The Nut Behind the Wheel: Spring 1999

In a recent issue of British Car, there’s an excellent article written by Australian Pat Quinn regarding the restoration of his Austin-Healey BN3. What’s a BN3, you ask? Well, Pat has restored the first of the two prototype four cylinder test vehicles into which Donald Healey and crew stuffed the soon to be introduced six cylinder unit. The vehicle looks just like a four-banger, except for a couple of differences, like a louvered bonnet, four seats, and solid wheels. But the most visual difference is that Pat’s car is fitted with a later roadster-style windscreen, thus previewing things to come with the deletion of the four-banger’s lovely folding unit. It is this windscreen that caught my eye and tickled my fancy, as Pat mentioned while assembling the car after its restoration, “The windscreen was difficult. I managed to break two in the process.” Been there. Done that.

It seems that one of the common restoration threads among us Healey people is the problem of broken windscreens that occurs during a restoration. How many Healey owners have assembled their car’s windscreen, or even had it professionally re-glazed, only to come back the next morning after installation to find it cracked? More than just a couple, I’m sure. What looks like a simple, straightforward process that any talented do-it-yourselfer can do is really a challenge due to a several factors. Let’s look at what it’s going to take to do this job on any of the Big Healey windscreens with some possibility of success the first time!

The first factor at play here is chrome plating. Almost all of us will have the windscreen frame re-plated. When this happens, it’s not unusual to get the pieces back in a different shape than when they went to the plater. Since all the Healey windscreen frames are brass, they can be shaped easily and, just as easily, bent, both before and after plating—good news, bad news. Sometimes in polishing, the pieces get caught up on the polishing wheel and bent, or the polisher believes they should be shaped slightly differently, or they just change shape somewhat due to the nature of the process and the softness of the material. It’s important to at least start with the pieces fitting correctly before you ship them off for plating, as it’s important to minimize how much you have to shape them after they’ve been plated. When bending after plating, you risk popping off chrome or wrinkling it if you have to bend the frame too much, in which case, it’s back to the plater again. All the pieces of the windscreen frame must fit the contour of the glass exactly and must all fit together with each other. If they don’t, and you begin to force them together, usually a cracked windscreen results.

Another problem with plating is that the channels may become some what narrower due to the buildup of plating material. This is not a good thing! You may not be able to get the lower T-shaped shroud seal in place and make it stay or, in even worse cases, there will not be enough room for the glazing rubber and glass to fit easily into the channel. Fixes? Enlarge the channel if this happens to you. A wedge-shaped piece of wood that will open up the channel slightly is the best tool to use. Wood won’t mar the chrome, whereas a screwdriver will just leave marks that not even the chrome plater can get out. The objective is to allow the various parts to just go together without forcing anything. If you have to force it, like using a hammer or excessive pressure, then the channels are just too tight. Tight channels lead to cracked windscreens!

The next factor is the hardware that is used to fasten together the windscreen frame. The screws that you use to attach the frame to their steel corner pieces must be the right stuff. If you use substitute screws that are longer than original, you risk having the end of one of them contacting the glass, an open invitation to crack propagation! The corner brackets must exactly match the holes in your frames so that the pieces will come together at each corner correctly. By drawing together each frame piece at the corners, additional strength is added to the assembly, with the load distributed to both the frame and the corner brackets.

A loose frame can also lead to a cracked windscreen. If a bracket’s holes don’t line up with the windscreen pieces, then select one that does, or drill and tap the bracket with a fresh hole, or fabricate a new bracket yourself. It’s important that no metal pieces contact the glass. To prevent such contact, that’s the job of the rubber buffer strips and the window glazing rubber. For the window glazing rubber, I highly recommend getting the appropriate glazing rubber kit of the right thickness for your model Healey. Before these were available, I used material from various sources, some of which were professional glass shops. But I was never really satisfied with any of these products, some of which I believe directly led to a couple of windscreens of mine that cracked.

While the shop manual and various catalogs show the stuff I’m calling rubber buffer strips, these do not come in the window glazing kits. You must use your originals or secure an appropriate replacement. These rubber buffers take up the space in the windscreen channel between the corner brackets. These strips of rubber, about a quarter of an inch thick and as wide as the chrome channel, cushion (buffer) the glass from contacting the windscreen frame. For the four cylinder windscreen, they additionally prevent the mounting screws used to attach the windscreen frame to the pillar post inside of the windscreen frame from contacting the glass. If your windscreen is original, or was last re-glazed correctly, these strips will be inside the channels when you remove the old glass. They generally are reusable.

What keeps the corner brackets and screws from contacting the glass? The windscreen glazing itself. So it’s very important that this glazing material fully extends into the corners of the glass to provide that bit of cushion needed to separate the glass from the hard stuff!

Next time we’ll continue to talk about windscreen assembly and attaching your completed windscreen assembly to the car, as well as some other important things so you won’t experience the dreaded crack of doom from windscreen replacement.