Dye Penetrant testing

[storkfoot]

I am building a Lambretta Vega engine from a casing that has had quite a bit of welding to cracks in the casing. I shall be building it as standard.

I'm still collecting a few engine parts that are missing. Whilst I am, I'm thinking of getting the casing dye penetrant tested to test the welding. I know I could build the engine and then compression test it but I'd rather check it out before I build it.

I am no engineer so the question is, is this a good idea?

[rosscla]

Can't see that you've anything to loose other than the cost of the test, if it finds any porous bits you can get it fixed while its stripped. If it's fine then you'll be reassured and not need to worry about it.

[carlos fandango]

What are you worried about ? A leak or welds failing ?
If its welds failing the i would of thought an x-ray would best.
If its a leak then i would of thought a pressure test would be the better option.
You could easily build the engine up with no internals, and make blanking plates for the areas you cant build, then pressure test.
My mate (a scooterist) has an NDT buisness, if you need any advise let me know and ill put you in touch

[storkfoot]

A mate has told me that it doesn't cost much and is something that a Precision Engineer shop does several times every day

In this case, I do have to take the casing in to get 2 of the 3 bearing flange screws out *, so I was going to kill 2 birds with one stone

* blow torch 5 minutes each side and an impact driver several times have failed to shift it and, yes, I did have the impact driver on the correct way (eventually)

[storkfoot]

You could easily build the engine up with no internals, and make blanking plates for the areas you cant build, then pressure test.

Good shout, Russ. I hadn't thought of this

I've never had a cracked casing but I have had mates who have chased engine problems for months and months before finding out that the problem was with the casing.

[rosscla]

It really depends where the welding is. If not in a pressurised area then a leak down test is no good.

My brother had a PX we used to call the Exxon Valdez because of the oil slick it used to leave, to this day we've never tracked where it came from.

[B-Race Tuning]

Is there a reason to start with a casing full of weld/ seized in screws, or a better casing sourced to rebuild?

[storkfoot]

I don't like to waste stuff. It's too easy to just dump stuff.

This is the casing (hopefully you can see it):

http://lunaownersclub.lifediscussion.ne ... -13th-vega

[rosscla]

Kinell...

Something must have really let loose to cause that and a leak down test is unlikely to be successful back there.

[B-Race Tuning]

I wasn't suggesting 'dumping', merely if you had doubts about the casing, that it may be better to start with good casings that potentially could then have saved you LOTS of money. Having now seen the photos, I'd have no real issues of building a quality spec motor into them, if that was the customers request. (I have been known to turn away "non-viable" builds. power or reliability non-viable wise). I have a 240 lump in the workshop with far worse repairs/ cracks in it.
Yours looks like it ONLY had gearbox failure??
Not sure dye testing is your best testing method. I agree, I'd blank off/ seal the casing and pressure test, ideally hot. 10psi air pressure and soapy water!