Crown gear mesh

[marked23]

How tight should the gear mesh be between the crown gear and the tail pinion? Is there a way to adjust this mesh?

If I sit still, wiggle the gears, and watch closely, I can see just a bit of space/movement between the gears. It looks like it's pretty good, but here's why I'm asking:

The tube drive input pinion seems to be about .5mm forward of where it should be. If I move the pinion back to where it is centered on the crown gear, this will loosen my gear mesh. Then what do I do? I don't have any of the extra shims in there to take out. (just the one .5mm) Can I sand down the edge of that brass sleve?

I'm new to building MA stuff.

-Mark

[capebob]

Mark,

It sounds like your gear mesh is ok and it is also ok to have the tail drive pinion a little off center to achieve proper mesh although the pinion in the center is the ideal. I would check section II step 1 F to be sure that the lower main bearing block is not installed upside down.

Bob

[marked23]

Well, I'm going to move the tail drive pinion to center on the crown gear. And when I do that, it's definately going to be too loose. [I need to pull out the pinion to polish it anyway.]

How can I make the crown gear go up higher to meet the new location of the pinion? I was thinking that I could sand a bit (maybe .25mm) off of the brass sleeve.

Thank you,

-Mark

[cdrking]

I just went through this whole mess after chipping a tooth off the crown gear. I put a new gear in and the mesh wasn't just right and I trashed another gear.

Got some advise from others and some said sand the brass sleeve. Some said use a piece of paper to set mesh correctly.

One guy told me throw the shim AND the brass sleeve away, center the bevel gear on the crown gear and pull up on the mast, (just barely held the weight of the heli) and tighten the lower split collar. Then push down on the main shaft and move the upper split collar in place and tighten it.

This was quick and painless and it has been going strong for about 50 flights now. I just checked the gear tonight and there's no problems. It's running great.

Jeff

[Shannon Davis]

I sanded the brass collar. The ION does not even come w/ the sleeve or shims. Not sure of the actual "setup" but I wouuld go w/ the "Ole Piece Of Paper In The Gears Trick"--then tighten the collar.

[cdrking]

What's the purpose of the brass sleeve?

Jeff

[angelob]

I did the same thing cdrking did - got rid of brass sleeve, pull up on mast and tighten collars. I know I read about it somewhere, but don't remember where. I have some 70 odd flights on my fury and gear looks great.

Angelo

[Russ McC]

Yes remove the sleeve and shims. These are only there to set the mesh and it is much easer with out them. I don’t recommend using any paper just slide it up tell it touches and snug the collar, rotate it and if it is free with no or very little lash then position the top collar and your good to go. I believe this is the excepted method at Min Air now also.

[marked23]

How should the mesh feel? I know Russ just described it, but I'm wondering if it's ok to have just a bit of 'notchy' feel. Or is that too tight?

-Mark

[fitenfyr]

Mark,
Notchy is good if the gear is brand new. If not it is too tight IMO.
I have the sleeve and the shim in mine, but use the method that Russ and Jeff describe.
Just visually check to make sure the gear is centered. If so then it is good. I also use the piece of paper in there when setting mine.
Black art that gear mesh is.......:D
Worked great till the last crash. :D ION is still going strong though. :D

[Dr.Ben]

The collar becomes a liability if it "sets" the mesh too loose. In all of the models that I've built since the consatnt drives were released and esp WRT the Furys, I try to set the mesh on the ring gear at the point where there is either zero lash or barely detectable on the LOW point on the gear. You will feel the mesh bump on the high side, but that point quickly wears off after a few flights. The resulting mesh is virtually lash free, yet has no binding. If you listen closely to a model that has a bit of lash in the front tail tranny in flight and esp. in hover, you can hear it with the motor pulses. It can and does feed back into the tail and shows as a wiggle. The tail sits a lot better with the lash is as little as possible. This all said, if you fly a few flights and still have some noticeable bind, add a shim or reset the collars.

Polishing the bevel gear is definately a good thing to do. If you happen upon one with a lot of the little "bumps" from the hardening process, it'll eat your ring gear in short order.

Ben Minor

[Knud Pedersen DENMARK]

Did a search on ”crone gear mesh”, and find this ”old tropic”

My fury makes a lot of noise, especially in ildup2 – I think it is because of to much “freeplay” between the cronegear and the bevel.

I can see there are more ways to fix this gearmesh.
---------------------------------------------------
1.
Remove the brass tube, and the shims.
And simply get the right mesh, by pulling up in the mast, and tightening the collar.
- This will mean that the Teflon ring under the crone must take the “pressure” - or (?)
---------------------------------------------------
2.
Sand the brasstupe, (and place more shims under the cronegear ?)
---------------------------------------------------

I can desired witch solution I should go for… :( ,,,whats most commen?

Then I can see that Dr.Ben, set the mesh at the “lowerst point on the crone”.
Is that good ? mmmh I think I will try that….

Dr. Ben, what do you mean by
“…lash in the front tail tranny…..” is that between the cronegear and the bevel????

ChopperKnud

[DavidH]

The brass tube spacer for the main shaft does not come in the kits anymore I don't believe. Most pilots just hold the heli by the rotor head. And then tighten the lower collar on the main shaft. Once the lower collar is tightened. Then suspend the weight of the heli by holding some pliers under the upper collar. Then tighten the upper collar against the upper bearing block. That is the way I set the gear mesh on the crown gear. This is with no brass spacer installed on the main shaft.

David

[Knud Pedersen DENMARK]

Hi DavidH

Are you saying that the Brasstube no longer is in the new kits ?? :?:

If so, I properly don´t have to be worried, about removing the brasstube.

I will remove the brasstube, and set the gearmesh with nearly no freeplay at the lowerst place on the cronegear.


ChopperKnud

[DavidH]

Knud,
I am not positive. But I believe I have heard Tim say that they do not put the brass tube spacer in the kits now. I think they have been in the kits for over a year now.

I will remove the brasstube, and set the gearmesh with nearly no freeplay at the lowerst place on the cronegear.


That is exactly what you want to do. Like I stated above. I hold the heli by the rotor head with the main shaft collars loose. I then give the heli a downward shake.
I then push the lower collar against the lower bearing block and tighten it up. I then support the weight of the heli by the upper collar by holding some pliers under it. I then tighten the upper collar against the upper bearing block. That is how I have been doing it for several years.

David

[MinAirChris]

David is correct, we no longer put that brass spacer in the kits.

Chris

[Dr.Ben]

Knud,

1) Lash on the front tranny = bevel/crown gear to ring gear mesh

2) Yes, I mesh on the low spot. If you mesh against the high spot, the resulting overall gear mesh is too loose.

Ben Minor

[EricLarson]

Ben is right on the money. No lash, but there should not be much resistance either. Too tight will result in a bit of melting of the crown gear material which can lead to problems. Just set it with minimum backlash and you will be fine.

One other point to mention that is OFTEN overlooked in the placement of the pinion of the crown gear. With the power we have you NEED to have that centered. I often see 10-20% of the crown gear that is not meshed with the pinion as the pinion is in the wrong place. Look very closely at the gear placement forward / aft and adjust so you get max contact of the pinion to crown gear. That will also help a lot.

Rough pinions are also a major problem. If yours in not smooth, you need to polish it.

[j2m]

Any tips on how to polish the pinion? I have just done a brand new pinion with 1200 grade wet & dry abrasive paper pinched between my fingertips. The teeth look good now but it took ages and I'm wondering if there's a smarter way? Also, should you polish both faces of each tooth or just the driven side?

[EricLarson]

I have used a little polishing brush on a dremel. Worked well. The paper works too, but ya it takes a bit of work :D

[Knud Pedersen DENMARK]

Hi Eric, regarding the gear mesh:
I did the gearmesh as DavidH described:

I hold the heli by the rotor head with the main shaft collars loose. I then give the heli a downward shake.
I then push the lower collar against the lower bearing block and tighten it up. I then support the weight of the heli by the upper collar by holding some pliers under it. I then tighten the upper collar against the upper bearing block. That is how I have been doing it for several years

Do you do it the same way, or do you think that this gives to little mesh?

ChopperKnud

[EricLarson]

Should be very close. I rotate the head afterward and make sure it does not have a lot of resistance. Small amount of resistance is fine. David's method should get you very close.

Just get it close to 0 backlash without grinding or anything when you rotate the head. It is not really that critical but placement of the pinion also is important.

If you chew up gears with little backlash, then there is something else wrong.

Most likely a slipping collar on the main shaft, rough pinion, or gyro gain set way too high.

later,

[DavidH]

Knud,
Setting the mesh the way I have been doing. The mesh is pretty much set by the weight of the heli. I only give the jerk on the heli to make sure the main shaft is set properly. Then I just tighten the lower collar with it resting on top on the lower bearing block. 95% of the time the crown gear will turn freely. I have very little backlash as Eric has mentioned. That is what you want. The crown gear will wear some after the first few flights if it is new. I then go back and check and make sure there is not too much back lash then. I keep the backlash as little as possible and the system still work freely.

David