Competition Traction Bars

[Diesel Freak]

mine being 8ft with 2 5/8 DOM 1/2'' wall they don't flex.

LOL... how heavy are those things?



I wanted to see what would be needed for a truck that had 1000 in Tq at the flywheel would need... . worst case... .





in 4x4 low range, and IF all the power went to the rear (front driveline broke) and the rear tires hooled up 100%



That would send over 54,000 foot pounds of tq through the rear carrier. Can you say busted axles!!!!



with a safety factor of 2, this would place the ladder bars under close to 30,000 pounds of compressive force (assuming the spring pack held nothing)



Minimum Moment of inertia of the 8 foot bars made from AISI 4340 steel would have to be . 943 in ^4



a solid square bar 1. 85 x 1. 85 inches would take care of it!!



and NEVER flex

 

[BigBadDodge]

Yeah but will you make wieght



BBD

 

[zstroken]

How did you arrive at 54,000 ft/lbs? What assumptions did you make?

 

[pwerwagn]

Max torque x first gear ratio x low range T-case ratio x gear ratio.

Torque is multiplied proportionatley to the ratio of the respective gear, assuming no frictional losses.

Pwerwagon... ... ... . that's true unless you have the front on the bar in a mount that allows the bar to rotate on an axis at the front. Welded to the axle at the rear.

Yeah, I realize that. I guess I've just never been fond of those setups, and they still do not allow "true" spring movement. It does still manipulate the spring movement somewhat, since the bar being welded to the lower mount also means the bar at the front *should* rise and droop at the same rate as the rear, but since it is fixed in a vertical plane it cannot. What that does is require the axle to twist as it moves up and down.



Again, with the amount of wheel travel these trucks have and the way most use them, it is fairly irrelevant.



-Jeff

 

[zstroken]

Still don't see 54,000. I end up with in the mid 20,000 ft/lb

 

[Turbo Thom]

Jeff... ... ..... it does allow for spring movement. If you will look at the rear shackle on the spring, what does it do when the spring compresses? It moves rearward, at a standing position. When the truck is in movement, it does the same thing but at a very rapid rate. Back and forth, back and forth. When this is going on the axle does not rotate, unless more power is applied than the spring can accept.



The front of the ladderbar does the same thing as the rear shackle. It moves the same, only now when excessive power is applied, whatever position the front rotating part of the ladderlink is in, it cannot allow the axle to rotate at all. Now just for demonstration, take the springs off and install air bags and coilovers, aka: BBG, and you will have the same thing. But with the rotating front bar, but you still have the OEM spring and a lot more money in your pocket.

And it is very critical not to let anything bind. None at all. Things will break. I have already proven that.



. . Preston. .

 

[pwerwagn]

Still don't see 54,000. I end up with in the mid 20,000 ft/lb

5. 61 x 2. 72 x 3. 55 x 1000 equals 54,170.

are you using the 1st gear of an auto??? then:

2. 45 x 2. 72 x 3. 55 x 1000 equals 23,xxx.





Preston,

I do realize that the shackle does allow for fore-aft movement. Yet, look at it from a purely vertical perspective. If the bar is solidly welded to the axle, if the axle moves up, so does the bar. Yes, the bar will also move rearward with the axle due to the movement of the shackle. but lets look at vertical. If the axle moves up 4", since he bar is rigidly affixed to the axle, it to would like to move up 4" (at both ends... ). It would do that if it werent fixed at the other end. So, since you have the frame end fixed, although it can move fore/aft, it cannot allow up/down. therefore the spring must absorb the difference (or the bar, if its not strong enough).

do you see my view of it??



--Jeff

 

[pwerwagn]

Preston,

I forgot to add I think your design is FAR better than a heim'd bar at both ends, in most circumstances. It does allow for far greater spring movement than an improperly designed heim jointed bar. It is nearly impossible on some setups to make a double heim'd bar work correctly, due to the fact that the distance from the front spring hanger to the centerline of the axle changes as the spring compresses, some more so than others. Some Asymmetrical springs are pretty much impossible tomake a heim'd bar work right...



Yet, I still feel that the best method is a proper length, properly mounted, double heim'd setup.



--Jeff

 

[SLangegger]

Preston,



Your setup is interesting to me. Could you post that pic to clarify a few things?

Thanks in advance

Steve

 

[zstroken]

Yep that was it. I didn't realize that first gear on a manual was that low. Thanks

 

[Turbo Thom]

pwerwgan... ... ... . good converation.



Steve... ... . I don't have a truck here with them mounted, but I'll set up some on the table and see what turns out.



. . Preston. .

 

[SLangegger]

Instead of using just one heavy bar, why not just make a bar with some supports? I. E. a triangular shaped bar?

 

[KevinLewis]

On my 74, I found a point on the frame and measured the distance from the point to the axle at full compression and full droop. I kept measuring from different distances and mounting points until I found one that lent itself well to axle movement.



-Jeff

Where abouts was that point and what was the length?

 

[BigBadDodge]

I used absolutly no math when designing and fabricating my four link :-laf



BBD

 

[jwilliams3]

Well you better next time! :-laf

 

[pwerwagn]

Where abouts was that point and what was the length?

wow, I think i need to go measure again. I do know that it wont work on the 2nd gens. The rear springs on the 74 are 8" springs, so they are way more heavily arched than a stock truck. So that means that when you compress them, the distance from teh front hanger to the center pin changes more drastically. The flatter the spring, the easier to set up bars.



All I remember is they are foward of where the frame starts to drop (its a 74 Club Cab Short Bed... ). I know I used 7/8" heims. I think It was 1-3/4" od DOM also, but dont recall off the top of my head.

pwerwgan... ... ... . good converation.

Agreed, Preston.



--Jeff

 

[pwerwagn]

Kevin,

How do you like the fox non-res 2. 0s???

 

[BigBadDodge]

I think I showed a lot of folks how tuff my system was last year at IRP



mine is a four link though, not to be confused with traction bars alone.



BBD

 

[Diesel Freak]

Instead of using just one heavy bar, why not just make a bar with some supports? I. E. a triangular shaped bar?

it can work, but while you dont have any vertical flex, you will have lateral flex... . assuming it is attached by "one" heim joint per end.



Using a square bar of the size I came up with will keep the bar from buckling in ANY direction.



You can go with a lighter piece, but it's external dimensions will be larger.



BBD, there is definately something to be said for Fabrication Experience and skills!!!

 

[Turbo Thom]

I've tried everything I know to get a picture up and it ain't working.



. . Preston. .