Need some help from the G.J. brain trust

[Jim Stabe]

I started putting the windshield back on my widened MGB project today and ran into some problems. I have never had the entire frame together on the car with the glass in it. I was always using the masonite mockup pattern as a substitute for the glass since I hadn't cut the actual windshield at that time, the glass is a cut down '67 Impala windshield. Turns out that the glass fits perfectly in the upper hoop of the frame and the bottom rail fits on to the glass when it is out of the car. Problem comes when trying to install the whole thing in the car and it puts the lower corners of the glass under a lot of stress (I cracked the passenger side of the glass today - already cracked the drivers side a while back).

Since I have to make another windshield anyway, I was thinking of extending the glass down until it comes within 1/4" of the cowl (about 1 1/4" more glass) and them making some sort of rubber piece to keep the glass pushed up and make the lower edge look nice. Problem is I have no idea how to do that and I was hoping the G.J. brain trust could come up with a solution. I hate coming this far and running into a problem like this

 

[EdT]

Well, I'm not a glass expert, but I'll offer an opinion and you can value it as much as you paid for it. The failure of the existing windshield looks like a case of more glass than can fit in the space between the uprights at the lower ends of the frame. as you discovered, glass is not as forgiving as masonite. While you could certainly extend the glass nearer the cowl, I don't think that's going to resolve the underlying problem of too much glass between the uprights. I think that the glass needs to be a bit smaller than the frame all around and then the space between the glass and the frame is taken up by the rubber seal piece. In your situation, it looks like you need to remove glass from the lower corners of the windshield or move the bottoms of the uprights outboard so that the glass is not in hard compression anywhere. Depending on how many Impala windshields you want to use up experimenting, it might be worth finding an old timer at a local glass shop and seeing what he thinks. Nobody who was'nt installing glass 40 years ago will have a clue since all the modern cars have glued on glass which sidesteps a lot of the issues you are running into. Just some thoughts. Enjoyed following your ambitious project.

 

[Brian_B_]

I hope this is allowed here..Hotrodders website would be more able to help with your situation.

http://www.hotrodders.com/forum/

 

[kerrynzl]

http://www.garagejournal.com/forum/attachment.php?attachmentid=347058&d=1402436930

Looking at this bottom section in the photo, the extrusion wraps around the glass in a "U" shape.

I would cut the extrusion from behind into an "L" shape, then use wind shield urethane to glue the glass to the lower frame.
you can slip it in underneath, and also grind the frame if needed.

Do away with the rubber altogether .

 

[softailgarage]

I cant answer your question but... An LT1 w/ six speed in a MGB??? Hoooooly ****, I gotta see it, that sucka gonna haul some ***!!! A couple of years ago there was a dude up in Fallbrook dumping 454's in Miata's, called 'em Monster Miata's.

 

[pmason0]

You could maybe use Lexan that is what people use in race cars to lose some weight. I haven't switched in my race car, waiting for the window to break first.

 

[Jim Stabe]

I cant answer your question but... An LT1 w/ six speed in a MGB??? Hoooooly ****, I gotta see it, that sucka gonna haul some ***!!! A couple of years ago there was a dude up in Fallbrook dumping 454's in Miata's, called 'em Monster Miata's.

With the supercharger it should be 425 - 450 hp at the rear wheels - getting it tuned next week.

The Monster Miatas are actually 302 Fords but they still perform really well http://monstermiata.webs.com/faq.htm

You could maybe use Lexan that is what people use in race cars to lose some weight. I haven't switched in my race car, waiting for the window to break first.

There is a considerable wrap in an MGB windshield and Lexan isn't the easiest material to form. You also have the issue of scratching besides it's not legal.

 

[gorilla]

My 1964 MGB windshield has a rubber gasket on the bottom edge. Have you considered using two of these on your wide MGB?

 

[Kevin54]

Jim......did the windshield crack on the outside or inside, or can you tell? Also, with the windshield pillars, is there a possibility that you can open the slot up wider to accept the seal, but then also add some liquid urethane in when you set the windshield? The curvature of your pillar is not matching the curvature of the windshield exactly, so you will need some more room to allow for error.

I remember years and years ago, my dad and I were setting a rear glass in a '55 Chevy. For some reason the body of that car was tweaked enough that we went through about 5 windows before we got things to fit. But at least back then, you could get a glass for about $10 at the junkyard.

If you don't mind me asking, how did you come by the pillars. Were they custom made, which I assume they were, and when they were made, how did they arrive at the dimensions to cut them since the windshield is a compound curve?

And if they were cut by someone on a CNC, they should still have the program stored, and shouldn't be too much of a problem for the part to be set back up and widened out a little to correct it. If I had a CNC, I could help you out but sadly I don't. I can though, tell you how they can double check things and get the correct dimensions to recut your slot through the pillars.

 

[Kevin54]

I did go back and reread what you posted above and took a better look at the pics. When you are tightening down the pillars is when it cracked, so you are putting the bottom of the pillars on a bind.

Also looking at where the pillar sets on the body, you look to have an area that does not meet the body correctly. It looks like you need some sort of an adapter to fit the bottom of the pillar or the top of the cowl.

I'm thinking and typing at the same time.

If the windshield fits in the frame the way it is while it is loose, yet mounted in rubber....do you have someone that is helping you to hold and mount the windshield frame? If so, what you can do is get a tube of Prussian Blue. This is basically an oil paint that does not dry. You can "blue up each mounting point on the cowling, and set the frame down on it and look and see where the bluing hits on the frame. You can then take a die grinder and start to sculpt the bottom of the frame. Test fit again. grind out and sculpt where you see the bluing. Lather, rinse, and repeat. It will take a while to do, but sculpting the bottom of the frame will be your best bet so you don't throw things on a bind. Then before mounting it for the last time, cut a rubber gasket for underneath the pillars of the frame. Something like a 1/16" or 3/32" thick urethane rubber that is not too high of a durometer would work. A piece of urethane with Shore A durometer of somewhere around 60 should work and allow for just a tad bit more of flexibility instead of nailing things down so tight.

One thing to remember also, that with the size of engine you have, and the small body, you will get twist in the body, so you want a little bit of flexibility. Your's is not like a factory built car where the windshield pillars are carried down into the door jams and are integral to one another, and then the windshield is set in that. Yours is a three sided frame that you are tying into something that will flex. Now if the bottom piece tied into the two sides and was rigid, then that would change the whole ballgame, but sadly I don't think you have that option. Even if your frame was a one piece frame, I think you would still get a twisting action out of it, so you will have t work with what you have and let the rubber around the glass handle the flex. And a windshield will take quite a bit of pressure on it as long as the rubber absorbs the twist before it reaches the glass.

 

[-Brent-]

Where the glass cracked doesn't actually have to be the place that's causing the stress but I am going to assume that's where the force is being applied due to mounting.

The pillars looks sand cast. I'd mount the frame without the glass and pull some measurements and transfer that over to the broken glass. As well, I'd get it fitting/mounted with the broken glass too. That way you can trim, sand, shape this glass without worry before you mess with the next "victim" ...er... windshield.

I don't envy you with this project. Just take your time and make small adjustments.

 

[Kevin54]

Jim....One other thing, check with E.rodz as he has a close friend that has done the same thing to whatever small car he has. He did exactly the same thing as you did as far as splitting a car and widening it out, so he may have a good idea as to what was done to remedy the situation. I would venture to guess that he would give you his buddy's e-mail so you two could talk back and forth about it.

And one more thing to consider, and it looks like your frame is aluminum, have you give it a thought about doing something like a Duvall windshield? Run a pillar down the middle and put the windshield in, in two pieces? That way, you are not creating so much stress across the whole windshield.

I did send Eric a PM and asked him to stop by in this thread to see if he has some input about what his buddy did. There is a video clip of the car, but I'm not sure where the clip was at.


`

 

[Jim Stabe]

My 1964 MGB windshield has a rubber gasket on the bottom edge. Have you considered using two of these on your wide MGB?

I'm not using the stock lower rail so the stock rubber piece would have no mechanism to mount

Jim......did the windshield crack on the outside or inside, or can you tell? Also, with the windshield pillars, is there a possibility that you can open the slot up wider to accept the seal, but then also add some liquid urethane in when you set the windshield? The curvature of your pillar is not matching the curvature of the windshield exactly, so you will need some more room to allow for error.

I remember years and years ago, my dad and I were setting a rear glass in a '55 Chevy. For some reason the body of that car was tweaked enough that we went through about 5 windows before we got things to fit. But at least back then, you could get a glass for about $10 at the junkyard.

If you don't mind me asking, how did you come by the pillars. Were they custom made, which I assume they were, and when they were made, how did they arrive at the dimensions to cut them since the windshield is a compound curve?

And if they were cut by someone on a CNC, they should still have the program stored, and shouldn't be too much of a problem for the part to be set back up and widened out a little to correct it. If I had a CNC, I could help you out but sadly I don't. I can though, tell you how they can double check things and get the correct dimensions to recut your slot through the pillars.

There are two separate crack scenarios and although both are in the same location, both have different causes. The driver side was caused by the channel in the pillar not following the contour of the glass at the very bottom. The crack didn't appear for several months just sitting in place on the car - no bottom rail in place. I found the offending area and relieved the side of the groove so it did not apply pressure to the glass - that problem solved. The glass fits perfectly in the upper frame (the hoop and pillars) and I currently have the glass held into the upper frame with zip ties. It is very secure and I could drive the car that way except for the ugly zip ties and the stuff that blows in under the glass at the bottom.

The 2nd crack is on the passenger side and it was caused by the lower rail. The lower rail is very complex in that the groove the glass sets in has a lot of curve in two different planes, it has to hold the glass at a varying angle to the cowl between 36 and 39 degrees, plus it has to sit flat on the curvature of the cowl. Making it was an absolute nightmare and I am admitting defeat that I can ever get all the relationships of the angles and curves right. Neither of the cracks was caused by the tightening down of the pillars in the car.

The pillars are made from MG Midget windshield frames. You can see the entire process in part 2 of my build journal http://forum.britishv8.org/read.php?13,22422 There are links in my signature. Basically I made bases from aluminum plate that allow using the stock MGB mounting system in the body. The Midget pillars are longer than MGB but very similar in design. The Midget windshield is also flatter (less wrap around) than the MGB which worked out perfectly as it matched the curvature of the '67 Impala windshield at the ends. With the longer length the windshield is actually the same height as the stock MGB but the glass is raked back 8 degrees more.

I did go back and reread what you posted above and took a better look at the pics. When you are tightening down the pillars is when it cracked, so you are putting the bottom of the pillars on a bind.

Also looking at where the pillar sets on the body, you look to have an area that does not meet the body correctly. It looks like you need some sort of an adapter to fit the bottom of the pillar or the top of the cowl.

I'm thinking and typing at the same time.

If the windshield fits in the frame the way it is while it is loose, yet mounted in rubber....do you have someone that is helping you to hold and mount the windshield frame? If so, what you can do is get a tube of Prussian Blue. This is basically an oil paint that does not dry. You can "blue up each mounting point on the cowling, and set the frame down on it and look and see where the bluing hits on the frame. You can then take a die grinder and start to sculpt the bottom of the frame. Test fit again. grind out and sculpt where you see the bluing. Lather, rinse, and repeat. It will take a while to do, but sculpting the bottom of the frame will be your best bet so you don't throw things on a bind. Then before mounting it for the last time, cut a rubber gasket for underneath the pillars of the frame. Something like a 1/16" or 3/32" thick urethane rubber that is not too high of a durometer would work. A piece of urethane with Shore A durometer of somewhere around 60 should work and allow for just a tad bit more of flexibility instead of nailing things down so tight.

One thing to remember also, that with the size of engine you have, and the small body, you will get twist in the body, so you want a little bit of flexibility. Your's is not like a factory built car where the windshield pillars are carried down into the door jams and are integral to one another, and then the windshield is set in that. Yours is a three sided frame that you are tying into something that will flex. Now if the bottom piece tied into the two sides and was rigid, then that would change the whole ballgame, but sadly I don't think you have that option. Even if your frame was a one piece frame, I think you would still get a twisting action out of it, so you will have t work with what you have and let the rubber around the glass handle the flex. And a windshield will take quite a bit of pressure on it as long as the rubber absorbs the twist before it reaches the glass.

I made the pillar bottoms with clearance to put a 1/8" thick soft durometer gasket underneath. I will probably leave it oversize and trim it to fit after the windshield is installed for the last time.

Actually the frame is tied into the door jambs and is very solid. The car is also very rigid due to the massive, double walled tunnel in the car. The structure is like a cross between the monocoque of the MGB and a backbone structure like what Colin Chapman used in the Lotus Elan. The structure is very rigid. I was putting the car on jackstands a few weeks ago and had the rear of the body supported on stands right in front of the rear wheels. When I lowered the front down the drivers side jacksstand touched the body 1/8" before the passenger side and when I released the pressure on the jack the clearance on the passenger side jackstand didn't change - I had to shim underneath so it would support.

Where the glass cracked doesn't actually have to be the place that's causing the stress but I am going to assume that's where the force is being applied due to mounting.

The pillars looks sand cast. I'd mount the frame without the glass and pull some measurements and transfer that over to the broken glass. As well, I'd get it fitting/mounted with the broken glass too. That way you can trim, sand, shape this glass without worry before you mess with the next "victim" ...er... windshield.

I don't envy you with this project. Just take your time and make small adjustments.

Like I said above, the upper part of the frame isn't the problem

Jim....One other thing, check with E.rodz as he has a close friend that has done the same thing to whatever small car he has. He did exactly the same thing as you did as far as splitting a car and widening it out, so he may have a good idea as to what was done to remedy the situation. I would venture to guess that he would give you his buddy's e-mail so you two could talk back and forth about it.

And one more thing to consider, and it looks like your frame is aluminum, have you give it a thought about doing something like a Duvall windshield? Run a pillar down the middle and put the windshield in, in two pieces? That way, you are not creating so much stress across the whole windshield.

I did send Eric a PM and asked him to stop by in this thread to see if he has some input about what his buddy did. There is a video clip of the car, but I'm not sure where the clip was at.
`

Thanks for contacting Eric, I'd like to see what he has to say. One thing I want in the car is to retain as much of the MGB look as I can, hence the Midget pillars. The Duval looks great on '32 roadsters, on an MGB - not so much.

I think all I have to do is come up with a good looking way to support the glass from the bottom and put a single bracket in the middle using some of the U channel to stabilize the glass fore and aft. I could easily machine that from aluminum. I have thought about making the lower support from fiberglass or mold it in place from a pourable silicone rubber. When I cut the next glass I will extend it about 1" further down so it is closer to the cowl and any supporting solution I use will be smaller and less noticible.

 

[gorilla]

Perhaps you could open up the groove in your lower molding so that the windshield makes no contact. Then support the glass with a couple of rubber blocks in the grove to hold it in place and then fill the grove with butal caulk.

 

[Jim Stabe]

Perhaps you could open up the groove in your lower molding so that the windshield makes no contact. Then support the glass with a couple of rubber blocks in the grove to hold it in place and then fill the grove with butal caulk.

The channel is only 1/8" wall so there isn't much room to open it up.

 

[MP&C]

Jim, how is the fit when the two frame parts are assembled off the car, ie: does bolting down the lower to the cowl cause it to twist/deform?

 

[Jim Stabe]

Jim, how is the fit when the two frame parts are assembled off the car, ie: does bolting down the lower to the cowl cause it to twist/deform?

The bottom rail fits to the glass OK off the car - not great but OK. The rail by itself fits to the cowl OK - not great but OK. The problem comes when trying to mate the assembly to the cowl. All the bad tolerances add up and the angles being off from one another rear their ugly heads and crack the glass. I have the top hoop fitting perfectly so I think the answer is to extend the glass closer to the cowl and make the bottom mount out of something compliant. I have watched a couple videos about a pourable silicone rubber that look promising and I could also make a fiberglass part that would capture the rubber U channel. All I need is something that will hold the glass up into the upper structure and it will be secure.

 

[nickleone]

Have you thought of the way a custom chop on a curved windshield is done. They sink the windshield into a slot cut into the cowl then use silicone etc to seal it.

Nick

 

[Jim Stabe]

Have you thought of the way a custom chop on a curved windshield is done. They sink the windshield into a slot cut into the cowl then use silicone etc to seal it.

Nick

I thought about it but I would still have the same problem in that I would have to make something to catch the bottom and hold it up. Same issue I have now only down inside the body.

 

[gorilla]

My last thought on this is to take the windshield to a machine shop that has a CMM have them generate a drawing for the bottom of the windshield then have a trim piece machined on a CNC mill. You would probably need to have the MG's cowl measured too.

 

[Roady94]

- If you are 100% committed to the gasket solution, you can check in with commercial glazier suppliers. They have access to gasketing options unknown to most common men. Gaskets designed to accommodate flex in framing, in addition to locating, securing, and sealing the pane.

Another option may be to extend the glass as you plan. Trim the lower channel as needed. Then use that channel as a model to cast your own gasket from silicone.

Congratulations on getting this far. I've been a silent fan for years.

 

[Jim Stabe]

My last thought on this is to take the windshield to a machine shop that has a CMM have them generate a drawing for the bottom of the windshield then have a trim piece machined on a CNC mill. You would probably need to have the MG's cowl measured too.

You must have a lot more money than I do.

 

[nickleone]

I thought about it but I would still have the same problem in that I would have to make something to catch the bottom and hold it up. Same issue I have now only down inside the body.

You make a trough for the glass to sit in. It is water tight. Not just a slot cut in the cowl.

Nick

 

[Jim Stabe]

You make a trough for the glass to sit in. It is water tight. Not just a slot cut in the cowl.

Nick

That creates the same problem I have now above the cowl. I have to get the curves and angles correct or it will stress the glass and crack it.

 

[Kevin54]

Jim.....I take it that you haven't had a chance to speak with E.Rodz yet.

As far as the bottom portion of the glass, what about a fiberglass lay up. At work, when we made mold, or more specifically, when a coworker made the molds, he used wax to get the shape he wanted of every detail. The wax comes in sheets of various thicknesses. You use the wax to get your form, then you layup your fiberglass and epoxy over the wax. This give you the mold you need you can then dismantle everything, then use that mold to make your actual bottom channel. You would want to make sure that you had the bottom seal on first before starting the layup.

If you are interested, I can e-mail my old coworker and see where he gets his supplies from.

And even with a fiberglass bottom piece, you could always get it chromed.

 

[Kevin54]

My last thought on this is to take the windshield to a machine shop that has a CMM have them generate a drawing for the bottom of the windshield then have a trim piece machined on a CNC mill. You would probably need to have the MG's cowl measured too.

You must have a lot more money than I do.

Jim...in reading back through, Gorilla does have an idea. A lot of times, companies will do a home hobbiest a favor cheaper than they will do another company a favor. Sending out a few e-mails to a few places only takes time and not money. That is unless you are doing this on someone elses time I did a search for CMM places in the San Diego area. CMM stands for Chord Measuring Machine. They could probably knock out dimensions on a windshield for you in less than 30 minutes. If you wanted them to do the frame, probably another 30. All the CMM does......you have a probe, they pick a Zero point, then they can go around the profile and generate points every so often. They could then compare it to the existing frame that you have now.

You'd be surprised as to the ones that would be interested in it just because it is something different. For one, a lot of them are not car guys that runs a CMM. And secondly, a lot of times they will take on something like that and store it in their head because another job may come up down the road that is similar but different, where they can be the hero. If it were me, I'd send out a few e-mails. Check this link and think about it. http://www.thomasnet.com/southern-california/inspection-services-cmm-40372203-1.html

 

[E.rodz]

wow quite the project you have going on here! the picts are to small to really see what is going on here. have you considered using a black urethane to glue it in instead of using the u channel gasket.? I do know one thing with this type of install if the entire perimeter is not completely flat against the mating surface it will crack. if you get it in there with out breaking and there is any stress on the glass when driving the car and pushing it on hard turns and or bumps it will crack! looks like the frame is cast alum. witch can be modified to fit better might be your best bet. good luck with your cool project!

 

[Jim Stabe]

wow quite the project you have going on here! the picts are to small to really see what is going on here. have you considered using a black urethane to glue it in instead of using the u channel gasket.? I do know one thing with this type of install if the entire perimeter is not completely flat against the mating surface it will crack. if you get it in there with out breaking and there is any stress on the glass when driving the car and pushing it on hard turns and or bumps it will crack! looks like the frame is cast alum. witch can be modified to fit better might be your best bet. good luck with your cool project!

If you click on the pictures they get a lot bigger. I'm going to use the U channel in the upper portion because it fits very well. The vertical pillars are cast from an MG MIdget but the rail across the top is aluminum U extrusion. If I put a ompliant lower support against the cowl to hold the glass up into the upper frame I think I will be OK. I went to the L.A. Roadster Club show yesterday and got a couple ideas I will experiment with over the next couple weeks before I decide which way to go.

 

[volleyball]

I am thinking the chevy windshield is all wrong for this project. You want something British looking to retain the stock look. Why not go with a 60's British windshield? From a larger vehicle. They seem to all have the same shape. Maybe a jag salon. Or a lorry?
Anyways take the windshield and frame. Stiffen it up, clad it to look MGB. Make mounts so that you can bolt it in like the stock windshield was.

 

[Jim Stabe]

I am thinking the chevy windshield is all wrong for this project. You want something British looking to retain the stock look. Why not go with a 60's British windshield? From a larger vehicle. They seem to all have the same shape. Maybe a jag salon. Or a lorry?
Anyways take the windshield and frame. Stiffen it up, clad it to look MGB. Make mounts so that you can bolt it in like the stock windshield was.

Go read the links in my signature. There is no British car that is as wide as mine and very few American cars for that matter. There are even fewer that have as much curvature as the MGB has, The Impala is the one that comes closest to meeting the criteria - trust me, I've looked at a lot of windshields. My frame IS stiff and it mounts like the stock one does and it looks better than the stock one IMHO.

 

[volleyball]

This is somewhat what I was thinking

 

[Jim Stabe]

I bet you couldn't get a 63" wide windshield out of that. Even if you could, it's a moot point since I have already done the fabrication using an Impala windshield