Cylinder head for sale

[James Baxter]

Cylinder head
What is it from? 1933? My cars are fixed head so this is surplus.
Looks OK. Offers?

[ian Howell]

Post 1930 7hp or 8hp. But which?

How to tell the difference - other than by direct comparison?

I have a feeling that the water passages are different shapes.

Are you there Tony / George?!

[Tony Fearn]

Post 1930 7hp or 8hp. But which?

I'll have a go, but am willing to be corrected!

The head in James' post looks like an early 30's 7hp type. I suppose that the 8hp head is the same.

These are some similar heads in my spares.

Tony.
P.S. They would look much better cleaned-up, but they are all waxoyled, and have been for decades!

[James Baxter]

I'll forgive yours for being dirty, if you'll forgive me.
You seem to have an odd 7. Mind is now wandering to a radial 7 engine..........no , stop that!

Are these things common as muck? Is the best use of mine as a door wedge?

[Andrew Henshall]

Hi James,

Your lone cylinder head is identical to the one on my 1936 7 hp that I am rebuilding. I am missing one head, and the one I do have is cracked, and so I am interested in purchasing yours. I will PM you with my offer.

Kind regards,

Andrew

[ian Howell]

Andrew: -

It looks as if Tony MIGHT have the other one?

Tony: - I don't wonder pre-war Jowetts are scarce - you must have bits of most of them!

Good job someone collects them!

[Andrew Henshall]

Hi James,

I sent you a PM yesterday.

Yes Ian, indeed Tony does have a large collection of heads, but I already have one coming via Michael Koch-Osborne. Tony has however offered to assist with parts for shock absorbers if I get desperate as all are missing on my 7 hp chassis.

Cheers,

Andrew

[ian Howell]

Andrew: -

I, along with many others I am sure, will be watching your progress with great interest.

Personally I have found as much satisfaction in repairing (NOT restoring) my Long Four as I am now finding in using it in its albeit incomplete state. (No fabric cover, upholstery largely non-existent).

Currently it has 'one leg in the air' as I am trying to sort out the brakes. Taking note of Tony's earlier comments about the actuating levers being most effective at 90 degrees to their operating rods, I found that most of mine are at best about 80 degress - and that on the 'wrong' side of right!

I think Jowetts have something to answer for here - if they had made the keyway in the operating shafts at say 85 degrees then the levers could have been reversed when the drums wore down as they inevitably do.

I am working on sourcing suitably thicker linings to take up the slack, rather than fit what (until recently) I considered to be non-standard thinner shoes to take thicker linings.

I am back home now for a few days so I hope to make some progress in this area, but as always . . .

[Tony Fearn]

A:- I found that most of mine are at best about 80 degress - and that on the 'wrong' side of right!

B:- If Jowetts had made the keyway in the operating shafts at say 85 degrees then the levers could have been reversed when the drums wore down as they inevitably do.

A:- That's an interesting observation Ian.

B:- Perhaps the length of the rods and also the length of the front brake actuating rods through the king pins has a bearing on this. The length of the latter must have some bearing on the lever angles.

I have no engineering training, so it's just a thought.

Tony.

[george garside]

I would go 100% with Roy's method it not only concurs with the factory recommendation but is also reinforced by Roy's vast practical experience of Jowett repair and servicing from the early twenties right up to his departure from this earth! Roy was a practical engineer and his garage had a fully equipped machine shop. He had many little 'non factory' wrinkles. I suspect the 80deg may be working 'better' on a particular vehicle may be because it gives the best result when dealing with cumulative wear througoutt the system. This however may not be giving the same stopping power as the factory setting would have achieved.

some test results of the 7hp 4 wheel braking system are ( from 30mph)
1929 long saloon 27ft from 25mph
1930 long saloon 41 ft '' 30 ''
1932 '' '' 39 30
1934 kestrel 38 30

so arou;nd 40 ft from 30 mph should be achievable. I used to test mine after brake set up by doing a crash stop on a quiet bit of road, applying the brakes when the front wheel reached a prearranged stone at the side of the road and then measuring from there to where it stopped. I always managed to get within the contemporary road test figures.

george

[Tony Fearn]

I used to test mine after brake set up by doing a crash stop on a quiet bit of road, applying the brakes when the front wheel reached a pre-arranged stone at the side of the road and then measuring from there to where it stopped. I always managed to get within the contemporary road test figures.

Wonderful, George! I'll bet you don't worry too much about political correctness either.
Tony.

[Forumadmin]

To illuminate on Tony's lack of engineering knowledge... Mechanical advantageis what mechanical brakes use. In simple terms it is a lever and this is translated into various forces that are vectored in different directions. The maths is simple for some and a bit more difficult for others. But look at it this way.. in Tony's diagram the direction of pull is rotating the shaft at the top in a counter clockwise direction. The maximum amount of torque or rotational force is achieved when the vector (or direction of pull) is farthest from the centre of the shaft.

See what happens as you move the arm either counter clockwise or clockwise from the fully down or 90 deg position. If you move it through 90 deg the direction of pull or vector will go through the centre of the shaft so there will be NO torque on the shaft, just all your force will be trying to move the position of the centre of the shaft so all your foot pedal effort will be wasted.

The maths uses trigonometry with sines, cosines and tangents, so suggest you go and find your school books for that!

Since you need the maximum force to be when the brakes are hard on, the position of the lever at that point should be 90deg to the direction of pull. The rest position is not that important, although if it is at zero or 180 deg you will not be able to start the braking process!

[george garside]

I suppose a common sense non scientific way of looking at it is the pretend the brake rod is a human arm & hand pulling in a direction roughly at right angles to a vertical line through the brake shaft itself. Plenty of leverage would be available up to the point when the brake arm reached the imaginery vertical line but to continue this 'rate of pull' the arm would need to be moved so it pulled in a more upwards direction i.e. so that the the relation ship between the 'pulling arm' and the brake arm remained the same.

Unfortunately the brake rod is unable to change the direction of its 'pull'' so becomes less effective beyond the 90 deg mark.

or something like that!

george

[ian Howell]

Slight misuderstanding here, but at least it has provoked interesting and informed comment!

Roy was of course absolutely right when he pointed out that the best effect was when the operating rod and the lever were at 90 dedgrees to each other. As the shoes / drum wear, and the wear is taken up by the 'Mickey Mouse' nuts on the rods, the angle becomes greater and the mechanical advantage less.

Based on the diagrams above, my rods are now at about 100 degrees to the levers (not 80 as originally stated) hence the confusion!

However, when everything was new the rods were probably at 90 degrees to the levers so ANY wear would inevitably lead towards the situation I now have. My point was that if the original angle had been about 85 degrees, then early wear would have moved the angle towards 90 degrees, thereby improving the situation until at least the wear took the angle to (say) 95 degrees.

Now. Any thoughts about there being more than one thickness of lining / shoe during original manufacture?

[george garside]

[quote="Tony Fearn"][quote="George"] I used to test mine after brake set up by doing a crash stop on a quiet bit of road, applying the brakes when the front wheel reached a pre-arranged stone at the side of the road and then measuring from there to where it stopped. I always managed to get within the contemporary road test figures.[/quote]
Wonderful, George! I'll bet you don't worry too much about political correctness either.
Tony.[/quote]

Tony, I used two other bits of test terrain !

- I used a gravel covered track up to a farm to test even ness particlulary of Bendix brakes which if incorrectly set could have a mind of their own. A quick stop from as little as 15 or 20 mph would leave 4 even length ''skid marks'' ( or grooves) of equal length in the gravel.

- the other one was local test hill. This was a longish steepening type of hill on which I made a mental note of the exact position it was necessary to change down to each gear when everything was set up properly. An occasional nip up the hill would tell me if all was bang on or if a bit of fettling was required.

As to political correctness - what is that?!

george