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Originally posted by 2highToy:
<STRONG>Why wouldn't you want the pinion to be pointed at the x-fer case throughout its range of motion with a normal driveshaft too? So by running parallel links it doesn't keep the same pinion angle but converging links do? So how do you determine the ideal convergence angle of the upper and lower links (when looking at them from the side)</STRONG>
Anyone ??? <IMG SRC="smilies/confused.gif" border="0">

<IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0">
 
Originally posted by 2highToy:
<STRONG>Anyone ??? <IMG SRC="smilies/confused.gif" border="0">

<IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"></STRONG>
i all ready answered this, sort of. Read above dude.
 
Originally posted by ToyFamily:
<STRONG>Hey guys this is an example of the benefits of the bent link and how I was talking about making it like a fin for strength.
<IMG width=494 height=348 SRC="http://www.pirate4x4.com/ubb/uploads/linkpic.jpg"></STRONG>
Benefits???? Ok dude, mount the link on top of the axle housing and get a flatter roll axis and less anti squat and the same amount of clearance. A straight tube is always stronger than a bent one. GET IT
 
Originally posted by 2highToy:
<STRONG>Why wouldn't you want the pinion to be pointed at the x-fer case throughout its range of motion with a normal driveshaft too? So by running parallel links it doesn't keep the same pinion angle but converging links do? So how do you determine the ideal convergence angle of the upper and lower links (when looking at them from the side)</STRONG>
You can use a compass, a tape measure and a piece of paper to figure it out. ; )
I like the pinion to rotate so I don't get alot of angle in the U-joint at full travel. That little difference in strength and clearance can be the difference between a machine that can hammer thru some nasty spots and a machine that spits out parts while hammering.

[ 10-19-2001: Message edited by: dirtrod ]
 
Originally posted by 2highToy:
<STRONG>Anyone ??? <IMG SRC="smilies/confused.gif" border="0">

<IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"> <IMG SRC="smilies/beer.gif" border="0"></STRONG>
With a regular drive shaft the pinion angle hs to be the same (or close to) the flange on the t-case. The reason you can point the cv is cause your suppost to have it pointed straight at the t-case (or within a few degrees)
 
Originally posted by dirtrod:
<STRONG> I like the pinion to rotate so I don't get alot of angle in the U-joint at full travel. </STRONG>
If your axle housing rotates that much through it's range of travel then under articulation it is going to be trying to twist. It seems like your links could be fighting each other enough to limit articulation.
 
I like the pinion to rotate so I don't get alot of angle in the U-joint at full travel. That little difference in strength and clearance can be the difference between a machine that can hammerle thru some nasty spots and a machine that spits out parts while hammering.
EXCELLENT post, Dirtrod. Seems like a lot of folks sweat the angle/oiling issues, and the pinion/driveline angle, but don't consider the relative strength of the u-joint at various degrees of bend. Yeah, I know, keeping all of these things in mind at onece is tough, but the best designers do.

Randii
 
Originally posted by ToyFamily:
<STRONG>Does anyone see anything wrong with this concept, I have been kicking it around for about a year.

<IMG width=489 height=526 SRC="http://www.pirate4x4.com/ubb/uploads/linksktch.jpg"></STRONG>

Toyfamily, you theif! You plagerizing-rip-off artist! You know you stole that idea
(picture) right outta my brain! arg..

Actually, my idea is sooooooo rip-off close
to your pic, (and I got my idea from the
currie long-arm front link; but they do theirs below the axle-yuck)

I've had the (yours) same exact idea in my
head for about 2 years now... I even bought
some 1.75 x .375wall dom tube for the links.
I'm using 1.250 aircraft-heims for it. I too
had thought the mounts should-be below axle
centerline, but after seeing lots of others
done in all fashions, I think staying above
will be fine. and the 90' bend thing, it
doesn't have to be 90', mine will probably be
around 45'. it's funny to see someone
else's sketches, and they look exactly like
your own..... And just for reference.
Sam's "slinky" from Sierrarockcrawlers.com
rig is built just like deserttoys rig (as for
the rear links)... pretty much zero rear steer. now the spring-issue could use a look
at maybe..

--Sherpa
 
OK guys - heres just a few numbers to thow at the effects of converging arms (when looking from the side) giving unwanted anti squat.

Lets say you throttle it a bit to punch up a hill with a modest 100ftlb in a modest 50 to 1 overall reduction this get a torque in the rear axle of 100x50 = 5000ftlb which has to be constrained by the rear links.

Now say your links converge and are 4ft long, to resist the torque the arms will lift at the chassis at the convergent point. This lift will be 5000 divide by 4 = 1250lb which will be lifting up 4 ft in front of the rear springs on the chassis and unloading the rear springs by the same 1250lb. This means that instead of the rear axle supporting all its weight above the axle 1250lb of it is supported 4ft in front of it which takes weight off the front axle and loads more on the back.

say there was 2500lb on the rear suspension and 1500lb on the front before you throttled it with the rear lifting up 1250lb at the 4ft mark this will (now say the wheelbase is 8ft long) unload the front suspension by 625lb and throw this extra weight on the rear so now you have 875lb on the front and 3125lb on the rear. Now this is BAD you want the weight on the front axle to drive up hill not the rear and the anti squat is doing the exact opposite.

This calc was done at modest torque and gearing and will get much much worse with more right boot.

The other thing this does is the 1250lb not going through the rear springs will unload the rear springs (say each spring is 300lb/in times 2 is 600lb/in) now 1250divide by 600 = 2 inches (this is ignoring the weight transfer effect from above cause my brane hurts) thus lifting the rear by 2 inches which increases your effective rear lift thus the rear angle of the arms giving you more anti squat by the arms pushing up on more of an angle which will lift the rear more and transfering more weight to the rear tyres etc etc . Which is again BAD.

The above calc is very rough but im sure that the numbers are about right.

Believe me if you want to get it awn and throttle it up hills you have got to get the power to the ground and anti squat is the killer. Get some videos of blokes with mega lift and buckets of anti squat throttle it and watch that back axle walk and the rig go no where.

Sam
 
More numbers!!

The effect of the angle of the links (when looking from the side) isnt as great as the effect of converging arms on anti squat.

Say the same 100ftlb at 50:1 gives 5000ftlb at the axle. If we have 36in tyres this gives a tyre radius of 1.5ft. So that the forward push on the links from the tyres will be 5000 / 1.5 = 3333lb.

If the same 4ft links are at an angle coming down from the chassis to the axle with a 1ft drop then the lift on the chassis will be about in the ratio of 4 to 1 so that with every 4lb pushing you will get 1lb lifting at the chassis mount point.

So with 3333lb pushing you will get 833lb lifting at the chassis. And if you mounted all the links on top of the axle to get the arms as horizontal as possible I doubt that you will have 1ft drop from the chassis mount point to the axle mount point. So that the 4 : 1 ratio should be much less. So that the 833lb should also be much less in reality.

This compares with the 1250lb lift caused by the convergent arms which if you do have converging arms to get the pinion always facing the transfer you will always get and there is no other way around it.

Sam
 
Originally posted by Strange Rover:
<STRONG>More numbers!!

The effect of the angle of the links (when looking from the side) isnt as great as the effect of converging arms on anti squat.

Say the same 100ftlb at 50:1 gives 5000ftlb at the axle. If we have 36in tyres this gives a tyre radius of 1.5ft. So that the forward push on the links from the tyres will be 5000 / 1.5 = 3333lb.

If the same 4ft links are at an angle coming down from the chassis to the axle with a 1ft drop then the lift on the chassis will be about in the ratio of 4 to 1 so that with every 4lb pushing you will get 1lb lifting at the chassis mount point.

So with 3333lb pushing you will get 833lb lifting at the chassis. And if you mounted all the links on top of the axle to get the arms as horizontal as possible I doubt that you will have 1ft drop from the chassis mount point to the axle mount point. So that the 4 : 1 ratio should be much less. So that the 833lb should also be much less in reality.

This compares with the 1250lb lift caused by the convergent arms which if you do have converging arms to get the pinion always facing the transfer you will always get and there is no other way around it.

Sam</STRONG>
THANK YOU SAM!!! I am building a rear 4 link/60 setup right now and this type of good technical post is waht I need! I do want a little bit of clarification. What you are saying is that for the purposes of four wheeling the upper and lower links should be roughly parallel, and that anti-squat is bad for four wheeling, right? My upper and lower links will be sloped down from the frame to the axle, but I can make them parallel if that would be best. If you need info on my rig to help I am running the stock 4.0 engine, the AX-15 tranny, and the stock np231 (for now), the rear (and front) will both be 60s, the rear control arms will all be roughly 45 inches long. My crawl ratio is a pathetic 60 to one. Thanks.
 
I threw a few numbers around just to demonstrate what anti squat actually does. When you gas it and have anti squat in the rear the effect is the same as if you moved the rear axle forward on the rig and had a big honkin rear overhang. Anti squat takes weight off the front and loads it on the rear because part of the weight the rear springs support is actually supported where the links attach to the chassis ie forward of the rear axle.

It dosent really mater what the numbers and ration and lengths you end up with but you should understand what anti squat is, what causes it, and how to minimise it because it is the difference between building a four link that can flex and one that can flex and hook up and get the power to the ground when you gas it.

To minimise the anti squat the upper and lower links should be parallel. The biggest cause of antisquat is using links that converge to one point on the chassis (when looking from the side)

The other cause is the links coming down from the chassis to the axle on an angle although this dosent cause as bad an effect as converging links. If the links came down at an angle of 45 deg this would be really bad but if they dropped by say 6 to 10 inches over a 45 inch long arm then this would be good.

If the arms were totally horizontal and parallel then you would have no anti squat and the rig would squat on the rear springs when you gassed it (cause there is no lift from the links to help). This may not be such a good thing either cause as the rig squats on the rear springs you will again get a weight shift to the rear so some anti squat could be a good thing.

Generally to build the links and fit everything into your rig you will have the arms coming down at a bit of an angle from the chassis to the axle and you probable will have them converging a little bit as well so I feel that just fitting everything in gets enough anti squat and you should just try to minimise it.

Sam
 
Originally posted by Strange Rover:
<STRONG>I threw a few numbers around just to demonstrate what anti squat actually does. When you gas it and have anti squat in the rear the effect is the same as if you moved the rear axle forward on the rig and had a big honkin rear overhang. Anti squat takes weight off the front and loads it on the rear because part of the weight the rear springs support is actually supported where the links attach to the chassis ie forward of the rear axle.

It dosent really mater what the numbers and ration and lengths you end up with but you should understand what anti squat is, what causes it, and how to minimise it because it is the difference between building a four link that can flex and one that can flex and hook up and get the power to the ground when you gas it.

To minimise the anti squat the upper and lower links should be parallel. The biggest cause of antisquat is using links that converge to one point on the chassis (when looking from the side)

The other cause is the links coming down from the chassis to the axle on an angle although this dosent cause as bad an effect as converging links. If the links came down at an angle of 45 deg this would be really bad but if they dropped by say 6 to 10 inches over a 45 inch long arm then this would be good.

If the arms were totally horizontal and parallel then you would have no anti squat and the rig would squat on the rear springs when you gassed it (cause there is no lift from the links to help). This may not be such a good thing either cause as the rig squats on the rear springs you will again get a weight shift to the rear so some anti squat could be a good thing.

Generally to build the links and fit everything into your rig you will have the arms coming down at a bit of an angle from the chassis to the axle and you probable will have them converging a little bit as well so I feel that just fitting everything in gets enough anti squat and you should just try to minimise it.

Sam</STRONG>
Thank you. Finally, a great old style hard-core POR tech post...
 
yea ggod post Sam , I think people have asked the question of set up many times but the response is always "depends on the variables" never the basic "what you need to do" then add into account your variables.

I worked on setting up my housing last night and if I keep the fire burning like I have I will have my link set up done by the end of the week. I don't think I will be running the links to the back of the housing like I wanted because of intereference. I want to have the links out wide and the coilovers as wide as poss for a stable rig I have the 16" travel shocks so I got "'s to spare. I will post pics.

[ 10-23-2001: Message edited by: ToyFamily ]
 
Where can I get general info on this stuff?

This is all very interesting discussion, and I am learning. But are there any good references out there for a home fabricator like myself to better understand the concepts?

Thanks,
Phil
 
Re: Where can I get general info on this stuff?

1TONTJ said:
This is all very interesting discussion, and I am learning. But are there any good references out there for a home fabricator like myself to better understand the concepts?

Thanks,
Phil
READ THE SUSPENSION GOD THREAD, AND BUY THE MILKIN BOOK CALLED GROUND VEHICLE DYNAMICS.
 
Sams calculations are good from what I can tell, but they consider a rig who is unbalanced to the rear. If you are unbalanced towards the front like most rigs the effects will be oposite of what he says, this is do to the anti squat will be acting behind the center of the vehicles mass intead of infront of it. All this means is that his assumptions like all of ours dont take into all the variables and consiquances of this very complex system. with your calculations you woulld have the entire rig being lifted from the antisquat whcih I Havent seen from a 4x4 setup before.
 
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