blowit Posted January 6, 2009 Report Posted January 6, 2009 We have only seen a few cracked domes in the shop here and curious, to those who have seen them, can you explain either exactly where the cracks are showing up or offer a pic? Motor setup at the time of the failure would be helpful too. Just trying to do some R&D on a combustion process and need to confirm the origins of this failure mode. Thanks Brandon Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 bump No one has had dome issues? Quote
FireHead Posted January 7, 2009 Report Posted January 7, 2009 We have only seen a few cracked domes in the shop here and curious, to those who have seen them, can you explain either exactly where the cracks are showing up or offer a pic? Motor setup at the time of the failure would be helpful too. Just trying to do some R&D on a combustion process and need to confirm the origins of this failure mode. Thanks Brandon I have seen cracking that started near the top of the spark plug thread. It was due to overtightening and too thin of steup up to that area. I had one dome crack begining at the o-ring groove and heading up, but that was again due to having too thin of area in that region. I had several other failures that broke due to design or something that I was doing with them. I will get pictures when I get back home. :geek: Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 Thanks. We have noticed several domes out there that do not have sufficient radii on all edges to prevent problems but not sure if we are missing anything else. Quote
BellicoseBanshee Posted January 7, 2009 Report Posted January 7, 2009 We have noticed several domes out there that do not have sufficient radii on all edges to prevent problems. Are you referring to "off the shelf" domes or domes cut for special/specific applications? Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 Are you referring to "off the shelf" domes or domes cut for special/specific applications? I guess, either way really. We just have not seen too many failures and curious what guys are mostly referring to when they say they have a cracked dome. I could not see custom domes being too much different than off the shelf units unless they are extreme stroker cases or whatnot. Quote
BellicoseBanshee Posted January 7, 2009 Report Posted January 7, 2009 Any chance there is a material deficiency involved with the cracked domes? Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 Any chance there is a material deficiency involved with the cracked domes? That is one of the modes we are looking into. We feel alloy selection is a concern. Quote
BellicoseBanshee Posted January 7, 2009 Report Posted January 7, 2009 Do you have access to any kind of NDI test equipment (maybe eddy current)? A dye penetrant inspection would most likely reveal any surface cracks... Quote
FireHead Posted January 7, 2009 Report Posted January 7, 2009 Do you have access to any kind of NDI test equipment (maybe eddy current)? A dye penetrant inspection would most likely reveal any surface cracks... Generally we use an x-ray method to check for cracks in parts like that. A dye might work if the crack was prominent enough. :geek: Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 Do you have access to any kind of NDI test equipment (maybe eddy current)? A dye penetrant inspection would most likely reveal any surface cracks... Just magnaflux testing but a couple others just a phone call away if we really need them. Seems most of the problems we have investigated were induced by operator error. Specifically AFR,CCR, fuel selection, or timing. I blew some all to hell years ago with Nitro but I have to exclude that little hiccup. I did more than crack the domes.... Brandon Quote
deckheight Posted January 7, 2009 Report Posted January 7, 2009 I have only seen two total, both being re-cut 4mm strokers. I attributed both to operator error (not running the proper fuel). One detonation seized hard on the exhaust side, caught a ring and chewed up the dome. Not much guess work there... The other was sustained mild to moderate detonation, finally water seized. Had a radial crack toward the top on the exhaust side. So far, I have not seen any problems with unmolested parts. No pics, both domes are long gone... Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 10-4, appreciate the input. Pretty much follows the lines we have seen. Kaboom does bad things to an engine. Brandon Quote
Chariot Performance Posted January 7, 2009 Report Posted January 7, 2009 (edited) We have manufactured a lot of domes but aren't too interested in supplying them right now. With regard to material selection the likely culprit, if indeed material plays a factor, is the T value of the alum. Most use 6061 t6 which isn't stress relieved. The problem with that is when heated and cooled the stress are magnified possibly leading to failures. We as with all our products use 6061 t6511 which is artificially aged and stress relieved by stretching. This material is less susceptible to fatigue cracks as well as much stronger (not so soft). Edited January 7, 2009 by Chariot Performance Quote
blowit Posted January 7, 2009 Author Report Posted January 7, 2009 We have manufactured a lot of domes but aren't too interested in supplying them right now. With regard to material selection the likely culprit, if indeed material plays a factor, is the T value of the alum. Most use 6061 t6 which isn't stress relieved. The problem with that is when heated and cooled the stress are magnified possibly leading to failures. We as with all our products use 6061 t6511 which is artificially aged and stress relieved by stretching. This material is less susceptible to fatigue cracks as well as much stronger (not so soft). As you well may know, 6061 is bottom barrel Al and is usually not a suitable structural alloy anyway. Kind of leaning harder on alloy selection or supplier origin. We have seen three domes in the past month that have failed in rather ridiculous areas so it is time to discover why. Of course no markings on the domes so no idea who made them. R&D guys are wanting something to do anyway. Brandon Quote
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