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Learning how to build Lotus Seven replicas...together!
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PostPosted: September 5, 2014, 9:05 pm 
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A few years back I had started a +442 frame a while back when I had officially chosen a motor. Turns out that option was not viable and the project was sidelined for a little while as I thought about options. I decided a +442 cabin with a FWD drivetrain might be interesting and started building a CAD frame, which (since I drive a WRX daily) morphed into a Subie powered Middy. While I tinkered, the FFR 818 made it's debut. I looked at the 818, looked at my frame, and came up with the mash up below...

99in wheel base, Stock FRONT WRX track width in the rear, the front is the same in the pic but, would be a little wider in execution. Ride height is 4.5inches from the frame to ground, tires are the OE WRX 205/55R16 (28.848in diameter). Frame length is 119.7in total lengh as modeled from front of tire to rear of frame is 129.7in. The engine/transmission are pretty damn close using a spare engine and transmission I have in the garage for measurements and locations (minus the exhaust manifolds and turbo) The rear wheels are aligned perfectly with the center of the hub and the CV axles horizontal with where the connect to the transmission. There is enough room to move the motor down an inch or two, which would give the CVs an upward angle. Haven't looked at how much though.

Feel free to be critical, feel free to add MSPAINT bracing (it's not all finished), tell me what is terrible.... I am curious what you fellas think about it? It's purely crude CAD since I am not supremely skilled and I just used it for a visual aid, I can provide the DWG if you wanna look at it that way.




See the second page for the Sketch Up model, and have at it!. The rear needs some work.


Attachments:
Middy Frame V3-1.JPG
Middy Frame V3-1.JPG [ 83.36 KiB | Viewed 2160 times ]
Middy Frame V3-1 side view.JPG
Middy Frame V3-1 side view.JPG [ 42.76 KiB | Viewed 2160 times ]
Middy Frame V3-1 Top View.JPG
Middy Frame V3-1 Top View.JPG [ 52.57 KiB | Viewed 2160 times ]


Last edited by autoxinvr6 on September 11, 2014, 9:34 am, edited 1 time in total.
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PostPosted: September 5, 2014, 10:03 pm 
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Location: Cornholio OR "Where the magic happens"
I believe your going to need a tunnel to provide torsional rigidity.

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PostPosted: September 5, 2014, 10:05 pm 
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Bent Wrench wrote:
I believe your going to need a tunnel to provide torsional rigidity.


There will definitely be a tunnel in there, I haven't decided on placement yet but, wanted to get some feed back thus far :cheers:


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PostPosted: September 6, 2014, 3:40 am 
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Diagonal load paths in the bottom plane.

FYI on these two:
viewtopic.php?f=18&t=13114


Attachments:
autoxinvr6.JPG
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PostPosted: September 6, 2014, 8:40 am 
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:cheers: "Diagonal load paths in the bottom plane" and I would look at adding a scuttle support loop with diagonals from the loop to the top front corners of the frame. Dave W


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PostPosted: September 6, 2014, 10:10 am 
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Miatav8,MstrASE,A&P,F wrote:
Diagonal load paths in the bottom plane.

FYI on these two:
viewtopic.php?f=18&t=13114


Would adding the blue sections to the frame across the bottom still require a tunnel down the middle of the car or would it just be extra benefit? Would having the tunnel change the angles of the middle "V" in the cockpit area?



davew wrote:
:cheers: "Diagonal load paths in the bottom plane" and I would look at adding a scuttle support loop with diagonals from the loop to the top front corners of the frame. Dave W


So from whatever scuttle support is built to the front where the forward "V" in blue that was drawn above?


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PostPosted: September 6, 2014, 10:17 am 
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It's good for you to think this thru in drawings. Are you using SketchUp or something else? There is a library of parts available in SketchUp, including an early middy frame I did. I had a picture of a Subaru and transaxle I imported and scaled and started to build a motor model around, it wouldn't help much but looked inspiring.

I don't think you need a tunnel to make a stiff chassis. Especially in a mid engine car when you have so much potential for space in the passenger compartment. Some of that space adds up to places to put strength like having a forward firewall without a huge hole in it.

- It's important to get the diagonals down the sides the way you are doing. The front most diagonal should go the coil over mounting, that's how the twisting and frame loads start. Likewise to the rear.

- You should have diagonals in the floor the way MV8 has drawn. You can arrange how you like for various reasons as you go along. It is easy to get this strength, the load is lower and the floor is a very wide beam so the strength comes quickly.

- It is very important to get some stiffness in the top. Something like the floor diagonals in the section under the scuttle.

Is this car for casual use like picnics and fun drives or actual track use?

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PostPosted: September 6, 2014, 10:47 am 
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horizenjob wrote:
It's good for you to think this thru in drawings. Are you using SketchUp or something else? There is a library of parts available in SketchUp, including an early middy frame I did. I had a picture of a Subaru and transaxle I imported and scaled and started to build a motor model around, it wouldn't help much but looked inspiring.


These were actually done with the Autocad student license. We touched on Autocad back in my high school days (over 10 years now :shock: ) and I am just drawing trying to bring back in the basics from back then. I never got into making solid tube parts or complex angles or curved tubes (like a roll bar) or making moving suspension pieces though... Gotta figure that out still.

horizenjob wrote:
I don't think you need a tunnel to make a stiff chassis. Especially in a mid engine car when you have so much potential for space in the passenger compartment. Some of that space adds up to places to put strength like having a forward firewall without a huge hole in it.

- It's important to get the diagonals down the sides the way you are doing. The front most diagonal should go the coil over mounting, that's how the twisting and frame loads start. Likewise to the rear.

- You should have diagonals in the floor the way MV8 has drawn. You can arrange how you like for various reasons as you go along. It is easy to get this strength, the load is lower and the floor is a very wide beam so the strength comes quickly.

- It is very important to get some stiffness in the top. Something like the floor diagonals in the section under the scuttle.

Is this car for casual use like picnics and fun drives or actual track use?


The car is actually something I'd like to use in autocross locally, not so much track, occasional street. VIR is 3 hrs from me but, I don't think I would make it out frequently. I would like to enjoy it on the street from time to time. My drive to work is surface streets, and only about 8 miles so it would be nice to take it to and from work on nice days.


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PostPosted: September 6, 2014, 11:05 am 
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Miatav8,MstrASE,A&P,F wrote:
Diagonal load paths in the bottom plane.

FYI on these two:
viewtopic.php?f=18&t=13114
\

The bulkhead/scuttle design from the 23 you linked might be usable here in my case for both front and rear. That would help significantly.


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PostPosted: September 6, 2014, 12:06 pm 
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Look through this http://www.midlana.com

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PostPosted: September 6, 2014, 12:45 pm 
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Definitely check out the MidLana site. I think the FFR818 is difficult for a beginner to follow, so not sure it's a good example for you building your frame.

Here's a picture of where I left off on the midship version of Car9. This is done in SketchUp, I think it's worth moving to that because you can use pieces other people have contributed. In this drawing there are already Subaru rear uprights and a scale picture of the motor and cylinder block. Of general use are the human models and we have various wheels including a nice looking one from Briggs. There are Ford front spindles and Miata, fuel cells, Rod end joints, frames for real Locost and Caterham. Lots of stuff you can just drop in and look at. You can upload your drawings to their 3dwarehouse so you can have backups.

SketchUp is far from perfect, but it's free and work you do can be used by others… If your interested I will update my midi drawing with new parts and do some cleanup.

I remember now the question I meant to ask you was if you expect to use 7 style bodywork or something like Jack's Lalo or Cheapracer is considering something DBR1 isn… Big difference in foot room


Attachments:
Car9_Midi.jpg
Car9_Midi.jpg [ 75.14 KiB | Viewed 2095 times ]

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PostPosted: September 6, 2014, 1:31 pm 
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The Midlana was one of my original middy inspirations. I am not sure if I want to keep the 7 dimensions or not... I was thinking about not really running any body at all and just keeping the car mostly naked aside from some driver protections and protections from road debris.


I will download Sketch Up and play with it. Easier to learn and work in 3D vs AutoCAD? I've got like a week in the above frame and all my variations... haha


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PostPosted: September 6, 2014, 4:54 pm 
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Not really liking working in Sketchup. It feels cumbersome... Definitely nice being able to import other peoples work though.


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PostPosted: September 7, 2014, 12:38 am 
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Here's what I've changed/added tonight.


Attachments:
Middy Frame V3-2.JPG
Middy Frame V3-2.JPG [ 52.23 KiB | Viewed 2053 times ]
Middy Frame V3-2 Front View.JPG
Middy Frame V3-2 Front View.JPG [ 44.69 KiB | Viewed 2053 times ]
Middy Frame V3-2 side view.JPG
Middy Frame V3-2 side view.JPG [ 35.02 KiB | Viewed 2053 times ]
Middy Frame V3-2 Top View.JPG
Middy Frame V3-2 Top View.JPG [ 58.07 KiB | Viewed 2053 times ]
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PostPosted: September 7, 2014, 1:28 pm 
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The more I think about it, the more I think I should just can the 442 that is already built and just start from scratch if I want to go Middy :-(


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