Author Topic: Sand blasting the crankcases- Yay or nay?  (Read 986 times)

Online Sluggo

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #15 on: 24.06. 2017 18:43 »
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

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

 Lee

--------------------------------------------------------

Amen,, hallelujah and say it on the mountain.   Thats it in a nutshell.   

I try to refrain, but I sometimes succumb to yelling at people on FeeBay for some of their ads, Last couple months a few that were over the top, including 2 that were charging a premium for allegedly restored bikes that were clearly bodge jobs and the cases, heads, and other alloy castings were all clearly sandblasted or media blasted.

I am into old cars as well,, And several times turned away engine rebuilds where idiots brought me parts that should never been sandblasted, and 2 cases where I sold alloy Datsun cyl heads and they sandblasted the heads and then wanted to return them for a refund.  I have no problems upon inspection refunding money, But dont alter a part and then change your mind and expect a refund.

That being said,, I AM that bastard with a carbide burr and rotary file..  I Used to do a lot of casting repairs and have a lot of time hogging out alloy to do so, or return a part to service, And at this point I am building a collection of display and cutaway engines for use at shows & events for our museum I volunteer with. Sometimes they will be on display AT the museum, sometimes at shows up and down the west coast and BC Canada.  Triumph, BSA, Norton and Harley.. maybe more if I can manage it.  I am using castings that are otherwise pretty far gone or scrap for the cutaways,, might do some that COULD be returned to service but those I wont polish or booger up.   

I will say up front that I am a total whore for polishing.  I have been roundly criticized for it.  Publicly castigated, Ridiculed and Mocked.  Several of my Triumph twins are polished cases, heads and covers.  Did 2 Norton twins as well (That was time  consuming) and one of my Goldstars and soon my Norton 961 prototype.  I wont ruin a viable and historically significant resto candidate,,  But my Goldie was already modified when I got it, and a BITSA to boot.  But I have a buffer and polishing setup and not afraid to use it.  (We call it BUFFZILLA as its a beast)
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Offline Kickaha

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #16 on: 25.06. 2017 00:34 »
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. 

I've been looking at those heat dispersant coatings as I thought they might benefit all the old air cooled stuff I tend to run

No one here that I can find has much info on it and a 300ml can is about $235
1955 BSA Gold Flash
New Zealand

Online Black Sheep

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #17 on: 25.06. 2017 07:04 »
I've just saved myself $235 + duty and postage by living in a cool climate. There just had to be an advantage to living in Scotland.
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Online Sluggo

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #18 on: 26.06. 2017 09:18 »
Rather than clutter up his posting on my off topic ranting, I will post a brief endorsement of my experiences of coatings, Heat dispersants, friction modifiers, oil shedding, etc etc.. and some I know of who also use them....
Hope you guys can get some use out of it, or feel free to ignore but Ill start a new topic.
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Offline East_Coast_BSA

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Re: Sand blasting the crankcases- Yay or nay?
« Reply #19 on: 01.07. 2017 18:42 »
Keep in mind that Glass Beading is a "Shot-Peening Process", not a cleaning process.  It's shot peening with much smaller media.  This is why the glass is round, it's not specifically intended to remove material (or contaminants).  It's primary purpose is to beat down the surface and get rid of stress risers and sharp edges.  Walnuts are better because they will remove unwanted grease and grime without changing the texture of the aluminum (the shells are softer than aluminum, this is also why the walnut media has sharp edges).  You're best bet is a liquid cleaner of some sort.  The small particles from walnuts will get into everything and anything and can be miserable to get out of small passages.