Some build questions.

[grovey]

Hi all,

I have some questions about the build.

1.) I modified the one way, and re-assembled everything. When I rotate the crown gear by hand, it is not always smooth, it seems to hitch a bit at times, and sometimes smooths out again. Is this normal? I really hope I don't have a bad sprague.

2.) How many washers are needed between the bottom of the crown gear and top bearing of the hub/sleeve? Mine (UPGRADE) only has one, as well as the one that came with the kit. The manual shows 2 washers.

3.) I placed a 1mm shim at the top of the crown gear under the middle bearing, and 1.2mm shim under the one way above the 3rd bearing, and there seems to be 0 slop with the appropriate mesh, does this mean I can remove the shaft collar? Or should that be left there for safety?

Thanks all.

[rcflyerheli]

No there should not be any hitch. It sounds like there is something fowling the races of a bearing, or you have a flat spot on a ball or race. That kind of stuff in my experience always gets worse rather than heal itself.

I have one washer between the crown gear and the main gear. I think the other one will need to be used if there is vertical play in the main gear. I had to find an appropriate shim for the bottom of the main gear between it and the sleeve that the jesus bolt goes through. that was to eliminate the vertical play in my main gear.

I would seriously think that that sleeve needs to be in place. I recall that there was enough vertical play that shims didn't eliminate the slop, thus the sleeve was used to remove main shaft vertical play.

[grovey]

Great. I really hope it is not a bearing especially since I just finished modding the one way.

What I may do is remove the sprague and re-insert the top bearing. And see if the hitching is there. If not then I know it is the sprague.

If it is the sprague then I might get an aftermarket one.

I am going to continue with the build though.

About the sleeve on the shaft. My understanding is the formula kit does not have it? I have zero slop using shims(may change after a few flights) on the top and bottom of the one way.

[rcflyerheli]

I don't know about the formula kit. I did the head change last year, and the new shaft setup on mine made the collar necessary. I guess that you could shim above and below the crown/main such that you wouldn't need the collar, but I'd think that due to the nature of the bearings that are in the setup, you would really not be able to get all the play out of shaft or you couldn't get the shims into place due to the outer race of the bearings being wider than the inner race. If you could get the shims into the system, I suppose it would work.

I know there are some that say there should be some play, but I don't subscribe to that theory. If the main shaft is free to move up and down (even a little), every time you change direction on collective, that shaft is going to move and now you have the inertia of the moving shaft/head/blades hitting the inner race of the bearings when the shims tighten up. If you could get the exact correct shims to be the same as the od of the outer race, and they don't contact the inner race (sort of like the shims between the thrust bearing and the radial bearing in the grips) then you would be ok, but that is the only way I can see to make shimming alone take out the play. I subscribe to the no play but not over tight so that the bearings are preloaded theory.

[grovey]

Thanks, yeah tonight I shimmed top and bottom and there is still play so I think I will use the collar.

Good news is the bearings are ok. I did notice that I did not seat the top bearing correctly, and that once I did the one way seemed to move smoother, so perhaps the sprague is just fine. I will just keep an eye on it.

I placed a 1.2mm shim up top, which I know some advise against, or rather the majority of builds need only 1mm, but with 1mm the mesh seemed a bit too tight. 1.2mm yields slight play.

Oddly enough, I am running 1.2 top and bottom and there is play. Seems odd, but like I said and as you recommended, looks like I should run the collar.

[Matt Nasca]

Originally Posted by grovey

Thanks, yeah tonight I shimmed top and bottom and there is still play so I think I will use the collar.

Good news is the bearings are ok. I did notice that I did not seat the top bearing correctly, and that once I did the one way seemed to move smoother, so perhaps the sprague is just fine. I will just keep an eye on it.

I placed a 1.2mm shim up top, which I know some advise against, or rather the majority of builds need only 1mm, but with 1mm the mesh seemed a bit too tight. 1.2mm yields slight play.

Oddly enough, I am running 1.2 top and bottom and there is play. Seems odd, but like I said and as you recommended, looks like I should run the collar.

The shim thickness I use for the top is between 1.12-1.14. This gives the slightest perceptible click between the crown and TT drive gear. Also make sure the boom is pushed in all the way.

If you shim above the lower bearing support, under the oneway assembly, you can get it tight so there's no play. I took off my collar and haven't had any issues. Just makes sure there is no up and down play.

[grovey]

Thanks Matt

.12-.14, is that in inches? what is that in mm? I am a metric man hehe.

I will look again tonight to see what I can do there with the shims, the solid shims are 1.2mm, but you have you stack others to get 1mm, When you stack them they are infuriatingly difficult to press into a gap to install.

My boom is all the way in, and can see a good mesh when looking from the side.

Something else I noticed last night, is there seems to be play between the main gear and the crown gear. Will need to take a closer look.

[rcflyerheli]

That play between the main and crown gears is what I had to shim out on mine. I had to put a shim between the bottom of the OWB and the top of the sleeve that takes the Jesus bolt.

[grovey]

Originally Posted by rcflyerheli

That play between the main and crown gears is what I had to shim out on mine. I had to put a shim between the bottom of the OWB and the top of the sleeve that takes the Jesus bolt.

Yeah I think that may be where the play is on mine, I may need to do the exact same thing.

If I can get rid of that play, then I think I am golden.

[Matt Nasca]

and the stack of very thin washers that make up a 1.12mm stack.

[velocity90]

Originally Posted by rcflyerheli

That play between the main and crown gears is what I had to shim out on mine. I had to put a shim between the bottom of the OWB and the top of the sleeve that takes the Jesus bolt.

Yes, me 2 else i couldn't get a washer underneath it also.

I also use 11mm on top. With 10mm the gearmesh is tight and with 12mm there too much play. 0.1mm shim makes a lot of difference.

I couldn't find the thicknesses I needed so glued all together (10+0.1) did the same at the bottom. Now replacing main gear isn't a disaster

[grovey]

Reporting back, thanks all for the help!

1.10 mm at the top, 1.20mm at the bottom with the main gear shimmed as well (1 shim), and all is good! No play, and adequate lash.

[grovey]

So it looks like I will be pinning the boom at the center, not right by the last clamp per the manual.

Good idea? I read a post by Rob Cherry stating that pinning the boom at the last clamp could increase fatigue there.

Also, should I use the stock 3x8, or purchase a 3x10? The 3x8 would be enough to clamp down, or barely tap a hole. Obviously the 3x10 would be able to protrude into the boom.

Lastly, do you guys pre-drill or just let it self tap?

[velocity90]

Originally Posted by grovey

So it looks like I will be pinning the boom at the center, not right by the last clamp per the manual.

Good idea? I read a post by Rob Cherry stating that pinning the boom at the last clamp could increase fatigue there.

Also, should I use the stock 3x8, or purchase a 3x10? The 3x8 would be enough to clamp down, or barely tap a hole. Obviously the 3x10 would be able to protrude into the boom.

Lastly, do you guys pre-drill or just let it self tap?

Correct, I also swapped it, also to the tywrap mod and don't over tighten the clamp. Thin layer of tape is a good idea.

[grovey]

Originally Posted by velocity90

Correct, I also swapped it, also to the tywrap mod and don't over tighten the clamp. Thin layer of tape is a good idea.

Yeah I put tape down, and I also have purchased the Rave boom support.

Did you use a 3x10 screw for the pinning of the boom? And did you drill or let it self-tap?

[velocity90]

Originally Posted by grovey

Yeah I put tape down, and I also have purchased the Rave boom support.

Did you use a 3x10 screw for the pinning of the boom? And did you drill or let it self-tap?

Use the supplied one. It isn't really nessesary anyway, 3 clamps

[omerco]

Originally Posted by velocity90

Correct, I also swapped it, also to the tywrap mod and don't over tighten the clamp. Thin layer of tape is a good idea.

I replaced the 3x6 bolts for the boom supports clamp with 3x8, green locktite and zip.
The 3x6 leave 3 mm to go in which is too little. There is room for 3x9 or even 10.
Mine never opened

[grovey]

Originally Posted by velocity90

Use the supplied one. It isn't really nessesary anyway, 3 clamps

Thanks again, I used the supplied one, kept tightening and backing out, rinse and repeat until it could seat properly then tightened it down. Yeah, 3 clamps should be good enough.

[Matt Nasca]

There is no problem pinning through the end hole. I've never seen or heard of an issue with that. groovy's method is the one I use as well.

[grovey]

Originally Posted by Matt Nasca

There is no problem pinning through the end hole. I've never seen or heard of an issue with that. groovy's method is the one I use as well.

That is good to know, I did that just as a precaution as I read a post here by Rob Cherry about another brand helicopter having its boom break at the last clamp. It wasn't the X7, but I felt I would move the pinning point as well.

This build is taking me way too long, I am hoping to finish it soon. Getting there.