Author Topic: Sand blasting the crankcases- Yay or nay?  (Read 982 times)

Offline owain

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Sand blasting the crankcases- Yay or nay?
« on: 13.03. 2017 20:33 »
Now that the engine is apart, I'm thinking of quickly blasting the crankcases with olivine sand (6 Mohs)...because that's what's in the sandblasting cabinet in the workshop. I thought it'd be a good way to get them looking like new and if all goes well, do the same procedure on my R3 engine. Any thoughts?
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #1 on: 13.03. 2017 21:19 »
 In spite of having the gear, I say nay because:
 1) you'd need to ensure you get all the grains out of every orifice

 2) Glass bead is better but still crap

  3) soda/Hydro/aqua-blasting is the g-o, much better and cleaner but not so cheap


 **edited 24/6/17   " 2)  gila bead is better.....to "Glass bead is better...."
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline jachenbach

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #2 on: 14.03. 2017 00:35 »
Walnut shell media would be much safer than glass beads. I've done it with glass. Won't do it again. Far too hard to ensure you've gotten it all out.

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #3 on: 14.03. 2017 10:08 »
Just good old degreaser and a high pressure water jet. If you want any shinier elbow grease and autosol.
You can never be sure ALL the grit is gone.
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #4 on: 14.03. 2017 10:09 »
I will only use soda in the cabinet for engine parts, it's slow compared to grit or sand but can simply be washed out and dissolved. Good for peace of mind
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Offline owain

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #5 on: 14.03. 2017 11:29 »
Righto, Good thing to check! We've got another cabinet with baking soda inside. I'll give that a go or use water at high pressure.
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #6 on: 14.03. 2017 11:59 »

 I dunno about baking soda, I think I was thinking of Washing soda, but may be mixed up with that being an electrolyte for reverse electrolysis rust conversion in fuel tanks *dunno* *dunno* *dunno*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online chaterlea25

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #7 on: 14.03. 2017 22:56 »
Hi Owain,
The danger with A10 cases is media getting into the oil passage from the pressure release valve to the cam trough, and the tiny bleed hole to the timing gears
There are pressed in plugs that would have to be drilled out to clean in there properly
You will also need to remove the anti drain ball and spring, theres a slotted plug inside the cases near the main crank bush

Nay from me *eek*

John
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Offline BSA_54A10

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #8 on: 15.03. 2017 08:46 »

 I dunno about baking soda, I think I was thinking of Washing soda, but may be mixed up with that being an electrolyte for reverse electrolysis rust conversion in fuel tanks *dunno* *dunno* *dunno*
Washing soda is NaOH, good luck trying to find any now days and if you do it will eat a hole in your cases in no time flat.
Baking Soda is NaCO which is a buffering agent ( ph 7) and will clean up the cases nicely then wash out in hot water, but it is soft & small so it is a slooooooow process.
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #9 on: 15.03. 2017 09:07 »
Quote
Washing soda, but may be mixed up with that being an electrolyte for reverse electrolysis rust conversion
yes washing soda is an electrolyte for electrolysis / rust conversion on steel - great fun. get it easily at spa pool shops - they use it for pH balance
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #10 on: 24.06. 2017 08:58 »
Going thru and looking for some specific tech ran across this discussion.

NEVER EVER EVER use sandblast or glass bead media, and use extreme caution using Walnut shell.
The primary reason besides the contamination and grit is simply it OPENS the castings,, I get very angry when I see an alloy engine part thats has been blasted, Its tell tale.  The surface of a casting has a certain finish to it and sealed to some degree.  All castings are not equal and some nasty castings make it out of the foundrys sometimes. (Norton has some of the gnarliest IMHO)  But BSA had their own foundrys and tended to be a superior casting operation.

When handling a part or engine that has been sandblasted it is hard to keep clean.. It picks up oil stains and finger or hand prints easily. 

The old school way was called "Bright beading" and involved walnut shell or NEW Glass bead and cranking DOWN the cabinet pressure to the point where the media did not explode when blasted. (The glass bead will shatter when blasting at higher pressures.. ) so, you crank it down to between 20 to 40 psi,, (Some experimentation required).  Then work over the casting. Follow this with an intense scrub with 2 grades of 3M scothbrite pads UNDER the stream or submerged in a solvent tank with diesel added.  This reseals the casting.

If that sounds tiresome, time consuming and a PIA, It is.

The modern standard, especially in aerospace is Baking soda.  Sure...you can go to the big box store and buy it in bulk, But you can search around and buy commercial grade baking soda MADE for media blasting and comes in different grades of coarseness.  You need a good blaster and nozzle, and different size than for sand or other media.. But it works really well. It DOES NOT alter the surface finish at all...  It just cleans nicely. REALLY Nicely!  The best part is you wash very thoroughly with hot water and it melts/dissolves.  The FAA has advisorys on this topic, as well as standard shop practice in most any aerospace shop or manufacturer.

There is ALSO several vendors in my area offering a waterjet-glass bead service and it is very nice!  Same deal as well for surface finish,, This is a bit more aggressive than Soda,, But the water jet stream cushions and then peens and reseals the metal castings.  All the top restorers are using this service in my areas..  But you come back to the problem of hidden grit with this method.  So,, I would recomend soda in most cases.

The exception is case and casting repairs.  I use to do a lot of repair work repairing castings as I worked in Aerospace casting manufacturing so, had a thriving side business going repairing damaged cases, heads, covers, primarys etc.   The key is using the right filler rod,, but we repaired all kinds of stuff others said was impossible,  I did all the prep and grinding,, then I paid welders where I worked to TIG weld the stuff,, then I would grind,.shape, sand etc the weld repairs, Then once properly textured we took it to a water jet-media vendor and had it blasted.  When done you cant tell it was repaired from the exterior.  The surface has that shiny diamond like textured finish that looks like a million bucks when done. In most cases a better surface finish than even the factory finish.
When doing a restoration or custom, It makes the difference between an amatuer resto and a pro one.

I can point out many of the bikes at the last Las Vegas auction and I know many of the restorers. The top money earners ALL use this process.
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #11 on: 24.06. 2017 09:14 »
Sluggo what's your view on blasting cast iron - like heads and barrels prior to painting?
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #12 on: 24.06. 2017 10:00 »
Well Cast iron is a totally different animal.  My specific concerns about alloy castings is the alloy has a sealed surface,, Like a heat treated camshaft. Surface is hard and inside is soft. 

But Cast iron,, That does not have those issues.  In my view it totally depends on what the casting looks like and what prev finishes were on it.  Is it rusty and covered with scale?? Id sandblast it.  Is it covered in a thick coating of paint, or worse,, multiple coatings of paint?  Id strip it in a chembath and then soda or sandblast it...

Some people powder coat a cast iron cyl and while I totally get the show boat trailer queen over restored look,,,I dont think thats very smart.

In aviation school, in order to pass each step we had "Practical" tests which involved demonstrating in front of an evaluator a task such as replacing guides, valve job, and painting a cylinder.   Back then we used Walnut shell on everything (Now soda media is the std) and then had to use a special zinc chromate primer and then a Catalyzed enamel or Poly black paint.

The trick was to prevent corrosion and totally paint ALL the orifices and between the fins, but not slather it on too thick.  This was rather challenging.   

While many people use a variety of rattle can paints to some degree of success,, What I use when painting (Since its a related topic)  Is I use either Diamont (RM) DE15 etch primer and its a thin primer with corrosion control and etch (Bonding) properties.  Lately I use Valspar VP50 as well and mixed at a etch only mix (You can use it as a etch surface primer or thicker as a sanding filler).  But in the paint trade its called a "*** coat" which means its only a very thin coating and almost see thru..  You are only applying enough material to provide a surface substrate for the following paint to stick and bond too.

I then follow with a single stage Poly catalyzed paint. (usually Valspar, but I have a couple other brands i like too).  Again,, uniform coating, but not too thick.

Alternatively (I know you didnt ask this, but its useful info)  I have been increasingly using special coatings.  I have a few shops locally that can apply specialized coatings such as heat reflective, or lubricating, or oil shedding.  For example piston tops are coated with a ceramic coating, the sides with a moly lubricant, and the underside with a oil shedder. 

But I have had a number of castings (engine cases) as well as cyls and heads done in a semi gloss black heat dispersant.  It works REALLY well,,  reduces heat by a sizable amount by verified testing.  All of this has been extensively tested, proven and the results are there. I have several people I know who use this exclusively in racing and have been for 20 years.

This is one shop near me, and great people. There products are tested on the Land speed record racing circuit (Bonneville, El Mirage and Loring, etc etc)   Some guys wrote a book years back on
"How to hotrod your motorhome" and again, trannys, cooling systems, brakes, and engines all showed great performance increases.

See : http://finishlinecoatings.com/

While not universally popular,, I know Kenny Dreer very well, Vintage rebuilders and Norton America motorsports.  Kenny was using Finishline for coatings on many of his builds for the last 25 years. (He is now retired) and ALL the VR880 bikes had these coatings.
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Re: Sand blasting the crankcases- Yay or nay?
« Reply #13 on: 24.06. 2017 10:21 »
 I have a need too clear a couple of things up;
First (not important) I did a typo in my 'Reply #1 that I've edited' to "**edited 24/6/17   " 2)  gila bead is better.....to "Glass bead is better...."

 ..but then...;
Quote
Quote from: duTch on March 14, 2017, 21:59:23


     I dunno about baking soda, I think I was thinking of Washing soda, but may be mixed up with that being an electrolyte for reverse electrolysis rust conversion in fuel tanks *dunno* *dunno* *dunno*

Washing soda is NaOH, good luck trying to find any now days and if you do it will eat a hole in your cases in no time flat.
Baking Soda is NaCO which is a buffering agent ( ph 7) and will clean up the cases nicely then wash out in hot water, but it is soft & small so it is a slooooooow process.


 Ok I concede I mixed up the Washing Soda (NaCO) for Baking Soda, but did qualify that in advance...but I'm sorry Trev, but believe 'Baking Soda' to be Sodium Bi-Carbonate NaHCO3,  and which when added to Tartaric acid becomes ' Baking Powder'.... *conf*

 So I don't think NAOH (Sodium Hydroxide) is part of the equation- so to speak *????*

  I think I got that right  *eek*

Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline coater87

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #14 on: 24.06. 2017 13:56 »
 Lets forget about surface appearance and oil shedding for a minute.

 There is no faster way to ruin aluminum casting than sandblasting. Besides maybe an idiot with a bastard file or a rotary burr.

 Can it be done? I have seen it done successfully, yes.

 But there is also a swap meet I attend every year full of aluminum castings that were cleaned up for quick sale via sandblasting, and they are ruined. Sandblasting is aggressive enough to quickly remove aluminum, and depending on what you are using for media it only gets worse.

 The major problem is mating surfaces, they take a beating. They may look clean, and new...but they are no longer flat enough to seal like they should.

 Really, its safer to do anything else besides sandblast because it can be so aggressive.

 Some guys swear the best finish is gotten with a fine bristle stainless steel brush and diesel fuel mixed with oderless mineral spirits.

 I like the look of vapor blasting, some guys hate it.

 My good friend likes the look of brand new glass beads as mentioned earlier ( the cases look too shiny IMO).

 Do whatever gets the cases to look the way you want, but dont wreck them in the process.

 Lee

 
Central Wisconsin in the U.S.