door bars are worth every cent - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-10-2009, 06:17 PM   #81
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Originally Posted by bbundy View Post
Go Park your car on some flat ground takes the roof off or put the top down open both doors and look at it from the side.

Other than the sills, the trans tunnel, and the wimpy so called frame rails it already is a flat plate trough the center of the car. To make it stiffer it needs added section modulus in the vertical direction to reduce vertical bending and torsion. A flat plate structure on the bottom of the car dosnt give section modulus in the correct direction. Spindly tubes replicating the flat plate is harldy better. Door bars do ad a huge amount of vertical section modulus though not as much as a real roof or a cage would. Also Converting the Trans tunnel from an open hat section to a tubular section also would significantly change the section modulus in both vertical bending and especially torsion.

Mazda I think was pretty on track on the Mazdaspeed as seen in the pic but I still think it can be done better.

Bob
I think maybe we are talking about two different bending modes here.
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Old 12-10-2009, 06:31 PM   #82
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Re: MSM

When I added the butterfly to my 2000, I could swear it ended up stiffer than my friend's MSM.
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Old 12-10-2009, 06:32 PM   #83
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I know this is probably short-sight, since one's interests and tastes change over time, but does anyone else feel like they will keep their Miata forever? Mine is rust free with a straight body. Motors and parts are plentiful. I don't see any automakers building a similar car that would be within my budget. Within a few years it'll be virtually worthless, so there wouldn't be much point in selling it.
LOL. I go through this exact thought process whenever I consider spending more money on my miata.
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Old 12-10-2009, 06:33 PM   #84
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Car sure will be nice when I'm done though.
Done? What is this "done" you speak of?

Quote:
Originally Posted by mgeoffriau View Post
I know this is probably short-sight, since one's interests and tastes change over time, but does anyone else feel like they will keep their Miata forever? Mine is rust free with a straight body. Motors and parts are plentiful. I don't see any automakers building a similar car that would be within my budget. Within a few years it'll be virtually worthless, so there wouldn't be much point in selling it.
I've said the same thing. It's a simple car, a blast to drive and you can replace ANYTHING on it for $300 or less (other than some performance add-ons).
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Old 12-10-2009, 07:36 PM   #85
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Originally Posted by mgeoffriau View Post
I know this is probably short-sight, since one's interests and tastes change over time, but does anyone else feel like they will keep their Miata forever? Mine is rust free with a straight body. Motors and parts are plentiful. I don't see any automakers building a similar car that would be within my budget. Within a few years it'll be virtually worthless, so there wouldn't be much point in selling it.
I've had mine since 92. I dont think I have ever owned anything that I have used and enjoyed for such a long period of time. No plans on getting rid of it ever. It is a 1990 with 300k miles on it. obviously some parts have been replaced.

Bob
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Old 12-10-2009, 07:50 PM   #86
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Originally Posted by JasonC SBB View Post
Re: MSM

When I added the butterfly to my 2000, I could swear it ended up stiffer than my friend's MSM.
I wonder if that was because you added the frame rail reinforcements as well.

Frame rail reinforcement + soso making a tube out of the transmission tunnel > making a slightly better tube out of the transmission tunnel.

I don’t know for sure that is just my best guess.

Bob
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Old 12-10-2009, 08:13 PM   #87
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Yes, FM's butterfly requires that their frame rails are in place. I installed em all at once.

And yet the door bars made a more dramatic improvement.
I suspect though that with the door bars, removing the butterfly/frame rails would be very noticeable. IOW they both help.

BTW I posted months ago on m.net that an easy way to measue stiffness would be to look for the dominant resonant frequency in the chassis motion in the left-right direction in an accelerometer mounted on the rollbar. The higher, the stiffer. In my car it was 17 Hz IIRC, with all the bracing in place. I don't have any before/after numbers though.

P.S. Here it is
http://forum.miata.net/vb/showthread...=accelerometer
The 17 Hz resonance is by far the largest resonance in the car, and it is largest in the left/right axis on the rollbar. This agrees with the butt-o-meter in that the chassis shudder feels like the seatback and the steering wheel are vibrating left-right (I'll bet, in opposite directions, due to chassis twist).
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Old 12-10-2009, 08:20 PM   #88
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P.P.S. I wish there were a door design wherein when you close it, some kind of strong mechanism latches in and makes the door a load bearing member, to make it part of the structure. Would work great for convertibles.
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Old 12-10-2009, 08:49 PM   #89
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Originally Posted by mgeoffriau View Post
but does anyone else feel like they will keep their Miata forever?
I'll eventually move up to an NB, then an NC. So I should have a Miata for at least the next 20 years. That is unless I can afford something like a ZR1 or maybe an Exige at some point.
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Old 12-10-2009, 09:05 PM   #90
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Mazda I think was pretty on track on the Mazdaspeed as seen in the pic but I still think it can be done better.

Bob
Do tell--what would the better mousetrap look like?
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Old 12-10-2009, 09:39 PM   #91
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If mine doesn't get totaled or something catastrophic doesn't happen to it..im going to keep it as long as I live and I'm going to keep modding it..

1990 78k Original Miles, original paint, lots of Original stuff, 2nd owner..

Nomie
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Old 12-10-2009, 11:09 PM   #92
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Quote:
Originally Posted by mgeoffriau View Post
I know this is probably short-sight, since one's interests and tastes change over time, but does anyone else feel like they will keep their Miata forever? Mine is rust free with a straight body. Motors and parts are plentiful. I don't see any automakers building a similar car that would be within my budget. Within a few years it'll be virtually worthless, so there wouldn't be much point in selling it.
Before I pulled the trigger on my build, I thought about where I came from with the VW catastrophe, my need for a "newish" car, my NEED to go to the track, and about where I want to put my money monthly (and its not $600 per month for a Subie).

There's no substitute for my car...and track rubber is only $600 a pop.
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Old 12-10-2009, 11:52 PM   #93
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Quote:
Originally Posted by JasonC SBB View Post
P.P.S. I wish there were a door design wherein when you close it, some kind of strong mechanism latches in and makes the door a load bearing member, to make it part of the structure. Would work great for convertibles.
I've spent hours at night wondering this exact same thing.

I always end up thinking I'd be better off doing everything else first, or just putting in a real cage for the effort.
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Old 12-11-2009, 11:07 AM   #94
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Quote:
Originally Posted by JasonC SBB View Post
P.P.S. I wish there were a door design wherein when you close it, some kind of strong mechanism latches in and makes the door a load bearing member, to make it part of the structure. Would work great for convertibles.
I thought about this too. I'm not so sure you can do it in a way that would be user friendly, though. The best way to do it would probably be like a safe lock where you spin a gear to lock large bars into the front and rear of the door jam. I guess you could use a motor to do it and have some sort of gear lock, but it'd probably be loud and annoying to most people. Imagine having to wait for your door to unlock. And then what happens if it fails in an accident and you're stuck? Or just fails in general and you're stuck? Maybe a manual crank as well?
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Old 01-23-2010, 01:12 PM   #95
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If this thread has taught me one thing, it's that I need to sell the Butterfly sitting in my garage and pick up a pair of door bars...

Good stuff.
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Old 01-27-2010, 05:34 PM   #96
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Originally Posted by cueball1 View Post
Hard Dog bolt in bars right?

Great review and good to know it makes a difference. Boss Frog slams them so much I was waffling. Got a set coming for the holidays now.

In what way do they slam them? on installation or just function? because they seem to be in the game now:

Miata Performance





http://www.bossfrog.biz/pdf/BF.DoorB...tions.0912.pdf
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Old 01-27-2010, 05:44 PM   #97
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I'm no engineer so I can't comment on their functionality, but aesthetically they look utter garbage.

I had door bars with my old Carbing cage, I miss them, (but not the loss in legroom!)
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Old 01-27-2010, 05:54 PM   #98
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What size tubing is that? Looks small. To me, that design looks like it will crumble on side impact.
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Old 01-27-2010, 05:58 PM   #99
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Seems like I recall BF slamming door bars unequivocally...until they introduced their own, then suddenly they were only slamming the other designs. The page explains their use of 1" tubing and sheetmetal instead of larger tubing.

It's ugly, but I could live with ugly if it was a truly superior design. They just lost some credibility with me when they changed their story about door bars (especially when consumer reviews of other doorbars are almost universally positive, even more so than roll bars, frame rails, butterflies, etc).
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Old 01-27-2010, 07:50 PM   #100
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Without looking at their page, their design could be stiffer for the same weight or the same weight for the same stiffness. The plates would increase beding stiffness considerably in the plane of the plates (vertically as installed). Also it can be narrower with the smaller diameter tubing.

Nice idea from a purely mechanical standpoint but I do not like the look at all especially with the lettering cutouts. I still prefer the ones I have.

OK read the description..
Quote:
Traditional single-tube door bars with two mounting points do little to stiffen the frame

Clearly that is not true. Marketing-speak.
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