Curti Posted January 22, 2014 Share Posted January 22, 2014 I have a windshield frame for an Auburn speedster that was manufactured in correctly. The glass on the passenger side slides right in. But there is no way the left side will go in unless the outboard windshield post is bent forward 3/4 inch. The post is approximately 1" X 1" . I am going to build a fixture to hold the frame to my welding table. Are there any words of wisdom before I go forward? Link to comment Share on other sites More sharing options...
ojh Posted January 22, 2014 Share Posted January 22, 2014 I can tell if the post is out of true in the sides or out of true at the bottom. It's a 1 piece casting? Is the left post and right post equal to each other when looking across? Link to comment Share on other sites More sharing options...
Curti Posted January 22, 2014 Author Share Posted January 22, 2014 The casting is three pieces. the center and the two outer left and right castings. The LH post seems to be tilted backward. The base of the casting lays nicely on the cowl. Link to comment Share on other sites More sharing options...
Restorer32 Posted January 22, 2014 Share Posted January 22, 2014 We have silicon bronze castings made on a regular basis and occasionally have to bend one a bit. Success or failure depends somewhat on the alloy and how good the casting is. We do it cold and very carefully. 1 inch over the length of a windshield post should be doable. Worst case you break it then repair by silver soldering before plating. Good luck! Link to comment Share on other sites More sharing options...
Curti Posted January 22, 2014 Author Share Posted January 22, 2014 That is encouraging, I think the casting was done in the 70's. Other than an expensive analysis is there a way to determine if silicone is in the alloy? Link to comment Share on other sites More sharing options...
Restorer32 Posted January 23, 2014 Share Posted January 23, 2014 I don't know. The more "red" the casting the more brass is in it and the more likely it is to break. Bronze is more yellow and significantly stronger. Link to comment Share on other sites More sharing options...
Curti Posted January 23, 2014 Author Share Posted January 23, 2014 This is very yellow, so I suspect is is silicon bronze. May I ask, why you bend it cold? Link to comment Share on other sites More sharing options...
Bhigdog Posted January 23, 2014 Share Posted January 23, 2014 With all respect it's pretty much impossible to identify brass vs bronze or which alloy of either you have by color. Likewise it's impossible to predict the malleability of your casting other than to say casting, if not annealed, often have a crystalline structure which is prone to cracking. Check out the link below. Good luck.................Bobhttp://www.metalreference.com/Forms_Copper_Alloy.html Link to comment Share on other sites More sharing options...
Curti Posted January 23, 2014 Author Share Posted January 23, 2014 I have annealed rigid brass and copper tubing to make tight bends etc. Can a casting be annealed? Link to comment Share on other sites More sharing options...
Bhigdog Posted January 23, 2014 Share Posted January 23, 2014 I have annealed rigid brass and copper tubing to make tight bends etc. Can a casting be annealed?Yes. Same process....................Bob Link to comment Share on other sites More sharing options...
Restorer32 Posted January 23, 2014 Share Posted January 23, 2014 Not pretending to be a metalurgist. In our experience the yellower the casting the more likely it is to bend without breaking. We bend cold because again in our experience we have broken more castings when trying to use heat. Just a general guideline, nothing more. We have far fewer problems since we started having all our castings done in silicon bronze. You are right though, bending any cast alloy is a crap shoot. Link to comment Share on other sites More sharing options...
Bhigdog Posted January 23, 2014 Share Posted January 23, 2014 Yes. Same process....................BobLet me walk this back a bit and say copper alloys generally can be annealed. There may be some alloys that that do not react well to the process. You might want to do more research vis-a-vis annealing bronze and brass before you make that commitment...............Bob Link to comment Share on other sites More sharing options...
Rusty_OToole Posted January 23, 2014 Share Posted January 23, 2014 Without seeing the casting and the car it is not possible to say if this will work, but have you considered filing or grinding a little off the base to make it lean forward more? You wouldn't have to shave much off to make the top move 3/4".Another way to get at the same thing would be to shim it and put a rubber gasket between the base and cowl. Link to comment Share on other sites More sharing options...
jdome Posted January 24, 2014 Share Posted January 24, 2014 Hello Curti, Bend brass cold (room temp.) Brass becomes brittle when hot and will likely crack or break if you bend it hot. Anneal it first, in fact you can control where the bend occurs if you just anneal the area where you want to bend such as at the base of the stanchion, not the whole frame. Anneal it by heating the area until it becomes red hot, then dunk it in cold water or under tap water. A plumber's hand held propane bottle torch will do the job. make sure you heat all around the area. Link to comment Share on other sites More sharing options...
Ivan Saxton Posted January 24, 2014 Share Posted January 24, 2014 A good, older, experienced scap metal dealer or foundryman may be able to estimate the alloy composition fairly accurately. The critical factor that affects malleability is the percentage of zinc in the alloy. Brass is usually not first choice for casting, unless the yellow colour is needed; that is, it will not be plated. If the alloy is gunmetal with tin as the main addition to the copper, it will be much more friendly to work. It is the zinc in brass that makes it "Hot-short", which means that it is more likely to break if you try to deform it when hot. One of my friends whose qualification is as a goldsmith, tells us that when shaping brass sheets by spinning, the temperature of brass is likely to be sufficient at the point when it ceases to be plastic. An experienced spinner would quickly release the pressure pad and flick the workpiece into a bucket of water and vinegar. The acetic acid is sufficient to clean the brass which would otherwise be blackened by oxidation from the heating. Now the temperature to which you heat some copper alloys for annealing can be quite critical. My son Stirling discovered that the best alloy to make some early Alfa Romeo and Isotta Fraschini radiator badges which needed to be coloured with vitreous enamel colours is what is called "gilding metal", which is 90% copper and 10 % zinc. The only place I could buy this had to roll it to half the thickness of the stock that they kept. The rolling cost considerably more than the material , but hardened it so that it needed annealing before the blanks could be gently pressed to the required radius, and then machined with the bench-top computer controlled milling machine I had made for him. The definite instruction was that the blanks had to be brought to exactly 400 degrees C and immediately allowed to air cool. We did this on the electric element, ceramic cooking top in the kitchen, which my pyrometer determined was the maximum temperature of the stove top. The method was to hold each blank with the pyrometer surface temp sensor, and flick it off the heat circle as soon as it reached 400C. I was told that if the metal was allowed to stew on the hot plate the crystal structure would be impaired. Now it may be of interest that this metal merchant usually only had one customer for gilding metal. That is the Commonwealth Mint. When Parliament decided to debase the Australian currency, they changed to gilding metal for the new one and two dollar coins, because the colour is similar to gold until it oxidises a little. Now to finish with a little piece of incidental information, Section 115 of the Constitution of the Commonwealth of Australia requires : "States not to coin money": " A State shall not coin money, nor make anything but gold and silver coin a legal tender in payment of debts ". This could be a problem, perhaps. Just to re- emphasise: A lot of copper cast alloys may be friendly and plastic, but you need to approximately know whether you have copper and tin, or copper and zinc, and if zinc, how much. Often you may be able to correct what you have with gentle bending and maybe gentle heat without approaching red hot. I once saw Jim Formby make a windscreen frame from yellow brass tube for his brother Henry's 1912 Cadillac. He used gentle heat, gentle persuasion, and patience. Link to comment Share on other sites More sharing options...
Friartuck Posted January 24, 2014 Share Posted January 24, 2014 There are metal working Forums on Yahoo and Google if you're looking for more opinions. These guys do their own castings and machine work. One example is: https://groups.google.com/forum/?hl=en#!forum/rec.crafts.metalworking Link to comment Share on other sites More sharing options...
Curti Posted January 24, 2014 Author Share Posted January 24, 2014 Yes, I have already ground the front of the casting but can't do much more of that without distorting the general appearance. I have dug out a bit of the factory lead in the cowl as well. Hopefully a little bit here and a little bit there will get me where I want to go. I will anneal it in the area and bend it cold. I'll take some pix over the weekend and let you know how it worked out. I very much appreciate all of the input. Link to comment Share on other sites More sharing options...
Curti Posted January 26, 2014 Author Share Posted January 26, 2014 Built a fixture to secure the windshield frame. Annealed it and bent it forward approximately 1/4 inch. installed on the cowl. Now get it rechromed. Thank's to all who posted. Life is Good ! Link to comment Share on other sites More sharing options...
Bhigdog Posted January 26, 2014 Share Posted January 26, 2014 Very nice. .................Bob Link to comment Share on other sites More sharing options...
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