Thread: Discussion Walkera 4F200 3 blade head
View Single Post
Old Jun 24, 2012, 03:16 PM
IntegrityHndywrk is online now
Find More Posts by IntegrityHndywrk
IHW Heli Division
IntegrityHndywrk's Avatar
United States, FL, Palm Coast
Joined Mar 2012
8,585 Posts
Fix 4f200 tail Wag from worn tail drive gear

I hope this info helps some people out there. I'd really like to see more demand for the 4f200. With less talk about how it falls apart in the air. (which is just not true. You just have to use thread lock glue properly, like most machines, including helicopters this size and bigger) I really hope to see it move on to a devo package instead of being discontinued.

Anyway, on to fixing the issue with wear & tear on the rear drive gear caps.

Here are some symptoms i was having in flight:

1. First and most noticeable was a slight tail wag if I let off the rudder and stopped "holding" it in place with constant rudder input.

2. Second symptom was less noticeable at first. When giving slight rudder input the tail would feel unresponsive at first. Then kick in and move right over and move normal in that direction after. Till stopping and giving slight input in the other direction with the same result. This is the key indicator the tail shaft is sliding around.

3. In the shifting winds we get here on the coast of Florida. I noticed the tail would suddenly shift over when the wind changed direction. Then it would be fine till the wind shifted again or something else effected the tail.

The Fix:

My tail shaft rear drive gear caps are worn out and seem to be filed down some on the one side leaving around 1mm of play on my tail shaft. This tail has easily had 80+ flights on it and replacing it at this point, i would just call normal maintenance. But this little hack here will give the shaft new life and more flights. The best part is, for most people with a parts box for their 4f200 they already have the solution in their 4f200 screw kit!

The fix was simple really. I had a 4f200 screw set laying in my parts box. I was looking at it the other day and noticed there were some tiny washers in there. The ID on them is nearly the same as the tail shaft. Just a bit bigger. I simply opened up the tail box on the fin side. Removed the side bearing and put the tiny washer on the shaft and closed it all up again. To my surprise my 2 tail box screw holes were stripped out, probably from slapping my tail on the ground a few times the other day after doing some flips. Backing them out probably did the threads in for good. Thankfully, by removing the silver washers from the head of the screws i was able to get a few extra turns in. Just enough to loctite and close the tail up tight. I managed to get half a pack in today on it before it started raining. But the tail was rock solid like it was new again! I checked for any binding by hand spinning the main and tail rotors separately both before and after the flight. This washer seems to be the perfect shim size for this shaft.

I had a hard time photographing the washer. But here are some pics of it installed.
IntegrityHndywrk is online now Find More Posts by IntegrityHndywrk
Last edited by IntegrityHndywrk; Jul 08, 2012 at 05:07 PM.
Reply With Quote