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MG MGA - coupe wipers

With the onset of winter I've been trying to improve the operation of my wipers. The problem with the coupe is that the windscreen is highly curved at its sides and the wiper blade has trouble following the curve. This is compounded by the low pressure the wiper arm can bring to bear on the wiper blade to make it follow the curve. My rainbow arms do not have springs but rely on the bending pressure of a flat plate. Be grateful to hear from any coupe owners who have managed to solve this problem
J H Cole

I use the adjustable arms BHA 4914S. I may have shortened them. Blades are GWB 1412.

I also use a modified 2 speed motor from a B.

Hope that helps

Colin
Colin Parkinson

Colin, I understand it is quite difficult to modify an mgb 2 speed wiper motor to work on an mga.
My mga cries out for the 2 speed wipers.
My single speed are so slow that I have to depend on using Rainex on the screen to let me drive more than about 40 mph in the rain.

Did you fix up the 2 speed youself or did you buy the motor and gearbox set up already modified?

Colyn
Colyn Firth

JH, I forgot to say that I changed my standard mga wiper arms for the screw-on mg midget type. They put much more pressure on the screen and work better but the higher friction tends to slow them down a little.

I also found that the modern version of the original mga design tend to fall off at the most awkward moments. I recently had to drive 100 miles in torrential rain in 70mph traffic with no wiper blades!
Luckily, by sheer chance that morning, I had applied Rainex to the screen and I found that so long as we drove above 40mph, the screen stayed clear.

Hence my interest in the 2 speed set up!
Colyn
Colyn Firth

Colyn, give Dominic a call re the MGB wipers..I used his info, and changed to these.
Gary Lock

Some improvement can usually be obtained by bending the arms to put more arch in them. I generally do it to everything I drive, hate it when the wipers lift off the screen at speed. I don't know how they get flattened out, but they do (I actually resorted to measuring the clearance of the arm off the screen), though it is worse on cars used in winter. Some blades can be carefully bent as well to improve the curvature following characteristics. And I finally cured my Mazda of lift-off by using shorter blades after observing that several inches were where I don't/can't look, namely at the bonnet & trees - but MGA are a little shy on excess blade length! Still, 10 or 15% off the blade is that much more effective pressure but still less drag.

FRM
FR Millmore

I notice,on my wiper blade arms that there are two small pins at each end. On the passenger side the blades do not seem to be a problem,but on the driver side,the outer edge of the blade has a good 1 1/2 inch not touching the screen. If I were to remove the outside pin would it not allow the metal blade and rubber to be bent more in order to touch the screen. It seems as thought the pin prevents the blade from flexing.
Gordon Harrison

The two speed modification I did is documented on Barney's site. It uses the two-speed motor from an MGB or similar, but you have to replace the gear wheel with one from a mini - which on reflection suggests that a late mini motor may well do the trick straight out of the box (and will be a lot easier to find in the UK at a local factor or breaker). The positioning of the peg on this wheel determines the arc that is swept by the wipers.

The wiring schematic and part number for the switch are also listed on Barney's page. I would also buy a new connector for the motorto make fabrication of your new harness much easier.

On a LHD car, I would also suggest using the B rack, and mounting the motor under the dash as it is on the B. I mounted mine in the standard A place, using the A mounting plate, B rubber pad and B metal U clip (see the B catalogue to figure out what I am rambling about.)

The two-speed is MUCH more effective than the MGA setup.
dominic clancy

The picture shows the end of the wiper blade that misses the windscreen - about 15% of its length. This is after some bending of the last piece of the wiper as FR suggests. I've placed an order for rainx and will see if it helps. My wiper blades are ancient and it may be that the rubber has lost some of its softness so as an experiment I'm thinking of trying some new blades using one of those replacement kits cut to length. I don't want to order up originals yet without knowing the remedy.

J H Cole

Gordon -
A pic of the arms & blade, preferably in the position where there is a problem, might help. Lots of different designs, and some are just not suited to severely curved glass. Sometimes what you are describing comes from bent arms, since the angle of the arm end may limit the pivot action. Re-arching the arm as I suggested above frequently addresses this.

FRM
FR Millmore

J.H.
Your photo shows exactly what my wiper blades do on my roadster, so this may not be a function of the blade but the arm. I tried new blades and the problem persists. The early A arms have a flat blade that provides the pressure on the screen. I tried bending the arms but this did not improve the length of contact much. Later ones from the B have a real spring, and that probably makes them press harder on the screen.
Peter.
P. Tilbury

Colyn, my set up was Dominic's idea!! I think the gear wheel was 105 deg? Not sure if he recomended the arms and blades, or if I did that by process of elimination.

Colin
Colin Parkinson

I do not think that the wiper arms in the photo are the original type. The original ones (often discarded but I have an original pair on my coupe) seem more likely to follow the curved windscreen corners.
Barry Bahnisch

You might try this site to see if they have anything that would work. You can custom build what ever you need on their web site. http://www.texautomotive.com/classic.html
Ed Bell

Barry, do your wiper arms have a spring and is the arm extendable? I think my arms may be similar to early midget. It strikes me that only a sprung arm can begin to put enough pressure on the blade to follow the windscreen curve.
J H Cole

Enclosed is a pic taken of a blade for sale on Ebay.As we can see it is very flat.

Now see my next post

Gordon Harrison

Here is a second pic of another blade on Ebay. Quite a difference in curvature. Perhaps the [problem lies in the actual blade type and not the wiper system.

Gordon Harrison

Seems to me it should be obvious that the blade used must be physically capable of curving enough to follow the glass, and the pic from JHC seems to show one that cannot do so. Bending only the outermost segment doesn't help much, since all the pressure gets applied to the inner sections, which are pretty well flat as shown. I no longer recall what the OE parts were like, but given the shape of the coupe glass, any arm/blade combo that is longer than standard might have this trouble on the outside end of the screen, but roadsters should not be a problem.

The multiple cantilever weight distribution systems of trailers for very heavy stuff have always fascinated me, and these segmented cantilever beams in the wiper blades are the same sort of thing. You need to really think about how the force is distributed whilst allowing for different road or glass contours. One sure thing is that when any segment reaches its travel limit, the even force distribution goes away quickly.

All arms are "sprung", but on some the spring is a leaf spring of one leaf, sometimes an extension of the main part of the arm. This gets deflected by the pin where the end sits, which usually has a flat on it that gives a cam action. If the pin is worn such that the cam effect is lessened or gone, or if there is corrosion of these parts, the arm will not "spring" correctly. I lubricate this contact point.

One effect of putting some arch in the arm is that you put the area of action off from where the cam/flat on the has worn, but very old arms might be past this trick.

FRM
FR Millmore

The backing of my coupe wiper blades are about 11mm wide and are chrome plated. There are cantilevered pivots at each end. On the left hand side there are five patent numbers and underneath them the words "others pending" and on the right hand side "Rainbow" and underneath that "Made in England". There are no springs.
Barry Bahnisch

Sorry, I meant to add that the arms are not extendable.
Barry Bahnisch

This thread was discussed between 21/11/2010 and 23/11/2010

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