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Mag drive gears and electronic ignitions

vic syracuse

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By now I've learned that when I find a problem on one airplane there's a pretty good chance that it exists on other airplanes. This one is very serious, and could potentially cause a catastrophic failure.

I was asked by a friend today to help him find the source of an oil leak on his recently completed RV-10. It looked to me like the gaskets on the magneto covers were leaking (he had dual Lightspeed electronic ignitions with the crank triggers). So I recommended he replace the gaskets, as they were overtightened.
When he removed the covers, both mag drive gears were lying in the holes, and luckily the rubber bumpers were still in them.

It turns out the engine was shipped with mags and they were removed. The aircraft was built at one of the known builder-assist centers.

Please, please, take the time to check yours if you don't know for sure that the drive gears were removed with the mags. This could easily cause a catastrophic failure within the engine.

Vic
 

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Please, please, take the time to check yours if you don't know for sure that the drive gears were removed with the mags.

And the bearings!

Coming up...the Discovery Channel's new reality show..."Looking Over Vic's Shoulder"

Join us every week when we watch famous airplane guy Vic Syracuse pull strange stuff out of small places.
Episode 1: Vic finds Jimmy Hoffa in a tailcone.
 
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Ok....I’m in the middle of removing my mags for a SDS CPI-2 install. Does anyone have any tips/tools to remove the bearings from the case? Gears and rubber drive pucks came out easy.
 
Ok....I’m in the middle of removing my mags for a SDS CPI-2 install. Does anyone have any tips/tools to remove the bearings from the case? Gears and rubber drive pucks came out easy.

Same way you get a pilot bearing out of the end of a crankshaft on a car: Pack the cavity behind the bearing with white grease, insert a drift of the same size as the drive gear pilot, smack it with a mallet. The hydraulic action will pop the bearing free.
 
good tip

Same way you get a pilot bearing out of the end of a crankshaft on a car: Pack the cavity behind the bearing with white grease, insert a drift of the same size as the drive gear pilot, smack it with a mallet. The hydraulic action will pop the bearing free.
I've never needed this tip so far, but really glad to know it! Very clever! I only hope I remember it when the time comes. :)
 
I haven't had an engine apart,

So please explain what's going.


The pictured gears go in the rear case. ??

Then the mags go into those gears. ??

Wouldn't they just idle with existing gears in the case?



thanks
 
I haven't had an engine apart,

So please explain what's going.


The pictured gears go in the rear case. ??

Then the mags go into those gears. ??

Wouldn't they just idle with existing gears in the case?



thanks

The mags keep them in place. Without the mag installed, there is no pressure on them to keep them pressed into the bearings.

Vic
 
I haven't had an engine apart,

So please explain what's going.


The pictured gears go in the rear case. ??

Then the mags go into those gears. ??

Wouldn't they just idle with existing gears in the case?



thanks

Only one end is supported by the bearing. The mag normally supports the other end. Minus the mag the gear can wobble around and eventually pop out along with the bearing.
 
Same way you get a pilot bearing out of the end of a crankshaft on a car: Pack the cavity behind the bearing with white grease, insert a drift of the same size as the drive gear pilot, smack it with a mallet. The hydraulic action will pop the bearing free.

Awesome! I’ll try this today. As you know, not much room to work with the engine installed in a Rocket.
 
I haven't had an engine apart,
So please explain what's going on.

Picture = 1000 words...

Folks often pull out the cushion coupler (orange below) and neglect to remove the bearings (pink below) from the case bosses. Sometimes they shake loose later and do a lot of damage.

What Vic found was coupler and bearings.
.
 

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Picture = 1000 words...

Folks often pull out the orange cushion coupler and neglect to remove the pink bearings from the case bosses. Sometimes they shake loose later and do a lot of damage.

What Vic found was coupler and bearings.
.

Does it mean the bearing is supposed to be pressed into the engine case and the gear belongs to the magneto? I am not quite sure what is wrong with the original picture

Thanks
 
Picture = 1000 words...

Folks often pull out the orange cushion coupler and neglect to remove the pink bearings from the case bosses. Sometimes they shake loose later and do a lot of damage.

What Vic found was coupler and bearings.
.

Does it mean the bearing is supposed to be pressed into the engine case and the gear belongs to the magneto? I am not quite sure what is wrong with the original picture

Thanks
 
Same way you get a pilot bearing out of the end of a crankshaft on a car: Pack the cavity behind the bearing with white grease, insert a drift of the same size as the drive gear pilot, smack it with a mallet. The hydraulic action will pop the bearing free.

Tried this method and neither bearing will budge. The grease just keeps coming out pass the bearing race. Tried using a thicker wheel bearing grease without success as well. Looks like my local harbor freight has a blind bearing puller set. Might try that next.
 
Wait a sec...

...what bearings?

When I pulled the mag's out of my IO-360-A1B6 I did not see a bearing race as shown in Dan's and Vic's attachments.

Different magneto drive on the IO-360 than the IO-540?

b
 

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Bearing Puller

My local Autozone lent me a pilot bearing puller ( with refundable deposit ) to get the bearing out.
 
Tried this method and neither bearing will budge. The grease just keeps coming out pass the bearing race. Tried using a thicker wheel bearing grease without success as well. Looks like my local harbor freight has a blind bearing puller set. Might try that next.

Well thats a good sign that your case is not all egged out from a prior wobbly bearing. The grease trick works great when the bearing is sealed AND you can get some good velocity on the mallet (like in a car). Open cage bearings and the tight confines of the Rocket engine compartment make that trick tougher but it usually works. Just dont damage the case with a puller!
 
...what bearings?

When I pulled the mag's out of my IO-360-A1B6 I did not see a bearing race as shown in Dan's and Vic's attachments.

Different magneto drive on the IO-360 than the IO-540?

b

You have a four (4) cylinder engine. The six (6) cylinder engine, mag, gear, and bearing deal with the six-cylinder engine. I have never seen this bearing, gear, mag setup on a four-cylinder engine yet in over 25-years of working on airplanes.
 
Vac pump too?

It occurs to me to ask: Does the vacuum pump on the Lyc 320 have the same deal? If I permanently pull the pump is there anything else in there that I need to remove before I cover the hole?

-Dave
 
...what bearings?

When I pulled the mag's out of my IO-360-A1B6 I did not see a bearing race as shown in Dan's and Vic's attachments.

Different magneto drive on the IO-360 than the IO-540?

b

Only the 6 cylinder engines have the potential problem. The 4 cylinder mags have a drive gear on them that mates to the accessory drive gear in the engine.

VIc
 
I took some pictures of mine today to help. Carol tells me not everyone understands drawings ( I know she doesn't).

So, the pics show where it is located, and then a pic inside the engine showing the hole where the bearing would be. There is also a pic showing what the bearing looks like.

Yours could be on either side, but mine is located on the left side of the engine, just above the fuel pump. It is standard practice to remove the impulse coupled mag when installing electronic ignition, and the impulse mag is usually on the left side. I have seen engines set up with dual implulse mags, so nothing is for certain.
 

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I took some pictures of mine today to help. Carol tells me not everyone understands drawings ( I know she doesn't).

So, the pics show where it is located, and then a pic inside the engine showing the hole where the bearing would be. There is also a pic showing what the bearing looks like.

Yours could be on either side, but mine is located on the left side of the engine, just above the fuel pump. It is standard practice to remove the impulse coupled mag when installing electronic ignition, and the impulse mag is usually on the left side. I have seen engines set up with dual implulse mags, so nothing is for certain.

Great pictures, Vic. And certainly adds clarification. Thanks for taking the time to take these photos and share the details of the problem.
 
Well thats a good sign that your case is not all egged out from a prior wobbly bearing. The grease trick works great when the bearing is sealed AND you can get some good velocity on the mallet (like in a car). Open cage bearings and the tight confines of the Rocket engine compartment make that trick tougher but it usually works. Just dont damage the case with a puller!

I went to my local AutoZone and checked out their pilot bearing puller. Unfortunately the smallest bearing ID it’s intended for was 5/8”. The ID of the mag bearing race is 1/2”. Ended up buying a complete set of blind bearing removal tools from Harbor Freight. The smallest tool did the trick. I wasn’t able to use the slide hammer included with the tool due to space but I was able to get enough of a grip on the bearing that they both came out with approx 1/2 hour work each.
 
It is standard practice to remove the impulse coupled mag when installing electronic ignition, and the impulse mag is usually on the left side. I have seen engines set up with dual implulse mags, so nothing is for certain.

Why standard practice to remove mag with impulse coupler?
 
Why standard practice to remove mag with impulse coupler?

Couple of reasons. From a practical standpoint, the impulse mag is most susceptible to maintenance issues due to the extra moving parts. There's also some noise out there that they are especially prone to failure in the 6 cylinders due to some harmonics.

The overriding reason would be that the electronic ignition usually retards the timing for starting so it negates the need for an impulse mag. The impulse mag provides a stronger, and retarded, spark during the starting process, but usually disengages around 500 RPM's. With electronic ignition, the spark is usually hotter, and you should find starting much easier.

The downside is that if the electronic ignition should fail, it could be hard to start your engine. I will tell you that I have done some testing with the EarthX battery in my 10, and it spins it fast enough that it will start on the mag alone (non-impulse).

If I were flying to isolated back-country places, I would probably leave the impulse mag installed.

Vic
 
Couple of reasons. From a practical standpoint, the impulse mag is most susceptible to maintenance issues due to the extra moving parts. There's also some noise out there that they are especially prone to failure in the 6 cylinders due to some harmonics.

The overriding reason would be that the electronic ignition usually retards the timing for starting so it negates the need for an impulse mag. The impulse mag provides a stronger, and retarded, spark during the starting process, but usually disengages around 500 RPM's. With electronic ignition, the spark is usually hotter, and you should find starting much easier.

The downside is that if the electronic ignition should fail, it could be hard to start your engine. I will tell you that I have done some testing with the EarthX battery in my 10, and it spins it fast enough that it will start on the mag alone (non-impulse).

If I were flying to isolated back-country places, I would probably leave the impulse mag installed.

Vic

Thanks.
I have a single SDS CPI-1 on my IO-360-B2B on the RH side. I had lots of hot start issues when I had two mags. I put the SDS system on primary for better starts. I know, not best reason, but it cost about the same as a Slickstart plus it had all the advantages of electronic ignition. I decided to leave the left impulse coupled mag on just for extra start insurance.
The mag is now approaching its 1000 hour inspection and Contemplating options.
 
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