Motor Balancing?

[GMONEY]

Where can I find info on how to balance a motor? I was talking with my mentor over the weekend and neither of us have ever needed to go down that road. I want the smoothest running helo around. I love when your time makes a better flying helo not your wallet..

Thanks
Gmoney

[jimras]

You shouldn't have to worry about that

The kind of RPM's they turn, they have to be balanced
right from the get-go.

[blax1]

Hi G
When I get home tonight I'll did out the mag and get the number for you, there was a great article some time back on how to balance fly wheel and clutch assembly, here is a link back to my C5 thread and some photos of how I did it... :cool:

http://www.rcheli411.com/forum/showthread.php?t=3062&page=2&pp=10&highlight=ralphs

Hope this helps :)
Ralph

[blax1]

I just finished reading a paper back written by Dave Day, he's a RCHeli- Guru from England, he had a great article on helicopter (nitro) Vibrations...... :)

I agree with you G if you get a heli as smooth as, you are way better off.... :cool:

One vibration that been interesting me, is my Rotopod, only when the main tank is empty, and the engine is drawing fuel from the secondary tank, the Rotopod gets the shakes, which eventually transmits it way up to the rotor head, needless to say I just land her, refuel her and go again, with no vibration until the main drains again, this phenomenon has me totally stuffed, BUT on reading the above article apparently on a nitro heli any vibration below the engine is from the engine Eg skids shaking etc and any vibration above is related the head and TR assembles, my vibration is coming from the engine, so I will be re-doing the dial gauge checking, now some people will say but you have already done that......But when I first started my heli, the bloody clutch unwound on the thread because I didn't use red loctite, well I glued it properly but didn't do the dial gauge again, so my thinking is my problem lies here, as well as the Rotopod which I intend to dump this weekend, sorry for the long story, but the bottom line is I agree with you smooth is sweet :cool:

[schluterdude]

An interesting side note to your dial indicating problem, that the plankers have been using for years to help balance out their motors.

A single cylinder engine is inherently out of balance, no matter what sort of balancing the manufacturer tries to achieve with the crank counter weight. This balance is not necessarily from the rotating components itself, but rather, from the power stroke of the engine. One way to attempt to counter-act this is to balance your fan/clutch/flywheel assemble as good as possible. Often times, you may find yourself wondering "gee, this is an awful lot of material I am removing from this component!" While this is true, you do not want to destroy the structural integrity of the part (centrifugal forces even on "light" parts gets pretty extreme at the rpm's these motors can, and do, spin). As such, if it is ever so slightly still out of balance; place the heavy end 180 degrees from the piston at top dead center. This effectively turns this outside spinning mass into a counterbalance of the motors internal rotating assembly.

Some may question this, but, take into consideration a full size car. On some vehicles, the flex plate and torque converter, or the flywheel on a standard transmission, is keyed or marked to a specific point. This is an external balance to the motor, even though if you look inside the crankshaft has already been drilled on its counterweights to balance the assembly. The reason for this is to help softer the power pulses of the motor in an effort to help make the ride smoother for the occupants.

Another reason for this is that we are unable to dynamically balance our components. Way back when (before I was born!), car tires were only balanced in a manner similar to the way we balance our fans and clutches. They were put on a rod, and weight was added to "balance" the assembly of the rim and tire. Now, they dynamically balance the assembly, which is why weight is put on the inside as well as the outside edges of the rim. This balances the tire at higher speeds where a vibration could be induced as a result of a mismatch between this inside and outside edges of the tire when viewed from the side.

One last tid bit, this is why Porsche uses a flat six engine to smooth the engine out, because the vibrations cause an energy loss in the grand scheme of things because it takes energy to cause the vibration in the first place. Granted, it can be said that it also takes energy to soften the vibration, and this is true. But in the end, the net gain is greater than the added cost of designing a motor that way when you are trying to squeeze every last ounce of power out of a given displacement. "Flat plane crank" v-8's and v-10's are also derived from the same principal (engines such as Ferrari), but, turned into a V configuration.

Sorry for the long tangent guys... My wife just pointed out I was rambling on, and she's right. I thought an example outside the realm might help to illustrate the point. Was I right, or was it just annoying beyond belief?
:cool:

[helifreak5623]

My Dad and I restore antique motorcycles. We have a 1971 Triumph Daytona 500. That's not important, but what is is that it had balances shafts inside the motor so that at high RPM the pistons stay in sync. I don't know if heli motors have these shafts, but if they do, then you have to balance them so they can do their job. Hope this helps, and sorry it's kind of off topic :rolleyes:.

[schluterdude]

yup, those balance shafts do a similar job. many engines use them to this day!

[blax1]

The definitive answer on balance shafts

http://en.wikipedia.org/wiki/Balance_shaft

schulterdude, your input and anyone elses for that matter is always welcome, great info :cool:

[schluterdude]

an interesting note if anyone out there drives a DSM car (eagle talon TSI or ESI, mitsubishi GSX, or plymouth laser TSI), i remember hearing somewhere that if you were to bypass the balance shaft, it can up your high end power. this makes sense as it robs some power to make the motor smoother (see above post). however, at the same time, the engine would be SIGNIFIGANTLY more "rumbly" and "twitchy". it may also cause some problems as far as longevity is concerned. but, if you're a hard core drag racer or solo II enthusiast, it may be worth more research as it would also need a different timing belt because it is driven from the belt that's taking care of your cam shafts to make sure your nice expensive sodium filled valves won't crash into those nice expensive forged pistons you're probably already running.

gotta love those interference four stroke motors!!!

btw, from what i've noticed, most four strokers for our models are. otherwise, there would be no need for the valve reliefs in the tops of the piston! too bad the four strokers aren't lighter and/or more powerful to make them practicle for heli's. the torque curve of a four stroke is hard to beat...

[GMONEY]

Guys thanks for the killer repies. My O.S. 91 is coming out on thursday nite.. She runs good and powers my Raptor with authority. I just think a little extra effort will make her even better.. I am also going to try using a newer battery technology to save some weght..

Thanks
Gmoney

[schluterdude]

i've never really heard anyone talk about it, but...

anyone out there bother balancing their main gear? i was thinking about the smoothness issue, and, that's a decent size wad of plastic spinning just as fast as the main rotor.

i know there is always that point of where "enough is enough" when it comes to the "pinash" details like that. i was just curious on everyone else's thoughts on that one. personally, i can't forsee it making that much of a difference, due to the signifigantly lower rpm's comared to the motor and the reasonably small moment it would induce compared to the main rotor. but, i would be willing to bet that the gear is unbalance from the factory, because just like any plastic part as it it shot into the mold and dries there are always dense and light spots throughout the part.

[GMONEY]

Schulterdude, I'll let you know on the main gear.. While the motor is out of the Rappy I was going to check that out also.. Hey its a hobby right? As a side note I normally wouldnt do any of this I perfer to fuel and fly.. But lately I have been thinking and as all of you know that is dangerous.. My flying abilites will never get close to even testing a poor running helo let alone a killer running helo..

G

[heli-cuzz]

Where can I find info on how to balance a motor? I was talking with my mentor over the weekend and neither of us have ever needed to go down that road. I want the smoothest running helo around. I love when your time makes a better flying helo not your wallet..

Thanks
Gmoney




http://ebmods.com/

Its a shame, he only does 4 wheel engines. Best in the biz. Gotta love the dyno test.

[GMONEY]

Has anybody ever contacted this guy? I bet he would do our motors.. We could benefit from R&D thats done like that.. I bet a motor from that guy would be as smooth as silk. If he knew that was our intent he could easily provide it.. I used to send my bikes out to get printed.. They rocked!

G

[heli-cuzz]

G,
he's a good friend of mine. I've asked before and he's modded a OS32 I have. He's very busy with the buggy/truggy engines. You could try sending an e-mail to him if you really want a modded/balanced/blueprinted engine.

[J-Heli]

Has anybody ever contacted this guy? I bet he would do our motors.. We could benefit from R&D thats done like that.. I bet a motor from that guy would be as smooth as silk. If he knew that was our intent he could easily provide it.. I used to send my bikes out to get printed.. They rocked!

G

He did a nitro engine for my 1/10th touring car and when I got it back and ran it a few times, I was astounded. I didn't know that engines could get that smooth. That guy has some real talent. Guess heli cuzz knows that too.