Magnetos for A65

[colinc]

Hi,

I am looking for some impulse mags to replace the current Bendix SF mags on the A65. The old mags have been overhauled and are fine, the engine starts first pull when cold, but despite our best efforts hot starting is impossible.

Anything considered, cores needing overhaul is not a problem. I do already have the gears (one impulse one not) for slick mags.

This is a big problem for me as after a break of many years I am planning finishing my ppl on the Tcraft and landing away and stopping the engine isn't really an option with the current mags.

regards

Colin

[magman]

Re: Magnetos for A65

I would disagree with the statement; "overhauled & are fine".

The coils or capacitors are most likely not functioning when HOT.

The old insulation tends to be ineffective & the mag does not fire.

If you can get the current mags redone with NEW parts (NOT NOS) may be an option.

TAP lists several mag shops that might be able to to provide some S4 mags.

There are pros & cons on the Bendix vs Slick mags.

Slick is cheaper for new outright.

However; LONG term ( over 500 hrs) I think Bendix (TCM) is better due to pricing structure on parts.

BOTH are good mags.

[N96337]

Re: Magnetos for A65

I agree with magman... bad insulation... get some NEW stuff in there. We had that problem with Single Otter mags as well. Just one more reason I keep my Eisemans!

[colinc]

Re: Magnetos for A65

I think that you are probably right. The points are NOS and the condensors are new but the original coils were checked as ok, however I can see that the insulation could break down as the temp rises and cause the hot starting problem.

Are new coils obtainable?

[Robert Lees]

Re: Magnetos for A65

Colin.

Be careful you are not being led up the garden path by the above responses. Your old Bendix mags are fine...they just don't have impulse units.

Are you cautious about having to hand-swing non-impulse mags when the engine is warm? With the throttle one inch open?

Bring the plane down to Leicester one weekend and I'll teach you and your Instructor how to start an A65.

Rob

[jim cooper]

Re: Magnetos for A65

Mechanic I am not, but the old timers seem to swear by Bendix and Eisman mags. They told me its usually the coil that goes (about 150-200 bucks) but that both are VERY good mags. (I have Eismans AND THEY ARE VERY GOOD, although quite old!) One good A-I told me recently the new slicks are in his words, ("way overpriced and crap!") unquote. JC

[colinc]

Re: Magnetos for A65

Thanks Rob,

I'll do that because in all other respects it's perfect. I also need to return your seat sling!

regards,

Colin

[colinc]

Re: Magnetos for A65

Jim,

my first thought was that we had tested the coils and they were fine, but they were cold so the idea has credibility. If I can find new coils at reasonable cost then it would be worth installing them.

However, I do think that in the long term I would like to fit impulse mags.

regards

Colin

[flyguy]

Re: Magnetos for A65

Colin,
I had a single Eisemann coil with a hot failure some time back.

The first thing that comes to mind is that it would be very unusual if coils on both mags started to experience heat failures at the same time.

The exception might be if you had one that was not running "right" for some time (which you would notice) and then the other one went bad. My experience is that a bad hot coil would let you know WHILE the engine is running, hot, before shutting down. Are you seeing that?

Have you proved, in some way, that there is not a spark being generated by either coil when hot? That is, make a spark gap on one plug and have someone turn over engine while you watch for spark, best in low light conditions.

Hope these suggestions help, I have some other suspicions, but I think these are where to start,

Darryl

[ajfriz]

Re: Magnetos for A65

I will trade you your bendix mags for my case mags that have impulse couplings I know there will be a lot of people that will disagree with this, but I would suggest keeping your bendix mags and stay away from Slicks...

[magman]

Re: Magnetos for A65

I agree with Flyguy on checking for spark - CAREFULLY.

ALL mags generate heat as part of their "Electromagnetic Induction" process.

Many old coils use varnished wire as insulation.

Age, time & heat take a toll & short out a part of the winding.


You may not notice the problem because the mag is turning RAPIDLY with the engine running.

Much SLOWER while hand propping with no impulse.

Spark voltage depends on cutting the magnetic lines of flux RAPIDLY.

Some folks swear that parking into the wind, & opening the cowling will help.

[astjp2]

Re: Magnetos for A65

I had the bendix, overhauled by Savage, went to slicks for the impulse. For a purist the bendix are fine. I did a bunch of back country flying and when you dont have a tiedown, the impulse were the only way to go. I could start my bendix on the first or second pull hot or cold but the reduced effort on the slicks made it worth every penny!!!!!! Tim