Mailing List flyrotary@lancaironline.net Message #21476
From: Ed Anderson <eanderson@carolina.rr.com>
Subject: Re: [FlyRotary] Seal Hrdness
Date: Thu, 5 May 2005 21:25:46 -0400
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Thanks Bob,
 
Verrrryyyyy Innnteerreessstinnngg.  So it does appear that my seals were "soft" at least in comparison of the Hurley seals of Rusty.  Only one area of the six areas you tested on my seal was above Rockwell 30 - whereas 11 out of the 12 areas tested on Rusty seal were above Rockwell 30.  Also one hit on my seal indicated a Rockwell hardness of only 23.1. I am not knowledgeable enough to know if those difference are a major significance or not - but it does show the metal in my seal of less hardness than that of Rusty.
 
  Your findings plus (as you noted) the ridge of metal gouged out of the seal by apparently its rubbing against the top edge of the apex slot indicates to me that my seals were likely less that they should have been.
 
Appreciate you taking the time and trouble, Bob.  Should have sent you one of Tracy's to test as well - but mine were all in the engine {:>)
 
Best Regards
 
Ed
----- Original Message -----
Sent: Thursday, May 05, 2005 8:28 PM
Subject: [FlyRotary] Seal Hrdness

OK here are the HARD numbers, but first let me give some detail on what equipment I used and how the tests were conducted.  The equipment used was an Equotip 2 portable hardness tester, manufactured by Proceq Sa, Switzerland.

 

The following is an explanation snagged from there web site.

 

“The EQUOTIP 2 metal hardness tester is a light weight, yet powerful portable hardness tester for all metallic materials.  It measures the Leeb value (L) for materials, which is a ratio of the impact velocity to the rebound velocity.  This L value is then converted to standard hardness scales such as Rockwell, Brinell, Shore, and Vickers using conversion tables stored in the display unit and generated from the original Leeb block.”

 

I had mentioned in a previous post that the numbers that I generated when testing the stock seal were jumping around.  Well like the old saying says, “when all else fails read the instructions.”  The seals are not thick enough to be tested without providing a good support, in fact they are at the minimum thickness for the impact device that is used.  So the seals were coupled to a heavy support base for the test.

 

The seals were tested in three locations on each side, the straight side end, center and the corner seal end.  Each set of figures represents 3 impacts, the first figure is the LOWEST “L” value in the series, the second is the HIGHEST “L” value, the third is the RANGE the forth is the MEAN “L”, the fifth is the HARDNESS.  In the first series, “L” value is converted to Brinell hardness, in the second series “L” is converted to Rockwell.

 

 

Min

Max

Range

Mean

Hardness Brinell

Rusty Duffy

 

 

 

 

 

Side 1

574

581

7

577

298

 

574

590

16

580

302

 

578

597

19

585

307

Average

 

 

 

 

302.33333

 

 

 

 

 

 

Side2

560

573

13

566

286

 

569

584

15

578

300

 

586

598

12

591

314

Average

 

 

 

 

300

 

 

 

 

 

 

 

Min

Max

Range

Mean

Hardness Rockwell

Side 1

571

593

22

580

31.4

 

578

582

4

580

31.4

 

561

563

2

562

28.8

Average

 

 

 

 

30.533333

 

 

 

 

 

 

Side 2

576

578

2

577

31

 

578

583

5

580

31.4

 

583

587

4

585

32.1

Average

 

 

 

 

31.5

 

 

 

 

 

 

Rusty's Broken Seal.  Only tested in 2 places

Min

Max

Range

Mean

Hardness Brinell

Side 1

571

600

29

584

306

 

565

588

23

576

297

Average

 

 

 

 

301.5

 

 

 

 

 

 

Side 2

588

592

4

589

312

 

580

600

20

587

310

Average

 

 

 

 

311

 

 

 

 

 

 

 

Min

Max

Range

Mean

Hardness Rockwell

Side 1

558

580

22

570

30.1

 

576

588

12

584

32.2

Average

 

 

 

 

31.15

 

 

 

 

 

 

Side 2

576

588

12

583

32.1

 

587

592

5

589

33

Average

 

 

 

 

32.55

 

 

 

 

 

 

 

 

 

 

 

 

Ed Anderson

Min

Max

Range

Mean

Hardness Brinell

Side 1

525

554

29

541

260

 

524

549

25

536

255

 

548

562

14

557

277

Average

 

 

 

 

264

 

 

 

 

 

 

Side 2

557

584

27

571

292

 

566

577

11

573

294

 

574

577

3

575

298

Average

 

 

 

 

294.66667

 

 

 

 

 

 

 

Min

Max

Range

Mean

Hardness Rockwell

Side 1

534

562

28

550

26.9

 

516

538

22

531

23.1

 

530

558

20

549

26.8

Average

 

 

 

 

25.6

 

 

 

 

 

 

Side 2

562

588

26

577

31.2

 

555

68

13

564

29.2

 

554

578

24

567

29.6

Average

 

 

 

 

30

 

 

I can only speculate on the difference between hardness values on Ed’s seal.  This seal had a noticeable ridge worn in both sides from the apparent rocking motion in the rotor apex slot.

 

I am not a Professional Engineer, But I did sleep in my own bed last night. (I think!)

 

 

Bob Perkinson

Hendersonville, TN.

RV9A

If Nothing Changes

Nothing Changes!

 


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