Finally...The GS"B"

Discussion in 'Some Assembly Required' started by kellymac530, May 22, 2013.

  1. larryboy

    larryboy Chopper Rider

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    It's actually way undersized, the factory forks are just sliders...the suspension loaded the engine with the a-arm and the shock pushed almost straight up on the other mounts. We're basically putting a huge lever well forward of where it used to be.

    I'm still scared of Fabrice's bike and was terrified! of it until he added the extra struts. I wouldn't ride that bike personally, but that's a call we all have to make for ourselves.

    I don't think this is strong enough and somebody was selling these at one time;

    [​IMG]
    #21
  2. kellymac530

    kellymac530 motorcycle addict

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    Yeah those are engineered by a frame manufacturer and sold by Bert Dursmaa for a mere $2000
    Those are actually somewhat of my model I was going for here.

    I get what you are saying on the stock GS frame geometry, but the force is STILL upward on the shock mount point. The front steering neck still carries all of the weight and downward force from compression.

    The biggest geometry differences for me are lateral forces that are now transfered up to the neck that were on the A-arm before...hence the 2 extra braces. Then the next biggest force change the forward impact, say like running into a wall. That force used to be taken by the A-arm mostly as the fulcrum point and pulling on the rear stays.

    That Bert D frame you posted only mounts at the A=arm pivot point, and the front frame mount. I am mounted at both of those points, and the rear subframe mount points behind the A-arm mount and straight back to the rear subframe near the shock mount.

    I will watch all of the welds and stays closely, but I am quite sure it is enough, and by that I mean enough for anyone. I worry MUCH more about the swingarm shock mount and the trans case at the swingarm pivots than the front frame section.
    #22
  3. aposaric

    aposaric Garden mechanic ;-)

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    Looking interesting :-) Do you have a side photo of the whole bike? I am interested in the triangulation you mentioned aswell. Those aluminium welds look really great :freaky
    #23
  4. larryboy

    larryboy Chopper Rider

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    No, the steering neck never carried any weight before. Try this if you're game...take off all of the struts and loosen the bolt on the big aluminum section you have modified, then lift the front end by holding the bottom of the forks, notice that it rotates over on itself, then grab the aluminum section where the shock used to bolt on and notice where things move and how much. That's what I did when I built my frame. You have to remember that only half the suspension load was going up before, half was going down into the a-arm and into the engine at it's pivot.


    [​IMG]

    [​IMG]

    [​IMG]


    Ok, I won't fuss at you anymore...just want you safe since it sounds like you're gonna ride it pretty hard, plus you asked. :deal
    #24
  5. kellymac530

    kellymac530 motorcycle addict

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    No worries, It is not fussing. I appreciate the input.

    I do disagree on the force transfer.
    I did lift on the aluminum head with all of the stays off. It does rotate up and over itself. But it does not with the stays in place.
    As far as the weight transfer to the A-arm. I see rearward thrust, like under hard braking or hitting something the force is definately transfered to the A-arm. But on suspension travel upward I see it as all of the force is up into the shock pocket just behind the steering bearing. That is the only place that pushes downward on the front wheel.

    I see it as I have 3 more anchor points than that Bert D frame head. The small one on the bottom pushes forward on the steering head which prevents the rolling up over itself already {I would never rely on that low pivot alone though}. Then middle stays that come up from the A-arm pivot and are much farther apart at the base than the OE rear stays, so those add some preventing of the fold back, but more protection of side to side movement {imo limited as that may be}. Then lastly those more horizontal top bars prevent any movement.

    I am definately no engineer, but I did stay at a Holiday last night....does that help :lol3
    But seriously, I am a carpenter, primarily metal stud framing, and that multiple angles design is similar to what we build and hang ALOT of weight off of everyday with soffits and cantilevered store fronts. Fabrices bike was still on the road last time I heard from him and I have more triangles and supports than him. I will add some trussing like yours if I see there is any movement or tweeking at all. I have to start off riding very mildly anyway and only street riding at first since I am still healing.

    Any other ideas? :ear
    #25
  6. icekube1

    icekube1 Middle aged git

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    I think Newton's 3rd might say different.

    Or maybe not. :dunno

    Good luck with your build. It looks interesting.
    #26
  7. kellymac530

    kellymac530 motorcycle addict

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    Am I missing something in my understanding of Newton's laws?

    If you take a BMW shock out of that pocket on the front head the bike drops down. All of the support falls on the shock. The front shock is suppoerted by the steering head casting.

    The telelever system I removed that Larryboy says carries weight is nothing more than a hindge. The weight is sitting on the on the top of the shock. Unless I am missing something on that also.

    BTW, at least imho, anyone who believes 100% in Newton's 3rd has never personally watched a skydiver hit the deck without an open shoot. I have, there is NO opposite reaction. I realize that there is some reaction, but the stepping off a boat logic does not apply to a body hitting the earth at speed. That was not a fun day. :eek1
    #27
  8. kellymac530

    kellymac530 motorcycle addict

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    Larryboy,
    I keep re-reading this post:
    No, the steering neck never carried any weight before. Try this if you're game...take off all of the struts and loosen the bolt on the big aluminum section you have modified, then lift the front end by holding the bottom of the forks, notice that it rotates over on itself, then grab the aluminum section where the shock used to bolt on and notice where things move and how much. That's what I did when I built my frame. You have to remember that only half the suspension load was going up before, half was going down into the a-arm and into the engine at it's pivot.

    And I keep looking at my frame, moving parts up and down, and I am really dumb or I am missing something {maybe because I am dumb}.

    I am not argueing with you, I respect you a ton and love your frame you built. Think of this as more of educating me..:lol3

    On the stock Telelever front end the bike sits weighted on the front wheel, agreed?
    The path of support that I see is: bottom of the wheel, front axle, fork tubes, ball joint, jumps back a bit to the bottom of the shock, through the shock spring, to the top shock mount, to the front frame head.

    Where does the weight transfer to the A-arm? {other than that 2" or so part between the ball joint and the lower shock mount}

    I am wondering if we are just seeing it differently because of the engine being a stress member...oilhead BMWs hang the rear suspension and the front suspension separately and are both stressed off the motor.

    You asked me to try an experiment if I was game, I can not do that test anymore cause I am welded up and assembled, but on a stock BMW Telelever if you removed thosen 2 rear stays and dropped the bike down on the wheels, the steering head WOULD then fold back on itself, up until it bound up anyway. The only thing stopping that is those 2 rear stays triangulating the front neck.

    Help me see what I am missing.
    #28
  9. DRjoe

    DRjoe Long timer

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    Well going by that theory then if you disconnected the tellerlever wishbone thingy your bike will not fall down because your shock is taking all the loads.
    #29
  10. larryboy

    larryboy Chopper Rider

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    Agreed.

    Let's start at the ball joint, that's where the load goes into the a-arm, the shock picks up a percentage of the load...there is a ratio in there and that's why the a-arm mount is huge, the load is getting multiplied by the shock mounting, a bridge engineer could explain it to us better I'm sure. IMHO, this is how they can get away with the wimpy upper mounting of the shock, I know I said "half" the load is up top, but it might actually be a smaller percentage...maybe 30% or so, think of the lower shock mount as a teeter totter...if you're old enough you'll remember the old teeter totter's that let you change the fulcrum and launch your step-brother to the moon. :lol3


    That's why I stress out when we hang a set of forks well forward of where the load used to be. I tried to build my frame off of what KTM does on their big bikes...truss frame over a stressed engine with standard forks, I would have done better given more time, but I feel that mine is safe and the rest that I have seen aren't.
    #30
  11. kellymac530

    kellymac530 motorcycle addict

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    Of course it would move some. That telelever is a hindge. Remove the mount bolt through the block and it can swing forward and rearward which would let it move some. But it would not drop all the way down. The majority of the weight would still sit on the shock and the steering head.

    Larryboy,
    As far as remembering a teeter-totter, yes I do. I think I am older than you even :cry. I will be 50 this year.
    As I see the large A-arm bolt, yes it does need to be large but not for compression of the suspension. I agree, there is a % of weight that is transferred to the A-arm since the shock is mounted in back of the ball joint so there is a teeter totter effect as you state. But the distance between the A-arm pivot and the shock mount is much more than the the distance from the ball joint to the A-arm. So the % would be 20-30% on the A-arm pivot and 60-70% on the shock mount/steering head.

    Then when the suspension fully compressed, as in bottoming out, which I did many times on the RT, the force is DOWN on the A-rm pivot bolt and the impact still hits full force on the upper shock mount, I even see it as MULTIPLIED on the upper shock mount since the fork ball joint is in front of the shock giving it more of the leverage you speak of in a seesaw.

    I see the need for the large A-arm pivot bolt being primarily for braking and side loading. When you hit the brakes or run into a hard edged bump, like a deep pot hole or a parking bumper, the forks try to push rearward. The the impact is into the A-arm pivot. Then also when the bike is leaned into a turn and the tire is side loaded, there is a hidge effect again since the top of BMW forks are not solid mounted in the upper TC and there is no lower TC. That load sideways is taken by the ball joint and transferred to the A-arm pivot bolt. I have added a much longer steering neck tube, a lower TC, tons of thick plateing and gussetting, a support brace from that same A-arm pivot bolt to the lower portion of the head support and up to the rear of the steering head.

    I know of a couple of people who have used that Bert Durssma frame and it is MORE than strong enough. it is engineered, tried, tested, and strong. That frame mounts at the A-arm pivot and the rear stay mounts, I have a 3rd mount point about 5-6" farther forward of those points where the stock steering head mounts...

    I honestly see it as AS strong or stronger than those Durssma frames.

    I am going to give it a try and if it is flexy or sketchy at all I promise I will fess up and post that.. If it is that way, then I am going to pop on that Durssma frame later.

    If it si so weak that it shatters, win win win. 1} You would be proved correct. 2} I would likely fly over the front and break my neck and the titanium plates and screws would sever my spinal cord and I am dead...no more pain and suffering. 3} I am well insured and my wife and daughter would not have to work or deal with my idiot ass anymore....everybody wins. :clap

    I have had it on the wheels and jumped up and down on the bike and so far it feels solid with no give or flexing. I will keep you posted.

    All of the challenges of my engineering or the lack there of are at least making me stay very conscious of it and are a positive thing, so keep that up. I appreciate the ideas. Extra eyes are always a good thing.

    How about the pipe?
    the seat?
    any other stuff?
    #31
  12. larryboy

    larryboy Chopper Rider

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    Like I said before, your design, Fabrice's, that Burs frame...they're probably all safe, I don't like any of them and won't ride any of them.

    At a minimum I would add the yellow bar I drew in...that's just me. It's not a win if the bike snaps in half and you get hurt, that's why we're here talking about it...I don't want you to get hurt.


    Pipe, I prefer the cat down low and no muffler. I had a Buell, really liked the pipe underneath. It makes matching hard bags look so much better.
    #32
  13. kellymac530

    kellymac530 motorcycle addict

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    One of the biggest concerns people had when this build started was the lack of heavy springs available for the KYB forks to compensate for the extra weight of the Beast.

    I have not ridden it yet, but so far the .50 springs I put in and the 5/8" spacers seem on the soft side, but quite doable and seem reasonably balanced with the rear shock just when standing on the pegs and bouncing....that said, I realize it is something I may have to address after some testing. So with that in mind I have been reading alot on the air forks on the new Crf450R and KX450F. I am really curious about just adding some nitrogen pressure to the existing forks to add some "air" spring rate to what I already have.

    Here is a simple diagram of what they used to use and what they have now:

    http://www.motorcycledaily.com/2012...es-from-kawasaki-and-honda-get-new-air-forks/

    There have been tons of bikes that have used and air over coil spring suspension in the past. I have had a few bikes in the past with that set up. I understand that there are other problems that arise like stiction on the seals, or blowing out seals, and the usual fluctuation of pressure with heat build up causing the raising and lowering of spring rate, but, it could be a viable option for at least some air assist...what do you guys think?

    Also, I have made alot of progress in a few areas. I finished the rear subframe and fender support. I mounted the tail light. I got a different front fender to match the rear...both the old KTM pumpkin orange not the typical newer KTM deeper orange.

    I am still stuck on the clutch lever!!!! A real pisser. The BMW uses a 10mm cable end and most other bikes use an 8mm end...thought I solved it by customizing an 8mm cable end to fit the cable...nope, standard dirt bike levers use a different pivot distance between the pivot bolt and the cable end so the Moose lever and perch do not pull the cable far enough to dissengage the clutch totally...pissed again. So now I decide to just use the BMW perch...nope, the clamp is a single pinch bolt style and not a cap type clamp and my bars are knurled and the perch would not slide over the knurling....gently slid a screw driver blade in to spread the clamp...SNAP, broke it off. Tons of grinding, cutting, fitting and I made a special clamp out of the Moose perch clamp and the BMW perch...it works....doooohhh, too wide to use after market dual sport switch controls and will not allow the use of the OE BMW switches now because of my clamp mods....I now think my head will explode....more cutting and fabbing and I can make my Baja Designs style controls work with the modded BMW perch, but barely and I am slightly worried on the strength in a dump....any ideas on perches and levers that have the longer throw and possibly the 10mm cable end but clamp on the bars like a dirt bike????????
    :ear
    #33
  14. gots_a_sol

    gots_a_sol Been here awhile

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    Cannon Racecraft could probably make you up some custom springs. I had them make up a set of 50's for my mini-moto as the highest rate off the shelf was 38.
    #34
  15. kellymac530

    kellymac530 motorcycle addict

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    Got my seat rebuilt, leather sides and rear seat with suede front. I got all of my wiring sorted out and hooked up...PHEW what a nightmare.

    Tank all welded then sealed up. Fuel pump installed and hold down mount built.

    Replumbed the oil cooler. What a PITA. Metric oil hose is just not available here in the US and neither are any fittings. I did finally find flexible 3/8" copper tubing is a good snug fit in the OE BMW oil line {12mm I believe}. So I picked up some and a few elbows and street 90*'s {male one side/female the other} and soldered up some hardline with rubber hose as the couplings. Works great, sheds heat, looks wierd {oh well} and is holding great because I used a air hammer with a point chisel on it to give the ends of the street elbows and hose end connections to flare them slightly so the hose and clamps can grab on better.

    I fired her up and rode her around the block. The frame is VERY stiff. I have no concernes with my frame work at this point, I will continue to watch for stresses and fractures or bends, but it felt very solid. I may have gotten the fork rake a bit steep because the steering feels SUPER light. Like dirt bike light or more. I will have to see if there is any head shake or twitchyness as I increase my test ride speeds. It may require a steering stabilizer/dampner, but it felt fine at moderate speeds.

    The brakes....yeah that was a known issue that I have not yet addressed and WOW does it need to be. I might as well have just dragged my feet.

    Suspension: Surprisingly good. It feels well balanced, does not dive excessively under what limited braking there is and it does not feel harsh mushy. I have not propperly tested much, but it is a good starting point anyway. One wierd issue I have never had before, maybe you folks can help figure it out. Under braking or any compression of the forks there is a wierd moan or wheezy sound on rebound. Any idea on what the heck that could be?
    It is possible it is in the brake somewhere, but it sounds like the forks. I can make it do it sitting still, holding the brake and compressiong the forks, but I have been alone here for a few days so I can not get down and listen while someone else compresses the forks...maybe my buddy will come by on wednesday and help me out.

    Of course to fire it up I sorted out my wiring. Got everything connected and realized the wiring harness is way too long coming out of the big old fairing. I had to cut all of the wiring and shorten each one. I soldered each connection carefully, and used the good thick clear heat shrink tubing on every connection. Then oddly my dash panel stopped working. When I turned on the key, my low fuel light and neutral light would not light up until after I started the motor....rut row.

    Cut open all of the wrapping I had done and tested all of the plug connectors, good. Tested all of my new connections..good. Then started looking closer....dooohhh.!!! There is a green wire with 2 brown stripes and a brown wire with 2 green stripes....barely discernable to the naked eye and you guessed it, I had swapped them backwards. Reconnected them the other way and dash lights are back...:clap

    Final issue so far is I still have the knobby tire trhat came on my YZ frontb wheel. It is a dirt only tire, it is old and very dry with a few splits and missing side knobs chunked off. It is a sand tire so very spread out knobbies and it just does not stick when turning tighter on the street....gotta go immediately. TKC80 coming asap.

    I also made a small adjustment in my steering stops. The Yamaha triples and the Honda neck were different spacing and it did not have enough angle. I just ground a small notch in the neck and gained quite a few degrees more turning angle.

    So far so good though and nothing too unexpected. So far I am really stoked on the progress. 4 months or so from tear down to first ride and all while I am in recovery and only able to work a couple hours a day...I feel good about it.:freaky
    #35
  16. larryboy

    larryboy Chopper Rider

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    What's the rake and trail? :ear


    I just ordered new springs for mine, .76 front and 18.9 rear, time to hit some sweet jumps. :evil
    #36
  17. kellymac530

    kellymac530 motorcycle addict

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    I set it up to be about the same as a KTM 525 exc which is 27* and the stock YZ 450 forks is set at 26.6* I believe so that was my goal, set it between 26 and 27* which would put trail at the stock YZ point, about 4-1/2"...
    But with the heavier weight and a bit more sag that the stock YZ runs it is at about 25* rake and 4-3/4" trail.
    how bad is it?
    :ear
    #37
  18. larryboy

    larryboy Chopper Rider

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    That's what I shoot for on my custom builds...perfect, you're probably just feeling how easy the 21" tire knifes around compared to the 65 pound 19" that was on there.

    :thumb
    #38
  19. kellymac530

    kellymac530 motorcycle addict

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    phew, that is good news.
    Mine never had a 19" wheel. Mine had a 17" cast wheel. My starting bike was not a GS like yours it was an RT.
    I am hoping, and now more confident that the knifing under is the really bad front tire. But there is a TKC80 sitting in the garage. It will be on tomorrow morning and we shall see.

    I swapped out the front brake master cylinder to the stock RT one...I doubt that will fix much, but worth a try. It is much larger bore and it was made for 8 pistons and ABS...so it barely moves to compress the 2 piston caliper now...:lol3

    Has anyone been able to mount a 4 piston caliper on a 21" wheel? I read somewhere it had been done but can't find it now. The 320mm rotor takes the caliper pretty far out on the spokes so it might work. Next up is the big rotor and caliper bracket.
    #39
  20. kellymac530

    kellymac530 motorcycle addict

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    Put a couple more miles on it today....:clap each ride I have been adjusting the little things a bit. Keeps getting better.
    I pulled the brake line out from under the fork leg, YZ ran the brake line down the fork and looped it under the axle. Alot of people swap them out to a shorter brake line like the Honda CR uses and the newer YZs run. I left mine stock length, but routed it straight up and inside the fork leg so that I could get more slack at the top. I used the slack to run the line infront of my new headlight. The longer line worked because I am using the BMW MC for now and the banjo is on the bottom so I angled it forward. :evil

    I have finished all of my wiring, and some temp front turn signals. I put on a TKC80 front tire but I had to use a HD front tube for now....I am interested in a tubless rim...but I know those are still a dream. Then I thought of a Tubliss system, but I am not sold on them and I worry that it will not seal well on the inner lip of the TKC80, it has a angled row of ribs all the way around the inside of the bead area and that is where the Tubliss seals...:huh

    The tire made ALL the difference in the steering.:D The sketchy steering was the rock hard old tire with missing knobs. It would kind of skip when turning and I was worried it was too steep and knifing under, but now with the tire it handles smoothly, turns great and is no longer sketchy. I played for a while just doing figure 8s in my street at slightly increasing speeds and it felt great. Balanced and even in both directions. Tracks straight. I am actually really proud that my home engineering and jigging seems to be dead on. :eek1 :lol3

    I still need to make the cap for the fairing front, Desierto style but homemade. I need to finsih straightening the dent in the tank and spray it black which I already have the paint for. I plan on having a grahic set made for the tank, but that is later and only if they can match my plastics color...rare orange these days. :ear

    Anyone have any better ideas on the brakes?
    I am ordering a 320mm rotor kit, but I do not think that is gonna be quite enough. The 20mm MC is TOO much. The 11mm YZ is too small {I think} and the caliper is just not enough. I am thinking a 14 or 16mm supermoto radial style MC and that 2 piston Braking caliper that JTH runs but I REALLY would like a 4 piston caliper....:ear
    #40