Adjustable Forged Rockers

[chris_seven]

Have just finished the 3-D Model of the adjustable forged rockers used in 65-67.

We have added a machining allowance and will be sinking the forging die in the next week to ten days.

First forgings for machining trials will be ready by the end of March.

[afterburn 549]

May I speak for the stupid one here like me ..me
Why? is there a shortage?
thanx

[chris_seven]

They stopped making the forged rocker in 1967 and replaced it with a cast part and I think 8000rpm + race engines need a forged part.

The 'Solid' forged rocker used in the RSR has been re-manufactured but at vast cost and has been specifically outlawed by the FIA in Period F Appendix K Race cars. they also need 'Motorsport' rocker shafts and a complete installation is about $7500 with lash caps.

There is a billet machined rocker available but again FIA scrutineers are not fond of this part (my local FIA man has said they are unacceptable) and they cost about $360 each. Our target price is much lower than this .

We are producing them specifically for early SWB race engines as the original parts are quite rare and generally badly worn.

[afterburn 549]

Thanx!

[Henry Schmidt]

Seems like a great idea. If you need a testing partner, give me a call.
We are in the process of putting together a system of rebuilding the stock cast rocker to better than new and yet I would really like to see what your final product looks like.
Cheers

[hcoles]

The pad surface location seems a bit under constrained. Is the radius dimension missing or is the surface located relative to that dimension going to the tip?

[chris_seven]

Henry, that would be helpful.

We are in the process of producing a fixture to allow us to fatigue test rockers using an electromagnetic resonance test machine (Amlser Vibrophore) which will allow us to compare the basic fatigue life of a standard cast part with a new forging.

We will use this type of machine as they work at reasonably high frequency so we can do the testing in reasonable time scales.

This test method will only look at bending fatigue, it won't look at wear of either bushes or rubbing faces and it would be good to have help with this part of the process.

I am sure that the fatigue performance of standard rockers can be improved by careful shot peening and wear resistance dealt with by suitable heat treatment or surface treatment but the fundamental Fracture Toughness of the cast part will always dominate its fatigue life and it will be impossible to break up the cast structure by any heat treatment as only mechanical hot working can achieve this type of result.

Out target is to produce a high quality forged part with good surface treatment and hence wear at a sensible price which should make them affordable for use in competition motors.

The material selection we are using is a base material of 4340 steel heat treated to a 'T' Tensile condition.

We will then machine and isotropic super finish before applying a Balinite DCL Star Coating

(Oerlikon Balzers - BALINIT® DLC STAR)

The bore will then be honed and we will insert a GBB DP lead free bush.

We initially thought to hard chrome as the original rockers but the cost difference between hard chrome and grinding is only about $10,00 per rocker.

[hcoles]

The pad surface location seems a bit under constrained. Is the radius dimension missing or is the surface located relative to that dimension going to the tip?

[chris_seven]

Originally Posted by hcoles

The pad surface location seems a bit under constrained. Is the radius dimension missing or is the surface located relative to that dimension going to the tip?

The pad surface radius dimension is missing from this drawing but is present on the model that will be used for the manufacture of the tooling.

I am sure that the pad surface is OK as we have modelled this from scanning a good condition rocker and have added machining allowances in the relevant places and just tidied up some of the surfaces which on the rockers we used for modelling showed the signs of worn tooling.

The fundamental size and shape are as per the original part. We have not tried to redesign the rocker only to reproduce the original.

WE also have the completed drawingof the finished part.

We could put the data into an FEA programme but I am not sure what we would really learn as we don't want to change the shape.

The FIA scrutineer that I had discussions with tells me that the part should have the apperance of a standard part. I believe I can then 'get away' with the DLC treatment but if not we can get Poeton to Hard Chrome and grind.

Hard Chrome plating (chroming) by Poeton – Apticote 100

[hcoles]

Originally Posted by chris_seven

The pad surface radius dimension is missing from this drawing but is present on the model that will be used for the manufacture of the tooling.

I am sure that the pad surface is OK as we have modelled this from scanning a good condition rocker and have added machining allowances in the relevant places and just tidied up some of the surfaces which on the rockers we used for modelling showed the signs of worn tooling.

The fundamental size and shape are as per the original part. We have not tried to redesign the rocker only to reproduce the original.

WE also have the completed drawingof the finished part.

We could put the data into an FEA programme but I am not sure what we would really learn as we don't want to change the shape.

The FIA scrutineer that I had discussions with tells me that the part should have the apperance of a standard part. I believe I can then 'get away' with the DLC treatment but if not we can get Poeton to Hard Chrome and grind.

Hard Chrome plating (chroming) by Poeton – Apticote 100

Thanks for the reply. No intent to imply you are changing the pad surface shape or location. On another thread the subject came up regarding "regrinding" the surface and how that might change the lift as a function of cam angle, and would change the lift if the "regrinding" was not setup correctly matching the radius or otherwise optimizing to a best match of lift after the "regrinding". My thought was that small changes (sloppy or incorrect setup) in the radius or location could make a significant change in the lift as a function of cam angle. In your drawing the key feature is verticalness (sic) of the adjustment screw hole, I'm not objecting to that, it just seems it could be problematic to use considering it is not a forged easy to bank to feature but is a post machined feature. Seems like a cart and horse situation. How will you register the part to make that important used later hole? How does/did the factory do it?

[chris_seven]

I do understand the issue and I agree that this does need careful set up.

The forgings are being machined by a company in the UK that manufactures cams and they have taken measurements from heads and cam carriers to ensure that everything is in the correct place.

Detailed metrology of this type is outside my skill set so I am leaving this to the experts that do it every day. They will also be supplying us with cams so we should be able to offer a complete package.

Once we are sure that we have the rocker correctly set up we plan to make a simple jig so we can measure all of the clearances of every rocker and be sure that we don't have variability in rocker ratio and hence lift.

I am sure there is plenty of scope to make a 'cock-up' but we are trying hard to get it right first time.

[hcoles]

Originally Posted by chris_seven

I do understand the issue and I agree that this does need careful set up.

The forgings are being machined by a company in the UK that manufactures cams and they have taken measurements from heads and cam carriers to ensure that everything is in the correct place.

Detailed metrology of this type is outside my skill set so I am leaving this to the experts that do it every day. They will also be supplying us with cams so we should be able to offer a complete package.

Once we are sure that we have the rocker correctly set up we plan to make a simple jig so we can measure all of the clearances of every rocker and be sure that we don't have variability in rocker ratio and hence lift.

I am sure there is plenty of scope to make a 'cock-up' but we are trying hard to get it right first time.

Good answer. The inspection, machining or metrology drawings or reports would be interesting and possibly helpful to all the others that get the pads reground or to inspect second hand or original parts. I'm assuming all the stock rockers are intended to be the same but probably not, so this may in fact not be of much help to us out here with cast rockers from a wide range of years. Maybe your machining company will setup a "golden" cam and fixture, at least check that lift as a function of angle is within some boundary. Possibly a few original new rockers can be found to use as the "golden" lift path. I tend to worry about things that may not matter, so no intent to cause you a problem. In my job, this is what I do - attempt to find faults in various types of measurements and conclusions. I'll take my meds now. ;-)

[chris_seven]

I completely agree about worrying about every issue, it is the only way to obtain good results.

I spent my former life developing fatigue test rigs and then gas turbine engine and component test systems for both mechanical integrity and aerothermal performance and this led to helicopter geaarbox testing and all sorts of other high speed rotating machinery.

I have always found that Murphy's law is consistent and repeatable.

The more any new design is picked to pieces the better and I appreciate your comments.

Many Turboshaft engine dynos around the world are not only calibrated but periodically tested with a 'golden' engine so I think a good test fixture whoch we can measure and use to check all rockers is the best way forward.

[hcoles]

Originally Posted by chris_seven

I completely agree about worrying about every issue, it is the only way to obtain good results.

I spent my former life developing fatigue test rigs and then gas turbine engine and component test systems for both mechanical integrity and aerothermal performance and this led to helicopter geaarbox testing and all sorts of other high speed rotating machinery.

I have always found that Murphy's law is consistent and repeatable.

The more any new design is picked to pieces the better and I appreciate your comments.

Many Turboshaft engine dynos around the world are not only calibrated but periodically tested with a 'golden' engine so I think a good test fixture whoch we can measure and use to check all rockers is the best way forward.

Agreed, get 10 good engineers to pick apart your design and you will end up with a better design in most cases. Of course there are many examples where an excellent design resulted from one person in a short period of time. In any case, remember you will also need a "golden" elephant foot that is registered from the top surface and not the bottom and a way to register for the "golden" rocker shaft. At some point you can get a few checked by a coordinate measurement service, those should be handy in the UK, the software is pretty good on these now.

[Walt Fricke]

Chris

Are you also making the lash caps in various dimensions?

Is the MOI (or even just the weight) of these less than that of the cast rockers with their adjusters and lock nut? Do you happen to know by how much? I realize this was not your goal - authentic reproduction was.

I have had good luck with cast rockers and shifting at 8,200 rpm, but less inertia in the valve train is always a good thing.

[chris_seven]

Originally Posted by Walt Fricke

Chris

Are you also making the lash caps in various dimensions?

Is the MOI (or even just the weight) of these less than that of the cast rockers with their adjusters and lock nut? Do you happen to know by how much? I realize this was not your goal - authentic reproduction was.

I have had good luck with cast rockers and shifting at 8,200 rpm, but less inertia in the valve train is always a good thing.

We make lash caps for Coventry Climax and Lotus Twin Cam engines but not for the 911 as yet.

The reasoning behind making the forged adjustable rocker has been that we haven't had great success with cast rockers and 906 cams. Early forged rockers are selling in Europe for around $120-150 each and still need to be refurbished. They are also quite difficult to find.

If we are successful and manage to sell some of the forged adjustable rockers we will re-invest the tooling money and make the solid rockers and lash caps.

I think we would still fit a bush - unlike the RSR part as this would avoid the need to use the Motorsport Rocker shaft.

I haven't calculated the MOI difference between the cast and forged rocker but the weight difference is around 10%. Total weight difference is approximately 10 gms.

As a new Genuine Porsche rocker arm in Europe is around $120 with Sales Tax and shot peening adds another $30.00 (by the time the bore and threaded areas are blanked off) the small premium to have a forged part with good surface treatment seemed a reasonable decision.

We are forging 20 engine sets of these rockers and have 10 sets already allocated.

[AlfonsoR]

Very interesting project! A couple of questions..

What material are you thinking of using?

What is the target price for a set?

[chris_seven]

Originally Posted by AlfonsoR

Very interesting project! A couple of questions..

What material are you thinking of using?

What is the target price for a set?

Originally Posted by chris_seven

The material selection we are using is a base material of 4340 steel heat treated to a 'T' Tensile condition.

We will then machine and isotropic super finish before applying a Balinite DCL Star Coating

(Oerlikon Balzers - BALINIT® DLC STAR)

Alfonso - material and surface treatment as above. We will fit a GBB Lead free bush after DLC treatment and honing of the bore.

Target selling price is $175.00 each as the tooling cost is several thousand dollars with all the reverse engineering/scanning costs.

[AlfonsoR]

Originally Posted by chris_seven

Alfonso - material and surface treatment as above. We will fit a GBB Lead free bush after DLC treatment and honing of the bore.

Target selling price is $175.00 each as the tooling cost is several thousand dollars with all the reverse engineering/scanning costs.

Chris,

Thanks and sorry I missed that. I scanned thru the thread while at work so I must have been feeling a little guilty.

[chris_seven]

First batch of samples for machining trials are due at the end of this week.

Measuring jigs are finished and I will take photographs as soon as possible.