Help - Gear Mesh

[cyprusflyer]

My gear mesh is a little tight between the pinion and main gear, that's with the clutch stack nicely centred in both planes and runs nice and free. When I install the main gear in that position it is tight. I can get it running nice if I ease the clutch stack bracket forward by a fraction, it goes from noisy to very quiet.
I really do not want to do that, the only way I see to get it perfect is to add about 0.3 - 0.5mm shims under the engine mounting lugs, moving the engine (OS105) slightly forward. Then I would have to reposition the fan shroud and the clutch stack should be right for a good mesh.
I have tried easing all  the motor mount to frame bolts and pushing forward, then tighten but no play here at all.
Any other way around this, where the heck do you get shims from to adjust??

[Chris Sexton]

The main gear is a zero/near zero lash joint but certainly shouldn't be tight and noisy. The need to shim will vary depending on motor manufacturer and their tolerances.

As for a source of shims, I have always turned to Ron Lund with HeliProz South. If you search on his site "shim" you will find many options for varying thickness and motor type.  I think you are not in america, I remember seeing your location on HeliFreak I think. I am not sure where you can get them internationally.

http://www.ronlund.com

[cyprusflyer]

Thanks Chris, thought it NOT a good idea to use washer size shims otherwise engine bearers have little support, my mesh is noisy with no backlash with clutch in the ideal position.
Turned to ExperienceRC, the have some Synergy N9 0.5mm shims in stock and ordered more stuff I needed so 1 or 2 pairs will do it. Fedex to Cyprus not that cheap!
The helical gears do need a tiny bit of backlash to allow for expansion when the pinion, clutch assy gets warmed up (which it will), my TDR certainly does.
So as I see it the stages are:

Guestimate a shim
Bolt engine in.
Centre clutch stack with no fore/aft bias.
Put main gear back in.
Make sure gear mesh is good, when happy then:
Remove clutch stack and check fan shroud
Re-assemble all, and life should be wonderful!

Bit more of trial and error with nitro engine installation!

[bmclaurin]

Just out of curiosity, what makes this particular pinion/main gear a zero/near zero lash joint? Not challenging, just trying to understand. My prior experience (admittedly not all that vast) with all my other helis is that the pinion/main gear joint needs a little space for when it heats up in normal operation.

The only way I see to adjust the mesh is to use an engine mount spacer/shim, as the OP suggested. My N7's mesh was just right without having to resort to a shim. I'm using the OS 105HZR.

Barry

[Chris Sexton]

I should start with a disclaimer. The below information is just my opinion. Everyone sets mesh differently.

I guess I should clarify what I mean by zero/near zero. It needs just ever so slight amount of room to accommodate expansion but not be loose enough to strip when cold. Sometimes when you tell someone you need a small amount of lash you get the "how much is small". I tell people to push the pinion up into the main gear until there is no play and back it off just ever so slight. You should almost not be able to hear the click when you check it.

And yes, the clutch stack bolts are slotted so you can shim your motor to fit and set proper mesh.  The kit does not come with shims as the amount/need will vary from one motor application to another.  Even finer point, I have now setup two of these with OS105, I didn't need shims on either, but I know someone who needed .5 shims on his OS105.

I will try and be better about explaining how I do things.

I agree, you don't want to use washers for shims on the motor. You need the full width of the motor mounts. If you search for motor mount shims you should find them easier. I am glad Cypress found some on ExperinceRC. I never thought to look through the old N9 parts!

[cyprusflyer]

The only heli I have seen that have little or no backlash at all is the Logo's, they have herringbone gears but even they expand and I leave a tiny bit of room.
All was well with mine until I screwed the motor down hard today to finalise the install, I notice that the fan shroud and clutch mounting position are at the rear most side of the elongated frame holes so makes sense and only solution is to move the engine forward and the rest will follow.
Can I suggest then that some 0.5mm shims are included in the kit, my build is basically on hold now for a week, for the sake of a 50 cent pair of shims!

[Rodney Kirstine]

The aluminum used in soda or beer cans makes pretty good shim stock and is really easy to cut.

[cyprusflyer]

Good tip Rodney, thanks never thought of that, probably cut with scissors and a hole punch, will give that a go :-)

[Rodney Kirstine]

You bet. The fact that you can cut it with scissors and use a hole punch is exactly what makes it so handy!

Sent from my MotoX via Tapatalk2

[Jean-Luc Bolduc]

Great tip Rodney. I did not need any shims either, but good to know, for those who may need some.
By the way, you only need a tiny movement to mesh properly. I don't think 0.30-0.50mm is enough to throw the whole stack out of alignment, imho.

[Rodney Kirstine]

Lol, 26 years as a design engineer and the best tip I've probably ever given is to drink a beer and use the can for shims...

Sent from my MotoX via Tapatalk2

[cyprusflyer]

I had a toast to Rodney last night, great tip and drank a can of beer 
This morning I cut off the ends of the can with scissors and also up the middle so I had a flat square of aluminium can.
I measured the thickness and it came out at 0.125mm as 4 thicknesses gave me 0.5mm I estimate I need.
So measured the mounts and they need to be 40 x 9 mm and the engine mount holes are 25mm apart.
Need to cut a dozen or so, so worth tooling up a but, used some MDF and marked lines at 0, 7.5, 32.5 and 40mm.
Cut 9mm strips as long as possible with a steel rule and Stanley knife, then cut to length and marked in pencil the motor screw hole lines. Then used my caliper to scribe a cross for hole centre at 4.5mm from the edge.

Now for the holes, tried a paper punch but too big and ragged, wanted 5mm hole so used a 5mm drill. I looked for some steel to drill, couldn't find any so thought what the heck, just drilled a 5mm hole in my pillar drill table, at least the hole will be bang on centre with the drill.
So now I use the pillar drill as a press/punch (POWER IS OFF DRILL NOT TURNING), just place the shim in the right place, press an inch and a perfect hole punched out    Yes mine has lasers which I calibrated to make easy positioning, suppose you could clamp something to position the shim against like a steel rule.

I used 4 each side as planned, torqued motor down and set up the clutch stack, the way I see it is judge by eye that the clutch bell is level with the shroud and see that the start shaft is at its free point. A slight lean will be felt by the start shaft rubbing.
Inserted the main gear on the shaft, eureka, now have 0.5mm approx gap, slight backlash, more or less on par with my E7.
So took apart, amazingly the fan shroud sat perfect and I had loosened the screws earlier, so locktighted up, re-assembled everything, all good to go 

Some photo's, extra servo is for Carbsmart, mixture tuning when engine is adjusted and broken in.
Also shows my Perfect Regulator Duo control switch, had to extend that cable by 7 cm, not for the light hearted.

[Rodney Kirstine]

Nice!

[Chris Sexton]

Wow what a great write up, thanks man!

[Rctintin]

This is the exact issue I have with my build. To be honest, at the cost of this kit, I'm not that happy that 2 pairs of .5mm shims could not be included in the kit!! Now I have to wait for delivery of the N9 shims I just found in stock, because I don't want 4 layers of shim under my motor.

The N5 and (IIRC) N5c come with shims. Matt, this needs to be addressed for the second batch of kits.