Jowett's Drawing Office, divided into brilliant and not good?

[David Morris]

Hi All,
I am going to suggest what to some may seem like heresy? That the Jowett Drawing Office had at least two teams working on the Javelin, one who did some excellent design work and the other who should really have stayed at home!

These are, of course, just my personal views and presented as a talking point, somewhat tongue in cheek? First, let me suggest two design areas in the Javelin that, in my view, were really excellent areas of good design.

The first of these was the design of the Javelin steering box. Unique to the Javelin, the design was, in my view, was streets ahead of contemporary designs and, with its folded rack, out on its own in design. To my knowledge, nobody copied it? Existing in every Javelin ( and strangely not carried across to the Jupiter ), this design has stood the test of time and, I suspect, has survived probably without the majority of owners ever having the need to touch it. The design nevertheless has the ability to adjust the mesh of the pinion with the folded rack via a eccentric sleeve that has the ability to be adjusted to almost eliminate any backlash. You have to be careful that, having adjusted the central portion of the rack, it doesn’t get tight at the extremes. I wonder how many owners have felt the need to adjust theirs? This was at a time where other manufacturers were continuing with their peg and cam boxes that had a crude method of adjusting the mesh and anyway, almost by design, most of the wear was on the nut, which inherently resulted in slop. I once had a Triumph Mayflower, where the steering, however hard you tried to adjust it via the peg adjusting screw, had about 3” of slack at the steering wheel! The Jowett box, in my view and in comparison, at the time, was a really good bit of design work.

My second choice of good Jowett design was in the later camshafts, which with their adjustable peg, which varied the rotational angle, with respect to the crankshaft. This was at a time when the only method of tuning the BMC ‘A’ Series engine camshaft was by varying the width of the crude Woodruff key in the chainwheel. Jowett’s solution was nice and reliable and, once set, didn’t wear or move.

Now for my selection of Jowett ‘bloomers’ from the other end of the drawing office? First in the list has to be the stupid design of the oil feed to the filter, through the Rear Timing Cover. This was set at an angle to the top of the block, and as we know, if you cut through a vertical tube on an angle, you get an ellipse. The resultant gasket had therefore to cope with a joint on an ellipse, and this is asking a lot of a simple cork gasket. The gasket eventually hardens and leaks. They all do eventually, and we have to cope with this, in my view, stupid design. Whoever signed this off must have been ‘asleep at the wheel’? One solution that seems to work is to replace the cork gasket with ‘O’ rings. Jowett’s were, however, not blind to using ‘O’ rings, as they used them on the balance tube, buried deep inside the engine.

My second ‘bloomer’ is the water pump. This was Jowett’s first design of a water pump, as previously they had relied on thermosyphon cooling. They even described the Javelin/Jupiter engine as incorporating ‘Pump-assisted Thermosyphon Cooling’. But the design of the pump looks like an ‘add-on’ and whirrs away on top of the engine, looking like a grass mower. I suspect the engine was designed, then showed cooling problems at the prototype stage, and someone said, “ Opps, we better add a pump”, and this was duly stuck, literally, on top of the existing design. We are left with a unit that is prone to tearing away from its slender mounting stays, chews into the radiator and soon starts to leak. Predictably prone to problems!

If you need a third example, the gearbox isn’t much better. At least Jowett’s had the early ones made by a reputable company, Meadows, but who thought that vertical selector shaft running in the plain aluminium bearing holes in the gearbox case would last long, without wear, and thus creating gear selection problems? A replaceable phosphor-bronze bush might have helped here? We know from subsequent history that, once they decided to try and save money, Jowett’s thought it would be a good idea to make the gearbox for Javelins and Jupiter’s in-house. That decision cost a subsequent severe loss of consumer confidence and must have helped kill off remaining sales. I can remember discussing this decision with a Jowett technical apprentice, who was working in the factory at the time, and who spent hours trying to lap-in gears at the factory and get functioning gearboxes.

But in hindsight, these ‘individualistic characteristics’ don’t really distract from a truly innovative car, from a tiny British manufacturer. Driving a Javelin or Jupiter, compared with the ‘warmed-up’ pre-war offerings that appeared post-war from the big companies, is an experience to be savored. The way ‘she’ handles and seems so energetic and responsive, even today, brings a smile to the face of any driver!

Hope you don’t take my comments too seriously, as they are meant as a bit of Easter fun? Enjoy!

All the best,

David

[Chris Spencer]

David - I wont argue with your points but equally argue that you have missed the larger picture - That being the design of the car in relation to the bodyshell was simply years ahead of its time - of a class leading unitary structure when the vast majority of other manufactures models where still utilising the outdated separate chassis & body structure with most resembling the shape of a brick on wheels - The car was also class leading in its aerodynamics with a drag coefficient of 0.41 - well ahead of its rivals of the era - Add to the fact it was the worlds first production car with a curved glass one piece windscreen and provided for comfort again well ahead of its competitors - Not considered 'Brilliant' in my book but 'Exceptional' in design

[David Morris]

Hi Chris,

I completely agree, and yes the Javelin was totally innovative. I think the only part on the car that I have found carried over from the pre-war models, was the oil filler cap, which I think was used as a petrol filler cap on some earlier pre-war models!

My 'talking point' was my choice of a couple of less-than-ideal design areas, that perhaps should have been solved before the car became a finished design? But I realise that the design overall had to be rushed, in the fierce post-war market place in the late 1940's. The Javelin stepped into the world that eagerly looked for new ideas, and I expect Jowett's backers were eager to see the cash rolling in?

All the best and a Happy Easter,

David

[Nick Webster]

David, regarding the design of the oil filter housing. It does have some features to commend it. The ports are arranged such that the filter remains full when the engine is not running and means an oil supply is quickly circulating, which is not so on some marques. The drain, if you can get to it, works. I must admit I do wonder why, right from the start there was a pipe that meant an oil cooler was easily put into the system. Did Jowett have an early anticipation of cooling problems? Finally the thorny question of the gasket. Originally it was probably not too bad if carefully assembled but the increase in oil hole diameter was made without adding any meat to the edge of the housing and hence the gasket edge is insufficient at the point where it leaks. The O ring and aluminium gasket solution works but in its simplest form is not what one might describe as perfect engineering. Really, O rings should be supported on both inner and outer edges, or in theory they just squish inwards to the same thickness as the aluminium gasket and become ineffectual. At worst they break up and disappear down the hole! I believe some solutions use a short tube fitted into the two parts, which is better but not so easy to do.

Nick

[David Morris]

Hi Nick,

Thanks for your post, which adds good info. I think Jowett's did realise early on that the oil runs hot. I have suffered from burns to my finger from the dipstick! I know that the later oil filter housings have a provision for an oil cooler take off, but cannot remember if this was included on the earlier Volks filter RTCs?

Yes, making the 'O' ring gasket work is tricky and not easy. I seem to remember that the later Jowett engine on display at the Coventry Motor Museum has, in addition to the twin overhead camshafts, an entirely different position for the oil filter, which points downwards, similar to those on the A30/35s. This ensures it is kept full and is easy to change, which is a pig on Javelin/Jupiter engines. I still think Gerald Palmer should have spent a bit more design effort on this part of the engine. In my view, this area lets down what is still a brillant piece of early post-war design.

All the best,

David

[PJGD]

Hello Nick,

I guess that I am in partial agreement with you that in an ideal arrangement an O-ring would be supported on both sides of a groove, but I think that its use in our gasket support plate is quite acceptable if the initial crush on the O-ring is observed. After all, in our situation, the pressure is all one way (from inside to outside) and this is no different from a typical O-ring in a groove [see graphic] where the inner wall of the groove serves no real purpose unless there is oscillating pressure, i.e. suction and pressure.In our case we have no external pressure that is capable of overcoming the friction of the initial crush.

Possibly an even better solution than a conventional O-ring is a Quad seal [second graphic]

O-ring in Groove.png

[Srenner]

Hey Phillip, stumbled upon the quad seal when ordering other stuff from McMaster and have used them on the block-to-head water transfer (52072) for close to 10 years. Doing up 2 motors this summer and thought about boring a small shoulder in the oil filter base to locate the seal, but it appears a gasket might be a simpler solution.