Impulse couplings

Tom-D

Tom-D

Taxi to Parking
Joined
Feb 23, 2005
Messages
34,740
Display Name
Display name:
Tom-D
a few pictures
#1 is the spring housing it contains the spring during assembly
#2 is the bottom side of the spring holder
#3 is the base or carrier of the assembly
#4 shows the bottom side of the carrier holding the fly weights in the low RPM position
#5 same thing
#6 same thing
#7 broken spring and the reason to remove.
#8 complete assembly drive gear and all.
#9 shows the fly weights held in the run position.
 

Attachments

  • DSCN2449.JPG
    DSCN2449.JPG
    214.5 KB · Views: 23
  • DSCN2450.JPG
    DSCN2450.JPG
    216.5 KB · Views: 21
  • DSCN2444.JPG
    DSCN2444.JPG
    226.2 KB · Views: 25
  • DSCN2446.JPG
    DSCN2446.JPG
    215.8 KB · Views: 23
  • DSCN2443.JPG
    DSCN2443.JPG
    168.2 KB · Views: 26
  • DSCN2451.JPG
    DSCN2451.JPG
    220 KB · Views: 25
  • DSCN2456.JPG
    DSCN2456.JPG
    144.8 KB · Views: 30
  • DSCN2455.JPG
    DSCN2455.JPG
    218.3 KB · Views: 23
  • DSCN2448.JPG
    DSCN2448.JPG
    209 KB · Views: 29
Last edited:
Ruh-Roh. Someone busted a spring. ;)

How do ya think they accomplished that one, Tom?
 
(dammit. i thought this was going to be about one night stands)
 
That spring didn't just break, it disintegrated!
Ever hear of pieces escaping the housing?
 
Geico266 said:
I would say you got your money's worth. Aren't they suppose to be replaced at 500 hours? :confused:
Click to expand...
Not at all. It's a good idea to inspect mags and couplings that often but they generally last a lot longer than that (like 4 times longer) without failing.
 
gismo said:
Not at all. It's a good idea to inspect mags and couplings that often but they generally last a lot longer than that (like 4 times longer) without failing.
Click to expand...

On the 310, the mags were original with the engines - factory remans from Continental. At about 1800 hours one failed, at about 2000 hours two failed (within 10 minutes of eachother on run time), and so I opted to have the fourth one done before it followed. In all cases, the nylon gear inside the mag was what failed.

I've done 2 or 3 of the mags on the Aztec, which have failed pretty much at random over my 800 hours of flying it. However, I doubt that they were done with the engine overhauls.
 
If they fail around 1,000 to 2,000 hours why not just replace them at the 500 hour inspection? Cost?

I have not overhauled them, but I have taken them apart and installed them. Why not just over haul them at 1,000 hours? :confused:

Just asking, but it seems to me that waiting for them to break is not a good plan.
 
Geico266 said:
If they fail around 1,000 to 2,000 hours why not just replace them at the 500 hour inspection? Cost?

I have not overhauled them, but I have taken them apart and installed them. Why not just over haul them at 1,000 hours? :confused:

Just asking, but it seems to me that waiting for them to break is not a good plan.
Click to expand...

Agreed it's not the best plan. It's a bit easier to track when you've got an easy means of knowing the history, i.e. you bought them new or had them done yourself.

Many people do overhaul them at a certain interval. Cost of overhaul depends on how you have it done (i.e. by an A&P or get an exchange unit from someplace). I have my A&P do my rebuilds, and it's not that expensive.
 
We must remember a new impulse coupling does not come as part of the mag, it is often removed from the old mag, and transferred to the new one. We do not track time on these parts, gears or other accessories. The drive gear is a portion of the engine and gets inspected but maybe not replaced either.

Bottom line here? you really do not know how old the impulse coupling is, unless you have a log entry stating when it was installed new. For your own good when you have parts replaced get the s/n and p/n entered, because the mag this was on, was replaced last year. this is the exactly the same coupling used on the Bendix mags and has a 500 hour AD to check the wear limits on the fly weight pivot points.

This coupling was on a Slick mag but it would not pass the Bendix AD requirements. A new one is in shipment and will be replace.
 
Last edited:
Good info guys. Thanks.

I have Slicks and replaced them 300 hours ago. From what I have read and been told it is better just to replacement rather than rebuild them.
 
Geico266 said:
Good info guys. Thanks.

I have Slicks and replaced them 300 hours ago. From what I have read and been told it is better just to replacement rather than rebuild them.
Click to expand...

This also makes a difference. All 8 of my mags are Bendix, and that makes me happy. The Slicks seem to cause problems for everyone I know who has them.
 
Geico266 said:
Good info guys. Thanks.

I have Slicks and replaced them 300 hours ago. From what I have read and been told it is better just to replacement rather than rebuild them.
Click to expand...

did you get the new impulse couplings too?

It is what drives the mag, with out it, your brand new mag will not start the engine, and it could allow your brand new mag to run 25 degrees retarded.
 
Ted DuPuis said:
Agreed it's not the best plan. It's a bit easier to track when you've got an easy means of knowing the history, i.e. you bought them new or had them done yourself.

Many people do overhaul them at a certain interval. Cost of overhaul depends on how you have it done (i.e. by an A&P or get an exchange unit from someplace). I have my A&P do my rebuilds, and it's not that expensive.
Click to expand...

I hope your A&P has the proper equipment to do the overhaul, or he is logging it as a repair. very few A&Ps have the equipment to compLy with the manual.

It requires the mag be tested on the bench.
 
Tom-D said:
I hope your A&P has the proper equipment to do the overhaul, or he is logging it as a repair. very few A&Ps have the equipment to compLy with the manual.
Click to expand...

Yes they do. This is why, when I broke down in Texas, we had to get one overnighted from Aviall at a significant increase in cost.

It requires the mag be tested on the bench.
Click to expand...

Yep. Some don't like to do it for that reason. Fortunately, mine have the proper equipment.
 
Ted DuPuis said:
Yes they do. This is why, when I broke down in Texas, we had to get one overnighted from Aviall at a significant increase in cost.



Yep. Some don't like to do it for that reason. Fortunately, mine have the proper equipment.
Click to expand...

Most will simply rebuild the mag with the parts it needed and replace it, do a mag drop test and call it a repair.
 
Tom-D said:
Most will simply rebuild the mag with the parts it needed and replace it, do a mag drop test and call it a repair.
Click to expand...

How far do you have to drop it in feet? Onto concrete or asphalt? ;)

Kidding. Just kidding. ;)
 
Tom-D said:
did you get the new impulse couplings too?

It is what drives the mag, with out it, your brand new mag will not start the engine, and it could allow your brand new mag to run 25 degrees retarded.
Click to expand...

Yes, the impuse coupler was new except for the metal drive gear. I think. :confused:
 
Last edited:
An old drill Sergeant drummed it into me long ago - take care of your impulse coupling and it will take care of you...

denny-o
 
Dr. O said:
An old drill Sergeant drummed it into me long ago - take care of your impulse coupling and it will take care of you...

denny-o
Click to expand...

"This my weapon, this is my gun, one is for fighting, one is for fun. " ;)
 
Tom-D said:
We must remember a new impulse coupling does not come as part of the mag, it is often removed from the old mag, and transferred to the new one. We do not track time on these parts, gears or other accessories. The drive gear is a portion of the engine and gets inspected but maybe not replaced either.

Bottom line here? you really do not know how old the impulse coupling is, unless you have a log entry stating when it was installed new. For your own good when you have parts replaced get the s/n and p/n entered, because the mag this was on, was replaced last year. this is the exactly the same coupling used on the Bendix mags and has a 500 hour AD to check the wear limits on the fly weight pivot points.

This coupling was on a Slick mag but it would not pass the Bendix AD requirements. A new one is in shipment and will be replace.
Click to expand...

TOM, JOOC what kind of impulse mag comes new or rebuilt without the impulse? I've bought and sold thousands of impulse mags all with impulses.
Charlie Melot Zephyr Engines
 
Tom-D said:
Most will simply rebuild the mag with the parts it needed and replace it, do a mag drop test and call it a repair.
Click to expand...

Yeah, my A&Ps actually do the full rebuild with bench test, etc.
 
charlie said:
TOM, JOOC what kind of impulse mag comes new or rebuilt without the impulse? I've bought and sold thousands of impulse mags all with impulses.
Charlie Melot Zephyr Engines
Click to expand...

After checking AS&S this morning all new slicks come with one installed. older re-built don't.

Yes, you can buy TCM Bendix together from several places.

The good overhaul shops do that. :)

Check the price difference here for bendix rebuilt and new
http://www.aircraftspruce.com/catalog/stpages/bendixmagneto.php
 
Last edited:
Tom, superb pictures. Having a contrasting background really helped in viewing. And great picture captions. Thank you for posting those. Now I will read this thread.

What is the 'varnish' on those components? In pic 5 it looks greasy. Is that because you sprayed a cleaner on them?
 
Last edited:
Ted DuPuis said:
On the 310, the mags were original with the engines - factory remans from Continental. At about 1800 hours one failed, at about 2000 hours two failed (within 10 minutes of eachother on run time), and so I opted to have the fourth one done before it followed. In all cases, the nylon gear inside the mag was what failed.

I've done 2 or 3 of the mags on the Aztec, which have failed pretty much at random over my 800 hours of flying it. However, I doubt that they were done with the engine overhauls.
Click to expand...
It seems you are using "mag" and impulse coupling as interchanegeable terms.
 
Geico266 said:
Good info guys. Thanks.
Click to expand...
I 2nd that. This thread answers many questions I have had.


From what I have read and been told it is better just to replacement rather than rebuild them.
Click to expand...
Ah roo? Previously you said you had disassembled them but not O/H them? Why would you bother given your comment here? BTW: I have gotten the same advice from long time A&Ps (better to replace)
 
Richard said:
It seems you are using "mag" and impulse coupling as interchanegeable terms.
Click to expand...

Lance referred to it being important to inspect mags and impulse couplings periodically. While I won't disagree, my point was that, if you have a properly rebuilt one, it can last much, much longer without inspection.

If the engines had been changed at TBO (instead of going beyond as we do), the engines would've made it from install to TBO without touching a mag, other than to adjust the timing.
 
You must log in or register to reply here.
Back
Top