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Pitbull TRS twisting swingarms ?

Discussion in 'General' started by DBConz, Jan 4, 2021.

Page 5 of 8
  1. Mongo

    Mongo Administrator

    :crackup:

    I've got better stuff and worse stuff in announcements if it helps :D
     
    Mongo, Jan 5, 2021
    #81
  2. ekraft84

    ekraft84 Registered User

    All kinds of fun schedule stuff I'm sure. Just don't ever run Grattan CCW again, okay ... :crackup:
     
    ekraft84, Jan 5, 2021
    #82
  3. Mongo

    Mongo Administrator

    Currently you are in the majority on that one so you're good to go :D
     
    Mongo, Jan 5, 2021
    #83
  4. Phl218

    Phl218 .

    Jeff had his plate come out of the floor thanks to the dip in the turn 200 yards before entering Barber. luckily the R6 landed to the camper call side, not the open area where it would have landed on the floor.
    but his plate was also installed by the guys who prepped his camper, so they just drilled a wood screw through the sub floor.
    we ended up cutting the tarp underneath and adding a 2x6 under the bolt hole for the proper bolt to go through and taped it back up.
     
    Phl218, Jan 5, 2021
    #84
  5. Mongo

    Mongo Administrator

    Is that one of the initial 2 bikes mentioned? If so that sure as hell has nothing to do with TRS or the instructions :eek:
     
    Mongo, Jan 5, 2021
    #85
  6. Wheel Bearing

    Wheel Bearing Professional low sider

    Bet you wouldn't bend any swing arms if you had foot anchors installed on the bike.
     
    Wheel Bearing, Jan 5, 2021
    #86
    BigBird, 969, TurboBlew and 2 others like this.
  7. stangmx13

    stangmx13 Well-Known Member

    Thats not a valid comparison. The forces are very different when something is constrained vs unconstrained. Say u were trying to bend a metal post by hitting it. Itd be a lot easier to bend if it were concreted into the ground. Itd be a lot harder if it was free standing.
     
    stangmx13, Jan 5, 2021
    #87
  8. stangmx13

    stangmx13 Well-Known Member

    This is the solution to never bending a swingarm with the TRS - make sure the floor is weaker than the swingarm.

    Or you could prevent the front tire from moving laterally, say with a wheel chock.
     
    stangmx13, Jan 5, 2021
    #88
    BigBird and Phl218 like this.
  9. Mongo

    Mongo Administrator

    Ummmmm, yeah, if the rear tire isn't constrained to the ground we call it a highside....

    But I do understand your point, mine is that you guys are all insane if you think the weight of the bike is going to bend a swingarm in the instances described when it has not as a trailer has barrel rolled down the road in an accident :crackup:
     
    Mongo, Jan 5, 2021
    #89
  10. Mongo

    Mongo Administrator

    How would that do anything to prevent stress on the swingarm? The situations described is the bike flopping side to side not the front tire moving.
     
    Mongo, Jan 5, 2021
    #90
  11. tophyr

    tophyr Grid Filler

    Haven't read the whole thread, but I can easily imagine this happening and it's also not gonna put me off using TRS, that mount is a godsend
     
    tophyr, Jan 5, 2021
    #91
    cBJr, BigBird, 23103a and 3 others like this.
  12. stangmx13

    stangmx13 Well-Known Member

    Given the same magnitude for trailer acceleration*, flopping side to side is likely a much smaller force on the swingarm than the front tire moving laterally. The lever arm to the CoG is far shorter for flopping. Id guess the comparison is 6" vs 36" because flopping is vertical distance and the other is horizontal. And Id bet TRS arms are weaker in the direction needed to allow the bike to flop because the arms only need to twist a little. So the TRS twists and the swingarm doesn't.

    IMO, worst case scenario for bending a swingarm in the TRS is setting the front tire on castor wheels, making the TRS floor mount bulletproof, and fishtailing the trailer. The mass of the motorcycle swings laterally with minimal friction with the longest lever arm possible. You'd kinda get this in real life if the front tire is allowed to bounce. A wheel chock or strap on the front end would solve that.

    *Of course, we have no idea what realistic trailer accelerations are. A big pothole will put some amount of flopping acceleration into the trailer... but its on springs so its probably not that fast. Producing large lateral acceleration for the motorcycle depends a lot on where its mounted in the trailer and a bunch of other things. Id guess you'd need a crash or violent fishtailing like others have described in this thread.
     
    stangmx13, Jan 5, 2021
    #92
  13. RRP

    RRP Kinda Superbikey

    If you're going to make sense, yer gonna have to leave...:D
     
    RRP, Jan 5, 2021
    #93
    tophyr likes this.
  14. badmoon692008

    badmoon692008 Well-Known Member

    The bike cant move side to side if both ends are constrained I think is the thought.
     
    badmoon692008, Jan 5, 2021
    #94
    BigBird likes this.
  15. baconologist

    baconologist Well-Known Member

    Rotella is the best oil!
     
    baconologist, Jan 5, 2021
    #95
    969 and TurboBlew like this.
  16. Mongo

    Mongo Administrator


    Huh? My Hyper had the front tire free to move laterally and guess what, it spun on the steering head. Lots of potholes and enough bouncing in the back of the pickup that the rear tire dented the tailgate. Someone also might have even taken many a corner at relatively fast rates of speed on and off road putting a lot of load on the bike and the TRS. Swingarm is still fine.

    If you're talking about the entire weight being pushed laterally at the level of the axle directly parallel to the floor then cool, a chock would help some. Wouldn't help a bit for the forces pushing laterally at other angles though. As for your casters idea, the front wheel already has the ability to move that way, it'll go to full lock one direction and then the only thing keeping it in place is the tiny amount of friction caused by the weight of the front end on the tire. Oh yeah, and the strength of the swingarm and it's mount to the bike. If potholes could bend swingarms in the TRS then every racer who has ever used one would have a bent swingarm.

    Still a moot point, nothing described in the initial post would bend a swingarm on either bike described. You can hypothetical anything to the breaking point but yet one more time, when bikes have been hanging by a TRS and nothing bent, when bikes have barrel rolled with a TRS and nothing bent, you can't hypothetical into blaming the stand for these. Just doesn't work.
     
    Mongo, Jan 5, 2021
    #96
  17. Mongo

    Mongo Administrator

    Bike can't move side to side with the rear end constrained either (it can slightly with just the front). A front chock also would do a thing for any force applied at say the bar or tank level.
     
    Mongo, Jan 5, 2021
    #97
  18. noles19

    noles19 Well-Known Member

    It might not blow a fork seals, but tying it down too tight will make it pop up really fast and hit you in the face when you undo it, or so I'm told I'd never let that happen of course...
     
    noles19, Jan 5, 2021
    #98
    BigBird, 969 and badmoon692008 like this.
  19. stangmx13

    stangmx13 Well-Known Member

    Im not sure that you actually understood my post. The castors has nothing to do with the steering head rotating. They were to allow the whole bike to swing laterally a bit easier, actually to rotate around the TRS. Well, they were there to make it easier for someone to visualize that motion. You keep saying that the bike cant swing that way.... well, it will when the swingarm bends, which is the point of the thread.

    Im also not sure why you keep bring up potholes when I said thats not the worst case.

    A few anecdotes of something not bending in a trailer incident does provide any data that its not possible in another trailer incident. The OP said blowing a tire and swerving the trailer. I already suggested that swearing a trailer is the worst case, especially if its violent enough to bounce the front tire off the ground. And who knows what else happened when the tire blew.

    You dont need to use my words to blame TRS for anything. Im practically speaking in "free body diagram" and we will literally never know if the TRS caused the bends from the OP, so its silly to blame anything.
     
    stangmx13, Jan 5, 2021
    #99
    badmoon692008 likes this.
  20. baconologist

    baconologist Well-Known Member

    Anything is possible.....
    But in the 100’s of thousands of miles towed with TRS systems. This incident is what engineers and statisticians call an outlier.
     
    baconologist, Jan 5, 2021
    #100
    TurboBlew and lopitt85 like this.
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