Head dome cracking

[BellicoseBanshee]

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:

I have had much success with dye penetrant inspection (fluorescent penetrant to be exact). The biggest problem with dye or fluorescent penetrant methods is making sure the parts/components are adequately clean prior to the inspection process. You are correct, X-ray is definitely a better method, for it detects faults/defects under the surface.

 

FireHead, I was going to try and throw you a curve ball by mentioning magnetic particle, but I figured it wasn't worth trying to get one over on you... :biggrin:

[FireHead]

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).

 

6061 T6 can be stress relieved/aged, but it is not always done and that nomenclature doesn't say either way. Usually you'll have another four numbers after it.

 

2000, 5000, and 6000 series ally is nice to use on a developement engine as you can easily weld it.

 

If I was making premium domes for a a race engine, then I would be using 7075. :geek:

[FireHead]

I have had much success with dye penetrant inspection (fluorescent penetrant to be exact). The biggest problem with dye or fluorescent penetrant methods is making sure the parts/components are adequately clean prior to the inspection process. You are correct, X-ray is definitely a better method, for it detects faults/defects under the surface.

 

FireHead, I was going to try and throw you a curve ball by mentioning magnetic particle, but I figured it wasn't worth trying to get one over on you... :biggrin:

 

The penetrant method is definetly useful for informal and field crack checking.

 

I like the mag-particle method for unused parts, but if you have parts that have run in an engine and had a ferrous part fail near it, then you can get all kinds of hokey results. :geek:

[BellicoseBanshee]

The penetrant method is definetly useful for informal and field crack checking.

 

I like the mag-particle method for unused parts, but if you have parts that have run in an engine and had a ferrous part fail near it, then you can get all kinds of hokey results. :geek:

The only experience I had with magnetic particle was checking landing gear struts, etc...

 

Used fluorescent penetrant to check fan flades, etc, basically field testing just like you said. X-ray was used for engine mounts, etc...

 

Used eddy current for ribs, spars, etc...

 

It has been a while though. :cool:

[Chariot Performance]

6061 T6 can be stress relieved/aged, but it is not always done and that nomenclature doesn't say either way. Usually you'll have another four numbers after it.

 

2000, 5000, and 6000 series ally is nice to use on a developement engine as you can easily weld it.

 

If I was making premium domes for a a race engine, then I would be using 7075. :geek:

 

You are correct about the aging but t6 is not stress relieved. The stress relief is noted by the 511 for example after T6 which happens by stretching the material. The last one denotes straightening after stretching. My concern was with using just T6 because of the stress left in the material. I was also incorrect about the use of others of just t6 because it sure seems many of the products are t4 temper or o temper being much softer tempers and a concern in it's own right. I agree 7075 would be the better choice. Maybe with all this discussion we will decide wether it is actually needed.

[FireHead]

You are correct about the aging but t6 is not stress relieved. The stress relief is noted by the 511 for example after T6 which happens by stretching the material. The last one denotes straightening after stretching. My concern was with using just T6 because of the stress left in the material. I was also incorrect about the use of others of just t6 because it sure seems many of the products are t4 temper or o temper being much softer tempers and a concern in it's own right. I agree 7075 would be the better choice. Maybe with all this discussion we will decide wether it is actually needed.

 

7075 is probably overkill, since a commercial available dome is sort of a wear item.

 

6061 T4 is not something I would use unless I was planning on have some other posttreatment done to it after machining.

 

Possibly a 7000 series alloy would be an ideal candidate, but I think most of it is too expensive. I haven't kept up on raw material prices for a bit. What does 7075 cost per pound these days? :geek:

[blowit]

7075 is probably overkill, since a commercial available dome is sort of a wear item.

 

6061 T4 is not something I would use unless I was planning on have some other posttreatment done to it after machining.

 

Possibly a 7000 series alloy would be an ideal candidate, but I think most of it is too expensive. I haven't kept up on raw material prices for a bit. What does 7075 cost per pound these days? :geek:

 

 

 

We were quoted 4.20/lb recently!!!!! Jeeze, that is getting up to stainless numbers. I agree 7075 may not be needed for something like this. In our aerospace division, we run a lot of 7075 and you know when you bite into it. It runs very nice but VERY obvious it is stout stuff by the machines talking. Nothing like 6061. It machine more predictably as well.

 

 

 

Brandon

[Chariot Performance]

7075 is probably overkill, since a commercial available dome is sort of a wear item.

 

6061 T4 is not something I would use unless I was planning on have some other posttreatment done to it after machining.

 

Possibly a 7000 series alloy would be an ideal candidate, but I think most of it is too expensive. I haven't kept up on raw material prices for a bit. What does 7075 cost per pound these days? :geek:

Full length bars of 7075 about $3.00 lb and 6061 t6511 $1.90 lb. Not too bad on 7075 right now

[FireHead]

We were quoted 4.20/lb recently!!!!! Jeeze, that is getting up to stainless numbers. I agree 7075 may not be needed for something like this. In our aerospace division, we run a lot of 7075 and you know when you bite into it. It runs very nice but VERY obvious it is stout stuff by the machines talking. Nothing like 6061. It machine more predictably as well.

 

 

 

Brandon

7075 chips quite differently as well depending on the heat process you have on the given alloy, especially when turned. :thumbsup:

[FireHead]

Full length bars of 7075 about $3.00 lb and 6061 t6511 $1.90 lb. Not too bad on 7075 right now

Both of those prices are pretty reasonable. If I were making domes for myself, I would upgrade to 7075 at those prices.

 

I sware I have seen some folk's domes that looked and felt like they were forged from recycled pop cans.

[blowit]

Both of those prices are pretty reasonable. If I were making domes for myself, I would upgrade to 7075 at those prices.

 

I sware I have seen some folk's domes that looked and felt like they were forged from recycled pop cans.

 

 

That has pretty much been our determination here. We do not have one of those fancy laser things that will identify an alloy but a large local OEM does so we are going to try and arrange that. Our thinking is the failures may only be from sub-par material that may or may not even be 6061-T651. Probably just a 3 string company trying to save a buck and using junk bar stock.

[jbooker82]

I sware I have seen some folk's domes that looked and felt like they were forged from recycled pop cans.

 

Yea dude you just use a bunch of bottoms. It is already preshaped.

[FireHead]

Yea dude you just use a bunch of bottoms. It is already preshaped.

I hear they are a direct bolt in dome that gives you 150hp on a 65mm bore engine. :biggrin:

[Chariot Performance]

Thinking of the 7075 material for domes. Without knowing the cast alum designation for the cylinders I am guessing that 7075 may be harder than the cast used but likely not the 6061 t6511 so the .003 or .004 thou the dome sticks out may cause some problems caving in the cylinder wall on very top on some bores. ????

Edited January 9, 2009 by Chariot Performance

[FireHead]

Thinking of the 7075 material for domes. Without knowing the cast alum designation for the cylinders I am guessing that 7075 may be harder than the cast used but likely not the 6061 t6511 so the .003 or .004 thou the dome sticks out may cause some problems caving in the cylinder wall on very top on some bores. ????

That all comes back to the heat treatment of the alloy you can get some really soft 7075. I suspect Calvin's cylinders are made out of some type of Tenzalloy. OEM cynlinders are probably some nippon variant of 5000 series ally. :geek: