Author Topic: Balance a Engine (Read 3152 times)

Chris Fretz · « **on:** January 06, 2018, 07:01:34 AM »

How do you balance the internal components of a engine?

Carl Cisneros · « **Reply #1 on:** January 06, 2018, 06:55:00 PM »

Chris

I will call you Sunday

Carl

RknRusty · « **Reply #2 on:** January 06, 2018, 10:27:02 PM »

Quote from: #Liner on January 06, 2018, 07:01:34 AM

How do you balance the internal components of a engine?

Hi Chris. Happy New Year... to you too, Carl.

Good to see you're still at it.
What in the world sort of project are you up to, balancing the engine's guts?
Rusty

Tim Wescott · « **Reply #3 on:** January 06, 2018, 11:09:10 PM »

Probably more than you wanted to know, but written by a model engine builder.

Keep in mind that you'll never perfectly balance any engine, and a single-cylinder engine doesn't even have a theoretically correct balance unless you add counter-rotating shafts.

Brian Gardner · « **Reply #4 on:** January 06, 2018, 11:24:00 PM »

I remember having to do all the calcs for "mechanics of machines" when I did all my engineering studies,...long time ago

Chris Fretz · « **Reply #5 on:** January 07, 2018, 09:25:54 AM »

Quote from: RknRusty on January 06, 2018, 10:27:02 PM

Hi Chris. Happy New Year... to you too, Carl.

Good to see you're still at it.
What in the world sort of project are you up to, balancing the engine's guts?
Rusty

Hi Rusty! Thanks! Happy New Year to you too.

Are you working on the Cardinal??

Lol I just thought it would be cool to undestand how these engines get "balanced/blue printed" kind of thing.
Butttttt I can see it is best left to the profesionals.

Chris

Quote from: Tim Wescott on January 06, 2018, 11:09:10 PM

Probably more than you wanted to know, but written by a model engine builder.

Keep in mind that you'll never perfectly balance any engine, and a single-cylinder engine doesn't even have a theoretically correct balance unless you add counter-rotating shafts.

Hi Tim. Thanks for the info. All I can say is Yikes!

Chris

Brett Buck · « **Reply #6 on:** January 07, 2018, 12:31:19 PM »

Quote

Lol I just thought it would be cool to undestand how these engines get "balanced/blue printed" kind of thing.
Butttttt I can see it is best left to the profesionals.

I am not aware of many people doing that with model engines, particularly the balanced part. And as noted, you can't really balance an engine, and which vibration modes you want to reduce depends on whether its a profile or a full fuselage airplane.

Brett

Lauri Malila · « **Reply #7 on:** January 07, 2018, 01:07:53 PM »

As a rule, mass produced engines are usually underbalanced. So it usually does no harm to add weight by drilling holes and inserting something heavier, like tungsten.
Stunt engine is a little problematic as it is difficult to make decision wether to focus on balancing reciprocating or rotating masses, so it makes it impossible to find an ideal situation over the whole used RPM range.
So, the least one can do to improve situation in a commercial engine, is to machine the counterweight a little to compensate the direction error caused by intake port (in shaft/rotor) opening, and remove unnecessary material in front of crankpin. Same operation corrects the typical mistake of symmetric counterweight. In resting position the crankpin should stay at a little after 12 o'clock, absolutely not before.
I don't think it's about "vibration mode" of differend nose constructions as brett wrote, but certainly a solid full fuselage is more tolerant for any kind of vibrator. It may well be that some harmonic stuff occur especially with profile fuselages. L

Air Ministry . · « **Reply #8 on:** January 07, 2018, 06:16:38 PM »

Pity It'd stick out the SIDE rather that underside or symetrically , But Gives Perfect Primary ( vibration ) Balance . so we're told.

There are primary & secondary (ad infinitum / Harmonics ) & rotateing plus reciprocating ' moments ' .

This Picture is a Dewkati SINGLE CYLINDER wit Bi - Dopawotsits .

Dane Martin · « **Reply #9 on:** January 07, 2018, 07:10:41 PM »

Quote from: #Liner on January 07, 2018, 09:25:54 AM

Lol I just thought it would be cool to undestand how these engines get "balanced/blue printed" kind of thing.
Butttttt I can see it is best left to the profesionals.

Chris

No way, I say have at it. Just use cheap engines or at least engines with readily available parts to practice with!

Brett Buck · « **Reply #10 on:** January 07, 2018, 10:17:07 PM »

Quote from: Lauri Malila on January 07, 2018, 01:07:53 PM

I don't think it's about "vibration mode" of differend nose constructions as brett wrote, but certainly a solid full fuselage is more tolerant for any kind of vibrator. It may well be that some harmonic stuff occur especially with profile fuselages. L

I think you want to err on the side of balancing it for the reciprocating mass and take a little more vibration in the side-to-side because you don't want to drive the fuselage in the weak direction. For a conventional inverted mount, it's a lot stiffer along the cylinder axis, so you probably want to care about the side-to-side motion more than up-and-down. For a general solution, probably want to minimize the maximum.

Point being is that anything you pick is a compromise, and the compromise might be different based on the application.

Brett

Chris Fretz · « **Reply #11 on:** January 08, 2018, 05:03:42 AM »

Quote from: Brett Buck on January 07, 2018, 10:17:07 PM

I think you want to err on the side of balancing it for the reciprocating mass and take a little more vibration in the side-to-side because you you want to drive the fuselage in the weak direction. For a conventional inverted mount, it's a lot stiffer along the cylinder axis, so you probably want to care about the side-to-side motion more than up-and-down. For a general solution, probably want to minimize the maximum.

Point being is that anything you pick is a compromise, and the compromise might be different based on the application.

Brett

Brett have you ever messed around with the internal balance of a mass produced engine to suite a profile or even a full fuse?

Chris

Brett Buck · « **Reply #12 on:** January 08, 2018, 10:09:02 AM »

Quote from: #Liner on January 08, 2018, 05:03:42 AM

Brett have you ever messed around with the internal balance of a mass produced engine to suite a profile or even a full fuse?

Chris

No, I have had experts do it for me, with dubious results. It's mostly a hypothetical discussion from my professional experience. One of my Foxes had tungsten counterweights that made it work better on profiles but they also ground away a bit on the pin side, and the pin broke off in a few minutes of running. One of my 40VFs had some grinding done on the pin side and along one counterweight, but I couldn't tell the difference between that and the stock engine in terms of vibration, or anything else for that matter.

Any current-production engine is good enough the way it is, as far as I can tell, and unless it's something is obviously wrong, probably best left alone, just because the danger of screwing something up seems much higher than correcting anything. First rule of engine modification, operate on the theory that while you are doing it, you are likely to break it and have stock spare parts available.

Brett

Tim Wescott · « **Reply #13 on:** January 08, 2018, 01:17:53 PM »

Quote from: Brett Buck on January 08, 2018, 10:09:02 AM

No, I have had experts do it for me, with dubious results. It's mostly a hypothetical discussion from my professional experience. One of my Foxes had tungsten counterweights that made it work better on profiles but they also ground away a bit on the pin side, and the pin broke off in a few minutes of running. One of my 40VFs had some grinding done on the pin side and along one counterweight, but I couldn't tell the difference between that and the stock engine in terms of vibration, or anything else for that matter.

Any current-production engine is good enough the way it is, as far as I can tell, and unless it's something is obviously wrong, probably best left alone, just because the danger of screwing something up seems much higher than correcting anything. First rule of engine modification, operate on the theory that while you are doing it, you are likely to break it and have stock spare parts available.

Wait. Isn't the Engineer's Creed "If it's broke, I can fix that, and if it ain't broke, I can fix that."? And aren't you supposed to be an engineer?

RandySmith · « **Reply #14 on:** January 08, 2018, 02:18:02 PM »

Quote from: Brett Buck on January 08, 2018, 10:09:02 AM

No, I have had experts do it for me, with dubious results. It's mostly a hypothetical discussion from my professional experience. One of my Foxes had tungsten counterweights that made it work better on profiles but they also ground away a bit on the pin side, and the pin broke off in a few minutes of running. One of my 40VFs had some grinding done on the pin side and along one counterweight, but I couldn't tell the difference between that and the stock engine in terms of vibration, or anything else for that matter.

Any current-production engine is good enough the way it is, as far as I can tell, and unless it's something is obviously wrong, probably best left alone, just because the danger of screwing something up seems much higher than correcting anything. First rule of engine modification, operate on the theory that while you are doing it, you are likely to break it and have stock spare parts available.

Brett

Brett is correct about leaving it alone, and if you don;t , be prepared to buy parts
However I do have to say that the B&B motor I do ARE better, and for the vast majority of them run smoother, The FOX Smith cranks were smoother than stock, The Thunder Tiger Aero Tigers run smoother than stock, as do the OPS ST and OS VF engines that I have done, over 7500 of them going back to the late 1980s
I have never heard of anyone having a crank pin , or crank counterweight break because of my work.
As far as FOX 35 they break routinely at the Counter weight crank pin and shaft, both at the front and at the window.

The OS FP and LA 35 40 and 46 series has one crank that came in much better balance than the other, it was made with the back side of the crank pin lightened , If I can pull one I will post a photo , the newer ones are full thickness and scalloped on the sides

But to back up Brett;s caution, I have seen a lot of messed up parts that have been cut/ground on by others

Regards
Randy

Chris Fretz · « **Reply #15 on:** January 08, 2018, 02:53:40 PM »

Quote from: RandySmith on January 08, 2018, 02:18:02 PM

Brett is correct about leaving it alone, and if you don;t , be prepared to buy parts
However I do have to say that the B&B motor I do ARE better, and for the vast majority of them run smoother, The FOX Smith cranks were smoother than stock, The Thunder Tiger Aero Tigers run smoother than stock, as do the OPS ST and OS VF engines that I have done, over 7500 of them going back to the late 1980s
I have never heard of anyone having a crank pin , or crank counterweight break because of my work.
As far as FOX 35 they break routinely at the Counter weight crank pin and shaft, both at the front and at the window.

The OS FP and LA 35 40 and 46 series has one crank that came in much better balance than the other, it was made with the back side of the crank pin lightened , If I can pull one I will post a photo , the newer ones are full thickness and scalloped on the sides

But to back up Brett;s caution, I have seen a lot of messed up parts that have been cut/ground on by others

Regards
Randy

Randy do you balance the FP and LA series that you sell?

Chris

RandySmith · « **Reply #16 on:** January 08, 2018, 03:57:27 PM »

Quote from: #Liner on January 08, 2018, 02:53:40 PM

Randy do you balance the FP and LA series that you sell?

Chris

Yes most of them, depends on what the owners want, I balance and Blueprint the OS FP and LA, except for the ones with the better crank, then I will take a small amount off of the side of it to help offset the crank opening hole, I do a head mode on the outside, that cuts a heat dam around the plug, some OS engine have this, as OS saw this somewhere and started doing it many years back, the one I cut is slightly wider and deeper, it helps the engine stay running clean in maneuvers by keeping the plug a little hotter, I have ran into OS engines without any chamfer on the rod, so that is checked, install the "CORRECT" size venturi for the spraybar you will run, ( This one thing caused more grief than anything else on FP-LAs)
and blueprint is deburring (yes I have found very bad burrs) and making sure it all fits as it should. Lastly I replace the philips with socket head bolts, and I either seal the backp-late with silicone sealant and locktight the rear bolts, that never comes loose or leaks, or I replace the backplate with a cnc aluminum one.
I still have some LA engines and FP s here, new and rebuilt.

Some people only want the Correct NVA and Venturi combo, and I do what ever they want.

Randy

Chris Fretz · « **Reply #17 on:** January 08, 2018, 04:15:50 PM »

Quote from: RandySmith on January 08, 2018, 03:57:27 PM

Yes most of them, depends on what the owners want, I balance and Blueprint the OS FP and LA, except for the ones with the better crank, then I will take a small amount off of the side of it to help offset the crank opening hole, I do a head mode on the outside, that cuts a heat dam around the plug, some OS engine have this, as OS saw this somewhere and started doing it many years back, the one I cut is slightly wider and deeper, it helps the engine stay running clean in maneuvers by keeping the plug a little hotter, I have ran into OS engines without any chamfer on the rod, so that is checked, install the "CORRECT" size venturi for the spraybar you will run, ( This one thing caused more grief than anything else on FP-LAs)
and blueprint is deburring (yes I have found very bad burrs) and making sure it all fits as it should. Lastly I replace the philips with socket head bolts, and I either seal the backp-late with silicone sealant and locktight the rear bolts, that never comes loose or leaks, or I replace the backplate with a cnc aluminum one.
I still have some LA engines and FP s here, new and rebuilt.

Some people only want the Correct NVA and Venturi combo, and I do what ever they want.

Randy

I should of bought my LA engines from you! What do you do to the Magnum 52?

Chris

Nevermind I saw it on another thread...

Brett Buck · « **Reply #18 on:** January 08, 2018, 09:38:00 PM »

Quote from: RandySmith on January 08, 2018, 02:18:02 PM

Brett is correct about leaving it alone, and if you don;t , be prepared to buy parts

But to back up Brett;s caution, I have seen a lot of messed up parts that have been cut/ground on by others

Some of the workmanship you see is just catastrophic, I just don't understand how some people come to the conclusion they know enough to undertake such projects. I am no engine expert, I know how I want it to run to be able to fly stunt effectively. I know just enough to know I am not qualified to safely do most of the stuff we talk about in terms of modifications - but apparently that puts me ahead of most of the people offering rework services.

Brett

Brett Buck · « **Reply #19 on:** January 08, 2018, 09:48:19 PM »

Quote from: Tim Wescott on January 08, 2018, 01:17:53 PM

Wait. Isn't the Engineer's Creed "If it's broke, I can fix that, and if it ain't broke, I can fix that."? And aren't you supposed to be an engineer?

Well, technically, I am a *successful* engineer who managed to work on the same or related national priority program for 35 years - so I have a lot of confidence that "x" can be done, but experienced enough to not to just assume it's going to work as I imagine. You have to be willing to objectively evaluate what your system is doing, and if it isn't working the way you expected, you have to find out why, in detail, and either fix the bug or change your idea.

I see problems along these lines with stunt, people have all these "theories" about how should work, but then when it doesn't, very frequently, they don't address the problem in any useful way. It's everywhere - designing, building, engine setup, trim, flying, and judging. There are far too many examples just in currently active threads that I would get carpal tunnel just making a list.

Brett

Peter Nevai · « **Reply #20 on:** January 20, 2018, 06:28:24 PM »

Over the years there have been as many people doctoring model engines as ones modifying CB radios. NOTE: The CB radio guys usually produced more reliable results. As many had complaints of ruined motors as those singing their praises. The majority of successful ones just remedied short comings of certain engines like making bushed con rods for those engines that only had aluminum to steel contact at the crank pin. These days the good ones like randy have ABC piston and liner retrofits made and again look to remedy obvious shortcomings of engines they modify else they create entire engines specifically designed for CLPA. Single cylinder engines inherently vibrate. In motorcycle applications rubber isolators are used to help kill the vibrations in cases both at the engine mounts and the handlebars. They are / were called "Thumpers" for more than one reason. As the photograph posted shows, designs like counter rotating mass and other techniques are employed to tame vibration with mixed success as it usually only successful at rather narrow RPM ranges. But often at least in motorcycle applications sometimes vibration is considered an attractive visceral feature. Go Figure, I personally was never a fan of numb butt or hands.

Air Ministry . · « **Reply #21 on:** January 20, 2018, 09:00:57 PM »

Maybe Someone knows how to balance One of THESE :

Early Aeromuddler picture has a conventional 180 degree full counterweight , most injuns unfortunately have thick ' V ' narrow at crankpin .

Figure get the Arc Welder & grindstone out .

If its ok on a 426 / 440 etc , should hang in ( counterweights ) if a homogenous welders employed .

Actually , a FP 40 crank something like starts to fit , At the end of the day youd end up with a Raduga/ Rainbow Cased FP 40 . ( tearing hair out Icon )

Robert Zambelli · « **Reply #22 on:** January 21, 2018, 11:57:15 AM »

Hey Matt - did you ever run the Raduga?
I have some that have never been started.

Bob Z.

Air Ministry . · « **Reply #23 on:** January 21, 2018, 04:48:35 PM »

I think I mustve once or twice , up Qld I had a rear muffler depart , its still in the grass ,
apparently theres still a Rossi or Nelson in the @#$% ponds ( shades of brooklands ) .

wouldve been in the Phantom ( side mount ) , I think . maybe the Yak .
Woulda had it a tad rich , seem to recall ' vibration phases ' berrrrr..... etc , otherwise wasnt totally hopeless .
Got a really nice fit one now , and 3 ' other ' . tho theyre not bad , not like silk like the bedded in one . to Turn , at least .

Picture in Aeromodellor shows dismantled , with a pork chop crank , or 180 deg. full circle and tapered leg from to crank pin .
where my 4 have narrow V crank web , thick . Would you throw it in oil or water , dull red from Arc , welding it ,
to maintain hardening , Or reheat it after the disc grinders been at it , and quench semi finished ? .

Theres actually pictures of welding counter weights to V 8 cranks , etc . in a 50s hot rod paperback A6 size book .