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| DIY crack testing https://www.ausmini.com/forums/viewtopic.php?f=2&t=37349 |
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| Author: | Wombat [ Sat Nov 03, 2007 12:02 pm ] |
| Post subject: | DIY crack testing |
I read this on another forum ; A DiY crack testing method is to soak the surface of the (spotlessly clean!) head in white spirit. Then wipe it dry and leave it to evaporate so that it looks bone dry. Then sprinkle talcum powder over the surface - any cracks will show up as the white spirit is drawn up into the talc. Is that an accurate test or do the pros use something more sophisticated? |
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| Author: | drmini in aust [ Sat Nov 03, 2007 12:08 pm ] |
| Post subject: | |
I use a dyecheck kit, it has 3 spray cans- 1. cleaner spray 2. red dye 3. developer (white powder) After the cleaner you spray the red dye on for 10-30 mins. Then wipe it all off, using some cleaner if needed. Then spray the powder. Any cracks show as red lines in the white dust. 
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| Author: | albino235 [ Sat Nov 03, 2007 12:33 pm ] |
| Post subject: | |
so just put some red dye in your white spirit 
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| Author: | andbat [ Sat Nov 03, 2007 3:39 pm ] |
| Post subject: | |
i pay $20 to the professionals they cover it in some kinda green conducting liquid, pass a current through it. any cracks show up as green lines/cracks where the current has had to go around the crack. (i belive that is what happens, something along those lines) |
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| Author: | drmini in aust [ Sat Nov 03, 2007 4:37 pm ] |
| Post subject: | |
Yes there are other (probably better) methods, some (eg magnaflux) even can detect sub-surface cracks. But they all cost money. If a Mini crank is cracked, a $15 dyecheck kit will show it just as well. Beware the old `ping' test with a spanner on the crankwebs- it's not always infallible. Chong had an 1100S one that passed that, but GR found a big crack in it. It was toasted.... 
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| Author: | EST-071 [ Sat Nov 03, 2007 4:40 pm ] |
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Doc, where do you get the dyecheck kits from? Cheers Pete |
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| Author: | drmini in aust [ Sat Nov 03, 2007 4:52 pm ] |
| Post subject: | |
Blackwoods carry them.
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| Author: | gafmo [ Sat Nov 03, 2007 5:44 pm ] |
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| Author: | mini-dunger [ Sat Nov 03, 2007 6:38 pm ] |
| Post subject: | |
for a head I would have it done by a pro with the ultraviolent lights and the dyes and such. My head had cracks down into the ports so i probly wouldnt have seen it if i did it myself. Using dyes on a cranks fine though as theres no sneaky places for cracks to hide. |
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| Author: | buztoy [ Sat Nov 03, 2007 6:44 pm ] |
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hey gaf or any one else any pics of a crack with that red dye test, no pics of a$$ cracks thanks
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| Author: | gafmo [ Sat Nov 03, 2007 7:18 pm ] |
| Post subject: | |
I have been Very Lucky with cranks..every one I have, have no cracks Including the Cooper S Crank  \
but I did get it done by Spiro from St George Cranks
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| Author: | DOZ [ Sat Nov 03, 2007 9:25 pm ] |
| Post subject: | |
There are a number of crack test methods that can be done but the penetrant method is by far the easiest at home....btw the fastest crack test with anything magnetic is a mag particle bench. This uses fine iron filings that glow bright green under black light. Using the magentic field makes the particles congregate around a defect, even ones slightly below the surface... Anyway, back on to penetrant... The history goes something like railways were being dusted with talc to remove excess oil and someone noticed a dry section had excess oil bleeding - it had a crack in the rail (from manufacture) and crack testing was born. The problem with different penetrant types is they have to get into the crack to start with, and then stay there while the excess is taken off before the developer is applied. If you remove too much then no cracks will appear. A small crack may be very hard to see so be careful and follow instructions with the cans. I would get a head crack tested using hot water, most cracks occur in places you cannot see anyway. Having said that Mini heads are pretty good for cracks, cranks are another story. For the original question of using white spirit I wouldn't recommend it. There is no contrast (red dye say) and you will find it very difficult to see small cracks. Stick to the kits, they are cheap insurance. Daniel |
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