I have an old leather jacket that i removed the sleeves, to supply the gaunlets for the cabinet.
The lining was removed to reduce the bulk of the gauntlets, but sufficent weight and length is important to allow flexibility when blasting, and also the function of these is to protect you arms and seal the sand in the unit during working pressures.
I made 2 seals out of wood, which compresses and seals these items against the cabinet, the leather effecting and excelent seal around the join.
You can get nitrile gauntlets, like vets use for, well, you know the rest, but i will use my welder gaunlets through these gaunlets. If you get a chance of second hand nitrile ones, just make sure the guy (or lady) is not a vet!
These seals where laborious to make, and i made mine out of bits of oak, as they do take some mechanical force when you are working, twisting etc, but you do not want any leaks and sand etc blowing back at you, so i took my time on there construction.
Saturday, 29 August 2009
Hopper design
I soon realised that i neede to do a bit of geometric math to apply cuts and correct lengths, i viewed that a 20cm drop in height would be adequate for the base of the funnel assy to catch and give effective speed of removal of sand/media. the quicker the sand exits the cabinet, the less likely you are to lose visibility of your part in the resultant sand storm inside.
Veiwing from the front, i could visualize the drop of 20cm, then how to calculated the rest?
well after study, i used the old favourite, Pythagoras, the lengths of one side is 403mm to the top of the triangle formed, the other side (front and back of cabinet) would be 282 mm. As many a meerkat would say, Simples.
To these markings we have to add material to allow a seam to be formed, i added 25 mm to both front and back sections, this will allow pop rivet of the assy together.
This seam will be sealed using a general automotive or silicon sealer post rivetting.
I havent really made my mind up at this point on the final exit plan for the media, i will just leave a hole to drop media into a suitable catch bag. I would like to view this, perhaps a sealed pipe or similar will be applied, but we shall see.
Veiwing from the front, i could visualize the drop of 20cm, then how to calculated the rest?
well after study, i used the old favourite, Pythagoras, the lengths of one side is 403mm to the top of the triangle formed, the other side (front and back of cabinet) would be 282 mm. As many a meerkat would say, Simples.
To these markings we have to add material to allow a seam to be formed, i added 25 mm to both front and back sections, this will allow pop rivet of the assy together.
This seam will be sealed using a general automotive or silicon sealer post rivetting.
I havent really made my mind up at this point on the final exit plan for the media, i will just leave a hole to drop media into a suitable catch bag. I would like to view this, perhaps a sealed pipe or similar will be applied, but we shall see.
Start of blast cabinet mark up
My needs for the cabinet are:
It must take an alloy wheel of suitable size, i have a full set of wire wheels and hub adapters, and i want to stripped thes done and re-finish them.
It must be square of dimension, in order to accept the wheels effectively, the depth has to be adequate to allow working the piece, there is a pot to yield inside, but i believe that i can leave the pot attached outside when its tight for space when blasting lasrge parts, and run a suitable hose from the gun, with its nozzle re-attached to the other end. We will see later if that works.
The ducting is marked Duct Mate, and is over 4ft tall as a single piece, so after study, i found that the natural height to work at would be standing, so i drew 2 circles on the front of the ducting to suit my elbow height, this will be the glove wholes for working.
I then planned the viewing aperture, and had sourced a piece of scrap double glazing ages ago, so stripped that down, and split it to remove a single piece of 6mm glass. I cut this to 24" x 12", im a better metal worker than a glass cutter, but i managed it.
I then drew my glass size on the ducting, and allowed a sealed surface around this. I plan to just apply a small neoprene or draught excluder to the glass to seal against the ducting, at the low levels of pressure, the sand should be kept well within the confines of the cabinet.
I would not recommend bonding it as it will get a hard life, and eventually cloud over through bounce back, or even break through damage, most of these units have replace glass. It is also notice from other builders that using acryilc can cloud over quickly and delight the user in electrostatic shocks during use, happy days!
a happy middle road is glass, with a consumable shield inside the unit, like 2-3 mm of acrylic sheet taped in front of it (i hate taped mods, but maybe this is less hassle)
At this point i had the overall dimensions of the cabinet marked, was happy with the height i had been working at, but i do not require a 4ft high unit of course, so i line was drawn to form the "base" of the unit.
The key to a succesful blast cabinet is a base that a allows firm support of your parts, an allow or wire wheel, cast iron manifold, all way may bags of sugar, so i will be sourcing a suitable wire base. I believe in recycling so i will try to source this from an abandoned shop trolley or similar.
Most blast cabinets have a base unit formed to a point to collect the blasted media in a hopper form, attached to a bag or similar. This allows you to recycle the media, and you can filter out large contaminates. You can re-use most, but sand is one of the worst is it smashes and makes ever finer dust (read Silicosis) as your repeat its use. Obviously the small the sand grains, the less effective they can become.
The width of the unit is 700 mm, so i marked a cut line of 725 mm, the extra 25mm is to form a flange to allow bolting of the hopper/base. Both end of the original ducting sheet havea substantial flange on the, i will utilise this in the hopper design for speed of build, and is very well sealed.
On to hopper design next...
It must take an alloy wheel of suitable size, i have a full set of wire wheels and hub adapters, and i want to stripped thes done and re-finish them.
It must be square of dimension, in order to accept the wheels effectively, the depth has to be adequate to allow working the piece, there is a pot to yield inside, but i believe that i can leave the pot attached outside when its tight for space when blasting lasrge parts, and run a suitable hose from the gun, with its nozzle re-attached to the other end. We will see later if that works.
The ducting is marked Duct Mate, and is over 4ft tall as a single piece, so after study, i found that the natural height to work at would be standing, so i drew 2 circles on the front of the ducting to suit my elbow height, this will be the glove wholes for working.
I then planned the viewing aperture, and had sourced a piece of scrap double glazing ages ago, so stripped that down, and split it to remove a single piece of 6mm glass. I cut this to 24" x 12", im a better metal worker than a glass cutter, but i managed it.
I then drew my glass size on the ducting, and allowed a sealed surface around this. I plan to just apply a small neoprene or draught excluder to the glass to seal against the ducting, at the low levels of pressure, the sand should be kept well within the confines of the cabinet.
I would not recommend bonding it as it will get a hard life, and eventually cloud over through bounce back, or even break through damage, most of these units have replace glass. It is also notice from other builders that using acryilc can cloud over quickly and delight the user in electrostatic shocks during use, happy days!
a happy middle road is glass, with a consumable shield inside the unit, like 2-3 mm of acrylic sheet taped in front of it (i hate taped mods, but maybe this is less hassle)
At this point i had the overall dimensions of the cabinet marked, was happy with the height i had been working at, but i do not require a 4ft high unit of course, so i line was drawn to form the "base" of the unit.
The key to a succesful blast cabinet is a base that a allows firm support of your parts, an allow or wire wheel, cast iron manifold, all way may bags of sugar, so i will be sourcing a suitable wire base. I believe in recycling so i will try to source this from an abandoned shop trolley or similar.
Most blast cabinets have a base unit formed to a point to collect the blasted media in a hopper form, attached to a bag or similar. This allows you to recycle the media, and you can filter out large contaminates. You can re-use most, but sand is one of the worst is it smashes and makes ever finer dust (read Silicosis) as your repeat its use. Obviously the small the sand grains, the less effective they can become.
The width of the unit is 700 mm, so i marked a cut line of 725 mm, the extra 25mm is to form a flange to allow bolting of the hopper/base. Both end of the original ducting sheet havea substantial flange on the, i will utilise this in the hopper design for speed of build, and is very well sealed.
On to hopper design next...
My DIY blast cabinet
Hi everyone, thought i would share my build of a suitable cabinet to blast parts for my restoration of my MG bgt car,
I have always desired a blast cabinet, i have put a lot of components to blast companies, but it really is a hit and a miss if it comes back to an acceptable standard, and more often than not, it has been to rough a finish.
This was probaly due to them prepping to pre-poder coat standard, where as many finishes i require, and other restorers, needa delicate finish with minimal prepping to spray. I generally finish in satin hammerite or similar.
I had a friend come to me with pedals for his mountain bike that required stripping, he had tried Nitromors and elbow grease, but due to the intricate nature of the pedals, it was not going to plan.
I have a small compressor, a Clarke model from Machine Mart, and too small for blasting when you read the math on it all, but decided to buy a small spot blast gun and give it a go anyway.
I also stopped off and bought kiln dried sand from B & Q, and used that as my medium to blast with.
PLEASE NOTE, blasting with sand is extremely dangerous to your lungs, use a mask of suitable quality, if this gets into your lungs then it will stay there and cause Silicosis. see http://en.wikipedia.org/wiki/Silicosis
This stuff comes back at you fast, goes down your neck, in your hair (i wish), and unless you have eyelashes of a camel, wear googles all the time, along with a nice pair of leather gloves, so be warned, but its excellent fun to see old paint and rust form into a nice, new finish. I could hold the parts by hand without gloves, but it also gets a bit warm, and sand is not as inert as we all think.
It worked a treat, and did the whole job in under ten minutes.
The finish at this point was perfect, i think sand is too agressive for aluminium, but due to the relatively low pressure capabilities of my compressor, it achieve a fantastic finish, and reminded me of the satin finishes you get on custom pistols from Colt and Barettas, and i have always admired those.
At this point i understood that this blast cabinet was now a neccessity.
I discussed with my friend my needs, and my build would require a ducting panel, or similar, and he works with these guys all day! The result was he dropped of next day a full section of flanged, 1mm or so thick ducting section, fantastic!
So after some careful measurement, a review of the web and other chaps exercises in blast cabinet projects, which are many, particularly in the US, i started marking it all up to cut. so here goes....
I have always desired a blast cabinet, i have put a lot of components to blast companies, but it really is a hit and a miss if it comes back to an acceptable standard, and more often than not, it has been to rough a finish.
This was probaly due to them prepping to pre-poder coat standard, where as many finishes i require, and other restorers, needa delicate finish with minimal prepping to spray. I generally finish in satin hammerite or similar.
I had a friend come to me with pedals for his mountain bike that required stripping, he had tried Nitromors and elbow grease, but due to the intricate nature of the pedals, it was not going to plan.
I have a small compressor, a Clarke model from Machine Mart, and too small for blasting when you read the math on it all, but decided to buy a small spot blast gun and give it a go anyway.
I also stopped off and bought kiln dried sand from B & Q, and used that as my medium to blast with.
PLEASE NOTE, blasting with sand is extremely dangerous to your lungs, use a mask of suitable quality, if this gets into your lungs then it will stay there and cause Silicosis. see http://en.wikipedia.org/wiki/Silicosis
This stuff comes back at you fast, goes down your neck, in your hair (i wish), and unless you have eyelashes of a camel, wear googles all the time, along with a nice pair of leather gloves, so be warned, but its excellent fun to see old paint and rust form into a nice, new finish. I could hold the parts by hand without gloves, but it also gets a bit warm, and sand is not as inert as we all think.
It worked a treat, and did the whole job in under ten minutes.
The finish at this point was perfect, i think sand is too agressive for aluminium, but due to the relatively low pressure capabilities of my compressor, it achieve a fantastic finish, and reminded me of the satin finishes you get on custom pistols from Colt and Barettas, and i have always admired those.
At this point i understood that this blast cabinet was now a neccessity.
I discussed with my friend my needs, and my build would require a ducting panel, or similar, and he works with these guys all day! The result was he dropped of next day a full section of flanged, 1mm or so thick ducting section, fantastic!
So after some careful measurement, a review of the web and other chaps exercises in blast cabinet projects, which are many, particularly in the US, i started marking it all up to cut. so here goes....
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