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Learning how to build Lotus Seven replicas...together!
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PostPosted: August 27, 2015, 12:23 pm 
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Did this design ever make it's way into solidworks? I saw back a ways in this thread that it was suggested. I am pondering using this design over the standard frame for a build with a forced induction BMW 6.


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PostPosted: August 27, 2015, 1:38 pm 
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DaveM wrote:
Did this design ever make it's way into solidworks? I saw back a ways in this thread that it was suggested. I am pondering using this design over the standard frame for a build with a forced induction BMW 6.


I don't think it did. Marcus uses Sketchup to draw everything with. I don't think he has access to solid works. If I had access to it I would have.

Which inline 6 turbo engine are you thinking about using?

Those engines are incredibly light for how large they are.

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PostPosted: August 27, 2015, 2:10 pm 
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Hi Dave, glad to see you're interested. There was an early version of the frame that someone (Cheapracer) converted to another format and uploaded to a 3d warehouse. Some searching might find it.

I maintain SketchUp drawings for each of the Car9 frames currently being built and I share them on my Google drive. My goal was for the builders to have a current 3d drawing as documentation for their car. SketchUp is not a highly featured CAD tool, but I think it is sufficient. It has some advantage in that it is free and accessible to anyone and it has parts available from the SketchUp repository and also parts that are shared by people on this site. In addition to the Car9 drawings, there is a drawing of a storeroom with parts on shelves, just like a real shop. I probably have a warped sense of humor.

We have not yet had a person with an I6 in mind. I think it would fit just fine. In comparison to a Locost, I think this frame is a great deal stronger and stiffer, I put hundreds of hours of effort into modeling the frame in FEA. It is well suited for an IRS suspension, has good protection for the fuel cell, and good support for the roll bar.

SeattleTom is doing a great build log that can serve as an excellent building guide. Joshua Briggs is working on a version that is using square tube. My build has a completed frame (mostly) and is waiting for me to finish the design part of my ECU project.

I encourage you to use SketchUp but will provide all the help I can if you go solidworks. Most of the use of the 3D modeling is pretty basic really and if you use it someone else may decide to use your work too. Once you have some basic dimensions you cut the tubes to fit anyway. The first step would be to build a basic box shape that represents your motor and then dropping it into a chassis and seeing what you land up with. Over time than you can keep improving the motor and also transmission models.

Maybe something like this?


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PostPosted: August 27, 2015, 2:46 pm 
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Dave, I used the basic measurements taken off of the Car9 Sketch-Up model to build my chassis. No problem doing so as the tubes all get hand coped anyway. Prior to starting my build I made a simple LS3 model in Sketch-Up using accurate dimensions for the basic shapes to "prove" the fit and reserve drivetrain space. While building the frame I dropped in a plastic LS3 replica engine as I won't have the real drivetrain for a couple more weeks. This allowed me to fit up the mounts, etc.

All my suspension modeling was done with Wishbone and Vsusp. The suspension mounting points measured from build table coordinates and hand fit. So far, so good. I'm very impressed with the Car9 chassis design. Very strong and adaptable.

BTW, I made a living for a number of years selling high-end CAD systems to the aerospace industry, but on this build I found I enjoyed working in the metal more than modeling on the screen :D

Looking forward to reading your Build Log :cheers:

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PostPosted: August 27, 2015, 5:08 pm 
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I'm sure most have seen it in my build log but since I'm the only one that has built a square version of Car9 I figured I should post it up here. Marcus, if you want throw this up on the first page so it's with Tom's frame.

I've had a lot of fun building this frame even though it's no where near finished. Trust me when I say I'm very excited to start working on it again. It's been sitting in the garage for almost 4 months. Sitting there on its build table, "finish me you slacker!!"

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PostPosted: August 27, 2015, 11:57 pm 
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Thanks for the responses guys.

I've used solidworks professionally for about 10 years, but moved to a manufacturing engineering role in January. I have pretty extensive experience with the weldment module of SW. So, I will probably work to remodel this.

I have a '99 528 that had the ECU go bad at 200k. It had a bad ECU, a bit of rust and a bunch of expensive problems looming like ABS module. It is an M52 TU with the aluminum block, dual variable valve timing and drive by wire throttle. A well applied megasquirt 3 will manage all of that with traction control, launch control and more. :-) A small turbo with a thicker head gasket in a light chassis should be a whole lot of fun. (lite, but not too lite) The car is all stripped and pulled out of the garage.

I also picked up a fab table last week. 4 X 8 X 5/8" steel table. It weighs about 900 lbs. Next on the grocery list is a welder worthy of the task. The 20 year old cheapo mig I have now is not going to do the trick. It feels like a build log is in order soon... as in now ish.


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PostPosted: August 28, 2015, 12:09 am 
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DaveM wrote:
Thanks for the responses guys.

It feels like a build log is in order soon... as in now ish.


Yes, newish works for us.

That's a hell of a build table you got. Be sure to post pics of that as well.

What car did that engine come out of?

Megasquirt 3 will solve any ECU problem.

Good luck on your build. Let's us know if you need any help putting it into solid works.

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PostPosted: November 24, 2015, 4:33 pm 
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I'm going to have to go through all the car 9 stuff again. I've been doing some thinking about a proper, race legal cage for my book frame car and the posibillity of maybe going to a hillclimb, but it would be a lot of work and I kind of like the car the way it is now. The car 9 chassis is looking more and more tempting. I also have a suitable donor for a new, better build, in the form of a ratty Tbird supercoupe that I was thinking I could turn into a track car. The extra rigidity of the car 9 design would be nice, and I could do a properly designed suspension with a limited slip diff as well. Even though I like my car the way it is now, there's a bunch of things I wish I had done differently, and a new car might be a good way to change those things.
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PostPosted: November 24, 2015, 5:53 pm 
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turbo_bird wrote:
I'm going to have to go through all the car 9 stuff again. I've been doing some thinking about a proper, race legal cage for my book frame car and the posibillity of maybe going to a hillclimb, but it would be a lot of work and I kind of like the car the way it is now. The car 9 chassis is looking more and more tempting. I also have a suitable donor for a new, better build, in the form of a ratty Tbird supercoupe that I was thinking I could turn into a track car. The extra rigidity of the car 9 design would be nice, and I could do a properly designed suspension with a limited slip diff as well. Even though I like my car the way it is now, there's a bunch of things I wish I had done differently, and a new car might be a good way to change those things.
Kristian


I support this and I say do it!! We need a 4th member to hop on the car9 frame. I've been working on mine again here lately. I had a 4 month break in build time. I'm pretty new to all this and Marcus helped me in every way with the frame. I was the first to build a square chassis so mine was a bit different. Him and I traded drawings for months before I even bought tubes.

Great part of the car9 you can build it to suit your needs in stead of modifying a frame to do so. That's what I loved so much about the idea of it.

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PostPosted: November 24, 2015, 6:28 pm 
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Yeah I would probably use a mix of round and square tube like you did. This won't be a project I'll be able to start for a year or so, but it's looking tempting. I was thinking my next project car should have a roof and doors to be a bit more practical, but that really complicates things. Ideally I'd like to wrap a 63 Falcon body around a tube frame with a small block Ford or an Aussie 4.0 DOHC straight 6 with a big turbo, but that's really not going to happen anytime soon. I keep thinking that if I find a rust free shell I'd pick it up, but I haven't really been looking either.
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PostPosted: November 24, 2015, 8:55 pm 
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Some of the things I really like about the car 9 chassis design is the trailing arms instead of traditional a-arms in the rear to avoid building the extra structure behind the bulkhead for them. Using tabs bolted to the frame for suspension mounts is also a great idea, and one that I wish I would have thought of for my current car, instead of welding brackets to the frame. I do wonder how much chassis stiffness would be lost by making the forward braces for the rollbar bow outwards for more driver clearance instead of being straight. I'm thinking close to a 90 at the shoulder end, then a straight shot to the frame at the front. I guess that would probably be close to not having them at all.
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PostPosted: November 24, 2015, 11:13 pm 
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Just subscribing to come back for much reading. Great looking frame Marcus. I bet it weighs half what my current one weighs.

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PostPosted: November 24, 2015, 11:52 pm 
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Hi Kristian, thanks for offering some outside perspective, I'm happy to hear it.

Quote:
the trailing arms instead of traditional a-arms in the rear to avoid building the extra structure behind the bulkhead for them


It's simple and strong. Some of the versions of extra structure behind the bulkhead, I just can't figure out how strong they are, it's a difficult place to triangulate. I found out later that the only version of the Seven from the factory with IRS had the same layout as Car9, for all the same reasons I think.

Quote:
Using tabs bolted to the frame for suspension mounts is also a great idea, and one that I wish I would have thought of for my current car, instead of welding brackets to the frame.


Completely copied this idea from a formula car I saw years ago. Just doubled the size of the parts, so it's a lot stronger.

Quote:
use a mix of round and square tube like you did.


This makes sense and I think Josh Briggs car is going well. Coping tubes is not all that hard though. One advantage of round tube is it comes in more thicknesses.


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I do wonder how much chassis stiffness would be lost by making the forward braces for the rollbar bow outwards for more driver clearance instead of being straight.


In the past I measured this in the FEA model, but I don't remember the answer. If you drive the car on the street these bars may limit the visibility for the driver and also pose a risk for head injury. They should be padded with proper roll bar foam. If you start a build I can go back into the model and measure changes like this for you.

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PostPosted: November 25, 2015, 12:04 am 
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wrightcomputing wrote:
Just subscribing to come back for much reading. Great looking frame Marcus. I bet it weighs half what my current one weighs.


Mine in the pic above was around 110 lbs give or take 5 pounds for memory lose.

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PostPosted: November 25, 2015, 12:24 am 
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Just subscribing to come back for much reading. Great looking frame Marcus. I bet it weighs half what my current one weighs.


I hope you can at least get some ideas from it. I think you could take a foot out of the length or nearly so. It was originally about 88" but I added a few inches because of how fast some of these cars were going to go on long straights - especially with Lalo style bodywork. If you keep the same basic layout you can stretch or shrink the dimensions, make it less tall and more skinny etc.

This car doesn't really have a transmission or driveshaft tunnel that might help you move things around, get your seat to the middle and move the driveshaft to the side.

The way the bracing works in the engine compartment, if you want to move the engine all the way to the side, that will work and you can adapt the bracing on the other side to make up for that. The bracing in the top of the engine compartment, under the scuttle and across the passenger seat works together. Because of this the engine compartment and passenger compartment are not open sections they are completely triangulated.

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