How to balance a compressor pt.1 - A Closer Look

We are building up a stage 5 compressor disk for a J79 turbojet engine from a fighter aircraft in active service.
We are sorting and installing the blades so we can balance the disk.

[AgentJayZ]

@castlebravo Yes, there are many disks with odd number of blades. It's not that big of a problem, because the mathematical, precise and calculated method of balancing gets you about 80% to the goal.
The last 19% of the way to a near-perfect balance is achieved through a combination of judgement, luck and black magic.

[saxonlight]

Another very interesting video. I am learning so much about jet engines. Thanks.

[AgentJayZ]

@rxvexe Aaah, such a seemingly simple question.
To disassemble and reassemble a turbine would take about 10, a turbine engine would take about 100.
But nobody would just dis and re without cleaning, inspecting, repairing or replacing the components before reassembly. That takes many hundreds more.
A thorough overhaul can take months.

Honest, this is the short version of the answer to your question.

[AgentJayZ]

@Helicopterpilot16 Today, I am putting the 9th and 10th stages on the compressor rotor of another afterburning J79.
We will be testing it in a couple of months.
These things take time...

[AgentJayZ]

@Helicopterpilot16 All I can say is it is going to be used in an aircraft, but that you already can tell because it has an afterburner.

[castlebravo]

Wondering if you've ever come across a disk with an odd number of blades. One engine I worked, the 1st stage compressor has an odd number. I remember you would weigh and figure out one set of three, then some math and a chart in manual, they would be installed about 120 degrees apart, then the remaining blades go in just like you did.

[AgentJayZ]

@bhp1984 Well, compressor blades are nowhere near as heavy as turbine blades, so the dovetail must be strong enough.
And it is a simpler shape that can be forged on the blades and cut more simply into the disk, saving manufacturing expense.

[AgentJayZ]

@Helicopterpilot16 That's a good idea. I'll see what I can do. Take a look at one of my first posts to see it shooting flames from its exhaust.
"Starting a large turbine engine"

[Helicopterpilot]

@AgentJayZ Ha I've seen it! Dang cool. are you going to run another j79 with the afterburner at all! I'd really like to see the nozzle movment and see what makes the sterotypical F-104 howl!

[Helicopterpilot]

I want to move to Fort St John BC and get a job there! i'd probraly be really good at balancing!

[Helicopterpilot]

@AgentJayZ Can't wait to hear it! Do you know what kind of aircraft its going to if any?

[AgentJayZ]

@TheAteston We would, if we put it together dirty...

[Helicopterpilot]

Could you make a video about the huffer cart starter?

[yakovb]

@AgentJayZ, awesome videos! I'm learning things... thanks!
I was wondering are you using any software at least for the initial setup. IMHO it shouldn't be too hard to write something to do this in one step.

[antoine]

Good mornign sir, first of all thanks for your useful videos they are amazing! I've a question: why we use different weight blades?

[bhp]

Any idea why compressor blades have simple dovetails rather than the fir-tree style on turbines?

[adrielgbr]

Hi! My name is Adriel, I'm from Argentina.. Could you send me an e-mail? Because I would like to ask you some things about homemade AXIAL turbines and balancing...
I would be so thankful...

Greetings from Argentina!