So I have been playing with the idea of adding a couple more tubes to the back of the Anklebiter. If you were to replace the back half of a 914 with tubes where would you put them? Here is a rendering of the original cage (red), drivetrain (Grey), and points that need to be tied in (green).
What would you do?
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Here is my first draft, any thoughts?
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Dam. Just cut the body off the pan and build a whole tube frame
I would like to keep the passenger compartment intact, I know it seems like a contradiction but I would like a nice stockish interior with a pretty stock passenger tub.
Ury, that stock starter looks heavy ...
Aha, i see you replaced it in the second pic ...
I was thinking of yours when I was working on this Ury, it is amazing how much more complicated things get when you cut off the rear frame rails.
The plan would be to eliminate all sheet metal behind the firewall but I would replace the stock cross member with a tube between the mounts.
More examples, some better, some not so much (IMHO), just food for thought ...
I like the design you posted. You really do need many of the bars because of the load paths, but IMHO it isn't overkill as long as you use correctly sized bars. With sparing use of .035 and .049 wall tubing you can keep the structure light in incredibly rigid.
The tube from the long too the motor mount wont be doing much the way it is, and would be better served meeting the cage w/ the other tube.
Likewise, the inner vertical from the motor mount up to the hoops will not be as strong as if they go to the "shoulder"
Last (and probably way overkill, but i've been doing Baja Trucks) would be a support from the upper shock mount down to the motor mount.
Could probably lose the bar between the trans mounts, there wont be any stress in that direction back there.
Tube wall thickness is another factor, I like the concept of using more light tubing versus less heavy tubing. No need to worry about racing rule books so any size that is appropriate is fair game. I like Jim's ideas, I was thinking 1.5 dia. what wall thickness would you guys use and where?
Cost no object I would go the route Hari Matsuda went. Not to shabby for a 72 year old. Actually these pics are a few years old.
Hari ran a few different cars but he did things with a 2.0 186 HP four / 1730 lb car that others running six's COULDNT do. The four cylinder was 100lb lighter than his later 3.4 car. The light weight car just by weight alone was 1-2 seconds per lap faster than the heavier cars. I am a believer in light weight versus BIG Horse Poo. Quicker and faster to a stop.
The orange car in the pics is the 3.4 that weighed in at 2080 lbs. Evil on the track.
When Hari was 69 years old he considered converting this car to street legal.
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Hari's latest configuration was this.
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500hp puts you in a different crowd than my car. Here are I few that I've found over the years.....
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I have more pictures but I'd have to spend the next day scanning them. As you can see, everyone has thier own ideas on how to do it. There is no right way or wrong way just different ways.
A Celette would be slick for a tube chassis. You'd have all the suspension pickup points, enigne and transaxle mount locations and if you ever wrecked her you could replicate the chassis. Some cool photos in this thread! I totally agree with sir Andy though. Stiffening is a good idea but the 914 chassis is pretty good. 500 hp good though?
The 914 chassis is far from good. I think the factory chassis stiffness is on the order of 2500lbs/deg. That is really weak. The factory chassis is a noodle.
As for the tube chassis. I would use 1.5x.045 and 1.5x.065 tubing. No need to get really big. Sheridan's car is probably the best engineered solution. It was done by a professional race car engineer. If you are going to do it I would toss the factory rear suspension and come up with something different. Mount the engine, tranny and suspension to an independent cradle. Then you could fix the 914 problems. The problem isn't flex in the rear of the chassis though. It flexes in the middle. So you will not gain much buy changing the rear. Plus the rear is pretty light because it is all sheetmetal.
Thanks for the input guys, lots of great pics. I am going to try to remember my statics and mechanics of materials classes from when I was in engineering so I can calculate some loads. I figure if I use predominantly .065 wall tubing the entire rear structure should weigh around 50 pounds.
Top of shock tower (bridging the hidden gap between frame rail and tower) and suspension ear are the two most important points. Much more is overkill and excess weight. IMO.
You build it and some will like it, some won't. Some will say it's too heavy, some say it's too light. Some will say it should be painted black, some say paint it white. You get the picture......
some one needs to design a full tube frame car...the buggy guys can build these things cheap.. Throw on a fiber glass body and youd have one hell of a DE car!!
Were I going to the trouble of building a tube frame, the first thing to go would be the Mac strut suspension & swing arms. Double A's all the way....just like a real racecar.
Are you still in school? If you are you should grab a copy of SolidWorks and model what you are building. Then you can use the integrated FEA software to mess with tube sizes. Its quite easy to use (and there are some great tutorials about building tube frames in it on Youtube), and would really help you out with choosing tube size.
Ohhh to have the time to entertain these things!!!
Dana,
How's my old rommie doin? How is Becky? How is Laurie? Hope all is well.
I'm not too good with this kind of stuff, but as far as solid works goes they have a nice set of tutorials on youtube http://www.youtube.com/user/solidworks... I believe they explicitly cover frame design in the tutorials. The FSAE team I'm on uses NX for frame design, I'm not sure what is used to analyze it though....
As I said I'm not very good at this, but squares are bad, triangles are good. These two seem to jump out at me.
Sorry, but I can't give you much better advice. I haven't really been involved in that aspect of our car's design...
My Qs are in blue. You already have the crosses to the tranny points done so those are redundant for this conversation.
Inside the blue circle... Why would you go up there? To me, the strong point to tie into is the tip of the blue arrow as that's what ties forward. I would ignore anything above it.
So top of shock tower forward to that point (my blue bar) is the strongest and most important piece in my mind.
Outer suspension point is strong by default. Inner ear needs some bracing. Doesn't make a huge difference where you go with it, I just put a blue bar to the strongest point in my thinking. Your green bar that goes lower is fine. Or just use Chris's kit (Tangerine).
Given that weight is important in your build, I just want to see you only add bracing where it's most effective, and not where it's really superfluous.
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IIRC, the "Birdcage" Maser was a very early tube-frame design, and not necessarily all that successful I think. You'd probably do much better to check a modern racer, or maybe one of the Sports Racer (e.g., DSR) cars for ideas rather than the Maser.
--DD
200 tubes
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how much wire do ya think they used here?
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