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Husqv repair-Classif'n 5: Hardware...problem...12 ref O (actually 8)-Ron—

03/10/2008 9:51 AM

Classification 5 - Hardware interface/reassembly & setup problemPENDINGPOSTS

  • a) 12 ref O (actually 8)-Ron—1st part: agrees w/ Metalsmith, asks pics of pin mentioned in linked posting; thinks spring concentric w/pivot as shown in posted drawing and presents evidence.
    • i) Cowanon responds to 1st part of Ron's statement: The picture and explanation are provided below. Ron, please see answer in section d), below.
  • b) 12 ref O Ron— (2nd part)—agrees w/ Metalsmith, asks pics of links, thinks spring is concentric w/handle per posted line drawing...
    • i) 14 rf 12-CowAnon—(already posted disagree idea of spring pivoting on handle pivot, more reply to Ron's 2nd assertion about Ron's description of "imprint" on handle pivot axis retainer nut: partial change of mind, correction of disagreement.
    • ii) Ron, here are two close-up pictorial views (same as above, and vertical-as-installed [inset]) where the owner manual's line drawing supposedly shows the composite spring's installed position...for which you claimed to find evidence. The "imprints" clock range position you mentioned is also indicated on both. Frankly, I just could not relate any artifacts on the handle axis nut (forget about Husqvarna's inept nomenclature-ing) to the "spring" (also a you'll soon see) as your post suggests. But, wait! I was looking at another chainsaw photo and... now I think I see it...let me point it out and add a pic below. (Be right back...) There, I amended the picture and posted it below.... And here's the other pic I was looking at as well....also with some additions. Ron, I now think you have scored a coup, and that all participants should immediately go back to post #12 and give you a GA Attaboy.
      • (1)

      • (2) It now appear my previous rebuttal might have been mistake (except the part about Husqvarna's inept drawing and part list nomenclature—and assembly break-down configuring as well); and that your observations are (almost) exactly correct—and, I've marked an additional "imprint" where the spring appears to have made, forget about that last statement and the black pointer and caption in the right-hand pic. Not only have you made an important discovery that explains why no amount of effort has succeeded in fitting the spring (back!) inside the handle; you have also, both, created and solved a heretofore unknown mystery! What I mean is, your observation has led to my uncovering the commission of a criminal act—one which I now am convinced is one of many such acts by the person/company that sold me the saw—and their modus operandi.... but I digress....
  • c) When I first was able to make out the markings in the picture, that decided me to pull out the saw and check first hand—remembering from earlier how difficult it would be to again re-assemble the brake assembly, I had deferred doing so until I could be reasonably confident of being able to reassembly it correctly...based on expertise from these CR4 discussions. It was when looking at the picture on the right (above) and at the saw (and both before and after re-disassembling the chain brake assembly (pic, bottom) that previously unseen picture (and possibly the answer to the main question) began to emerge:
    • i) After disassembling the chain brake assembly—this time removing the brake prime mover, the helical spring, first—yes, it made both disassembly and later reassembly much easier—I was able to attempt to match the larger helix of the composite "spring" (now recognized as a misnomer, as you will see....) to the imprints markings on the saw handle pivot axis nut (and to the Husq' drawing depiction):
      • (1) To my surprise the helix did not seem to match well to the markings on the handle axis pivot nut itself.
      • (2) Curiously, the smaller turn in the spring seemed a better dimensional, did this mean the nut was misplaced in the drawing? To find out...
    • ii) I began looking at the circular recess molded into the side cover of the saw itself (see picture above)—the recess which appeared not to have any function...other than to accommodate something of similar shape as the "composite" spring, either one of its helix turnings or its bend.
      • (1) The "larger" helix proved to be a good match, the bend almost as good.
      • (2) This still could not explain how the spring could fit there and also function dynamically with brake operation; i.e., why it was depicted as it was in the mfr drawing.
      • (3) It was at this time that it occurred to me that the imprint markings, if not consistent with the spring having been in full contact (there you'd expect a full-circle imprint, not partial imprints), might be consistent if the spring and nut had contacted each other only at an angle—such as if the spring (and its helix turning) had been leaning towards or away from the brake handle (nut)—such as if the spring was in contact, both, with main saw and handle such a way as to prevent it from "escaping" and being lost, even under high vibration saw operation.
        • (a) I decided to mock up the fully assembled saw configuration and see if a sensible spring placement could be found when all saw "subassemblies" were joined...and how the spring, if external on the chain brake assembly, might be retained to prevent its loss.
          • (i) I assembled a "chain brake assembly" using only the handle (shell), the cover with band (shell), the little brake actuation/release bolt, and a key from my multi-hex-key tool (it was handy, having been previously used to remove the brake handle) to "stand in" for the three-part brake axis pivot.
          • (ii) Fastening the mock brake assembly to the saw (with saw chain bar) mounting/tension-setting nuts, I then tried every conceivable spring positioning I could think of to find a "best" fit for the spring...and some way to "mount" it so it stayed in place.
            • 1. At length I was able to find a "best fit"... one in which the spring could be (more or less) securely "fastened" in place...but to what purpose? That remained a mystery.
            • 2. And the other end of the spring—where to "attach" it and how the spring might function.... at this point I decided to put it aside and revisit figuring out about the chain brake assembly...this time without the composite spring...if could be assembled to work.
      • (4) Since the assembled brake assembly had been made to work previously—after a fashion—to close (but not to open) the binder strap when the heavy-force helical spring was present, I decided to (try again) to change the only thing that can be changed: instead of atop the bifurcated spring I inserted the little brake linkage actuation bolt so that it would travel beneath the bifurcated spring when the handle is moved.
        • (a) Previously it had been virtually impossible to do it this way with the helical spring installed.
        • (b) Without the helical spring in place, it proved not only possible but fairly easy—even easier than installing the bolt above the bifurcated spring!
        • (c) Only one hitch was encountered...there were two positions (or ranges) along the bifurcated spring at which the bolt could be inserted, one which would and one which would permit full movement of the brake handle (more about that in a full procedure I intend to post after the end of this discussion, but for now...)
        • (d) Once all chain brake assembly components, except the helical spring and spring cover, were installed (with bolt in proper position):
          • (i) Testing showed the assembly to be working as designed through its entire motion range, for both opening and closing the binder.
          • (ii) The so-called "pop" (at the transition from brake-on to brake-released was also "observed"—the "pop" (with its connotation as something exploding or breaking [no pun] is better described in this case as a (palpable) barely audible "jolt"...or "bump"...but this could change with helical spring installed.
          • (iii) After repeated brake/un-brake trials it was decided to retry...ii)(3)(a)... but, before that, the finger-tight assembled brake assembly, set at brake off (handle back) was observed to be readily and easily fitted (and secured with bar mounting nuts), with no binder-strap-clutch-drum interference, at its "installed" position on the saw.
          • (iv) (The decision was made at about this time to reserve discussion about how the spring got inside the handle to begin with, for another, potentially off-topic, posting. )
          • (v) (The next test—repeating above steps ii)(3)(a)(i) & (ii) would finally reveal the almost certain "true" purpose and function of the (heretofore) "composite" (etc.) spring...and more errors in the mfr's manual's descriptive and pictorial documentation of the saw—and, inferentially, how it was these errors that led to all problems to begin with...
    • iii) The below photo shots of the trial "installation" of chain brake assembly on chain saw shows what appears to be the "official" correct fit. (Taken with only a flashlight beam to illuminate it, I have added pointers to indicate the (formerly called) spring in its nearly hidden position behind the "side cover."
      • (1)

      • (2) Note that in this position the "spring-like" object (inset) appears to serve the sole function of supporting the saw top cover—as an adjunct to the opposite side (shown as view A) and probably functions:
        • (a) To brace the otherwise unsupported right side of top cover.
        • (b) To prevent possible distortion of top cover induced by heat from engine/engine exhaust.
        • (c) As a vibration damper—to alleviate loosening of (say) the bar-mount/chain-adjust nuts, chain-tensioner, and such....
        • (d) Note also the errors in the mfrs drawing and parts list(s):
          • (i) Where the spring-like object is depicted 90° out of rotation, and backwards;
          • (ii) Where the same is depicted in the wrong drawing;
          • (iii) Where the part number prefix (symbolizing higher assembly) is ambiguous;
          • (iv) Where an accurate nomenclature would have read something like: "spring-form brace (or) strut...or simply, (say) brace [catalog format: brace, springform (top-cover-support)]. The original name being wrong in that:
            • 1. "Spring" has not relation to actual function—hence leads to confusion.
            • 2. It is not properly a "spring" that the term, spring, is reserved only to an item that functions as a spring (it serves to push something (by expanding from compression), pull something (by retracting from extension), or turn something (by twisting or untwisting)...the brace (as it shall henceforth be called) does none of these.
    • iv) So there it is: the original question now appears to be resolved; but is it actually resolved?
      • (1) The next step to find out will be to dismantle then re-assemble the chain brake assembly with the helical binder-actuation spring—which might entail fabrication of a tool as suggested by another (Justan as U recall) ; remount the assembly with brace properly installed; and restart and test both the chain brake and the saw.
      • (2) Also to be done is posting a reply to Just an Engineer's entry.
      • (3) I will post the final results (except for the accurate teardown and reassembly procedure) after completing (1) and (2). PLEASE, stand by.
  • d) Ron, you asked me to point out the "pin" referred to in the following linked passage:
    • (i) "I think it's a bad design on the post supporting the chain brake spring lever. ...(a little more than 1/8") pin ...only press-fitted into the aluminum sprocket cover. Impossible to reset this device if you remove the cover while the chain brake lever is engaged. I broke it...trying to compress the spring to refit the cover. ...I...modified it the way I think the original designers should have made it, by drilling out the broken shaft hinge [?] post, and tapping a 1/4 x 20 thread for a machine screw... ...hardened metal three-spoked spring lever had to be drilled to hinge on the new...screw. Then...assembled, securing the screw on...thread side with a lock washer and nut on the new hole that penetrated the case, on the outside of the case."
    • (ii) I pointed out the (what I sense to be) the corresponding pin above, in the lower-right-most frame in the picture at b)ii)(1)...the subject pin (elsewhere called "bolt" in these discussions) is circled in yellow. However, I note that the quoted speaker refers to a metal cover (quite likely on a metal saw), from which can be inferred that the saw might be much older, and possibly with chain brake assembly of different design and function. Naturally, we would think of newer, plastic-housed chain brake assemblies as mere derivatives (clones insofar as plasti-form fabricating allows) of metallic-housed predecessors. However this is something we (or at least I) cannot take for granted. As to the metal saw's applicability to this discussion, in view of the "discoveries" mentioned above, any similarity might now be a moot point. However...
    • (iii) It is interesting to see how that Husqvarna saw owner, too, appears to have gotten tangled up a bit by the poor nomenclature choices used in Husqvarna manuals—apparently some things never change.
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