Subaru EA 81 Engine Mounting

[techie49]

Does anyone here know where I might get a mounting (frame) for a Subaru EA81 to fit a Zodiac 601 XL. I suppose I'd be able to get one from the States but the cost and shipping makes it quite expensive. Someone in Australia must make one ????

 

Paul Toone

 

 

[bushcaddy105]

It's not difficult to make your own. Chrome Moly tube is readily available in Oz and easy enough to notch to fit together on a simple wooden jig which provides the correct distance from firewall to engine. A professional welder will then zip it together for you (TIG welding required, NOT MIG)

 

 

[techie49]

Cheers for that John. I'm rapidly coming to that conclusion. The only point which concerns me is any offset from a straight line to allow for the torque of the engine. I think you have to allow a degree or so, I'm no expert there. It would be nice if someone had an engineering drawing instead of re-inventing the wheel (badly).

 

Regards,

 

Paul Toone

 

 

[Guest Old_Plane_Nut]

engine offset

 

working on a Petenpol aircamper at the moment which the builder had offset the engine THE WRONG WAY. Had a massive trim tab had the new owner complained to me that he had a sore right leg from holding severe right rudder all the time. Aircraft inspected and flown like this and not picked up. Infingcredible. Basically you have to work out the Pfactor of the prop to decide the offset and down thrust of the engine off choice. Do a little bit of research on P factor so that you understand the forces that are involved. But for an E81 with belt reduction, about 3 degrees to the right viewed from the cockpit and about 2 degrees down. I make my engine mounts so that they are adjustable ( using rose joints ) until I get the aircraft to fly handsoff and then replace the rosejoints with steel T joints. I'm making one for a VW at the moment so if you need some photos let me know, Not difficult just a bit of thought and a fair amount of welding. I make mine out of 4130 for lightness but its not really necessary idf weight is not a concern or you need a bit of weight in the nose.

 

Cheers

 

James

 

 

[facthunter]

Offset and welding.

 

There is a small problem with 4130 and welding especially with TIG. There can be a hard line near the weld formed by the rapid cooling. To get the full strength that 4130 affords, you should heat treat the frame, or normalise near the welds, at least.

 

Engine offset. The correct amount of sidethrust will cancell out the engine slipstream effect on the rudder. The beauty of doing it ths way is that nothing else changes. If you do it by rudder offset or trim tab adjustment, change of power setting still affects the way the plane flys. You might have to do abit of remodelling of your cowl when it is done. Nev

 

 

[David F]

Welding Chrome Moly Tube

 

Shouldnt it really be welded with oxy acetylene ? 3150 deg c with a fairly slow weld progress campared to a TIG (much hotter at 6000 + much quicker) Wider throat thickness and post weld heat treatment (due to slower weld progress ) reduces the risc of cracking.

 

What do you recon guys ?

 

Dave

 

 

[Guest Old_Plane_Nut]

TIG welding 4130

 

I've done this for a lot of years and did an advanced welding course at TAFE. Iwas even going thru the process offf being Certified as an aircraft welder but then realised you need a lot of work to maintain your certification (2 grand a year in 2004 ) so didnt continue with the certification. Up to an including 65 thou wall thickness tubing no preheating or post treatment is necessary or recommended. Above this wall thickness, the welds are supposed to be postheated to cheery red and let cool to normalise the 4130. You do this with oxy acetylene. Why dont you just weld with oxy you ask. Well the danger lies in overheating the 4130 and basically cooking the steel and all the strength out of it. Tig welding 4130 is very easy and the heat is very localised for a minimum amount of time. It doesnt pop and fizz like other types of steel and even tho you can spend a fortune on special welding rods, I've found double or triple deoxidized welding rods ( for mild steel ) work very well. All welds, the weld is stronger than the parent metal and can fracture right next to the weld. 2 or 3 times deoxized rods the 4130 weld is slightly weaker but I've put my life on the above and fly several of my friends aircraft and my own that I've made mounts for. The petinpol has a 50mm * 50 mm box section mild steel rail frame mounted to the firewall and 2 mild steel tubes running from the top of the firewall to the heads to give both the offset and the down thrust. Apart from being offset the wrong way the mount is plenty strong enough. James

 

 

[Downunder]

I have heard of engine mount builders fitting a schrader valve (the valve in car tyres)

 

and a small pressure gauge. Pressurising it to only a few PSI. If the gauge drops to zero then you may have a cracked mount.

 

 

[Guest Old_Plane_Nut]

pressurizing the engine mount

 

This is virtually impossible because most engine mounts are made up of individual tubes. This means that you would need a valve on each tube to prove that it was air tight. I find a lot of the time that you cant get all the way around a weld and you have to accept this. You have to then drill a hole in the tubes and fill with fish oil or something similar to protect the inside of the tubing.

 

On the other hand there are times when you need to purge weld ( especially exhausts as you need a cleaner airflow in side the tube ) You need a second pressure reg and tape off all the joints you are going to weld and then put the rubber tube tightly in one end and at the other end XXXXX a hole. Turn on the second valve and pressurize the tube with argon. the little XXXXX hole will let the oxy escape (which contaminates your weld) and you will get beautiful welds inside and outside the tube. Very expensive to do. Twice the amount of gas and ten times the fiddling about. I forgot to mention heat crayons earlier. You draw a line on the steel you want to heat treat. When it gets to the required temp, the line suddenly dissapears. Hey presto. You have the metal at the required temp. Gasweld, BWIP etc carry them

 

Have a go

 

James

 

 

[Guest Wigg]

Techie49 I see you fly out of Moorabbin I take it you know the area well? If you are not confident in doing the welding yourself we use Aerospace Welding Services on the cnr of First Ave & Second St. Don't know if this is any help

 

 

[Guest Old_Plane_Nut]

offset and down thrust

 

I dont know this aircraft well enough to describe the engine mount, but if someone else undertakes it, they must know the off set and down thrust and then build a jig to hold everything true while they weld what they can get at it in the jig. Then temporary reinforcement plates need to be tack welded across any tube meeting points before taking the mount out of the jig. The one I made for the AT3 ( Polish all metal low wing ) cost the owner $A 1800 and that was mates rates with the 4130 included. You might think this is expensive but there was 3 weeks work doing it. So 1800 less expenses and then pay tax on it. Would you do it for 3 weeks work?

 

The Sub 81 is easily mounted as I explained. Just need 2 rails for the 4 engine mounts to sit on and then a tube from each of the 4 extremes of the firewall to give the required down thrust and offset. Buy the Tony Hayes Manual Firewall Forward. The information is still valid even tho the last printing was many years ago.

 

You dont need 4130. Its just 3 times as strong so you can reduce its wall thickness by half the structural steel equivalent and it will still be stronger. Do the weight and balance and decide how far forward of the firewall the engine needs to be and if weight is not critical make one out of structural steel. What category is the aircraft going to be registered in. You'll learn a hell of a lot if you do it yourself

 

James

 

 

[facthunter]

Correction.

 

I think you mean Tony Bingelis Firewall Forward? Nev

 

 

[Guest Old_Plane_Nut]

Firewall forward

 

Sorry, I got my Tony's mixed up after reading the articles about Tony Hayes life

 

Your are so right about never stopping learning. Thats why I encourage the building of the engine mount by the owner. Its also the reason I asked what category the aircraft will be registered in ans he may not be allowed to do the welding depending on the category.

 

If you do as much as you possibly can on your own aircraft, then you understand it a lot better and it does become part of you. You know why you need that right boot on the rudder all the time or the plane changes trim a lot when you increase or decrease power. You know the angle of incidence because you did it. You know how much down thrust is developed by the tailplane because you did the calcs and set the down thrust.

 

Surely this makes you a better pilot than the guy with the checkbook

 

Sorry about the rant but even the 51 % rules are a load of crock

 

James

 

 

[Tony2]

Gotta love google images for search

 

Subaru EA81 Engine Mounting - Google Search

 

This is a well respected site Look no tubes

 

Motor Mount

 

The mount holds the engine at 1 degree down and 1 degree right which is as per the O-200 plans for this airplane. I found that my EA-81 installation was very sensative to power changes when mounted at zero-zero and decided to follow the O-200 recommendation for this engine.

 

Subaru engines

 

EA-81 DDT Info

 

SUGGESTIONS FOR BUILDING A ROTARY ENGINE MOTOR MOUNT

 

http://mthobby.pcperfect.com/ch601/chengine1.htm

 

Not reinventing the engine mount email the people that have made an engine mount and then document you experience to help more people

 

Good Luck, and the offset still can be corrected with shims ? starting point 1 degree?

 

and for everyone one that has considered a subaroooo Manuals to download

 

http://www.finleyweb.net/JonsStuff/SubaruDocumentation.aspx