Deandome

My Feedback: (1)

Just got back from picking up my OS 55ax But looking at the mounting instructions for my Sr. Falcon, I have some questions.

The engine mounts to a plywood 'mounting plate', and that plate is either glued or screwed to two mounting rails on the plane (depending on whether you want a 'breakaway motor' or not). Anyhoo, per the instructions, that mounting plate is supposed to be a tad asymmetrical, to put the motor off-center (to the left) a bit, which I believe is to compensate for the rotational forces of the prop (you're also s'posed to mount the plate at about a 2 deg. angle).

Problem is, that plate is NOT asymmetrical, and it's also a bit big to fit in the motor-space/on the rails. I can/will sand it down to fit, but I figure I'll need to build in the asymmetry when doing so. So my question is...how far off-center should I mount the engine? Looking at the plate in the instruction photos, I'm guessing only about 1/4" or less, but I thought I'd check.

And no, I can't get a new one from the mfg, as this ARF kit dates back a bit to before the time Great Planes took over Goldberg (I guess I could check, though).

Thanks for your help!

KitBuilder

I built the CG Eagle a coiujple years ago and it had the same system. Ply plate with cutout in a U shape for the motor that sits on / attaches to rails. Look closely at that plate.. the a-sym will be slight and you'll want the nose of the motor pointing right when looking from behind. The rails should also have the required downthrust already in place if an arf.
Mike

KitBuilder

j.duncker

My Feedback: (2)

1/8 th fibre glass plate is a better material than ply.

If using ply get some good quality marine ply with at leat 5 laminations.

ratshooter

I looked up the instructions for your plane on the Goldberg website. It didn't say anything about downthrust so I am guessing its built in like Kitbuilder said. It also said you need 2 degrees of RIGHT thrust. Thats not very much. It also said the engine plate is thinner on one side and the thinner side goes to the left side of the plane.

For my own planes that do not have flat bottomed airfoils I just go zero zero on the thrust line. Flat bottomed airfoils get about 4 degrees of downthrust depending on how much power they have.

ratshooter

I went back and read your post and it sounds like you have it figured out correctly. Just a slight amount to the right should be plenty of right thrust. If you have any drafting tools you draw a straight line and then a line at 2* and see how small it is.

red head

Once you decide how to mount the engine be sure that you fuel proof that plate and the rails real good along with the firewall. ENJOY !!! RED

bingo field

Roger that what Red Head said. Thin some 30 minute epoxy with some denatured alcohol and brush on several coats, thinned out it will soak in pretty well, and it will give you a great fuel proofing job. I think it helps make the firewall stronger, too.

Hossfly

Rather off topic however I do like to pass this on as in today's ARF world it gets hidden. I used alcohol for many years to thin epoxy. Then some 20+ years ago another old timer showed me a trick. Mix your epoxy, and for the subject job 30 min is good or whatever you wish. Brush some, sloppy as you wish, on the area to be covered. Turn your heat gun or money-kote heat gun on and proceed to heat things up. Don't allow splashing on anything as until you try this you will be surprised as the epoxy just turns GIN-THIN and runs into every crevice. Secure the model so you can brush and heat. Wood grain, cracks, crevasses, all get filled. Lasts a long time. BTW the set-up time is much less than the stated epoxy time.

bingo field

Hossfly, would it be good to mention that you want to obviously keep that heat gun away from any covering material in the vicinity, lest you accidentally shrink it down. I forgot all about using the heat gun, it does make the epoxy run when it gets heated up. And the cure time is greatly reduced, down to minutes after the wood cools.

Deandome

My Feedback: (1)

Thanks all!

I measured both sides of the mounting plate/my digital caliper, and the difference is miniscule...like 1-2mm...which seems like it's symmetrical/within normal mfg. tolerances. And as-is, it cannot even fit in the engine bay, so I'll have to sand it down a bit. The motor is also too snug & spreads the rails a bit if you force it, so I have to sand there, too. I'm thinking/guessing that the wrong plate was put in this kit, so I THINK I might build in a little more 'asymmetry' when I sand it to fit...maybe not.

As for the engine-bay sealing, there is indeed some kind of coating of that already applied by the factory, so I"ll probby only do one coat of epoxy.

On another note, I'm re-thinking the recommendations I got NOT to set up my tank w/a special fueling valve/dot. Cuz if you [link=http://www.osengines.com/engines/osmg0556-a.jpg]look at the engine[/link], you'll see how the fuel nipple is nestled tightly behind the needle valve, so fueling via the engine's fuel line seems pretty problematic. And the fuel tank itself is located under a hatch-cover that you need to secure w/screws (see [link=http://manuals.hobbico.com/gpm/gpma1967-manual.pdf]page 19 of the manual[/link]; again, not conducive to easy refueling.

So what do you think would be a not-too-complex option...figuring in that I'll have the Hayes fuel tank?

Thanks again!

ratshooter

Can you pull the fuel line off the nipple with hemostats? I gad cub that I had to do this with. It wasn't a big deal. There used to be an inline fuel filler that would shut off the flow to the carb when it was lifted out. I don't know if it still made or not.

On the engine mount just sand it till it fits. Don't kill yourself worrying about side thrust. I am scratch buuilding a Sweet Stik right now and it will be set at zero zero thrust lines.

jester_s1

The simplest way to fuel would be to put a Tee in the carb line and run your fueling tap out from that. Just make sure to zip tie each fitting on the Tee so that nothing leaks from getting tugged on. If you close your throttle while refueling, the tank will provide much less resistance to the fuel flow than the carb will, so flooding shouldn't be a problem.

jaka

Hi!
Always think of following the KISS principle!
Use a third line for fueling! Do not use a fuel-valve!

JohnBuckner

My Feedback: (1)

The solution is so increditably simple and there is never a real need beyond just a simple two line system with the exception of pressurized and pumped fuel systems. Look at the two pictures and notice the fuel line at the carb nipple is never unplugged but a simple 3/8th inch tank tube is located wherever you choose and fueling is always done from there.

Avoid the fueling devices and unneeded third lines or tees especially for this airplane which is an exposed engine. All thats needed is a simple little bit of brass or aluminum tank tube placed wherever you need it.

John

red head

If you put a " T " in your carb line ~~ you will flood your engine and end up with a real mess. ENJOY !!! RED

cfircav8r

My Feedback: (1)

I do what John said, only I use an inline filter instead of just a brass tube. Either way works great.

jaka

Hi!
I thought he had and engine with the needle mounted on the back plate and could not remove the fuel line from the nipple when fueling!?

Mikecam

I like the 3 line system because the 2 line system will trap any dirt from the fuel jug on the wrong side of the pick up screen. It's the only screen I use on my stuff. 2 line and fueling from the tank side of a filter would work as well with your clunk one that does not have a screen.

JohnBuckner

My Feedback: (1)

Good morning jaka, well Um its morning here anyway The Subject engine is an OS 55AX and what he was talking about was the proximity of the inlet nipple just inside of the new slant back main needle valve. He even posted a link to a picture of an AX.

Its not really a problem even not using a cut and brass tube in most open top cowls to just remove and replace the line at the nipple just like any trainer but the short connector is even more important for engines with rear needle valves as they are a problem sometimes to remove and replace in that tight spot between the engine and the firewall.

The same system is just as effective with any size or cowled airplane also. A simple split between the carburator and the fuel supply is all that is ever really needed with the exception of the YS pressure systems as I noted.

John

Pylonracr

Slightly off topic here, but is your 55ax new? If it is, it NEEDS to be broken in properly. I love these engines, but OSuses nickel plated liners instead of chrome and therefore have unique oil requirements. Make sure your fuel has enough oil in it, and has some castor. Feel free to PM me if you have any questions. It is fairly simple, but something you have to keep in mind if you want this engine to last.

Best wishes.
Scott

Deandome

My Feedback: (1)

NO...that's the beauty of this (that...and the price of $80!!). It was broken in by a super-experienced pilot, then flown THREE times (a large, scale plane, I think), then he sold the plane & had the motor sitting around. It looks pristine...I think I'll even try the plug that's on it before throwing a new one on!!

After picking it up far from home, I happened to be near Al's Hobby Shop in Elmhurst, IL...probby the biggest/best shop in Chicagoland, so I headed in for some supplies; prop balancer, 2000mah NiMh Rx pack, etc...and I asked about fuel. I even called the seller, and he couldn't remember anything other than it was 15% nitro. The guy @ Al's backed that up, and he recommended [link=http://store.alshobbyshop.com/omega15fuel-1gal.aspx]Morgan's Omega 'pink'; 15% nitro/17% lube[/link], with the lube being 70% synthetic & 30% castor. He said stay away from all-castor (that's for ringed motors these days), and while I'd be good w/100% synthetic, he liked the blend.

So I got a gallon...gotta say that $18 a gal. was a nice change of pace from how much $$ car fuel costs!!

BTW, he threw in two props; a 12"x6, and a 13" (can't find the pitch listed on the hub...strange, as they're both Master Airscrews)....I think they were big cuz the plane he had had a big cowl. People here were telling me to go w/11", and I don't mind ponying up $5-8 for a prop. But can I use these, either as-is or cut down & balanced? Or are cut-down props only good for breaking in new engines?

Pylonracr

The 12x6 will work, but I would probably put a 13x5 on it to slow the plane down a little bit.The beauty of props is that it only costs 3 bucks to tell if it works better.
The engine that was bench run and flown 3 times. Not broken in, but on its way. Add 3oz of oil to the first gallon of fuel and 2oz to every gallon after that. The OS nickel liners like more that the industry standard 17% oil. You can get a quart of Klotz castor synthetic blend to add to your fuel for about 12 bucks or so, and it will do15 gallons of fuel depending on how accurately measure. Not super critical, just get about that much in your fuel and you will be fine. The other option is buy fuel that is all synthetic and add 2oz of castor to each gallon. The few extra pennies in oil will pay off greatly when you have a few years on this engine and it still runs well. Never run this engine with all synthetic, this thing needs a little castor.

Welcome to the addiction
Scott