Technical Details on the New FullAuto Commando Cylinder Head from STS, in the US.

Ian James said:

I wish that I could afford one ,they sound liki the bees knees.On my 850 rebuild I have re tensioed 5 times in 400 miles and still it goes down(copper gasket) .No oil leaks for 100 ml and then out it comes.screw it down same same ,I am tempted to add 5fp to all when I do it again.I dount think that the head is cracked because it dostnt weap until it comes lose. Any ideas ? And yes a great post Cheers Ian

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Unless there's some other identifiable problem, I'd guess that it's likely that what you're seeing is the "metal creep" that's a problem with aluminum alloy. It comes from load/pressure or a loss of mechanical properties due to overheating. The better alloys resist the mechanical load and they resist temperature changes better. The factory alloy is good - in fact, miraculous in it's time, but the newer stuff is better. It also helps if there's more "meat" around the seating areas for head bolts and nuts for studs and wider gasket surfaces. So, "creep" can be minimized by choice of alloy and design of the part.

worntorn said:

The composite type does seem to have more success, however when they blow it tends to be quite magnificent. The copper gaskets just bubble and ooze away but the bike still runs.
Judging by the Maney 1007 result, I'll never get a perfect seal.
I might try Cometic for a custom gasket.
Hopefully I've got the cams timed properly so that only one piston is trying to push the head off at any given upstroke!

Glen

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I got busted on that two piston push concept. Thanks for reminding me only one of them fires at a time. ha

No problem, we are thankful that it's only one, otherwise it would definitely cause the Scotty syndrome.
As in " She just won't take it Captain, the main reac-tor is going to blow!"

Blewdy Yaink said:

So, "creep" can be minimized by choice of alloy and design of the part.

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And by choosing fasteners of the appropriate strength

gortnipper said:

I think the original and CNC AUS FA heads were 6061 T6?

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That's right.

mdt-son said:

That's right.

First ride with NEW head

Well guys, I've finally got my MK1 850 back with it's new Fullauto Technologies head and I rode it first yesterday and then for a few hours today. Apart from some muck in the carb (34mm Mikuni) which gave me the half throttle blahs, it was great. I had to fiddle with a few carb adjustments to...

www.accessnorton.com

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I'm really confused now. For over 50 years now I've read 6061 is a wrought alloy and not a casting alloy. I've never done any casting, and am for sure not an expert on the subject, but it does make me curious. I found this explanation on an engineering site, in response to the question, "Can 6061 aluminum be cast?" The grammar isn't great, but the explanation sounds reasonable to me.

"6061 standard is specific to wrought material. Casting alloys (and there are alloys that are functionally equivalent to 6061). Yes they are cast as an ingot but they are roll formed afterwards and that changes the metallurgical structure, this doesn't happen in cast parts so alloy additions have to be made to compensate for that lack of grain refinement. Cast grain structures are fundamentally different than wrought structures and it affects the performance of the part in different ways. When converting a part from a machined or welded process to casting, that needs to be kept in mind."

Maybe Ken (Fullauto) was referring to the casting equivalent to 6061, whatever alloy that is.

I did find references explaining that A356 (casting alloy) and 6061 (wrought alloy) have 94% of their composition in common. If Iunderstand it correctly, the principal difference in composition that affects casting ability is the low silicon content of 6061, which makes the melted material much less fluid, making casting difficult.

Also found references to "squeeze casting" 6061 alloy, but the description sounds more like a forging operation that conventional casting. And it's nothing like sand casting cylinder heads. Also some mention of "centrifugal casting" of 6061 into sleeves and rings, but again, nothing like making cylinder heads.

Have I missed some new technology that allows cylinder heads to be sand cast from 6061 wrought bars, rods, or plates? I doubt it, but I'd be happy to be corrected.

If I live long enough, I'll probably see alloy cylinder heads made by 3D printers.

Ken

I wondered about the same. 6061 isn't really suited to gravity casting. Hopefully Ken (Fullauto) will chime in.

- Knut

@Fullauto @G81 Can Cycle ?

OK, let's climb out of a rabbit hole here and go back to some basics.

I cannot speak about the Australian "FullAuto" castings. I have been interested in the casting of Norton cylinder heads ever since I was introduced to the concept of using Rolls Royce aviation alloys for the stock Commando heads in 1972. It was a source of pride at the factory that the RR53B alloy was used in the stock heads. RR53B was originally developed as one of the High-Duty company's alloys in a coordinated research program between High-Duty and Rolls Royce. Aluminum alloying was still in its infancy at the time that the Rolls Royce alloys were introduced. The alloy "Duralumin" was introduced especially for aircraft (structural) use in a full production process about 1909; duralumin is an aluminum-copper alloy, it's considerably harder and stronger than pure aluminum but duralumin adds little in heat resistance to pure aluminum.
High-Duty alloys began their research into alloys specifically for high-output engine alloys shortly after WWI and the discovery British National Physics Laboratory that adding nickel to aluminum created an alloy (called "Y-alloy) that retained its strength under heat exposure. See https://en.wikipedia.org/wiki/Hiduminium#High_Duty_Alloys_Ltd. RR53B used the aluminum-nickel-copper formula and added iron which also contributed to higher strength. This alloy was validated in Rolls Royce testing and introduced into special engines by about 1930. It was originally accepted as a casting material, even though the introduction of iron into the alloy causes some issues with grain structure as the iron aged in the casting.

In an attempt to create specialty alloys for structural use, both in aviation and other industrial processes, there was an effort to define and develop aluminum alloys for plate, strip, and sheet use, with high strength-to-weight ratios. In 1935, 6061 was introduced as a major improvement, in that it produced a strong light product with low production costs but with no provision being made for good casting characteristics. Developments during WWII (continuing with industrial development afterwards), looked to keep the high-strength, light-weight, low-cost characteristics of 6061, By the late 1950s, the Aluminum Association began the development of casting alloys in a series nominated by the letter "A" with a 3-digit numerical designation. The casting alloy A356 is one of the alloys in this series.

So, there's a logical path here. If we compare A356 to 6061, we can see that the two alloys are very similar.

The biggest differences are that A356 has a higher level of silicon (giving much better casting performance), with reduced copper, magnesium, and iron. But, generally, it seems to me that A356 is very much like 6061, except for the alloying for casting.

I can't speak for John but he and I discussed the issues of casting, molds and forms, design of the final component, and choice of material. Throughout the process of the transfer of the manufacture of the FullAuto heads from Australia, John completely reviewed every aspect. The STS version is cast in A356; I have no idea what the Australian heads were cast in, but; after thorough review with the American foundry and their experts, and after redesign of the castings to align with the 5-axis machining equipment and provide "more meat" in places (around the head bolt bosses and spark plug areas, more thickness at ports, a more solid headgasket area) that is beneficial, the STS product is different in many ways.

6061 is important in the history of development of alloys we have today, but it's not directly involved in the production of the STS heads.

mdt-son said:

I wondered about the same. 6061 isn't really suited to gravity casting. Hopefully Ken (Fullauto) will chime in.

- Knut

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Just as a guess on my part, could the Australian foundry been describing a casting alloy as "6061" as a general description of the alloy when the alloy used was actually "a casting alloy a lot like 6061"? I agree, 6061 has never been developed for casting (in fact, the opposite it correct) and a Commando head is difficult to cast in comparison to many others. It might be that that was a "misunderstanding through simplification".

Blewdy Yaink said:

6061 is important in the history of development of alloys we have today, but it's not directly involved in the production of the STS heads.

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Thanks for the details on the A356 to 6061 comparison. But I don't think any of us were claiming that STS used 6061 in their production of new heads. My post, and some of the others, were aimed at mdt-son's post which quoted Ken as saying that the first Fullauto heads were cast in 6061. I still think that has to be a mistake, but, again, I could be mistaken. Still waiting for an answer to that issue.

Ken

Blewdy Yaink said:

Just as a guess on my part, could the Australian foundry been describing a casting alloy as "6061" as a general description of the alloy when the alloy used was actually "a casting alloy a lot like 6061"? I agree, 6061 has never been developed for casting (in fact, the opposite it correct) and a Commando head is difficult to cast in comparison to many others. It might be that that was a "misunderstanding through simplification".

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Sounds like the likeliest explanation.

In searching for info on casting 6061, I did run into one Chinese site with a lot of poorly written info about how they could die cast "pure aluminum 6061". It was difficult to tell from their description what they were really talking about. If anyone needs some entertainment, this is the site. Maybe someone with more experience in the field than I could shed some light on it.


Ken

lcrken said:

Sounds like the likeliest explanation.

In searching for info on casting 6061, I did run into one Chinese site with a lot of poorly written info about how they could die cast "pure aluminum 6061". It was difficult to tell from their description what they were really talking about. If anyone needs some entertainment, this is the site. Maybe someone with more experience in the field than I could shed some light on it.

6061 Aluminum Die Casting, Best No. 1 aluminum 6061 casting

Pure aluminum die casting process is very useful in the die casting field like 6061 aluminum die casting, especially for automotive die casting parts, the reason the pure aluminum die casting part is very good for anodizing surface treatment

www.aludiecasting.com

Ken

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Thank you, Ken. I think that it is likely that there is a mix of "common descriptions" and precise technical terminology, leading to confusion and misunderstandings.

lcrken said:

In searching for info on casting 6061, I did run into one Chinese site with a lot of poorly written info about how they could die cast "pure aluminum 6061". It was difficult to tell from their description what they were really talking about. If anyone needs some entertainment, this is the site. Maybe someone with more experience in the field than I could shed some light on it.

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A distinction has to be made between the gravitation feed casting vs. the pressure / injection casting method, which is what this guy is discussing (compare this to the extrusion method). The latter method will work for 6061. Note high pouring tremperature, special ladle, large and short gates, and a pre-heated die, all measures aiming at preventing the molten alloy to start solidifying while on the run. Note also the simple object shapes.

The alloy used in Australia for pouring the head castings by gravity feed must have been a modified 6061. The dynamic viscosity of molten stock 6061 is simply too high to warrant good results for gravity feed castings (typical values are 0.6 vs. 0.013 mPa*s for A356).

- Knut

Me mumbling to myself: Look away, Derek, look away.... You do not need one of these... you have other things you could spend your savings on... grumble, grumble....

Derek Wilson said:

Me mumbling to myself: Look away, Derek, look away.... You do not need one of these... you have other things you could spend your savings on... grumble, grumble....

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On the other hand, I keep mumbling "Some things are worth 10 months of Noodle Ramen for dinner ..."

Timing is everything: right product + right time = open wallet, bleed.

I love the stuff I learn here.

gortnipper said:

@Fullauto @G81 Can Cycle ?

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yes