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metal compatibility roller rocker conversion

metal compatibility roller rocker conversion

metal compatibility roller rocker conversion

(OP)
We are designing a rocker conversions for a SOHC race engine. The operation is via finger follower style rocker with 2 rollers under the cam and one on the tip for the valve stem. I need help to find the best material compatibility for the rollers and pins. The cam roller runs directly on a needle bearing so I was thinking something like case hardened 8620 for both the roller and pin would be OK? Cam it self I'm not sure of exact grade, i think is 41xx... and induction hardened. Geometry and cam is all sorted we have spent a great deal of time and development into getting it designed correctly.

My main concern is the tip roller which runs directly on the pin with no bearing, similar to all your typical v8 style roller rockers and I need to find the best material and hardening process for these two components. Iv heard dissimilar metals are usually better. This is only splash fed with engine oil, i have included into the design some little oil tracks in the sides of the body to promote oil down to the pin.

the cam roller is 26mm x 10mm wide with 2mm open cage needle running on a 10mm shaft (pin)
the tip roller is 13mm x9mm wide running directly on a 5mm pin

Thoughts and comments greatly appreciated.

RE: metal compatibility roller rocker conversion

Wouldn't you just use standard roller bearing components from the local bearing shop?

RE: metal compatibility roller rocker conversion

Design of bearings races is covered in some detail in FAG/Schaeffler Technologies publications. The needle bearing catalog was particularly helpful regarding critical details like hardness, case depth required for particular loading, geometry and surface finish.

ISKY is offering roller rockers with bushings for some extreme applications due to bushings' superior overload carrying capabilities.

RE: metal compatibility roller rocker conversion

(OP)
Yes, maybe i wasn't clear enough with my description, this follower has two rollers one is large runs against the cam in a constant spinning motion with a needle bearing inside this is no problem i have received plenty of help from bearing companies and we have a nice little open cage needle bearing in there. The problem I have is with the other roller on the tip which is much smaller and needs to run directly on a 5mm shaft pressed into the body of the follower. This tip roller is similar in design concept and application to any old school V8 roller rocker which has a small roller on the tip which rocks back and forth on the valve stem during its motion. Both the shaft and roller will need to be high strength hardened components and able to withstand a lot of impact load but will also need to be compatible to wearing against each other with only splash fed oil. I would like to get some ideas of steel grades and hardness i should be looking at.

RE: metal compatibility roller rocker conversion

Hi E21

INA catalog 307 is what I was referring to.
I do no know if there is an online equivalent, but suspect there is. This says something similar will be available November 2012
http://www.fag.com/content.fag.de/en/branches/indu...)

There is a section dedicated to the design of shafts that needle bearings will roll directly against

Materials for rolling raceways.
Light duty applications successfully run the needles on some pretty basic, soft steels.
But Since hard working ball/roller bearings (Harley and oher MC crankpins) need a case depth of 1.5 mm or so, I'd anticipate hardening 3 mm of the 5mm shaft - might as well consider it thru hardening
INA lists thru hardening steels - DIN 17230 eg 100Cr6 ( same as 52100 maybe)

Surface hardness 670 to 840 HV is required, with hardness >550HV at depth based on load and rolling element ( needle ) diameter.
Nitriding is generally too shallow to work. Chrome plate is out.

the geometry ( roundness, smoothness, cylindricity, clearance ) for use as a bearing are all specified.

What the shock loads are, and whether the shaft/race can "take it" is another story

RE: metal compatibility roller rocker conversion

(OP)
tmoose
thank you for the input, the roller I am most concerned with has no bearing it runs directly on the shaft and its the material and hardness for this roller follower and shaft Im looking for help with.

I have received help from SKF for the bigger roller and shaft which does have a needle bearing and we have gone with a case hardened steel for both so at this stage I have a starting point to try.

RE: metal compatibility roller rocker conversion

This may be a little unscientific for you - but I have made very useful little bearings (for an application similar to yours) by using a standard 5/16 inch hardened and ground dowel pin inside a standard 8mm needle roller inner race.

RE: metal compatibility roller rocker conversion

(OP)
Thats more like the thing i was thinking but maybe the other way round, use a single 5mmm needle roller for the shaft and make a hardened roller. Anyone have thoughts? Should the roller be case or through hardened?

RE: metal compatibility roller rocker conversion

"I've heard dissimilar metals are usually better."

Steel on steel is a bad start, hard or not.
Skimpy lubrication supply makes it worse.
Likelihood of starting from zero rpm makes it harder to initiate or maintain hydrodynamic lubrication, which makes it even worse.
Some plating or coatings might help. I believe Honda used to nitride their con rod pin ends when the attempted a steel-on-steel full float, and it was common to find the rod and pin galled to some degree.
Leaded bronzes are better at surviving marginal lubrication than the stronger bronzes.

RE: metal compatibility roller rocker conversion

Fascinating, Tm - - can you think of any standard applications for these two components - - presumably a leaded bronze bush and centerless ground hardened pin would be the better match - - I imagine there's a decent choice of, for instance, "needle" bearing rollers for pins, but what std applications would call for leaded bronze bushings, and who produces them?

Tekton

RE: metal compatibility roller rocker conversion

(OP)
I would go as far as to say every pushrod engine roller rocker in the world (usually V8) from probably hundreds of manufacturers use a steel on steel pin and roller for the valve stem roller so its a widely used and well proven concept but of course they wont share such details. Can the likes of 4140 be hardened to different levels? Is it best to have both surfaces hard as possible or would it be better to have say the pin a hard grade of tool steel or bearing steel and the roller made of something of lesser hardness??

RE: metal compatibility roller rocker conversion

I don't have the answers, but I'll surely be closely following this thread- since I'm also embarking on design/fabrication of a set of roller followers for a one-off DOHC inline four cylinder! I'll probably also go with a needle bearing for the cam roller and plain bearing for the tip roller. The pivot end will likely be a radiused cup sitting on a ball stud (threaded for lash adjustment). I'm leaning toward a crowned wheel at the valve tip to assure no parallelism conflicts between cam lobes and valve tips- what do you think?

RE: metal compatibility roller rocker conversion

(OP)
smile :).... pinto or L series?? be careful with the geometry or you end up with a big inverse on one side of the cam lobe which makes it difficult to design and grind, I also considered a crowned roller for alignment, but for now sticking with the standard notched lash cap, we are looking at producing these so stay in touch. If your engine is the ford then i think there is something already available, maybe from UK?

RE: metal compatibility roller rocker conversion

No, nothing available; converting a rare old M/T Pontiac hemi head from pushrod/rockers to DOHC.

RE: metal compatibility roller rocker conversion


e21jps,

If cost is no object, then consider cold-worked Haynes L25 (cobalt alloy). I have had good experience with this alloy (also called Haynes alloy L-605) in challenging boundary lubrication applications. Metal-to-metal galling resistance at elevated temperatures is very good.

Dick

RE: metal compatibility roller rocker conversion

Turbo, since commissioning a few dozen one off specials is prohibitively expensive, can you suggest any production applications where one might purchase L25 or L-605 pins and/or bushings which, if they cannot be directly substituted or incorporated in the experimental valve train, hopefully might be adapted with minimal effort?

Would you suggest both pin and bush utilise the same cobalt alloy, or should dissimilar materials be used - - if so in which positions?

I asked similar questions of Tmoose regarding his Nov 5th suggestion of using leaded bronze, presumably the bush, but he may not have an answer - - does anyone else have suggestions please?

Tekton

RE: metal compatibility roller rocker conversion

Straight Aluminum bearing bronzes are strong but gall without real good lubrication.

http://www.buntingbearings.com/index.html?gclid=CN...
http://www.buntingbearings.com/data.html

http://www.anchorbronze.com/c93200.htm
"C93200 is suitable for bearings, bushings having medium loads and speeds with adequate lubrication".
SAE 660 Bearing Bronze , High Leaded Tin Bronze , 83-7-7-3 , ASTM B 505 , ASTM B 271.

A little lead eases manufacturing. A little more buys better resistance to galling when lubrication is poor. "Too much" can cost too much strength.

RE: metal compatibility roller rocker conversion

Tekton,

My experience with using L-605 is both the pin and the bushing in a variable nozzle mechanism for a turbocharger. I believe the alloy was developed for similar pin and bushing applications in the variable exhasut nozzle mechanisms of fighter jet engines.

I also used this alloy to solve a valve to valve guide wear issue for a large engine (CAT 3600 series) exhaust gas bypass valve. I don't really know of any other commercial applications, or how the material may be purchased other than bar stock.

See link for info about New Hampshire bearings.

The big advantage of L-605 is the high temp dry anti-galling properties. It may not be the ideal cost material for your application, but it would very likely work from a technical stand-point.

Dick

http://www.nhbb.com/reference/rod-ends-bearings/be...

RE: metal compatibility roller rocker conversion

Turbo and Tmoose, thanks for your suggestions and links, which I shall investigate carefully

Our application differs from the OP's in that we intend swaging 5mm od hollow pins into either end of the rocker arms, one to support an approximately 15mm od roller acting on the camshaft lobe, the other an approximately 8mm od roller acting on the valve stem tip

My suspicions are that a C93200 high leaded tin bronze bushing and complementary pin would suit the valve stem tip roller assy, but may not the higher rpm camshaft lobe roller depending on Anchor Bronze & Metals Inc. definition of "medium loads and speeds"

While L605 may also be suitable, I expect its cost effectiveness will suffer due to the materials required to meet the extreme operating temps and minimum lubrication of its design brief

Tekton

RE: metal compatibility roller rocker conversion

e21jps,

Whit any type of hertzian contact, like that of your camshaft roller follower or rocker roller tip, you should always try to equalize the contact stresses in both parts. With the contact between the roller follower and cam lobe, the roller follower will typically have a smaller radius of curvature than the cam lobe, except for contact across the nose of the cam lobe, and will also be subject to a greater number of load cycles than the cam lobe due to its smaller circumference. To minimize friction losses at the roller follower, it is best to have rolling contact between the cam and roller, and to have sliding contact at the much smaller radius interface between the roller and rocker pin.

The same applies with the contact at the rocker roller tip and valve stem. The reversing rolling contact between the roller tip and valve stem, produces less friction loss than the sliding contact at the smaller radius contact between the tip roller ID and the rocker tip shaft.

RE: metal compatibility roller rocker conversion

e21- You knew it was just a matter of time, before I hijiacked your thread, right?!
I recently got far enough along with my OHC design to assign dimensions to my "fingers" and come up with ballpark worst-case tensile and shear stress requirements. It looks like I could get away with easy-machining 4130 (off-the-shelf wrought bar at about 30 -32 Rockwell-C). Comments?

RE: metal compatibility roller rocker conversion

(OP)
Hey all discussion is welcome, where i got to was considering 52100 bearing steel for both the rollers this is said to be great alloy with good durability and wear properties, i think its used with deep case hardening to about 60 Rockwell. For the tip roller pin something like 4340 through harden to around 43 Rockwell to maintain core strength, same material for the cam roller pin but since it has a needle bearing use a deep case harden up to maybe 50+ Rockwell

Anyone have thoughts on this combo??

RE: metal compatibility roller rocker conversion

If you want to take a page from the latest F1/INDY/NASCAR type valvetrain and engine tech, I would suggest either tool steel, or 52100 for both parts, and then have one of them DLC (Diamond Like Carbon) coated to provide a good bearing layer between them. Today's DLC coatings are both hard, and tough (interesting mix), and also provide their own lubrication. Most DLC's end up with some mix of sp3 bonded carbon (diamond), some sp2 bonded carbon, plus some hydrogen, interspersed in their outermost layer(s). The sp2 bonded carbon provides graphitic lubrication to the boundary when no oil film is present (i.e. startup), all but eliminating wear. I can personally recommend Industrial Hard Carbon, in Denver, NC. They market their coatings to racers and engine folks via a sister company called Extremion. Good stuff.

-Tony Staples
www.tscombustion.com

RE: metal compatibility roller rocker conversion

So- any comments on my proposed use of 4130 for the bodies of the followers? Any concern about the areas where the two roller axles will seat in them- maybe need local harderning there? [I'm leaning toward a snug fit of the axles in the bodies, with retention by E-clips in grooves.]

RE: metal compatibility roller rocker conversion

"52100 bearing steel ...... is said to be great alloy with good durability and wear properties ". I think 52100's claims to fame are hardenability, which brings raises UTS and fatigue strength, and availability with high cleanliness with thus reduced likelihood of impurities to serve as fatigue initiation sites. Related to Hertzian stress is "contact stress" that is the heart of many ball bearing life calculations. Hertzian stress near ball/roller/race contact can be WAY higher than plane bearing stress, so even tiny material imperfections in the wrong place are going to reduce the stress cycle counts before cracking.

Maybe the tribological nightmare of skimpily lubricated steel-on-steel has proven to survive just fine in this application, but substitution of "ceramic" balls, still running on 52100 races, immediately brings life improvements related to disagreements that go on at the secret ball/race interface. The weaker the ElastoHyroDynamic lubrication, the more impressive the resistance of the mixed material combo to wear and damage becomes.

RE: metal compatibility roller rocker conversion

I'm hoping to avoid needle bearings, which make an AWFUL MESS if breakage occurs in a race engine. I also hope to not "re-invent the wheel", so I was looking at Isky's description of their EZ-Roll roller lifters, which use micro-finish technology in place of needle bearings (forgive my over-simplification). Since they offer retrofit of EZ-Roll to earlier lifters, I fired off an email, asking if they might help me out- either sell me the EZ-Roll pieces for my use, or do the "fitting" of those pieces to the followers I'll fabricate. Here's hoping they respond...

RE: metal compatibility roller rocker conversion

(OP)
During my discussions with a metalurgest he indicated chromolly steels such as 4130 would be fine for the pin/shaft, I have gone for 8620 with a deep case harden for good core strength and hard surface for the needles. I have looked at the Isky EZ Roll, they have oil pressure fed through internal galleries to the pin so it operates just like a journal bearing which i think is essential to its success. It is possible to incorporate the same system into my rocker as i do have a pressure fed rocker shaft but it involves a lot of galleries and blind plug in the pin etc. much easier to just stick with well proven needles. I have seen a few articles about peoples adventures with an old overhead cam V8, ford i think? it had roller followers without a needle bearing and encountered countless failures between pins and rollers so a needle bearing really is the best solution for everything but the most extreme conditions. Some drag engines run over 750lb open spring pressure with 1.65:1 or greater rockers so thats 1,230lb up static on the lifter, not to mention the dynamic loads shifting lifters, pushrods and valves to 0.700" lift all at 8000rpm so its no wonder they start having problems! OHC applications typically have lower spring pressures, my application only has about 280lb static with a 1.4:1 rocker ratio 0.500" lift and no pushrods or lifters to move so im picking the needles will be happy all day.

RE: metal compatibility roller rocker conversion

Isky has not yet answered my email. When (if) they do, I'll question them about the need for pressure oil delivery to the wheel/axle. If necessary, I could provide that, since my design already includes pressurized oil to the follower/ball-stud juncture. It would just mean a couple of passages drilled into each follower body.

RE: metal compatibility roller rocker conversion

Oops... I forgot to respond to your comments:
Springs will be about 250 lb. seat and 575 lb. open (about .625" lift). Follower ratio will be within a whisker of 1:2. Maximum negative acceleration of lobe profiles will be limited to about 2.5 x 10^(-4) inches per cam degree squared. I'm building the engine (blown alky) to have good power up to at least 10,000 RPM.

RE: metal compatibility roller rocker conversion

Today's telephone conversation with Ron Iskenderian was in stark contrast to my being frustrated at lack of a response from my emails to Isky Cams. I gotta' tell ya'- Ron exemplifies good customer service. We talked for more than a half hour, during which he displayed considerable engineering expertise- and also a genuine interest in my project (telling him how his dad Ed helped me out thirty years ago with my original M/T hemi sort of "broke the ice"). He is quite willing to sell me the EZ-Roll pieces and to work with me.

Neither the EZ-Roll nor EZ-Max lifters have internal oiling- "splash" is fine for all but extremely severe applications (1,300 lb. springs, etc.), in which case "dedicated" oil supply to the axle is recommended (but merely "aimed" near the axle is sufficient).

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