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Old December 29th, 2004, 06:24 PM   #26
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Here are some drawings I made to help out with castor and how it changes on the flipped arms.
1) Stock
2) Flipped arms only, spindles in the stock orientation.
3) The cut needed to bring castor back in the ballpark. (not to scale, just an idea of where)
4) After the cut is made and the frame head tilted up.

Castor will affect the driving down the road more than Ackerman. Ackerman only comes into play when you turn.

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Old December 30th, 2004, 03:45 AM   #27
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Man, all these lame pics that look like something out of a coloring book............ are exactly what I need! [img]style_emoticons/<#EMO_DIR#>/thumbsup.gif[/img] [img]style_emoticons/<#EMO_DIR#>/funny.gif[/img] I tell you, I know nothing of front end geometry and all this is really helpful. I had no idea what the pie cut was all about till it dawned on me the other day, then the pic above confirmed my idea. This would make a good sticky in the "too lazy" section if it's not all ready.
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Old December 30th, 2004, 04:19 AM   #28
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Any guess (calculations?) as to how large a pie cut you make in the framehead for a given amount of drop? The cut Nick made in his didn't look that large and dropped his front end 2.5 inches (IIRC).
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Old December 30th, 2004, 05:08 AM   #29
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I can't remember how much I cut out, was about 1.5" give or take. Easy way to find out is to take a measuring stick or a long pole where the end of the pole is around where the front end will be and the other end where the pie cut will happen. Move the angle up to the desired level then you should be able to find out by the degree of angle you just moved it how much to pie cut out.

FYI, if you just pie cut, you'll end up with a minor lowered job because the trailing arm (where it was horizontal) is now pointing downwards kind of rasing the car back up slightly. So if you change the angle of the trailing arms back to horizontall then you'll get the full effects (but will give you a smoother rise). Or you can pie cut the framehead twice (once on top and once in bottom) for a full Z'd frame effect. Now pie cutting a flip beam will give you even more of a lift then it would a normal beam.

Be precise when welding the pie cut framhead back together or your front end may be alittle lopsided once you put it together. Also when pie cutting the framehead, you need to cut a slit on the bottom of the framehead as well or it won't bend one bit (FYI).

http://www.runtrod.com/files/floor6.htm
Here's my page of the piecut frame for reference.

Before:


After:


Rough cut amount
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Old December 30th, 2004, 06:51 AM   #30
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Not to muddy the waters any more, but could the caster be corrected by swapping the trailing arms top-for-bottom? It might make for some unteresting, underslung shock-mounting arrangements, but... [img]style_emoticons/<#EMO_DIR#>/Idunno.gif[/img]
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Old December 30th, 2004, 07:10 AM   #31
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there was someone that did that.. if you were running without shocks it would be fairly simple.. are there any problems with that setup other than no shocks??? [img]style_emoticons/<#EMO_DIR#>/Idunno.gif[/img]
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Old December 30th, 2004, 07:54 AM   #32
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I think you could swap link pin arms( I think they are very close to the same length however) but I can't see how it would be possible with ball-joint arms. Lowering a car with stock location trailing arms reduces castor. I'm not sure but it would seem lowering a car with reversed trailing arms would help castor. There are always castor shims you can use too.
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Old December 30th, 2004, 08:19 AM   #33
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im pretty sure the bearings in balljoint beams are different sizes, the bottom arms have bigger ones. so you would have to turn the beam upside down, not swop the arms over.
it is entirely possible i think, BUT the balljoints would now be pressed in from the wrong direction, and could pop out. with a k+l it has aleady been said the arms are very close in length, so would have less of an effect. i still recon you would need to cut the framehead, so it seems a bit pointless.

as for the size of the piecut, i figured it out as being about 1-1 1/4"
i think nick pretty much totally covered the piecutting business, but im going to be removing the tray either side of the framehead when i do El greenie as well.
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Old December 30th, 2004, 04:02 PM   #34
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Nick, what do you mean by cutting a slit in the bottom.

Also I wonder about the Drag'N bug now. [img]style_emoticons/<#EMO_DIR#>/funny.gif[/img]
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Old December 30th, 2004, 05:17 PM   #35
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Quote:
Originally posted by Jon@Dec 30 2004, 08:02 PM
Nick, what do you mean by cutting a slit in the bottom.
<div align="right">Quoted post</div>
Notice on the inside bottom of the tunnel (inside the framehead) there's a slit cut going across there.


The bottom of the tunnel is not flat, it's kind of curved. It'll be impossible bending the framehead as is because of this without the use of fancy equiptment, so by cutting a slit on the bottom you can easily bend it upwards now (then reweld shut when done).

Also if anyone wants to bend their framehead, I places a stack of tires (maybe at least knee high) on the very front of the framehead, then put weight near where the piecut is at on the framhead. That way the frame will bend downwards at the piecut area. I probably put at least 300lbs of weight (using bags of sandblast media and myself) so I can weld the thing shut. Without the weight the chassis will just spring back to flat level, a little tricky getting it to weld while jumping up and down the chassis [img]style_emoticons/<#EMO_DIR#>/wacko.gif[/img]
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Old December 30th, 2004, 06:24 PM   #36
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<div class='quotetop'>QUOTE</div><div class='quotemain'>a little tricky getting it to weld while jumping up and down the chassis [/b][/quote]

Too bad you have no pics of that!! [img]style_emoticons/<#EMO_DIR#>/funny.gif[/img]
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Old December 31st, 2004, 04:32 PM   #37
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I just can't bring myself to even consider cutting the frame head. This just seems kinda scary to me. I just picture it braking off. I know its welded on and all that it's just kinda severe.

What I have come up with is an idea where I could take a piece of tubing equal to the O.D of the beams tubing and cut a section out of it length wise leaving most of it intact so if I were to set it flat on a table it would be about 1.75 or so thick. Then weld it on the back side of the bottom tube to act as a super sized cator shim. Next cut loose the center mounting brackets and trim, pivot them downward so that they still line up with the frame heads mounting holes. Resulting in a beam thats leaning back some and still bolts up to the frame just like the stock one.

Yes I am sure it will work and i don't think its a lotta work. I just gotta decide what I am gonna do.
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Old December 31st, 2004, 07:59 PM   #38
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With any welding skills at all,I can't see it being a big problem The cut area will be in compression once it's done and on the ground. You could always plate it up some. I think your idea could work OK too though.
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Old December 31st, 2004, 08:28 PM   #39
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Remember that when you take a stock car and lower the front in proportion the the rear you LOSE castor, so if you flip the beam and then proceed to A) put shorter tires on front B) put taller tires on back or C) lower the front more than the back you'll GAIN castor.

Also remember that a car that's been slammed up front will have trailing arms that angle upwards.
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Old December 31st, 2004, 08:58 PM   #40
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Jon, I'm not saying I'm a better welder than you but I'll come weld it for you if you want. I am certified and have been welding for a living for over 12 years and I have been welding heavy equipment attachments for Caterpillar for almost 7 years. It seems like it is a pretty straightforward deal (famous last words, I know [img]style_emoticons/<#EMO_DIR#>/funny.gif[/img] )
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Old January 1st, 2005, 05:49 AM   #41
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Charlie, you are with out any doubt a better welder than me. No offense taken.
I just get bad feeling about things like this some times. Of course there is no way in hell my 110 mig welder could handle this, so I would have to do it at work with a 220 Arc. If you want when the time comes you could come up to my work and do it there. Maybe on a saturday or something. I would still have to pull the body off and everything. Then throw the pan on the roof of car. Might be awhile though.

I still kinda like the Idea of having a big ass spacer behind the bottom tube though. [img]style_emoticons/<#EMO_DIR#>/Idunno.gif[/img]
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Old January 1st, 2005, 12:15 PM   #42
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I would think a 110 mig welder with flux core wire for deeper penetration should do the job just fine.
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Old January 1st, 2005, 01:55 PM   #43
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Where did this 10 degree figure come from ? I have been working some of this out and I was jsut curious. Was it a guess ?
For some reason it looks like a little more. But I am working out a pivot from the top tube of the beam. Trying to work out this layed back beam idea. It will work Just the bolt holes will need to be lined up afterwards.

Also why couldn't the wedge be cut a little further forward on the frame head. Like right behind the mounts wheres still kinda straight before the taper..... Know what I mean, the widest straight section. Looks like you could cut the wedge out of that and just simple lay it back some without a bottom cut.
I am not really concerned with getting any extra lowering as I have dropped spindles, dropped beam and 14" wheels. I will be able to set this thing on the ground anyway. [img]style_emoticons/<#EMO_DIR#>/thumbsup.gif[/img]
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Old January 2nd, 2005, 06:23 PM   #44
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<div class='quotetop'>QUOTE</div><div class='quotemain'>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.[/b][/quote]

That was where the 10 degrees came in. I believe he is saying that a stock Bug has 6 degree positive castor. When the arms are flipped you get around 6 degrees minus. In order to approach a "stock" castor setting "you are needing to push the top of the framehaed back by about 10 degrees". (seems like 12 degrees would be closer, but it's dez's article). Either the top of the beam has to go back or the bottom has to come out....pick your poison.

OK...?
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Old January 2nd, 2005, 06:30 PM   #45
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Thanks I kept coming up with twelve myself but I kept reading this 10 degree thing and I didn't consider the lowering part.
Thanks agian.
I think I will be doing the lower tube spacer thing. Thsi should keep the steering bov in the correct place to line up the steering shaft. just turn it a little bit. [img]style_emoticons/<#EMO_DIR#>/thumbsup.gif[/img]

Now My next big question is should I use my 4" narrowed beam ? Doing so will allow me to cut down the tie rods to the desired length, instead of welding in extentions. Of course this is just an opinion question.
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Old January 2nd, 2005, 09:26 PM   #46
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Remember what he said, when you lower the car you move the degrees a little as well. so that may be where the 10 came from, 10+ the lowering = 12ish

I'll re-read again to be sure.
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Old January 3rd, 2005, 03:10 AM   #47
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right, micheal is kinda there with it 6degs, then you flip it, and youll end up with 6 the other way. BUT lower it a bit and it will knock a couple of degrees off that. (the reason that costor shims exist)

ive been thinking about what youve said jon, and i like the idea of your beam with a integral spacer being 'bolt-on', but it will need a good bit of work to make it so- i think the beam clamps may need to be fabbed from scratch. i things work out well and i do end up producing these, i may try doing your way, as it would make it a nice easy bolt on product.
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Old January 3rd, 2005, 10:36 AM   #48
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This is the mechanical engineer side of me talking, so take pot shots if I don't see the whole picture.

What's laid out here, and the way it has been discussed is FANTASTIC! If we had more detailed presentations like this, there would be a lot fewer questions.

However, having said that, I still have one basic problem with the entire "flipped" front end design.

I realize the trailing arms are forged, and are fairly strong in their applications. However, as designed from the factory they are TRAILING arms, not LEADING arms. By this point alone you are changing the basic function of the part and I worry about a failure.

As a tire approaches a pothole (curb, rock, dead body, etc.) the tire will hit the obstruction and PULL the trailing arm rearward as the force is dissipated through the suspension. This loads the trailing arms in tension where you are relying on the pure tensile strength of the forged parts to survive. They do, and have for many billions of miles on these cars. No argument there. Also why do you always see trailing arms as, well, "trailing"? The closest you get to forward facing arm is one that is at 90 degrees like a dual A-arm setup.

Now, people are taking the trailing arm, and flipping them around. As the tire approaches the same obstruction and strikes it, the arms will now be loaded in compression, not tension. You are going to rely purely on the bending strength of the material, insteal of it's tensile properties. As you may know, this is not typically equal, and tensile strength is almost always greater. As the arm reaches it's failure limit, it will bend, then buckle. Thankfully, this should not create a purely unsafe condition since the forged material will bend, rather than suffer brittle failure. You'll know you screwed it up before it wrecks something. This may not be a concern to those who live in climates where the roads aren't a blown-apart pothole riddled mess, but I don't live there. I live in Michigan where expansion joints are more like speed bumps, and pot holes commonly destroy rims.

To think about it in laymans terms it is usually better to pull something up over an obstruction than ram into it directly. You could compare it to a wheelbarrow being pushed up to a curb with a full load. It may be easier to pull that load up backwards, and allow the wheel to roll up and over, than run at it head on and hit it directly. The force being distributed to your arms is better in tension than compression.

That may not be a great analogy, but it's how I visualize it.

If this has been covered before, I haven't seen it. Try to keep the rock throwing to mainly small rocks if possible.
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Old January 3rd, 2005, 04:54 PM   #49
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Griznant, I agree with you, I understand what your saying. The only factor you didn't address is that the trialing arms are on a pivot and they are usually angled upwards. So when slammed hard against a bump they should pivot upwards and back. Yes they are working backwards but I think it will be OK in lowered situation.
Yes they will be under more stress than they ordinarily would be though.
I think it a stock hieght situation they would be under quite a bit more stress.

Dez, If you use my idea you will have to give me credit or something.
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Old January 4th, 2005, 02:12 AM   #50
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i agree with jon totally on that. when the car is slammed, they actually lean back about the right amount for the force to be upwards in relation to the arm- remember, any bump you hit, the forces are a vector, with vertical and horisontal components. the horisontal component is far larger, but the horisontal component pulls it round far enough so it isnt a 'dead' load on the end of the arm.

and jon, i surely would give you credit, you thought of it!!
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