recent 700 kit - maingear runout ?

[rcmarty]

Building up a new 700 kit (thin framed with doublers) I bought on black Friday

I've been around the XX kits since the beginning with the 800 and the first shipment of the 700's

The new kit has a oneway hub that's not as tight on the maingear. (early 700 issue)

I have about a 2-3mm up/down wobble on the maingear.

I've been carefull not to overtorque the bolts to the hub and not tighten down one hard then do thru the rest. Instead I seated the first bolt gently then put the other bolts in then tightened up them in a head torqueing fashion.

I've also taken all the bolts out again and rotated the hub 1/4 turn to see if I can get a better result. It has improved a little where it currently is. Worse location was easily 4-5 mm out.

Anyone else had this issue with a newer kit ? Could it be the hubs are now undersized ? possibly gear warp ?

Side note : I ended up with 2 x .5 shims under maingear to prevent binding. (manual calls for 1x1mm + 1x.5mm)

Martin

[I Fly Helis]

It is ok to have some up/down play on the main gear. As long as there is no play in the auto/tail gear you are ok. A little bit of up/down on the main gear is good because it will insure correct gear mesh, and can self-correct its mesh

[Raptorapture]

Martin has been flying this kit forever so should be familiar with the Mikado strategy for gear meshing. The question is whether the wobble is during rotation, ie does not stay in same place vertically while engaged and spinning or in range of motion vertically when not engaged and spinning?

[rcmarty]

I have been running the XX series since they came out. This is my new 700 stretch to 770 project.
On this one I had to change up the shimming off the bottom 3rd bearing , needed to go down to 1mm spacing to prevent binding/drag on maingear.

I suspect it's a warped maingear , highspot seems to be focused on less than a 1/4 of the gear.
I'm concerned how it will feed thru the pinion. I'm assuming the one way locks into place when under load so this highspot is going to cause an issue going thru the pinion. Or at the very least accelerate wear.

Or the main gear is straight ( very plausible with Mikado moulding and plastic ) and the oneway center hub is undersized and causing issues on assembly.

I have another NIP gear here I can give a try. The more I think about it , the more I want to tear it back down and get it straighter.

I'm hoping I didn't get a Friday long weekend kit , tinkering with the tail box I got a rough bearing on one side of the gearbox sideplate , odd looking marks/sanding on the tailshaft gear , and trying to set the mesh on the tailbox isn't going well.

Martin

[rcmarty]

I finally got my hands on my 19t pinion.

Fired up the motor and it wasn't very good. Reminded me of the early align days .. lol

Chunk chunk chunk noise.

close look of the gear I see one tooth has a slight nick in the top half. Might have been dropped at factory.

So I got out the other nip gear I have and fitted it. Much quieter but still wobbles.

I went thru the 'too large oneway hub' problem on my first 700 build. This hub by comparison is way undersized (has 1mm wiggle room ) . My 800 had a firm fit to the hub and second 800 has the same firm fit to hub.

I'm suspecting the hub is the culprit. So I need to tear down an 800 to get the hub out and continue to chase this horrible sound. (or go back to align !! lol )

Martin

[rcmarty]

I managed to figure out the problem. The hub isn't right. Looks great but doesn't run true.

I took another hub of my 800 (still undersized IMO as it rattles around inside maingear) and put it back into heli with original gear. Gear runs much straighter and sounds much better.

Maingear has a nick on the topside of the gear for some reason , makes a bit of noise going thru the pinion but the goal for the last 2 nights has been why the wacky runout.

Martin

[RyanW]

Sorry to hear of the issues and good for chasing it down. Have you sent the parts to MikadoUSA or contacted Mikado Germany on these items? I am sure they would like to inspect them and get replacements to you!

[rcmarty]

I sent a message to Mikado usa.

They replied the next day requesting a video.

I told them the process of elimination I used and that I had to take apart and reassemble several times to find the problem. I'm hoping to not have to tear it down again , I've spent 2 long nights on this side project.

Currently the 770 is on track , I swiped the hub and maingear from a 2nd 800 that hasn't been flown so the parts are good to test with. Also had a NIP maingear for testing.

I told them it sound just like a trex 600 with a crappy maingear - wobbling up and down and making the chunk chunk noise. lol.


Ryan .. your pinion went out today , let hope Canada post can get the job done in time.

Martin