no avail.

Best wishes
Mike Hoyle

[PJGD]

A good point Mike; I had not noticed that statement in the manual before and I am not sure why that requirement appears important enough to show up as an instruction.

I can almost understand it in the case of the idler gear insofar that the gear rotates on the stationary spindle and thus needs adequate lubrication in the bore, and the chamfer may assist the oil to get into the clearance. With respect to the driven shaft, the square section circlip is essential because it is the only thing that holds the shaft in place by resisting the reaction of the drive gear which otherwise would pull the shaft out of the pump. Fortunately, it is a static force in the sense that there is no relative motion between the gear and the shaft since they are keyed together and hence in theory, no wear. Nevertheless it is essential that the circlip retains the shaft to the trapped gear securely.

As for the driven gear, it may be that the chamfer helps to direct the oil up the shaft to the point where it rotates within the pump body, where again lubrication is needed. I am not sure that it is essential to use a square section circlip, which as you point out are not very common. The important dimensions are the ID (or groove diameter) and the thickness (or groove height). The installed OD of the circlip is around 0.58" while the recess in which it sits in the pump end cover is 0.625" diameter, so there is some room for increase in circlip OD.

Bottom line: try to find an available external circlip that meets the dimensional criteria, and report back what you found (part number, etc.) so that it helps other club members in the future, and then reassemble your pump as the manual suggests.

Philip Dingle

[MichaelHoyle]

Thanks for your thoughts Philip
I did not think about idler shaft lubrication as I assumed there would always be a pressure drop across the gears which would help enough oil to flow up the little channel in the base and up the shaft as plenty comes out of the drive gear nozzle. Maybe it does need some help, but why both gears?

I have also tried to get round section snap rings, in the only suitable inch size which I can find listed (wire dia 0.059, ID 0.458), but with no luck either.

I have no drawing so I don't know the original diameter of the groove or whether mine is worn through rotation of snap rings over the years but neither the nearest listed square or round section ring will grip my groove when the ring is closed (usually I think there would be 0.006/7 interference for an external snap ring of this size) so these rings will always be able to move sideways and around a little when fitted to my groove, making (nominally) the effective diameter about 0.610 for the square section and 0.600 for the round section rings within a thou or so which leaves a fairly small clearance for the square section ring considering that the base is not positively located on the body. Mine can certainly move sideways quite a bit with bolts loosely in place.

That suggests that a round section ring might be good and I have heard of people using them, except that (including the .003 reduction in nominal 'thickness' of the round ring) it can rise some way inside the chamfer giving a little more free vertical play when starting up but maybe helping it to stay concentric. I guess that with the relatively small amount of use which our car will get this movement will not cause too much of a wear problem on the woodruff key.

In case I could not find a new snap ring I made a round section ring from a piece of coil spring. The wire diameter was a little bigger at 0.070 which easily went into the groove. This gave me about 0.008 vertical play. It grips the shaft at present, maybe not all round, giving an OD of under 0.600 which should be OK but the wire is not as springy as a snap ring so I'm wondering if it may slowly open up. I may be able to find better springs to play with. The story continues and its amazing how interesting such a small thing can be.

Mike

[David Morris]

Hi Michael,

Have you tried JCS? If they cannot help, can I suggest Simply Bearings on 01942 269837. Their stock list seems to show mostly round section rings, but worth a try?

I realise that you probably already know this, but we recently had a problem with a Javelin oil pump. We rebuilt one and fitted it in high hopes. However, what we omitted to do was to check and calibrate the oil relief valve fitted to the pump. When we reached to stage of initially running the engine in the car, this pump, unknown to us, had a stuck oil pressure relief valve.

Goodness knows what pressure it generated, but it managed to blow the gaskets on the filter and the dreaded Timing Rear Cover, as well as bursting the external oil transfer pipe! On stripping the pump, we found the valve seized and just that little bit of rust in the wrong place had caused us an awful lot of trouble! John Airey has made up a calibrating rig for the valve which allows you to set up the relief pressure off the engine, so it might be worth giving him a call?

All the best,

David

[Srenner]

Slightly on-topic: Snap rings or circlips are manufactured by stamping, so there is a rounded side where the die pushes to start the cut and a sharp side where the die cuts the material. The sharp side ALWAYS has to face away from the thrust face so that the sharp edge has a grip on the locating groove. If the rounded side is faced outermost, the thrusting force might cause the rounded edge to climb out of the groove.

[MichaelHoyle]

Just picked up the last two replies

David
Thanks for your reply. Yes, JCS was my first try and I have tried Simply Bearings and several other bearing shops and a couple of manufacturers, no luck in this size. I need an old fashioned shop which keep odds and ends in the back or who are willing to ask around and find them somewhere but 'No demand so no chance' was one reply.
I have made up a test rig for the relief valve, Just would like the right snap ring and some explanation about why the driven gear needs to have its chamfer at the lower end which seems wrong for taking the upward thrust on the drive shaft.

Sorry you have had such trouble with your pump, If John Airey has rebuilt his pump he may have some clues, I will try him.

Srenner
Thanks for that, its very much on topic. I have come across this situation on small stampings but too long ago for me to have remembered. Just need to get the right ring and I will put it on in the right direction. Guess you don't have a theory about the chamfer or you would have said. Your point here makes me even less keen on having the chamfer downwards as this will also tend to try to ease the snap ring out as the force will be right at the outer edge of the ring.

[PJGD]

I have two oil pumps on my workbench at present, one of which is apart. From this disassembled pump, I can confirm that the spindle bore of both gears have a chamfer at both ends, but only the bottom of the driven-by-the-engine but driving-the-idler gear has the large chamfer. After taking dimensions of the parts, I made the attached dimensioned drawing.

Points to note: The retaining ring is made from square section [0.063"] wire. It does not seem very springy [highly technical term!], and when in its groove in the driving spindle, its OD appears to be smaller than the large diameter of the chamfer. It is almost as if the intent is for the chamfer to hold the ring into its groove; if so, it is not an elegant piece of engineering.

The ring appears to be similar to this WA-522 example from American Ring company [spec sheet attached], and you note that the ring is supplied in "opened" form, to be lated crimped onto the shaft. In this case, the WA-522 ring is a little too large on the OD for our purpose.

I still have no better explanation for the large chamfer required in that location other than to promote some flow of oil up the shaft. Remember that in use, the gear will be pulled up against the pump body which will make it difficult for any reasonable flow of oil to reach the spindle by that route.

Philip

[MichaelHoyle]

Hi Philip
Many thanks for all the work in measuring and drawing.

My dimensions are similar but not exactly the same. There would be tolerances and also, I guess, aftermarket parts around.

I have been able to dismantle another pump and now I have seen gears with chamfers both ends. A closer look at some of mine make me wonder if there were originally very small chamfers on those which I thought were flat and where the circlips have chewed up the ends of the gears, perhaps due to the circlips binding on the 5/8 bore, for which there is some evidence, or getting the edge crushed into the chamfer.

My shafts were both OD 0.4985, groove diameters 0.435 and 0.438/9. Chamfers on gears were within 0.572/578 and one at 0.542.(roughly, so 3rd place is not reliable as I had difficulty measuring them, only have calipers, worsening eyesight and wobbly hands - old age creeping along!)

There is a square section external snap ring in GB catalogues, but so far I have not been able to locate any. Suppliers say there is virtually no call for most inch sizes over here. It is 0.062 x 0.062 and ID 0.461. I think this theoretically just fit inside the 5/8 bore (which is near enough spot on), even with movement in the smaller groove except that the base is not positively located on the body. I will use one if I can find any. Just by chance the shaft with the smaller groove so slightly more side play has the best gear on the upper end. Such is life. I have not heard of retaining rings which need to be closed onto the shaft. Maybe for light duty?

If the ring goes very slightly up into the chamfer, this will increase the vertical play which is enough on mine already with its 'soft' square ring which is wider than the chamfer all way round as I cannot close it further due to the bit of 'springyness' left in it. I have heard of people using a round snap ring but trying this with a ring cut from a suitable ID coil spring of 0.070 wire diameter I also found more vertical play than with a 0.062 square ring and I guess that the line contact above and below the ring would increase this play over time. A smaller wire diameter ring might give flat contact with the chamfer and the groove, but with yet more vertical play so I have discounted that approach.

I can understand that a chamfer might help oil flow up the shaft of the driven gear but to get oil up the keyway of the driver to oil the top face it would also have to get past a fairly well fitting key. Having said that, both of my pump bodies show most wear above the driving gear so more lube is probably needed.

Well, I have not exercised my remaining brain cells so much for a long time so I guess it is doing me good.

Thanks again for your thoughts

Kind regards

Michael

[PJGD]

On the two pumps that I have on my bench, the vertical end float of the drive shaft is around 0.017". Because of the helical drive gear, this end float could affect ignition timing; if the timing is set with the shaft "dropped down" as it were, the timing will retard slightly when the running engine lifts the shaft to its upper position.

I would not expect to see aftermarket parts associated with the Jowett oil pump, but there are clear differences between nominally the same parts, so I think that a lot of the variation is down to suspect Jowett manufacture.

Philip

[David Kemp]

Have you thought of contacting Neil Moore in NZ? He has done a tremendous amount of work on Javelin oil pumps,
leading to the Moore improvements.

[Keith Clements]

Neil is probably at home twidling his thumbs as the NZ rally is cancelled.

[David Kemp]

Neil is not twiddling his thumbs. He is building me an oil pump and finding me a good oil pan.

[MichaelHoyle]

Thanks folks, I have sent Neil an email.