Epoxy casting repair?

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- timleech
  
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posted
19 years ago

Thu, Sep 2, 2004 8:43 PM

(Posted separately to uk.rec.models.engineering)

I've got a badly corroded cast iron gearbox casing to repair. It's the reducing gear from a Lister JP marine. These have a water cooling jacket, superfluous on a 21hp JP2, but this one has evidently suffered from a past life with salt water passing through. One side of the water jacket literally fell off recently, and the owner was complaining that it was leaking oil. I've ground off most of the remaining water jacket, to get at what was behind. After removing loads of scale, I'm left with gearbox side walls which are paper thin in places, and perforated on one side. There should be enough mechanical strength left in the webs through which the retaining bolts pass. I reckon the only satisfactory repair will be by getting it grit blasted, & then coating the sides with epoxy. Welding is, to my mind, out of the question. Any suggestions as to what is a good epoxy to use? Or should I just bite the bullet & contact the local Belzona rep, with the consequent emptying of wallet?

Cheers

Tim Tim Leech Dutton Dry-Dock

Traditional & Modern canal craft repairs

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- Tom
  
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posted
19 years ago

Thu, Sep 2, 2004 8:56 PM

Belzona is the bees knees for a lot of repairs, however as you say, the price can make one wince! :-(

Devcon products tend to be cheaper in your application..

Tom

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- Andy Dingley
  
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posted
19 years ago

Thu, Sep 2, 2004 10:40 PM

Got a picture?

Why is welding out of the question? What's the problem?

There's always more than one way to skin a cat.... I once fixed a tractor gearbox by making an entire oiltight inner box from mig-welded steel sheet, then just cosmetically fixed the cast iron outer with car body filler. If you don't mind the appearance, then there are all sorts of evil bodges involved steel sheet wrappers on the outside, screwed to tapped holes in the webs and sealed underneath with Hermetite.

If the walls really are paper-thin as you describe, then I'd be looking to replace them, no matter how troublesome it was. Cast iron just isn't happy in really thin sections, it's brittle, it's porous, it's just bad news.

Is JB Weld available in a sensible pack? Otherwise it probably depends on what your local favoured supplier offers. I think Araldite and Devcon both have their own magic products for this. Personally I use West System's vanilla epoxy and mix my own fillers into it, as needed.