View Single Post
  #15   Report Post  
Posted to rec.crafts.metalworking
Larry Jaques
 
Posts: n/a
Default Year 6 Ryobi weed trimmer report

On Sat, 20 May 2006 22:32:06 GMT, with neither quill nor qualm, Gunner
quickly quoth:

On Sat, 20 May 2006 14:32:45 -0700, Larry Jaques
wrote:

On Sat, 20 May 2006 17:02:33 GMT, with neither quill nor qualm, Gunner
quickly quoth:

If that link doesn't work then go to MTD's home page, click on
"parts and accessories", and then "launch illustrated search engine".

http://www.mtdproducts.com/webapp/wc...rate/index.jsp


Btw..they are made in Chandler/Mesa Arizona.

Want the number for the plant supervisor or Sr. Engineer, so you can
bitch about the early failure? G


Bolens, Yard Machine, Cub Cadet, Troy-Built, and McCulloch products
are all THAT good, eh?


No comment on that one?



Gunner, vendor to MTD


Can you tell us what you vend to them?


Sure. Most of the pistons used in their engines are made from
castings, on OmniTurn CNC lathes.

Rather fascinating problems at first. The only way to hold the
piston casting..was from the inside..so needed an expanding collet
formed to fit the inside of the piston. Only problem was..3 out of 6
pistons would move during the operation Sometimes much..sometimes only
a smidge.. It was discovered that they have 6 die cast moulds..and 3
of them were out of spec enough that the custom expander would not
hold them rigidly. So I developed a way to hold even the loose ones.
Cant tell you about that..but it works. I had to sign a NDS.


Yeah, and it's best not to say anything anyway. I was going to say it
probably had something to do with indexing on the piston wrist pin
holes, but those came later.


The pistons come in, are held in the collet, and spun. The top is
domed slightly, the sides are turned, and the ring grooves are cut.
Then a drill motor comes in..and the C axis spindle turns the piston
and drills the wrist pin hole on one side, then spins 180', drills the
other hole, then a reamer comes in and reams the two holes seperately.
Test is when a gage pin with .0001 clearance is dropped into one
hole..it has to fall all the way through.




Not easy to do if the piston moved on the collet even a **** hair.
And of course all the other dimensions have to be within a certain
tolernce..surprisingly close for something of this nature.
Perpendicularity, parallelism, roundness, etc etc


Yes, and all of those have to matter when these things have an
operating range of 1,000+ degrees or so. [Gawd, I've been out of the
business so long (20+ yrs) I've forgotten all the relevant data...]


Being aluminum..the piston cannot be held too loose by the internal
gripper, or it comes loose or moves, and cannot be expanded too much,
as the piston comes out 3 sided. A fine balance, complicated by the
die casting size issues. Took a while to quantify the problem and
then try various fixes.


Cool.


Needless to say..they make good parts now. And coolant temperatures
both winter and summer made a fair amount of difference also..it being
in Aridzona next to Phoenix


BTDT and was installing A/C units on extremely hot engines in new
trucks for a dealer one summer. Suckage Factor: 100% I moved back to
LoCal right after that.

--
Put some color in your cheeks: Garden Naked!
------
www.diversify.com Colorful Website Development