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PostPosted: Tue Feb 07, 2006 4:48 pm
by flyalaz
Hello once again,

Now that the engine rebuild is finished, the next item on the list is to fit new spinners. With a new installation, it's relatively easy to just position the spinner and drill through into the backplate.
When installing a new spinner, unless you want to make the backplate look like Swiss cheese, it's going to take a little finess to line up and mate the holes.
I think I have a way to do everything in one shot, but I haven't started yet. In my case, the old spinners were cut for the bi-props, and are too large for the P-tip profile. What I did so far was to use masking tape to block out the cutout and make it smaller to match the P-tip. So far so good.
The next step I have in mind, is to use a spinner I made from ABS as a template. I slip the old one inside, mark the cutout locations, and at the same time backdrill the holes. This should position the new spinner properly, as well as maintain a proper gap.

Anybody else have another idea?

Blue skies,
Karl

PostPosted: Thu Feb 09, 2006 12:42 am
by art
Karl, where did you get new spinners? Thanks Art

PostPosted: Thu Feb 09, 2006 12:39 pm
by flyalaz
Hi Art,

I bought them from John Nagy either last year or two years ago, along with four wheel halves. I don't know if he has any more.
I also made a spinner mould and then thermo-moulded some ABS plastic over it. The process still needs fine tuning, and I still need to spin test them to make sure they don't fly apart, but so far, the ABS seems to be bulletproof. Right now, I need to get some more material and mould a few more.

Karl

PostPosted: Fri Feb 10, 2006 7:54 pm
by flyalaz
First spinner almost done.

Took a little finageling, but the cutout is the right size. I used the dummy spinner to give me the approximate height, then after locating some 1/8" plate on the front of the motor, used a small washer like a little wheel with a pencil through the hole to follow the contour of the prop and transfer the shape to the spinner to give me an exact match.

Hole drilling next.

K.

PostPosted: Sat Feb 11, 2006 7:31 pm
by Shannon
Karl what type of screws will you be using on the spinners ? Years back I quit using the original type self-tapping sheet metal screws in favor of threaded stainless machine screws. I also use a flat washer under each screw as well as loc-tite.

Shannon

PostPosted: Sat Feb 11, 2006 9:44 pm
by flyalaz
Hi Shannon,

I use some MS flush head screws that are gold plated! I redrilled and tapped the backplate to fit and carefully countersunk the spinner to fit the screws. There are no knife edge conditions in the spinner holes, which would lead to cracking, and I plan on doing the same with these new ones.
The screws have been installed with locktite of course. I have been flying with this installation for the last three years absolutly fault free.

Knifedge conditions were a BIG no-no when I was working on biz jets, and my rough drawing will show what I mean for anyone who isn't familiar with the term.

Cheers,

Karl

PostPosted: Sat Feb 11, 2006 10:46 pm
by Shannon
Sounds like what you have works fine. Reason I asked was several spinnner plates I've seen had cracks that were apparently caused by self-tapping screws. Evidently the self-tapping screws had expanded the metal causing cracks to form on the plate flange.

It's good practice to keep a check on the spinners, screws, and plates. You will quickly become a believer after one blows apart on you.

Shannon

PostPosted: Sun Feb 12, 2006 6:02 pm
by flyalaz
I've heard a lot of stories about the old stock plates, and I gave mine a thorough cleaning and inspection before mounting them. There were a lot of score marks left on them from the fabrication process, so I blended them all out then polished them.
I don't know what alloy they are, and I know some types will crack more readily along a score mark so I didn't take a chance. You are most likely right about how others have failed, those self-tapping screws basically forcing their way into the metal, and I hope I never have to witness flying shrapnel on mine!
Drilling and tapping is definitely the way to go, and a proper pre-flight inspection is just good practice.

Karl ;)

PostPosted: Sun Feb 12, 2006 9:47 pm
by Shannon
The first indication of spinner plate problems was posted in Tech Update 8 (Aug, '83). I'm not aware if new plates were ever developed and sent out ?

Shannon

PostPosted: Mon Feb 13, 2006 1:07 am
by flyalaz
Perhaps Mr. Kramer would have an answer to that?