Help - Gear Mesh

[mdu6]

I'm thinking something may be up with the OS cases because most of the people I see asking about shims are using the OS 105.

Look at the attached side view of the OS105 (or for that matter any other OS engine will do).

The bottom of the engine mounting lugs is inline with the center of the crankshaft - this is the base of the engine geometry and the only one that could come into play (from the engine point of view) in the gear mesh (putting aside distorted engine cases/crankshaft fabrication errors).

If someone as the gear mesh problem - it should be easy to check that the lugs do line up with the center of the crankshaft.

[Kevin Feil]

Great Responce MD! Thank you for sharing that..

K

[Rctintin]

OK, my shims turned up today (Thanks Climb Out the UK Synergy Importer) and with a .5mm shim it feels a tighter mesh than I would normally use (paper strip method) and with both .5's (1mm) in there, its a bit to loose, so I have gone for .5, and I'll keep an eye on the mesh after each flight for the first few flights.

[Rodney Kirstine]

That's good news, Rob.  Are you going to be able to maiden it soon?

On the gear mesh, mine is also a little tighter than what I would normally set for main gear lash but it's been running awesome.

[flyalan]

There should be very little place and as long as there is no binding you should be good to go.  I keep almost no play in the gear mesh on any of my Synergy's.  Never had an issue.  For me the paper method is too loose with the helical gears and pinions.  Even using thin paper I would rather set it by feel. 

Cheers

Alan

[Rodney Kirstine]

For me the paper method is too loose with the helical gears and pinions

I stripped a main gear on my E7 setting it this way and I've been doing it by feel ever since.

[flyalan]

When I check someone's Synergy build the first thing I do is inspect the gear mesh.  I think folks that are used to straight gears expect the mesh to be the same as with a helical set.  Not so!  Only once in the past year have I seen anyone running too tight a mesh and on that one I could immediately tell when he spooled it up.

Cheers

Alan

[mdu6]

One other point on the finer details of engine/main gear alignment.

Don't forget the clutch/start shaft is as important as the main gear/engine alignment. Before committing all screws with Loctite - check that when you turn the hex adapter/start shaft counter clockwise, you feel  less drag as possible coming from the one-way bearing in the clutch. This is a good way to confirm everything is straight (or as straight as possible).

Mario

[Rctintin]

The way I checked for the clutch stack to be vertical is by allowing the whole assembly to sit down on top of the clutch shoe. The bell sits on that big flat surface perfectly, and you can still feel the gap in the mesh. Now lift the assembly back up to where the frame bolts go into the bearing holder, and nip up the bolts and re check the amount of backlash. If it feels the same, your good to lock tight each bolt in turn, knowing that the whole assembly is fully vertical.

Mesh is a funny thing, and it is different in different models. You have to set it looser that you believe correct on the TDR (still a helical cut gear) because of the extra heat produced in the 2 stage gearing compared to the dinner plate size main gear on the E7/N9. If you don't, it WILL strip. My TDR has seen over 200 flights on that original main gear, and its been clocked at 124mph and its not a hot setup (2100 max HS)

I hope to get the N7 finished by next week end for the maiden. (Running my own company affords me little time so its a few hours late each night I get to build )

[Richard Rollins]

I had to do this shim for my YS91 srx to get everything lined up correct. Now its perfect.. It is easy to make and it took all four on each side to work ..
Rick

[mdu6]

I had to do this shim for my YS91 srx

No shims needed on my side for the YS91 SRX

1) Once the engine was losely mounted on the motor mount, I push the engine up (towards the clutch) while tightening it up.

2) Once this was done, I pulled the engine/motor mount (now secured together) towards the front of the heli, while tightening the motor mount to the frame.

This made for a 'perfect' gear mesh.

Mario

[1helimech]

I put a OS 91HZ PS in mine and I will be doing the engine shimming tonight, as it's a "little"  tight when I put the main shaft in.... Thanks for the great can shim solution  or "CSS "...As a point of reference how much shim did you all have to use ? 

[cyprusflyer]

I might be in the unique position to have tried both the OS105 and YS 91 Tareq in my N7.
As I initially posted in this thread 0.5mm of beer can shim (John Smiths beer BTW) for the OS 105.
The YS did not require any shims at all!
So we can infer that the engine specs were slightly out, mine is going like a train on that YS, outperforming any 700 size Nitro I have seen so far.

[1helimech]

I added 4 CSS shims per side and I now have no back lash and it runs with much less noise and way less rotational friction....All I can say is thanks for the shimming tip !!!   

[Chris Wall]

What size N9 shims are most that are having issues with the 105 and gear mesh using (it looks like the come in 0.5, 1.0, & 1.5)?  My gear mesh feels tighter than I would like to run, but not binding, basically no lash at all...