12:05 Garage- ’70 Duster build
- Thread starter racerjoe
- Start date
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racerjoe
Well-Known Member
Well here it is. I ended up making the arms with 2.5" x 3/8" flat bar instead of drawing something to be cut by send cut send. I wasn't confident enough in what was in my head, so I decided to do it the old fashioned way.
I'm slightly concerned about the bracket on the LCA, but I'll just let it ride and monitor it for stress cracks or twisting.
This is just a cap that holds the spline coupling in place. I haven't oxygen acetylene brazed in a while so I decided to have at it on this piece.
I have to admit, I was struggling with the idea of this piece of 1.5" x .188 wall tubing twisting enough. I had fears of it being so stiff if I jacked up one side the wheel wouldn't have any travel. I should have put those thoughts out my mind and trusted the math. The suspension moves just fine. I went for a short ride and it is marginally stiffer just driving down the road. I'd imagine most passengers wouldn't even notice. I found a 2 lane road and did an imaginary slalom, it's definitely much flatter. I didn't get super aggressive because I wanted to keep it between the ditches.
We do have autocross this weekend, but it's Mardi Gras season and we're going to the parades. I'll have to wait until next month to see how it does around the cones.
I'm slightly concerned about the bracket on the LCA, but I'll just let it ride and monitor it for stress cracks or twisting.
This is just a cap that holds the spline coupling in place. I haven't oxygen acetylene brazed in a while so I decided to have at it on this piece.
I have to admit, I was struggling with the idea of this piece of 1.5" x .188 wall tubing twisting enough. I had fears of it being so stiff if I jacked up one side the wheel wouldn't have any travel. I should have put those thoughts out my mind and trusted the math. The suspension moves just fine. I went for a short ride and it is marginally stiffer just driving down the road. I'd imagine most passengers wouldn't even notice. I found a 2 lane road and did an imaginary slalom, it's definitely much flatter. I didn't get super aggressive because I wanted to keep it between the ditches.
We do have autocross this weekend, but it's Mardi Gras season and we're going to the parades. I'll have to wait until next month to see how it does around the cones.
DionR
Well-Known Member
I like it! BTW, I don't think SendCutSend can bend 3/8" plate. If you had planned to have them bend it for you.
I assume the calculations take into account the length of the arm?
What size was the original sway bar? Could just be the angle, but looks dinky and with a fairly long arm to boot.
racerjoe
Well-Known Member
I would have had them cut only, but added a slice about 1/8-3/16" all the across leaving 1/4" on each side so I could have a reference to bend. Then just weld the slice up. Go back and look at the saddles for the tube. That was the same idea. On these, I cut about halfway through the flat bar, then heated it, bent it, then welded. It makes for a clean bend and right where I want it. Also, I'm bending steel in a bench vice, I don't have a press brake.
Since I have nearly the same wheel rate as I used to with the torsion bars, I used the Hotchkis sway bar as a place to start. Using this calculator --> Sway Bar Rate Calculator - Addco I was able to determine the rate of the Hotchkis bar. Then I worked backwards using common tubing diameter and thicknesses. I ended up with the same diameter and thickness as the Hotchkis bar. It is currently setup in the hole that is damn near the same rate as the Hotchkis bar (746lb/in) and I have a hole 3/4" in both directions. This equates to almost 100lb/in more on the short side and about 80lb/in less on the looser side.
The bar Denny supplies is a 1" solid. The spring rate on it is around 250lb/in. So this is a substantial change. Remember, Denny didn't design his kit to be full on pro touring, road race setup. He has offered to make me a bar, but I wanted to try this.
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bjkadron
Well-Known Member
Fantastic! I have to say I'm almost definitely going to do something similar on mine. Thanks for finding those PTO shafts!
I think you are on the right track with the stiffness based on riding in/watching/looking at action shots of your car. Now you just need to go drive in a big circle and see which hole you need to use for neutral breakaway!
I think you are on the right track with the stiffness based on riding in/watching/looking at action shots of your car. Now you just need to go drive in a big circle and see which hole you need to use for neutral breakaway!
racerjoe
Well-Known Member
I definitely need to be educated on this circle business you speak of. Also, I was thinking if I need more finite adjustment, I could move one side only. Is that a thing or just dumb? Although I’m probably not a good enough driver to be able to recognize a change that small.Fantastic! I have to say I'm almost definitely going to do something similar on mine. Thanks for finding those PTO shafts!
I think you are on the right track with the stiffness based on riding in/watching/looking at action shots of your car. Now you just need to go drive in a big circle and see which hole you need to use for neutral breakaway!
DionR
Well-Known Member
I thought about using the same idea on the crossmember parts that needs bends on my project. But after looking at the extra effort of locating the slots and adding 1.5' of weld I figured I would let them do it for me and see. It added like $12 to the bottom flange on the upper crossmember and I figured that was a decent ROI, but didn't look at how much it added to the bottom crossmember part. The mount I would get bent either way. Now, if they show up and don't fit up, I might change my tune some. Add that the bending added a day or more to the process, too.
Got notice that they shipped today but too early for an estimated delivery date.
bjkadron
Well-Known Member
Roll stiffness not only controls the amount of lean of the car, but if you look at the ratio of the f/r roll stiffness (roll couple) then it also serves as the easiest way to adjust the steady state breakaway characteristics of the vehicle. ie: over/under-steer during the middle of the corner.
The easiest way to test this is a skidpad test (or driving in a circle) and slowly increasing speed until one end starts to break away. If the rear goes first then lower rear stiffness or increase front stiffness. If the front goes first then Lower Front stiffness or increase rear stiffness. Repeat until you evenly slide out as you approach the grip limit of the corner radius.
Yes, you can offset different sides because the total twisting force is what is acting in either direction. I believe it would be the equivalent of moving both sides half as much but I'd have to calculate that. If you want to get really into the weeds here is a great thread that Whiteline contributed to: https://forums.nasioc.com/forums/showthread.php?t=218971
racerjoe
Well-Known Member
I'm wearing out that Addco calculator- good thing I don't have to pay for it!
I did some calculations for the other two setpoints. Both the center to forward and center to rearward either adds or subtracts about 40-45lb/in. I'm not sure I'll be able to tune something that finite. My rear Hotchkis bar also has 3 holes, currently setup on the middle. I used to run full tight with the smaller wheel/tire package, but loosened it with the current setup. I like having all this adjustability! Now I need to find a big parking lot for circles.
bjkadron
Well-Known Member
Yeah, when you add in the adjustments on your rear bar I don't think you will need more then the even sets to get there. it's at least 9 combos of Roll couple.
Honestly finding the parking lot where you won't get yelled at is usually the hardest part.
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racerjoe
Well-Known Member
And one without parking blocks and light poles. We have a movie theatre that just closed nearby. I think their back parking lot will work. I'll have to do a drive by to check it out.
bjkadron
Well-Known Member
Yeah, If you have a couple cones you may want to throw them out so you can keep a consistent radius.
racerjoe
Well-Known Member
It's getting enough miles on it, that's for sure. I missed autocross this past weekend because Mardi Gras. The cruise around the lake is next weekend. I hope to make it if my schedule and weather allows. It's about 135-150 miles depending on the route.Looking good brutha! SO, how's that trash pile?
No no no.. I wouldn't call your car a trash pile. I figure you probably have a pile of goodies tossed off to side that would be pure gold to a guy like... Umm me
racerjoe
Well-Known Member
Hahahaha! I guess I'm numb to sarcasm and just assumed that's what you meant. I've actually been selling stuff off.
racerjoe
Well-Known Member
That's actually been on there for a while. That picture was 2023 Moparty.
DionR
Well-Known Member
racerjoe
Well-Known Member
There wasn't even a G3 in it at that time! Lol! Guess what, I still don't have a single Holley branded part on it.And not a single Holley swap part used in the G3 swap.
I think you should be comped
bjkadron
Well-Known Member
It is interesting they used it for the 73-76 duster page... Haha
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Chevy guys... am I right?
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