WaterH
Well-known member
Everything is so “engineered”. I love it.
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Dust Buggy
- Thread starter HYDRODYNAMIC
- Start date
Bebop
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8" arms ?
Shit, I thought my 10" ones were short.
I ran into the issue of not being able to find the right rate. My .750 x 36" still feels too stiff.
Other option for your tab would be to turn it 90 degrees and run the stud parallel to the trailing arm. That's what BKOR is doing on their cars.
Shit, I thought my 10" ones were short.
I ran into the issue of not being able to find the right rate. My .750 x 36" still feels too stiff.
Other option for your tab would be to turn it 90 degrees and run the stud parallel to the trailing arm. That's what BKOR is doing on their cars.
HYDRODYNAMIC
Rock Stacker
This is where detailed CAD is worth the time and headache. Putting 10lbs in a 5lb bag. I didn’t plan for the brake cables or fuel line but was able to squeeze them in.
HYDRODYNAMIC
Rock Stacker
With one shock at bump the other is hanging out at 8” on a 10” travel shock so with limit straps at 9” there is 1” of sway bar flex left.
The sway bar is a TK1 Racing KOH/Ultra4 bar 1.25" x 29 Spline at ends turned down to 1" across mid section.
The arms are 8" by name but the actual length rod end to bar center is 8.375"
The DustBuggy is tall and heavy. Full four seater with heavy lower tubes and it will be loaded with all the trail goodies.
How does yours flex? Full bump one side and full droop other?
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SHARPMACHINE
Web Wheeler
This thread makes me feel dumb. :(
You are an artist.
You are an artist.
Kreep
Rock God
This info bothers me each time I read it. I thought heat treating didn't change the modulus, just the elastic limit and fatigue strength. So heat treat shouldn't change the spring rate unless you've exceeded the elastic limit. I agree that an off road bar will likely see higher stress levels than a street bar, so maybe that was the point he was making. Still, it reminds me of the grade 5 vs grade 8 bolt discussions...
Kreep
Rock God
BTW, I've said it before, and I'll say it again. You have some of the best builds on the interweb!
Bebop
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My arms are 10" from center to rod end. Bar is way smaller than your and still feels too stiff from time to time. Buggy weighs 4500lbs.
Flexes real well although flexes more without the bar connected, obv.
HYDRODYNAMIC
Rock Stacker
I was regurgitating what I understood TK1 Racing was trying to explain.
My best guess is for street use they want a light bar as possible for weight saving and since it has minimal twist rotation they can reduce the elasticity of the bar and make it stiffer without the issue of breaking the bar.
For off-road there is more weight, more rotation, and the bars get beefier so more material can do the work.
Ghetto Fab.
No idea what I'm doing
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Wouldn't heat treat have to change the modulus to increase strength? Otherwise there wouldn't be much point to heat treating. Maybe not so much change it, but move it further up the graph. The statement "heat treat" is tricky because it can mean so many different things.
Weasel
Red Skull Member
No the modulus doesn't change. Modulus is not equal to the spring rate. The HT changes the yield and failure points. It can move it up in the Y direction and right in the X direction of your stress strain curve. The area under the curve is your toughness. Some HT just raise the yield in the y direction, strong but not very tough. Others move it in the Y and X direction strong and tough.
Kreep
Rock God
Eggsactly. So for those following along that don't have engineering degrees pretty much all steel alloys have the same torsional modulus of elasticity. You can think of this as the material's stiffness. Heat treating does not change this property AFAIK. So if you made a bunch of identically shaped steel rods of different alloys and different heat treats it would take exactly the same torque to twist them a certain number of degrees. That is until the brittle ones broke and the soft ones permanently deformed.
So all steels regardless of heat treatment have the same torsional stiffness but not all make good springs because they fail before delivering a useful amount of travel.
What I'm trying to get my head around is how a road car's sway bar is stressed harder than a buggy's. In my limited experience the road cars are lighter, have larger diameter bars and shorter arms which to me says less stress and an easier job on the heat treat...
Anyway, sorry to derail an otherwise outstanding build thread!
arse_sidewards
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Note the edit.
Also don't think of it in terms of travel, think of it in terms of twist per length of steel (for a fixed diameter bar).
Weasel
Red Skull Member
Road car have higher 'input' loads. Ie they are hooked to a pretty consistent sticky surface and travel is more limited. Hence the load might be larger but the bar doesn't have to react through the same amount of travel that a off-road bar would. The load on a off-road bar maybe be less but the range of motion is much larger.
And the edit, while technical correct, a spring that has failed has also yielded.
And the edit, while technical correct, a spring that has failed has also yielded.
arse_sidewards
Red Skull Member
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What I was getting at is that a spring can yield without failing. I think we've all done that to a leaf spring or two.
subybaja
E. Spengler
No degree here, so I'm having a hard time getting my head around this.
So you're saying that a 1" high-carbon bar through-hardened to 70rc vs the same bar annealed with take the same amount of force to twist 2*? Never mind the inevitable shatter/pretzel...
And that high-carbon hard bar vs a dimensionally identical low-carbon bar?
Weasel
Red Skull Member
No he's saying modulus of elasticity doesn't change. The relationship between stress and strain is the same for all steel regardless of HT up to the yield point. That's how the modulus is defined. The modulus is the slope of the line on a stress strain curve up to the yield point. The yield point is what moves.No degree here, so I'm having a hard time getting my head around this.
So you're saying that a 1" high-carbon bar through-hardened to 70rc vs the same bar annealed with take the same amount of force to twist 2*? Never mind the inevitable shatter/pretzel...
And that high-carbon hard bar vs a dimensionally identical low-carbon bar?
Kreep
Rock God
No degree here, so I'm having a hard time getting my head around this.
So you're saying that a 1" high-carbon bar through-hardened to 70rc vs the same bar annealed with take the same amount of force to twist 2*? Never mind the inevitable shatter/pretzel...
And that high-carbon hard bar vs a dimensionally identical low-carbon bar?
Yes, that is exactly what the math says as long as the stress is within the elastic limit. But what I don't know is the exact point when they exceed that limit and fail by breaking or permanently deforming. So maybe they're the same for 15* or maybe it's only to 1/2*.
What I was getting at is that a spring can yield without failing. I think we've all done that to a leaf spring or two.
I get your point because both other failure modes (brittle fracture and fatigue) result in a bar broken in half. But I personally feel like if a sway bar yields it is done. Who wants to drive around leaning arse sideways???
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arse_sidewards
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I was thinking more along the lines of bent=fix later and broken=stop and fix now.But I personally feel like if a sway bar yields it is done. Who wants to drive around leaning arse sideways???
Bebop
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I have twisted mine permanently and it makes for weird reactions, that's for sure...I get your point because both other failure modes (brittle fracture and fatigue) result in a bar broken in half. But I personally feel like if a sway bar yields it is done. Who wants to drive around leaning arse sideways???
arse_sidewards
Red Skull Member
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Can't be much worse than a broken torsion bar and the sway bar holding that side of the vehicle up.
HYDRODYNAMIC
Rock Stacker
Back to where I should have been. Double shear tabs on the sway bar links. Teflon lined FK alloy rod ends. Total flex on the bar to lift a tire off the ground is 19°. The bar will flex some more if I push down on the tire. When the bumped tire is fully loaded and pivoting on the air bump, I expect the bar to flex more probably to the point the limit straps engage.
TK1 makes nice stuff, good choice!
I like the "wobble stopper" you have on the lower links.
I like the "wobble stopper" you have on the lower links.
HYDRODYNAMIC
Rock Stacker
Limit straps are mounted in the rear.
24” quad wrap Kartek branded. I think all these come from the same factory with different brand patches. I had them left over so I will stay with Kartek brand but I really like the Elrods Prostrap brand.
These 24” stretch to 24.25” static. My research says that they will stretch to 26” single and 25” dual. I set them up for 16” of travel plus 1.25” of dynamic stretch travel. So 17.25” of travel is my best guess.
24” quad wrap Kartek branded. I think all these come from the same factory with different brand patches. I had them left over so I will stay with Kartek brand but I really like the Elrods Prostrap brand.
These 24” stretch to 24.25” static. My research says that they will stretch to 26” single and 25” dual. I set them up for 16” of travel plus 1.25” of dynamic stretch travel. So 17.25” of travel is my best guess.
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WaterH
Well-known member
I would have thought one strap each corner is plenty. Do serious crawlers/wheelers break them much? Looks good though. The pilot in me likes redundant.
chaplinfj60
Well-known member
takes double shear to the next level.Limit straps are mounted in the rear.
24” quad wrap Kartek branded. I think all these come from the same factory with different brand patches. I had them left over so I will stay with Kartek brand but I really like the Elrods Prostrap brand.
These 24” stretch to 24.25” static. My research says that they will stretch to 26” single and 25” dual. I set them up at 25.5” which gives me 16” of travel plus 1.25” of dynamic stretch travel. So 17.25” of travel is my best guess.
i like it alot and actually given me an idea
HYDRODYNAMIC
Rock Stacker
Most of the buggies in tech at KOH had single per corner quad wrap straps.
Campbells and Scherer have dual straps per corner on the rear axle. They also have large and heavy trussed axles cycling the straps infinitely more than I will.
On trailing arms the rear axle has leverage on the shock so the axle can hammer away at the shock much harder if the strap is not working compared to an axle mounted shock.
Another thing to keep in mind is the stretch rate. Most vendors say 1” per foot and half that for duals.
That’s 2” for 24” straps. Thats 16” of travel instead of 18” that you will not see in the rocks as the dynamic loading will not be enough to stretch the strap. With duals the stretch is cut in half so you can get another inch of travel and have the same stopping point to protect the shocks.
Some might like the stretch as it will reduce the shock load when the straps limit out.
One would probably have been enough, but I did like the idea of more travel with less stretch. I also like that it creates spares if a strap got loose and cut up by driveline, tire, chassis, or WTF, there are spares.
I would really prefer that vendors would give out rate of stretch per lbs. similar to springs so you can calculate instead of rule of thumb.
Campbells and Scherer have dual straps per corner on the rear axle. They also have large and heavy trussed axles cycling the straps infinitely more than I will.
On trailing arms the rear axle has leverage on the shock so the axle can hammer away at the shock much harder if the strap is not working compared to an axle mounted shock.
Another thing to keep in mind is the stretch rate. Most vendors say 1” per foot and half that for duals.
That’s 2” for 24” straps. Thats 16” of travel instead of 18” that you will not see in the rocks as the dynamic loading will not be enough to stretch the strap. With duals the stretch is cut in half so you can get another inch of travel and have the same stopping point to protect the shocks.
Some might like the stretch as it will reduce the shock load when the straps limit out.
One would probably have been enough, but I did like the idea of more travel with less stretch. I also like that it creates spares if a strap got loose and cut up by driveline, tire, chassis, or WTF, there are spares.
I would really prefer that vendors would give out rate of stretch per lbs. similar to springs so you can calculate instead of rule of thumb.