500 Trex 450 DFC Pro Tail Drive Too Tight

[2WheelNut]

Hey guys, just had a little mishap. This heli is new to me and on the maiden flight I barely saved it from falling over and disintegrating. A lesson there as I was expecting to just fly her out of the crate. The tail hit the carpet and the tail drive stripped and the tail servo give up a few teeth as well. No biggie, so now I have it back together and the autorotation does not turn freely. It looks like the mesh it too tight with the tail drive. Any way to fix this? The new tail gears are the black ones and I replaced the white ones. Not enough teeth left on the previous one to count, but I have 28 teeth on the new one. Is this the correct count? The Align manual does not provide the tooth count.
Checking for mesh slop, the umbrella sets on both ends of the boom seem pretty good - just a hair of slop. It appears all pressure is being caused by the autorotation to tail drive gear.
Thanks in advance!

 

[Tony]

Try loosening the tail block from the frame, and pulling back on the tail block. If that doesn't work, then loosen the main bearing blocks and push them forward. This should allow you to move the mesh a little more on the loose side.

And as far as I know, there is only one tail drive gear (belt and TT) for the 450's. I know for larger helicopters, they have .6 and .8 and so on, but the 450 is just run what you brung. And also know, the black gears are about twice as strong as the white gears.

 

[2WheelNut]

Twice as strong. I'd almost rather strip the gearset than have worse thing happen. I have already tried moving the boom block back. Not much help there. I'll try the main forward, and then the motor as well as the mesh there is already fairly tight. Thanks for the feedback!

 

[Tony]

Motor is much easier to set mesh on lol. Let me know how it goes. There are other things you can do (but shouldn't have to) inside the tail block to move it back. Weird that it's too tight though. Usually those two gears are pretty loose.

As for what you said about the black gears, the reason they came out with those is for the mild tail blade strike in grass or dirt. Just that little bit can strip those white gears. We are not talking about the tail stripping out the auto-rotation gear or anything, just resistance against stripping when you have the inadvertent tail strike that any belt tail would fly away from.

 

[2WheelNut]

So attempted the adjustment on the main. No joy on that. So looking at the tail block, I don't see how it can be modified to get a little more play. I could dremel the frame around the tail block screws to get a little adjustment room...

Or, just try to find a set of white gears?

BTW - tried to log into the Phoenix session earlier. The password didn't seem to work for me.

 

[Tony]

The modification on the tail block is with the bearings that hold the tail drive gear. Most of the time (key phrase) those bearings are held in there way too tight. To get a helicopter spinning as free as it possibly can, I will use an exacto and shave the back side of the bearing housing to loosen the plastics grip on the bearing. This can yield about a 1-2mm movement to the rear that can open up the gear mesh. It doesn't always work, but worth a shot.

As for the dremel, I would not use that on the frame, they cut a little too fast. I just use a small round micro file to open up the holes to the rear.

As for phoenix, the password is rchelp all lowercase and no hyphen or spaces. We will have another one next sunday. If you have any issues, send me a PM and I will look into it.

 

[2WheelNut]

I'm still trying to understand the rear block mod. If you shave a little bit on the rear side of the bearing then doesn't that affect the mesh on the bevel gears (some call these umbrella gears..)? Seems like this would work great for a belt drive, but I'm missing something on torque tube equipped units.

Good call on the dremel. Certainly better to attack the frame with a file...

 

[Tony]

Yes, it would require you to adjust the TT gears mesh if you did the bearing mod. I would see what you can get done with the file. I'm sure it will be the easiest method.

 

[Admiral]

I had a similar problem with my 500 recently, after damaging the TT drive gear in long grass I fitted a new gear set, on the test flight it made a strange noise and I opted not to take off, when I killed the throttle the blade stopped spinning very quickly. When I pulled it down there was a tight spot in the umbrella gears, I thought of modifying the housing but decided against as I believed the fault to be in the gears not the housing.
I scrapped out the gears with a pointed modelling knife to remove and scrap left from manufacture then re-assembled the housing and gears the tight spot was still there, then I used a long Phillips shaft and a battery drill on HS and ran the gears for about 10 minutes.

The tight spot was 99% gone turning the gears by hand and not noticeable when back in the 500, it now flies well back to normal.

 

[2WheelNut]

I finally have all the settings updated in the 3GX (thanks for the videos Tony!) and it should be ready for first flight. I will make the frame adjustment, though I appreciate the Admiral's input. This would work except that mine isn't only tight in a single area, the mesh is definitely too tight to the auto-rotation gear and is constant. I will work on the frame tonight and get it spinning better before I re-attempt flying.

 

[coolgabsi]

Video or it didn't happen