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    Re: How to design and build A-Arm suspension
    #31
    Seņor Banned Member Chikin's Avatar
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    Deaner::: with the front steering vs the rear steering.
    If you have front steer..... Well the mounts come farther out towards the wheels. So depending on the spindles/wheel combo. This can be tricky because you can get the wheel and the steering joint to hit each other OR.... Have a piece of debris get lodged and blow a tire. But that's trivial points and well any thing can happen once off road...right.

    But this photo shows the mounting points of the rack placement for front and rear steer.



    So rick is right when he says the steering link would not get bent from and objects possibly hit while still off road because it's rear mounted on the spindle.
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    Re: How to design and build A-Arm suspension
    #32
    Bend-Tech Dragon Master
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    Quote Originally Posted by minibajaman View Post
    No. While this can happen, there isn't any reason it needs to. Sometimes the numbers work out well, like 10 deg rake and 10 deg caster. But if you want 10 deg of rake and 5 deg of caster like I have on my buggy, this is also achievable. This has been debated many times before, no real need to do it again.
    .
    Oh I know they can be separate, it all depends on how much articulation your steering pivots can take. Tho I did build a king pin type that added or subtracted caster from rake without any down sides.
    Okay, I'll go sit in my corner now
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    Re: How to design and build A-Arm suspension
    #33
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    Does anyone have a picture process to help explain these steps for a hands on learner like myself. I've been reading and reading trying to figure it out but I'm only finding pieces of information and can't quite put it together. I really want to understand it though. Thanks in advance for any help.
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    Re: How to design and build A-Arm suspension
    #34
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    I clicked on some of the suggested threads at the bottom of your post. No process but some suggestions.

    I went through the same process after Shannon Campbell won KOH with an independent front suspension. It was explored pretty well as several started to build IFS cars and reported on Pirate4x4.com.

    You may find this thread informative and there is a list of most all IFS cars in Ultra4. At the bottom of that list are some builds. Starfighter is a good one to help with the process.

    http://www.pirate4x4.com/forum/gener...x4-biulds.html

    That being said. It is NOT EASY in today's Tech. Tech has moved beyond the 2D and 3D basics that was standard 5 years ago but still the most common. Today, the best and most complete way is to design with simulation programming and then design the build. Whatever you start with you will want to put the tire where you want it...and then complicate that with body roll to the ground. Body roll destroys A-Arm camber to the ground. It is something that few designers take into account but a becoming aware of it as others have moved to the more sophisticated geometry. Pictures of poor roll geometry should be that link also. As a hint, 90% the new tech is in the frame mounting of the A-Arms, and I doubt you could mess with that on a drawing board but possibly in a suspension program that you would just have to play with. If you see frame mounts parallel, that can be said as old tech.....But that old tech is still winning so we might be talking the last 2% in suspension geometry control. I spend hourly weeks trying to do it myself on a board and finally gave it to a master as he has learned through about 10 builds and countless videos and pictures which I support. Too bad he is not in the industry but with that talent has moved on.

    Now you can ask just how important is IFS geometry to this level. Guys are winning without it but taking some nasty rides as the front tires tuck underneath in a turn. How far they tuck is how tight, how much weight is put on the outside corner, and how much CG & body lean is in the car. Ultra4 cars are extreme as they usually run 50/50 weight, are around 4000lb+, run tall 39-43" tires at relatively low pressures,and turn30-38* from center. CG's are all over the place, as fabrication tech came from Straight axles which usually need high bodies. A TT probably has a 60/40 ratio and maybe even a CL1 car is 70/30. They want to skip the fronts. I'm not sure about the SXS's but they are lite and the tires don't fold under like a larger rig. As you get further away from the weight and lean scenario, the less IFS geometry has to be at a high level.

    It is usually easy to design a IFS for straight running on uneven ground. If your terrain has turns or offcamber, then make sure you consider the effects of body lean on camber to the ground.

    For ultra4 rigs, our IFS design criteria is simulating with 10* body lean. Take front pictures of similar cars in a turn to measure what is the normal roll for your use. It is interesting that I am using 5* for the rear, as usually the rear jacks up and the body roll to the ground is less. Too much sliding traction in the rear can be an uncomfortable thing, as that can flip you over also. Rear race tires may have a different sidewall tread than the front. Kind of like straight across paddles let you broadslide easier than those in a chevron pattern. And the process goes on..............

    As a little Ultra4 history as I see it. IFS was/is the rage because of the positive handling with racks and swingers. All others are hydraulic with little control (in comparison). About that same time racers learned about rear steer from 4 link geometry. It had moved from panhard rod rears used in rock crawling, but little was known about how a rear steers across uneven terrain. They caught on to that which helped the front straight axle guys. Shock tech improved, and now hydraulic steering is much more responsive. With a straight axle, they always perpendicular to the ground with good traction. You don't loose camber thru body roll...but the CG can spank you and tire tuck is still there. Out'ed lately is setting the front and rear spindles with a few degrees of negative camber. Photos have also shown the benefits. IFS is great for going REAL fast, but SA's can go fast also.

    On Ackerman: The only place you need Ackerman IMO is in the parking garage. It seems like the last thing you want to happen in a front end is that the outside tire does not want to turn..and turn you. This is especially true in a front wheel drive where it is pulling you around. In the dirt, I think parallel is beneficial. I would worry more about bump and roll steer. That is usually handled by the length and positioning of the steering rack or swingers. IFS will test you no matter your proficiency.

    You won't get much information from sports car guy as they are used to big roll bars and 3" movement, but they would be much closer to helping if they had the interest. A local friend owns a suspension shop and when I visit I get to look at some pretty spindly sports cars. Some couldn't survive a 3/4" pot hole. Plus along with travel we have huge braking stress with those big tires. Most all IFS wear (heims) is from braking.

    Minibuggy was a great resource to start learning from. Just paying back some of the extras we are applying today...and just mentioned several years ago.
    Last edited by Isdtbower; 05-28-2017 at 03:36 PM.
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