metal compatibility roller rocker conversion

[e21jps]

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.

 

[BigClive]

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

 

[Tmoose]

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.

 

[e21jps]

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.

 

[Tmoose]

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/e...ler_bearing.jsp?addedItem=PubLanguage(386195)

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

 

[e21jps]

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.

 

[BigClive]

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.

 

[e21jps]

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?

 

[Tmoose]

"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.

 

[Tekton]

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

 

[e21jps]

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??

 

[pontiacjack]

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?

 

[e21jps]

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?

 

[pontiacjack]

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

 

[turbomotor]

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

 

[Tekton]

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

 

[Tmoose]

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

http://www.buntingbearings.com/index.html?gclid=CNXWuKD20LMCFQZnOgod2TYA4A

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.

 

[turbomotor]

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/bearing-materials.aspx

 

[Tekton]

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

 

[Tmoose]

The Bunting bronze data link does not leave PV ratings of 93200 to the imagination.

http://www.buntingbearings.com/data.html