Jump to content

Question about metal work (pot metal)


Recommended Posts

I spoke to the wiper man about having my wiper motor rebuilt. He told me that by the year of my car, that there is a good chance that it couldn't be done to last. He stated that the inside of the frame (where the wiper piece travels back and forth inside) warps outwards, and if it were to be rebult, it would only work for a short time, then stop working again. Well, so I went and bought a rebuilt one for my car on Ebay, and it worked great! Well, after sitting for a few months, it has stopped working, just as the wiper man told me would happen.

OK, here is the question. Is there any way to bend pot-metal back into shape without damaging (cracking) it? I was thinking that maybe by applying some heat to it, and using a vice to SLOWLY bend it back inwards just a little at a time. You know, heat it, then turn the vise just a little, and leave it there for a number of hours. The next day, do the same until the insides flatten back out a bit.

Opinions? I have never worked with pot-metal in this way, and would be interested in hearing if others have ever tried this before. Also, if this can't be done, I have another idea on how to correct this. I will keep this idea to myself for now, but if I try it, I will be sure and doccument the process with photos, so if it works, I'll post the photos so others will see the method that I use.

I would be very interested in hearing any and all feed-back on this one, and thank you!

Link to post
Share on other sites

Interesting idea. Pot metal has a brittle crystaline structure that tolerates very little bending. On the other hand it warped by itself over time so perhaps you can warp it back over time. On the third hand the warpage may be due to internal stresses working themselves out over time and you are screwed. I say give it a try and report back.............Bob

Link to post
Share on other sites
I spoke to the wiper man about having my wiper motor rebuilt. He told me that by the year of my car, that there is a good chance that it couldn't be done to last. He stated that the inside of the frame (where the wiper piece travels back and forth inside) warps outwards, and if it were to be rebult, it would only work for a short time, then stop working again. Well, so I went and bought a rebuilt one for my car on Ebay, and it worked great! Well, after sitting for a few months, it has stopped working, just as the wiper man told me would happen.

OK, here is the question. Is there any way to bend pot-metal back into shape without damaging (cracking) it? I was thinking that maybe by applying some heat to it, and using a vice to SLOWLY bend it back inwards just a little at a time. You know, heat it, then turn the vise just a little, and leave it there for a number of hours. The next day, do the same until the insides flatten back out a bit.

Opinions? I have never worked with pot-metal in this way, and would be interested in hearing if others have ever tried this before. Also, if this can't be done, I have another idea on how to correct this. I will keep this idea to myself for now, but if I try it, I will be sure and doccument the process with photos, so if it works, I'll post the photos so others will see the method that I use.

I would be very interested in hearing any and all feed-back on this one, and thank you!

No Way! I've tried slowly straightening a piece of bent pot metal trim back to straight as an arrow and while I didn't break it resisted. After several weeks of applying an ever increasing pressure it had changed little. A casting like a wiper motor housing is not going to change. Though it won't be correct, the best thing to do is to buy one of those electric wiper conversions that were commonly available in the late 1950s and early 1960s. They crop up on ebay regularly from a guy that refurbishes them. If you don't see one that might fit your car drop him a message from one of his listings and ask if he as one that will work. Just be prepared to give him the original part number and manufacturer of the one in the car.

I stopped screwing around with old vacuum wiper motors four years ago and now don't have to worry about getting caught in a shower. Now the only problem I have is finding blades of the correct length.

Jim

Link to post
Share on other sites

OK, I get the point. BUT, have you ever applied any heat to the metal either just before trying to bend it, or maybe even better, WHILE it is being clamped? Unfortunately, I am afraid that it will not work, but I believe it is worth a try.

I wasn't going to mention it now, but what the hay. Here is the other idea I have to correct this problem. The "bowing" or "warping" is in the very center, causing the little wiper inside to have a tendancy to stop, or loose power when the it gets to the center of the motor. I have used many different types of epoxy over the years. Some are quite thick, while others are very thin. I will get the motor perfectly level horizontally, and pour a bit of the really thin epoxy in the middle area that is warped. This should then level out in the middle where the warpage is. The exopy will haden like glass, creating a glass-like smooth surface. If the epoxy were to be too thick of a coating, then it can be simply sanded and polished with the drimmel tool and a polishing wheel. Doing it this way would not disturb the metal at all, while bringing the inside deminsions to the correct measurments.

What do you think? Will it work?

Link to post
Share on other sites

Jim,

You cannot bend pot metal back into shape. "pot metal" is an alloy of zinc and any number of other low temp metals and varies from batch to batch. It will melt at as little as 750f.

That being said, the wiper motor for your car is nat that rare and you should be able to find a stable housing.

Have you tried Fickert?

Dennis

Link to post
Share on other sites

Dennis

I spoke to the "wiper man" who has been recommended to my by this site, and was told that if anyone can do the job, he can. He is the guy that told me that most of these wiper motors from this time period warped over time, and that it would be a waist of his time, and my money to send mine in. He also stated that if I sent my original one in, he would check it out, but the chances are not great that mine would be rebuildable. He also said that any that I bought from this time period may have the same problem. When rebuilt, they would would work fine in the beginning, but would not work correctly if let sit for a few months, which is exactly what happended to the one that I bought.

I think I am going to experiment with one of mine, just to see if it will work. The worst that can happen is that it will not work, so not much will be lost. If it DOES work, then many others might be able to repair their originals to keep their car completely original.

Link to post
Share on other sites
OK, I get the point. BUT, have you ever applied any heat to the metal either just before trying to bend it, or maybe even better, WHILE it is being clamped? Unfortunately, I am afraid that it will not work, but I believe it is worth a try.

I wasn't going to mention it now, but what the hay. Here is the other idea I have to correct this problem. The "bowing" or "warping" is in the very center, causing the little wiper inside to have a tendancy to stop, or loose power when the it gets to the center of the motor. I have used many different types of epoxy over the years. Some are quite thick, while others are very thin. I will get the motor perfectly level horizontally, and pour a bit of the really thin epoxy in the middle area that is warped. This should then level out in the middle where the warpage is. The exopy will haden like glass, creating a glass-like smooth surface. If the epoxy were to be too thick of a coating, then it can be simply sanded and polished with the drimmel tool and a polishing wheel. Doing it this way would not disturb the metal at all, while bringing the inside deminsions to the correct measurments.

What do you think? Will it work?

I think you will be changing the wiper action by reducing the chamber size, assuming I thoroughly understand your thoughts. Additionally, that wiper motor housing will have absorbed a certain amount of fuel residues if the vacuum source is from the manifold vacuum, achieving a bond may well be virtually impossible.

Jim

Link to post
Share on other sites

Methinks you should definitely try the epoxy fix. You might bring this one back from the dead and really, what do you have to lose?

The flapper won't care if it is rubbing pot metal or epoxy. As for adhesion, I suspect the epoxy will take to the pot metal quite well. Maybe rough up the surface with some coarse sandpaper beforehand to give it a bit of tooth.

If you end up with a bit too much epoxy in the cavity, I would suggest not using a Dremel (unless there's waaaay to much, Mr. Clumsy) but rather glue your sandpaper to a disc almost the same diameter as the inside of the housing and use that (manually) to finish the surface down to level. Use increasingly fine grades, of course.

Good luck.

Link to post
Share on other sites

Jim

I really will not be reducing the chamber size, I'll just be adding a bit of epoxy to the insides to compensate for the warpage that has occured over the years. The epoxy will only fill the larger than normal void created by the warpage, not the complete chamber. Its because of this warpage, that the wiper piece inside is not tight enough at the center of its wiper action, allowing air to leak past the wiper gasket inside. As far as the vacuum source goes, I was under the belief that the vacuum sucks air from under the dash, and not from the manifold. However, I do agree that the metal must be completely clean before adding a bit of epoxy.

Bamfords Garage

I agree about using some sand paper on the metal first, to give the epoxy some "bite" with the metal. As far as sanding it if too much epoxy is used, well....I am hoping that I will not have to do this. But then again, I wanted to have a back-up plan....just in case.

Link to post
Share on other sites

At the time I spoke to him (several months ago) he didn't have the type that I needed. He told me it is hard to find one of these without the warpage. The later ones were made better, and held their shape. I have already bought some rain-X, but I kind of like the idea of having working wipers. It may be a few months before I try my idea, you know, too many irons in the fire right now. I still think that my idea will work, but there is really only one way to find out.

Link to post
Share on other sites

The vacuum comes from the manifold, it is routed through the underside of the dash, usually up a door pillar. Can I ask just to clarify, the wiper motor is stuck or weak? Ive had both and stuck was easy. weak forced another line on the Hershey list. When the wipers arent working, or in case of failure, Rain-X works pretty good.

Link to post
Share on other sites

Herb, the vacuum driven wiper motor is not a cylindrical motor, it is a paddle drawn back and forth across a 180 arc by vacuum created by the engine. There is a valve that switches which side of the paddle the vacuum is drawing on, allowing for constant motion. These "motors" require air tight condition and occassional lubrication and any warp from pot metal (Which I don't think you can heat and bend, It will crumble in your hands because the crystalline bonds cannot be reformed and reflexing is only breaking more) can cause them to drag the paddle, allow air to slip by the paddle (again, light machine oil helps with that) or draw air through the seal between lid and body.

Link to post
Share on other sites

Sambarn

On mine, the vacuum line goes through the firewall. Here's what the motor does, and why it is doing what it does. First of all, this is a recently rebuilt motor. (the photo shown is my original motor which has not been rebuilt) It has all new gaskets and o-rings. If you were to look at the insides of the motor, at the mid-way point, this is the place where the assembly warps. Right after it is rebuilt, the leather gasket seals the inside wiper piece good. However, if the motor isn't used for a bit, then the leather has a tendancy to hold the shape of the insides of the chamber. Because the center ares has bowed just a little bit outward, when the wipers are turned on, when in inside wiper piece gets to the center part of its action, then there is vacuum (air) leakage at this point. If played with enough, it will start working. the problem is, the longer it sits not being used, the more leakage there is in the center of its motion.

Herb

I have included a photo of the inside of the wiper motor to show you what I am talking about. Note the wiper piece inside. This used a piece of leather to seal the inside wiper piece. When that wiper piece gets to the center of its motion (where it is slightly warped) it looses power and will stop.

post-66697-143138472586_thumb.jpg

Link to post
Share on other sites

While I think the epoxy fix can work, here's another idea that might be easier and less prone to complications...

Consider a thin plate of metal (ie 0.005—0.010 shim stock), cut in a semi-circular shape to fit the housing and epoxied in place over the warp. That gives you a smooth, flat surface for the flipper to ride on, with no irregularities at the edge of the epoxy pool. The inside dimension is little changed, and although it is a few thou narrower, that just serves to make up for a bit of wear on the flipper.

Link to post
Share on other sites

Hey Jim,Had the same issue on a '37 Ford though probably not as bad as yours.Took the top off off the motor as you have in the pic and laid a piece of coarse sandpaper on a sheet of glass and sanded both halves as flat as i could.Reassembled with a couple drops of oil in the chamber and worked fine.At this stage you have nothing to lose.diz

Link to post
Share on other sites

Jim

I have used jbweld before, and all it is is another type of epoxy. For what I was using it for, it was not as good as other epoxys I have used.

JFranklin

The problem is, when the flapper is at the off position, the gasket on the flapper molds (conforms) itself to this size. When the wipers are finally used, the flapper gasket has sized itself to the off position, and when the flapper starts to move over the center position (which is slightly enlarged) there is air leakage. This is happening with a rebuilt unit, with new gaskets.

DizzyDale

I hadn't thought of that. What I need to do is to make a accurate measurement of the chamber to see exactly how much the chamber has warped. Good idea though.

Bamfords Garage

Don't know if this will work. I am assuming that both sides are warped, which means that a piece of metal would have to be added to each side. Again, I need to make a precise measurement to see what I am up against. I like your way of thinking though. Again, this may very well work. I hadn't thought of this either.

You guys are coming up with some good ideas about this. Thank you! Please, keep them coming. I know that I am not the only one who has had this problem, so which ever way works, its bound to help many others over time.

Link to post
Share on other sites
  • 4 years later...

This kickdown switch was in the oven at 500 F for a while then I drove a previously prepared wedge Gently between the block and switch,  I had an old carburetor that I put a propane torch to and found that it melted above 500F, using a "temple stick" something welders use to check welding temperatures.

  Your situation appears a bit more involved, maybe with some long machine screws a flat surface and some heat it might work.

Good luck,

Jay

post-83135-0-25425600-1453654338_thumb.j

post-83135-0-63323900-1453654363_thumb.j

post-83135-0-12203100-1453654385_thumb.j

Link to post
Share on other sites

Here is the deal with "pot metal", otherwise known as white metal or die cast. The problem is that there is no metallurgical standard for the metal. It is a mixture of several metals including, but not limited to, zinc, copper, tin, lead, aluminum, iron, and cadmium. All having different melting points. You can apply heat and have everything looking good and all of a sudden you wind up with a pile of melted metal. Bending it is also a risk because it is very brittle and with out warning it can break. There is another site where this very subject came up and several people chimed in on "I weld pot metal all the time" well, I have been welding for over 50 years, have a Class One Certification and a Welding Technology Degree and I can't weld it. I asked to see the results of those that said they can do it, but haven't seen them posted yet. Don't get me wrong, I think there might be someone out there that has done it, I don't know, I would love to hear from those who can weld or repair it.  Epoxy might be your only hope. Let us know the results.

Link to post
Share on other sites

How about making a wooden form the size of the opening. Use it to hold a piece of shim stock in place until the epoxy hardens. In other words combine your idea of epoxy, with the shim stock idea + a wooden former to hold it in place? I think this would be the only way to get a surface that was dead level, smooth, and an equal distance from the other side.

 

Or maybe a wooden former covered with plastic to make a smooth surface and just the epoxy, or possibly plastic aluminum compound?

Link to post
Share on other sites

Keep in mind that this post is from 2011.  My experience is that some pot metal survives and is stable and others deteriorate.  More seems to deteriorate and it probably depends on what the metal "mix" was when processed. Need to find a good solid part that isn't starting the decay process.

Scott

Link to post
Share on other sites

I wonder if a guy couldn't make up some sort of flycutter or hone that would pilot on the wiper shaft and use it to resurface the chamber? I know they are thin, but one that is minimally warped could be brought back to usefulness. An oversized paddle would have to be made but that would be fairly easy

Link to post
Share on other sites

If you want to reshape or bend pot metal try using a hot air paint stripping gun. I had a headlight molding on a 73 impala that was almost folded in half, by heating it with the airgun and slowly clamping it to a table I was able to push it back into place. The heat gun made the pot metal pliable like working with plastic. Try it. you have nothing to lose.

Viv.

Link to post
Share on other sites

They are ALL correct, I am a Metallurgical Engineer, no you cannot slowly bend pot metal back in shape. (Sorry) It was a cheap and inexpensive way to make a part back then. (like plastic today, buy a new one.)

Link to post
Share on other sites

If you want to reshape or bend pot metal try using a hot air paint stripping gun. I had a headlight molding on a 73 impala that was almost folded in half, by heating it with the airgun and slowly clamping it to a table I was able to push it back into place. The heat gun made the pot metal pliable like working with plastic. Try it. you have nothing to lose.

Viv.

 

It was most likely an aluminum alloy...............Bob

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...