TREX 450 SE main gear stripped

[Si Goodchild]

Guys,

My little GL450 (TREX 450 SE copy) went in again this afternoon and it wasn't even my fault! She was flying just great when from nowhere came a couple of tail twitches which then stopped and then 2-3 secs later she just went in from about 3 ft up. It seemed at first that the tail had somehow quit but it looks okay on inspection and the gyro/servo seem to be functioning. There was none of my earlier radio problems either as the rx light was properly illuminated.

My suspicion is that the maingear wasn't properly meshed because it is totally shredded all the way round with a really bad spot where I reckon the motor kept running after impact. When I fitted it about 5 LiPos ago I didn't do any sort of meshing checks or adjust the motor position as I assumed it was a straight one for one swap: perhaps I was wrong. There are the remnants of teeth all over the model which suggests that the gear was getting stripped in flight. Looking at the remains, the meshing doesn't seem miles out, but I've no other ideas.

Any advice on set-up when I do the rebuild? I've never had this problem before.

Si

[robgt]

Pinion should be about 2/3 of the way in to the main gear (mesh-wise). Not too tight, and not too loose.

Cheers,
Rob

[Tom Burgess]

Were you running a Trex 700 main gear?

[Si Goodchild]

Pinion should be about 2/3 of the way in to the main gear (mesh-wise). Not too tight, and not too loose.

So nearly fully engaged, but not quite, yes? Which is about where I thought it was. I will be extra careful when fitting the new gears.

[simoncalver]

hi mate
if your running a standard gl450 gear set chuck it in the bin and buy the trex 450 v2 set complete and chuck it in.
i had the same problem with mine and the trex gear set is much stronger

[robgt]

So nearly fully engaged, but not quite, yes?

You need a reasonable gap as the main gears are generally not perfectly round, so there needs to be room for the high spots of the gear to pass the pinion without binding the mesh too tight, while at the same time not being too far away to let the mesh get too loose on the low spots.

Too loose and you will strip the gears, too tight and you will reduce your flight time.

Cheers,
Rob

[Si Goodchild]

Many thanks guys. All the spares going in to the GL450 are Align TREX 450 SE V1 items so quality should improve with time. My plan was to buy the set of 3 main gears at £6 rather than 2 gears with one one-way bearing at £13 as that part should still be okay, but I note SimonCalver's comments: which parts specifically are you advising replacing, mate? (links to the fast-lad site would be great!)

When setting up I'll make sure that the gears run smoothly and freely all the way round but keep the gap to a bare minimum: the risk of a reduced flight time I can live with, piling in from way up I can't. I was fairly lucky this time that I was deliberately flying low and slow when she twitched and let go. Is adjusting the motor position the norm everytime you replace the main gear?

Si

[robgt]

Is adjusting the motor position the norm everytime you replace the main gear?

Not every time, once you get a decent mesh on the gears, it's likely to remain there for most gears, but it should be checked each time to be sure.

The other issue with running a gear mesh too tight (outside of reduced flight time) is that it is harder on your LiPos - which forms part of the reduced flight time comment. Just wanted you to be aware

I usually aim for about 1mm gap between pinion and main gear.
Cheers,
Rob

[simoncalver]

mate trust me and buy the £13 set the one way bearing in the gl is s**t. part no is HS1218-01 for white gears and -84 for blue,once you have the set you can then buy the pack of 3 gears as and when but i have only had to change mine after a huge crash into tarmac

[Si Goodchild]

Cheers, guys. I'll go with that.

1mm gap, though. Crikey, it's less than that now on the remains I have in front of me. Will keep you posted!

[Xige]

Reminds me to check out my gear mesh & motor is in tightly screwed in. Thanks for this. Ugh slap on the wrist for me I knew been missing something.

[Farmer Giles]

as already mentioned, once it's installed then look for the high spot and mesh it there. Then check your low spot to see if it's too far out. I have my high spot with almost no gap at all and it's meshed nicely at the low spot.

If you have trouble with one set of main gear try another set as I doubt they will always be the same. you could also try rotating them round the centre hub to try and find the truest position.

HTH

[Andy from Sandy]

I understsand what rob is saying in so far as most of these small main gears are not round.

You need to at least find the spot where the gap is going to be the smallest/tightest and then adjust the meshing so that there is a small amount of free play.

My little GL450 (TREX 450 SE copy) went in again this afternoon and it wasn't even my fault!

I didn't do any sort of meshing checks or adjust the motor position as I assumed it was a straight one for one swap

A slight contradiction with yourself there me-thinks.

[Si Goodchild]

fair point!

[shaun.e]

Bring it to work when its fixed Si, I'll give it the once over if you want?