An 800's Rebirth/The build of MechanicO

Discussion in 'Parallel Universe' started by FinTec, Dec 12, 2014.

  1. Motomochila

    Motomochila Moto Scientist and time traveler

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    The 4860's have 300 mm of travel. Are you considering sticking with that length or lowering down to around 250? Reason for my question; I just picked up a 2015 800 adventure and the first "real" mod is suspension upgrades. I measured the 4860's from a set I have laying around and want to go this route but wonder if the increased length on a new rear shock to match the increased length would cause too much angle on the swing arm. That rake angle would potentially cause too much twitchiness as well, but having a 300 mm travel GS would be schweeeet. I converted my 690 to 300mm from the stock 250 without changing the rake so no problem there. The difference in suspension performance was fantastic.
    #41
  2. Dansrc51

    Dansrc51 I need a cape....

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    Excellent build thread and well thought out. I love to see alternative takes on bike builds using hand built parts rather than off the shelf.
    #42
  3. sarathmenon

    sarathmenon Armchair Adventurer

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    If you go from 270 to 300, your rake should increase by .5 degrees and trail by 8mm (rough math, haven't had my coffee yet). If anything, your bike will be more stable on the road and slower to turn into corners - this again will only be a slight change over stock. I'd be more concerned with the higher centre of gravity, which again is probably going to be minimal. Also, the stock setup eats head stem bearings at a very regular rate, raising the front end will worsen that.
    #43
  4. Motomochila

    Motomochila Moto Scientist and time traveler

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    Thought of that issue. By raising the rear, the angle should move back to almost stock rake and trail except for the different offset on the 4860's. I think they are a bit further out., (.50 I think). The issue I need to consider is the steeper angle of the swing-arm due to the taller shock. the front, stock at 231 mm, (9.1"), and the rear at 215mm, (8.5") could effectively be converted to 300, (11.8") up front and 275mm in the rear, (10.8"). The higher center of gravity wouldn't cause much issue but i wonder if the 2 inches of rear travel on the swing arm would cause too much stress or chain misalignment.

    As Fin333 starts his suspension build using the 4860's I'll be curious to see his calculations and results. Hope he does it soon since the stocker's tend to slug about in the rough stuff.
    #44
  5. FinTec

    FinTec Been here awhile

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    sarathmenon: ha, red-neck engineering! Yea, when it comes to the front end of a motorcycle, I cannot even comprehend taking a short cut. You can have a front wheel on a car fall off and you will most likely just skid to a stop. On a motorbike? Yowza!

    So what I did on the design of these triples for safety was take the stock ones and just make sure I was "more". I measured all the wall thicknesses, rib thickness, heights, depths, etc. Then I make sure my design does not go "less" than these stock dimensions. Sure I could have done some crazy FEA analysis, remodeled it so cut a little material off here and there for weight, but is .25 lbs extra worth the front end staying on? Yes it is. Also as I mentioned before, I am using 6061 T6511 aluminum. Excellent material and probably 30% stronger than the cast aluminum they use. So my conclusion on the design is it is as strong if not stronger than stock.
    #45
  6. jengel451

    jengel451 1 Cool MotherF#$cker

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    In raising the rear, you'll increase swingarm angle, which will put more pressure on your Swingarm pivot from the chain under power. Nothing that you really will notice on this type of bike, but you'll really need to keep an eye on the chain slider for excessive wear, and if you go down one tooth on the front sprocket, it'll compound that issue.

    I don't think you'll have to worry about anything else since the bearings won't really care what they are doing.
    #46
  7. FinTec

    FinTec Been here awhile

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    Motomochila: To change the travel of the 4860 I have, you just need to change two things, one aluminum spacer and the springs. Most places that sell the springs also have those spacers to change the travel. Here at the ones I made:

    [​IMG]

    Cannot remember what the fork had in them but I made a 30mm spacer (as seen in above pic). And I used 465mm springs (58kg).

    So my total travel is now 9.8"(250mm). Stock height in front is 9.1" so I increased it .7". However, I am converting the rear to 18" wheel so rear height now goes up .5" (I know this is rough estimate). So in the scheme of things, I am almost matched front and rear now.

    It will drive you crazy trying to account for all variables though. How much sag? What happens to the rake when the front end is compressed and the rear is not? Or goodness knows what is going on dynamically with the geometry while in motion. The one that gets me is when you brake, the front end dives, now you have less rake, now the bike is twitcher. Right when you need it to NOT be twitcher (i.e. trying to stop fast). So all you can really do is pick some of the factory "static" data points and try to keep those as they have probably done some work to make sure that is a good compromise.

    That said, I did change the offset to speed up the steering and glad I did.

    And I do want to run a longer travel rear shock (say 9", stock - 8.5") and then I'll re-spring and spacer in the front to 10.6" (270mm) of travel and call it a day.

    Motomochila, in my opinion, you really only have two constraints to do what you talk about: can your legs handle the height and is the front and rear matched/balanced? If you can do these two things I say go for it. You can check the chain tension for the extra travel when you have the shock off. Let it sag all the way down to the new point and see if the chain binds. If not, green light. At 10.6" in front and 9" in rear I will be at the limits of comfort for my 6' 1" height and 34" inseam. How tall are you and inseam BTW?

    Now lets talk about dropping those darn foot pegs .5" to .75" down. Now we are talking.......
    #47
  8. Scubawerx

    Scubawerx Scubawerx

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    Forget football, this guy's "building" a bike! I'm watching.
    #48
  9. Motomochila

    Motomochila Moto Scientist and time traveler

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    6' 1" here too. But I'm an expert rider off-road and tend to use up suspension real fast. I down graded from a GS 1200 Adventure with custom Race-Tech suspension, to go with a more dirt oriented GS800. Already far happier with the ergonomics, but the suspension lacks. As you do your build, I will be interested in how the KTM swap with longer rear really works. The triples you made
    are awesome. No capabilities myself for CNC machining. I will have to pay someone with your talent to do this for me.....that is, if your end result gives you the desired results. In the mean time, I'll just bang the rough stuff on my 300mm suspended 690.

    Subscribed my friend.

    Jerry
    #49
  10. dirtysouthjacket

    dirtysouthjacket Been here awhile

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    I think you said earlier in the comments that you were going to mess with the rear suspension later.

    I give you 2 trail rides, before you start planning your rear suspension upgrades. :D

    After I improved the front end with the Shiver conversion, all I think about is the ass of the bike bouncing around trail behind me. Its much more obvious that the rear is barely keeping up now that the front is squared away.

    Great work btw. I have also looked hard at the auctions for GS's. I might go for a F700 for the SO in another couple of years.
    #50
  11. FinTec

    FinTec Been here awhile

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    dirtysouthjacket: ha, I figured that was going to be the case. I definitely see where these WP forks are going to be vastly better than stock and then the rear will need to "catch-up" so to speak. And to confirm it from a guy like you who has been here, make it more the priority. The only real reason for putting it off for now is it is a plug and go event and I am trying to do what I can now to at least get him running. But trust me, rear shock is on the list.

    So now to the lower clamp op1. Nothing really different to see here as it is very similar to the uppers in its operation, just different shape and features.

    Just making sure it is going to fit

    [​IMG]

    Cut the big holes

    [​IMG]


    This was a lot of cutting off the top. Bit hard to see but what you are looking at are the built-in stops for steering.

    [​IMG]


    Now cut the outer profile

    [​IMG]


    And here is the upper and lower after op1 on each.

    [​IMG]


    Another note is on the upper you'll notice there are raised bosses for the bar clamps. I did this to include 1 cm of built in ride for the bars. I am still going to have risers but it was easy to add 1 cm here and now during cutting these.

    Op2 is next where we cut the underside of each of these.
    #51
  12. FinTec

    FinTec Been here awhile

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    To do op2 on these I need to machine the aluminum jaws on the vice to accept the odd shape of the part as we are not dealing with a square anymore. You can just see in this picture how there is a large radius on the far jaw to accept the radius of the top clamp center section. I could just clamp with flat jaws and hope for the best, but two things: it puts little flats spots on your part and it may move while be machined. Again, I only want to make these once so I took the extra time to machine the jaws.

    [​IMG]

    Now you see the upper sitting in the vice ready to be cut

    [​IMG]

    After material removed

    [​IMG]

    Now using an EM do all the inside cavity work

    [​IMG]

    Some drilling and tapping and done

    [​IMG]

    The upper and lower done with op1 and op2

    [​IMG]
    [​IMG]

    I am a fan of taking off the corners on my parts. hey, I've go it on the vice already and located, just run a nice 1/8" radius corner EM around the part and it looks SO much better and clean. I am amazed at how many "expensive" parts I get and they cut this corner (no pun intended).
    #52
  13. FinTec

    FinTec Been here awhile

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    So took the upper and lower that are NOT done and assembled them with the 4860 WP fork. This can also ruin your day. This is where you find out you made a mistake: holes not aligned right, upper and lower holes not concentric, holes too small, holes too big, etc. Studying the stock parts I see that most triples run a pretty close tolerance with the bore for the fork uppers. Too small, and you aint going in, too big and you have to clamp down hard with the bolts to get to hold, if it even holds. So I shot for .001" over the diameter of the fork.

    Slipped in like a glove (and not OJ's glove)

    [​IMG]
    [​IMG]

    Very happy with the results so far. Now just need to do the final smaller ops on the triples and then we make the steer tube.
    #53
    mrsdnf likes this.
  14. UpST8

    UpST8 turnin gas to noise

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    awesome stuff! I'm in :lurk
    #54
  15. Captain Excellent

    Captain Excellent Stay weird, or you'll be normal like everyone else

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    I was running your design geometry through my mind the other day, in particular the increased offset you've created on the upper clamp. Given a fixed axis for the head tube, as you increase the offset of the upper clamp, that would for all intensive purposes rotate the angle of the forks about a centre point in the plane of the lower clamp. Given a .001 tolerance on the cut out for the fork tube, how did you ensure the angles would all align? Was that all coordinated in the Solidworks? It would be a very subtle angle, and since I don't know much about CNC machines I'm curious if it was able to accommodate that angle.
    Great work. It's refreshing to see a thread with some real content here. Not another banal "oil" thread. I'm obviously signed up for the full saga.
    #55
  16. FinTec

    FinTec Been here awhile

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    Captain Excellent: Ah, I think I did a poor job of explaining the offset change. This offset was done on BOTH the upper and lower, not just the upper. You are correct, if just done on the upper that would be some crazy geometry/math and goodness knows how it would affect the handling. You would be changing the rake, but this changed rake would follow the fork as they rotate and not stay in plane with the frame/headtube. Makes my head hurt trying to envision it :eek1

    So I just did not include the drawing of the lower as that is implied they will be the same. Hope this make sense.
    #56
  17. Captain Excellent

    Captain Excellent Stay weird, or you'll be normal like everyone else

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    Ah, so with a uniform offset, no change in angle, just a change in the fulcrum from the axis of the head tube. I'm going to have to do some reading about bike geometry to understand why this would make a difference.
    #57
  18. wipe-out

    wipe-out Been here awhile

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    :velvt I'll take a pair please! Anodized in red? Awesome stuff!
    #58
  19. doc4216

    doc4216 Chronic High Fiver

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    This is awesome! I love seeing builds like this. I essentially would have to buy everything or make new friends real quickly!

    Great job so far. I can't wait to see it when you're finished.
    #59
  20. Garball

    Garball Ex Stromrider

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    This is better than reading a book over the Xmas holidays. Awsome.
    #60