Fan support struts.

[Tim Neville]

I've always been of the opinion that the fan support arrangement on the Javelin is a 'winky wonky' setup. On my early (1950) Jav I have the most 'wonky' support stay fixing arrangement with the spigots and split pin. I appreciate that later types had threaded studs with Oddie nuts. Looking through the notes on this in the Jav tech guide - it says " ....Note; To allow a certain amount of flexibility on the water pump supporting stays, the Oddie nuts must not be tightened fully down." Why not? My thinking is that the whole arrangement should be more substantial and more rigid. As it is, the vibration of the stays wears away the spigots on the bearing end housing and the stay holes. Surely as long as the fan is true and well balanced, a system with no free play or flop, would be better; the length of the fan stays would provide sufficient flexing for any movement at the pump connecting hose end?
My spigots and stay holes are worn so Iam thinking of re-engineering the whole thing, any comments or ideas?

[Forumadmin]

The Jupiter arrangement is probably better; but even so needs to be made from thicker steel at the base. I cannot comment on the Javelin as mine has no mechanical fan.

[Leo Bolter]

I have noticed on many Javelins and Jupiters here in NZ and also on images of overseas cars, that the tension necessary on the "vee" belt tends to cause the water pump to lean off to one side of centre. The belt MUST slacken off and require adjustment more often when this happens, especially on a new installation, or at least until it "settles down".

To me it seems that the single stay at the front of the pump to timing cover, on the generator side is doing very little (nothing!?) to help prevent this situation from occurring.

A simple stay placed as in the images below will solve this. Please note: Because of the effective angle of the stay, the actual position of the holes in this stay are fairly critical if it is to be useful in holding the pump in line against the pull of the belt. In reality the hole centre distance will probably need to be determined for each individual engine.

A "crank" is needed at the top of the stay to give sufficient clearance between it and the belt and pump pulley. It's a good idea to incorporate appropriately longer bolts that go through the stay, so as to maintain the original depth of thread in the casings.

Another method I have heard of being utilised is to use a tight fitting stainless steel tube inside the water "in hole" of the pump body that also fits inside the water passage in the timing cover . . the usual rubber hose is still used of course! I must stress that I have NO experience with this method.



"A" is an extra stay to resist the pull of the "V" belt.



NOTE: There's a crank in the stay at it's water pump end.

Regards, Leo.

[george garside]

It has alaways puzzled me as to why the 'Heath Robinson' arrangement of the water ppump being effectively 'mounted 'on a bit of rubber tube was used on the Jav/Jup engine. Even if the water pump housing haad been flange mounted onto the engine it would have still been on the wrong end so to speak i.e. it trying to 'suck' hot water out rather than pumping cold water in. The only conclusion I have been able to draw (not confirmed by anybody or anything) is that it was originally intended to rely on thermosyphon as had all Jowetts prior to it, presumably the water pump being stuck on as an afterthought to both increase cooling & enable the fittment of a heater.

I also find it odd that the CD twin was sdesigned for t hermosyphon at a time when interior heaters ( at least as an option) were becoming quite common on most makes of vehicle.

can anybody shed any light?

george

[Forumadmin]

The designer admitted to me when I was driving him around in my Javelin that it was 'his worst bit of design'. Gerald Palmer also said that he was constrained by Jowett tradition in many design areas.

Having spent many days over the last fcouple of weeks building and rebuilding water pumps, I must say it is not the only design flaw in the cooling system.

Have a look at this is the pair of castings glued into the pump and timing cover and then bolted together to replace that rubber pipe that bends under the tension of the dynamo. http://jowett.org/jowettnet/dt/tech/mods/mods.htm

[Jack]

Just as an idea, and not knowing the detail of the problem, you can get incredibly stiff rubber water hoses which have steel wire coiled through the inside of them.

Indeed, this is the hose we have had to use for the fuel hose on the SC Rebuild, this is available in a number of sizes from a number of sources, I used Winchester Hoses to get the fuel pipe.

The stuff really is rigid as hell, you certainly couldn't bend it more than a couple of degrees, and in short lengths is probably plenty strong enough.

Jack.

[Leo Bolter]

George, you said:

"The only conclusion I have been able to draw (not confirmed by anybody or anything) is that it was originally intended to rely on thermosyphon . . . . "

That's the assumption I came to too!

Jowett's seem be at least aware of the the pathetic "design" of the problem area as mentioned in my previous post . . . and were doing something about it! Take a look at this timing cover off a 4 cylinder CD I owned at one stage.


NOTE what appears to be extra offset of the coolant pump from the engine's centreline and there's no fan shaft (an electric fan was used). There even appears to be a "real centrifugal volute" as a improvement, from the appearance of the back of the pump casting.

[TedAllen]

Interesting as I'm just putting my pump together, I might try the extra stay.
I was mistaken about the new seals I've just got, I see now that they both work on the faces of the impellor. I think I'd offered them up the wrong way round. Old age or tiredness !
One thing I've noticed is that the centre line of my engine...line from pulley nut through oil filler to centre of starter dog is about an inch towards the nearside, assuming the bonnet catch pin is central to the car.
The fan shaft runs straight and is in line with the crankcase join. Nothing odd about the engine mountings.....all standard stuff.

It doesn't seem to be any problem, though.

Ted

[Forumadmin]

Drummond also noticed this on the SC but on closer inspection with a measuring tool it was in the centre. I started spouting about layrubs needing to have about 3 degrees of misalignment to work......

[george garside]

I remember Horace Grimley telling me that at one point he was running an experimental dept Jav with several (can't remember how many) temperature guages on the dashboard with thermocouples in various places on the engine . This indicated that there were steam pockets occuring in a number of places in the water jackets whcih gave rise to overheating. I think he also talked about 'cavitation' presumably caused by the water pump sucking instead of blowing.


Has anybody tried removing the standard water pump & using an electric pump (or maybe 2 smaller ones) on the bottom hoses - possibly easier on a Jupiter with more space behind bottom of radiator.

Another , to me, inherent flaw in the javelins cooling system is that the amount of air coming in through the grille is greater than the amount that can get out behind the radiator which must reduce its cooling capacity.

IN the days of 20 mile traffic jams on the Exeter bypass I fou;nd that crawling for hours with one side of the bonnet open on a (fanless)Bradford (CC) completely eliminated any tendency to overheat as it prevented build dup of heat undr the bonnet.

george

[Alastair Gregg]

Funny you should mention this George, I was looking at Bill Lumb's Javelin over the weekend. He has fitted twin electric pumps on the "Chassis" by the hoses attached to the radiator. He has no problem with overheating, but then he also has a Nissan radiator and electric fan which takes the car a long way from standard.

I'm not trying to get all technical but as I understand cavitation, its caused by the implosion of (in this case) air as the pump forces the air into smaller and smaller places. I'm not sure the direction makes any difference unless the design is such that in one direction the route is more smooth thus allowing free flow whilst in the other direction there are places to trap the air. I suspect no matter which way the coolant flows there are lots of nooks and crannies to trap air in the Jav/Jup engine.

[Leo Bolter]

Ladies and Gentlemen.

Pertaining to CAVITATION
See http://en.wikipedia.org/wiki/Cavitation especially the section "Pumps and Propellors", for a good explanation of cavitation and it's effects.
Note that basically the point of onset of cavitation in a fluid is dependent on the fluid's vapour pressure, which in turn is influenced by the pressure and the temperature of that liquid.

Pertaining to Vehicle cooling systems.
So, from reading the above we can see that hot water will cavitate more easily, especially in a poorly designed (cooling) system, than cold water in the same situation. But, remember the small vapour bubbles which are formed in the low pressure region will very likely collapse almost immediately (be re-absorbed) when they move away from the low pressure area, and that the volume of these bubbles, while they exist, is very small in relation to the volume of coolant in the engine's system . . . In other words no huge "air" bubbles should be formed to displace coolant out of the radiator overflow. If this is happening the problem probably lies elsewhere (i.e. air being sucked in through seals, gas from combustion leaking into coolant etc.). This effect could be mistaken for localised boiling. Early stages of localised boiling with it's formation of "steam" pockets should in theory, just show as coolant displacement (and probably higher than usual top tank temperature) until there's insufficient coolant left to circulate . . then, at that stage, there'll be lots of steam!

Personally, I really don't think there's much likelihood of cavitation being a factor in our Jowett cooling systems troubles, even though the pump design is pretty crude* as is its location in the system (which leaves much to be desired) . . . at least the pressure cap should help suppress cavitaton.

By the way . . . I have "cured" a engine with what appeared to be localised boiling when towing a caravan by using "neat" propriety engine coolant . . . When sorting out troubles running a overflow tube through the firewall to a observable bottle can tell you lots too . . .

I'll be interested to hear others' thoughts on the dynamics of the fluids in a cooling system . . .

* But, I would say fairly typical of automotive coolant pumps in general.

My apologies for blathering on . . .

Leo.

[Tim Neville]

I tend to agree with Alastair that direction of flow makes little difference, after all which ever way the pump pumps, one side will be under positive pressure and the other negative. True cavitation as shown by Leo is more likely to be caused by introduced gases and possibly localised boiling. I agree that cavitation is unlikely to be of much significance. I think that turbulence and consequent poor flow in 'awkward' areas is a very significant factor in the flow through our cars system, particularly as the pump is pretty poor. Smoother, cleaner waterways throughout the system together with max possible flow rate and the later additional piping layout (getting water through the heads quicker) is I think the best answer for engines with the original pump layout. Or, of course, there are a number of ways to better engineer the whole pretty poorly designed thing, if staying original is not a priority.

[Alastair Gregg]

I realize I am at grave risk of getting carried away in the excitement of somebody agreeing with one of my "technical" observations.

Several other thoughts entered my tiny little brain regarding water pump efficiency.

1. Has anyone measured the output flow of a Jowett pump.

2. Has anyone done the calculations on bore size of the ins and outs on the Jowett system. To my untrained eye the water transfer "ducts " look to be pretty restrictive. I did read somewhere that, was it Bill Lock, had larger through holed ones. But there must be a maximum flow that the Jowett system could sustain and this will be a physical restriction.

3. If the output of the pump is (and I suspect this to be the case) only a fraction of the capacity that could be comfortably allowed through the Jowett system then if you need more flow I have heard of folks considering putting a bigger pump from an American V8 in place of the Jowett pump. Sadly I don't have any results to share with you. The support stays holding a larger pump in place would become more vital.

4. The one that has been exercising my mind has been the thought of effectively doubling a standard Jowett pump. Creating a double pump on the same shaft. Now it would either need someone who was clever enough to be able to weld Aluminium and force two pumps into a fabricated housing. I forsee sealing problems down that route, or the other option is to have two pumps on the one shaft and arrange a clever flow path combining inputs and outputs. The Jupiter lends itself more readily to this because of the Y pipe.

This latter option does at least use standard Jowett components albeit in a non standard configuration.

Probably a non starter but traveling up and down the country in a modern I have plenty of time to think of wild and wacky ideas.

Try not to laugh too loudly, underneath it all I'm quite sensitive

Yay this is my 500th post!!

[george garside]

JOwett engineering had a atest rig for testing reconditioned water pumps & somewhere in a dusty corner of my brain lurks the figure 11 galls a minute - I may well be totally wrong though!

I don't think that 'sucking harder' by doubling the water pump up in its normal position would make a world of difference, certainly not in proportion to the effort to make ssuch a set up. Forcing cold water through the water jackets with a pump on the bottom hoses seems more logical to me. I agree about th;e wateer transfer elbows - the haave always seemed to me to be a cack handed idea to put it politely.

george