X-bar Project
Aug 13, 2012, 11:17 AM
#1
X-bar Project
So Im starting work on designing an X-bar for the rear strut towers on our car. Ive been playing around with the idea for a while now and I decided to finally invest in it and go for it.
My brother is a welder and metal worker so Im having him make some brackets to go onto the top of the struts and Im going to build from there up. So as soon as I get those in I'll post some pictures.
In the mean time I wanted to see if anyone had any thoughts on the project. Such as mounting points for the top of the "X". Or if the bars should connect in the middle or be separate from each other. Or whatever else you all can think of. Any input will be highly welcomed!
Thanks!
My brother is a welder and metal worker so Im having him make some brackets to go onto the top of the struts and Im going to build from there up. So as soon as I get those in I'll post some pictures.
In the mean time I wanted to see if anyone had any thoughts on the project. Such as mounting points for the top of the "X". Or if the bars should connect in the middle or be separate from each other. Or whatever else you all can think of. Any input will be highly welcomed!
Thanks!
Aug 14, 2012, 01:15 PM
#4
Thats actually really awesome keith. Ive seen bar setups similar to that for the Evos while studying different brace designs.
@zak yea I agree. Thats sorta what I am trying to achieve. I'd like to have a set of subs in my trunk too someday. So a setup like that would be in the way. Plus I actually have to use my trunk sometimes lol.
So. My original plan was to design something like this setup for an WRX.
And while this looks cheap and like it would maybe get the job done I noticed that it wasnt connected to the strut points and it wouldnt help againt any type of flex other than outward flex.
Now I dont want to do a traditional "strut bar" (putting metal connecting the two struts) because the trunk floor of the RA is already designed to take that sort of pressure as the floor and the mounting points of the struts are almost inline if not dead on.
Therefore I want to combine these two ideas and make a setup that connects four points in a vertical manner to tie the entire rear end together. Then You'll still have quite a bit of trunk/sub room. LOL I'll update as soon as the mounts for the top of the struts are finished.
In the mean time here are some pictures Ive been gawking at for inspiration.
@zak yea I agree. Thats sorta what I am trying to achieve. I'd like to have a set of subs in my trunk too someday. So a setup like that would be in the way. Plus I actually have to use my trunk sometimes lol.
So. My original plan was to design something like this setup for an WRX.
And while this looks cheap and like it would maybe get the job done I noticed that it wasnt connected to the strut points and it wouldnt help againt any type of flex other than outward flex.
Now I dont want to do a traditional "strut bar" (putting metal connecting the two struts) because the trunk floor of the RA is already designed to take that sort of pressure as the floor and the mounting points of the struts are almost inline if not dead on.
Therefore I want to combine these two ideas and make a setup that connects four points in a vertical manner to tie the entire rear end together. Then You'll still have quite a bit of trunk/sub room. LOL I'll update as soon as the mounts for the top of the struts are finished.
In the mean time here are some pictures Ive been gawking at for inspiration.
Aug 15, 2012, 05:06 AM
#5
Sounds promising ,but tell your brother I get on it 
A lot of the Wrx guys like the "cheap" one but it does have a function so it's not worthless at least. I have looked into this as well but more focused on something that might fit our car, than custom making it.
Keep us posted !!!
A lot of the Wrx guys like the "cheap" one but it does have a function so it's not worthless at least. I have looked into this as well but more focused on something that might fit our car, than custom making it.
Keep us posted !!!
Aug 15, 2012, 02:30 PM
#6
So I did some more studying of possible mounting points for the top of the X and I almost thought I had a better/simpler solution with an A shaped brace. Because the points where I would like to mount the top of the X are taken up by the roll for the seat belts... But I still fount some possible mounting points (see image below).
And to back me up on my X vs A brace type I talked to a girl I know who has her bachelor's in Math and is currently almost done with her bachelor's in Mechanical Engineering. I explained to her how it all worked and the forces that would be applied to the bar and showed her the possible mounting points. Her answer: Stick with the X bar and make sure it has a strong weld in the center of the X.
Works for me.
Current Plan
And to back me up on my X vs A brace type I talked to a girl I know who has her bachelor's in Math and is currently almost done with her bachelor's in Mechanical Engineering. I explained to her how it all worked and the forces that would be applied to the bar and showed her the possible mounting points. Her answer: Stick with the X bar and make sure it has a strong weld in the center of the X.
Works for me.
Current Plan
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Aug 15, 2012, 08:08 PM
#9
When we were discussing this in another thread (last year?) I stripped my trunk to have a look and was trying to visualize how our car's steel chassis was flexing in that back area due to hard bumps and high-g racetrack cornering inputs. Couldn't do it in my head. Therefore I couldn't design a brace that I knew would be effective. Must know how the body reacts to input loads before I can design a brace to add stiffness, i.e. position/orient the bars correctly to counteract chassis flexing.
I studied pictures of what the engineers at other car companies did (Sentra Spec-V for example), and there is a huge range of designs. However, none of the chassis I looked at were designed like the Mitsu. Others had the top of the rear shocks sticking way up in the trunk, they had much less metal bracing behind the rear seat than us, and so on. You can even see this if you compare pics that Bakuro has shown. So in the end, I still didn't know what the best rear brace design for our chassis might be - or even if we needed one!
Crans, here it doesn't matter if the bars are uneven length. You are right though, to stop bending and racking, triangles rule and its best if the brace is angled at 45 degrees to the chassis.
Bakuro, your effort is much appreciated, go for it and keep us posted!
Two comments from the peanut gallery here on your proposed design, if you don't mind
1. bolted joints loaded like yours will be less efficient than welded connections, so make sure the brace ends are bolted really well to the car body.
2. it might be better to attach the tops of the brace to the top or corner of the rear deck (where the speakers sit), instead of pushing on the side of the car near the fenders.
I studied pictures of what the engineers at other car companies did (Sentra Spec-V for example), and there is a huge range of designs. However, none of the chassis I looked at were designed like the Mitsu. Others had the top of the rear shocks sticking way up in the trunk, they had much less metal bracing behind the rear seat than us, and so on. You can even see this if you compare pics that Bakuro has shown. So in the end, I still didn't know what the best rear brace design for our chassis might be - or even if we needed one!
Crans, here it doesn't matter if the bars are uneven length. You are right though, to stop bending and racking, triangles rule and its best if the brace is angled at 45 degrees to the chassis.
Bakuro, your effort is much appreciated, go for it and keep us posted!
Two comments from the peanut gallery here on your proposed design, if you don't mind
1. bolted joints loaded like yours will be less efficient than welded connections, so make sure the brace ends are bolted really well to the car body.
2. it might be better to attach the tops of the brace to the top or corner of the rear deck (where the speakers sit), instead of pushing on the side of the car near the fenders.
Aug 16, 2012, 12:13 PM
#10
When we were discussing this in another thread (last year?) I stripped my trunk to have a look and was trying to visualize how our car's steel chassis was flexing in that back area due to hard bumps and high-g racetrack cornering inputs. Couldn't do it in my head. Therefore I couldn't design a brace that I knew would be effective. Must know how the body reacts to input loads before I can design a brace to add stiffness, i.e. position/orient the bars correctly to counteract chassis flexing.
I studied pictures of what the engineers at other car companies did (Sentra Spec-V for example), and there is a huge range of designs. However, none of the chassis I looked at were designed like the Mitsu. Others had the top of the rear shocks sticking way up in the trunk, they had much less metal bracing behind the rear seat than us, and so on. You can even see this if you compare pics that Bakuro has shown. So in the end, I still didn't know what the best rear brace design for our chassis might be - or even if we needed one!
Crans, here it doesn't matter if the bars are uneven length. You are right though, to stop bending and racking, triangles rule and its best if the brace is angled at 45 degrees to the chassis.
Bakuro, your effort is much appreciated, go for it and keep us posted!
Two comments from the peanut gallery here on your proposed design, if you don't mind
1. bolted joints loaded like yours will be less efficient than welded connections, so make sure the brace ends are bolted really well to the car body.
2. it might be better to attach the tops of the brace to the top or corner of the rear deck (where the speakers sit), instead of pushing on the side of the car near the fenders.
I studied pictures of what the engineers at other car companies did (Sentra Spec-V for example), and there is a huge range of designs. However, none of the chassis I looked at were designed like the Mitsu. Others had the top of the rear shocks sticking way up in the trunk, they had much less metal bracing behind the rear seat than us, and so on. You can even see this if you compare pics that Bakuro has shown. So in the end, I still didn't know what the best rear brace design for our chassis might be - or even if we needed one!
Crans, here it doesn't matter if the bars are uneven length. You are right though, to stop bending and racking, triangles rule and its best if the brace is angled at 45 degrees to the chassis.
Bakuro, your effort is much appreciated, go for it and keep us posted!
Two comments from the peanut gallery here on your proposed design, if you don't mind
1. bolted joints loaded like yours will be less efficient than welded connections, so make sure the brace ends are bolted really well to the car body.
2. it might be better to attach the tops of the brace to the top or corner of the rear deck (where the speakers sit), instead of pushing on the side of the car near the fenders.
To answer your questions:
1) bolted joints can create less efficient "weak points" in the brace. However something that Ive seen a lot of people run into with braces like the RRM one that are a solid welded piece is getting the alignment just right to attach them. This happened in my friends 3g Eclipse. Using a jack and some redneck ingenuity we got it on but it was way more complicated then simply bolting it on. So Im thinking that bolted attachments will not only make a simpler install but also give you more room to adjust the stiffness if you wanted to make that sort of modification. Another example of this is with sway bars. The Whiteline that I, Crans, and a few others have (couldnt think of anyone off the top of my head sorry lol) is one solid piece. However for more track ready/ racing variations Whiteline provided adjustable bars with several mounting points so the user can alter the stiffness of the bar.
2) I entirely agree with this. It would be better if I could mount the top of the X in a higher position but a few things get in the way of that and have stopped me from pursuing those methods. First off things get in the way. The speakers, the seat belt packs, the bars that move when you open/close the trunk. And while if this was a track car Id have no problem with removing any of those things my car still has to accomodate rear seat passengers, and my love of loud music (lol
) And mouting any higher than that would become more akin the the "A" shape I had imagined before which would have had a bracket on the underside of the bolt for the center child seat anchor. However I would trust the current mounting points that have several welds holding it together in several places and less leverage to bend than the center of the thin long piece that makes up the rear shelf.Other than that I have been wondering if there would be any benefit of a more forward slanted bar that would anchor at the back of the passenger seats. If you see the picture I posted with the red lines there is a big hole on each side of the small wall between the back seats and the trunk. Right above those holes are two much smaller holes. Anyone think that would make a better mounting point than the points I had previously chosen? I keep going back and forth on which would be better, but I think Im still leaning toward my initial positions.
Aug 27, 2012, 11:46 AM
#15
Sorry for the lack of updates Ive had trouble finding time to get on here lately. So here is the update.
The lower brackets turned out great! See pics below.
And I am now contemplating how best to design the "X". In the last picture you can see the bolts I test fitted for now. Im not sure If i'll go with one solid bar or a couple of bars with opposite threads on each end so that you can install then tighten to my liking. Im also contemplating the design of the upper brackets. Either the spot right over the struts where the red lines lead to which Im thinking would look like more of a metal clasp. Or the holes where the blue lines lead which would lean the bar forward more. But I think a bracket may be more easily made.
Thoughts?
The lower brackets turned out great! See pics below.
And I am now contemplating how best to design the "X". In the last picture you can see the bolts I test fitted for now. Im not sure If i'll go with one solid bar or a couple of bars with opposite threads on each end so that you can install then tighten to my liking. Im also contemplating the design of the upper brackets. Either the spot right over the struts where the red lines lead to which Im thinking would look like more of a metal clasp. Or the holes where the blue lines lead which would lean the bar forward more. But I think a bracket may be more easily made.
Thoughts?