Thread: mounting shocks

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    Re: mounting shocks
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    Quote Originally Posted by LiveWire\";p=\"72419

    This suspension has 18.25" long shocks with 6" travel yielding 12" travel at the axle stub and 6.25" travel shock on the 2nd and 3rd yielding 12.5" travel. At first glance, it would appear the shock is inline with the arm. While inline with the tube, the actual A-arm pivot line is at less of an angle than the tube because the ball joints are clocked upward. The lower shock mount is in reality about 1.25" lower than the A-arm line making the suspension slightly more progressive. The suspension never reaches a point of the shock being 90 degrees to the A-arm, let alone the A-arm tube. The motion ratio starts slightly above 2:1 and ends up slightly below 2:1 with a 2:1 overall.
    I'm sorry but could you explain that first sentence in the second paragraph ?
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    Re: mounting shocks
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    [quote=masterfabr\";p=\"72421]
    Quote Originally Posted by "LiveWire\";p=\"72419":rhr4udcq

    This suspension has 18.25" long shocks with 6" travel yielding 12" travel at the axle stub and 6.25" travel shock on the 2nd and 3rd yielding 12.5" travel. At first glance, it would appear the shock is inline with the arm. While inline with the tube, the actual A-arm pivot line is at less of an angle than the tube because the ball joints are clocked upward. The lower shock mount is in reality about 1.25" lower than the A-arm line making the suspension slightly more progressive. The suspension never reaches a point of the shock being 90 degrees to the A-arm, let alone the A-arm tube. The motion ratio starts slightly above 2:1 and ends up slightly below 2:1 with a 2:1 overall.
    I'm sorry but could you explain that first sentence in the second paragraph ?[/quote:rhr4udcq]

    I thought, yeah, that is a bit of a messy sentence, I'll just edit the post. DOH. I had started with one picture then added more. I just added to the sentence instead of rewriting it.

    The buggies pictured below have 18.25" long extended shocks. The shocks on the first one have 6" travel yielding about 12" travel at the axle stub. The 2nd and 3rd cars pictured have 6.25" shock travel giving about 12.5" travel at the axle stub.
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    Re: mounting shocks
    Senior Member Engineer's Avatar
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    Jerry

    * Your (Simpleton) observations are very good in my opinion. *They address most of the important concepts without being mired down trying to reach theoretical perfection, which always creates tradeoffs.

    * There are always limiting straps and bump stops that can be added..... * * [smilie=banghead.gif]

    Masterfabr

    * You were correct at the beginning. *The shock only sees and works on its relationship and mount on the A-arm, the frame, and the A-arm pivot on the frame. *The left red line and the green line in the picture. *The shock does not control the wheel, it controls the A-arm. *The A-arm controls the spindle. *Do you want to factor in camber change when looking at wheel travel? *The buggy pictured with the red green and yellow lines probably generates 1 inch or more of vertical wheel travel through camber change alone.

    * So in my opinion you were correct that the important relationship in keeping progressive travel, and maximum shock leverage etc is between the shock mount on the frame, the shock mount on the A-arm, and the A-arm mount on the frame. *The Ball joint location is a separate issue……… *I did not say that the ball joint location does not matter, that it does not have any effect, or anything else about it, just that it is a separate issue. *Eight pages of this thread are a result of short incomplete answers, and misunderstandings. *At the beginning you were holding strong, but then the weight of opinion started to make you question. *So I had to post. *I am not trying to be a dick, but you really have to break everything down to understand how it works, and everything affects everything. *I do alot of work with linkages at work, so buggy suspensions really fascinate me, because in truth they are very complex, and yet simple in basic design.

    * So while I believe you were basically correct in the beginning. *The guys looking at ball joint location are correct in some ways also, because ball joint location also affects wheel travel progressiveness etc. *And as others have pointed out, the distance the shock is above or below the A-arm is usually slight, *so there are not huge differences. *Especially on ATV tire cars. *When trying to get 20-24 inches of travel things start to get real crazy, and angles get out of control.

    LiveWire

    * You are correct. *I misinterpreted some of what you were pointing out with your chart, and did not understand exactly where you were coming from. *Your right that much of the disagreement comes from not understanding exactly what others are saying.


    *
    Quote Originally Posted by LiveWire\";p=\"72330
    I would like to know the goal of that rule of thumb. I thought the goal was to prevent a falling rate suspension and maybe that is. So my argument is that the shock mount needs to be inline or below the arm itself for that to work. Sometimes it is the case though that we argue about what to do not realizing we have different goals. At that point it becomes a case of personal opinion as to which factors are most important to the individual.
    On the other hand maybe I was correct about your misunderstanding because you restate it in this quote. *(So my argument is that the shock mount needs to be inline or below the arm itself for that to work.) *This statement has no basis in truth. *It doesn't matter if the shock is mounted inline, above or below the A-arm. *What matters is the angle between the shock mounts and the A-arm mount on the frame. *Your chart proved that and you don't even know it. *You changed the location of the lower shock mount on the A-arm in your diagram, but you also changed the angle of the shock to the A-arm at the same time because you kept the top shock mount the same horizontally. *If you would have allowed the angle to stay the same, you would have found that a low or high shock mount gives the same progressive ratio. *This would have meant that on the high mount the top of the shock would have moved toward the frame, and with the low mount the top of the shock would have moved very far toward the tire.

    You have to change only 1 variable at a time in order to absolutely prove anything. *So you did not prove that the lower shock A-arm mount location is the key, because at the same time you allowed the angle to change between the mounts.

    If you have not understood this yet, try reading it again very slowly to understand exactly what I am saying.

    I understand your chart 100% and exactly what you accomplished, and yet you have drawn an incorrect assumption from it.

    I am not trying to be a dick, just technically accurate, and I assume everyone on here wants to have a correct understanding as well. *Since I made my first post everyone seems to have changed from technical argument to (hell yah lets ride!!). *So I assume either we have got waaaaay to deep on it and now no one cares, or some people have seen that it is not so simple.

    I am not picking on you, it's just that (the shock mount needs to be inline or below the arm itself for that to work.) is not an accurate statement because it doesn't take into account the upper shock mount location. *I do understand what you’re saying.
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    Re: mounting shocks
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    Engineer,welcome to the site again! EXCELLENT POST. So far as I'm concerned you have not been a dick in this topic at all. And NO not because you agreed with my first assumption but because you explained it in a way the made sense to me. I must admit I wishy-washied on the subject since k-fabs animation made sense to me as drawn but I think you'll also notice in latter posts that I also had reservations about it also.That is because the animation was not the same as the a arm example being discussed. I did not then or now feel that we were considering all influencing factors correctly.Just a gut instinct and with no verifiable basis in fact. *OK NOW IT"S TIME FOR THE REBUTTAL FROM THE OPPOSING POINT OF VIEW. C'mon if you REALLY think your argument is more compelling then help the rest of us to "see the light".
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    Re: mounting shocks
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    [quote=Engineer\";p=\"72433]Jerry

    * Your (Simpleton) observations are very good in my opinion. *They address most of the important concepts without being mired down trying to reach theoretical perfection, which always creates tradeoffs.

    * There are always limiting straps and bump stops that can be added..... * * [smilie=banghead.gif]

    Masterfabr

    * You were correct at the beginning. *The shock only sees and works on its relationship and mount on the A-arm, the frame, and the A-arm pivot on the frame. *The left red line and the green line in the picture. *The shock does not control the wheel, it controls the A-arm. *The A-arm controls the spindle. *Do you want to factor in camber change when looking at wheel travel? *The buggy pictured with the red green and yellow lines probably generates 1 inch or more of vertical wheel travel through camber change alone.

    * So in my opinion you were correct that the important relationship in keeping progressive travel, and maximum shock leverage etc is between the shock mount on the frame, the shock mount on the A-arm, and the A-arm mount on the frame. *The Ball joint location is a separate issue……… *I did not say that the ball joint location does not matter, that it does not have any effect, or anything else about it, just that it is a separate issue. *Eight pages of this thread are a result of short incomplete answers, and misunderstandings. *At the beginning you were holding strong, but then the weight of opinion started to make you question. *So I had to post. *I am not trying to be a dick, but you really have to break everything down to understand how it works, and everything affects everything. *I do alot of work with linkages at work, so buggy suspensions really fascinate me, because in truth they are very complex, and yet simple in basic design.

    * So while I believe you were basically correct in the beginning. *The guys looking at ball joint location are correct in some ways also, because ball joint location also affects wheel travel progressiveness etc. *And as others have pointed out, the distance the shock is above or below the A-arm is usually slight, *so there are not huge differences. *Especially on ATV tire cars. *When trying to get 20-24 inches of travel things start to get real crazy, and angles get out of control.

    LiveWire

    * You are correct. *I misinterpreted some of what you were pointing out with your chart, and did not understand exactly where you were coming from. *Your right that much of the disagreement comes from not understanding exactly what others are saying.


    *
    Quote Originally Posted by "LiveWire\";p=\"72330":247gi9c7
    I would like to know the goal of that rule of thumb. I thought the goal was to prevent a falling rate suspension and maybe that is. So my argument is that the shock mount needs to be inline or below the arm itself for that to work. Sometimes it is the case though that we argue about what to do not realizing we have different goals. At that point it becomes a case of personal opinion as to which factors are most important to the individual.
    On the other hand maybe I was correct about your misunderstanding because you restate it in this quote. *(So my argument is that the shock mount needs to be inline or below the arm itself for that to work.) *This statement has no basis in truth. *It doesn't matter if the shock is mounted inline, above or below the A-arm. *What matters is the angle between the shock mounts and the A-arm mount on the frame. *Your chart proved that and you don't even know it. *You changed the location of the lower shock mount on the A-arm in your diagram, but you also changed the angle of the shock to the A-arm at the same time because you kept the top shock mount the same horizontally. *If you would have allowed the angle to stay the same, you would have found that a low or high shock mount gives the same progressive ratio. *This would have meant that on the high mount the top of the shock would have moved toward the frame, and with the low mount the top of the shock would have moved very far toward the tire.

    You have to change only 1 variable at a time in order to absolutely prove anything. *So you did not prove that the lower shock A-arm mount location is the key, because at the same time you allowed the angle to change between the mounts.

    If you have not understood this yet, try reading it again very slowly to understand exactly what I am saying.

    I understand your chart 100% and exactly what you accomplished, and yet you have drawn an incorrect assumption from it.

    I am not trying to be a dick, just technically accurate, and I assume everyone on here wants to have a correct understanding as well. *Since I made my first post everyone seems to have changed from technical argument to (hell yah lets ride!!). *So I assume either we have got waaaaay to deep on it and now no one cares, or some people have seen that it is not so simple.

    I am not picking on you, it's just that (the shock mount needs to be inline or below the arm itself for that to work.) is not an accurate statement because it doesn't take into account the upper shock mount location. *I do understand what you’re saying.[/quote:247gi9c7]

    You are still arguing the same points I am. When I stated that the lower shock mount should be inline or below the A-arm line, it was was in regards to previous statements that the shock should be at 90 degrees to the A-arm (not shock to A-arm pivot) at full bump. I argued from the beginning that the angle formed from the shock ends and A-arm pivot is what should be looked at. I was saying that if you were to make the shock 90 degrees to the arm, the mount needs to be inline or below the arm. That would make the angle of the shock/A-arm pivot 90 or less and therefore give a progressive suspension. The chart and drawing with the mount above the arm is an example of what not to do. I was drawing what others said would work and I was proving it would not. I guess I should have added comments along those lines, but was thinking the numbers spoke for themselves. I like numbers.

    I hate rules of thumb in general because I so often see them applied when the assumptions required for the rule to work are not present.
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    Re: mounting shocks
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    Livewire: i am a little slow here, what you are saying is if the shock is mounted above the a arm and you set thing up to be at90 degrees at full bump you are really 90 plus degrees. in other words if you have to mount above th ararm set tthe angle at less then 90 but close to 90 to stay progessive.

    Sorry i am a visually learner, and like rules of thumb because i do not have the high tech kwonledge or skills to figure things like this out on computers. That is you i ask question that may seem simple or silly to people who have the knowledge and computers to figure it out.

    I do really apprecate the time that every puts in the anwser my questions... and thank you all for doing so, If it were not for you ALL I would not have started to build a buggy, I am just tring with the help of ALL of you to build a buggy that will work well and most importantlybe safe for me and my family...
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    Re: mounting shocks
    Senior Member Engineer's Avatar
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    [quote=LiveWire\";p=\"72444]
    [quote="Engineer\";p=\"72433":1uajjljs]Jerry

    Your (Simpleton) observations are very good in my opinion. They address most of the important concepts without being mired down trying to reach theoretical perfection, which always creates tradeoffs.

    There are always limiting straps and bump stops that can be added..... [smilie=banghead.gif]

    Masterfabr

    You were correct at the beginning. The shock only sees and works on its relationship and mount on the A-arm, the frame, and the A-arm pivot on the frame. The left red line and the green line in the picture. The shock does not control the wheel, it controls the A-arm. The A-arm controls the spindle. Do you want to factor in camber change when looking at wheel travel? The buggy pictured with the red green and yellow lines probably generates 1 inch or more of vertical wheel travel through camber change alone.

    So in my opinion you were correct that the important relationship in keeping progressive travel, and maximum shock leverage etc is between the shock mount on the frame, the shock mount on the A-arm, and the A-arm mount on the frame. The Ball joint location is a separate issue……… I did not say that the ball joint location does not matter, that it does not have any effect, or anything else about it, just that it is a separate issue. Eight pages of this thread are a result of short incomplete answers, and misunderstandings. At the beginning you were holding strong, but then the weight of opinion started to make you question. So I had to post. I am not trying to be a dick, but you really have to break everything down to understand how it works, and everything affects everything. I do alot of work with linkages at work, so buggy suspensions really fascinate me, because in truth they are very complex, and yet simple in basic design.

    So while I believe you were basically correct in the beginning. The guys looking at ball joint location are correct in some ways also, because ball joint location also affects wheel travel progressiveness etc. And as others have pointed out, the distance the shock is above or below the A-arm is usually slight, so there are not huge differences. Especially on ATV tire cars. When trying to get 20-24 inches of travel things start to get real crazy, and angles get out of control.

    LiveWire

    You are correct. I misinterpreted some of what you were pointing out with your chart, and did not understand exactly where you were coming from. Your right that much of the disagreement comes from not understanding exactly what others are saying.


    Quote Originally Posted by "LiveWire\";p=\"72330":1uajjljs
    I would like to know the goal of that rule of thumb. I thought the goal was to prevent a falling rate suspension and maybe that is. So my argument is that the shock mount needs to be inline or below the arm itself for that to work. Sometimes it is the case though that we argue about what to do not realizing we have different goals. At that point it becomes a case of personal opinion as to which factors are most important to the individual.
    On the other hand maybe I was correct about your misunderstanding because you restate it in this quote. (So my argument is that the shock mount needs to be inline or below the arm itself for that to work.) This statement has no basis in truth. It doesn't matter if the shock is mounted inline, above or below the A-arm. What matters is the angle between the shock mounts and the A-arm mount on the frame. Your chart proved that and you don't even know it. You changed the location of the lower shock mount on the A-arm in your diagram, but you also changed the angle of the shock to the A-arm at the same time because you kept the top shock mount the same horizontally. If you would have allowed the angle to stay the same, you would have found that a low or high shock mount gives the same progressive ratio. This would have meant that on the high mount the top of the shock would have moved toward the frame, and with the low mount the top of the shock would have moved very far toward the tire.

    You have to change only 1 variable at a time in order to absolutely prove anything. So you did not prove that the lower shock A-arm mount location is the key, because at the same time you allowed the angle to change between the mounts.

    If you have not understood this yet, try reading it again very slowly to understand exactly what I am saying.

    I understand your chart 100% and exactly what you accomplished, and yet you have drawn an incorrect assumption from it.

    I am not trying to be a dick, just technically accurate, and I assume everyone on here wants to have a correct understanding as well. Since I made my first post everyone seems to have changed from technical argument to (hell yah lets ride!!). So I assume either we have got waaaaay to deep on it and now no one cares, or some people have seen that it is not so simple.

    I am not picking on you, it's just that (the shock mount needs to be inline or below the arm itself for that to work.) is not an accurate statement because it doesn't take into account the upper shock mount location. I do understand what you’re saying.[/quote:1uajjljs]

    You are still arguing the same points I am. When I stated that the lower shock mount should be inline or below the A-arm line, it was was in regards to previous statements that the shock should be at 90 degrees to the A-arm (not shock to A-arm pivot) at full bump. I argued from the beginning that the angle formed from the shock ends and A-arm pivot is what should be looked at. I was saying that if you were to make the shock 90 degrees to the arm, the mount needs to be inline or below the arm. That would make the angle of the shock/A-arm pivot 90 or less and therefore give a progressive suspension. The chart and drawing with the mount above the arm is an example of what not to do. I was drawing what others said would work and I was proving it would not. I guess I should have added comments along those lines, but was thinking the numbers spoke for themselves. I like numbers.

    I hate rules of thumb in general because I so often see them applied when the assumptions required for the rule to work are not present.
    [/quote:1uajjljs]


    Peace LiveWire. *Thanks for the Explanation.

    Jerry

    It looks like your doing good figureing it all out. *Puters make some things easier to see, but your patience has a car almost built, and all I have is some drawings on a Computer. *

    Masterfab

    Thanks for the welcome! *I see that you can upload PDF's which I can create from Cad..... *Mabey this weekend. *But I am not sure the opposition cares anymore.
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    Re: mounting shocks
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    Quote Originally Posted by jerry\";p=\"72465
    Livewire: i am a little slow here, what you are saying is if the shock is mounted above the a arm and you set thing up to be at90 degrees at full bump you are really 90 plus degrees. in other words if you have to mount above th ararm set tthe angle at less then 90 but close to 90 to stay progessive.

    Sorry i am a visually learner, and like rules of thumb because i do not have the high tech kwonledge or skills to figure things like this out on computers. That is you i ask question that may seem simple or silly to people who have the knowledge and computers to figure it out.

    I do really apprecate the time that every puts in the anwser my questions... and thank you all for doing so, If it were not for you ALL I would not have started to build a buggy, I am just tring with the help of ALL of you to build a buggy that will work well and most importantlybe safe for me and my family...
    Engineer pointed out you are understanding it well. Looking back in the thread to get back to the original question, it appears you have the bottom of the shock pushed to the outside of the arm and the mount is above. Forget the mounting below the arm part since it would probably interfere with the axle.



    If you were to leave your mount where it is and put the shock 90 degrees to the arm, your actual angle to it's pivot line would be greater than 90. That is what Bdkw1, myself, masterfabr, BugPac and Engineer have been saying. Also, since it is so far out the arm, your motion ratio would be low.

    If you put the shock at 90 degrees to the line from the A-arm pivot to the lower mount, I think your motion ratio will still be low. There is another issue that we did not get into. When I did the CAD diagrams, I created a third like what Engineer was suggesting with the shock at 90 degrees to the A-arm pivot/shock mount line. When I ran the numbers for that, I still got a regressive suspension, just not as bad. I had to lean it in another 15 degrees to get it progressive. I did not post that diagram or numbers because it just added more complexity to the discussion and I was only trying to prove the 90 to the arm part doesn't work. I'm sure Engineer could explain why that was occurring better than I if anyone cares. I don't seem to do a good job putting geometry in my head into words. As I said, I like numbers.

    I would bet that if you do what I said in an earlier thread about finding the upper mount based on the motion ratio, you'll end up with a slightly progressive suspension with no needs for limiting straps or extra snubbers.

    In fact, it may be very close to this:
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    Re: mounting shocks
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    Engineer,it's not that the opposition doesn't care anymore .It's because they are wrong and can't prove their point. *[smilie=blowkiss.gif] * Personally I love these types of debates.Great info and plenty to think about. To each that have contributed to this topic I say GREAT JOB!!!!! no matter which side you are on.THANK YOU!
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    Re: mounting shocks
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    Quote Originally Posted by K-fab\";p=\"72239
    The lever is the a-arm.
    The effort comes from the tire
    The mounting point of the a-arm on the chassis is the fulcrum
    The shock is what balances the load input and controls everything.



    What we're concerned with (and debating) is the two ends of the lever, one stationary (fulcrum) and one movable (effort)
    And
    The two ends of the shock.
    And
    The relationship of these four points to each other at a specific point of motion - the full bump, in this case.

    So let's start out with our a-arm:
    It does not matter how you connect the two points, just as long as they are attached to each other in some fashion.
    (see first pic below. *All are structures that will allow one point to rotate about the other if one point is secured.)

    You can have a crescent shaped structure between the fulcrum and effort.
    Or you can have a straight line.
    Or a curvy line.
    Or a swoopy S shaped unit.
    Or multiple z-bends.

    As long as there are two end points (fulcrum & effort) there is ONE line that concerns this - the straight line BETWEEN THE TWO POINTS (show in blue in the first pic below); each end of a structure, if you will. *This line may be obvious (straight piece of tubing) or 'imaginary' as far as the eye can see. *In physics, it is there.

    They taught us to get rid of all the crap around/between/above/below these to points and to treat it as a straight (blue) line when dealing with loads on a lever.

    This is the line that represents the radius of the curve that the a-arm follows as it moves. *This is the line that the system works around.

    Now throw in the shock. *The shock represents the vector of movement.


    The vector is the motion of the shock as it gets compressed. *It is being pushed by the lever at the load point.

    If you go back to the drawing where I put the green (shock vector) line between the two mounting points of the shock and the yellow line (blue in the pix below), you'll see that these two lines are perpendicular. *It does not matter where the shock is mounted as long as these two lines are perpendicular to each other at full bump.

    While you want to take the red lines as the input to the shock by the system, it is incorrect to do so. *It is all about the forces in the system and the relationship between these two forces.

    Master - I've been searching all over the internet to find an example, but all I can find is a few elementary pics that you see, along with my Yoshicad work.
    I'm not trying to argue with anyone - I'm trying to show you the science - physics - behind the idea. *Physics was my favorite group of engineering classes - I did extremely well in these classes, other than the dreaded Lens stuff - that was screwy.
    Just trying to learn something not pissing. Would not the imaginary lever ac be the real lever we should be considering in some way? And would not be the appropriate shock placement be approx.the red shock or something like it (black shock)? If not -why?
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