How many people are building airplanes?

Paul Lamar

Hello Paul, I am slowly working on the rebuild of  Zenair CH250 and Bede BD4. Both were damaged in landing accidents. I bought the airframes without engines or instruments. G-RAYS is the Zenair.
Everything is a learning curve for me.

I have put both these aircraft in steel jigs .Just coming to grips with the best way to remove the pop rivets in the areas requiring repair is of interest to me right now. Some rivets seem much tougher than others like there is a variation in the type used especially in the BD4. I have been punching out the steel centre shaft first . Some don't want to budge and there is only so much force I can use. I have then drilled in with a 1/8 drill bit but some seem to slip from the centre especially when the core steel is still in it. This can easily lead to damage to the surrounding area which is fine when I can't reuse the skin anyway but I would like to be bang on so I don't cause damage when I come to peel open the wing skins for a good inspection inside on the Zenair . Once I have drilled in just below skin surface depth or sometimes all the way through I knock the top of the rivet off with a small chisel.


Any hints or advice would be appreciated.


Although I have collected a number of different automotive engines including the Subaru, Rover V8 and Corvair my gut feeling is the Mazda RX8 (of which I have got three) gives me the best solution. The Mazda has the best ability to produce a high power to weight ratio. However the Zenair at least has a recommended max firewall forward weight of 300lbs and I would really like to be well under this .
It's for this reason I am looking at ways to reduce the Mazda basic weight and find your discussion of alloy end plates most interesting. I am waiting on a chance to get together with a friend who is going to machine down a couple of end plates to see what I have to play with . I am thinking along the lines of milling the end plates down to about half an inch thick then making up a water jacket a bit like the  oil sump.


Water pump from a v6 ford is a self contained item so that can be run by belt and I am looking for a dry sump oil pump.


You were also talking at one time of electric points being run on the crank shaft. What I don't yet know is how many times the points on the Mazda need to fire per revolution of the crank. Could you help me on that one?


One other question I have is regarding superchargers or turbo chargers. Sometimes I read how an automotive turbo charger is not ideal in an aircraft as it runs at a high capacity for long periods. Is this truly a problem and if so what sort of turbocharger should I be looking for?

My work away from home as a live in carer (although it is only 15 weeks or so a year)  and the fact that I have to go from England to France as often as possible to maintain my home there means work on my planes is sporadic . I wish I had started on pursuing my true interest many,many years ago and I have a lot of catching up to do.


I would like to take this opportunity to once again thank you for allowing me access to your vast knowledge and experience by way of the internet.
Regards
Mark Dillner UK

Thanks Mark.

Q1 "You were also talking at one time of electric points being run on the crank shaft."

Each Wankel rotor fires once per revolution of the e-shaft so a very simple inductive
ignition is all you need.  In aircraft use there is no real need for ignition advance.
Set the advance to 22 degrees BTDC.

One set of points for each rotor. One cam for each rotor. The points are closed
for 90% of the time. When the points open the coil fires the plug.
Since the Mazda has two plugs per rotor wire two coils in parallel.

Now you need a second set of everything for the second rotor.
Mount the second cam 180 degrees away from the first cam.

That is all there is to it. A super simple ignition system two rotor ignition system.
Highly reliable. Check the wear on the points from time to time
and replace as necessary.

RX8 coils and a lot of others these days have solid state switches built in
so the points no longer carry a lot of current.


Q2 "automotive turbo charger is not ideal in an aircraft"

That is true.  Use as large a turbo as you can get  and use a blow off valve
on the intake manifold set to what ever boost or HP you want.

The reason for this is you don't need rapid spool up for the turbo charger
and a large turbine is more durable at the 1800 F exhaust temperatures
involved.

You can use a by pass hole in the exhaust manifold venting the exhaust system
to the atmosphere.

No real need for a waste gate. About a inch and
a quarter hole is about right. Make it larger for less boost.  I would say
at this point 80 inches of Mercury will give you about  650 HP at 8000 RPM
in a two rotor with a very effective intercooler. You control this with the blow off valve,

Keep the manifold air temperature below 150 degrees Fahrenheit.
You might need water injection for take off power if your intercooler
does not do the job..

More like 40 or 45 inches of mercury is about right for most experimental
aircraft. You will get something like 300 or 350 HP max take off power.


With Iannetti silicon nitride apex seals the life of the Mazda rotary is unlimited
in aircraft use.

Paul Lamar

The Rotary Engine free News Letter. Powered by Linux. If you want off
the list PLEASE let me know and I will remove  you.  ACRE NL web
site. http://www.rotaryeng.net You Tube http://tinyurl.com/beqqxas
Copyright 1998-2017 All world wide rights reserved.