BananaHobby RC Repair Guides:
Replacing the Main Gear on a Contra Model Helicopter





 

 Preparation:

 This guide will cover the repair procedure for replacing the main gear on a Contra helicopter. You will need a few very simple tools for this job.

 A pair of pliers (needle nose is preferred), as well as a philips screwdriver and a pointed screwdriver or something similar are a must.

 A hammer is being used here to secure the replacement gear after it is installed, this is optional. You may also consider using a power tool for the screws.


 

 The first thing you will want to do is remove the canopy, this can be done by first sliding the plastic canopy off the mounting studs.

 Look at the very rear of the canopy where it flares back into points, there is a rubber stopper mounted on each side that secures it to the metal mounting stud.

 Slide the rubber stopper and canopy flare off both sides' mounting studs, and then gently ease the canopy off as shown.

 If you are having trouble, the second to last photo in this guide will show the mounting studs up close.


 

 Setting the canopy aside, flip your helicopter over and look at the bottom, there are several screws that needs to come out first before you proceed.

 The screw is shown being taken out in this photo, you will also remove the corresponding screw mounted on the opposite side of the helicopter.


 

 Once you have done that, move towards the rear of the underside of the helicopter, pass the rear set of landing struts.

 Now take out the screw being shown here, as well as the corrosponding screw mounted on the opposite side.

 At this time you should have removed a total of four screws, keep them in a safe place for now.


 

 Now you will need to remove two screws on the side of the helicopter, right behind the landing strut, these screws hold the tail struts to the main frame of the helicopter.


 

 Once you remove the screws the struts should come right off, keep these aside in a safe place.


 

 With these 6 screws and the struts now removed, the top and bottom halves of your main frame should come apart easily as seen here..


 

 Carefully remove the servo lead wires from the top part going into the recevier on the bottom part, it is recommended that you try to mark these leads in a way so you can remember which one belongs to which channel function.


 

 Your two halves of the helicopter should now be clear of each other, go ahead and set aside the bottom part, the main gear is attached to the top part only.


 Here is a view of the main gear, it is mounted to the main shaft in the center of the helicopter assembly, secured in place with a pin in the center as shown here.


 

 Now you will use that point ended screwdriver to push out the pin as demonstrated in this photo.


 

 Push the pin through and out the other side. If you couldn't find this tool, a paper clip or toothpick, or the smallest screwdriver in an eyeglasses repair set might work as common substitutes.


 

 Now use the pliers to grab the pin and fully remove it, set it aside, your replacement should come with a new pin, but it can't hurt to have a spare if the pin is in good condition.


 

 Now we will use one of the screwdrivers to gently leverage and ease off the old main gear.


 

 Now you can see the exposed main shaft as well as the hole where the pin locks in.

 Take care at this point, as without the main gear in place the main shaft and blades may fall off if nothing is underneath supporting them while your helicopter is upside down as you're working on it. Its a good idea to do this with the top of the main blades resting against a worktable.


 

 Here you can see the worn down teeth of the old gear, this gear will not be able to catch properly with the teeth on the motor drive shaft.


 

 Now we attach on the brand new replacement gear, ensure the holes for the pin are lined up, and push it into place.

 Also make sure the teeth are lined up with the teeth from the motor and are nice and snug.

 Remember to have something supporting your main blades and main shaft while doing this or you may end up pushing out the main shaft assembly.


 

 Now use your pilers to fit the new pin in, be sure to push the pin in fully so that the gear is secure.


 

 It should look like this when you are finished.


 

 Now we reassemble the helicopter, in reverse order as when we went over how to disassemble it for the repair.

 Plug the servo leads back in the receiver, and secure the bottom part of the main frame to the top and remount the screws and struts.


 

 Reattach the canopy, here's a closeup of the rubber stoppers on the canopy flare mounted on the mounting studs.


 

 All finished, you have successfully replaced the main gear of your Contra Helicopter.


 This repair guide has been brought to you courtesy of www.BananaHobby.com.