Titanium Rocker Shafts

[chris_seven]

To match with the Ti Studs we are starting to make we have finally bitten the bullet and started to manufacture a trial batch of Titanium Rocker Shafts.

The idea is that the lower modulus will cause the fit between the bore and the shaft end to be improved.

We have also decided to change the design of the grooves to accommodate an O ring rather than a square section seal as it will be easier to install.

The seal does not need to have a significant pressure capability so we have decided to use a 'dynamic' fit which should make installation more straightforward.

The 'fit' of rocker shafts has also concerned me for a while and I think many of the problems that occur are due to poor installation/removal of the shafts.

The h5 fit specified means that some shafts will be an extremely tight fit and it is possible that the factory could have used an informal 'selective assembly' procedure which would mean that new engines would generally be oil tight and undamaged.

Later in the life of the engine it would be more difficult to follow this procedure and some shafts may have been 'helped' into bores causing scoring.

I could be wrong but as we have more flexibility we have eased the fit to a g5 which will make assembly a little easier.

We hope the O ring will have sufficient capability to seal slightly scored bores.



We have selected a 6AL4V Titanium alloy which will be solution treated and precipitation hardened to around 175 ksi.

After grinding the shafts will be isotropically superfinished and then PVD coated with a Titanium Carbo Nitride Layer which has a surface hardness of about 3500HV (harder than DLC).

They will be very lightly polished after coating to further reduce friction.

We should have them on test early in 2014.

[mike curnow]

and this is to improve what?

[Kris Clewell]

and this is to improve what?

thats what I was going to ask. As a non moving part of the valve train, what are we doing here? just longevity?

[Fishcop]

I'd say it's to eliminate the leaking that occurs in older engines that have been pulled down more than once. Very hard to find a cam tower that hasn't had some scoring or damage from the fitting and removal of rocker shafts, over time they weep (even using the RSR seals). Replacing the old rocker shafts with an improved unit will be cheaper and easier than machine work to the cam tower and the inevitable problems of then getting a factory rocker shaft to fit and seal.

[chris_seven]

The idea is that the lower modulus will cause the fit between the bore and the shaft end to be improved.

There seems to be an increasing issue with shafts both leaking and walking out of engines.

The RSR Seals are a pain to fit and costly and the practice of trying to refurbish shafts by polishing just makes the fit worse.

There are some aftermarket solutions which replace the nut and bush used in the standard rocker shaft but I worry about this approach as the nuts used don't have a feature allowing them to be gripped which could mean they would be very difficult to remove.

I thought a solution that used standard hardware with a relatively low cost O Ring (Viton) may be attractive for old engines that had leaks.

It is almost impossible to refurbish old cam towers that are scored as you would also need to obtain oversized shafts and rocker arms with oversized bushes.

I hope these parts will eliminate this requirement and allow many of the scored cam carriers to be used successfully at reasonable cost and without complex engineering.

[Frank Beck]

Chris,

I wish you the best of luck with your products and so far am impressed with them. Except perhaps this one?

We do a LOT of old motors and the Wrightwood Racing seals work magnificently. Whether it's a street tractor motor or a 9k race motor, it's been our experience that the seals are not difficult to install and we have no problem with the shafts walking. Maybe you're using some of the lesser quality seals that are out there? Not hard to identify as they have no beveled edge and "cut" as you're installing them.

Tell me you're going to build a screw style Ti rocker that weighs 30% of a stock cast version, AND is designed to break relatively easy and I will pre order 20 sets.

[chris_seven]

Frank,

We see quite a few problems and I don't think it is going to get better.

The seals I have used till now have been supplied by Porsche. I looked at making bevelled edge seals but then decided to look at shafts as tooling costs were high and shipping costs for seal sets is more than the seals and doesn't seem worthwhile.

We have also seen some new rocker shafts that don't like to fit as they are at the top end of the size range.

The cost of making these shafts isn't too bad and if we are correct they will work and be easy to use.

I am not sure that I would make Ti Rocker arms as I don't have a good enough fatigue test facility but a simple shaft which is subject to low stresses is much more straightforward.

I think the price of a set of shafts will be similar to the price of the typical aftermarket locks that are available and much more straightforward.

If you are going to replace shafts the increase in cost is relatively small but I would agree that if you don't need shafts there are alternatives.

We are only making 6 sets as a trial so it won't be too costly an experiment. If they work we could use them all in-house in around 12 months.

I tend to agree that they are a bit experimental - but nothing ventured - nothing gained.

[Flieger]

Even a tiny bit of mass taken off the back of a 911 helps.