Grit blasting

[SpringbokParticipant @springbok]

[SpringbokParticipant @springbok]

Hi everyone
Seriously need a bit of help, I have had the only word is dumped into my garage a Fowler 3" traction engine which has been donated to our club. And asked to restore it, now to say a sad sight is an understatement as it look like someone has got a couple of buckets of black paint and thrown them at it.
I am after some advice on what type of system and supplier to go to, I have a twin cylendar Jun-Air compressor, model 12-50,

Displacement 120
CFM 425
Tank
Bar 50
Gals 13.2
This compressor has done sterling work for me as a spray system for all my loco's and running on air but grit blasting at the moment is a black art to me.

Look forward to help.
Bob

Edited By Springbok on 07/02/2013 10:35:19

[Chris TriceParticipant @christrice43267]

I can't quote figures but grit blasting or sand blasting takes large volumes of air. You may find your compressor working hard to keep up. You really need to be well set up to grit blast (large quantities of grit, proper booth etc). Finding someone who does it professionally is the way I'd go especially if it's a large item. However, if you're dismantling this model into smaller component, why not just buy a cheap plastic storage container and five litres of brake fluid from a motor factors? It'll strip most paints without the fumes associated with the more caustic paint strippers.

[chris jParticipant @chrisj]

Not sure how much help this is but I have a garden tractor that caught light and is now a rusted hulk.

phones the local sand blaster and he told me that it would be in the region of £40 to blast clean.I

[SpringbokParticipant @springbok]

Thankyou but need a little bit more help that that and I do not have a sit on mower

[John ShepherdParticipant @johnshepherd38883]

Springbok

I use one of these: http://www.axminster.co.uk/axminster-hand-held-grit-blaster-prod22989/?searchfor=800286

I use it with a modest compressor (2L, 8Bar/115psi, CFM 7.3) and buy tubs of grit from Machine Mart and although I have to stop and start quite a bit it does work. When I looked for a grit blaster, apart from one that is made to be used with air brushing, this one had the lowest air consumption I could find. I have only used it to remove flaking paint, light rust and to give a finish before painting so have not made it work too hard up to now. I always use it outside, with a makeshift booth made out of a plastic storage box and wear a mask and goggles. It pays to have a long airline so that the compressor air intake is well away from the action.

I think that you could use something much bigger with your compessor and this one may or may not cope with the job in hand but at the price you might still find it useful and a good starting point before making a big investment in heavy duty kit?

Hope that helps
Regards

John

[chris jParticipant @chrisj]

Posted by Springbok on 07/02/2013 14:11:45:

Thankyou but need a little bit more help that that and I do not have a sit on mower

Well, excuse me for trying to assist in some way,

[JasonBModerator @jasonb]

Bob are those figures right? looks like you are saying 120CFM and 50bar thats 700psi

 

I suspect from the model number 12-50 that you have a displacement of 120 lts or 4.25CFM compressor with 50lts or 13.2 tank with a likely max pressure of 8bar. or 120psi

What you really need to know if the FAD [ Free Air Delivery ] as this is what really comes out of the compressor not the displacement of the pump which is always the one they sell it to you with in your case 4.25CFM but FAd is likely to be about 2.5CFM.

I have heard good reports of teh small cabinets that the likes of Machine Mart do and you should just about get a rear wheel in there but they still need something like 10CFM FAD.

Edited By JasonB on 07/02/2013 15:57:37

[Chris GunnParticipant @chrisgunn36534]

I would reiterate what has been said above, you need a lot of air to grit blast continuously, we needed a big screw compressor to run our sand blaster, and we needed dust extraction to keep the dust out of the workshop, and still it was messy, it would be even worse in a home workshop. I think Chris J was trying to say if it costs £40 to sand blast a mower, why go to all to bother to get the sprayer, media etc, plus the cost of running your compressor non stop, (is the Jun air continously rated, by the way?), when £40 could get the job done, dust and hassle free. On the same tack, I have just had 2 front and 2 rear traction engine wheels in 6" scale sandblasted for £50 cash.

Chris G

[Chris CourtneyParticipant @chriscourtney72250]

I have one of the smaller Machine Mart blast cabinets (model number CSB20B). They specify a minimum compressor capacity of 10cfm at 80-100psi. I use it to bead blast small aluminium components, and actually run it from a 8,7cfm compressor. It does work, but the compressor is too small, I get away with it because the parts are small, but I spend a lot of time waiting for the receiver pressure to recover.

As others have said, you do need a lot of air, especially if you are trying to clean up heavily rusted or painted components. You state that your compressor is a 120cfm model… if this is correct then it is a pretty large compressor, even my humble 8.7cfm compressor requires a 2HP motor. If the figures are correct, then you have more than enough air for grit blasting with hobby sized equipment.

Chris C

[RJWParticipant @rjw]

The spec below was lifted off the web for the Jun-Air 12-50 compressor, and to be honest other than for very small localised blasting jobs, isn't up to any serious blasting work at all, the tank is way too small anyway and would have nothing in reserve!

I use a 15cfm twin cylinder 3HP compressor with a 200 litre tank bought new, and that runs out of breath fairly quickly!

If the engine is going to be stripped anyway, I'd cover any blasting and paint stripping on an individual basis, also be aware that blasting will not get rid of any paint that is in any way 'soft' it will simply absorb the energy in the grit, ditto any oil or grease!

Just my 2p's worth

John

Motor 0.68KW/1HP

Displacement up to 100 Lit/min depending on pressure

Max pressure 8bar/120psi

Air receiver 50 Litre

Voltage 220/240Volt

Power 680Watt

Weight 55Kg

Noise 45dB

[Phil PParticipant @philp]

Please have a look at a leaflet produced by the company I work for, it tells you what the air consumption will be for different blast gun configurations.

http://www.guyson.co.uk/assets/uploads/files/Blast%20Machine%20Services%20Leaflet.pdf

Bear in mind that the lower the air consumption the longer a job will take, depending on what the surface has been treated with and what you want to end up with will dictate what sort of blast media, and pressure you need to work with.

It sounds like you might be very disappointed with the results if you only have 2.5 cfm available, I would consider 12 to 16cfm a basic minimum if you want to shift rust and old paint.

As a very rough guide expect to produce approx 2.5 to3.5 cfm / horsepower.

Phil

Edited By Phil P on 07/02/2013 21:01:14

[Sub MandrelParticipant @submandrel]

I'd try the brake fluid. Ordinary paint stripper turned a black cruddy lump into a lovely little Zenith carb for me. Grit blasting could easily have damaged it.

Neil

[SpringbokParticipant @springbok]

ChrisJ

Sorry did not mean to sound offish.
The whole thing I would think weighs over a ton and rear wheels approx 3 feet dia so would need a very big tubIf my compressor is not man enought maybe nitromors. But would like to get it running for the club up our Ashton Court site for the summer season.

Bob

[JasonBModerator @jasonb]

Bob are you sure its 3" scale as 3ft wheels would put it in the 6" scale region in which case I would think about getting it done commercially at least all the larger bits.

[chris jParticipant @chrisj]

Posted by Springbok on 08/02/2013 06:07:10:

ChrisJ

Sorry did not mean to sound offish.
The whole thing I would think weighs over a ton and rear wheels approx 3 feet dia so would need a very big tubIf my compressor is not man enought maybe nitromors. But would like to get it running for the club up our Ashton Court site for the summer season.

Bob

No worries.

I think the size of it makes my argument somewhat more pertinent tbh.

Anyway, good luck with it.

Chris

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