Heating problems

I have been running up the engine. So far I have 45 minutes on it. A number of problems have reared their head. The wiring has to be re done. I need to eliminate the quick disconnect plug. The tach pick up wire needs to be rerouted away from all of the other leads. The tach is not reading properly. The pick up is inducing a signal into the adjacent wires, which in turn are inducing a second signal into the tach pick up lead. The CHT lead broke because there was not enough strain relief, the EGT never worked. I need to disconnect the instrument panel from the canopy, yet it still needs to pivot away when the canopy is raised. I'm going to make a secondary pivot for the Instrument panel. That should solve the problem and allow hard wiring direct to the panel and eliminate the disconnect plug. The second problem which is much more serious is excessive hear build up on the reduction drive mount. That in turn is conducting the heat to the back of the spinner backing plate. The spinner backing plate is room temp cured graphite epoxy laminate. As soon as it gets above 175 degrees, the plate gets soft and the spinner starts to wobble. I plan on solving this by three methods, I will post cure the spinner plate in the oven at 300 degrees. Hopefully that will raise the T/G (Temperature of gel) to near the hub temp. Next I will place a fiberfrax or Mica insulator between the hub and the spinner backing plate. Third I am going to drill some vent holes in the backing plate and in the inlet baffle. to direct some of the input cooling air toward the mount. There is no secondary air flowing in the rest of the cowl, this is causing high internal temps. Hopefully the internal duct I am ding to add will help this. It will take very little flow to solve this problem. Because of this, I decided to tear down the engine compartment and install a .012 aluminum heat shield over the top of the firewall fiberfrax insulation.
 

Existing baffle wearing thru the FiberFrax

 The actual engine head temp is running cool, it seems to peak around 425 degrees. The spec allow the head to see 500 degrees. Because of this, I should be able to redirect some cooling air toward the reduction drive mount.

New Aluminum heat shield

I am in the process of finishing the engine re installation. I should have this finished tomorrow.

Finally I have a third problem that is also equally serious. My Fiberglass fuel tank is starting to deteriorate. I attribute this to the ethanol that is in modern fuels. I never had this problem 25 years ago on my Wren. I also do not like the design of the fuel pick up on this tank. Another glaring error I made was the lack of a tank sump for the fuel pick up. I also need a fuel shut off valve. The tank head pressure is overcoming the reed valves in the pumper carb, causing the engine to flood while sitting. The other problem I discovered, was that the fuel filter and line needs to be routed on the inlet side of the intake plenum.The fuel was cooking off when the engine was shut off causing a vapor lock and making starting hot very hard. I started laying up a new tank and I bought a special fuel tank epoxy coating designed to protect against the ethanol in the gasoline.  Anyway, better to find all of this out on the ground then of first flight!!!
















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MZ 34 Initial Run Up

Well I finally started the engine!!!!!!!!  My theory of engine mounting was correct!!! The vibration was absolutely minimal. This is so much less than a 277 Rotax!!  Once the engine is running above 1400 rpm, which is only 598 prop rpm, the engine smoothed right out. I am spending the rest of the week end breaking in the engine. Next week end could be the first taxi test. I am uploading a video The theory was explained in this blog post   http://www.blogger.com/blogger.g?blogID=25566109025005725#editor/target=post;postID=7281790481309410657

My Friend Yuki has a 277 mounted in a FP303, and the vibration is so bad, his instruments are failing. This thing is really running smooth. so later in the day I added the cowl. I was getting worried that the engine would not cool properly because of the cowl baffling. So my Buddy Ed and I installed the cowl and spinner and ran her up. The engine definitely cooled better, but the cowl is seeing high temps after shut down. Some of the paint near the exhaust pipe started to blister. I need to add header wrap to the pipe, and aluminum foil insulation to the inner surface of the cowl, and a heat shield between the exhaust and the fabric. Sounds like tomorrows job.



I added the foil and header wrap. Should be smooth sailing this week end. i plan on running the engine in for 5 hours before I attempt to fly. I bet my neighbors will be thrilled!!!

insulation

I used 3m automotive trim adhesive to bond the insulation. Aircraft Spruce sell this product.

header wrap installed

this should take care of the need for a thermal barrier against the fabric. There is a lot of air flowing there and during the run up there weren't any issues.

and finally here is a video of the second run up with the cowl in place. I'm pretty proud how well centered the spinner is

Quick update

I have been traveling for work for the last 2 weeks, I was home for one day between trips and I got a little bit done on the project. Luckily there are not any trips in the foreseeable future, so I should be able to get back on track. I am almost ready to start the engine for the first time. Today I made decent progress, I started setting the initial pitch of the ground adjustable prop. From this point on every job it the final step for that section and wont have to be repeated. Final fasteners are being installed and safety wire and cotter pins are being installed.

rudder cable fairing

here s the rudder fairing finally installed. Eventually I will paint it to match the fuselage.

rudder final installation

Here is the Rudder final installation. I ordered some new bolts for the tail wheel axle, but other than that everything is finalized.

That's all I have this week, I will continue to add to this blog entry later this week
















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