Grit blasting at last

[fizzy]

Equipment used
Clarke 7.5hp 270L 3 phase compressor and a 20 gallon Sealey style blast pot. Trust me you really really wouldn't want to use a smaller compressor. Many times I thought I should have just gone to a pro with bigger gear. 30cfm barely enough.

Finally got to the stage of blasting my trailer prior to painting with Jorun 90AL.
Weather the biggest enemy.
A million thanks to @DAPPH who helped massively.
Started on Saturday but wasted 4 hours trying to use crushed glass. Would run for 2 mins then clog the nozzle. Didn't help it was contaminated with metal particles. So much for recycling ! Even when I used a magnet and removed them it didn't help. Just too coarse for my 4mm nozzle.
Managed to source an alternative locally. Hardly any problems after that.
Took about 6 hours. Cleanup hard work.

Last pic was from a few days previously. Drilling through the pre drilled holes in the crossmembers. Floor is 9mm stokbord just as an infill with 6mm Ali checkerplate on top. Ignore my horrific uphill welding on the sides. Just practice. The side rails are actually held on with heavy spot welds from above. I am happy with my normal welding just can't do out of position.

 

[Erie Fred]

I rarely re-use, as I don't have helpers, and have experienced the same problems you had, mainly plugging.

Friends that are exceedingly cheap have tried all manner of tarps, shovels, brooms, etc.
And everyone screens the recycle when dumping into the pot.
And every single one has had so many plug ups, they cuss and swear to no end.

And a few have stopped recycling.

While a few soldier on......

 

[fizzy]

I rarely re-use, as I don't have helpers, and have experienced the same problems you had, mainly plugging.

Friends that are exceedingly cheap have tried all manner of tarps, shovels, brooms, etc.
And everyone screens the recycle when dumping into the pot.
And every single one has had so many plug ups, they cuss and swear to no end.

And a few have stopped recycling.

While a few soldier on......

No I didn't reuse the glass grit. It was commercial grade crushed glass from recycled bottles and jars etc!
We did re use the "other" media as we didn't have enough. As long as you run it through a sieve you never get problems - it just gets finer each time you use it.

 

[sako243]

May I ask. Why?...

I'd have just run it down to CLH and asked Mark to shove it on the next artic to the galvanisers. 1 week turnaround and job done.

They might have even been able to arrange for the lorry to stop by the unit to collect rather than trekking it to St Clears.

 

[Erie Fred]

This is why I only use the once thru stuff, the more expensive grit needs to be recycled,
and we run into problems.
One guy even had problems with grass/hay getting into his reclaim, made screening a problem.

what was the stuff you used after the glass that worked better ?

 

[fizzy]

This is why I only use the once thru stuff, the more expensive grit needs to be recycled,
and we run into problems.
One guy even had problems with grass/hay getting into his reclaim, made screening a problem.

what was the stuff you used after the glass that worked better ?

Not allowed to say - it is a top secret formula but readily available

 

[fizzy]

May I ask. Why?...

I'd have just run it down to CLH and asked Mark to shove it on the next artic to the galvanisers. 1 week turnaround and job done.

They might have even been able to arrange for the lorry to stop by the unit to collect rather than trekking it to St Clears.

Not a good idea to rivet aluminium sheets to galvanised steel. Also the Jotun 90 should outlast the galv.
Not only that but I have made or worked on almost every single part of this trailer. Almost finished now
Painting tonight - then another coat of Jotun 90 followed by Hardtop XP.
When properly cured the aluminium sheets will be rivetted on. Floor rivetted in. Then the mudguards and side running boards to make up. I have already started on those. Also in 3mm aluminium. Final job will be rear doors and later on a roof for it perhaps.
I think in total there will be about 400x 6.4mm rivets. Thank God I have an air rivet gun.

 

[Erie Fred]

Not allowed to say - it is a top secret formula but readily available

Light tan in color ? Kinda sandy feeling betwixt your fingers ?....
I agree, I have never found anything finer to get into the small divots
caused by rust.

 

[fizzy]

Light tan in color ? Kinda sandy feeling betwixt your fingers ?....
I agree, I have never found anything finer to get into the small divots
caused by rust.

Bit too fine actually. Should be great for my lathes and milling machines when I get around to restoring them.
I like the black grit slag stuff but didn't have any. I thought the half pallet of glass grit I had was going to be ok but not with a 4mm nozzle. My compressor won't run any bigger really. Scary how much air blasting needs. Road towed diesel compressor the best if you are serious about it. I think that is what @brightspark uses and a few others on here.
My 7.5hp was just enough. I once did a Land Rover chassis with a 3.5hp compressor - never again!

 

[Erie Fred]

I have blasted 1000's of lbs of abrasive over the years using a 10 hp electric and a 3/16" nozzle.
It just seems to be a perfect combination I stumbled upon.
I had a 200 cfm compressor running a 300 lb pot and a 5/16" nozzle, but you have to really
run fast to keep from wasting abrasive.

 

[fizzy]

I have blasted 1000's of lbs of abrasive over the years using a 10 hp electric and a 3/16" nozzle.
It just seems to be a perfect combination I stumbled upon.
I had a 200 cfm compressor running a 300 lb pot and a 5/16" nozzle, but you have to really
run fast to keep from wasting abrasive.

My next step is to fit a proper clemco sryle metering valve like @brightspark uses. I do have one but haven't fitted it yet. The supplied gate valve worked after a fashion but not much control.

 

[Erie Fred]

My next step is to fit a proper clemco sryle metering valve like @brightspark uses. I do have one but haven't fitted it yet. The supplied gate valve worked after a fashion but not much control.

I must have lucked out when I built my pot. I used a simple 1" ball valve with a long rod
going up the side to control it.
When blasting, where is your choke valve set at ?

 

[fizzy]

I must have lucked out when I built my pot. I used a simple 1" ball valve with a long rod
going up the side to control it.
When blasting, where is your choke valve set at ?

It is set at "about right"
I have to keep fiddling with it hence needing a decent valve.

 

[Erie Fred]

It is set at "about right"
I have to keep fiddling with it hence needing a decent valve.

Your choke valve should be wide open at all times, unless your clearing a plug up.
and then, just a quick close and back open.

 

[8ob]

I have blasted 1000's of lbs of abrasive over the years using a 10 hp electric and a 3/16" nozzle.
It just seems to be a perfect combination I stumbled upon.
I had a 200 cfm compressor running a 300 lb pot and a 5/16" nozzle, but you have to really
run fast to keep from wasting abrasive.

Fred, a pro I use for blasting was saying the more cfm available the less medium you need to use to make good progress, as in masses of hp air carrying smaller quantity of abrasive. He also reckoned that most of the abrasive's used on high cfm setups shatter/dull off and are not worth recycling.

Bob

 

[Erie Fred]

Fred, a pro I use for blasting was saying the more cfm available the less medium you need to use to make good progress, as in masses of hp air carrying smaller quantity of abrasive. He also reckoned that most of the abrasive's used on high cfm setups shatter/dull off and are not worth recycling.

Bob

Yes, that is my MO pretty much as well.
Also, smaller means more pieces per second thru a given nozzle size.

It really doesn't match sandpaper recommendations 100%, where some people
think coarser grit for heavier rust.

 

[brightspark]

Yes, that is my MO pretty much as well.
Also, smaller means more pieces per second thru a given nozzle size.

It really doesn't match sandpaper recommendations 100%, where some people
think coarser grit for heavier rust.

using course grit at high pressure can get heavy rust of quickly but leaves a well pitted rough finish and you need to go over it a few times to completely remove the rust. ok on oil rigs and bridges but you need finer media for wheels cabinets and the likes for a good fine finish for painting

 

[fizzy]

Your choke valve should be wide open at all times, unless your clearing a plug up.
and then, just a quick close and back open.

Forgive my ignorance but I thought the choke valve was what controls the grit? If mine is open too far it soon blocks or you waste the grit.

 

[brightspark]

Forgive my ignorance but I thought the choke valve was what controls the grit? If mine is open too far it soon blocks or you waste the grit.

the choke valve ak ball valve is fitted half way down the main air pipe and kept open. if its closed the air is all forced through the pot and helps clear any blockages with a quick shut and reopen. the bottom ones the grit valve. its the yellow ball valve on the down pipe

 

[Erie Fred]

Forgive my ignorance but I thought the choke valve was what controls the grit? If mine is open too far it soon blocks or you waste the grit.

The choke valve runs down the back from the Tee where the supply air comes in.
The hose on the choke valve supplies air to the underside where the sand drops down thru the sand valve.
If you close the choke valve, more air goes on top of the sand.
I'll try to dig up a diagram or pix tomorrow, I think Clemco has a nice diagram.