Wisdom of Using a Mooney Engine

[RV7ator]

I'm liking the responses. Thanks. As to the counterweights, tracking the suffix back through the Lyc pedigree, half-way back to the basic A1A there's mention of particular weights at particular stations, and the prop plate bushings are keyed differently. So this baby is tuned to a particular Hartzell (part of the deal).

And I'm reading that even with the dual Bendix, this engine fits a the Dyna 1 mount Van's sells for A1As. Da, Comrades?

I know of the crank-triggered EIs, thank you, so I can build my way out of magneto dependent tech.

John Siebold

[RV8RIVETER]

I bought my engine off of a Mooney, -A3B6D many years ago, did the teardown and assembly ourselves after having all parts certified overhauled. It has been a great engine and experience. Have flown 4+ years on the dual mag without issue, it's reliability is no different than the other mags. The only AD is about not re-using star washers to prevent housing from rotational slipping.

That said, I am looking to upgrade to megajolt Ford EDIS ignition if I can engineer a crank pickup to mount to mag hole.

Wade

[Jim Ball]

Originally Posted by RV7ator

I'm considering adopting a kit with a IO-360-A3B6D, which is an angle valve engine with the dual Bendix mag and counter-weighted crank. What has the brain trust to say about installing this in a -7? My first concern is changing out the accessory case to separate mags so I can install P-mags. How much surgery and expense goes into doing this. Any issues with c-weighted cranks? I vaguely recall some problems, maybe ADs, no so long ago with them, though being a parallel valve guy, didn't pay much attention. Any other issues?

John Siebold

The conversion from dual magneto to two single magneto is not as simple as changing the accessory housing. The crankcase idler gear shaft locations have to be changed, a different crankshaft gear installed which would include specialized machining of the crank to change the gear bolt size from 1/2" to 5/16" and dowel relocation. It's quite an extensive conversion, we used to do the work at ECi. I don't know what shops can handle it these days.
It would be better to go with a Lightspeed ignition system that is not gear driven. It would be much less expensive.

[scsmith]

Originally Posted by Jim Ball

The conversion from dual magneto to two single magneto is not as simple as changing the accessory housing. The crankcase idler gear shaft locations have to be changed, a different crankshaft gear installed which would include specialized machining of the crank to change the gear bolt size from 1/2" to 5/16" and dowel relocation. It's quite an extensive conversion, we used to do the work at ECi. I don't know what shops can handle it these days.
It would be better to go with a Lightspeed ignition system that is not gear driven. It would be much less expensive.

Thanks for adding the helpful details. This reinforces what hgerhardt said, but with more info as to why.

[lr172]

Originally Posted by RV8RIVETER

I bought my engine off of a Mooney, -A3B6D many years ago, did the teardown and assembly ourselves after having all parts certified overhauled. It has been a great engine and experience. Have flown 4+ years on the dual mag without issue, it's reliability is no different than the other mags. The only AD is about not re-using star washers to prevent housing from rotational slipping.

That said, I am looking to upgrade to megajolt Ford EDIS ignition if I can engineer a crank pickup to mount to mag hole.

Wade

When I added a megasquirt ignition on my 6, I made a custom pickup for the mag hole, using a standard lycoming gear. I made two of them, but only used one with no plans to add the second one. I made it so it could support either magnets or a small 32-1 toothed wheel. I used magnets for the megasquirt installation, but the EDIS will need a VR pickup and 32-1 toothed wheel.

I am afraid to use it on the 540 I am building, due to the reported vibration issues in the accy case. I will be doing a flywheel based pickup.

PM me if interested, as I would like to sell the extra.

Larry

[scsmith]

Originally Posted by DanH

Hmmm. Hey boss, did they say exactly that?

Pendulum absorbers damp a vibratory order. Generally, in pendulum design the roller and bushing diameters set the order. A particular propeller may be happier if some specific order is damped, but if the installed pendulum is tuned to a different order, it's hard to imagine how it could hurt. They are passive devices. Put another way, they damp, not add. If the crank doesn't oscillate at the tuned order, the pendulum does nothing.

Parts book says the A3B6D uses the same pendulums, rollers, and bushings as the rest of the IO-360 A and B models with pendulums. The different crank part numbers are due to differences in prop flange drive bushings.

If I wanted to run that engine and did not want a dual mag, I'd just install crank triggered ignitions...SDS, EFII, Lightspeed, or EDIS.

I would think that prop mass/inertia, and prop clock position, would be an important part of the tuned system to get the benefit the counterweights were designed to provide. So sticking with the same prop is probably best. Taking a whole package off of one airframe and mounting to another is probably fine -- unlikely that the airframe participates much in the modes we are talking about.

[lr172]

Originally Posted by scsmith

I would think that prop mass/inertia, and prop clock position, would be an important part of the tuned system to get the benefit the counterweights were designed to provide. So sticking with the same prop is probably best. Taking a whole package off of one airframe and mounting to another is probably fine -- unlikely that the airframe participates much in the modes we are talking about.

THis is interesting. I have done some research and found that many have re-clocked their Hartzell on the 540 at a different position from stock (clocking moved lug over) and have seen reduced vibration. Curious to learn your thoughts on that, as the 540 has counter weights as well that are configured for the hartzel compact hub.

[RV8RIVETER]

Thank you Larry. PM sent.

[Ironflight]

Originally Posted by DanH

Hmmm. Hey boss, did they say exactly that?

Pendulum absorbers damp a vibratory order. Generally, in pendulum design the roller and bushing diameters set the order. A particular propeller may be happier if some specific order is damped, but if the installed pendulum is tuned to a different order, it's hard to imagine how it could hurt. They are passive devices. Put another way, they damp, not add. If the crank doesn't oscillate at the tuned order, the pendulum does nothing.

Parts book says the A3B6D uses the same pendulums, rollers, and bushings as the rest of the IO-360 A and B models with pendulums. The different crank part numbers are due to differences in prop flange drive bushings.

If I wanted to run that engine and did not want a dual mag, I'd just install crank triggered ignitions...SDS, EFII, Lightspeed, or EDIS.

Right or wrong, that?s what the old guy said....caveat that it is the factory advice filtered by a guy who was teaching his last class after 40 years or something like that....

[DanH]

Originally Posted by lr172

... but the EDIS will need a VR pickup and 32-1 toothed wheel.

36 less one. Just polishing the pins....

Originally Posted by scsmith

I would think that prop mass/inertia, and prop clock position, would be an important part of the tuned system to get the benefit the counterweights were designed to provide. So sticking with the same prop is probably best. Taking a whole package off of one airframe and mounting to another is probably fine -- unlikely that the airframe participates much in the modes we are talking about.

Good discussion of prop clocking here some years ago, with input from Les Dowd. I put an example of blade ringing in post 39.

Propeller mass moment of inertia is usually far greater than the inertia of the crank assembly, so the prop can generally be viewed as an anchor against which the crank oscillates torsionally.

Also a post or two relating to airframe participation (see #33). An A3B6D/McCauley combination may be fine on a Mooney 201, but it's pretty awful on an RV. Been there, done that with an 8A.

http://www.vansairforce.com/communit...ad.php?t=14161