SkyTec Starter -- Working loose

RONSIM · #1 08-07-2016, 06:01 AM

Working with a friend on his -7A --- less than 250hrs total, and on his second Skytec starter. The first was replaced under warranty because of looseness between the starter motor and the gear drive. We checked his starter yesterday, during an oil change, and discovered the same loose condition. This starter had the same issue on last oil change and the (2) connecting bolts were tightened and safetied.

What we found, this time, after removing one of the bolts, is that the motor housing bolt holes are significantly larger than the bolt. There are only (2) small (3/16?) bolts holding the motor to the gear drive and the bolt we removed showed significant fretting/stretching/deformed. I believe that the torque is allowing the motor to shift due to the larger hole in the motor flange and wearing at the bolt.

This is the "NL" version of the starter. I was wondering if anyone else has seen this issue? We are placing a call to the Skytec folks on Monday to discuss the issue.

Ron

DanH · #2 08-07-2016, 06:31 AM

It's been reported here multiple times. I repaired an early NL with a badly fretted case and stripped threads, and flew it a while. Then I upgraded to a new one, which is slowly doing the same.

catmandu · #3 08-07-2016, 06:31 AM

Yes, on two separate aircraft. On the RV, most recent rebuild was installed six months ago (after a cracked bendix housing), and I was told there were "improvements made" for that very problem, but still check it very closely each oil change. Just over 100 hours since and no issues noted thus far.

Toobuilder · #4 08-07-2016, 07:36 AM

Same issue with my NL. I dont know why they don't put dowel pins in to lock it down. Great starter aside from this issue.

tim2542 · #5 08-07-2016, 08:28 AM

I've had 2 of the same issue in 300 hrs. so I'm on my 3rd one now. The screws are found loose with the locking tabs in place, so it seems obvious the threads are pulling or wearing.
SkyTec has stood behind them even replacing it after the original warrenty expired, but they claim this is unusual and I'm pretty sure they see it all the time.
When this one works loose again and I'm sure it will, I think I'll install some Keen-Serts or similar thread insert. My untrained opinion is fine threads in aluminum is generally not a good idea. The dowel pin idea is interesting also, I wonder if there is a good place for one. Perhaps the screw holes could be machined for a dowel sleeve after the thread insert is installed.
Tim Andres

skylor · #6 08-07-2016, 10:29 AM

Quote:

Originally Posted by Toobuilder

Same issue with my NL. I dont know why they don't put dowel pins in to lock it down.

Likely because the motor itself is a COTS unit from the automotive world that doesn't have features already in the frame to accept dowel pins.

Skylor

krw5927 · #7 08-07-2016, 05:42 PM

Any idea which COTS unit the NL starter uses? How do I find this same motor online or, better yet, at my local auto parts store?

skylor · #8 08-07-2016, 11:33 PM

Quote:

Originally Posted by krw5927

Any idea which COTS unit the NL starter uses? How do I find this same motor online or, better yet, at my local auto parts store?

I'm not sure specifically which model motor the NL starter uses. The Skytec lightweight starters use motors and solenoids common to later model Fords, such as the 2005 Crown Vic.

bret · #9 08-08-2016, 05:53 AM

What is the cause or common denominator in these failures, heavy prop, ign timing to high for start ? thanks for the heads up, guess ill add this to my inspections....

Toobuilder · #10 08-08-2016, 07:04 AM

Quote:

Originally Posted by bret

What is the cause or common denominator in these failures, heavy prop, ign timing to high for start ? thanks for the heads up, guess ill add this to my inspections....

In my case I'm a stock compression 260, ignition timed to 3 degrees after TDC, and a standard 2 blade Hartzell - pretty easy on a starter.