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 Post subject: Re: Potentia v8
PostPosted: February 27, 2021, 8:24 pm 
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Miatav8,MstrASE,A&P,F wrote:
Interesting build! I hear you on the bar fitment. I’m in the process of fitting bars to a D100 right now. Wouldn’t it be great if there were published dims for oem bars?

Is that a hollow bar? Taper stud end links?


Its a Solid bar, endlinks are not tapered. Will the bar be ineffective the way I've mounted it? You've drawn in with the mount points in their correct position further out, I was wondering if that U shaped bend between the 2 mounts is critical to its ability to be a spring. If the current mount isn't a problem then why mount it low?

Bent Wrench wrote:
How about lowering the rear section of the body so the mid body line is lined up and then chop the top of the forward section to match?
Not sure I follow, chopping the top is something I want to avoid as I'd like a stock windshield/seals, the window line will be different rear of the Vent windows. Spent a while making some scale images of what the body might be so maybe it's been fixed in there?
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 Post subject: Re: Potentia v8
PostPosted: February 28, 2021, 8:26 am 
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Thanks for asking why. You know the bar will be effective. I didn’t say it would not add roll resistance (ineffective). I assume you are interested in maximizing the effectiveness (though maximum effectiveness may be too much for tuning purposes).

A line drawn through the pivot centers of the saddle and endlink should be level for the bar stiffness to increase with the degree of roll and minimize movement and angular changes in/through the endlinks for wear and loading of the control arm. It appears the endlink cl is higher than the saddle cl for coilover clearance. It also appears the bar can hit the coilover in droop. I/m guessing that is why you polished the bar arms. Again, it may just appear that way.

The bar effective rate is reduced significantly due to the arm length increase and deflection in the zigzag arm. Let’s assume a 23mm (.90”) solid bar with 12 inch arms and 34 inches between the arms as installed on an odyssey for a 148 lb rate. By moving the saddles inboard, the arms are increased to 15 inches and the effective width is somewhere between the new and original saddle position (32”?) reducing the rate to about 100 lb, not counting the reduction for arm deflection in bending near the saddle where it originally was only twisting.

By lowering the bar, you reduce the cg height but add bracket weight partially offset by shorter endlinks.

For the sake of general discussion, arm length and bar od have a much greater effect on rate than bar length at the saddles. It interesting that so many bars these days have large drops/arm/offset between the saddles, since this would load the bar in a form of shear and bending rather than torsion but I’ve not fully considered what effect the inner arm length has on effective rate. I doubt there is a simple rate calculator for that currently.

I think you’ve done a great job in finding a way to get an oem bar to fit considering all the completed work in the way. “Painted into a corner” at this stage if you know what I mean. Understandably, most don't give any consideration for a bar during initial construction.

For others who might want add a bar like this, what is the eye to eye width and saddle width (between green marks)?

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 Post subject: Re: Potentia v8
PostPosted: February 28, 2021, 1:50 pm 
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Miatav8,MstrASE,A&P,F wrote:
Thanks for asking why. You know the bar will be effective. I didn’t say it would not add roll resistance (ineffective). I assume you are interested in maximizing the effectiveness (though maximum effectiveness may be too much for tuning purposes).

A line drawn through the pivot centers of the saddle and endlink should be level for the bar stiffness to increase with the degree of roll and minimize movement and angular changes in/through the endlinks for wear and loading of the control arm. It appears the endlink cl is higher than the saddle cl for coilover clearance. It also appears the bar can hit the coilover in droop. I/m guessing that is why you polished the bar arms. Again, it may just appear that way.

The bar effective rate is reduced significantly due to the arm length increase and deflection in the zigzag arm. Let’s assume a 23mm (.90”) solid bar with 12 inch arms and 34 inches between the arms as installed on an odyssey for a 148 lb rate. By moving the saddles inboard, the arms are increased to 15 inches and the effective width is somewhere between the new and original saddle position (32”?) reducing the rate to about 100 lb, not counting the reduction for arm deflection in bending near the saddle where it originally was only twisting.

By lowering the bar, you reduce the cg height but add bracket weight partially offset by shorter endlinks.

For the sake of general discussion, arm length and bar od have a much greater effect on rate than bar length at the saddles. It interesting that so many bars these days have large drops/arm/offset between the saddles, since this would load the bar in a form of shear and bending rather than torsion but I’ve not fully considered what effect the inner arm length has on effective rate. I doubt there is a simple rate calculator for that currently.

I think you’ve done a great job in finding a way to get an oem bar to fit considering all the completed work in the way. “Painted into a corner” at this stage if you know what I mean. Understandably, most don't give any consideration for a bar during initial construction.

For others who might want add a bar like this, what is the eye to eye width and saddle width (between green marks)?

I appreciate the in depth response.

This Sway bar from an 04-era Odyssey has been modified, the polished area is where I've cut and rewelded. The welds were ground down for clearance at the coilover but as you said there needs to be a sleeve, In my haste the endlinks were cut a tad short. For any sway bar changes I'm trying to keep cuts and welds in that area (where theres minimal bending).

The sway bar does deflect a bit with the current mounts, moving the mount up will bring the lever arm level(or closer to it) with the endlink. Space is at a premium around suspension components, it looks more open then it really is in pictures. The mounts could move out up top which will remain poor for COG but a worthwhile sacrifice for accessibility.

The sway bar was definitely an add on to the design, after deciding to go with a steel skin and closed wheel body its clear that this will be hefty by Locost standards. The Honda sway bar was chosen primarily because it was available, there aught to be better choices out there. If only there was a database of technical blueprints for autoparts.

The bar drop in between saddles is an interesting question, perhaps that yield helps smooth shock between the wheels for sharp impacts?
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 Post subject: Re: Potentia v8
PostPosted: March 1, 2021, 9:57 am 
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Thanks for sharing that. My guess is oems are looking to shave cost and material. It is cheaper to snake a light tube through that meets the rate needed rather than add thicker metal to extend saddles out to where the bar can be straight. I doubt they actually use 4140. My wife has a survivor 93 mazda 323 bubble back that I fit much larger ZX2 swaybars. Tried local yards but they refused to sell sway bars since they are often bent from accident damage. I did find bars online and they were a little bent but that was remedied in a pipe bender without much force. The rear did not fully fit my application, but I was able to shorten the arms an inch to align properly with existing IRS holes by flattening a little more of the arm in a press then drilling new holes.

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 Post subject: Re: Potentia v8
PostPosted: March 3, 2021, 8:48 am 
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Location: 4AGE in S.E. Michigan
Stab bars " I doubt they actually use 4140"
Probably close to 90% of all OEM solid stab bars are just commercial grade 1020. They induction heat the bend and formed area(s) for about 20 sec, then shape the bar in a hydraulic operated fixture and flat-in the ends plus perf the attachment holes all in one operation.
Davew


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 Post subject: Re: Potentia v8
PostPosted: March 3, 2021, 10:05 am 
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davew wrote:
Stab bars " I doubt they actually use 4140"
Probably close to 90% of all OEM solid stab bars are just commercial grade 1020. They induction heat the bend and formed area(s) for about 20 sec, then shape the bar in a hydraulic operated fixture and flat-in the ends plus perf the attachment holes all in one operation.
Davew


I was hoping that was the case. Thanks for the confirmation. I guess as long as we don’t allow so much twist that it doesn’t return through limited motion ratio, maximize bar width to spread the load and sufficient bar thickness to resist, we could fab the whole thing without special expensive processes or alloys.

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 Post subject: Re: Potentia v8
PostPosted: March 5, 2021, 10:55 pm 
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The sc400 fuel hanger was designed in a fuel tank with a seperate access panel, so instead I bought a EK Civic pump assembly and married the two. The level sender is just some generic unit that has the ohm specs needed to run with the Knock-off Smiths gauges.
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The mount plates were a pain to make as the mounting holes were not spaced evenly, in hindsight I should’ve used thicker steel too. 18ga was used on the fuel tank throughout but 16ga would've been easier to work with.
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The internal baffles didn't change much besides a couple additions around the pump. I filled it with water and was happy with how the baffles were working.
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The mount plates were welded all the way round on the inside, the plan was to weld the outside too but the heat distortion threw the entire panel way out of whack. It took a few hours with a torch and Mallet to bring it back to flat-ish. As you can see there's still lots of distortion but it's going to be covered in sound deadning and under a false floor anyways. What I should've done was strengthen the panel prior to welding, a few bead rolls combined with some horizontal bracing would've gone a long way.
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Used POR15's tank sealer to deal with any pinholes and inhibit rust. After that its primer and seamsealer (closer to butyl tape then rubber) around all the edges, the idea being to mitigate spillage if a crack forms during an accident. Also fiddled with the roof placement to get it as low and forward as possible.
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Started work on the roll bar mounts and trunk frame, the fuel tank will have 2"x1/8" straps. Good isolator pads seemed impossible to find so Big rig mudflaps are going to be used as the interface between all the parts.
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Not sure if a bar linking the horizontal rail down to the panhard area will be necessary, its going to get a steel panel regardless.


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 Post subject: Re: Potentia v8
PostPosted: March 6, 2021, 9:52 am 
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Nice tank! Mig welds are tough to make air/liquid tight imho. You could also have made lap flanges, stitch welded, then fluxed and soldered with a hand torch (like copper/brass radiators and older factory fuel tanks) before sealing the inside. The heat required is not enough to warp.

I agree, thicker is better when having to weld sheetmetal. For cosmetic sheet metal, I’ve tried heat and hammer smoothing of mig welds but they just crack as wells as the warping from the torch so I end up just lapping spots and grinding. Tedious! A nut welded inside the bottom to accept an oil pan drain plug for a tank drain is nice to have too. Hard not to use the chinese aluminum tanks that are so cheap but the foam is junk and no baffles.

I like the marine tubular tank floats since they are about $20, are stainless so they deal with ethanol water absorption well, and come in a couple different resistance values to work with universal gauges.

Commercial poly truck flaps are cheap and durable. I bought Ryder flaps I use for pedal pads, countersinking for pop rivets, dimpled side out. Also makes a good battery tray, fixed pad with screws or rivets for stepping into the car, but the poly is too rigid for rad duct sealing strips or tank supports.

I don’t see much benefit to adding a longitudinal tube along the bottom rear unless you add a bolt on tie below the axle between the front and rear. Could be two drill and weld in crush sleeves for 3/8 bolts on each end or flanges. Rear impacts are likely to be much higher but you never know.

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 Post subject: Re: Potentia v8
PostPosted: March 7, 2021, 12:16 am 
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Miatav8,MstrASE,A&P,F wrote:
Commercial poly truck flaps are cheap and durable. I bought Ryder flaps I use for pedal pads, countersinking for pop rivets, dimpled side out. Also makes a good battery tray, fixed pad with screws or rivets for stepping into the car, but the poly is too rigid for rad duct sealing strips or tank supports.

I don’t see much benefit to adding a longitudinal tube along the bottom rear unless you add a bolt on tie below the axle between the front and rear. Could be two drill and weld in crush sleeves for 3/8 bolts on each end or flanges. Rear impacts are likely to be much higher but you never know.


Looks like I've answered my own question, the lower beam is necessary as that's the area where the roll bars rear supports will land. While that area will buckle in an accident, less will be better to keep from turning the whole thing into a mouse trap.

On your advice, Found a set of generic fuel tank pads for the straps.


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 Post subject: Re: Potentia v8
PostPosted: March 7, 2021, 9:50 am 
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I think the straps you have are fine. Infact, I’ve made similar tank mounts but used left over aircraft cowl baffle strips (not because it is better in any way). I was just rambling about the many uses of cost effective mud flaps. Westfield has used aluminum tank straps with adhesive backed open cell foam like you’d buy at home depot.

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 Post subject: Re: Potentia v8
PostPosted: March 18, 2021, 7:45 pm 
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Finally figured a 3rd mount for the steering rack. It's not finished as the there will be a bit of Reinforcement along with dowels for the bolts.
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The e36 radiator is a challenge having mounts partway up rather then on the bottom, and being fairly wide at 22". The idea is to have a support strong enough to allow for a forward tow point in the grille.. (not pictured is a tow hook structure that juts another 1.5ft past the radiator on the RH side, the triangulation top to bottom is designed with that in mind)
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Now is a very bad time to be building a Locost, this was today's prices at $2.50 per foot for 1" 16ga tube!
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And an idea for how the front and rear may look.
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 Post subject: Re: Potentia v8
PostPosted: March 19, 2021, 7:57 am 
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The drawings remind me of a Triumph GT6 ( I have a spitfire project).

I’ve been dreading a trip to the steel supplier. I was considering making support columns to replace concrete piers under my house and restocking common tube and strip I use the most.

On the rack mount, very clever! You may want to add a pipe sleeve for a positive stop when tightening the mount or prevailing torque nuts or jamb nuts.

No need for all the extra metal around the radiator or rubber isolators between the rad and brkt. Use the structural flanges on the top and bottom. Cut steel tubes or bend C-flanges to fit inside the rad flanges and drill for through bolts. This allows the extra clearance needed for head/washer/nut to be outside the flanges. ¼ or 5/16 by 3 inch bolts is probably what you need. Make the top mount separate from the bottom or one side mount for each side that bolts together for removing the brkt.

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 Post subject: Re: Potentia v8
PostPosted: March 19, 2021, 1:47 pm 
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Nice rack...er...rack mount :oops:

Any provision for bump steer adjustment?

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 Post subject: Re: Potentia v8
PostPosted: March 19, 2021, 3:28 pm 
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On the rad mounting, here are examples of what I did with bent flanges on a 5.0l ranger and tube to adapt the stock miata brkts to a speedway rad, both circa 2000ish so I think I've improved since then but the basic idea.

viewtopic.php?f=35&t=8208&p=252168&hilit=miata+flange#p252168

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 Post subject: Re: Potentia v8
PostPosted: March 19, 2021, 5:55 pm 
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seattletom wrote:
Nice rack...er...rack mount :oops:

Any provision for bump steer adjustment?

Swapping the outer tie rods to heim joints would allow for shimming. In the early stages I measured a few things wrong and so my steering rack is a bit narrow, I've saved a second sc400 rack to modify if this one has issues.
Miatav8,MstrASE,A&P,F wrote:
On the rad mounting, here are examples of what I did with bent flanges on a 5.0l ranger and tube to adapt the stock miata brkts to a speedway rad, both circa 2000ish so I think I've improved since then but the basic idea.

https://www.locostusa.com/forums/viewto ... ge#p252168
The current mount is something I'm not happy about. With this being a road car I feel the rubber isolators may be important so gears are turning on a better solution, it should be simple enough to build mounts into the planned lattice and bypass the angle iron monstrosity.


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