>> Paul, everyone.
>>
>>
>> In the interest of redundancy and safety I have been doing drawings
on
>> the
>> possibility of installing two leading plugs. Each would be fired
by
>> independent ignition systems. One a mag, the other a C.D. system.
>>
>> The leading plugs are the critical ones. Therefore I've look at two
plugs
>> angled in towards the middle which would result in two angled
>> intersecting
>> holes at the housing middle. Another way to do it would be to
plug
the
>> center hole and drill two new holes side by side.
>>
>> The first way would bring the fire into the middle but would create
a
>> chamber of about 1 cc cubed.
>>
>> The second case is obviously easier and like Paul suggested in an
earlier
>> post there is enough metal (almost 10mm in the inner housing to tap
and
>> thread a aluminum insert into it. The outer housing has enough
thickness
>> so
>> it could be stepped for an 0-ring seal or epoxied in.
>>
>> On the straight through approach the pitch of the holes would be
30mm
on
>> center or in other words 15mm offset. I am concerned if one
ignition
>> system
>> goes down would the remaining firing plug cause rotor imbalance
because
>> the
>> center of combustion is offset? Lycs and Continentals obviously
can
run
>> on
>> one ignition system and the distance between plugs is two to three
times
>> greater.
>>
>> Any comments would be appreciated as I can't find any material to
suggest
>> Mazda or anyone has ever tried this.
>>
>> Doug Fir
>>
>> I can see how this would add to the electrical reliability
>> of the ignition system. Unfortunately this is the most critical
>> area of the Wankel rotor housing as far as cooling is concerned.
>> Mazda is still doing research and changing this area as far as
>> the exact configuration of the water jacket is concerned.
>>
>> The early one rotor NSU Wankel Spyder got it wrong and
>> the rotor housing would crack straight through the spark
>> plug hole.
>>
>> When the rotor housing melts after you run it at high power
>> without coolant for awhile this is where it starts melting.
>>
>> Therefore it is highly risky to modify this area.
>> On the other hand it might help if a little R&D was done by
>> installing some thermocouples.
>>
>> BTW This is another reason you don't want to nickel and
>> dime the cooling system plumbing by using automotive hose
>> and hose clamps. Use only silicone rubber hose and constant
>> torque hose clamps or better yet -20 or -24 AN lines.
>>
>> Baker Precision down the street from Mazdatrix now has
>> forty five degree and ninety degree bends in the one inch
>> size silicone hose. They don't have constant torque hose
>> clamps yet but you can buy those in every truck stop
>> in the country. When I need AN fittings and hose Baker is
>> where I go.
>>
>> http://www.bakerprecision.com/splsilicone.htm
>>
>> I know you know all this Doug but it is worth repeating
>> for the new subscribers from time to time.
>>
>> Paul Lamar ...No rotor no motor.
>>
>
> Paul,
>
> Yes you brought up one of the points I was concerned with and that
is
> adding
> more restriction to the water passage in the most critical cooling
area.
I
> hadn't heard about the physical weakness of the housing in that area
but
> it
> does makes sense not to add addition stress risers. Come to think of
it
> roughness in castings often causes stress risers. That might be why
the
> cooling passages are so smooth. That and low water flow resistance
of
> course.
>
> Still for the rotary powered airplanes, failure of the either of the
> leading
> plugs is probably the main issue I'm not completely happy with. JB
Weld
> is
> the other but I am coming around on that one. Only 499 more
freeze/boil
> cycles to go:)
>
> If the plug is considered a super reliable item then dual ignitions
> systems
> could be pulsed out of phase through the same plug. IE: one of the
FET
> gate
> closes as the other one opens. Granted this would cause even more
wear
and
> elevated temperatures on the plug but at least it is something that
could
> be
> easily dyno tested.
>
> I did a little research on plug design today and suspect size has
been
> influenced to some extent by ham handed mechanics like Paul has
mentioned
> earlier.
>
> Food for thought is shown below:
>
> \\ Since the inside of a spark plug is a relatively slim 3mm dia.
rod
> with
> a iridium tip welded on, couldn't two of these rods enter at an
angle
and
> then travel straight down a 14mm diameter thin wall threaded
stainless
> tube
> and be epoxy potted in place? Of course the epoxy would have to be
a
high
> temp non conductive type. The face that is next to the inner
housing
> would
> have a stainless cap with two holes surrounding the 0.4mm diameter
> iridium
> electrodes. The iridium 0.4 mm tip, now currently used in plugs,
would
> fire to the stainless 2mm dia. hole surrounding it. The hole shape
could
> be
> enhanced if need be. Ie star shape. The electrodes would still be
timed
to
> fire in sequence.
>
> The loss of compression would be minuscule and might even be better
than
> the
> standard recessed plugs. The idea might work for the trailing plug
as
> well
> eliminating fussing with the far trailing plug. This would give us
four
> spark events as the rotor travels by.
>
> The inner electrodes could be supplied by Nippon Densu down the road
a
bit
> from here, and the stainless and epoxy cases made up without too
much
> trouble. Sure they would be more expensive than regular plugs but
with
a
> little development effort we may be able to come up with a way to
tap
the
> epoxy and screw the electrodes in as well so the cases could be
reusable.
Doug,
Use JB Weld, you could tap that.
John
I don't think JB Weld is high temp enough for this application.
--
Paul Lamar ...No rotor no motor.
Doug,
I appreciate your reasoning for looking into dual leading plugs, but my
gut feeling as an engineer/pilot is that you would be in the area of
diminishing returns.
As I understand it, if the lead plug goes dead for whatever reason, we
still should have 90+% power.
Now I know we can work up a scenario where that 10% might make the
difference between an inconvenience and tragedy, but unless I missed
something in the discussions, I really don't believe an additional
ignition system actually gets us much besides a "warm fuzzy",
complication and expense.
Currently, I feel quite comfortable flying w/ two independent "antique"
ignition systems (mags) sparking an "antique" engine (C-145).
A rotary w/ dual, well designed solid state ignitions system should be a
vast improvement by itself.
Just an opinion.....
Smooth air,
Steve Webre
Broussard, LA.
N3812V
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