ghittner

The Machs' were cancelled due to porosity in the castings. If you look at them it was very typical to find porosity throughout the castings especially in the hub and blade root areas. Later in the life of the Mach prop program they experimented with one piece castings but never could overcome the porosity issues with throwing blades. Hence the cancellation of the Mach propellers. We have taken care of any porosity issues during the casting process by changing gate sizing and pouring rates. Pure Virgin stainless steel is a key as well!
Greg Hittner

bbladesprops

Greg,

Without condensation intended. Just the facts.

Mach props phased themselves out for various reasons, not just from porosity failures specific. Heck I have some with hundreds of hours on them and they are still intact in the shop. Other advancements and lack of marketing, and the costs of production with the ease of other options/Merc props played in as well. (by the way, blade root failures were mostly from the welding issues not porosity).

Failure can and will occur with any lost wax investment cast propellers put under the stresses they are put up against. This is because the best investment cast pouring’s in the world cannot alleviate porosity or cold rolls, etc. completely!. Changing the flow rates and the size of the gate opening can't remove ceramic dust and Mother Nature and Mondays and Fridays. Claiming to have taken care of any porosity is a bold statement.

Plant 98 at Mercury has more hours and experience than any other foundry in the world when it comes to this stuff. I spent many hours living this. Mercury's foundry researches and works with these issues with the help of many sources daily and has for decades. I’m not married to Mercury anymore but I do understand and respect their experience in this arena and can with much experience state they know more than most. The issues of blade failure will remain when we talk about investment /lost wax castings. Truth be told, each casting has a life of its own. No foundry can claim perfection. Not Plant 98 Mercury, not the ones “we” work with not even Hill's old foundry and your current foundry Greg .



Brett

bbladesprops

Allicat38,
I looked up the recipe on the Lab we did. Are there any issues with the props? What are your numbers as far as WOT rpm and speed?

Brett

ghittner

I think you meant "contention"? None taken Brett. As usual, no time for that. We as well have gone through porosity issues and it is an expensive endeavor to look at propellers being thrown into the scrap pile due to it. So, That being said if we have any issues with porosity, the props are trashed into the garbage and new ones cast in a different manner that alleviates the problem. So, on that note we have no further porosity issues that reach our customers and no blade failures due to it.
My Best Brett,
Greg Hittner

bbladesprops

No,
I said what meant. I meant I wasn't trying to be "condescending" to you (cut you down), your comment or story although I disagree with it. You can't completely alleviate casting flaws. Nobody can.

We do the same when we see porosity, destroy it or fix it if possible
The problem and reality is, not all porosity is visible on the surface. Much of porosity can be internal. You can't see it! We find it when we modify or Lab propellers while removing surface material and fix it at that point. The porosity within yours and other castings act as stress risers and over time the blades can crack from the inside out.

Are you actually saying you know there are no porous holes within your castings? You say if you see them you then pour in a different manner? Why don't you always pour in the manner that you determine prevents them. Also, it isn't just pouring that causes porosity.

I don't know how you expect to control porosity completely when you can't see blades and hubs internally. Improve the problem, maybe yes. Remove any and all issues, I don't think so. Again, claiming to know there is no porosity in your castings is a aggressive statement and I'd be careful with that one.

My best to you too,
Brett

ghittner

Wow Brett!
"No One claiming perfection here! What was stated was exactly was
"We have taken care of any porosity issues",
that's it, nothing more, nothing less! Let's not make it into a statement that was not made!
But thank you for the lesson in metallurgy. However, I think we have it down quite well.
My Best,
Greg Hittner

bbladesprops

Wow Greg,

We did not intend to ruffle your feathers.

We are simply supplying clear concise technical information on this forum as we have since its inception 6+ years ago.
Specifics is our business.

I'm not making this into anything other than what you wrote.

You stated you had taken care of any porosity issues. To me, that is claiming perfection.

I wish we could all claim that but I feel it imperative for the public to understand that is a impossible thing to claim. You can only get in trouble that way. Castings will fail due to imperfections. Especially propellers. These are not forgings.

I'm sure you have learned a ton in the last few months! We all keep learning as we go along and grow.
Your welcome on the lesson. LOL

Have a nice weekend,
Brett

Rookie

iTrader: (4)

I don't think they are in business anymore, but I have been running some Spinelli round ear 26's that I bought this winter. I think they came off a Cig 35 Cafe'. I think they are more of a 24P then 26P. I like how they run but wish they didn't pull so many RPM's.

They are the middle props. I just wish I could spin the top props cause I love the attitude of the boat with them.

ghittner

Ruffle? Not at all Brett! A little chiding and ribbing is good for the Psyche. Some benefit more than others from giving it and others from needing it. But as for myself, it's all water off a ducks back...
Great weekend to you too!
My Best,
Greg Hittner

bbladesprops

Greg,

I wasn't chiding or ribbing or making jokes. I was and am serious on all the points I have made.

From Gary G's. Mach propellers to the porosity issues. I am suggesting you are claiming ability you can not control or in the Mach situation, don't have the backround for.

Brett