Thorp Air Command - T18.net

I got to the hangar today & measured my ring, as close as I could. These should be accurate enough -

Thickness: 15/16"
Width: 1 7/16"
O.D.: 11 1/2"
I.D.: 8 5/8"

Here are some pictures... the first shows how some washers are used for balancing -

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

John, Thankyou so much, this will get the process started and probably finished. I see you Recommend having it all balanced as a unit, ring gear, ring and prop. I do have access to an engine balancer that can balance the ring before install..What process do you use to balance the entire package, just whenever you get a minute.......Thanks again. Dan

John, by the way, how is the fox comming, is it taking shape, bout ready to get it off Tera Firma ? Dan

Dan,

I have an ACES dynamic balancer rig. It's a great tool.

The Kitfox build is moving along, slowly. Just started to cover the fuselage... the tail feathers & wings are done and ready to fly. I'm planning on buying an engine in July.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Hi John,

I noticed the washers on your weight ring and I was wondering, are they all on the same side?( front side) If they are, you would have a better balance situation if you split the balance weight/ washers so that they are on both sides of the flywheel/weight ring assembly. As the assembly rotates the balance weights will want to exert a force towards the center of mass of the rotating assembly.

Regards,

Jim

2 things Jim... I'm balancing the entire rotating assembly - ring, prop, spinner, etc. They are closer to the center of mass as is. Secondly, there are potential clearance issues on the back side with the alternator belt, etc.

It has worked very well as you see it. I can get the vibration down to 0.02 to 0.03 ips.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

John,

That's very good.(0.2-0.3 IPS) I was thinking that having all the components balanced as well as they can be would only help with respect to the assembly.

Best regards,

Jim

Thanks Jim... I agree. I think you should statically balance the propeller as well as you can before installation, but the ring should be pretty perfect if it's machined carefully. Once it's installed, you're limited to a dynamic balance, involving the entire rotating assembly as I said before. With a prop extension, applying the weight to the ring gear is not always effective enough, but it worked well for me since I had already balanced everything without the inertia ring installed. Sometimes you have to add weight to the spinner backplate instead or also. Again, in regard to adding weight to the front AND back of the ring, it is never recommended to add multiple washers under the head of a bolt, and there is a potential clearance issue on the back of the ring gear.
By the way, it's 0.02 & 0.03 IPS.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Well, I got the Inertia ring cut, drilled & painted, it was cut to the Dementions that John gave me out of cold steel. I had it water jetted out of plate and the I ran all of the Finised dementions out on the Lathe. My Lathe is small so I had to indicate the thing about 3-4 times as I was cutting on it, I chucked up the ring gear in the Lathe and then indicated in the ring on the front of it to within .0015 and then transfer puched the hole locations onto the ring. After drilling and Champhering the holes I bolted it up to the ring gear whilst the gear was in the chuck( the gear was chucked from the ID bore in the center)and then I indicated it in on center of the gear all the whilst snugging up the bolts. This was a most tedious process as the bolt clearances were next to nill, But it ran out at the .0015. John ,you are correct, it helps smooth things out, Idle is smoother, running at RPM is smoother, I had a smooth engine to start with but this is the Icing on the cake. Seems it deadens the pulses, the ole Lycasaurus does indeed like to have a little flywheel effect after all. All I could grab onto was half the ID of the ring to start with, the cutting was slow and pains taking and it took some time but it did pay off, and by the way, I ran the indicator on the gear to see how accurate the machining was on it from the factory, it was ok, considering it was a part done in a production run.....Thanks John Dan

Thanks for the report Dan! I'm proud of you... sounds like you had to do it "the hard way"! I think you'll probably find that the engine will now run reliably at a little lower rpm. If you can get everything dynamically balanced now, you will really be happy with it, I'm sure. Sure wish I was a little closer to you - I'd do that for you. Good job!!

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

If I were to machine another ring I would change just a few things as far as the technique part of it that is for sure, the accuracy I am stickler about so it will probably always take me just a little longer to turn a part. I have seen your work, we have alot in common when it comes to the Machine shop. That ring raised my Brows a bit when I cranked the old bugger up, when I hit 2500 on the tach they raised a bit more. Seems when that mass starts moving the starter doesnt work as hard either, seems a little weight put in just the right spot is not a bad thing at all. Dan

Dan,

I'm new to the board here and have been scourering the Internet for information regarding the inertia ring. I have a quote from a local machine shop to produce a unit based on the dimensions I found earlier in the thread.

After running this assembly for a year, is there anything you would change if you made another?

Thank you,
Alan Blythe
Bartlett, TN

Hey John, why are there braided lines plumbed into the front of the lifter oil galleys on both sides?




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http://www.dixiefriedfabrication.com/

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Hi Lou,
The pictures didn't come through for me, but I assume you're talking about the line at the top front of the engine... it's a single line, connecting the 2 threaded ports on both sides together. It's a little bit of a long story that I believe I've related on this forum in the past, but I'll try to give you a shortened answer. Years ago in the 90's a friend, Ray (now deceased), who raced his Pitts at Reno, had such a line on his engine. He said that he used to have a problem with a very oily spark plug on the #4 cylinder of his engine every time he checked. Someone told him to install the line, he did, and the oily plug went away. My #4 bottom plug was also oily whenever I checked it, although it didn't seem to be a problem. I called and talked to one of the engineers at Lycoming about it. He said that adding that line wouldn't hurt anything, but it wouldn't have any effect other than adding a couple more places for leaks to develop. OK, so I tried it anyway, and sure enough my plug wasn't oily anymore. Supposedly the theory is that since oil enters that galley from the back of the engine then goes forward and crosses over to the right side galley through an internal port and back down that side, that the internal port is possibly a little undersized, and the oil pressure is greater right where the oil enters above that #4 cylinder. I guess that depending on valve guide condition, etc., that perhaps excessive oil builds up under the rocker box cover and seeps down into that cylinder when the engine is shut down. The line is supposed to help even the pressure between the 2 galleys. I know that theory sounds a little dubious, but I've got nothin' else. Some people who've tried it say it worked like it did for me & Ray. For others it supposedly didn't have any effect. I used a -3 Teflon lined SS braided line with steel fittings.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Hi Alan, Yes, I have run the Ring for a while now and I would change just one thing, the color, I would have painted it just s touch darker and that's about it. However! I just installed an electronic Ignition here not long ago, between the Ignition and the ring the old beast runs a lot smoother. When I installed the ring it got smoother especially at Idle, I did notice it was also smoother at cruise. Then the Ignition was installed, it got smoother yet through the entire RPM spectrum. I also have a full 100 Rpm increase on takeoff. I Had to re- learn how to run the old devil when I installed the Ignition, it starts better, it leans different it just has some different characteristics than what it had, in a very good way.I was told it would be a different running rig when I bought the Ignition, then I went on to find out that it was the truth. As John reported some time ago, if you run a light weight wood prop, your Lyc will appreciate the Inercia ring and so will you, but run it without the ring for a bit, and then install the ring so you can see and feel the difference for youself, it is kinda funny how well that chunk of cold steel works.....Dan