Update on the FE Power Cylinder Head Testing

[jayb]

Would pairing the shafts on the outer cylinders, and adding caps under the bolts for additional clamping force, be enough to eliminate the center bolts?

I ask, because I would think the termination of the shaft immediately after the end bolts of each shaft provides a significant leverage point against the shaft and bolt. The entire load is taken up by the bolt, in a very focused point. There's enough area in the middle of the head to extend the shafts a bit and use a cap to add clamping force (even if 2 shafts were used, instead of 4). Same goes between the outer cylinders. If the shaft were one piece on the outer adjacent cylinders, a significant amount of force could be added with a center cap, transferring the load over a greater area. The only area where it would be limited to a small cap would be the outer ends. I'd mention a bridged cap in that area, but think you'd run into valve cover clearance issues then.

Great minds think alike    Actually, my original design did use caps to hold the shafts in place, and no bolt in the middle.  You can see a picture of that design in the thread in the Vendor Classifieds, at the link below:

http://fepower.net/simplemachinesforum/index.php?topic=7336.0


This was the design before any FEA analysis, and although it appeared to be pretty robust, it would have had the same problem with flexing of the shaft in the middle.  I really want to avoid that, because of the length of the intake rocker.  It's over two inches long, and the clearance between the shaft and the rocker is only a couple thousandths, and if you put a five thousandths bend into the shaft at max lift, you are going to have an interference issue. 

I spent some time looking at the T&D race rocker setup for the FE, and that one uses bolts, no caps, and also a bolt between the rockers.  I've gotta believe that T&D knows more than me about this, so I took some cues from their design.  The other consideration is the additional material and machining time to make the caps; it is not a trivial issue, and would add significantly to the cost.

I don't know if using a single shaft for four of the rockers would help with the flex or not, but I don't like that idea because it means that removing the shaft would mean backing out the bolts while the shaft is under valve spring pressure.  Kind of like removing the rocker shaft on a normal FE valvetrain.  With individual shafts you can get the engine at TDC firing and take off the rocker pair without any spring pressure, and when you are running big springs I think that's important.  Plus it's just easier to service the valvetrain if it needs to come apart.  So I'm going to stick with a single shaft for each rocker pair.

[jayb]

I have a question or rather a concern about the weight of the steel rocker arms vs the original aluminium type. Is the FEA plot you showed intended for steel material? Noting that the aluminium versions are much more bulky in comparison to the plot. I guess I am hoping the weight increase of the steel adds more strength but isn't going to be a lot heavier. Especially at the extremities. (Then Jay will have to add even more bolts to hold down the valve-train.)

I'm not afraid of the weight issue, in fact Jesel says that their steel rockers are effectively lighter than their aluminum ones, for the same strength.  The steel rockers are going to be heavier overall, but the diameter around the shaft is smaller for less inertia, and of course the smaller cross sections by the adjuster and the roller tip will help keep the weight down.  I don't think I'll be giving up much in terms of performance with the steel rockers, and I'll get a huge longevity benefit...

[jayb]

I note that the FEA image doesn't have the c'bore, for the Torrington thrust bearings.

The counterbores are both in the exhaust rocker with this design.

[70bosscat]

Absolutely awesome work Jay. Most people have just a basic understanding of what it takes to pull all of this off. The amount of time, money, and brain power that is involved in a project of this magnitude is enormous and the fact that you're doing this as a one man show with a little help from your friends is incredible. I think the steel rockers in Thor's pic of the side by side comparison are your best bet strength and weight wise not to mention dead sexy. Thanks for your endless hours of dedication to this project. The market won't be huge but it's great to see this stuff out there period. Best of luck on refining this combo and I'm confident you'll get everything dialed in sooner rather than later. I just wish I was closer so I could see the goodies in person. Great writeup as always.

Ric

[Joey120373]

Since I love looking at rocker arms....

The LS style lends itself pretty well to getting a bolt directly under the rocker arm. Something like this, on a shaft with 4 or even 6 bolts might work.

https://tprace.com/products/ls7-nhra-legal-direct-bolt-on-rocker-arm

Of course this is all in my head, and Who knows if it would work. My guess is it’s already bean thought of.

[jayb]

That is an interesting idea, using a rocker arm that is already available for some other engine.  Not sure how well those would handle the side loads on the intake rocker, though.  I'm probably stuck with a custom design...

[Joey120373]

Yes, that rocker arm doesn't have enough offset at all. I posted that more as a design suggestion.
The LS rocker design is pretty darn good, but i don't think it would do well with the side loading, as you said.

But the open center design combined with a shaft could make for all kinds of bolts holding the assembly down.

My Father asked me to suggest NP3 plating as an option for the side or thrust bearings. Its a very tough electro-less Teflon impregnated nickle coating ( if i remember correctly ) . It has an extremely good friction coefficient and is tough as nails. He uses it all the time on custom rifles, but the company that does it also uses it on high end racing engine stuff.
it would allow for very thin thrust washers instead of roller bearings, more room for aluminum.

I think i prefer the steel or investment cast option though, strong, light, and no worries about fatigue.
 

[SSdynosaur]

I would think that steel rockers are the direction to go. It looks like they can be strong even with a lot of material removal. I think on these Pontiac steel rockers, they had a 1" offset and the adjuster was on a 5* cant, maybe the cant would help you if you don't have any built in.                                                                                                                                                                                                                                                                                                                   It looks like they did the same as far as a bearing pocket for the side loads on these rockers, you can see the cant toward the pushrod on the adjuster end. Angled toward the pushrod.                                                                                                                                                                                                                                                                                                                                                                                                                                                                       On these rockers, they have the aluminum version next to the steel versions on the same head, you can see how much more material they remove from the steel rocker compared to the aluminum (left and right mirror cylinders, but the same).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                Here is an even bigger offset on a steel rocker for a Hemi I think.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            Another steel rocker                                                                                                                                                                                                                                                                                                                         On some high RPM engines I have seen aluminum on the intake and steel on the exhaust, for cylinder pressure, but you could certainly do it the other way around or just go with steel on both.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Cool pics of all kinds of high performance rockers!

Long ago, IIRC it was Jim Butcher who ran the very last Top Fuel dragster with a BBC engine. Not that competitive with the 426 Hemi-based entries but as the story goes, the engine kept losing exhaust rockers as the forces in a blown nitro engine were pretty fantasic for the stud mount arm. No one at the time made a really strong steel rocker to prevent said breakage as no one else ran a BBC on heavy loads of nitro and high 6-71 blower pressures. Today, a custom-designed rocker would not be such a deal breaker as back then, a supplier needed a ton of orders to justify even a small production run.

Wow, there's a trip down memory lane! Jim (Bucher) and I ran out of the same shop at that time. My only offering is that he was very competitive within the Top Fuel ranks in that era "IF" the mostly OEM castings stayed together. Big if, but he was seldom out-powered; most loses came from parts failures. Honestly, at that point in history, most TF losses could be attributed to OEM part failures. Additionally, Jim couldn't even consider running a Chev aluminum casting cylinder head because the burnout alone would snatch 1 to 3 of the exhaust rocker stud mounts completely off the head; not stripped threads but the entire chunk of the casting. Therefore he was forced to run cast iron while all his competitors ran aluminum heads. Keep in mind this was the time period when the Gen 1 Hemi was still the tool of choice for most upper tier TF racers. The Gen 2 Hemis were just beginning to garner a bit of attention and there were only a couple of Mark IV Rat motors competing in the entire US. Your premise is 100% correct, the parts selection we routinely take for granted in present day situations hadn't even begun to evolve. Thanks for posting.

[cammerfe]

Have you considered lash caps for making adjustment instead of threaded screws? If I'm remembering properly, it's the valve end where the weight reduction does the most good. Dump the screw and used a pressed-in, hardened button to meet the pushrod.

KS

[WerbyFord]

Have you considered lash caps for making adjustment instead of threaded screws? If I'm remembering properly, it's the valve end where the weight reduction does the most good. Dump the screw and used a pressed-in, hardened button to meet the pushrod.

KS

Jay,
I read Ken's comment & wondered, if those adjusters are a pipe-style thread, are they putting the surrounding area of the (brittle aluminum) rocker in tension? I wonder how Bill did that in FEA. You can pre-load stuff in FEA but that's tricky too. Still agree on the steel rockers.

ALSO -
Would you have the LSA and ICL or advance of the cam?

In any case, in guessing at the intake so far in the Gonkulator, with the other stuff, the RPM always peaks at 7000-7200, so I wonder if there are more revs to be had!

[jayb]

The adjusters are straight thread, not an interference thread.  I've used different thickness lash caps on an SOHC, and to me they are a huge pain, but worth it on the SOHC because the adjuster is over the valve tip.  That is not the case with this valvetrain, so adjusters are the way to go. 

The cam in this engine is 112 LSA, set at 110 for the intake centerline.  I am certain more revs are to be had, gotta work the combination a little more...

[Cyclone Joe]

Jay and Bill,

What temper of 7075 did you go with?  If you used the T75 temper that explains the failure you're seeing.  If you have margin to go to the T73 (overaged) temper that'll really improve the fatigue behavior (although maybe not 100 fixing it).

The shot peening will really help that surface tension as well - putting everything in compression backs you back down the yield curve.

V/R
Joe Burnett

[jayb]

Joe, thanks for the info.  The temper was actually T651.  I'm not sure how that compares to the ones you mentioned...

[hwoods]

Faster Horses, Younger Women, Stronger Whiskey, More Money..... any updates?

[Barry_R]

T&D offers shot peening as an option on their aluminum rockers, and it's ben recommended on more serious stuff - but they actively try to steer me towards steel for those applications.  The roller/roller tip rockers they made for me on SOHC builds are all steel.  Expensive, but might be a lesson in there for us - maybe some past experience on their part.  I have seen some WW and Jesel stuff with a very significant "arch" shaped rib across the top - would that help in your design - maybe move some load away from the thin cross section area?