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4 seat buggy, best approach...

Discussion in 'Center Of Gravity' started by BadDog, May 31, 2004.

  1. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I’m seriously considering selling my current chassis (K30 frame/cage/suspension) and using the money to help pay for steel to start over with a full custom buggy. This would initially use my 350TBI/Th400/203/205/square 1410 shafts/D60/C14FF/4.56/Detroits/42” TSLs and my existing 4 seats. This would also have a front and rear multi-link with coils. I want adjustable link mounts for tuning and adjustable height for the spring mounts. May go with a LS1 or other late aluminum V8 in the future, might also sell the D60/C14FF for a set of 404 Mogs (or 1300s! /forums/images/graemlins/eek.gif) This may also get full hydro and sell my redneck ram setup. For the body, tube will be mostly 1.75 x 0.120 HREW and 1” since those are the dies I have. I may even use DOM in some high impact/stress areas, but that remains to be seen. I *DO NOT* want to have an HREW vs. DOM (or anything else) discussion here. It also needs to be fairly narrow and low since that is one of the problems I have with the existing truggy. No mid-engine, or terribly radical stuff either.

    Those are the basic parameters.

    I would like comments in general, sketches, pics of similar rigs (fairly narrow and low 4 seat specifically), things you like or have seen, whatever. So if it’s related within reason, don’t worry too much about “off topic”. But there are a few things I would specifically like to discuss.

    1) Square base frame. We’ve had part of this discussion before. I’m thinking 2 x 3 x 0.188 rectangular mild tubing for the main frame. This would be from rear link mounts, forward to the engine mount location. And it would be fairly narrow, about like the stock GM frame. Design would be rigid, with cage used as a “space frame” for added rigidity and I want the engine, trans, and case solidly mounted. Obviously, I don’t want to be ripping it apart or having to change/fix it after building, but I also don’t want to add *too* much weight. Though it would be “down low” and so not as bad as up high. Maybe 2 x 4 would be worth the extra weight? Or 0.250 wall? The rest of the body will be all round tube, but I just don’t see any value to be had with round tube for the main frame since it makes mounting stuff tougher. Also, the majority of loads at that level are going to oriented more-or-less perpendicular to the frame, making square stronger lb for lb.

    Anyone see a problem with steel selection or have any comments?

    2) Unique design elements you would love to incorporate if you could start with a clean slate. I’m mostly interested in function for most and above all, but looks are worth considering if it’s not too much harder, more money, or compromising function. I’ve got ideas and pics of cool consoles, cross members, cage/body sections, and so forth that I’ll be combining as possible. I’ve seen nice frenched gussets where he b-pillar meats the upper halo, cool swoopy console/clusters, adjustable suspension tricks, and all that sort of thing. But not anything that requires more than the basic fab tools (i.e. I have no access to mill, lathe, or CNC water jet). Integrated (lockable) storage is also big on my list. Stuff that works well and helps make use of every available inch.

    Basically, lets just talk about clean sheet buggy design, based on the previous parameters, with the thought in mind that I may well try to build it.
     
  2. Triaged

    Triaged 1/2 ton status

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    1) I don't see the need for any square/rectangular tubing. You don't need it from a stress or stiffness standpoint as the rest of the "cage" will provide more stiffness then it ever could. You can't bend it, weighs more, costs more... You also have to look at how you are going to tie in the round stuff to it...there arn't many good ways that are easy (but using the same width as the round would be a good start). I think motor mounts would be just as easy on round vs square...the only one that might be easier is the Steering box and T-case mount but even that shouldn't be that hard ( 2 parallel tubes plated and some poly bushings and tabs?).

    If I was going to use rectangular I would be tempted to just keep just that section of frame from the K30 (T-case to steering box). Why duplicate something that is already there?

    2) If you want lockable "skinning" the tubes with some welded sheet steel would be a good way to go. You can even call it a "shear pannel" and forgo triditional "triangulation". I would also desigh something around a nice marine cooler (marine versions get redisigned much less often and are large and have lots of insulation).
     
  3. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Thanks for the input Dan. My main beef with round down there is the impact resistance and inertial loads from the drive lines when I land hard. I've seen quite a few tube buggies where the bottom tubes get pretty wasted/flattened/dinged due to landing on them. And the only defense from impact damage is to skid plate them all sufficiently, and there comes the weight back into the picture. Square can handle that sort of thing much better than round, leaving skids only where needed to keep from hanging up or hitting something vulnerable.

    I do agree about the mounting thing, that's a pretty small issue in the over-all scheme. I think it would be easier mounting things like the link brackets and such, but round can be plated to achieve a nice mounting surface. I don’t know, maybe I’m just stuck in a mind set and should open up to the possibility of a full tube chassis. I know the comp rigs generally go that way, I’m just not sure it is the best way for a general play rig that is expected to last a few years of torture.

    In any case, I am also considering striping it to the frame and starting over. But that leaves me with the up-n-down K30 frame that makes many other things more difficult. It would be more likely if I had a straight K5 type frame (with straight rails between the axles) and it would weigh less too. Either way I’m not too keen on using the K30 frame if I’m going to go to all this trouble anyway…

    That’s what I had in mind for the lockable storage, I just have to make sure the tubes wind up in the right places. /forums/images/graemlins/laugh.gif I’m thinking that is one of the best things about starting clean slate, I can make much better use of space while keeping the overall dimensions smaller and lighter.

    I’ll check into the marine coolers too. I’m sick of strapping on a cheap cooler.

    Thanks…
     
  4. az-k5

    az-k5 1/2 ton status

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    I am in the square base group. It makes the frame much easier to build, modify and add on too (but you already knew that). It also allows the impact stress to remain at the frame level. Look at marves buggy, his is all out of plumb after one season (and one very severe roll). A round tube frame is more of an underbody cage when it comes to distributing the load. The problems I have seen most often with round is a good impact on the base frame tubes can skew the upper cage, and a hard flop on the top of the cage will skew the frame mounts as well. This will just be copounded by using a wheelbase sutable for a family buggy.

    As for fitting 4 seats in with tools, food, gear, and people I think getting real creative on storage is a must.

    I can't wait for your new project to begin. /forums/images/graemlins/bow.gif
     
  5. Triaged

    Triaged 1/2 ton status

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    I can't see suqare or rectangular tubing being any more dent resistant then the same wall thickness round tube. The other point to consider is the yield strength of the material. DOM will have a higher yield strength then welded stuff so lower rails might be a good place to use some of it...or just thicker then .120".

    The only time you see "frame rails" in racing is when they are required by the rules.
     
  6. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hmmm... I disagree, and given you know more about this engineering than I do, I'm probably looking at it the wrong way. So, I’ll explain my views and maybe you can point out my mistakes…

    My view comes from 2 places. What I've seen and what I (try to) think my way through (which is often what gets me in trouble).

    I know I've seen lots of full tube buggies out here that have lots of flat spots and outright kinks in the lower tubes due to break over of boulders or falls. These are then cut and spliced or plated to repair as needed till things get too far and they start over. I also see square base frames that travel the same territory in rigs with otherwise similar characteristics (Toy based in many cases) and they last several seasons with only abrasion and minor (very insignificant) dents. I attribute this to high ksi loading in round tube. With round tube, almost every impact is going to point load the tube wall. And the round tube is not structurally designed to support that, so it gets dents, egged, and flat spotted. Once it starts to dent/egg/flat, it has lost much of its strength and the only thing saving it is the space-frame triangulation stopping the nodes from pulling together. Square tube takes the hit (depending on impact surface) and typically spreads it over a larger surface. As the base frame gets most of it’s loading up and down, the vertical walls are perfectly oriented to deal with it as efficiently as possible without damage. Even if the horizontal was gets a small dent, once it conforms to the impact surface, the ksi drops dramatically and the side wall can support the load. The only exception might be sharp pointed surfaces which generally break off anyway.

    I see round tube primarily useful for aesthetics and random load orientation (from any direction). And square for predictable directional loads such as the lower chassis frame. Of course I’m also thinking 2 x 3 x 0.188 as opposed to dual trussed round tubes 1.75 x 0.120. Big difference there, but I still think the square could handle the forces better lb for lb...
     
  7. Triaged

    Triaged 1/2 ton status

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    I guess I am thinking about rocks as being more of a point load then flat... That being the case I would a round structure would provide the best distribution of that load and a flat structure would be put in more bending (the weakist way to load something). I may very well be wrong in that assumption (and it sounds like I am from your experience) but that was my reasoning. Heck on the little car I designed and built I made the A-arms out of 3/4 x .035 wall /forums/images/graemlins/yikes.gif Someone finally dented one by hitting it while sliding in one of the trailer ramps /forums/images/graemlins/doah.gif.

    In bending the box section would be WAY stronger then tube...but this depends heavily on how long the un-supported sections are. If you want to know how strong they would be in bending I could send you an email with a spreadsheet that would calculate it for you...
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    That would be great. I would love to see/use that spread sheet if I do start this project...
     
  9. jjlaughner

    jjlaughner 3/4 ton status

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    If I knew a little more about the avaliable parts I'd sketch up a few designs. I have several based on blazer frames /forums/images/graemlins/thinking.gif
    I'm not an engineer but I understand the concepts and I ALWAYS, usually, build overboard /forums/images/graemlins/whistling.gif /forums/images/graemlins/histerical.gif
     
  10. BILLY RAY

    BILLY RAY 1/2 ton status

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    Hey BadDog kind cool to hear about the buggy thing. If you want to wait I will be doing mine this winter. Full tube and yes a four seater. The only thing I don't know is if I should put the Rad. in the frt. or back? Oh well the buggy will be 4 link frt. and rear with a Jeep Lib. hood it will also be running full with axles and the doubler will be replaced for an Atlas. /forums/images/graemlins/hack.gif


    Hey BadDog as for the tube that gets drug on rock what you do is bend and weld another peice under the main fram line and when it gets wasted just cut it off and install another one. That is what alot of the comp. buggys are doing.
     
  11. Hossbaby50

    Hossbaby50 3/4 ton status

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    That is a cool idea with welding in the second set of tubes to take the abuse and then reweld new ones in once the old ones are FUBAR. It kinda seems like it is missing the point though. Why go threw the hole process of cutting off the old tube and welding new tube every season if you can build it out of square tube that will take the abuse forever and not bend.

    I see the local AZ guys dropping there 5-6 thousand pound trucks on there square tube rock sliders all year every year and they never have to cut and reweld new sliders in. /forums/images/graemlins/dunno.gif

    Harley
     
  12. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    That is a good idea, and I've seen that on some of the local rigs. Basically a sacrificial tube to protect the others. I’m just not sure it’s worth it. Still pondering exactly how, or even if, I will build one… But one of my main criteria after working on this one so much and breaking so often is that it be as close to zero upkeep as possible. Obviously that’s a far reach from reality, but like Harley said, if it can be avoided, why not?

    Also, *if* I do it, it will probably be done this summer/fall to be ready for the winter wheeling season. But that 110* heat (already) just saps the energy out of me these days…
     
  13. BILLY RAY

    BILLY RAY 1/2 ton status

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    I do understand the AZ. heat we do have this thing called Texas heat and that is why winter is the time for me. The other reason I don't do much wheeling in the winter and I will be using alot of parts from my K5/Buggy.
     
  14. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    I want to jump in on this but can't read through all of it at work so maybe tonight.

    Russ, you need to talk to my brother some more, these are all the reasons we built him a full chassis rather than starting with a K5 like he originally wanted to do.
     
  15. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Looking forward to your thoughts. And yeah, that's why I called him to start with. He had the perspective of being around for your K5 to truggy evolution, also saw any issues that came along with Beck's, and decided to build his buggy. So I wanted any "Wish I had done..." or "Glad I did..." views and that type of thing. If I do decided to jump in on the deep end, I'll likely be chatting with both of you on several things including links, drive train mounting, and similar.
     
  16. BILLY RAY

    BILLY RAY 1/2 ton status

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    /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif
     
  17. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Well, here we go. Brandon's buggy kicks butt over a frame based rig for a couple of reasons, mainly lighter (depending on the individual of course) and the weight is lower. His motor is about 6" lower and 8" farther back than a stock GM frame in relation to the axle. This is looking at frames with around a 12-13" ride height or roughly a 4" lift. This drivetrain lowering is a cool feature and really helps keep the thing more stable and it would be really tough to do with a stock frame and still have any good reason to keep the stock frame.

    Round vs. square for the belly? I'm still not sure. For the hard vertical hits, the square is the strong material for sure. "I" in the vertical direction is huge for square and that is a big deal.
    Dent resistance? Not sure but you're right, russ, when you hit something, it should only push up till it hits the vertical wall and stop, if it even goes that far. However, here in the real world we put belly skins and thick side panels under everything and dent resistance becomes irrelevant. Looking at Brandon's, I've almost decided to just use round to do my own because I'd still use the 3/16" AR plate for the belly and that stuff just doesn't let the supporting structure get dented. A square or rectangle section is still stronger in the one direction we can load it on the belly though, straight up and down. Maybe this is where we use some thinner wall rectangular tube, maybe even less than 1/8th? Brandon's is 2x3x1/8" and I think it's plenty strong. In fact, I'd say it's overkill for the section going up to the motor because that area is heavily triangulated by the rest of the chassis and doesn't take hits like the belly.

    One of our main goals in his buggy buildup was to have a durable vehicle that didn't require replacing tubes from rock damage. To achieve that we used .120 wall DOM for everything that could get hit and it's pretty heavily triangulated, probably more than most buggies. But I know it's going to shrug off a lot of hard hits over the next few years. My K5 took a NASTY tumble at the supercrawl a couple years ago and judging from the stress cracks and wrinkles in the paint, it tried hard to bend in the middle but held up. I could have been replacing the chassis and some major drivetrain parts but instead we fixed the shock mounts and kept using it. I think we all want as much of that durability as we can get.
    I'm not a frequent spectator at the rock crawl comps anymore but I've seen a couple and seen vehicles tumble hard enough to seriously mess up a chassis that may have made it intact with a few pounds of x-bracing. For recreation guys, this is the key to having fun: not having to work on it any more than absolutely necessary.

    For storage, take a look at the various toolbags that places like Mastercraft build, think about ammo cans, tuffy boxes, etc, when you start. There are some small things you can do with the chassis to make storage easier but I wouldn't compromise much since storage is easy to tuck into misc. places. A spot for a cooler probably has to have a bit more planning. There's no doubt that having all the little places to store stuff and nice mounts for everyting makes the vehicle far more enjoyable. I have a problem now with continuing that work on Wally knowing that I want something different.

    My advice to you Russ is this: figure out how you want to build it and build yourself a new chassis. Since you have all the hard parts already, the price outlay will be minimal. I guess minimal is all relative but you have the EFI motor, trans, low gear t-case and the axles already, that's a major chunk right there not to mention stuff like radiators and seats and gauges, etc. I think your overall satisfaction level will be much higher both short term and long term. I know I've run Wally for a relatively long time with minimal work other than crash repair (and not much of that in the last year) and it's been very nice. I don't see why you couldn't have several years of hard use with the same minimal upkeep.

    Theres my book on this for now.
     
  18. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Thanks Stephen, you input is much appreciated as someone who has been there.

    But actually, I don't think I'll be plating anything but the drive train (between the rails). Seems like the plated boat sides are heavy, and I really like the way my outriggers work. I can see cases where they might present a problem, but so far they haven't and I've discovered that they work very well to hook and pivot before sliding right along and off. Seems like my 2" x 0.250 square outriggers would way less than the side plates, but things are different in a narrow buggy, and the outriggers will be much more inboard so that may change things. /forums/images/graemlins/thinking.gif

    And I like the idea of 1/8 wall square for the main frame, the only thing I would worry about (considering skids) is the suspension mounts would need more effort to tie into the other tubes to keep from damaging the frame or ripping out...

    Believe it or not, I'm leaning ever more toward a full buggy, but I sure will miss the truggy. Amazing how attached you get, as I'm sure you can understand with Wally. I'm also thinking about going down and getting a GM 4x4 model for parts to do a scale model of what I want. Something productive while I'm getting up the energy and drive to tackle a buggy... The scale model of my cage sure helped out a lot when I did it (my first). My first plan looked a little better, but the model was “soft” in several dimensions due to aesthetic bends. I corrected it in the model till it was solid. Then I had already bent and assembled it in the model exactly like I would do in the cage, so the cage when fairly easy even though it was the first. I’m thinking the same will be true with a buggy. I also want to play with links and such too.

    And with the price of steel, I’ll probably be building it all with the HREW I stocked up on a while back. At most, I may buy a couple of sticks of DOM for the really critical impact zones, and of course the links. Or maybe even square links? Ugly, but very bend resistant for the lower links. Then, 4 link (parallel, double or single triangulated?), 3 link, torque tube style (grader ball style), etc. has to be decided for each end and work out the compromises and costs. Suspension, sway bar(?), …. ooooh, my head hurts already.
     
  19. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hey, here is one for you (all of you for that matter). I was thinking earlier about this and I’ve come up with something that I think may be original (at least I don’t think I’ve seen or heard of it).

    Thinking about dynamic adjustable height. Thinking about airbags and other options. Thinking about the limitations of airbags such as general lack of travel and vulnerability, etc. Thinking about roll control and sway bars. And then it dawns on me. One of the best things about links is splitting the job of locating the axle and suspending so you can deal with each optimally. What about 1 step further? Split suspension and roll control! One of the big expense issues is long travel coil-overs. Separate coils and shocks have mounting and space issues as well as travel. Why? Because we mount them outboard to control body roll relative to side forces as well as the rate of that body roll (and limiting oscillation, etc.). If you mount them in-board you effectively increase travel, but loose control. Airbags are worse because of limited travel, so they get mounted forward on arms or such, making them more vulnerable and requiring arms and joints that are stronger still since they are now load bearing again. Blow a bag and you’re screwed.

    So, my idea (for you guys to shoot full of holes). Why not mount an airbag in the center of the axle over the bridge. This airbag does nothing but support the load by lifting 4-6” off the collapsed height. The truck would be bump stopped to prevent anything terrible, and could also incorporate a coil spring to prevent total collapse if a bag/line blows, and to add rate before bottoming with the bag intact. The bag could be raised to full height for height adjustability, and articulation would remain unaffected. But what about body roll? Do what the coil-over guys do to deal with the coil push off and soft rates, add a tuneable sway bar. With variable height, the swaybar will rotate with no load and work the same from different heights. Dealing with changing arc geometry you could even have it effectively stiffen as height increases. Easy adjustability (if done right) would also allow you to account for predominant side hill and off-camber vs tip-toeing through a boulder field or climbing falls.

    Obviously, this is for the rear. The front has more complexity but this might be adapted to the front with some success as well.

    What do you guys think? Am I nuts?

    [Edit]
    The only thing I can think of that would be a loss over outboard coil-overs would be loss of variable rate, but creative implementation of the sway arms and links could give some variable rate...
     
  20. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Not nuts.
    I have some sketches of the same thing but with a single coil or coilover tied to the end of a hydraulic cylinder to adjust the ride height.
    You ever looked at how a scorpion actually works? I think this is the line of thinking that started that direction.
    You still have to have a shock at the wheel so I don't think you' would gain much more than easy adjustability of the ride height from just having to move one spring mounting point. It would be pretty easy to adjust your roll rate with varying lengths of arms or multiple holes in the arms.

    There's something bugging me about this and I can't figure it out right now. With a swaybar for 100% roll control, your suspension is full coupled side to side. The other extreme case is a standard leaf or coil at each wheel where your inputs to the chassis are somewhat independent.

    Maybe there's something to this that won't work because of this 100% coupled action?
     

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