Hello RCUniversers!

Here is my story...
I bought a Kyosho Trainer 40 a month or so back. Had to wait a looong time till my engine (O.S. LA .46) arrived.
But if finally did, yay!
So I mounted the engine in the plane today together with a Dubro spinner and a 11x6 Master airscrew prop.
A friend of mine came over to help me out with the break-in of the engine.
After a couple of hits with the starter to engine came to life, and so did the plane! The whole thing started to vibrate a LOT.
We turned the engine off and started to look for loose screws and nuts, but they where all well secured. We even moved the
tank to the outside in case it was laying against the side of the plane, and thereby causing these vibrations.
Fired up the engine again, and the plane started to shake around like it had Super Parkinsons. We opened the throttle more and
the vibrations went away. Again we turned it off and looked around, finding nothing, no loose wood, no loose screws or servos or
batterypack. We decided to call it a day and give it another shot tomorrow.

I know this is a tough question since you more or less "have to be there" to see and hear the vibrations. Seems like its coming from
the front of the plane. Didn't see any cracks in the engine-mount nor in the firewall.

But anyone have any similar experiences or any good advice to share?

Did you balance the prop ? If you did balance it (or after you balance it) if it still vibrates, try running it without the spinner. Something is out of balance, and the primary culprit is the prop with the secondary culprit being the spinner.

Hope this helps.

first but a 10x8 prop!

it could just be the OS rattle!!

Campy: Nope haven't balanced the prop. I was told that you only had to bother with balancing props in larger planes. But I will try that tomorrow, and I'll try a new spinner as well.

volkan: 10x8 prop? Why? the manual recommends a 11x6 during running-in and normal use? =/

By 'larger planes' they likely meant larger than 1/2a. Once you get into 9" and larger diameter props, they need to be balanced. Smaller props can and in a perfect world should be balanced as well, but are sometimes extremely difficult to do because of the infinitesimal amounts of weight to remove or add to balance.

i also have a 46la in a super air, i had a 11-6, but you dont get the revs,
10-8, will make your plane faster, however, i think again, and a 11-6 for a trainer is ok!!
see what the general opion at your club is.

My question would be is the back blate of the spinner a tight fit around the crank shaft? Does the spinner come with bushings or do you ream it out to the correct size? Most new porps are close enough to balance that it sould not shake like your is. Sounds like a spinner issue or worse, a bent crank shaft!!![X(]

Well, this spinner is fishy. I wouldn't be that suprised its thats the one causing these problems.
I've talked to a couple of people and no one have never even heard of this kind of construction.
I'll try too explain, but since english isn't my mothertongue there will probably be a lot of "thingys"
and "whatnots" instead of the correct technical term

The spinner comes with a back plate, front cone, two screws and four plastic bushings (?)
-> ( http://www2.gpmd.com/image/d/dubq3680.jpg )
You fit one of the bushings on the crank shaft (four different inner diameter-sizes so you won't have to drill the back plate)
and then press the backplate on to this bushing, then comes the propeller (which is tight I have to screw mine on, is that good or bad?)
then the spacer, then screw the nut tight. And then you press and screw the cone on to the backplate.


I'll report back tomorrow if the change of spinner and prop proved to be the solution to my problem. Thanks for the tips

Hi Zeno,

Try one thing at a time so you will know what improves the situation. I agree with the others that it is most likely the spinner.

Remove the spinner and try this first. If it still vibrates balance the prop and try again. If it still vibrates after removing the spinner and balancing the prop it sounds like the crankshaft.

Good Luck,
Colin

Your spinner sounds like one of a normal variety to me. (I've used them and they're usually fine.)I have a problem with this statement, and many of the others.

zeno was correct when he said, "I know this is a tough question since you more or less "have to be there" to see and hear the vibrations." There is a GOOD chance that the vibrations that your seeing are NORMAL! All of these engines vibrate to some degree, and whether or not your's vibrates too much is a question that we can't really answer here.

I never balance props under about 12 inch diameter anymore, and my engines don't shake any more than the guy on the flight line next to me that goes to the trouble. It MAY make a difference with your's, I just wouldn't count on (or fixate on) finding a problem.

Balance the prop and change the spinner if you wish, but if that doesn't make things better, then chances are good it's normal vibration.

Welcome to RCU and HAVE FUN!
Dennis-

just curious but... how do you know that it is vibrating a lot? If you are running it a very low idle or 4-stroking it (which I know, guys, will kill the engine), it may vibrate a lot. I would suggest the best solution is always just to bring it to the local field and let someone help you out with it. The spinner is not a problem unless you are using the wrong bushing. The prop is not a problem unless there is something very wrong with the balance say an electronic tag or something.

Ok, today we checked the balance on the propeller and it was just fine by default. We changed the spinner
and fired up the engine again, the plane was still rattling like Parkinson on LSD. We adjusted the idle a bit
to get rid of the worst vibrations, perhaps this will prove to be set to high and cause problems during landings,
time will tell.

I'm not that experienced when it comes to planes (used to be racing 1:10 track a
couple of years ago, so I'm not a total newbie when it comes to the hobby ). I can only compare this
trainer to another trainer which I've been learning on for a couple of months. Can't remember that
one vibrating like this one. Of course its pretty much impossible to get the plane total vibration-free.
But comparing these two, the Kyosho is vibrating a lot during lower rpm.

Anyways, gonna get the plane up in the air this friday. If it flies well I'm just gonna try and ignore it and keep
having fun with it in the air

Woho!
Reporting in again in case someone else run into the same problems as I.
Managed to remove the annoying vibrations! So now I got !QUOT!standard-vibrations!QUOT! only

I wrote that I did use a 11x6 Master Airscrew. The first time when I attached the prop it was
very very tight so I screw it on (hurt my poor fingers ).
Next time when we changed the spinner I got sick and tired of screwing the thing on, so I drilled
a larger hole in the prop so it would just slide on, you would still have to push it on, so it was quite tight still.
But there was still vibrations.

So today I visited the local hobby store, hoping to buy a new fresh Kyosho prop, just to change (read elsewhere
on this great forum that someone else also had vibrations while using Master Airscrew props, that he changed
and the vibrations was gone) and see what would happen. I went there and explained my problems
and the guy showed me his propstand and guess what... It was full of Master Airscrews... I did feel very silly
since I was kind of blaming the brand a little bit (I have to give it to them though, they make the best looking
props, and since they've been around for so long there shouldn't really be any trouble with them).
So I bought a new one, went down in size to 10x6. But he also had a small stand with some APC-props,
the guy running the store said something like !QUOT!Well.. They're great, doesn't make much noise and you'll get more force
from those, but they are more expensive.!QUOT!, and the way he said it I felt like it was gonna cost me a brick of gold.
The Master Airscrew cost about $5 and the APC around $6.7, so well.. ehr.. I don't know why he said it like that
Oh yeah, when I told him about my problem he asked if I'd drilled the prop, when I told him !QUOT!yes!QUOT! he just started shaking his
head telling me that was a big, big no-no, and that was the reason for the vibrations (I did screw it on the first time dammit!).
Oh well, I went back home and pulled out the APC, it slid on perfectly no need for ... drilling...
I did have to carve A LOT on the spinner to make it fit though, but the guy at the store warned me about this though.
Finally it went on. I ran out with my gear and fired the engine up (side note: I just had to try starting the engine by giving the spinner
a twist, I thought it looked really neat when someone did that in an engine-review-video. But I just couldn't get that to work...)
The engine started up and... voila! Normal vibrations!
I taxed the plane around screaming !QUOT!Yippie-yay-yay!!QUOT! inside. Didn't dare to put her up, too many lamp posts and trees around the place.


Sooo... What did I learn from all this? Don't be a cheap-ass? Don't drill the props? Well, maybe, I don't know. Ok, I'll try and stay away from
drilling the prop, perhaps that was it, I don't know. But I'll keep buying APC-props.
And I also want to clear it out that I'm NOT telling you that Master Airscrew props are crap!
No siree. They might work great, they sure look great. Its probably just me



... and no. I can never keep things short...

zeno, glad to hear you got it all sorted.

Please, but I beg to differ. MAS props aren't "crap". If you need to enlarge the hole in a propeller, please, by all means, use a prop reamer. They're intended for the job and will keep the hole in the same place.

The main difficulty with drilling a propeller is that you can get the hole off a bit, unless you use a drill press and are very careful to exactly center the drill bit in the hole. A propeller reamer is self-centering. If the hole is slightly off-center, or even tilted a little bit, you can have severe vibration problems that may be very difficult to track down. It's not so easy for most modelers. This is true regardless of the brand of propeller.

We've used a very wide variety of propellers over the years and have really found little fault with any of the major brands. They all need some fine-tuning to bring into balance. Wood props are the most inconsistently-balanced in the off-the-shelf condition. You do need to check the balance of all props before you fly them. It's a good idea to have a few spares that you've balanced and know are good.

bax

I agree with BAX -- Both Master Airscrew & APC are reputable props & are used by thousands of modellers. Make sure that you balance all of your props & ensure that the shaft holes are true if you ream them.

From what I have read in this thread, I believe that you are over-propping your engine. A .46 LA can't effectively pull either an 11-6 or 10-8 prop. An 11-4 will work far better than the 11-6 where you want acceleration, climb & aerobatics. If speed is your need, a 10-7 is the max you should inflict on a .46 LA. Over propping will overheat the engine, increase radial crankshaft loads, increase piston side-load, increase vibration and shorten its life.

Single cylinder model engines are balanced to run smoothly in the upper end of their power band, & if you are overloading the engine with too much prop, you are pushing the revs down at full load & there is a good chance that you are out of the dynamic balance range -- that could be where your excessive vibration is comming from.