DeTomaso Mailing List: March 2000, Message #67

 <<>

That is a limitation with sonic testers. In doing something similar with a 
sonic tester in the past where we were getting inaccurate readings we were 
able to over come it by calibrating the sonic tester with a known surface 
with about the same diameter. We were able to have good repeatability and 
reproducibility. Our accuracy was, if I remember correctly, in the area of 
+/- .00025.  We had a tolerance of +/- .001.

I again state I have never done a sonic test on an engine block cylinder but 
have used it on a number of aerospace parts.  The unit I am thinking of 
borrowing is a high end, high accuracy model. A lot more than $900.00 retail. 
It is actually a bit over kill for the application we are discussing but then 
if I can borrow it so it is free and because it is a high accuracy model it 
is actually a bit more forgiving in the application we are discussing. 

Upkeep on most sonic testers is almost nil. I will state for the record that 
they are not designed for a dirty environment. The surfaced to be tested will 
have to have the mating surface that the sensor goes on clean of grit, rust, 
scaling and so on. Nothing that a little simple green and fine sandpaper 
can't handle in the application we are discussing. The other surface being 
clean really doesn't matter.

The biggest problem with most sonic testers is the rechargeable battery 
packs. They have a tendency to go bad unless the unit is used fairly 
constantly.  The grease is an ongoing expense but it is relatively 
inexpensive. The one thing that I want to emphasize is that these units 
cannot be dropped or have fluid poured over them. They are not real rugged 
and getting them repaired is very costly. But short of dropping or immersing 
one they are fine. Treat them like a good pair of Mics and things will be 
Okie dokie. 

I will try to give it the old college try when I hook up with MD and then we 
will get back with everyone. I may also be able to arrange a demo of a couple 
different models using an engine block to see what model would best meet the 
needs of the group. 

I "may" be able to purchase or trade for the unit I sold. I had it laying 
around with a bunch of other metrology equipment and I sold it at a price 
where I literally gave it away. I know it isn't used a lot and that is very 
well cared for so I will follow up on that. If I can get it back maybe I can 
either sell it to the group at the price I get it for or if the price is 
right I can loan it to the group. A lot of people have taken time out to 
share their passion for Panteras with me and if I can get it back at a 
reasonable cost it will be a way of giving back.  

Kim