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Learning how to build Lotus Seven replicas...together!
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PostPosted: October 29, 2008, 4:33 pm 
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Joined: October 1, 2008, 1:02 pm
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Location: Pittsburgh
Hi,

First post, figured I better jump in with something to show!!

Been hooked on the whole locost idea ever since I saw Jeff Underwoods R1 tearing up the track. I set off on a plan for a MC locost, but became disenchanted with the BEC for a number of reasons, none of which are actually valid. Nonetheless, I was undeterred.

Then my thoughts turned to the VQ35 motor out of the 350Z/g35, but it became pretty obvious that some major surgery to adopt the motor was in order. I started down the MegaSquirt road, but my eyes started glazing over when I read about how much tuing was required.

I'm not sure exactly what took me so long to seen JonW's VTEC At-om build, but I reall became enamored with the organic curves and the mid engine design. I started looking for suitable powerplants and have it down to a few that would use a transaxle out of a FWD. The JDM motors like the Nissan SR20DET and DSM 4G63T are the clear favorites, and I'm leaning to the 4G63T just for the aftermarket support as well as parts here in the US as the motor came in turbo Eclipses with ~210HP. Pretty easy to get more power out of them as well, not sure that will be necessary. I also very much liked Phil's LS1 design with the rear bars. ProximaCentauri's build was also an excellent read, and I am truely in awe of his capabilities.

I pit crew for the Baja 1000 every year (except this one) and I also was influenced by the buggy design in the desert. Make no mistake though, I was heavily relying on the Ar-i-el At-om design with modifications where I thought necessary. But this is my first strike at the design of a car, so there are alot of bugs to be worked out.

I basically drew it all from pics and a few numbers I had from Ariels Website. The suspension is just a WAG with no numbers to support it, just trying to get stuff to fit. Seats are Corbeau Clubman size and the dude is 6'.

I know it's probably overbuilt as designed, but that's why I'm coming with hat in hand to ask for advice.

Thanks, really enjoy everyone's build, hope to start mine in the not too distant future.

Peter Owens (Pittsburgh)

Forgive the "kinky" tubes, it takes awhile to render the images when the program (Rhino3D) is trying to get a lot of accuracy.

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Last edited by sailah on October 29, 2008, 6:42 pm, edited 1 time in total.

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PostPosted: October 29, 2008, 6:29 pm 
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Joined: September 25, 2008, 6:13 pm
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Location: Los Angeles, CA
Not trying to be a dick but don't start a topic with the title "Thoughts". It doesn't help anyone help you, and it makes searching more difficult. Forums have a hard enough time archiving material in a good format.

I like the rear cage supports coming up from the tail.

I love and miss Pittsburgh. Used to live in squirrel hill and then shady side. It's a good city.


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PostPosted: October 29, 2008, 6:45 pm 
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Location: Pittsburgh
Thanks, title changed.

I live in Shadyside (ellsworth & Aiken). I'm originally a Mainah, my wife is from Sewickley. Not too sure on Pittsburgh long term, but perfectly liveable while we are here. Unfortunately my shop (mostly woodworking) is out in Sewickley, so it's a bit of a drive to get anything done.

Peter

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PostPosted: October 29, 2008, 7:58 pm 
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Location: Los Angeles, CA
Oh man, we had a lot of parties at an apartment on Ellsworth, mostly school related. I went to CMU. I am sure there are a bunch of students right around the corner.

Pittsburgh is an interesting city, the cost of living is nothing, and the cultural opertunities are really surprising for city of it's size. Steelers, Pirates, Penguins, First Tier Orchestra, fantastic LORT Theaters.

Sewickley is a little far for a shop, and if you were wiling to move the shop, I am sure you could find shop space on the north shore or in Braddock for next to nothing, but moving is a pain.

I love the Corbeau Clubman seats by the way (in look and shape, I've never sat in them).


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PostPosted: October 29, 2008, 11:05 pm 
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The frame looks familiar........

Save yourself some time and consider an MR2 as a donor. Get the mid '90s turbo. They can make more power. Replicate the susp geom. That will save you several hundreds of hours designing rear uprights, susp geom, shifter, front uprights, etc. You'll need those extra hours bending/fabbing/jigging the frame.

You should select the radiator and powertrain before you finalize frame sizing. Build around those critical items.

I'm tearing mine down now for final welding.

I lived in Shadyside for a year when at Pitt in early 70s. Can't remember the street (or much else from those years).


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PostPosted: October 29, 2008, 11:32 pm 
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Joined: April 23, 2006, 8:26 pm
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The model looks really... big. What's the wheelbase and track?

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PostPosted: October 30, 2008, 8:08 am 
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Jon,

Yeah, I had a a few of your build photos printed out for inspiration. :D

I looked into the MR2, specifically buying an entire rear clip froma JDM car. I can't remember why I was thinking otherwise, but may agin look into them. It seems for a decent rear clip complete with everythign including dash/harness/ecu was ~$3000. There's a guy in PA who buys them in bulk for N/A MR@club.com owners and then travels around with a trailer installing them. I don't think he is doing it anymore, but worth a call.

Kurt,

The frame is about 108" tip to tail. wheelbase is 93", track is 63". Once I nail down my donor, the frame will undergo a complete redo to slim down the engine compartment. Prob will spend the winter delving into various books (incuding yours) to get a handle on suspension design, which I am woefully ignorant on.

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PostPosted: October 30, 2008, 8:56 am 
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Looks good! You gonna share your plans with everyone else? :wink:

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PostPosted: October 30, 2008, 9:11 am 
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Sure, it's Rhino3D file which can probably be read by most 3D programs. I have AutoCad 2004 but Rhino is such amore powerful tool for dynamic curves, rendering and setting up a design like this. It's a great program, I started using it when I was a naval architect student.

PM me if you want a copy of the model.

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PostPosted: October 30, 2008, 9:27 am 
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sailah wrote:
The frame is about 108" tip to tail. wheelbase is 93", track is 63".

Reason I say it looks big is how much room there is around the passengers. My seats are have no room on the outside and about 4" between. Than again I'm using a 48" wide compartment and yours must be a lot wider since the wheels are inset relative to the width of the chassis. Just curious.

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PostPosted: October 30, 2008, 9:54 am 
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It's definitely a good starting point, until you have many of the parts on hand that you'd need to finalize the design more. I think if you don't mind the physical size, the extra shoulder room would be welcomed by most drivers and passengers from both a comfort and safety standpoint. My initial thoughts are that the compound curve on the lower main rail looks like trouble to bend, the low height of the cage with the single diagonal look troublesome for the passengers head, and I wonder what kind of interference problems you might face with those underslung lower fron suspension pickups as inset past the main tube as they appear currently. I also don't know how complete your bracing is, but there's probably a little additional triangulation you may want to consider as well. I know I'm being kind of nit picky for an initial sketch, but it's also stuff worth keeping in mind as the design evolves...And since I don't see anything too major to harp on you for, I've got to find something to complain about. ;)

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PostPosted: October 30, 2008, 12:01 pm 
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Location: Pittsburgh
Kurt,

I noticed when I rendered the above view that there is indeed a lot of room compared to a book chassis. I was using the Excel numbers from Jon that stated max width at the shoulders of the chassis. Now while I'm not trying to make an exact duplicate of Jon's or the At-om, I should recognize the wisdom of those who have done this before or are doing it. The seats are Corbeau Clubmans and are true to size, however they will probably end up being moved inboard slightly. I would try and then tighten up the "lovehandles" so as to not be portly.

I'm pretty broad shouldered and my in-laws who share motoring enjoyment are all 6'4".

As I stated, just a first crack at the design. Once I settle on the final donor as many have suggested, I can start clocking in real numbers. I do appreciate everyone's input, it's exactly why I posted up the design. The great thing about Rhino and doing it in 3D is that you can view the model dynamically, spin it around, "sit" in the chassis and see what your sight lines would be. It is also a few clicks to completely scale the model in 1, 2 or 3 dimensions. And since your are drawing in 3D simultaneously on 3 screens, every change you make to one view is automatically reflected in the model. I know I am gushing about Rhino, but it is a really wonderful tool to refine designs before melting metal.


What are the thoughts on having the main tubes CNC bent? I am planning on getting a JD2 bender for the hoops etc, but the long bends would need a tool like a roll bender. For the 4 tubes I need done, seems like outsourcing it would be financially prudent. As well as prob more accurate.

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PostPosted: October 30, 2008, 12:10 pm 
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Driven5 wrote:
It's definitely a good starting point, until you have many of the parts on hand that you'd need to finalize the design more. I think if you don't mind the physical size, the extra shoulder room would be welcomed by most drivers and passengers from both a comfort and safety standpoint. My initial thoughts are that the compound curve on the lower main rail looks like trouble to bend, the low height of the cage with the single diagonal look troublesome for the passengers head, and I wonder what kind of interference problems you might face with those underslung lower fron suspension pickups as inset past the main tube as they appear currently. I also don't know how complete your bracing is, but there's probably a little additional triangulation you may want to consider as well. I know I'm being kind of nit picky for an initial sketch, but it's also stuff worth keeping in mind as the design evolves...And since I don't see anything too major to harp on you for, I've got to find something to complain about. ;)


Driven,

Good point about the front pickup, hadn't caught that. I'll probably need some serious study time with a suspension book and program to get even close to what it should be. The front "box" can easily be modified to drop the lower tubes to allow lower pick ups and no interference. I guess that would also depend on ride height and where the attachment points on the front uprights would be. Probably will end up doing custom spindles as I will have more flexibility. The roll cage will most likely be bumped up as well as the floor being dropped slightly to accomodate someone who is 6'3". I wonder the wisdom oh having the bent top tubes like Jon has for giving the D&P "T-tops".

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PostPosted: October 30, 2008, 12:23 pm 
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One feature of the seats I'm using is that they have side shoulder supports. It makes the installed width of the seat pretty wide so it's probably good you have as much room as you do. Also, the driver's arms hang outside the seat frame, directly below the shoulder supports. For that reason it's good to not have the seats butted up against tubes on either side.

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Midlana book: Build this mid-engine Locost!, http://www.midlana.com/
Kimini book: Designing mid-engine cars using FWD drivetrains, http://www.kimini.com/book_info/


Last edited by Anonymous on October 30, 2008, 12:37 pm, edited 1 time in total.

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PostPosted: October 30, 2008, 12:36 pm 
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In my car, the shoulder clear distance is 51"; very spacious.

Front susp is identical to At-om design. The LCAs are 23" long and travel over a narrow angle. Clearance is not a problem.

Let me know if you can find a shop to do CNC bending. My roll bender needs to be improved with lower aluminium rollers for next use. Otherwise, it worked well. To match tubes all you need to do is lay tubes on top of each other.


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