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kingmeirl
January 21st, 2009, 11:34
I have a rusty's 8" lift and the rear leafs are really curved (no blocks). My question is when I am going to change the shackle angle from almost 0 degrees to 45 degrees, wouldn't it also benefit me to make the shackles longer? longer shackles would allow the leafs to stretch all the way out for full flex, right? or am I wrong?

builder
January 21st, 2009, 12:56
They will give you more flex yes, which you will probably need since 8" leaf pack wont flex much anyway.

kingmeirl
January 21st, 2009, 13:24
sweet, and 45 degrees is the target angle?

dinorl007
January 21st, 2009, 13:36
i believe the more angle u have the softer the ride, have u checked on shackle relocation brackets? i have them and it gave me about an inch in lift, but the shackle angle went from almost straght to 45 deg and improved the ride and flex greatly, they have them in the vendors forum. hth

kingmeirl
January 21st, 2009, 14:09
I have looked at those, but I am not looking for any more lift, just more flex. Also, the way my leafs are so curved, I want to make the shackles longer. I am working out the geometry now to see how much longer I want them. Those brackets just change the angle. I am going to have to completely cut the originals out and make my own bracket much higher and farther forward than what those bolt in brackets could offer. but maybe I could use those and weld them where I want them?

swbooking
January 21st, 2009, 14:12
Your running 8" leaf packs with stock shackles? Im surprised you have any shackle box left...

I would look into getting some RE Boomerangs (or similar style TnT etc) and the shackle relocateors from Offroad Engineering:

http://naxja.org/forum/showthread.php?t=956630

http://www.naxja.org/forum/showthread.php?t=955999

kingmeirl
January 21st, 2009, 14:23
ya, i bought the jeep this way (stock axles too!). They look to be aftermarket shackles (rusty's) but are bolted up in the stock location. They are 4 3/4" long and look to be at a 75 degree angle going the wrong way.

kingmeirl
January 21st, 2009, 14:25
From the looks of the pics, won't the lower part of the shackle hit the bracket before full compression can be achieved?

userbmx1315
January 21st, 2009, 14:29
i'd look at leaf if you want more flex. 4.5 in leafs, 1.5 u bolt elim. shackle relocation box and 1.5 lift shackles. should put u at the same lift and will flwx better then the 8" packs.

keep in mind that the angle of the shackles will effect your lift. (not much tho)

swbooking
January 21st, 2009, 14:34
Did you look at more then the first page on the second link I gave you? There are pics on pgs. 2, 4, and 5 of rigs flexed out with theyre kit. Doesnt look they have any binding problems.

I would second what userbmx1315 said. Look in getting smaller leafs.

kingmeirl
January 21st, 2009, 15:58
smaller as in flatter? how would flatter leafs flex more? I could understand less leafs so they would bend easier.

kingmeirl
January 21st, 2009, 16:03
I see why the shackle at a 45 degree angle would allow for more flex, It takes less movement of the leaf to move the shackle up and down in relation to the vehicle at that angle. As opposed to the shackle being at 90 degrees, where the leaf would push the shackle horizontal to the vehicle. Basically, its easier to rotate the shackle than compresss the leaf.

TheAlmightySam
January 21st, 2009, 17:13
The shackle angle should be 90 to the angle of the leaf. The angle of the shackle to the body is irrelevant. At 90 to the leaf, the movement of the leaf can be most effectively transferred into the shackle with minimum upward forces applied to the shackle (and thus, the body), giving both the smoothest ride and the greatest flex.

Of course, this isn't always possible, but in theory, that's your target. Most like to be a little past 90 so that on suspension droop, the shackle doesn't decide to push the wrong way and invert.

kingmeirl
January 21st, 2009, 17:50
ok, so i've been doing a lot of geometry. Ride height the leaf is 49" bolt to bolt. The leaf flat would be 53" long. With my stock 80 degree (reversed) shackle that is 4.75 inches long, and the leaf flat, I would only have about 9 inches of travel up. If the same shackle were place in the 45 degree forward position, I would only have roughly 11 inches of travel up. I would also gain 2 inches of droop. Not saying I am going to do this, but the math shows that if I replace my 4.75 inch shackle with a 36" shackle and mount it at a 27 degree angle (forward of course) then I would have 16 inches of travel up and 16 inches of droop (from ride height). That is 8" from the leaf and 8" from the shackle. That is only if my leaf were flat. And these numbers will only apply to my same size leaf, but you get the idea.

kingmeirl
January 21st, 2009, 18:00
The shackle angle should be 90 to the angle of the leaf. The angle of the shackle to the body is irrelevant. At 90 to the leaf, the movement of the leaf can be most effectively transferred into the shackle with minimum upward forces applied to the shackle (and thus, the body), giving both the smoothest ride and the greatest flex.

Of course, this isn't always possible, but in theory, that's your target. Most like to be a little past 90 so that on suspension droop, the shackle doesn't decide to push the wrong way and invert.

If the shackle were at 90 degrees to the leaf, then the leaf would have to push the shackle out before it pushed it up, which would negate the whole physics behind moving it in the first place, right? You want the shackle to move up with compression of the leaf, not out. And if it were at 90 degrees you would have almost no droop before the shackle was maxed out in that direction, or started inverting like you said.

I'm just trying to find the physics in a leaf and shackle and use it to our advantage instead of just doing what everyone else does. I'm really sorry if someone takes this wrong, but I just want to help.

TheAlmightySam
January 21st, 2009, 18:16
If the shackle were at 90 degrees to the leaf, then the leaf would have to push the shackle out before it pushed it up, which would negate the whole physics behind moving it in the first place, right? You want the shackle to move up with compression of the leaf, not out. And if it were at 90 degrees you would have almost no droop before the shackle was maxed out in that direction, or started inverting like you said.

I'm just trying to find the physics in a leaf and shackle and use it to our advantage instead of just doing what everyone else does. I'm really sorry if someone takes this wrong, but I just want to help.

Why does it matter which direction the shackle is pushed? The goal is to allow the maximum fore-aft travel of the rear spring eye. When the spring is compressed, it will most easily transmit force to a shackle that is placed at a 90 angle to it.

Think back to physics class: Moment = F x r, where all three quantities are vectors. The greatest moment will occur when F and r are perpendicular to each other. Imagine a wrench on a bolt. By pushing purely in one direction on that bolt, as the leaf spring pushes purely in one direction on the shackle, it takes more force to push against a wrench that's in any position other than at a 90 angle to your arm. The same goes for the leaf spring.

Of course, as mentioned, this is not always practical. Knowing how much the rear eye will move forward during downtravel tells you if the shackle will reach the limit of its movement. Once the shackle and spring are colinear, of course, the spring can move no further.

So, ideally, 90 to the spring, but this is not always practical.

userbmx1315
January 21st, 2009, 19:20
heres what my shackle angle looks like. dodge van main and an s10 bastard.
http://i57.photobucket.com/albums/g217/userbmx1315/100_0010.jpg?t=1232594325

kingmeirl
January 21st, 2009, 19:24
I see what you are saying and you are right about the forces, but in the case of the leaf and shackle, you are not trying to just compress the leaf, you can also get up and down travel for the axle if the shackle moves in the same direction. So, if the shackle is at 90 degrees, and the leaf flattens the shackle will not travel up, it will travel horizontially. But if the shackle is at 45 degrees, and the leaf flattens, then the shackle will be forced to move up, giving you more travel which is what we are trying to accomplish.

kingmeirl
January 21st, 2009, 19:40
http://i509.photobucket.com/albums/s338/kingmeirl/untitled.jpg

A is the distance the leaf will travel when flattened
B is the direction the shackle will move when the leaf is flattened
C is the distance the leaf will move up when the shackle is rotated

A and C need be the greatest number for the greatest amount of 'flex'
B will change only when the shackle is repositioned or lengthened.

A will not change unless leafs are changed. If the shackle is at 90 degrees, C will be minimal. Notice how his shackle is at about 60 degrees. I would be willing to bet that he gets about 2 more inches of up travel than if his shackle were at 90 degrees.

xcm
January 21st, 2009, 22:53
I would look into getting some RE Boomerangs (or similar style TnT etc) and the shackle relocateors from Offroad Engineering:

http://naxja.org/forum/showthread.php?t=956630

http://www.naxja.org/forum/showthread.php?t=955999

not to be confused w/... you guessed it, offroad engineering! http://www.offroad-engineering.com/ ... a shop specializing in racing shocks, they did my fox's for me, and are good guys....

ColoradoRaptor
January 22nd, 2009, 05:48
heres what my shackle angle looks like. dodge van main and an s10 bastard.
http://i57.photobucket.com/albums/g217/userbmx1315/100_0010.jpg?t=1232594325

You need a longer shackle or a relocator BAD!!

userbmx1315
January 22nd, 2009, 11:23
i'm getting new springs with a little more arch. i know that archs are bad but its a little more lift. its actally a bastard pack from a set of front 85 yota springs. its all i could afford right now.

kingmeirl
January 22nd, 2009, 16:34
what do you mean the archs are bad? Also, on that other thread someone said something about flatter leafs flex more, is that true? I would think a spring with more arch would have greater travel.

builder
January 22nd, 2009, 17:36
Absolutely a flatter spring flexe's better.think about it for awhile and it will come to you why a flatter pack flexe's better.

kingmeirl
January 23rd, 2009, 05:34
well, i slept on it and still can't think of why a flatter leaf would flex better. less leafs, yes, but flatter? please explain.

ColoradoRaptor
January 23rd, 2009, 06:34
Ok, for crying out loud..... the flatter the spring the less force required to flex it out!! The more arc the more force required!! Ok, and just in case you ask the more leaves the higher the load capacity.... There are other variables but that is the basics

RCP Phx
January 23rd, 2009, 06:40
heres what my shackle angle looks like. dodge van main and an s10 bastard.
http://i57.photobucket.com/albums/g217/userbmx1315/100_0010.jpg?t=1232594325

Shackle angle looks great,what you do need are some boomerang shackles.Also I dont see any spring clamps?

kingmeirl
January 23rd, 2009, 10:18
Ok, for crying out loud..... the flatter the spring the less force required to flex it out!! The more arc the more force required!! Ok, and just in case you ask the more leaves the higher the load capacity.... There are other variables but that is the basics

to flex it out, yes. i understand that. but if it takes 100lbs of force to make a flatter spring bend 3 inches to be flat, and the same 100 lbs of force on a more curved spring would also bend it 3 inches, but it would not be flat, then how can a flatter leaf give you more flex? the flatter spring would only give you 3 inches of travel and the more arched spring would give you the same 3 inches of travel with the same force. EXCEPT the more arched spring would be able to flex more than 3 inches once more force is applied.

builder
January 23rd, 2009, 14:49
Suspension Tuning - NAXJA Forums -::- North American XJ Association (http://www.naxja.org/forum/showthread.php?t=23381&highlight=leaf+spring+flex) this should make it clear!

kingmeirl
January 23rd, 2009, 16:20
apparently "Nay" agrees with me in that link you gave me, but just for questions sake: lets say a flatter spring does give you more droop. The only reason you would want more droop is if your fenders get in the way of the tires. If a flatter leaf only gave you 8 inches of droop and an arched leaf only gave you 8 inches of compression, which would you choose? I hope you didn't say droop because at full droop, there is no weight on the tire. If your suspension was made to travel down, then there would be less and less traction as you drooped.

Also, when the drivers side droops and the passenger side compresses, is there anything to combat the effects of the flat leaf on a rotating axle? wouldnt the leaf want to rotate with the axle at the u-bolts?

builder
January 23rd, 2009, 17:17
I give! if you still don't get it like " nay " didn't. then you never will. flatter leaf packs flex better both ways.

kingmeirl
January 24th, 2009, 07:05
i'm really sorry man but i'm stubborn as hell. lol. I think I will just go to the junk yard and get some different size leafs and come back and mock them up. then i can put a scale under a jack and jack them up and see how much they flex with the same forces. It is very possible that you are right, but I just can't see it in my head. I do appreciate you trying to explain this to me and I apologize if you got frustrated with me...

XJEEPER
January 26th, 2009, 06:56
Why does it matter which direction the shackle is pushed? The goal is to allow the maximum fore-aft travel of the rear spring eye. When the spring is compressed, it will most easily transmit force to a shackle that is placed at a 90 angle to it.

Think back to physics class: Moment = F x r, where all three quantities are vectors. The greatest moment will occur when F and r are perpendicular to each other. Imagine a wrench on a bolt. By pushing purely in one direction on that bolt, as the leaf spring pushes purely in one direction on the shackle, it takes more force to push against a wrench that's in any position other than at a 90 angle to your arm. The same goes for the leaf spring.

Of course, as mentioned, this is not always practical. Knowing how much the rear eye will move forward during downtravel tells you if the shackle will reach the limit of its movement. Once the shackle and spring are colinear, of course, the spring can move no further.

So, ideally, 90 to the spring, but this is not always practical.

Application experience overrules your theory. A 90 degree shackle angle = l , results in a stiff, bouncy ride. An angle more like \ is what you are looking for, ride is good, flex is good.
Debate is over.

kingmeirl
January 27th, 2009, 19:22
so has no one any experience with longer shackles?