Setting up the three ratio metal gearbox

We discontinued the Mini Olympus gearbox because of continuing quality control issues so in it's place we offer this metal gear, ball bearing box that is of much better quality for not much more. It is a bit more work to set up properly so we offer this instruction sheet to help answer questions that we have encountered.

First lay out and familiarize yourself with the parts. If you didn't purchase our Emm motor mount then disregard it. Notice there are three pinion gears. The largest pinion will give you a 2:1 gear ratio for the fastest prop rpm but you will need to use smaller props. the middle size pinion will give a 2.5:1 ratio and will spin a larger prop for a given amp draw. The smallest pinion will produce the most power at a 3:1 ratio and will spin props as large as 12" diameter. You will have to experiment with different types and sizes of props to find what ratio/prop works best for your application. 

Use a precision screwdriver to install the two screws provided with the gearbox. The screwdriver will have to be able to fit through the hole directly above the screw. Leave the screws loose enough to slide the motor up or down and put the pinion you want on the motor shaft. I would start with the 2.5:1 pinion and about an 8x6 prop to begin with. You will need a set of metric and inch Allen wrenches to assemble this gearbox so if you don't have any, I would recommend purchasing a set of "ball drivers" because the end has a tiny ball shaped hex on it that allows turning set screw on a little bit of an angle. Tighten the pinion down to the shaft. This is the important part!! You have to adjust the gear mesh so it is not too tight and not too loose. Snug one screw and loosen the other so the motor can be pivoted in and out of the main gear. Push the motor in tight to the main gear then back it out slightly so you can see a little bit of space between the teeth. Spin the prop shaft and check that it spins freely. When I am sure that the mesh is correct, I snug one screw, run the other one out and coat the threads with GOOP or "re-movable" Loctite before putting it back in and tightening it down. Then do the same to the other screw being careful not to change the gear mesh.

If you want to use our Emm Motor mount, this box has two screw holes that match up to the mounting holes in the motor mount. The threads may be a bit to large but if you use Goop or Loctite on the screws and don't over tighten, it should be fine. We have also found that #4 pan head sheet metal screws cut off to about 1/4" work even better to attach the Emm to the front of the box. Run the screws into the holes to make threads then take out and cut off and use goop or Loctite to secure them. Bend the tabs back and fasten to you plane using # 4 sheet metal screws. I would suggest supporting the back of the motor with a block or something also.

Well this is about it. I strongly recommend balancing the prop before running because an unbalanced prop will shake a gearbox apart. It is a good idea to balance any prop before running, even gas engine planes but it is essential for electric because the airframes are usually very light and power is small and an unbalanced prop will rob precious power and can do some damage to boot. We have a simple prop balancer available for $5.50 that will do a fair job for not a lot of money. 

You should be aware that gearboxes and electric setups in general are not very tough. I would recommend using our 7x6 soft prop or a folding prop and the 2:1 ratio for beginning pilots. These props will be more forgiving in a crash. It is very possible that you will bend the prop shaft, especially if you are learning to fly. If you do, take the prop adapter off the gearbox and gently bend the shaft as straight as possible. You may well ruin several gear boxes - motors - even speed controls before mastering the hobby. All you can do is grin, take your lumps, and move on. Every expert pilot out there has a secret pile of junk from the early days that he would never admit to having. We are here to help all we can and maybe even bring the learning curve up a bit. Remember, we've all done stupid things and smashed things up a bit but the reward is soooo worth it when you see your latest ship sailing by in complete control --- what a rush!