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Custom Radius Arms. . .rod ends or solid mount???

Discussion in 'Shop - Suspension & Steering' started by atomicjoe23, Dec 2, 2009.

  1. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    I'm designing my own I-beam/radius arm front suspension and have a quick question. . .

    . . .when attaching the radius arms to the I-beams what is the "best" type of attachement?

    I've seen solid, the stock C-style bushings and rod ends. . .

    Thanks!
     
  2. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    OK. . .I just poured over Camburg's, Giant's, and Blitzkrieg's websites and they all mount the radius arms to the I-beams using some combination of tabs/ears mounted on either the I-beam or the radius arms with a bolt running through the other piece.

    . . .base on that here's my plan:

    My I-beams are gonna be tubular with the sides plated, so I'll plate them all the way out to the ends and then I'll mount tabs to the plate on the I-beam and plate those tabs so that they are VERY securely supported. . .and then I will bolt the radius arms to the tabs on the I-beams. . .should look fairly similar to Camburg's equal lenght racing set-up.

    Post up with opinions and tips!
     
  3. BRINGTHERUCKUS

    BRINGTHERUCKUS Nimrod de PMC

    Joined:
    Apr 28, 2005
    Location:
    Parker/Tucson, Arizona
    you can weld the radius are to the beam.... known as a "j" arm to the bro crowd, its become quite popular.
     
  4. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    Any advantages to that over bolting it on. . .a little bit stronger connection? at the cost of being able to easily replace a single component?

    Thanks for the suggestion.
     
  5. BRINGTHERUCKUS

    BRINGTHERUCKUS Nimrod de PMC

    Joined:
    Apr 28, 2005
    Location:
    Parker/Tucson, Arizona
    Stronger i think... less chance of failure, the bolt could come loose and cause a whole lot of hell. Happened to me and my cousin at a Snore race last year, it was just hanging out 3 or so inches....
     
  6. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    I'm making beams for a small (<400 lbs without driver and fuel) SAE buggy, max speed will be 40 MPH. . .here they are so far. . .

    They will be made out of 1.00" x 0.120" 1020 DOM tubing, they have 1.0" x 0.090" tube bracing on the inside at the very end that you can see and they also another brace on the other side of the bend. The plating I have in the drawing is 0.090" but I could go down to 0.065" I don't know yet. . .probably depends on how I end up attaching the radius arms to the beams. As you can see right now I have tabs on the outside tubing brace (might change that brace to 0.120" wall since the tabs are on them) and I was gonna box them to the beams with some more 0.090" or 0.065" plate. . .I haven't gotten that far yet though. . .

    Right now these are set-up for ~16" of total travel before frame contact. . .I can't remember the camber numbers off the top of my head, they are in the AutoCAD program at home, but I'm switching over to SW at the moment so I don't have those numbers with me. . .setting them up for about 6* of caster.

    I'm posting a pic of the buggy so far as well. . .I just put some of the sheetmetal on today. I still need to put some lightening holes in the sheetmetal that you see at the A pillar location. . .that's all the sheetmetal I have on at the moment because I have to figure out how to make the correct planes to draw on to get the sheetmetal right in the rest of the places. . .since I can only use 3 points to make a plane they aren't coming out exactly right. . .I'll figure it out eventually but sheetmetal is low on the priority list. . .right now I'm getting started on putting the knuckles into SW's to make sure that I've got the I-beams constructed correctly.
     

    Attached Files:

  7. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    Man, I've really got to remember to turn off the temporary axis view when I save SW stuff as .jpg's. . .sorry about all the dashed blue lines!
     
  8. 1450-ranger

    1450-ranger Well-Known Member

    Joined:
    Jun 13, 2004
    Location:
    CA
    I know you are set on the beams... but bad idea. The steering is complicated to integrate, excessive camber will slow the SAE buggy down dramatically.

    where are you going to mount the radius arms to the frame?? the angle is going to be extreme and the arms will be short.... big caster change. no bueno

    take a step back, zoom out on the project and then decide.



    bolt the beam & radius arm together. much easier to set up, replace & install. keep in mind that once you make a 'j' beam, adjusting the heims pretty much goes out the window.....
     
  9. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    McClintock. . .the radius arms are going to mount to the roll bar (in SAE terminology the rear roll hoop) and will be 36" long. . .I think that's as long (or longer than some of the radius arms out there on full-size (stock) trucks. . .that's over 1/2 the wheelbase of the vehicle. . .that's definitely longer in ratio than anything I know of. . .

    . . .believe me. . .I'm a HUGE fan of A-arms, BUT I spent a LOT of time thinking this over and I think the beams will be more advantageous than the A-arms. . .I spent a lot of time maximizing the length of the A-arms and the radius arms and getting the weight distribution where I want it. The I-beams are not quite 36" long with a front track width of 62.5". . .once again the I-beam are over 1/2 the track width. . .having the I-beams and radius arms as long as they are with respect to the wheelbase and track width should help with the camber change quite a bit. Plus think about the typical SAE buggy (which mine is not), how much wheel travel do they have, like 10" tops for most of them. . .not very much camber change in 10" compared to the 16"+ that you see in real trucks. . .

    I totally respect you and the experience you have. . .and trust me I am taking everything you say to heart. A lot of it I have already taken into consideration.

    I'm working on the radius arms now. . .let me get them on the chassis and I will post up a pic of the chassis with the I-beams and the radius arms on it and then you tell me what you think. . .I've already calculated the camber change in AutoCAD but I don't wanna open that now to see what it was (can't remember off the top of my head) but I will post it up tomorrow while I'm at school (there computers don't get bogged down having AutoCAD and SW's both open at the same time like mine does).

    Keep the suggestions and comments coming MC. . .I'm listening and I appreciate it. . .just wait and reserve your judgement until you see my design. . .once you see it as a whole then make all the comments you want. . .I will definitely appreciate them. I had to learn a lot last year to design A-arms and now I'm learning even more this year to make beams, radius arms and swing-set steering, but I enjoy it and that's what matters most to me at this point in time. . .learn as much as I can while it's not coming out of my pocket!!!
     
  10. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    Oh yeah. . .almost forgot, I'm going with bolt on radius arms. . .
     
  11. Zambo

    Zambo Well-Known Member

    Joined:
    Apr 16, 2007
    Location:
    San Diego, CA
    The problem with "J arm" beams from what I understand is that unlike A arms, the two heims on an I beam setup are at 90deg to each other. Since the mounts are fixed to the frame and cannot move, you have limited adjustability unless the radius arm/I beam connection point is flexible. The distance between the heims never changes due to the fixed mounts, therefore you can't just shorten up the heim at the end of a J beam and reattach it, you'd have to lengthen the heim on the other end of the "arm" so that the distance between the two heims remains the same. On a two piece setup, you can loosen the connection between the two pieces, adjust either heim, and then tighten the two pieces back together. I know at least one fab place that used to make J beams but switched back to a two piece setup for this reason.

    Disclaimer: I am not by any means an expert on this!
     
  12. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    I totally agree with that thought process. . .which is why I decided to go with a two piec, bolt-together set-up.

    Given enough time, money and testing it might be unnecessary. . .you could probably find the "ideal" set-up for "your" vehicle and "your" driving style, but that is not a very adaptable set-up. . .on the other end of the spectrum you can get into too much adjustability. . .

    . . .from my experience with sportbike racing, many racer's have asked the factories for less adjustability because they just end up on a wild goose chase. . .they come back into the pit and tell the crew what they need and then the engineer's just go crazy and their are too many variable to make any useful progress. . .

    I don't anticipate the need for radical adjustments on the radius arms. . .I'm designing them with the heim in the mid position of the threaded tube adapter which should be more than enough. I know the wheelbase I'm shooting for and the adjustments I would need to make should be just fine adjustments. . .I don't think I will need the full 2 5/8" adjustment of the rod end. . .
    "
     
  13. RSwenson

    RSwenson Member

    Joined:
    Jan 9, 2006
    Location:
    San Jose Ca.
    Joe,
    The adjustments Zambo speaks of are not for handling or ride adjustments.
    They are assembly/fitment adjustments.

    Length adjustments are fine for a push/pull linkage but not in this application.

    You should attempt to have maximum thread engagement in both beam and radius arm spherical joint shaft.

    Horizontal and vertical load forces are highest near the pivots.
    The spherical joint shaft is the weak point.

    Ron
     
  14. atomicjoe23

    atomicjoe23 Well-Known Member

    Joined:
    Feb 2, 2008
    Location:
    Silverdale, WA
    Here's a pic with the I-beams and the radius arms on the buggy. . .

    . . .I got the knuckles into SW and now I have to adjust the I-beams. . .I figured that was gonna happen, I was hoping that I would have them fairly close though. . .oh well.

    [​IMG]
     

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