In the latest copy of the Cornwall Club's magazine, I see there's a letter from Dave Mann (RN Saloon Registrar) stating that in the past he had 'wondered' why people changed from Vacumm wipers to electric.

His long time experiance seems to have been with the updraught 22FZ type, however he thought he might improve things by fitting a side draught 26VA and manifold and one noticable effect was the vacuum wiper was a lot slower and generally in efficient, indeed he felt that he would go to an electric wiper too if that was the standard of performance.

I have 26VA's and the vacuum wiper motors have now been replaced by electric after a particularly nasty 5 hour journey recently in constant rain and mud on the road, most of the time I had to operate the wiper by hand. I was glad to get home.

SO, the purpose of this posting is, why would the 22FZ create a different result from the 26VA? Presumably it's the shape of the inlet manifold.

Naomi

Niaomi,

I havnt seen the earlier carb, but is the choke size 22mm as opposed to 26mm of the 26VA. I dont know if the above info is correct but if it was then that might be an explanation.
The depression or vacumn is related to the cross sectional area of the orofice the air is flowing through. Our dear friend Bernoulli decided that airflow speeds up if you pass it through a reduced area(venturi) and thus the pressure reduces, so in the case of a carb which is throttled back there will exist a high depression on ther engine side of the throttle.
So if the choke is bigger on the 26VA perhaps the depression is less????
Incidentally "moderns" whcih used to be "souped up" with twin sidedraught Webers have been known to have problems with brake servo vacumn and I have heard of vacumn reseviors being constructed.

Steve

Hi,

For any given speed the A7 engine needs a certain volume of air! If the hole it sucks it through is 22 mm instead of 26mm then the speed of the air through the hole must be greater. Therefore the amount of 'suck' must be greater ( in layman's terms ) and therefore the vacuum wipers should be more effective.

Whilst on the subject have you seen how thick the butterfly is in an updraught carb compared with the side-draught? Whilst the up-draught carb would seem to have everything going against it they seem to work very well.

I had a vacuum one on my car – It was horrible –
Mac soaked the leather plunger things inside and tweaked it, but when ever it was needed the most IE in the rain it stopped

I saw a really flash one a an auto jumble – like a dynamo you flick it and it goes off by itself.

Having been really unlucky with parts – I persuaded the stand holder to let me go and try it.

Trusty tool kit to hand I wired it up and flicked it into action, it was superb.
Holding it my hand having connected it to the 6volt battery, I opened the door to switch the circuit off… and WANG !!! did I get a belt from it.

Stood in the field with enough wire to test it, scared to drop it, as it would have hit the door, there I was – stuck – If I made contact with any part of the body I completed the circuit and got one heck of a thrwack…..

To do that, they must be generating some current.

I pulled the wires out in the end !!!

Not very helpful but thought I would mention it –
I might try and round up all the different types for the web site….
After the stamps, the Bruce White fourum, and some car info ……

Well back to the web site building !

Jason

The 26Va side draught didn't decrease the fuel consumption, so I reverted to the 22FZB which gives 35MPG overall and 50MPG on a run. So my vacumm wiper is still running well, it is still faster than electric even at 45 MPH. However it stops when hill climbing and does a couple of sweeps when changing down. Ideally you select the gear and throttle setting to keep the wiper going and this gves the best fuel consumption.