R

RFazio

Well Known Member
Sly-Tec Starter Questions

I've got a sky-tec starter on my RV-6 with a Lycoming O-360. I have 230 hours on the plane and started with a new engine. Two times recently it back fired and caused the engine to turn over backwards and spin the starter in reverse. I think I may have let go of the starter switch and it fired at that point and caused it to reverse. I checked my ingition switch to make sure it is starting with only the left mag energized and it is. Then recently I also noticed that after starting it sounded like the starter bendix was still in for a moment or two. So I pulled the starter to check it out. I figured maybe the bendix needed lube. It was perfectly clean and worked very smoothly. I lubed it up anyway and clamped it in a vise. I hooked up jumper cables and spun it up. The bendix comes out instantly when applying power but stays in when I pull off the cable until it slows down. It is as though the motor is running as a generator and powering it enough to hold the bendix in. Is this normal? Also why do I have a starter solenoid on the firewall and a second one on the starter? The one on the starter is jumped out to energize when the firewall one is on. Couldn't I just use the one on the starter and eliminate the firewall solenoid? It would seem that would eliminate the solenoid staying in problem, I think?
 
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You need to keep the one on the firewall, the one on the starter draws 30amps for a moment as it engages and this draw will kill the key switch, that?s why you have a starter switch on the firewall, don?t remove it.

As for the starter staying engaged for a second, I don?t know. Is it a Skytech? Or Flytech? I don?t recognize Flytech but that does not mean much:)
 
Another reason to use a separate solenoid at the firewall is, with the other configuration, you would have a very large wire running to the front of the engine that is HOT all the time.
 
Sky-Tec not Flytech

It's a Sky-tec, I thought I had something wrong? I have a large wire running up to the starter anyway. It would not be any larger for the starter if I used the starter solenoid. I do agree with Russ though, 30 amps would kill the starter switch.
 
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RFazio said:
It's a Sky-tec, I thought I had something wrong? I have a large wire running up to the starter anyway. It would not be any larger for the starter if I used the starter solenoid. I do agree with Russ though, 30 amps would kill the starter switch.
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But that wire is not HOT all the time like it would be if you used that solenoid exclusively.
 
RFazio said:
Then recently I also noticed that after starting it sounded like the starter bendix was still in for a moment or two. So I pulled the starter to check it out. I figured maybe the bendix needed lube. It was perfectly clean and worked very smoothly. I lubed it up anyway and clamped it in a vise. I hooked up jumper cables and spun it up. The bendix comes out instantly when applying power but stays in when I pull off the cable until it slows down. It is as though the motor is running as a generator and powering it enough to hold the bendix in. Is this normal?
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What you describe is referred to as "starter run-on" and it is definitely not desirable. I dont have the answer at my finger tips, but I do remember extensive discussions on this subject in Bob Nuckolls' Aeroelectric List forum, so you may want to do an archives search there and you can followup with him with additional questions as needed. I do remember that while starter run-on is real, the notion of the starter motor acting as a generator, while sounding plausible, is a myth.

erich
 
Thanks for the suggestion. I did read through the Bob Nuckolls' Aeroelectric List and did find reference to the starter run-on for permanent magnet motors. He also posts the fix for the problem, a second small contactor breaking the connection to the starter's solenoid. I don't know if it is necessary but if I keep having the problem I may try his fix. At least I know I'm not crazy, and it appears to be normal. Thanks again.
 
erich weaver said:
I do remember that while starter run-on is real, the notion of the starter motor acting as a generator, while sounding plausible, is a myth.

erich
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You might want to do a little reading on motors&generators before you declare
them myths. It's a wire moving in a iron core field ,they are one and the same.
 
I wired my -6 up with a starter solenoid per the Aeroelectric book. Years later when I replaced the starter cable to put in a NL starter I removed the solenoid because honestly, I think its stupid to have a 2nd solenoid. If the starter cable is properly supported the chances of it failing and shorting on something are next to zero. Besides that one can still shut the master off. The starter worked much better with the 2nd one removed since just a few milliohms in resistance at 350A creates a considerable voltage drop.
 
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