Unbalanced prop?

[sdg111]

Can an unbalanced prop cause cub to lunge left and low? Went flying today and it lasted all of five minutes. Hand launched and she flew left and low and crashed. Can't see anything obviously wrong but I have tinkered a lot with the prop but could it cause such drastic flight characteristics?

[renard80]

I'm wondering why you have "tinkered a lot with the prop".

FWIW, I have never balanced or "tinkered with" any of the props on my SC. I just whack 'em on and fly.

My purist friends howl in horror, saying it is essential to balance a new prop, shaving off microscopic amounts of plastic until it balances perfectly.

Rightly or wrongly (and no doubt wrongly!), I simply plough on regardless, with no discernible malfunction. I look upon the SC as a lumpy old friendly chunk of foam which gives me pleasure, not a finely-honed precision instrument.

I used to have your problem (veering sharply on take off before crashing to ground). I overcame it by increasing throttle steadily on take off (not too much throttle initially) and being alert to counteract any tendency to veer.

I do not rely entirely on throttle when taking off. I steadily increase acceleration, at the same time easing back slightly on the right stick to gently achieve lift. Works for me!

[flydiver]

If it was unbalanced to the point of one blade missing.....maybe.
But I suggest that in all likelihood is was something else.

[kenninny]

check to see if the servos are not reversed, and make sure the rudder is center.

[sdg111]

Thanks gents. stripped her down and checked everything last night and all seemed okay.

I've never had any problem getting her airborne before. I hand launched her and she veered left and stuggled to get up. It almost seems as if there was a lack of power. If it happens again I'm going to have to get that new motor.

Renard80, funny you should bring up the prop. Yes, I tinkered with it trying to get it finely balanced, yet as Fly says, it's unlikely this caused my problem.

However, I've stuck on a new one fresh out of the packet, so I'll see how it goes.

Will have to search the forum to see if the motor ever turns as if normal but doesn't generate the power required to give her lift. I'm assuming it's possible this could happen.....

[hounddog]

Motor offset angles ok? You have offset built in to both the firewall AND the stock gearbox as I am sure you are aware.

I once broke a fire wall without noticing and it did make it fly odd as the motor and gearbox were pulling away from the fuze under load.

[sdg111]

Thanks houndog. I fitted a new gearbox and propshaft last night and paid particular attention to the offset as I was re-fitting the cowl. It seemed okay and I certainly didn't notice a crack to the firewall.

Can I ask, where did your firewall break? Mine seems intact.

I'm a bit worried about hand lauching it next time in case it just dives into the ground again. I would prefer to launch from the ground as at least I could tell if there was sufficient power to become airborne before she's actually in the air.

[hounddog]

If there is a lack of power, try switching on your Tx, putting the throttle to full, then connecting the battery (take off the prop first).

It should run through it's beeps bar the arm beep.

Bring the throttle stick back to zero and the ESC should then arm and beep.

You have just reset your throttle range.

[sdg111]

Wow, that's all news to me. I've clearly missed something.

I've never heard a beep from my TX or ESC, ever. I'll try this when i get home though. Thanks for that, appreciate it.

Why do you need to take the prop off? Is it to maximise power?

[hounddog]

Ahh silly me, I'm thinking of the brushless motors in my other models.

I think the throttle range setting will still be valid though.

Going to stick a battery in my cub to see if it beeps. Back in a mo.....


Nope no beeps but I note the esc will not arm until the throttle has been backed off. So it will probably set the throttle range. high and low setting as normal.

Taking the prop off stops you having a trip to hospital if the prop takes a bite at you.

Some of my larger motors / props can do a surprising amount of damage including taking fingers clean off. I am always wary of a live prop with battery connected.

[sdg111]

Thanks hounddog. I shouldn't think my motor would start running more slowly for any reason, I guess they'd just stop working if there was a fault.

Can't fly again till later in the week but, fingers crossed, she'll fly okay, if not I've no idea what's wrong to be honest......

[hounddog]

What transmitter are you using?

A computer type has throttle range settings both up and down.

Maybe the upper range needs setting on the Tx if so?


Another thing to check is the rudder / tail. Mine came loose over time and wobbled side to side. This made it very difficult to trim out and the plane would wander either left or right.

I added some shims to the horizontal stabilizer and some clear tape to hold it in place ala my HZ T28 which you tape as standard.

This cured the trimming issue.

Keep at it you will find it in the end.

I guess if you feel like me you are finding it hard to keep enthusiastic due to this horrible weather?

I am absolutely sick of it.

[sdg111]

Thanks for all that. I'm using the standard TX, Dx4 if I recall, not at home so can't check.

Funny you should mention the tail because after the second minor crash yesterday the tail was out of shape when I recovered her. I've checked the screws and all tight but will check again.

Weather, although cold, has been okay for flying. Saturday and Sunday were very, very still up here, hence why I ventured out. I was more than a bit bemused that she wouldn't fly as that's never happened before.

I checked and double checked the wings, tail, trim etc, all rather frustrating when this happens but all part of flying i guess.


Did you tape the tail vertically, from bottom to top either side? Might try this if you think it's worth it.

[kenninny]

is your battery fully charged? connection ok? when it cold keep battery in a coat pocket until you fly lipos lose power faster when they are cold

[Filadelfos Hobby]

Apr 1, 2013 11:29:19 GMT 1 sdg111 said:

I shouldn't think my motor would start running more slowly for any reason, I guess they'd just stop working if there was a fault.

That's not true for a BRUSHED motor. A brushed motor will run slower & slower until eventually there's not enough RPM to provide the proper power. This is because the carbon brushes wear out. Back in the day, we used to open up the cans & replace the brushes. Brushed motors are so cheap now, there's no point to all that work... just swap out the motor.