5.5 problem with crown gear

[Temptation]

Quick question for guys flying the 5.5
Are you guys having problems with eating up the teeth on the crown gear?
I have a new 5.5 and i can see that the crown gear has bad ware in it. Im going to need a new one to fly again but they are back ordered. Is this a problem with the 5.5?

[ZeniethLily]

No, check your alignment of the bevel gear - it is probably too close to the crown gear. You can raise it a little to see if it helps.

[Temptation]

Thanks, i will try it again.

[GimpyGolden]

+1.
What I like to do is pull the blades, slightly loosen the 4 screws for the front TT bearing support bearing as well as the 4 through bolts for the boom clamps and run the machine up on the bench. This kind of lets everything settle where it wants to be.
Recheck lash, should have a little rock on lowest spot of gear 9if there is one) and then tighten everything back up.

Do a few flights and check lash and wear pattern on gear. Adjust accordingly.
On a new build I would check after every ten or so flights for about the first thirty and after that just go fly it.

[Temptation]

Thanks, I just got a new gear order and it should be on its way soon. I willl try and pay closer attention to the gear mesh this time. I thought i had it right the first time, but evidently i didn't. The thing is, looking at the gear and how it wore, i can't tell if it was too tight or too lose. .

We will see how it goes this time.

[ZeniethLily]

You'll have to look at the mesh directly, and spin the rotor head by hand - it shouldn't cog, but continue spinning a little more. There should be a very slight gap between the gears, which gives the little bit of rock at the bottom of the gear.

[Temptation]

Ok finally got some new parts and a day off from work to change the gear. I took out the old gear and can see high and low spots. This made me want to check the new gear. The new gears are machined to exact at the center of crown gear but at the edges are as much as a .48 off at the outside edge of the gear. The crown is perfectly flat and smooth. So when cutting the crown the machine work is off at the outside edge in thickness. When i place new gear into the heli you can see this when i spin the head. The bottom of the crown is perfect but you can see the crown gear teeth rise and fall as it rotates. What i did for now is to find and mark the highest spot and set the gear mesh as tight as possible for the highest point. I'm hoping this will work but i don't like the backlash i get at the low spots.

If you guys have any suggestions, i am open.
thanks.

[Temptation]

Update, Ok after calling kds, i used some shims to set the gear mesh right and backed out on the 4 screws holding front drive shaft mount. Rotated the head as i tighten up the 4 screws for the front drive shaft mount and once done i checked the black lash. Now she is right even with some high spots. After doing some test flights, she is very smooth and all gears look good. this is a very quiet heli. I'm very happy with how she feels, sounds and the build quality is top notch. I can see that i had to much back lash the first time around. Yes the crown gear has some high spots but from a high to a low spot we are talking only at the edge of the teeth and it was .48 mm off. With all the angles in this one gear its understandable. I used some shims from a gas engine. They were .01mm each. I used 4 of them with the stock one as well. This gave me close to a 1mm shim from the bottom bearing block. Everything is so smooth now.

[Larryu]

Thanks for sharing. I've been following along but bought mine used so I haven't had to deal with the crown gear yet as a result couldn't be of help. But this post will help me down the road.

[Temptation]

Kds was very helpful in all this. Just keep in mind that you want to keep the gear mesh tight without any binding. In other words, very little back lash but spin freely. The reason for taking the boom lose and the 4 screws on the front drive shaft mount was so the correct height for the crown could be set first and locked down to ensure you dont bind any of the bearings for the tail boom and front drive shaft mount bearing.
I was told that some people would loosen up the tail boom and push down on the front drive shaft mount then lock the screws down. But this would put to much pressure on the bearings and they would fail down the road.

By setting the height first, you spin the head to allow the gears to set and then lock front drive shaft mount and then the boom down. This keeps the bearings lined up for longer life.

[fishfiend]

I found that on the 5.5 the front drive shaft is made from aluminium, and will bend in a crash, whereas the 7.2 one is made from steel and is very hard to bend..luckily the 7.2 drive shaft fit perfectly in the 5.5..I was getting high/low spots on my crown gear mesh, it turns out the front drive shaft was bent...worth checking if you're having problems.

[Temptation]

No, she is flying so good now. She is smooth as butter.
While at Ircha I had some KDS teem guys look her over. They said she looks good and were very impressed with how smooth and we'll she flew. One guy said mine was flying better then his. I put her in a hover and did a hands free hover and showed him. No shakes or drifts. Very solid. Now that she is setup and I have had some time to play with my setup, I am more them happy with this bird. I changed the blades to some edge 553mm and that made a big difference in pop. I changed my p and I gain, and I am loving this bird. Quiet and smooth all the way! Only problem now is the kds canopy quick release won't stay locked on.

[ZeniethLily]

i swapped out of the quick release pins because they kept breaking - was actually going to get some from rcbooya but the shipping is just too expensive for me to justify it

[Temptation]

I just ordered some rcbooya, I got some for my x7 at ircha and they worked great. I didn't get any for the agile because I already had the KDS ones..... So I paid more to get rcbooya shipped. But they are better.

[Larryu]

Temptation could I get a little clarification did you put the shims between the main gear and the crown gear or under the whole assembly? Also, I bought one of the 7.2 front drive shafts and fishfiend is correct it is the same part made out of steal. I got the KDS quick mounts also and three of the four stay locked the fourth one would come loose when I pulled on it. I played with that one a little off the helicopter and now it stays on but I always pull on them good after I put the canopy on. I don’t see them lasting a long time so I’ll probably get a set of the rcbooya’s hopefully the hole size in the canopy is the same.

[Temptation]

I just got some rcbooya to try. Ill let you know tomorrow if the fit the same hole.

On page 15 in the manual look at the washer (5) part # (ka-55-076). It says " this washer is used for adjusting the tightness of the gear mesh".

When the bearings are pressed in, they could be a little off, so shims or washers may need to be added here. Check it first before you add any. Not every heli will need this done. 9.2 x 13.8 x 0.5 is the size of the stock washer but if you need to add some, you can use a different size shim/s so long as the stock washer is on the bottom.
I believe my shims are 9.5 x 12 x 0.1 (i added 4)
Again if you add any of a different size place the stock one on the bottom.

[Temptation]

Ok i test fit the rcbooya canopy mounts in the same hole as the kds quick release canopy mounts. The kds hole is a little bit bigger but the rcbooya still work just fine. I'm going to run the rcbooya from now on.

On the rear mounts there is a long treaded rod for the tail boom that the rcbooya attached to. I had to cut a very small amount of this thread so the quick release would work.

[Larryu]

Great I'll probably order some soon. The KDS ones are getting harder to get them to lock on.
I'm having trouble finding a shim what will work. I have some 10mm ones but I think they'll be to big and I couldn't find any 9mm I was going to take a Dremel and open the hole up. I may just live with it it's not bad just a little loose.

[ZeniethLily]

that is great news! I would love to get some, but the shipping costs as much as the product itself I'll probably have to get it the next time i am stateside

[Temptation]

Originally Posted by Larryu

Great I'll probably order some soon. The KDS ones are getting harder to get them to lock on.
I'm having trouble finding a shim what will work. I have some 10mm ones but I think they'll be to big and I couldn't find any 9mm I was going to take a Dremel and open the hole up. I may just live with it it's not bad just a little loose.

You can try this part number,

KA-55-076
Keep in mind that, not every kit will need shims.