Blasting and Painting

Eventually I hope my knowledge will allow me to restore old bikes. At the moment I'm working on learning painting and I have a couple questions.

To do home blasting do I need a chamber or do I just hook up a blasting gun and go crazy?

For painting what kind of gun would you suggest and brands of paint? I've done some spraybombs but in the end they're still just can jobs.

 

Knowing how messy blasting is (because I have a cabinet), definately get a chamber or similar.

The dust would be unbearable otherwise and you would go through a lot more blasting media.

 

I agree, blasting is a horrible process unless you set up properly to do yourself. You can buy a cheap blasting gun and a bag of media to get started but expect to have to do it out in the yard and downwind from your neighbour's washing line. In addition you will want pretty good protective gear (leather gloves, dust proof goggles, ear muffs and a respirator) because that media ends up getting into places you won't believe

After putting up with this for a few years I eventually built my own cabinet but I should have bought one because it took alot of mucking around to get it all working right, especially recycling the media. I found that the air pressure, nozzle size and media type have to be matched for it to work well. Excess pressure will smash the media to dust and makes recycling pointless (especially for glass beads which are great for aluminium but break up with over 40 psi at the gun).

Grit size, material and air pressure will determine the finish and what suits one job won't suit another. I found a 50/50 mix of garnet and glass beads at 35 psi gives a good finish on most castings, straight garnet at around 70 psi is good on rusted or painted steel. Soda is popular for carbs because it is water soluble and can be washed out. Soda usually can't be recycled so it is ideal for outdoor, one use applications. Make sure you thoroughly degrease, rinse and dry the parts before blasting. Then mask off any areas you don't want blasted with reinforced duct tape. Fill any threaded holes over 1/4 inch with silicone sealant and let dry, or use wooden plugs. Surface grease absorbs the impact making the process completely ineffective. Plan to paint steel within two hours particularly in humid weather.

A large cabinet takes up a lot of shop room, makes a hell of a racket and unless it is well sealed will make a mess. That mess is abrasive mess which is the last thing you want around your engine parts or shop tools. It is also the last thing you want to be breathing, particularly the galss bead variety which will give you silicosis of the lungs. Vacuum dust extraction and lighting is a must or you wont be able to see whats happening inside. You want to route that extracted dust through a good filter then outdoors. Compressor size will limit the speed of the operation (10cfm is an absolute minimum) For certain media such as ilmentite or bicarb soda you also have to keep the media dry or it will glug up and won't flow into your gun. This means some method of drying the compressed air after the compressor.

Water traps will take out some but unless the air is cooled first the rest will come out as droplets at the gun as the pressure drop causes the airborne moisture to condense. Industrial units use refrigerated air driers but you can cool the air just as well by putting a coil of air hose into a drum of water and putting the water trap after that. In my old shop I had a forty foot length of inch diameter water pipe down one wall, on a bit of a slope which allowed the air to cool and the water to be drained off at the low end.

Cabinets have the downside that the largest item you can blast will be whatever you can swing around inside your cabinet. If you just want to grab one of the cheap guns and experiment in the yard go for it, it's the best way to learn and you will get a reasonable result for not alot of bucks, but it will make a mess!

If you are interested in building a cabinet I can post some pics of mine. Good Luck.

 

Amen to that!^^^
Nice write up Iandmac!

 

2nd that
I've done it with a winter coat zipped all the way up, leather gloves, hat on backwards, and a face shield. I had sand in my ears for a week. Still went in my eyes, mouth, and noes, and all down my coat, in my shoes, and pants. It bounces off of everything and gets everywhere. I am gonna look into building a blast cabinet.

iandmac, I'd love to see some pictures of yours.

 

I built mine out of an old freezer!

 

OK, here's the pics of my home made blast cabinet. Construction is welded steel angle 25x25x3 with 6mm acrylic (perspex) panels stuck in with silicone sealant. Some features to look at if you are considering building one yourself:

1. Airflow through the cabinet. The automotive air filter on the left lets air in, the fitting on the right sucks air and dust out. This creates an air flow from left to right which takes the dust away so you can see what you are doing. A pool vacuum hose on this fitting is connected to an old domestic vac cleaner I put out in the yard. Don't use a good one for this, the abrasive wrecks the bearings in the fan motors, I get about a year out of one then buy another for ten bucks at Cash Converters.

The stainless baffle on the right stops media from flowing out with the air, the solid stuff hits the plate and falls down, the airborne dust gets carried intot the tube. It works well. The vacuum creates a negative pressure in the cabinet which helps seal the lid down and also tends to draw dust back into the cabinet. I used a rubber lid seal but I'm going to replace it with self adhesive foam.

2. Angle of the vee in the bottom. Make it more than 45 degrees or the media will not flow. This one has the sides at 53 degrees because that was the angle of the machine I copied it from

3. Media pickup circuit. Notice the pvc tube along the bottom of the vee. This originally had five 3mm holes along its length to let the media in. I had to tape four of them off to stop the gun from blocking. You only need a small hole in that pickup tube. The gun works by using a venturi to create a vacuum in the pickup tube which draws media into the airflow. You need to keep the air in that tube moving, if it blocks with media it stops the vacuum and your gun stops blasting. This is the single biggest headache with this process. My pickup tube has a vent line to the outside so the air is continuously being drawn in from outside, through the pvc tube along the bottom of the vee and up into the gun. It still blocks occasionally but it can be cleared easily by a blast of compressed air into the outside vent. This backpressures the vent tube and blows the blockage back out of the small hole in the pickup tube.

4. Other items:

Lighting is optional but highly recommended, it's hard to see what's going on in there without it.
Perforated metal deck to let the media flow through for recycling. This is split in the middle to enable removal.
Toughened glass viewing window (replaceable for when it gets all frosted up, this is my second in over ten years).
Lid catch, I just thought it was a cool idea
Air supply is pretty conventional with water trap and regulator.
Very modest 12cfm v-twin compressor, perfectly adequate for the 3mm nozzle I use at 40 to 70psi.
Long gloves with worm drive clamps on large PVC pipe flanges (easy, cheap)
Adjustable feet (M16 bolts) to get the height just right.
The media in these photos is 50/50 #240 garnet and glass beads, my favourite mix, it's good for just about everything.

Any other home built cabinets out there?

 

Iandmac, that is a piece of art!!!
Beautiful work too...

 

iandmac you are the MAN!!!! Now get your tail over to my house and build me one!!!

 

I agree. This is a work of art. If you had it to do over again (not considering the learning curve) would you build your own again or would you buy one from a discount tool source. I would love to have a cabinet but the room it takes up and the cost of a decent sized unit keeps me from it. I used to rebuild vintage Indian and Royal Enfields (actually the gentleman who owned the shop would give me a task to complete) in the old days and used a bead blasting cabinet extensively. What a beautiful tool. He also had pneumatic lifts to get the work to the correct level. Nice......Very nice!

 

robert, aaawww shucks ... thanks

dwcopple, it's a bit far and there's a big ocean in between !!

wamaxim, nowadays I'd buy one because I have a bit more cash and not so much time. I built this in 1992 when such cabinets were quite rare and very expensive (upwards of $3000). I had trouble even finding a decent one to copy the hopper angle from. These days they have become much more popular amongst the hobbyists and so the importers have brought the prices down as volume increased.

Having said that I get a kick out of building my own gear and there's nothing too complex about the construction here, it's just welded steel and perspex stuck in with silicone. I made the frame first then measured and sketched the panels and went to a local sign making company to get them cut to size. I got a local sheetmetal shop to bend the couple of wierd angled horizontal pieces on the sides and the lid out of 3mm sheet. The gun was an old one I scrounged from a junk sale and the perforated metal was from a scrap yard, I just cut it down to size. I was heavily into 4WD's back then and had a few cylinder heads to blast, that's what dictated the size. For bikes I'd probably want something a bit deeper so I could swing a tank in there. You can only reach so far in though so it has to be practical.

I've never regretted the few weekends it took to put together though and it's paid for itself a hundred times over in convenience alone. As you can see, it didn't cost very much to build. It's also a great conversation piece when people visit with beer

 

I've seen nice cabinets made from 200gal home heating oil tanks cut around about 1/3 of the way down, then hinged on the back. Obviously there are issues with cleaning the tank beforehand.

 

In our area, there's a place called Ublast, where you can take what-ever project your working on, and blast it in their cabinet ... for a few bucks

 

Mods,

Since Iandmac did such an informative and stellar write-up, how about making this a sticky somewhere here. In many years and countless forums, i've never seen anyone take the time that he has to teach blasting, A-Z.

If ever a thread deserved it, this is the one!!

Thanks iandmac, I learned a lot from this....and I've been doing it for a while. I can only imagine that this is REALLY helpful to a newbie at it.

jeff

 

how do you get a frame in that cabinet ?

 

I bet it ain't easy :roll: !!!

skillet

 

Making Carbs All Shiny On The Outside

News Flash !!

Just had my carbs apart for cleaning (again). I've been unhappy with the soda blast as it cleans but doesn't polish and the straight glass beads are too harsh on the soft metal.

So I tried 50/50 soda and glass beads. Only one word for the result FANTASTIC. Honestly, those of you with blasting chambers or even outdoor setups should try this one and see for yourself.

The soda seems to soften the impact of the glass beads, leaving a smooth textured finish. This is the closest finish to wet bead blasting I've ever been able to achieve with a dry blast, I'm absolutely stoked with this.

I've included some photos but they just don't do the surface finish justice. I'm thinking of shooting them with a coat of fuel resistant clear to make them look really shmick ... or not.

By the way, you need to plug the holes, I used wooden dowells and other random plugs to stopper them up, you don't want that abrasive inside the carbs (see photos below). For threaded holes use a couple of M5 and M6 screws with a bit of plumbers teflon tape to seal the thread. Fit the bowl and an old carb hat as well. When finished take out the plugs and give them a good sluice in the kitchen sink with hot soapy water then a hot rinse and air blast.

Beware ... photos of seriously attractive bodies follow ... if you are offended by carburettor porn stop here

 

REALLY does a NICE job!!!

skillet

 

Caarrrrbbb poorrnnnnnnn

It's.............so beautiful!

 

hot damn that finished product is awesome