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Old December 27th, 2004, 10:21 AM   #1
dez
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well then, as i said last week, heres my little contribution to volksrods.com- some tech articles on flipped beams, including castor angle and ackermann theory.

firstly, you will need to understand these principles to understand what makes a car handle well, or badly.
1.CASTOR ANGLE
castor angle is basically the invisible line around which your wheel pivots when it turns. it isnt a vertical line, it typically leans back about 5-7degrees on a typical road car. front engined cars usually have less castor, as the weight of the engine helps the car turn, and the steering to centralise itself after completing a turn. cars with light front ends, or those used in high speed applications (e.g. lakes roadsters) have much more castor, upto 15degrees, for the same reasons.
a totally stock beetle is listed as having 6degrees of castor. when you lower it, this angle reduces to about 2-3degrees, making the handling very light, and 'wandery',hence why castor shims are available to push the bottom of the beam forward to correct this. this angle changes because of the the traling arm design of the suspension, when the arms go past horisontal (as stock they are below horisontal), it is rotating the cator angle forwards.

so, when you flip the arms to face forwards, instead of having the castor leaning backwards 6degrees, it now leans forwards 6degrees, so the handling will be terrible!! lowering the beam will cure this somewhat, but it will still lean the wrong way by a couple of degrees. even with 3 sets of castor shims it wouldnt cure it enough for it to handle well, hence the need to PIE-CUT THE FRAMEHEAD. you are needing to push the top of the framehaed back by about 10degrees (on a lowered flipped beam) to regain the stock castor angle.

so know youve cured the castor, whats next??
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Old December 27th, 2004, 10:24 AM   #2
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Quote:
Originally posted by dez@Dec 27 2004, 02:21 PM
so know youve cured the castor, whats next??
<div align="right">Quoted post</div>
tell us [img]style_emoticons/<#EMO_DIR#>/Idunno.gif[/img]
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Old December 27th, 2004, 10:25 AM   #3
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mutilate the steering arms at a guess.....
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Old December 27th, 2004, 10:34 AM   #4
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2.ACKERMANN ANGLE
this is the important bit, as its what has the most effect on the handling of the car.



this diagram shows the perfect ackermann setup. when a line is drawn between each 'kingpin' and the steering arm pivot on the spindle, in an ideal setup the lines will cross on the centreline of the car, at the rear axle centreline. quite unsuprisingly, a stock beetle has the perfect ackermann setup!!

so, when you flip the trailing arms forwards, but fit the spindles the conventional way round, you will make the intersect of the ackermann lines move forward about 11-12". this really isnt a problem, and wont effect handling much at all.if youre picky, you could bend the arms a bit so it corrects the geometry. you will need to bend the trackrods a bit to clear the trailing arms, but overall its pretty simple to do, and keeps the steering box in the stock place, and keeps the steering damper on too. and if you shorten the chassis buggy style, it will actually have stock ackermann properties!!

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Old December 27th, 2004, 10:39 AM   #5
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so that bits all pretty simple. it only gets complicated if you want to do a daft system involving suicide steering, or cowl steering like im currently working on for mine.

ile add the diagrams for that as soon as ive finished them [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img]
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Old December 27th, 2004, 10:52 AM   #6
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this diagram shows the problem i have, as i want to run the steering out in front. when you do that, the acckermann lines actually point outwards!



so what do ya do??? ya draw a line between the rear axle/car centreline intestect, that goes out to the kingpin, then keep it going forward towards where the spindle is. this will show you roughly where it needs to be. in this case it need to be rather near the brake drum, close into the backside of the wheel.

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Old December 27th, 2004, 11:07 AM   #7
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Good job Dez. [img]style_emoticons/<#EMO_DIR#>/thumbsup.gif[/img] This needs to be pinned so people can find it easy. Again you've done a good job explaining the problems and some of the solutions. Keep it up. [img]style_emoticons/<#EMO_DIR#>/bowdown.gif[/img]
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Old December 27th, 2004, 11:23 AM   #8
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that is assuming the steering arms are pointing forward. Is there room to keep the spindles in stock position swapping only the trailing arms and somehow run the tie rods between the trailing arms? (hard for me to tell without a car in front of me). wouldnt this keep the arms in more of a line similar to stock?
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Old December 27th, 2004, 11:29 AM   #9
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reread it [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img]

the second diagram in post #4 is what you are reffering to. i think you may have to fit a bumpsteer kit to make sure nothing touches anything it shouldnt, ile be able to tell you in a couple o weeks [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img] as i am going to do a step by step illustrated guide to add to this thread.

i think a lot of people have tried to make this seem harder than it is. it really is only a weekend job to do the whole thing, and have it handle well first time.
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Old December 27th, 2004, 11:37 AM   #10
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DOH!!!!!! must be your accent. [img]style_emoticons/<#EMO_DIR#>/wacko.gif[/img]

but you still show the shock towers pointing forward....so you are flipping the entire axle. what it you just swapped the trailing arms, but left the beam alone.....could that work?
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Old December 27th, 2004, 11:53 AM   #11
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yep, makes no difference. i flipped the towers as well as it allows you to still fit shocks in the 'stock' position, as theyre a legal requirement over here. you could, by all means, just hack the towers off if you want to change the shock style, or not run them at all.
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Old December 27th, 2004, 12:05 PM   #12
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that starts to sound really simple......plus the shocks in front of the beam sticking way up has always bothered me.....gotta come up with a different more asthetic idea
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Old December 27th, 2004, 12:10 PM   #13
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thats what im trying to prove- it is pretty simple.

i have something planned for the beam on my other car- no shock towers at all. instead, it will have morris minor lever arm shocks hidden between/behind the 2 beam tubes- it leaves a lot more room for headlight mounting too.
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Old December 27th, 2004, 02:13 PM   #14
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As someone that knows precisely dick about suspension geometry, ackerman angles, caster, etc. I would like to thank you for putting this up.

With your diagrams and text, it is all starting to make sense to me now.
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Old December 27th, 2004, 08:25 PM   #15
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Quote:
Originally posted by walt@Dec 27 2004, 12:07 PM
Good job Dez. [img]style_emoticons/<#EMO_DIR#>/thumbsup.gif[/img] This needs to be pinned so people can find it easy. Again you've done a good job explaining the problems and some of the solutions. Keep it up. [img]style_emoticons/<#EMO_DIR#>/bowdown.gif[/img]
<div align="right">Quoted post</div>
It is now in the "too lazy for the search function" thread!

Keep it up Dez
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Old December 28th, 2004, 03:11 AM   #16
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Quote:
Originally posted by dez@Dec 27 2004, 01:10 PM
thats what im trying to prove- it is pretty simple.

i have something planned for the beam on my other car- no shock towers at all. instead, it will have morris minor lever arm shocks hidden between/behind the 2 beam tubes- it leaves a lot more room for headlight mounting too.
<div align="right">Quoted post</div>

have you seen these? http://www.tperformance.com/street_rod_sto...tion_shock_kit/

were discussed on here a while ago, could be useful... and cheap.


sounds like this could be the hot setup, since i plan on shortening my pan. Thanks for explaining this stuff.


TFTom
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<span style=\'color:orange\'></div><table border=\'0\' align=\'center\' width=\'95%\' cellpadding=\'3\' cellspacing=\'1\'><tr><td>QUOTE </td></tr><tr><td id=\'QUOTE\'>I'll kill you you sick english FREAK!</td></tr></table><div class=\'signature\'> alltypesvw</span>
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Old December 28th, 2004, 07:27 AM   #17
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[img]style_emoticons/<#EMO_DIR#>/blink.gif[/img] Very informative! Unfortunately I work about 70 hours a week, and i'm not mechanically inclined. It really sucks, I have some cool ideas but can't afford to jack up my daily driver. Before I moved to AZ from CO I couldn't find anyone who knew what I was talking about. Then they were afraid to try it. Is there anyone here in AZ who could help a brotha out with his RAT?
Quote:
Originally posted by Top_Fuel_Thomas+Dec 28 2004, 04:11 AM--><div class='quotetop'>QUOTE(Top_Fuel_Thomas @ Dec 28 2004, 04:11 AM)</div><div class='quotemain'><!--QuoteBegin-dez@Dec 27 2004, 01:10 PM
thats what im trying to prove- it is pretty simple.

i have something planned for the beam on my other car- no shock towers at all. instead, it will have morris minor lever arm shocks hidden between/behind the 2 beam tubes- it leaves a lot more room for headlight mounting too.
<div align="right">Quoted post</div>

have you seen these? http://www.tperformance.com/street_rod_sto...tion_shock_kit/

were discussed on here a while ago, could be useful... and cheap.


sounds like this could be the hot setup, since i plan on shortening my pan. Thanks for explaining this stuff.


TFTom
<div align="right">Quoted post</div>
[/b][/quote]
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Old December 28th, 2004, 07:43 AM   #18
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yeah tom, ive seen those, but as with most street rod parts, theyre overly expensive for whay you get. why not make the arms and tabs out of sheet steel youself, all youll need is a drill, a hacksaw, a file and some time, or you could go all hi-tech and use a grinder! then a hi-ten bolt for the friction pivot,, 4 rose joints, and only buy the friction pads. $3 and a bit of time as opposed to 50 dollars, and the tabs you get in the kit wont be right for the vw front end, so youll need to make those anyway [img]style_emoticons/<#EMO_DIR#>/Idunno.gif[/img] they even give you the dimensions of the damn things!
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Old December 28th, 2004, 08:19 AM   #19
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Looks good Dez [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img]

Lets hope it all works well [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]

I reckon a few step by step photos may be in order, some point in Feb [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/wink.gif[/img]
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Old December 28th, 2004, 08:58 AM   #20
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hi dez
a mate of mine is making some friction shocks out of some con rods looks well trick will try and get some pic`s when he`s not lookin [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]
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Old December 28th, 2004, 05:48 PM   #21
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Lets not get too side tracked on the friction shocks. I really don't understand tem but thats another discussion.

Anyway, Dez, I really hope you include the cutting and tilting of the bulkhead. This actually scares the hell out of me. I have already flipped my ft. end and worked out the angles and such on paper. Not with graphics such as you have done and not with the steering ahead of the beam either. However I did discover the Castor thing as well and was wondering if I should try and make some sorts super wedge welded to the beam and cut the brackets loose and correct the angle on them so they will bolt up straight. I just did not want to even consider the bulkhead tilting thing.

So, yes I think people have tried to make a bigger job out of this then need be. It went quite quickly and I even chopped the shock towers off. I am still working on the dampner interference with the tierod. I am interested in how you plan to address this with out bending the arm. But I guess you'll be going with the steering ahead though so it really wont matter.
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Old December 28th, 2004, 07:47 PM   #22
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This nice little article explains, with simple diagrams, most everything about the Ackerman and how to solve the front steer issue.

Ackerman steering
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Old December 29th, 2004, 03:22 AM   #23
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michael - thanx for that post. even a dummy like me can understand that [img]style_emoticons/<#EMO_DIR#>/thumbsup.gif[/img]
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Old December 29th, 2004, 12:13 PM   #24
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michael has also done some digrams on how the castor bit works, he emailed them to me to o.k. adding them here- i say see as its your handiwork, you addthem and take the credit, as theyre exactly right!!
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Old December 29th, 2004, 12:58 PM   #25
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Quote:
Originally posted by dez@Dec 29 2004, 05:13 PM
michael has also done some digrams on how the castor bit works, he emailed them to me to o.k. adding them here- i say see as its your handiwork, you addthem and take the credit, as theyre exactly right!!
<div align="right">Quoted post</div>

http://www.nationaltbucketalliance.c...info/index.asp

Seems to be a good bit of steering related info...
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