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How much vibration is too much?

TreeCrash

Junior Member
#1
Okay, I'm posting for a friend who is having trouble registering, so bear with me:

Hey guys,

I very recently got a Blade 450 3D and have been slowly learning to fly it. Unfortunately, about a week into it, I had a minor crash. I managed to tip the heli over and hit the blades against the ground(http://youtu.be/AQ4CSPNStho).

After the crash, I had a bent flybar (which I bent back) and some of the plastic coating (or is it paint?) on the wooden blades bubbled a bit and is cracked in one spot. The crack seems to be getting a little worse as time goes on.

As I've been doing hovering exercises, once in a while I notice that my training gear is vibrating quite a bit, indicating vibrations in the heli itself. I'm not sure if I would notice the vibrations if I didn't have the training gear attached, which sort of makes me think it's not so bad. However, I definitely notice the heli's nose drifting which makes me suspect that it's vibrating too much and throwing the gyro off. Is there a better way to really tell if the heli is vibrating too much? If the problem is vibration, then I assume it's because of the cracked coating. Should I try taping it and then re-balancing the blades?

Thanks!
 

Ak Flyer

Fly the wings off
Mentor
#2
That bent flybar is causing you problems. You can't bend them back. They aren't that much and come in a two pack, you definitely need to replace it.

You also should replace those blades. I've personally seen them leave the heli while hovering. One shot right between my legs and landed about 50 feet behind me.

Invest in a blade balancer and have a person at the hobby shop walk you through the process (assuming they know). Most shops that sell heli's have a heli guy, find him and have him show you.

You'll need to make sure that your new flybar is centered exactly and the blades are dead even as well (both distance and angle).

The vibration can surely cause the gyro to work improperly. A tail vibration can do the same. As you're hovering you should be able to see the tail clear as a bell. If it's blurry then you probably bent the tail shaft. (be careful when replacing it to make sure the belt doesn't get over twisted or twisted the wrong direction so the tail spins backwards).

Hope this helps some.

Also, here's a spot I found carbon blades for less than I was paying for wood ones. So far they are great. Balanced much easier and the cyclic is much crisper. You may want to wait until you get better at flying though as it does speed things up quite a bit.

http://www.ebay.com/itm/16078654085...X:IT&_trksid=p3984.m1439.l2649#ht_1655wt_1037
 

Ak Flyer

Fly the wings off
Mentor
#3
I also recommend flattening out your training gear so that you're not so elevated. That way your training gear will better help you prevent that from happening. Leave it up just a bit to absorb the shock from hard landings but that's too high to help tipping.

You also need to make sure your main shaft isn't bent and your feathering shaft. Very rarely do you get away without bending at least one shaft even in a minor crash such as that.
 

TreeCrash

Junior Member
#4
Thanks so much for the quick response. I was afraid he bent something, and the surface damage to the blades made me nervous. Looks like we will be going shopping. The bird seemed to perform fine, but it does have that drift. I don't know how adjustable that training gear is... it is a set from Blade and seems to have a fairly rigid connection in the center. I will have to see if we can modify it. I will see about the shafts, we may be able to check them on the lathe if I can ever convince him to tear the poor bird apart to get at them :p
 

Ak Flyer

Fly the wings off
Mentor
#5
No problem at all, I'm happy to help.

Take the blades off and spin the rotor head, most of the time a bent main shaft will be plainly evident. You should be able to see a smooth rotation all the way up to full speed. (not that you need to spin it full speed)

Take an allen wrench of the appropriate size and turn the feathering shaft in the center of the blade grip. If it's bent you will see it right away. If you do remove the shafts, just roll them across a perfectly flat surface (piece of glass is ideal) and they will either roll perfectly or you'll see it right away. Wouldn't need to put them in a lathe.

If you do remove the shafts, the main shaft is easy. Just remove the ball links from the servos, remove the jesus bolt from the rotor head and the whole thing will pop off. Then you can remove the bolt from the main gear one way bearing hub and the shaft will come out. Notice that one side is longer than the other, I believe that the 450 has a built in hub where the 400 had a removable stop. Anyway, I think it's the short side that goes down the frame, either way it's the side long enough that the stop rests on the top of the bearing and lines up with the main gear hole.

If you remove the feathering shaft, then you need to pay very close attention to the order of the bearings, races, spacers and o-rings (or dampers). It's very important that these are put back correctly. The spacers determine the tension on the dampers which determines the flexibility in your rotor head. Tighter makes for crisper response (harder durometer dampers as well) and a softer setup will create a softer and more forgiving head.
 

TreeCrash

Junior Member
#6
We did spin it up without the blades and it looked okay... but the main gear seemed to wobble at low speeds (I will post a video at some point). I doubt that is normal. We took the main shaft out the next day and did find it ever so slightly bent. It was hard to tell, but slowly rolling it on the counter reviled a little bit of bend. There is a stopper/step in the middle of the shaft that makes it a bit hard to roll... but I'm pretty sure there was a bend. There will be a new one going in as soon as we get it. We didn't check the feathering shaft though.
 

TreeCrash

Junior Member
#7
Just a quick update. We replaced the mainshaft and the flybar (which actually turned out to be quite a pain to replace). Checked the feathering shaft by turning it in the blade grip and it seemed fine. It is hard to tell if it flies better because it really wasn't that bad to start with. I'm sure it helps though. Here are the maintenance videos I made.
Spin up without blades: http://youtu.be/GmZMiyWcqH8
Removing the main shaft: http://youtu.be/2PJe0qP3sFo

I plan on making one of the flybar replacement too.

Edit: Flybar replacement is up: http://youtu.be/POqHaTQeUiw
 
Last edited:

Dark_fox

Junior Member
#8
Just a quick reference for people looking into this at a later date, a good way to figure out if any 'true spinning' part is bent is to roll it on a flat piece of glass. Generally glass holds a perfect straightness irregardless of temperature (if its flat glass that is) and thus will give you an easier to see indication if something is bent.
 
#9
I've discovered that my vibration seems to be worse when the engine is cold. After riding for a little while it seems to improve. I also hit a bump with my wife on the back and the vibration changed. I'm hoping either it's the mount or timing or both. Going to have my shop check them when I get the fluids changed.....Click here

Regards,
Berry