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Softer damping will help prevent shock shaft bending

Discussion in 'HPI Baja' started by iphong, Mar 6, 2007.

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  1. iphong

    iphong Member

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    In theory of physic, movement will absorb shocks & forces, so the more time of movement on the damper, it will minimize the force applied by the Baja landing. the baja is heavy, so when it lands, a huge amount of force transfer to the damper. If the damper is set too firm, the piston will create a huge oposit force back to the shaft, These two oposit forces cause the shaft to bend. Therefore, you need softer damper, so when force transfered to the damper, it moves smooth enough so the springs can do its job to absorb the shock. The problem is you need time to firgure out the right setting for the damper, too soft will reduce shock's absorbent and too firm will result bent shaft.

    Old school physic really helps.

    Phong.
     
  2. bgjames111

    bgjames111 New Member

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    i'm gonna have to disagree here with you a little bit. The spring's job is not to absorb "shock" it's job is actually to preserve ride height, and damping rebound. Too soft of damping will result in a bouncing ride, and bottoming of the suspension too easily. What really is needed here is a stronger shock shaft, maybe a larger diameter...and then use damping that is appropriate to the surface the car is driving on.
     
  3. tulz43

    tulz43 Well-Known Member

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    I'm gonna have to agree with James. Plus RAMtech has released stiff springs....as well as working on some other goodies to help prevent bending shafts. I don't think he'd release something that would cause more bending.
     
  4. Newmer

    Newmer Member

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    After reading all the posts, I think the first 2 are close to saying the same thing, but in different ways. The way I understand Physics, the spring creates resistance to the energy being transfered to the shock, and the dampening slows this transfer of motion energy down.
    I agree with the first post in saying that a high dampening setting does not allow the motion energy to be absorbed quick enough, thus putting the energy at the shaft where the 2 forces of motion resist each other. Energy always has to go somewhere. The heavier springs will give you more ride height, and more resistance, but I do not think the play a part in dampening or slowing the energy transfer down. They help resist the energy transfer, and re-bound it back in the other direction. They create the re bound, not slow it down.
    I think this may be a cause to the bending shafts. The sweet combination or settings for spring rate, dampening, shock size, and amount of energy being transfered to the shock with reference to total weight, when jumping the Baja, has not yet been found.
    I also believe more of the shock shaft needs to be supported inside the shock body. There is a weak point there now.
    Just my theory.

    Newmer
     
    #4 Newmer, Mar 8, 2007
    Last edited: Mar 8, 2007
  5. brice_arnold

    brice_arnold Member

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    It's not as simple as a one dimension force analysis There are forces in three dimesnions acting on the suspension.

    Some issue that contribute to the bending shock shafts include:

    1. the shafts are extended too far from the piston body such that then can get cocked and bend

    2. All of the suspension components are made from very flexible plastic which moves. This include motion perpendicular to the motion of the shock shaft. Thus causing bent shock shaft.

    You are proposing that the shock shaft is buckling due to dirrect axial loading. If you crunched the numbers to calculate the forces for this type of failure you would find that to be an unlikely scenario.In which case changing the dampening or spirngs will have no effect.
     
  6. spuddy

    spuddy Member

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    Coil springs are designed to absorb up/down forces to keep tires firmly planted on the ground. shock absorbers, dissipate the energy absorbed by coil springs, so up/down motion is quickly quieted to zero.
     
  7. brice_arnold

    brice_arnold Member

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    Yep-

    springs resist change in position

    dampers resist change in velocity

    the spirngs will compensate for canges in terain and the dampers will prevent the car from bouncing around like a pogo stick. A classic control systems problem in vibrational analysis.
     
  8. Newmer

    Newmer Member

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    It sounds like we are all close to saying the same thing, just in different ways. Lets hope someone will have a solution soon.
     
  9. Inferno.ca

    Inferno.ca Member

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    One solution for now is to use a short piece of fuel tubing under the piston to set the shock so it does not fully extend. This creates obviosly less droop but also keeps the shock more in line so the initial compression from full extension is not a worry because full extension will now have stability inside of the shock body. The piston will not have a chance to "cock" and bind.
     
  10. Newmer

    Newmer Member

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    I have heared of this before, but I think you lose some ground clearance. Has anyone tried this with success ???

    Newmer
     
  11. Yamadude

    Yamadude Well-Known Member

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    Been there done that it don't help and I have 10 shafts to prove it. lol.The fuel tubing does nothing but take away some travel.
     
  12. spuddy

    spuddy Member

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    the only way your going to stop the shafts from bending is to make bigger shafts Stainless steel or something strong but not so strong its going to snap. i think someone on here are designing new shafts i think all that is needed is to make the shafts maybe 8mm then machine the end smaller the same size as the standard shaft so you can use the piston in the shaft or even drill out the larger shaft and drill a hole in it and tap it to take a small screw to screw the piston on and then make a new bottom end cap out of alloy but make the center bit alittle bit longer so it as more meat there so when the shafts compress it will stop it from bending . anyway only a thought . god i wish i had a machine shop:2guns:
     
  13. RCXpress

    RCXpress Member

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    Well I'm no offroader, so I don't know all there is to know on the subject, but golly wouldn't NOT flinging your Baja 20 feet in the air (as read on another thread) help keep the shock shafts from bending? :p
    Maybe if you can be satisfied with a bit less air time you'll get less down time. :)
     
  14. phx123

    phx123 Active Member

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    Oh come on I said it landed pretty good ;)
     
  15. beachbaja

    beachbaja Member

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    we need piggy back shocks with bigger shafts
     
  16. TurtleRacing

    TurtleRacing Well-Known Member

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    Well, I guess I will chime in here & let all of you know that I am working on the shocks. I have tried bigger diameter tool steel shafts w/aluminum guides, bent them. Now I am making the shafts out of TiTanium & they are holding up quite well. Some more testing & I will be releasing them, so hopefully in the next month or two I will be able get the shock problem reduced to almost nothing. The fact is, no matter what, no matter material, no matter design, someone will find a way to bend them. But the titanium has been holding up very well.

    Piggy backs will be an add on I will offer at a later date, but they will happen.
     
  17. phx123

    phx123 Active Member

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    Thats some good news. I hate breaking shafts . I mean sometimes I jump high but I hate the fact that Im almost scared to drive it cause I know they are gonna break .
     
  18. TurtleRacing

    TurtleRacing Well-Known Member

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    I'm right there with you my friend, I can't tell you how many shafts I've broken! That's why I'm taking on this problem, I know alot of people are having this isssue & must be as frustrated as me. Please have patience though, it will take some time to get it right.
     
  19. iphong

    iphong Member

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    looking foward for the updated shafts.
     
  20. GeneralG

    GeneralG Active Member

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    Here is what happens when you use 15wt oil with fuel tubing underneath the piston measuring at about 1/4" and the pistons set to the biggest opening. mmm, yup they still bend!

    [​IMG]