Jump to content

dynamic balancing and chasing your tail

Badmoonraising

By Badmoonraising
in General Mooney Talk

 Share

Recommended Posts

Badmoonraising Enthusiast

Badmoonraising

Posted
Posted

After having the prop overhauled it seemed reasonable to do a dynamic balance. This is a first for me. I was the assistant only and my AME is using the equipment for the first time. We had quite a time of it. Often getting close to the .06 ips. But when the rpm was raised to cruise speed the whole thing went off the rails i.e. not balanced at all. To make a long story short; we pulled, cleaned and tested the plugs. That was a real eye opener. Six of the eight plugs gave up on us once the pressure neared 80 psi. Some far before that pressure. Needless to say I replaced the plugs and we managed to balance to .01 ips. 

So here's the thing for me; The plugs were replaced August of 2015. The is less than 200 hours on the plugs. Probably quite a bit less. 

Never having done dynamic balancing before, it seems like such a good diagnostic beyond obtaining a smooth running machine. 

  • Like 1
Link to comment
Share on other sites
MB65E Grand Master

MB65E

Posted
Posted

I’ve been told similar things by a an awesome guy that balanced my engine. He even mentioned massive plugs cause more vibration. I thought it was a little silly that he could isolate the vibration to plugs. However, he worked for Chadwick and helped designe the systems in place today. Another neat thing I learned is that they weight some control rods on helicopters to prevent harmonic vibration. 

-Matt

Link to comment
Share on other sites
jaylw314 Grand Master

jaylw314

Posted
Posted

What RPM were you using to do the dynamic balancing?  The balancing should really be done with the engine running at cruise RPM, 2400-2500 if possible.  The fact that you guys balanced it and THEN checked it at cruise RPM doesn't sound right.

I previously balanced at 2400 RPM at 0.04 ips and was very happy with the results.  With a new prop, I balanced it to 2500 RPM and 0.01 ips and am less happy with the results--it's smooth about 2400 RPM, but once I'm below that it's noticeably worse than my old prop between 2000-2400 RPM.  Of course, we're talking about a different prop so that may not be comparable.

Link to comment
Share on other sites
jaylw314 Grand Master

jaylw314

Posted
Posted
24 minutes ago, Badmoonraising said:

We took averages at 1700 rpm and 2600. 

What brand of plug is recommended???

I've got a hard time imagining you could balance at two different RPM's.  Not an A&P, but the guy who did the balancing just wanted one RPM.

In terms of plugs, people seem to prefer Tempest over Champion by reputation.  People seem to think fine-wire plugs are worth it, but it's a cost/benefit problem.

If you have plugs bad enough to affect ignition, that should have been apparent on either the runup or an in-flight mag check with a 4-cylinder engine monitor.  Not clear if you have an engine monitor.

  • Like 2
Link to comment
Share on other sites
carusoam Grand Master

carusoam

Posted
Posted
4 hours ago, Badmoonraising said:

Several questions there;

Don't know what you mean by Champion Massives? But yes they were Champion. 

The average that we really went for was cruising RPM, 2,600-2,650. 

And yes, we did clean and gap plugs before testing. 

I will look for a set of Tempest online to replace for next annual. 

Badmoon...

There are two manufacturers...

and

Two types of plugs...

One manufacturer has terrible quality challenges with no end in sight...

And fine wires look more similar to automotive spark plugs... and provide for better airflow where the spark occurs...

When money is scarce, often people will put a set of fine wires in the lower plug locations... where the benefit is slightly better at burning off oil that may collect in the lower areas...

Talk to your mechanic about what you want.  He will be familiar with these devices...

Measuring resistance on failed plugs is a mechanic 101 type of skill...

PP thoughts only not a mechanic...

Do you have a Gill battery as well? Another manufacturer with quality challenges...

Best regards,

-a-

Link to comment
Share on other sites
Hank Grand Master

Hank

Posted
Posted

Don't feel too bad, @Badmoonraising. I replaced my Champion massives two years ago (each plug cost twice what a set of six for my truck did) and they've been doing quite well. Fine wire plugs run 3-4 times more than that. If your lower plugs foul often or show oil, adding fine wire plugs there can be beneficial. They seem to oerform better LOP than massive plugs (compare the size of the electrodes and the names will become obvious), but my C will barely run LOP.

I do find that leaning heavily on the ground has stopped almost all lead fouling on my plugs, and it keeps me from taking off partially leaned and cooking the engine; in fact, I have to richen up just to taxi uphill . . . .

Link to comment
Share on other sites
gsxrpilot Grand Master

gsxrpilot

Posted
Posted
1 hour ago, mcrouch said:

YIKES!! There is no freaking logical reason that spark plugs should cost that much $$. That is ridiculous.

One of the first things I did when acquiring my 252 was to swap out all the Champion massives for Tempest fines. They are expensive, but after spending north of $100K on the airplane, another $1K (12 plugs) to have it running its best seems normal. I haven't had a single fouled plug since the swap. I also added an EDM-900. With a $60K engine on the nose, protecting it is a solid investment. 1500 hours on original cylinders says the investment has already paid for its self.

Link to comment
Share on other sites
jaylw314 Grand Master

jaylw314

Posted
Posted
18 hours ago, Badmoonraising said:

Don't have a true engine monitor. Just EGT/CHT on one. I'd love to have one. Might kick my ADF off my panel for one. 

I'd say the engine monitor is a better first investment than the fine-wire plugs.  If you were having ignition problems, it would have saved you hours of pulling and bench testing all your spark plugs--you could have easily identified which specific plugs were problematic. 

Fine-wire plugs might help or they might not.  Champion massives used to suck, but according to one of the Mike Busch webinars, they quietly changed their design to be more like Tempest, so in theory they may not suck as much anymore.  In the end, fine-wire plugs are at least similar in terms of cost-effectiveness (they cost 3-4x as much and last 3-4x as much) so the only real negative is the up-front investment cost

As to the balancing, I'd suggest running at 2500 RPM while balancing.  Most people seem to shoot for that RPM during cruise, and that's when you care about vibrations the most.

  • Like 1
Link to comment
Share on other sites
Bolter Mentor

Bolter

Posted
Posted
23 hours ago, jaylw314 said:

I'd say the engine monitor is a better first investment than the fine-wire plugs.  If you were having ignition problems, it would have saved you hours of pulling and bench testing all your spark plugs--you could have easily identified which specific plugs were problematic. 

Fine-wire plugs might help or they might not.  Champion massives used to suck, but according to one of the Mike Busch webinars, they quietly changed their design to be more like Tempest, so in theory they may not suck as much anymore.  In the end, fine-wire plugs are at least similar in terms of cost-effectiveness (they cost 3-4x as much and last 3-4x as much) so the only real negative is the up-front investment cost

As to the balancing, I'd suggest running at 2500 RPM while balancing.  Most people seem to shoot for that RPM during cruise, and that's when you care about vibrations the most.

What was the time frame for this "quiet" change to the Champion design?

Link to comment
Share on other sites
Cyril Gibb Experienced

Cyril Gibb

Posted
Posted
On 10/19/2018 at 11:57 PM, carusoam said:

 

On 10/19/2018 at 11:57 PM, carusoam said:

...Two types of plugs...

I’d view it as 2 1/2 types.  For massives, there are also BY plugs with an extended nose designed originally for oil fouling on the bottom plugs. An additional advantage is the same price as other massives.  Also the theoretical advantage of firing more within the cylinder fuel mixture rather sparking at the edge of the cylinder head which, again theoretically, should give the effect of more spark advance.

Works for me.

  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.