How can I tell for sure if I have impulse coupling on one or both Slick mags (model 6393 on left, 6350 on right)? There is no difference externally that I can see (both seem to sit on a thick aluminum color base between the mag body and the engine case. Related question is if I do have impulse coupling on both, how does the wiring of the start switch change?
Van's Air Force
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impulse coupling
- Thread starter bob888
- Start date
Slowly and carefully turn the prop by hand in the normal rotation direction. Stay out of the prop arc just in case it fires. As you come up on a compression peak, you will hear a distinct 'clunk' noise if you have an impulse coupling.
As previously stated, I believe you have a retard breaker (extra points open at TDC but no impulse mechanism). These are designed to work with a Slickstart unit.
As previously stated, I believe you have a retard breaker (extra points open at TDC but no impulse mechanism). These are designed to work with a Slickstart unit.
Mag Switch
If you have a mag switch with a start position and non impulse mag in right position the right mag terminal on the switch needs to be jumpered to the terminal immediately adjacent to the R terminal. This grounds the right mag when the switch is placed in the start position.
If you have a mag switch with a start position and non impulse mag in right position the right mag terminal on the switch needs to be jumpered to the terminal immediately adjacent to the R terminal. This grounds the right mag when the switch is placed in the start position.
az_gila
Well Known Member
Don't do a Tim Allen
As always, the manufacturer's literature is the best source.
http://www.qaa.com/resource-center/Resources/L-1318H Slick Application Guide.pdf
Magneto types (active and obsolete) are listed on the last few pages, with definitions on page 10.
6393 = RB = Retard Breaker
6350 = DD = Direct Drive
As always, the manufacturer's literature is the best source.
http://www.qaa.com/resource-center/Resources/L-1318H Slick Application Guide.pdf
Magneto types (active and obsolete) are listed on the last few pages, with definitions on page 10.
6393 = RB = Retard Breaker
6350 = DD = Direct Drive
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I have exactly this set-up and can confirm that you have a retard breaker on the left. You should be able to see an extra terminal for the Retard.
You will need a Slick Start:
https://www.championaerospacepubs.com/docs/F-1100-SL2-96G.pdf
Having said that, I believe you can use an old-fashioned vibrator, but why would you?
Set-up was easy with a timing box. You just set the advance timing and the retard timing is taken care of internally. I only have a few starts (cold and hot), but they have all been near instantaneous with no spluttering or hesitation - really sweet.
As far as I can tell, the only downside of not having an impulse breaker is that you can't hand-swing in the event of a flat battery. Call me unadventurous, but that's probably something I wouldn't want to do on an engine that size anyway!
You will need a Slick Start:
https://www.championaerospacepubs.com/docs/F-1100-SL2-96G.pdf
Having said that, I believe you can use an old-fashioned vibrator, but why would you?
Set-up was easy with a timing box. You just set the advance timing and the retard timing is taken care of internally. I only have a few starts (cold and hot), but they have all been near instantaneous with no spluttering or hesitation - really sweet.
As far as I can tell, the only downside of not having an impulse breaker is that you can't hand-swing in the event of a flat battery. Call me unadventurous, but that's probably something I wouldn't want to do on an engine that size anyway!
awmuhs
Well Known Member
retard breaker question
I have a Vans IO540 on my RV10. I have been flying it for about 18 months and have recently been having trouble starting it mainly when it is hot.
When i was building the plane I was not very knowledgeable about what a retard breaker (RB) mag is. In fact I thought I had an impulse coupling mag on the left side. I recently found out it isn't. It's a RB.
I have been learning more about the difference between mags recently but do not know how an RB mag that doesn't have the RB terminal connected to anything behaves.
I have been flying without a vibrator box or Slckstart on the left side. How does this affect my ability to start the airplane??
I have a Vans IO540 on my RV10. I have been flying it for about 18 months and have recently been having trouble starting it mainly when it is hot.
When i was building the plane I was not very knowledgeable about what a retard breaker (RB) mag is. In fact I thought I had an impulse coupling mag on the left side. I recently found out it isn't. It's a RB.
I have been learning more about the difference between mags recently but do not know how an RB mag that doesn't have the RB terminal connected to anything behaves.
I have been flying without a vibrator box or Slckstart on the left side. How does this affect my ability to start the airplane??
Mostly the engine will have to spin fast enough for the mag to generate enough voltage to jump the plug gap. The slickstart or impulse couplings boost the voltage at very low rpm. So if the day comes that your battery is weak so the starter turns the engine slowly; or the plug gaps open up, it may not start.
Make sure your ignition key is wired so you start only on the retard breaker.
Jesse
Well Known Member
That is exactly the way I have experienced it. I flew a plane that I thought had an impulse coupling and it only had the Retard breaker. It never failed to start cold. It only seemed to have a problem after refueling and trying to restart. I added a SlickStart and that solved the problem.
I'm sure there is a good reason why Van's only sells engines with the RB Mag, but doesn't include the necessary SlickStart box, but I can't imagine what it is.
I read a post here a couple of years ago regarding the same question. The response indicated that Lycoming stopped using impulse coupling mags on the 540 engines years ago due to harmonic resonance that causes impulse coupling failure. I have not personally confirmed this information, but it seems plausible. An impulse coupling pawl failure on a running engine will cause lots of damage and may ruin you're day.
Yeah that's a good question as well. They supply the rest of the ignition system, so why not the required starting booster? They want way too much for that box. Have you tried looking for a "non-aviation" version? I bet there were retard breaker magnetos and starting boosters installed on some sort of machinery in the past.
Evolution10
Active Member
I received my Lycoming Thunderbolt engine just over a year ago. It was spec'd with two impulse mags - no problem with the request.
Not quite. The retard mag, just as its name implies, retards the timing at very low rpm so that the points open and the spark fires (if enough voltage) close to top dead center. If you attempt to start on the mag without the RB it will attempt to fire 25 deg before TDC, and at low rpm there is the chance of a kick-back, where the engine suddenly stops and turns in reverse a bit, which tends to break starter gear teeth. So the RB is doing something for you now, but only half of what it should (without the slickstart you have low firing voltage).
I agree with other posts that the plans and/or order forms from Vans are not crystal clear. I didn't realize the stock engine did not have impulse couplings until I got it.
Auburntsts
Well Known Member
Last time I checked they had yet to ship a 6-cyl p-mag after years of effort. Has that changed?
Just install a slick start module as in the instructions and your 540 will start like it has an electronic ignition. Hot or cold. They can also be installed with an impulse mag, but there are separate instruction pages, so be sure an use the instructions appropriate for the 6393 retard breaker mag.
Happy starting
Auburntsts
Well Known Member
Are you serious?
I was just trying to be polite to the suggestion of buying a p-mag in lieu of a SlickStart.
Raymo
Well Known Member
Duh. Missed the RV-10 association.
Carl Froehlich
Well Known Member
For anything else I would have drop the wait a long time ago. But here I am, flying with 1930 era magnetos waiting for the note from Brad at eMag that my two ignitions are in the mail.
I wait for the simple reason of extensive positive experience with the four cylinder pMags, as well as extensive negative experience with another electronic ignition system.
With 310 hours with just the stock Van's IO-540 slick mags the engine start has never been an issue. I miss most the efficiency gain from an electronic ignition. The most irritating aspect with mags is cleaning the plugs.
Carl
awmuhs
Well Known Member
SlickStart
OK, I have a confession to make. so as not to complicate my story when I asked about the RB mag last night in post #8 I didn't say that I had already installed the Slickstart.
I was trying to confirm what I had pieced together by reading on VAF, talking to Champion tech support, and other research I had done to see if the path I chose was a good one.
I mentioned in my first post I had no problem starting for the first 180 hours then hard starts became the norm. The engine ran great with no change in mag drop after I started having the hard starting issue. I installed the Slickstart unit as per the instructions last week. Now starting Hot or cold means maybe one blade passing before it fires. We will see if it continues.
Did I miss somewhere in the Van's plans or engine instructions that it said or strongly suggested to install the Slcikstart during construction?
OK, I have a confession to make. so as not to complicate my story when I asked about the RB mag last night in post #8 I didn't say that I had already installed the Slickstart.
I was trying to confirm what I had pieced together by reading on VAF, talking to Champion tech support, and other research I had done to see if the path I chose was a good one.
I mentioned in my first post I had no problem starting for the first 180 hours then hard starts became the norm. The engine ran great with no change in mag drop after I started having the hard starting issue. I installed the Slickstart unit as per the instructions last week. Now starting Hot or cold means maybe one blade passing before it fires. We will see if it continues.
Did I miss somewhere in the Van's plans or engine instructions that it said or strongly suggested to install the Slcikstart during construction?
I missed it too. Only after I got the engine did I see that there were no impulse couplings. I don't recall exactly what Vans web site said then. Now, under "slick start", it says "recommended", which made me think it was not required. Now, on the engine order page, it says slickstart "required".
