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$630 starter shim, gotta be kidding!

KazooRV-9A

Well Known Member
Patron
A couple of weeks ago, I decided to test the Sky-Tek light weight starter that I mounted on the O-320 on my RV-9A project. This was just a cranking test, and luckily NOT a first engine start.
At the end of a few seconds of cranking, the starter pinion was stuck on the flywheel... I could get it to let go, but it definitely did not release on its own.
So I called Sky-Tek and the support guy told me (as I suspected) that the starter would need to be shimmed away from its engine mount pad, and he sent me a Textron Lycoming Service Instruction No. 1447B. He also cryptically alluded to being able to make my own shim.
In that Service instruction, there are some dimensions for clearances to the flywheel, and a reference to shim P/N LW-16152. So of course I googled the shim P/N, and luckily I was sitting down, because at Sky Geek the price was $631.40, with a 49-52 Business day lead time!
Affordable to maybe Jeff Bezos, Elon Musk, Bill Gates, Mark Zuckerberg, or Warren Buffett!
So firstly, I had not seen anyone post to watch for this possible interference with a Sky-Tek starter, so here's my story/warning for future reference. And just a shot, does anyone happen to for some reason have one of these shims, as I have access to a waterjet machine and could make some. And I'd be curious as to the thickness of the shim as a starting point. And/or I would like to hear of anyone else that has had to shim their starters, for the exact process they did. Otherwise I am sure I can fabricate a shim, and save the remaining balance of the $631.40, for something else on the project!
AC.
 
It would be helpful to know the thickness required. You could use anything from aluminum sheet, to stainless steel tape if it needed to be thin. If they aren't cheap to buy, I'd just make one and move on.
 
Would think you could go to a Goldsmith & get one made cheaper!

Price to cut 1, or a few shims ranging from .005 to .020 can't cost but a tiny fraction of that Unobtanium plated Lycoming piece!
 
Sky geek is always incredibly expensive. I don't know how they're still in business.

Like others have said, I'd recommend building your own. No need to spend all that money for a piece of drilled sheet metal and an 8130 for an RV.
 
Everyone has about the same price.

If it is just backlash being zero, a few gear calculations could yield the necessary center spread vs backlash. Easy to make a shim, but i might start with a thin AN washer and measure backlash delta as a starting point. Then it easy to make a shim from aluminum the desired thickness. I am guessing .015" so you could start with .016" sheet from the scrap bin. No paint.

Correction. Assuming 12 DP, 149 teeth, and 9 teeth, and 14.5 deg pressure angle. Backlash = 1.933x desired backlash. or ~ .020. Since the pinion got stuck, then it may need more, so start with .025" shim and measure backlash targeting 0.010". Adjust according to the formula.
 
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Stuck Starter Pinion Gear

I’ve had the same problem on a couple of occasions. I’ve used the shim once with good results on the other occasion it didn’t solve the problem but another starter and ring gear combination did. I still have the shim and it mic’s at .012” thick. I’ll send you a picture of the shim.
Duff
 
If you can make an electronic drawing with correct dimensions, any machine shop with a CNC mill should be able to crank out 10 for $200.
 
I’d draw it in cad, print it out on my printer, then confirm the dimensions and shape. Once I knew I had a good drawing, I’d shim with washers to confirm thickness as the other poster suggested, then upload to sendcutsend.com. A few days later I’d have what I need: perfect laser cut part.
 
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Don’t use gold

Would think you could go to a Goldsmith & get one made cheaper!

Ralph,

I think with the heat of the case, vibration and pre-load on the bolts that gold may be too soft and squish over time and lose the alignment.
 
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Starter Shim

Hey Andy,
I sent you the shim I had. Good luck on getting some duplicates made. Would appreciate a note when you get it.
Duff
 
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