LocostUSA.com

I have a few simple points to make from a purely theoretical, engineering standpoint. Moving from broad to specific,
1) the entire chassis acts as a single giant member, in theory, connecting the front and rear suspension points.
2) that chassis is made up of individual tubes. duh.
3) just as the wall thickness and size of a tube determines its stiffness, the individual members of a chassis determine the chassis's stiffness.
4) for the same mass (weight) of material, the STIFFEST theoretical shape is a round tube. That's why driveshafts are round tubes. So, if a round tube is the stiffest possible element per weight, that means a chassis made with round tubes is the stiffest possible option.

Note: 1" round tube of the same thickness as a 1" square tube will NOT weight the same.

my 2c.
-Mateo

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Wolfpack Motorsports
N. C. State University
Raleigh, NC

I'm late to the game. Anyway. I really want to do the round tube chassis as well! There are alot of things I want to do. But, for my first, I'm doing the most common setup. My current plan includes making more then one variation of the locost.

I'm one of those with "want-itis", and the mechanical skills to generally make it happen. The only thing I'm missing for a round tube build, is the bender and dies. There are just several places where I don't think welds should be. Yes, I realize there are million of man hours of production behind the current design. Doesn't mean they were right. In competition, following someone else is a sure way to finishing second place. No, I have no immediate plans to become a great weekend racer. If something breaks, I'll fix it. No big deal. I've seen alot of welds on alot of these build's. I can tell you just from the looks of them, the tubing certainly is not the weak point, but nobody seems to mention that. Use round tube, your crazy.... Square tube with booger welds is much stronger.??? Questions a 50 year old design, you're crazy!

I've also noticed if you are looking to do something a little different with your design, you should be posting on Australian sites, which are alot more receptive to alternative designs and creativity.

Hey, it's your car, build it the way you want, and then you take responsibility for building it that way. And if you have a question, I'll still try to help.

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Going fast in a straight line has become boring.

Yes those imginative, innovative, crafty Australians are soooooooooooooo much better to discuss these matters with.

dewme5, you make this statement based on what?

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

Well, I hope you stick around and help. I expect to be up to my ears in problems soon. But, really, your coming across with a chip on your shoulder here. You want a round tube frame, go ahead. I think in many cases a mix is the best solution.

I don't think there is anything like a million man hours in frame design for sevens. By orders of magnitude. People question the original design all the time - that's what the discussion here is about.

So be helpful, be an example of what you would like to see. Not much help in this post though....

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

as I read thru this post, at almost every turn, there is somebody telling bikeindirt that he shouldn't do something. Watch out, the project will never get finished. watch out, round is weaker in 2 directions. Just read thru this thread from start to finish, and you will see what I'm talking about.

There is absolutely no chip on my shoulder, and I love this site. I also have no problems with anybody on it. BUT for a site about building it yourself, there sure are alot of "dont' do that's" going on.

The reference about the Aussie sites, has to do with a whole culture mentality. America likes to buy it in a finished state for the most part. Aussie's do alot more resourcing as a norm. Here in the U.S. people think they have a "custom" chopper when they buy a harley, and have the dealer bolt on some saddle bags.

My whole point. of "Hey, it's your car, build it the way you want, and then you take responsibility for building it that way. And if you have a question, I'll still try to help." is not a bad thing, it's a good thing. I don't mean I'm the only one who is willing to help, or anything like that. When you do something that no one else is doing, you create a unique situation, and always with unique problems. When you run into those problems, people are still willing to help.

My last real project was a twin turbo, 380hp Mopar crate motor, t-56 6-speed, fuel injected, 1969 barracuda. Lets just say I'm familiar with "unique problems" The people at Moparchat helped me then, and I still return the favor years later. As far as I'm aware I am the first individual to mate a t-56 behind a small block mopar. All told, I had just over 500hp to the rear tires, and 24mpg in the city. Was it perfect, not even close. Before I blew it up, it was a blast to drive though. In fact, it was a blast right at the end. (to much boost, to little fuel). I learned.

Back on topic, to many people are filled with why you shouldn't, that what should isn't getting done.

I say make it round.

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Going fast in a straight line has become boring.

Wait, so if someone comes on and says he's going to build a twin-turbo V8 Mopar and run it at 13:1 AFR, you're fine with that?

Sometimes people have very good reasons for saying not to do something a certain way. As long as they list the reasons why, it's a perfectly reasonable, and informative, post.

Just because someone says something contrary to one's wishes doesn't mean that they're automatically wrong.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I don't think that playing devil's advocate in attempt to show some potential problems an individual may encounter with a proposed design is being discouraging. As long as the warnings are based in truth, they are valid and need to be considered.

I don't see where anyone has refused to help Bikeindirt because he is doing something different.

I think your stereotype about Americans vs. Australians is a bunch of hogwash to be truthful. I don't think anyone on this board is the "American" you describe in your post. I think everyone here is resourceful and innovatative or they wouldn't be here researching how to build their own car.

But hey to each his own right? That's the beauty of message boards, if everyone agreed there would be no good discussion.

I hope you and Bikeindirt build some great round tube framed cars.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

I'm not playing devils advocate. I work AS a mechanical engineer, I am not formally trained. I work with others that are, and there seems to be a large problem with rules and reasons why something won't work, just because the rules were already established..... without trying Sure, sometimes there are good reasons, and you can learn by others mistakes. Sometimes the better way is the one you don't know about. Sure, I've done stuff that others could do better. I don't have a problem with someone having a better way, or doing something different, and turning out better then mine. If I try something and I fail, does that mean no one else can do it right?? that's just crazy.

"Wait, so if someone comes on and says he's going to build a twin-turbo V8 Mopar and run it at 13:1 AFR, you're fine with that?" what does that have to do with anything I said? Now, if someone wants to put a twin-turbo V8 mopar with T-56 in his locost, I'll have some tips on mating the tranny to save some effort and money. The turbos/fuel, I'm probably not the person to learn what to do from.

I'll highlight a few things I'm talking about.

"the original chassis was designed to use the properties of square tube. Swapping square for round tube would change the properties of the chassis. It would weigh less but could be weaker."

"A structural analyses before starting would prevent you discovering that the product of your labor was an ill handling beast that didn't respond to chassis tuning. "

"Slow down, dude. All of us started like you. A newby with a better idea. You're not the first. "

"Far far more Locosts are started than finished. The odds are already against you completing one, so why add to the challenge by changing a proven design."

"my sincere apologies for the discouragement, but congratulations on the 'FU I'm going to do it anyway attitude' Wink"

These are some of the highlights which I originally referred to. Although after reading thru the whole thread again, it wasn't as negative as I first read.

I still say, if you want round, build it round. Of course, do the research and make it work correctly. Make it safe, but most important, make it.

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Going fast in a straight line has become boring.

Looks like nothing but good advice to me. Certainly nothing that should discourage a confident, determined builder.

I look forward to seeing some round tube chassis. If you haven't already, look at the pics in the building from a kit section for the pics of the round tube Coveland chassis.

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He is a wise man who does not grieve for the things which he has not, but rejoices for those which he has.

I did look at that link for the cloveland, and I thought it looked really good. Wish there was more posted on it. I'd really like to go with a round tube, but I'm thinking the first one is going to be square tube. I'm not decided just yet. Round tubes just look more "finished/professional" in my opinion. I know there are many advantages to building using square. Of course I'm one of the many who thinks there are a few improvements that could be made. In my defense though, the original was designed for a different motor and trans, and the general public. When designing for personal goals/use, there are concessions that are acceptable. As an example, with a bike motor being smaller, triangulation in the engine bay can be improved (I think).

So..... beyond dealing with cutting fishmouths, difficult measuring, and troubles concerning body work. What should people pay attention to while they do a round tube chassis.

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Going fast in a straight line has become boring.

Measure the stiffness when your done, we'd all like to know how it comes out. Especially if your basically going for 11/4" round vs. 1" sq., which weigh the same...

Maybe skip the ERW type and get seamless 1020? It's unfortunate that they don't make a variety of types of square, but it's optimized to be in-expensive, so far as I can tell.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

Something to be considered is that free advice should be always considered as worth what you paid for it. Listen, consider, research, then make your decision. If your decision dosn't work be prepared for some I told you sos.

I believe the original 7 was a combination of square and round but then again the original was a modded 11 and designed for skinny tires and about 50 hp.

Conventional wisdom once was that the world was flat and we all know better now. Learning is generaly doing something "wrong" then figuring out how to fix it.

I'm always ready for I told you so's. In fact you can go ahead and start, even though I'm a few weeks from cutting my first tube. Hey, IF it comes out looking and performing good, don't be scared to let me know that too.

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Going fast in a straight line has become boring.

I haven't read this entire thread, just the first few and the last few. So forgive me if I repeat.

I think it's already been established that round is stiffer than square (in most instances). I for one think the round would make a much more attractive chassis.

But, I think for our purposes, square is better for several reason.

It's easier to cut the weird angles
It's easier to weld
It's easier to locate and attach mounting points
It's just easier to fabricate with
And for our purposes it's plenty strong enough (for most applications).
Did I mention it doesn"t roll off of the table

Personally, If a guy wants to take on the round tube chassis I say have at it.......and post lots of pictures. Do a good job and it should be beautiful.

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RacerDan
+442 Chevy 2.8
Never be afraid to try something new. Remember, amateurs built the
Ark, professionals built the Titanic.

Hey BID, just came across this:

http://locostbuilders.co.uk/viewthread.php?tid=19676



Check out the builder's site for lots of good ideas: http://www.seven-nl.tk/

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Before you judge a guy walk a mile in his shoes. Then when you judge him, you've got a mile head start and you've got his shoes on:)