From Godfrey Stewart

[Keith Clements]

Hi there
I grew up with the Jowett. My father bought it before the war and it served us well until 1964 when it was difficult to keep it going. I can well remember helping my father to remove the engine in an attempt to improve its performance.
It carried us on our holidays to both the South and East Coast. Very often if we had friends come to visit the site Father would sleep in the car. Sadly at the end it was becoming more and more unreliable, to an extent that on its last outing it returned most of the way home on one cylinder.
On another occasion in the mid 1950’s we were out on a very frosty Boxing day following the hunt when we hit a patch of ice and the car turned over on its side. Fortunately the Jowett had a sun roof and we were able to use it to get out. My mother and I were taken home by a passing motorist whilst my father with some help managed to right the car and drive it home with very little damage apart from a cut hand from the windscreen. This was the only accident I can recall having in the nearly twenty years that I travelled in it.
The other abiding memory that I have it that when father wanted to light his pipe he would ask me to hold the wheel (fortunately there was very little traffic around in those days).
Sadly I never got to drive it, I could never master double declutching.

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[Keith Clements]

What amazes me is how a car with so little power manages to tow such a large caravan!

[Tony Fearn]

Hello Godfrey,
Thanks for the post about the car that your dad and the family had. It's lovely to hear these anecdotes of Jowetteering.
It was also nice to see the long four by the side of that massive caravan. The Jowett had 17 bhp you may remember!
I had a similar car (called 'Sydney') some time ago, which my friend Bernard now has.
Best wishes,
Tony.

[Keith Clements]

Hi again
I found the comment about towing caravans. Sadly 7hp (not 17hp) probably wouldn't pull the skin of a rice pudding,
The caravans were on a caravan park and we would hire one for the factory fortnight (ie last week in July first week in August).

Thanks for the interest
Godfrey

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[Keith Clements]

You may notice a change of surname for Godfrey caused by the fact his email address was spelt Stuart and he then informed me it should be Stewart. Hopefully the two clans are not upset too much. Anyhow we look forward to more memories coming from Godfrey in the future.

Amazing how the brain plays tricks. I previously had Gavin above and this was because we have a Gavin Stewart in the club. Sorry again....

[Andrew Henshall]

Quote:

"Sadly 7hp (not 17hp) probably wouldn't pull the skin off a rice pudding."


I'm hesitant in opening this can of worms again, but here goes: RAC Rating hp vs brake horsepower (bhp)!

The Expert has spoken and declared that the Stuart Jowett is a Long Four (Saloon), and I can see that the document that Godfrey uploaded shows it was first registered in 1934. The 1934 Long Saloon had a 907.2 cc engine with an RAC rating of 7 hp. It probably produced about 17 bhp on a dyno at best. In 1937, the engine was replaced by the 946 cc engine with an RAC rating of 8 hp, which was reported to have produced a mighty 20 bhp. Given that the 1166.4 cc four cylinder engine introduced in 1936 had an RAC rating of 10 hp, and produced 32 bhp, it is strange that they weren't more popular.

The RAC rated hp figure has little connection with an engine's actual output, but it was very important, as for many years the annual car taxation was based on its RAC rating. There is a myth that the RAC rating was an arbitrary figure as the RAC formula does not take into account the engine's stroke (and thus capacity). This is not true!

In fact, the RAC formula was based on sound engineering principles and account was taken of stroke. The limiting factor in the accuracy of the RAC formula was that three specific assumptions, which never varied, were made about the engine and the conditions under which it operated. As the formula was used for taxation purposes for many years, these assumptions were not updated and soon quietly forgotten about.

The RAC formula states:

RAC Rated hp = (D**2 x n)/2.5 where D = the diameter of the cylinder in inches [1" = 25.4 mm], and n = the number of cylinders

The RAC formula is in fact derived from general principles.

The indicated brake horsepower per cylinder can be calculated if the mean effective pressure in the cylinder is known. This pressure is the mean of the varying pressures acting on the piston. Being the mean value, it is that notional unvarying pressure which acts on the piston during the entire power stroke. The three assumptions which did not change year after year, whatever the engine under consideration, are:

1. Mechanical efficiency at Vm is 75%
2. The mean effective pressure Pm is 90lb/sq.in
3. The mean piston speed Vm is 1,000 ft/min, i.e. 2 x L x N = 1000 ft/min

From a brief consideration of Assumption 3, it will be seen that the stroke of the engine has in fact been taken into account. 1000 ft/min was the then considered maximum mean piston speed that was consistent with acceptable wear and friction. Thus the formula "expected" a short stroke engine to operate at a higher r.p.m than a long stroke engine and vice-versa, the product of stroke length and r.p.m. being constant - in other words, the mean piston speed Vm. This was their worst assumption.

OK people, now it is over to you to argue against the Jowett 7 hp twin with an RAC rating of 7 hp producing a magnificent 17 bhp.

[richard turner]

The Jowett 7 seems to have a considerable ability to pull! Whilst on the way to a rally with my old van the BMW 5 series we were towing a caravan with broke down. The AA declined to help as the BM was deemed to be in a dangerous place and it was suggested that we had to summon traffic officers to assist. In a fit of pique I towed the BMW with caravan attached to a safe place which was fortunately within a mile. The process was not fast but the old crate completed the task without too much trouble!
Rich

[PAUL BEAUMONT]

I suspect that the answer to this conundrum lies in the fact that what the Jowett Flat twin lacks in power it makes up for in torque - hence the "Little Engine with the big Pull". When towing, unless you want to imitate the idiots off Top Gear torque is arguably more useful than power.