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Learning how to build Lotus Seven replicas...together!
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PostPosted: June 28, 2012, 12:55 am 
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I've been working on my thoughts about how to build a space frame for a Seven / Locost style car for track use for several months. Much progress has been made, but there still remains more work.

My thread in Automotive Talk, messy shop, is over 20 pages long now. In the interest of getting more eyes on this and reducing what people have to read to get up to speed it seems like it's time to start a more specific thread here.

So first off the project name is Car9. I am not great at naming things and not only are the names like Decimator 5000 already taken, but they also have a poser quality to them. With this name we are leaving open the possibility to go to a Car11 in the future. I am open to suggestions on everything from names to design to implementation. All the work I am doing and the work of people contributing is being made available, as posts on this forum and models that can be downloaded from here or the Car9 web site or the SketchUp 3d Warehouse or wherever.

My goal here has been to produce an improved chassis for building a locost, in particular for road racing. It is easy enough to convert a road racing car into something to take on a picnic, but the reverse is not true. It can be difficult to make a weak thing strong, but not so difficult to take a strong thing to a picnic. A car for road racing is required to have a roll cage and it is encouraged to use these cages to stiffen the car. So Car9 integrates the roll cage and the chassis as much as possible for efficiency. For street use some of these tubes may be omitted and you still have a very robust frame which provides protection for it's passengers.

Builders often face having to make choices or modifications to the frame to employ their desired components. High on this list are larger engines / transmissions and independent rear suspensions. Car9 does not depend on it's driveshaft tunnel to provide strength or stiffness. I think this is better invested in material around the passenger compartment that can help protect this car's precious cargo. It does not have a rear suspension box which is difficult to support properly and can potentially hurt the passengers in a rear end collision. It does have high strength tubing around the back of the car and a well braced roll bar.

The engine compartment is considerably larger and the tubing is arranged to be more adaptable to rearrangement. The front of the frame is wider so the steering rack does not need to be modified. If you want you can shrink the front and shrink your steering rack. My original intent was that it could wear bodywork for a Locost, noses and scuttles that are adjustable should fit but that needs to be checked.

In the SketchUp models you can put items in to different layers and decide which you want to view from a menu. There are currently 25 layers in the Car9 SketchUp model. So you can display a V8 engine or a Ford Duratech or display them both at the same time to compare. There are layers for Ford IRS and Subaru IRS parts, these layers also include changes to the frame to go with the parts.

Currently working on the rear suspension geometry and mounting and also some transmission/driveshaft tunnel and footwell/firewall stuff.

Some statistics. The frame is currently coming in around 175 lbs., I'll admit it's heavier then I wanted. That does include a roll cage and the stress on the tubing is very low. For the moment, I think this is the right way to present this since some people will use this for the street.

This frame is showing around 8000 ft-lbs/degree of stiffness and that goes to 11,000 ft-lbs/degree with the addition of a short tube across the passenger area.


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Car9Gstab32side.jpg
Car9Gstab32side.jpg [ 132.62 KiB | Viewed 14745 times ]

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.
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PostPosted: June 28, 2012, 6:46 am 
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Well done, Sir!
And quite generous of you to share your chassis after all the work that went into the design.

:cheers:
JDK

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PostPosted: June 28, 2012, 9:11 am 
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Excellent. I've been following the MessyShop thread since the beginning. I'm afraid I don't have anything useful to add other than a "well done"! :cheers:

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PostPosted: June 28, 2012, 9:26 am 
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horizenjob wrote:
This frame is showing around 8000 ft-lbs/degree of stiffness and that goes to 11,000 ft-lbs/degree with the addition of a short tube across the passenger area.


Damn humans... jeez. Why can't they just be a dense lump that we can locate low near the center of the car?

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PostPosted: June 28, 2012, 11:01 am 
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Acerguy wrote:
I've been following the MessyShop thread since the beginning.
Well I haven't! This is a splendid example of why we should give our threads appropriate names. I never once looked at Messy Shop 'cause I figure I've got that messy shop thing down to a science and I don't have much to learn on the subject. Plus it was in Automotive Talk, which is fun when I have the time but not a forum full of useful knowledge and...man, I'm sorry I missed this.

Two quick Qs before I pore through the pages of yore: do you have one of those cool 3d thingies where the viewer can rotate/twist the model without entering it into a CAD program first (and if not, where can we find the latest of top/side/front/rear views), and are the materials listed somewhere?

That's remarkable work. And there's one under construction?

PS--why "Car9"?

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PostPosted: June 28, 2012, 12:04 pm 
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I downloaded SketchUp Lite (or whatever the free version is called) and duh, ignore my"...without entering it into a CAD program first.." question. That is one fab little program for us novices.

Now I want to know where I can find the latest version of Car9 (the one on the OP would be good) so I can examine it to my heart's content.

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PostPosted: June 28, 2012, 12:39 pm 
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Quote:
Why can't they just be a dense lump that we can locate low near the center of the car?


I would say, and not happy about this, that my body shape is trending that way despite my efforts. :rofl:

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Well I haven't! This is a splendid example of why we should give our threads appropriate names.


I'm glad I finally did. I didn't want to be presumptuous when I first started and then I didn't split the topic up soon enough as i kept plowing onwards.

Quote:
do you have one of those cool 3d thingies where the viewer can rotate/twist the model without entering it into a CAD program first (and if not, where can we find the latest of top/side/front/rear views), and are the materials listed somewhere?


The drawing is done in Google SketchUp, which is a free product available for Windows and Mac OSX. It's pretty easy to use and for just panning and zooming you can get the hang in just a few minutes. I can export the files in COLLADA format which I think some of the big programs can digest. Autodesk is listed as a contributor. http://en.wikipedia.org/wiki/COLLADA

I see from that wikipedia article that Mac users can just load the diagram into preview for a 3D look. I haven't tried that but will do that latter today.

The materials are 1 3/8" x .083" DOM tubing for the cage ( yellow ). This is the SCCA spec for cars of 1700 lbs. and lighter (with driver) for road racing. The red tube is 1" x .065" tube, purple is 1" x .065" square and blue is 1" x 2" x .065".

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That's remarkable work.


Thank-you very much. I think this chassis is a good match for a Lalo body. Car9 is a bit wider in front and uses a standard length steering rack. No problem to widen the footwell a bit for 3" more room. The higher frame rail is hidden under a Lalo body.

The roll hoop forward braces are required for wheel to wheel track use, but not for the street - so acrobatics to get in and out are not necessary.

People wanting to add more choices can contribute that work and it can be maintained in the same files in different layers. This way we can all move forward without so may different directions.I hope that makes it easier for people wanting to follow in our footsteps.

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


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PostPosted: June 28, 2012, 12:47 pm 
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https://sites.google.com/site/car9buildit/home/downloads

Look for the SketchUp model, it's a couple of items down. I try to upload there once a week or so. Seattle Tom is helping me with some suspension design and working on a better engine model, so we find it easiest to coordinate by keeping the most recent files on that web site. Better then pawing thru forum threads constantly and It's a useful backup too.

I just uploaded now. When you look you'll see the car model in the foreground and then a pile of junk and a workbench in the background. Half sense of humor and half usefulness. The workbench has Miata, Subaru uprights a chunk of frame bracing on it. The workbench exists because it can be easier to measure parts from a reference plane and sometimes even make jigs for things. I think it's hilarious that it works out that way sometimes.

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Car9 Roadster information - models, drawings, resources etc.


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PostPosted: June 28, 2012, 1:43 pm 
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Marcus,

Car9 is progressing really well. Nice piece of work. I'm hoping to begin my V8 build this fall.

I'm a day or so away from uploading an LS3 SketchUp model to the Car9 website. I finally watched the SketchUp tutorials and they really help with understanding the SU package. Here's a teaser of my work-in-process on the motor model. It's based on the full-size Datadrawing I bought some time ago. So it should be accurate enough for space reservation and placement studies and should fit well in Car9.


Attachments:
LS3 draft model.jpg
LS3 draft model.jpg [ 81.7 KiB | Viewed 14652 times ]

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My Car9 build: viewtopic.php?f=35&t=14613
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PostPosted: June 28, 2012, 5:34 pm 
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JackMcCornack wrote:
PS--why "Car9"?


Because Car1 thru Car8 caught fire, fell over and then sank into the swamp...

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"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: June 29, 2012, 1:31 am 
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Tom, thanks for making a better engine model, this looks great! The extra detail will help and it will look more inspirational in the car. Getting the exhaust ports in the right place and also the motor mount locations will be a big help. I'll put that right in when you get it uploaded.

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


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PostPosted: June 29, 2012, 9:00 am 
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This is awesome Marcus, thanks for your time offered to others to add and improve on what is one of the last areas of innovation left for the common man, you're a Chapman, errr, Champion :-)


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PostPosted: June 29, 2012, 10:46 am 
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horizenjob wrote:
People wanting to add more choices can contribute that work and it can be maintained in the same files in different layers. This way we can all move forward without so may different directions.I hope that makes it easier for people wanting to follow in our footsteps.
I haven't even figured out how to select individual components (the side of the roll cage is one piece, for example, and I'd want to be able to select/adjust tubes were I nervy enough to "add more choices"). Do I need to get SketchUp Pro?

This is truly marvelous. I'm going to send you an IM later, 'cause I don't want to look like a fawning fanboy in public.

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PostPosted: June 29, 2012, 11:22 am 
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Because Car1 thru Car8 caught fire, fell over and then sank into the swamp...


Please give me credit! They exploded, caught fire and sank. I can say now, it doesn't matter how much hydrogen you put in the frame, it's just a bad idea.

I'll try to post the changes I'm making so there is some sense of a change history. So below is most of what I actually changed yesterday after I uploaded the model. I will also put up a post today that describes some status and what still needs to be done.


Changes:
- I put the two sets of pedals into their own layers now so that you can choose between Wilwood reverse mount swinging pedals or Tilton floor mount. I should draw up a set of BEX swinging pedals and make that a default. The hanging pedal set from Wilwood looks like it will likely interfere with the steering.

- Put sleeves in the frame for the rear trailing arm mounts.

- Fixed the 13" wheel center to match inside of rim. Now it can easily be adjusted for offset using the ruler included in the rim. The rear rims are now 13"x8" x 12 mm offset and they seem to fit the Ford IRS uprights.

- Moved the headlights into their own layer from one of the bodywork layers

- Removed the work for an inboard front suspension. If you want an inboard suspension, do it right and buy a Lalo body! Started making the left and right front suspensions the same. The verticals are now in the side components so edits will match side to side.

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SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


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PostPosted: June 29, 2012, 11:37 am 
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JackMcCornack wrote:
I haven't even figured out how to select individual components (the side of the roll cage is one piece, for example, and I'd want to be able to select/adjust tubes were I nervy enough to "add more choices"). Do I need to get SketchUp Pro?
Jack, I highly recommend the SU tutorial videos. They are short, to the point and get one started with the SU toolkit. The "Welcome" page will point you to them. You can do a lot with the free version and some of the free plugins. I'm not sure why one would need the Pro version.
Quote:
thanks for making a better engine model, this looks great!
Thanks, Horizonjob. It was actually "fun and easy" once I watched the videos. I think I've found a way to make a decent looking bellhousing in SU. That should help with space planning in the footwell area. Vintage races are this weekend, so it may be a few days...

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My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."

Ultima Spyder, Northstar 4.0, Porsche G50/52


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