Hi there,

here are some pictures of my newly ball burnished cases. Pretty good result (maybe a little too shiny but it's OK), no material is removed and it has a shot peening effect on the cases.

Did you mask off the sealing surfaces?

Where did you have this done and how much?

enekoizagirre wrote:Pretty good result (maybe a little too shiny but it's OK...

Very Nice....now the fun part is keeping them that way

No masking needed, it was made here in Spain, www.baster.es (web is in spanish). Engine cases, gearbox cases, head and primary inner case for 100 euros.

Shiny, shiny!

I wonder if there's some where here in the U.K that does a similar process?

How come they missed between the fins?

Hegel wrote:I wonder if there's some where here in the U.K that does a similar process?

Probably hundreds, it's not really special and many machining companies offer this kind of finishing. The process is know as ball burnishing, trowalising (named after the company TROmmel-WALther), tribofinishing, vibratory finishing, tumble finishing, whatever ... and is an industry standard. As usual you can go over the top and apply a chemically enhanced version known as Isotropic SuperFinish (ISF). NASCAR does that on complete blocks, mainly to aid oil drainage in the V.

How come they missed between the fins?

It depends on the size of the grinding "stones".

However I consider this mod to cooling fins pretty useless, maybe even deadly for the engine due to the surface reduction and the aerodynamic influences (boundary layer etc.). It looks good but technically speaking it is a change for the worse in the case of the head. On the housings, hm, yes, okay ...



Tim

How is this different than shot peening or tumbling?

However I consider this mod to cooling fins pretty useless, maybe even deadly for the engine due to the surface reduction and the aerodynamic influences (boundary layer etc.). It looks good but technically speaking it is a change for the worse in the case of the head. On the housings, hm, yes, okay ...

surface reduction? I was told there was no dimension change, so why should any surface reduction happen?

Thanks Tim

I have to have a look around for when I put the 850 cases together

It depends on the size of the grinding "stones"

Ah, gotcha. Another media type first to clean between the fins then.



<edit> I wouldn't have thought there'd be much difference in head cooling (Not that I'm an expert, or anything), with this finish? Considering some folk spray the head black, reducing the turbulence across the fins, etc. I'm not trying to start a bun fight...Just like to know is all

, maybe even deadly for the engine due to the surface reduction and the aerodynamic influences (boundary layer etc.).

Tim

Aerodynamic influences/boundary layer? Do explain?

enekoizagirre wrote:surface reduction? I was told there was no dimension change, so why should any surface reduction happen?

Erm, that's a joke, right? Why do you think it is shiny by now?

What happens is that the peaks are either plastically deformed or removed - depending on the actual process in the tumbler - and of course this is a dimensional change, but we're talking about µm here. "No dimensional change" in this sense applies to engineering dimensions, tumbling doesn't remove enough material to alter usual tolerances so even after several hours of trowalising a part that fit the specs before will still fit them.

The thing is that heat transfer depends on the surface roughness and for the case of an air-cooled fin the bigger (aka more rough) the surface is this is usually better.


Tim

Skyguyz wrote:Aerodynamic influences/boundary layer? Do explain?

A rough surface will create a larger boundary layer than a smooth one - and heat transfer happens mainly in the boundary layer. In order to be able to work properly a cooling fin needs enough aera to transfer the heat and enough boundary layer volume to dump the heat into. Both is changed by polishing and IMHO the change is for the worse.


Tim