450 450 Dominator Build

[PLANETGETLOW]

As some of you may or may not know I've been building this 450l for about 2 weeks and finally got it assembled. Upon spoiling it up I noticed a bad wobble and my gyro and Servo reversed after fixing the gyro and servo the head was still wobbling very severe which caused a main Blade to boom strike.

I then pulled the head off and spooled it up only to notice that the main shaft was bent. Please keep in mind that this helicopter has never been hovered so this main shaft was bent right from the manufacturer. I went and purchased another main shaft that had a locking bearing which was nice because it allowed me to make a tighter tolerance between the top of the frame on main gear so there is maybe 1mm of slack.

I then put the head back on and took it for a test hover/spool up, which it hovered spooled up and hovered fine but when it's spooled down the vibration came back almost to the extent of causing a blade to ground strike. Maybe i came off ofmthe throttle too fast?

This prompted me to bring the helicopter back in and pull the head completely apart and inspect the Feathering spindle and the rest of the components. This prompted me to bring the helicopter back in and pull the head completely apart and inspect the feather and spend all and the rest of the components. When I finally got it all torn apart the feathering shaft was fine it was not bent however I forgot to Lube the bearings.

I now have it all back together and did a bench tests pool up everything seemed fine so I went ahead and put the main blades on and I'm letting the locktite setup before i try it again.

In the meantime I've been reading that the main shafts on these for 450s are very fragile has anybody else experience this? I've read to the extent that a hard landing could even cause a been making shaft?

Would coming off of the throttle too fast cause a bad wobble? Has anybody else had main shaft issues?

 

[Smoggie]

It's a good while since I flew A trex 450 but i never had any particular issues with a bent main shaft. I think i did bend one but only after a crash, which is to be expected.

Are you flying normal mode so that when you go to throttle down using the collective stick you are also adding lots of negative pitch?.. if so then that's probably the reason for the wobble on slowdown. Much better to keep the pitch close to zero and cut power with throttle hold.

 

[Tony]

It was not the shaft that caused the strike, it was the blades being too loose.

There should have been shims with the proper shaft with the moulded in collar to reduce the play. Those collars fail all the time which is why they got away from them.

The shafts are quite hard, but a strike on the tail boom, enough to destroy blades will destroy a shaft.

and no, spooling down too quickly will not cause issues unless your blades are still way too loose.

 

[Smoggie]

Tony, good call on the blade grips being too loose (and/or uneven). Also on the play on the shaft, there should be none when correct shims are used.

I guess that it's not inconceivable for a shaft to be bend right out of the box but it is highly unusual. If you had a boom strike then more likely it got bent in the strike and the wobble was due to other factors (like poorly adjusted blade grips for instance)

 

[PLANETGETLOW]

Appreciate the feedback. Blades are now tighened as you mentioned before. First test hover coming soon.

 

[Smoggie]

The usual test for blade grip tightness is that the grips should be 'just' tight enough so that if you hold the heli on it's side with the blades horizontal they should not fall. But if you give the heli a slight jerk they should both drop equally. Getting them evenly tightened is key.

 

[PLANETGETLOW]

The usual test for blade grip tightness is that the grips should be 'just' tight enough so that if you hold the heli on it's side with the blades horizontal they should not fall. But if you give the heli a slight jerk they should both drop equally. Getting them evenly tightened is key.

Thats what Tony was sayin, i have them like that now. He also has me thinking, as much as I want to go test this im wondering if i shouldnt just replace the main shaft with a stock one.

I boought a complete 450L airframe that came in today plus theres a ton of extra parts and one of them is a stock main shaft.

 

[Tony]

I only use the stock shaft. It's all I have used since that style came out. If you can't get all the play out you can loosen the main blocks and squeeze them together or push them apart to adjust the play.

 

[PLANETGETLOW]

I ended up putting a stock shaft back in. It has no play now. Head feels good, tail looks good, hopefully tomorrow it will perform good. Gonna go tbrough the Ikon setup again.

Im struggling getting +12 and -12 pitch, always have. On one blade it reads 12.4 and on the other -11. Tracking is good but cant get it to be equal. Ive tried adjusting the top two links on the head and it will just go out of track. A guy at Horizon Hobby said to only read pitch on one blade????

 

[Tony]

Did you happen to follow my digital pitch gauge video? In there I show you how to set the blade pitch properly with the digital gauge. You have to check it without moving the helicopter, and on the same side of the heli.

 

[PLANETGETLOW]

Yep, followed it exactly

 

[Smoggie]

It's not unusual to have slightly different + and - pitch travel. It may be caused by not having you servo arms precisely leveled at mid stick/zero pitch (check them). But it can also be a 'quirk' of the servo/swash linkage geometry. If the servo arms are dead on level at zero pitch and you still have unequal travel you can fix it by slightly adjusting the travel range in your Tx setup, a few % should do it.

 

[PLANETGETLOW]

It's not unusual to have slightly different + and - pitch travel. It may be caused by not having you servo arms precisely leveled at mid stick/zero pitch (check them). But it can also be a 'quirk' of the servo/swash linkage geometry. If the servo arms are dead on level at zero pitch and you still have unequal travel you can fix it by slightly adjusting the travel range in your Tx setup, a few % should do it.

Servos are dead leveled. Linkage is adjusted accordingly. Ill try the travel range

 

[trainrider06]

What type servo's are you running? As Steve said during travel if you have one that's lazy, weak, or jittery that could cause problems. I had a brand new DS 430 servo, failing on me that I had to replace right off because it was slow and jittery.

 

[PLANETGETLOW]

What type servo's are you running? As Steve said during travel if you have one that's lazy, weak, or jittery that could cause problems. I had a brand new DS 430 servo, failing on me that I had to replace right off because it was slow and jittery.

They are the stock servos that came with the kit. I did what Smoggie said regarding travel and i was able to get +12 and -12 on the pitch. This of course changed the settings in the Ikon software but I dont see any way else?

 

[trainrider06]

What do you mean "changed the settings in the Ikon"?
I have the DS430 Align servo's in both my 450 PRo and 450L heli's

 

[PLANETGETLOW]

When i change the travel adjust in the radio get correct pitch it changes the servo travel endpoints in the Ikon software, not allt but slightly more than 100

I use Ikon on all of my built helis. The Blade 270cfx is the only heli I have with a Beastx

 

[trainrider06]

as long as you don't have any buzzing on the servo's at max end points you should be ok. So after you redid the servo pitch and range settings did you do the servo max end put range check?

 

[PLANETGETLOW]

Yea setup seems fine, much much easier on my 500.

While doing a bench test spool up i noticed that the vibration seems to be tied to head speed. Right around 1\4 stick it wobbles but when i raise the head speed to 1\2 throttle it immediately goes away. Using throttle hold works and shut it down quick. If not it will wobble on spool down. So confused

 

[trainrider06]

You should be good then, what servo's do you have?