>>>> 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
Steve,
Thanks for your opinion. For some reason I thought running on the
trailing
plugs alone caused a major loss in power, and elevated exhaust
temperatures
due to incomplete combustion. Ie fuel burning in the exhaust or turbo
charger. I just assumed that we were then dealing with a critical
situation.
If that is not the case then I completely agree with you. It
complicates
the
issue. I still want two ignition systems and one of them will be a
mag.
About the C-145. That must be the tail dragger father of my plane.
Doug Fir
C-150
N6686T
Doug,
About the C-145. That must be the tail dragger father of my plane.
Yep. It's a '48 C-170.
Paul and Crew - Has anyone seen results of a dyno pull w/o the leading
plug firing?
Steve Webre
Broussard, LA
I don't know. Perhaps Dave Lemon or Jim Mederer have tried it.
I'll ask Dave when he gets back.
Paul Lamar ...No rotor no motor.
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