zero
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Posts posted by zero
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I'm pretty sure in most of the TC rod failures I have heard of, the driver experienced a STRONG geometry change under braking. All of the accounts indicated the car pulled HARD in the direction of the failure, implying the wheel was moving rearward in the car. This seems to mean there must be some significant rearward force on the suspension when braking.
Frankly, assuming the strut doesn't break, there is really only so much geometry change that can happen from a torque effect. Also, we know that TC rods don't like bending loads and really aren't the right shape to resist them so it can't be contributing much to the torque resistance anyway. Yet, there is still the braking force/geometry change correlation. The TC rod/bucket/frame rail absolutely feel a significant compressive force under braking.
I haven't experience a rod failure myself, but I have experienced a TC bucket failure, and the car pulled in a similar manner.
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Well, the way I'm thinking of it is that the caliper is trying to rotate forward and is resisted in the way you describe.
But I think the wheel is also trying to move rearward. I'm not thinking it's the same as hitting a curb, but there is a component of force that is similar to a tire hitting a curb
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Braking force is only torque. Just like acceleration loads are only torque. Those loads are transferred to or from the chassis via the suspension links. And ALL of the weight of the sprung mass of the vehicle is supported by the springs. How could it be otherwise?
Correct me if I'm thinking about this wrong but here's my take on what 30 ounce means.
There certainly is quite a bit of torque applied to the suspension when you brake, but that isn't all of the force being applied to the suspension.
I think of it as a pulley, you have two torques being applied, at the tire and at the rotor/suspension, but in order for those torques to be applied, the wheel has to remain in the same place relative to the forces. What 30oz is thinking, I believe, is that the locating force isn't insignificant. Sure, the ARB and your tie rods might keep you on the track, but there are forces other than the torque to consider.
Consider the case of an IRS with inboard brakes. In this case the torques are not being taken through the suspension, but I think we could all agree that you'd still have lateral force in the suspension under braking, and you certainly would want a semi longitudinal member to take that load.
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I was reading one of the project builds on MotoIQ today, and one of products they installed on their project s2000 caught my eye. It is an upper front subframe brace.
Bolting to thick metal of the door mounts and reaching forward to the strut towers, I'd imagine something like this could add some substantial stiffness to our cars, especially if tied into the rockers and used in conjunction with something like the rocker to TC brace pictured below. If done well, I think this could resist some of the 'hinge' action of the rocker to firewall connection, allowing the rockers to do their job a bit better
Anyone have thoughts on this?
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Tony,
Obviously there is no such FIA ruling, and the guy who said that hasn't posted in over a week. No one else is claiming that.
Manufacturers are using it to meet FMVSS roof crush standards though.
I made up some test box sections from wrecked 2+2's and loaded them until they collapsed.
The ones with foam fill were significantly better than the factory stock ones.
The "spot welder gone mad" examples were nearly as good.
There are places for HD foam, they're just not inside steel sections unless corrosion protection can be guaranteed.
Exactly the sort of information I was looking for. Awesome. I was thinking of doing that with my scrap 240 shell when i cut it up. Thanks!
Also, here's another interesting read on foam in an existing unibody and it's effect on stiffness.
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They all slip over. I thought the same thing because the 240 rails are flanged like the originals, but they slip over as well.
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Apparently this was one of the upgrades Mazda did on the RX-8 when they came out with the R3 handling package. Foam filled crossmember. Mazda claims it was for stiffness rather than crashworthiness or NVH reduction.
http://www.roadandtrack.com/auto-shows/detroit/2009-mazda-rx-8
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Yes, the bad dog rails (the additional rear sections that are available for the 240z only) are the commercially available sub frame connectors, though many people make their own out of rectangular section steel as well. They connect the front frame rails and the rear subframe that the rear suspension mounts to, usually replacing the under floor frame rails. There are a number of threads on the subject.
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I was gonna leave this one alone, mainly because of the tone of some of the responses, but Clive's post spurred me. I think WE ALL now know it is NOT A GOOD IDEA for our Z's largely for the rust and future repair issues. I don't think anyone, or at least anyone still posting, is still confused on this.
With that out of the way, it doesn't mean that the thought behind it was necessarily 'stupid' or 'dumb'. Luseboy wants the thread deleted, I believe, because of the tone of the discussion, which I think is a little bit sad. Just because it won't apply to our cars doesn't mean that the discussion isn't worth having. I found the Corvair anecdote very interesting, this is how we learn.
There is solid reasoning and empirical evidence that proper structural foam can be used to stiffen a chassis, even one that wasn't designed for it.
I don't have an SAE subscription anymore and didn't feel like subscribing for this discussion(have an email out to my phd partner to check it out for me), but one of Art Goldman's colleagues published this paper.
The main topic of discussion is, again, safety. That said, in the introduction they get into the stiffness relevant to the original aim of our discussion. They added foam to an existing rocker to B-pillar joint and measured stiffness and fatigue. They, apparently, later did the proper optimization to take full advantage of the material as well, but the initial improvements were substantial(torsional stiffness by 250%!). Obviously I haven't read the article, but it certainly seems promising enough to warrant a closer look.
Does anyone still have an SAE subscription?
We're a forum largely of engineers, we have 'engineered' in our motto, why not have the engineering discussion.
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After many many years of attempts and speculation, Formula 1 is finally coming to the NY metro area. The Grand Prix of America, starting in 2013, will be a race held right across the river in Weehawken/ West New York.
The construction of the track and the cost of participation rights will be entirely privately funded, so there should be no one to complain (too loudly) and get in the way of what will be an amazing event.
The backdrop of the race will be the NYC skyline and, as you can see from the artist's rendering, some residents of both the large apartment towers and East facing townhouses just lucked out, as they will likely be able to rent their homes for substantial sums for the weekend.
I can't wait for this, now I will have two US F1 races to go to every year!
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Pasted and modified from my post here
Last night I went to the shop with the intention of just putting another coat of resin on my gas tank. Fortunately, this only took about 20 minutes to trim the excess carbon and recoat the tank. It's looking pretty good so far, and I'll start to sand and polish it soon.
Done with this so early, I found myself with an evening to work on something else. The tiny rust spot on my new 240z chassis has been eating at me for a little while, so I decided it was time to fix it.
Here is the spot in question. (that circular hole is a factory drainage hole, there's a plug that goes in there)
First I took a wire wheel to the area, removing both the undercoating and the loose, thin rusty metal.
Next, I removed the thinner areas of metal, and made a shape that I could replicate with new metal.
Next, I cut out a piece of cardboard to approximately the shape I need to patch.
Then I traced the outline of the cardboard on some new metal.
Cut out the desired shape and wire wheeled the metal clean.
Fit the new metal in place.
Welded it in place. (this was difficult, as the metal I was patching with was substantially thicker than the existing floorboards.)
Then I started to grind the welds smooth. I ran out of time, so it isn't quite done.
Once I have it all ground flat, I can see where I may have missed some spots welding and can make another pass. It is VERY nice to only have to do this once or twice, rather than ALL OVER THE PLACE on my old car.
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Show me some polyurethane foam that has a Young's modulus higher than steel.
I didn't mean to imply there was one, just that there was stuff much better than the "great stuff" some are picturing here
Nobody's talking about a crash scenario here. We're talking about stiffening up a beam prior to buckling.
I understand that, and I thought I covered that in the post. Sorry if that wasn't clear. Just thought that the ACTUAL benefit of foam filling might be relevant to the discussion too, especially considering the talk of cages and rollovers.
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Yeah, I found an alarming amount of "great stuff" in my 72. Inside the doglegs, in the fenders. They had to have something to lay the fiberglass up against...
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Foam doesn't necessarily mean soft, just that it has hollows. There are some extremely rigid foams out there.
And, yes, from a basic solid-mech analysis, adding a relatively low strength material to the center of a structure doesn't add much strength. Where it truly makes a difference is when the load gets closer to the buckle point of the structure. The foam can allow a structure to maintain its designed form longer, allowing the steel to do it's work more effectively
Here's an interesting link to some testing. I know that it's sponsored by a foam manufacturer, so as with anything, take the numbers with a grain of salt. But if nothing else, you can see how different the failure modes are in the pictures.
http://elib.dlr.de/65654/1/Materialien_des_Karosseriebaus_07_04_10.pdf
Again, not appropriate for our cars, but not an idea without merit in other uses.
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Yeah, the theory of making a structure stronger with a stiff foam is solid. Look at bone or foam sandwiched composites.
It's just that the practicalities of doing it on our cars make it implausible. Also there may be more to gain by more securely tying the rockers into the other structures of the car than there is by strengthening the rockers themselves
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I'll definitely be keeping an eye on this thread.
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Owning both a Z and a Miata, I can say that the Z doesn't feel as low as the Miata on the road. My 240 was pretty darn low before I pulled it apart. I think it has to do with the Z having higher doors and the protection of the roof. I suspect that my Z and Miata had very similar seatbottom heights though.
I don't mind being low at all, the one annoying thing about a car so low is that I feel like oncoming or following cars' headlights are in my eyes a bit more than when I'm in other cars.
Basically sitting on the rear axle is a cool feeling. I feel like I have a much better sense of what the rear end is doing than in longer wheelbase cars.
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Yeah, I drove it to CT and back saturday. It is a solid car, and everything works! I had never heard the s30 seatbelt buzzer before. It was a little hard keeping up with Clive in evilz and Dave in his turbo car on the backroads, but it was a great time. The 260 could absolutely be an everyday car.
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Hey guys,
I have a quick question. Bad Dog rails will be on their way as soon as the rear rails are available (~a week or so). I was planning the install and was unsure of what to do for an undercoating solution. The floors only have 1 quarter sized rust spot in them, so I was gonna patch that and weld in the new rails. The existing undercoating is chipping in places, but there is little to no rust.
Should I:
A - strip the undercoating only where I need to for welding and where it is obviously loose and spray over existing
or B - wirewheel the whole floor and recoat.
I'm not worried about how much work it is, but I am sort of concerned about the transition between the old and new undercoat. I don't plan on stripping the whole bottom of the car, so at some point there will have to be a transition. I'm planning to use POR15 on the inside of the floors, but I know it is pretty picky about prep, so I don't know if it would be the best idea for the underside.
What product would you suggest for this?
Thanks.
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That A pillar rust is frightening! I thought my A pillar rust was bad, but not compared to that.
Yeah, I could pretty much write the book on what what to look for when buying an s30, cause all of it is on my Z. I bought my car when I was a young dumb 15 year old, and was pretty much struck by "fall in love with the first Z you drive" syndrome.
Fiberglass driver side floor - check
Riveted/bolted in passenger floor - check
Bondo over foam rear quarter - check
Poorly repaired frame rail - check
Riveted in galvanized dogleg covered in fiberglass - check x2
Riveted in battery tray area - check
Sclupted silicone covered by paint A-pillar - check
Fiberglass taillight mount area - check
I've learned quite a lot in the past 10 years or so, and I finally have the space to build a car right.
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Hey everyone,
I've been keeping a blog of my work on my Z, but I figured that I should start posting here as well, since 90% of the people in the world who would possibly care about my Z are on here. This post won't have all the pictures I put on my blog, so if you'd like more detail go there. From here on out I will post updates here with pictures and everything. If you're interested, please read through my progress of the past 6 months or so, click through on my blog.
So, the first order of operations on the new 240z is as follows:
1. Remove the factory sound deadening and undercoating from the floors so I can
2. Weld in thicker, stronger, full length frame rails over the originals.
3. Apply POR15 rust inhibiting paint on the floors
4. Apply new undercoating.
5. Put in new sound deadening and insulation.
This weekend I started step 1. Normally this stuff is pretty hard to remove. I have heard a lot of stories about guys having to chill it with dry ice to get it to come off in chunks. Luckily, mine came up pretty easily with just a hammer and broad screwdriver. At the front of the footwell, because of the angle, it was a bit hard to remove. Lacking dry ice, I used the refrigerant from canned air to chill the sound deadening so that I could chip it off easily. I got the bulk of the work done by Sunday.
I also got a bit more aggressive in investigating the rust on my old Z. Needless to say, it's a good thing I have a new shell. I only discovered the rust on the A-pillar after removing door molding. Someone had filled it with silicone and painted over it. Scary stuff...
On monday, having most of the deadening off, I decided it was time to get the new Z in it's proper place. earlier in the week, I spent some time clearing the scrap that was in the back of the shop, mainly to make room for a different sort of scrap.
I dragged my old Z into the corner by myself, just as AY stopped by. He helped me push the new Z onto it's bay.
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Afterwards, we pulled the engine out of his 912, a surprisingly easy process. Disconnect, unbolt and drop it out the bottom. You don't even need an engine hoist, just a floor jack. Good progress all around.
I'm ordering framerails, POR15 and possibly sound deadening this week. Stay tuned.
-W.W. SBSS
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So I was reading about KTM's new 250cc Moto3 engine just now. This engine, like many high performance 4 valve singles, has one exhaust outlet per valve, or two per cylinder. As seen below.
Since all of the talk on here about 180 degree headers and the like, I was wondering whether it would be beneficial for an engine like this to have different length primaries. This thing is tuned for a pretty specific, high rpm being a pure race engine, so you could tune the length to evenly space the pulses for a relatively narrow rpm range. Would this speed up the average exhaust velocity? Could some scavenging effect be achieved? Would it sound like a twin?
Just some thoughts.
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Just saw the Lingenfelter car on jalopnik and was going to share. I'd like to hear that thing without the turbo and out of a dyno room.
Fiberglass door panels w/speaker holes
in Interior
Posted
If they're the same ones that were in the older pics, then no, they don't have speaker holes. If that's a dealbreaker for you, Clive, I might be interested in taking them off your hands, Rayven.