Little Wing Tim Mercer Yamaha Geared PRSU

There have been two types of redrives for yamaha engine conversion on a Little Wing. Both are exciting as they both are dealing with finding the solution to finding an affordable, powerful and reliable powerplant. Not only for general home builts but more importantly one for the Little Wing.

Two choices have emerged, one is belt drive and one is using Todd's engine cage with geared reduction unit. I started this post for Tim Mercer as he has chosen geared reduction. Tim has been making GREAT PROGRESS ! Here is the latest email as sent to me:


James,


I have not been in touch for a long while! Hope all is well! I see you are making progress with the 2 place and the Yamaha engine layout! It would not be any fun if it were easy! RIGHT! LOL!

I wanted to post some pictures on the forum and show my progress but with computer issues I get locked up and the computer shuts down while trying to post so I gave up. Here is where I am at on my Little Wing today.

I had to work out how to get the cowl over the top of the engine without remaking the instrument panel, boot cowl and firewall. I added 2.25” to the top of the nose bowl I bought from Aircraft Spruce after I had raised it with a bent form and that was not enough so I fiber glassed an add on and then made a reverse scoop of aluminum to cover the water fill cap but still allow the gull wing doors to hinge from the firewall to the nose. It worked out well and looks kind of like a super cub now. I still have a few things to work out before I dismantle it for the umpteenth time and start covering and finish work. You may share these with the others as you desire and if you want and can you are welcome to post them on the forum under your “booster progress” post.



Take Care



Tim Mercer

Way to go Tim, I am excited for you and I appreciate you showing your progress. These photos will help me as I just got my engine from Todd.

jtm

An interesting setup you have there Tim, however I must speak up about the location of your radiator.

All radiators must have free cool air coming in through the cooling fins to be effective. In addition, the incoming volume of cool air must be of a higher pressure differential than the heated air that is exiting behind the radiator and out the cowling.

With your current setup, incoming air into the cowling will be heated up by the engine and exhaust manifold. Second, as I see from the picture, the air in front of and behind of the radiator will have no pressure differential and thus there will not be effective flow through the cooling fins.

Jess Meyers of Belted Air in Las Vegas, Nevada, has created a very effective method of radiator cooling with his Chevy 4.3 L V6 setup for Van RV homebuilt airplanes. The following pictures shows how Meyers' effectively baffled the engine and manifold heat away from the radiator by ducting cool fresh air over the top of the engine (creating a positive plenum chamber), through the radiator, down the back side near the firewall, and out the bottom of the cowling. A traditional cowl flap is mounted to control the amount of air allowed exit the cowling.

Understandably with your inline engine, you will not be able to duplicate exactly Meyers' setup, however you get the idea. Interestingly prior this setup, Meyers used two GM air conditioner evaporator radiators mounted right behind the cooling intakes. You could duplicate this first method, change the cowl and duplicate the radiator setup that the Curtis P-40 used, or set up the radiator just below and behind the cowling and in front of the landing gear as many Kitfox builders do.

Wayne

Wayne,
Thanks for your comments but i have no worries for my engine cooling. This is a work in progress, what is not in the pictures is the 12" electric fan for radiator cooling that will be mounted on the front side of the radiator and the baffles that will direct "cool" airflow directly to the fan and radiator from the top over the engine and the outside bottom of the cowl as well as through the nose bowl holes and AWAY from the exhaust. The 2.5" behind the radiator is more than sufficient to exhaust warm air and will be directed out the sides. I also have 3-2" hoses directed at the radiator for fresh air in and calculations show more than enough airflow for cooling with all the baffles and hoses. You should see how tight the radiator is packed in the snowmobile this engine came out of and that radiator is half the size of the one i am using.

Tim

Tim i watched video with engine running up. Whenever i do it with mine you can see the whole plane trying to move ahead-even side to side as tail tied. I dont know why but it seemed like engine running way up but not loading up. I know youset pitch by some numbers but i wonder if you set it up enough to load engine. Just guess I'm wondering what thrust test is telling you. You definately got power available just wondering how much it was trying to pull. keep up the great work!

James,

The camera angle does not show all the detail. It really tried to lift the tail numerous times and with way i had the strap on the tail to my trucks drop hitch if i would have throttled up more it would have pivoted and hit the prop and i was full on the brakes as well. i have yet to do a thrust test but i am sure from what i felt the day i did this video it will pull what Todd's engine did which was 450LBS. I have my propeller set at 13.5 degrees and my redrive is a 4-1 gear ratio. At 8500rpm for the moment i got there was EXCITING to say the least.

Post a video of yours so i can compare visually!

Thanks

Tim

I remember when my direct drive setup could not be held in place when i ran throttle up. It was screaming and a whole lot of air. Heck- in my old posts I think I mentioned turning my head sideways and glasses being blown off into grass like twenty feet. I remember crawling around thee ground carefully feeling for my glasses.

All that just to find I was putting out 230 lbs. Enough to feel like it was producing the thrust needed. As the plane sits with tail on ground and the brakes on it will try to rotate up onto wheels/longerons parallel to ground. (With tail strap preventing nose over) I dont have video handy but i did post pix from thrust test. I'm just saying that I remember how it felt soooo strong but until I got pitch/prop setup.... it wasnt doing enough. (Everyone knows how disappointed I was) When I got 380 I knew the difference only when I measured it. the engine rpm went way up withe the 10'' bigger prop but that could have be done by lowering the pitch. The only way to quantify the feel was to measure it again.

I'll just say with the prop disc not parallel to ground.. air blows and hits the disk,the fuselage,the tail etc. And it doesn't just sit there. At less than 3/4 throtte the brakes wont hold her . I'm thinking you'll be at least 500 but you will not just have an rpm.

I saw a fixed wing experimental once that landed at my airport to get fuel. He had a Yamaha engine WITH ITS transmission.

As he climbed out in second gear and nosed over to "cruise-climb" he shifted into 3rd.
We were cracking up!