Sandblasting Rims Questions

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Bill Lee/Virginia

Senior Member
I am sandblasting and painting my Model A rims and do not want to overheat and possibly warp them. The rims have very thin old paint and light rust on them. What is the best medium to use? Sand, some type of shells, or other? Where is the best place to purchase the medium? What is the best air pressure to use? What other advice do you have? Thanks in advance. Happy New Year to everyone.
Bill Lee/Virginia Peninsula
 
Bill Lee/Virginia said:
I am sandblasting and painting my Model A rims and do not want to overheat and possibly warp them. The rims have very thin old paint and light rust on them. What is the best medium to use? Sand, some type of shells, or other? Where is the best place to purchase the medium? What is the best air pressure to use? What other advice do you have? Thanks in advance. Happy New Year to everyone.
Bill Lee/Virginia Peninsula
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Harbor freight has different medias, glass bead but slower cutting,aluminum oxide fast but dusty, sands, you need a "lot" of volumn air compressor, a thought would be to have done elsewhere at a shop set up to sandblast its inexpensive to have done I had mine done for $75.00 each and powder coated. Les Schawb has set ups but only a few colors on west coast. Won't warp them.
 

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I took mine to a local truck tire and wheel place and they sand blasted them and powder coated them black for around $30 apiece. Limited colors but the work and quality was good. You might look around and see if there is a place near you. They are usually near the expressways.
 
Bill, I severely doubt you could get a wheel hot enough to warp using sand unless someone just concentrated on one single spoke for a length of time.

I use aluminum oxide at about 45 lbs pressure. Sand has a habit of making the surface very coarse which requires more sanding.
 
I use fine sand that I buy at my local lumber yard that sells sand , I sift it thru a window screen , never a problem.
 
First off heat from sandblasting causing distortion is NOT correct.

You need to get the metal up to enough heat to get it to turn blue. I think that approaches 500 degrees, not going to happen. Think about it, you have to heat the area up to plastic stage for a heat shrink to happen. That means the metal would have to be so hot it would instantly burn you. But you can touch the metal no problem after blasting.

You have a lot of expanding gas which is how air conditioning works. So the air blast is taking heat away from the metal. Keep in mind when you blow out a candle you are taking away too much heat for the flame to continue combusting.

Distortion happens when too much energy from impact causes the surface to expand. This makes one side of the metal longer than the other. You get too much energy from too high a pressure or too much material in the stream. Distortion can only happen when enough thickness is stretched to make the metal move. So this only happens on thinner sheet metal and when it is not is a shape that can resist the force of the stretch. Curved areas are stronger and react different to the surface stretching.

You will not distort a wheel. So do not worry.

BTW, wheels take forever to blast at lower pressures in a glass bead booth. I found I could cut the time blasting in half by first letting the wheels set in an electrolytic rust removal tank. Depending on the paint your are trying to remove you may not need to do much blasting after ERR.
 
I just have a pro do the job. They come back like new and in very short order. Just be sure to primer them immediately after you do this or you will get rust.
 
Ever consider Electrolysis? It's cheap and it takes paint, grease, and rust off in hard to get areas. If you have the time! If you're in a hurry, have them sand blasted.
Terry
 
I've sandblasted for years with regular sand. I get it in hundred pound bags at a local home improvement store. I blast with a home made blaster running about 90 psi. I can post a pic if you'd like. You will not warp your wheels sandblasting them, if you did the metal was far too weak to consider mounting tires to.
 
Forgot to add if you are blasting your wheels yourself make sure you wear a good respirator and do it either outside or in a fairly well ventilated area. Silica dust is not something you want in your lungs
 
Kevin in NJ said:
First off heat from sandblasting causing distortion is NOT correct.

You need to get the metal up to enough heat to get it to turn blue. I think that approaches 500 degrees, not going to happen. Think about it, you have to heat the area up to plastic stage for a heat shrink to happen. That means the metal would have to be so hot it would instantly burn you. But you can touch the metal no problem after blasting.

You have a lot of expanding gas which is how air conditioning works. So the air blast is taking heat away from the metal. Keep in mind when you blow out a candle you are taking away too much heat for the flame to continue combusting.

Distortion happens when too much energy from impact causes the surface to expand. This makes one side of the metal longer than the other. You get too much energy from too high a pressure or too much material in the stream. Distortion can only happen when enough thickness is stretched to make the metal move. So this only happens on thinner sheet metal and when it is not is a shape that can resist the force of the stretch. Curved areas are stronger and react different to the surface stretching.

You will not distort a wheel. So do not worry.

BTW, wheels take forever to blast at lower pressures in a glass bead booth. I found I could cut the time blasting in half by first letting the wheels set in an electrolytic rust removal tank. Depending on the paint your are trying to remove you may not need to do much blasting after ERR.
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Thank you Kevin for that excellent explanation !
 
Before you take you model A wheels to the sand blaster, check them first for being true. I took eight good looking rust free 19 inch wheels to the sand blaster and had them all blasted. I painted all eight of them and then mounted up the best looking six of them. After driving the new restoration, I found out that half of the wheels had a bad wobble. The best four good ones are now on the ground and the best two wobbling wheels of the other four wobbling wheels are now mounted as spares in the wheel wells. I wasted half of my wheel restoration costs on bad wheels. :(
 
Not sure I "buy into" Kevin's theory about metal turning blue. We shrink metal all the time and it only needs to be hot enough to create steam when water is applied, --which is way short of the 500° mentioned IMO. Also understand that concentrated heat applied to a spoke area is what will warp a wheel. I do subscribe to his theory where the rapid air movement that is propelling the media is also carrying away most of the heat necessary to warp the wheel.


BTW Terry, are you sure Electrolysis will remove organic items such as paint and grease??

.
 
A tip for the hobbyist. When sand blasting Model A wheels, stack several wheels on top of each other to start. When you are blasting spokes of the top wheel sand will blow in to the spokes of the wheels below and save you some time overall.
 
My comments are based on science based texts or web pages I have read (this was a few years ago). I am trying to locate the sources.

Essentially the metal has to be in the plastic state for the atoms to move in on themselves. This occurs around 550 degrees which also happens to be the dark blue state of metal. Now the exact temp I do not know and it will be different depending on the type of metal. The rule of thumb that was listed was that you get the metal to where it take a blue color you have caused a shrink. Keep in mind I am combining information from a 1940's book on metal, a 1970 autobody text book, anvilfire.com, and a metal working forum so I am not sure I piece together all the info for an exact reference. If I find it all I will post it.

I would believe you were getting the metal up to the 400 area and causing a shrink, but at 212 I would say something is wrong. The would be putting boiling water on a section of metal would warp it and I know that is not true. If you have oil on the surface and it start smoking then you know you up around 300-400 degrees.

Electrolysis will remove some paints. It seems the process reaches some and can loosen and remove large sheets of some paint types. A guy that restores gas pumps showed it on his website. What ever was used on gas pumps came off in sheets easy as pie. It does not work on grease or well bonded paints. I know it does not take off the powder coat, epoxy and that thick red primer that nothing seems to touch on some old parts.
 
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