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 Post subject: The Gecko Project
PostPosted: January 28, 2008, 5:51 am 
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Joined: February 1, 2006, 3:02 am
Posts: 317
After a long hiatus due to family and health issues I've finally been making some visible progress on the Mk2 chassis (Mk1 got cut into bits, the longer of which are becoming braces in Mk2 :) )

It's still going slowly but it is progress. Some pics are in my Picasa gallery (linky) which also gives some sense of the design to put the photos in some context. The last 4 photos are new today.

It's still a long (long, long) way from being finished but I feel more confident that I might finish it before I retire :)

Dominic


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 Post subject: Gecko progress
PostPosted: January 28, 2008, 3:47 pm 
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Joined: January 22, 2007, 5:13 pm
Posts: 313
Location: Anchorage Alaska
Looks real good!

I like the double upper tube layout in the cockpit area and double diagonal braces below. Very sensible and safe design. Of course I would think that since it is very similar to what I plan to do. I am putting the double upper tubes at shoulder level though, say about the top height of your scuttle ring frame. Yours will be easier to get in and out of though since they are lower.

Balsa models are great, eh? I built two this weekend of different designs. They help fight the "Paralysis by Analysis" disease too. And it is so much faster to change the wood model than the full size steel version. Besides, Staniforth considers it an essential part of the design process. Balsa FEA.

I am looking forward to reading more about your build. Keep it up!


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PostPosted: January 28, 2008, 3:59 pm 
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Joined: April 23, 2006, 8:26 pm
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I, too, want to use high side tubes, but am concerned that in even a mild side accident, the driver's head will whip sideways and smack the very tubes designed to protect. I'm still working this out.

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PostPosted: January 28, 2008, 4:02 pm 
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Joined: April 23, 2006, 8:26 pm
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Location: SoCal
Hey where'd you get your driver, "Woody"? Sure beats trying to make one as long as he's scaled appropriately.

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PostPosted: January 28, 2008, 4:48 pm 
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Joined: September 19, 2007, 8:13 am
Posts: 33
Location: Naples, FL
KB58 wrote:
Hey where'd you get your driver, "Woody"? Sure beats trying to make one as long as he's scaled appropriately.


local crafts store should have them.


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PostPosted: January 28, 2008, 7:41 pm 
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The voice of reason
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Joined: January 10, 2008, 4:47 pm
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Location: Massachusetts
I've been wondering about padding the tubes. What's commonly used in SCCA?

From what I'm seeing in pictures people are too casual about this. During a real accident, your spine can stretch 5 inches and your neck 6 inches. So you can easily contact thing you won't expect. And your head can snap back and hit things really hard. In one accident I was wearing a 4 point belt, 3" straps and at impact I remember looking down between the top of the steering wheel and the dash. On another occasion, without a helmut, I remember thinking how soft the drivers side window was as my head went thru it.

There is some approved stuff. It is claimed to be very stiff and rigid. It should be, just like the rigid foam inside a helmut. This is 1" thick material.


http://www.pegasusautoracing.com/productselection.asp?Product=2395

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PostPosted: January 29, 2008, 12:44 am 
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Thanks for the responses guys. A couple of answers/comments:

Kurt, as bluej says, the mannequin is a standard artists model, available from any art and craft shop for a few dollars. They seem to come in a few sizes - mine is 300mm/12"tall which makes him about right for 1:6 scale models which, coincidentally, is a reasonable size for desktop work. Much smaller and the model becomes fiddly to work on and too fragile, much bigger and it's just unwieldy. A 1:4 model of my car would be 825mm/33" long!

On the subject of double tubes - they're there to add strength to the frame that would tend to come from the centre tunnel in a Locost. There are a couple of other benefits:
- the double tubes make the portal frame ring at the dashboard bulkhead an easy and obvious improvement
- they add some side impact protection
- they'll give me a little more elbow room if and when I have a windscreen and side curtains
- they push the horizontal mid line of the body out, breaking up the potential slab sidedness that is a risk with middy clubman shapes

Would I put tubes like that up at shoulder level? In a street car, absolutely not! As Kurt says, they're a terrific way to bash your brains out. In a track only car, where you'd ALWAYS be wearing a helmet, I'd think about it but I still don't think I'd like the idea.

I've noticed that there's no "manifesto" post here from me to outline the project, so here goes:

-- The Gecko Project --
Named after the lizard because they're small, quick and have sticky feet.
Frame is my own design that really owes nothing anymore to the Locost.
Engine/gearbox is 2006 Mitusbishi Lancer 4G69-MIVEC. I originally was using a JDM Corolla 4A-GE 20 valve but registration difficulties with that engine here in Australia forced a change. Plus, I got the MIVEC cheap :)
Front suspension is Gemini (Chevette) uprights and Locost-type wishbones.
Rear suspension is Corolla uprights and struts, modified to coil-over. Uprights are tied to the frame with a toe-control link where the steering arms attach. MR2 rear brakes bolt straight up to the Corolla uprights and have handbrake mechanism.
Wheels are 15x7 3-piece mags - 4x100PCD, RWD offset.
Bodywork is mostly ali over the frame tubes with a fibreglass nose and guards.
Dimensions:
Wheelbase 2400mm/96"
Track 1480mm/59"
Overall Length 3300mm/132"
Overall Width 1690mm/67.5"
Height - at engine cover 860mm/34.5"
- at roll bar 1100mm/44"
Weight (projected) 700kg/1540 lb


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 Post subject: GECKO goodies
PostPosted: January 29, 2008, 1:54 pm 
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Joined: January 22, 2007, 5:13 pm
Posts: 313
Location: Anchorage Alaska
Thanks for the specs on your build. Always nice to know the defining features of a new design.

As for shoulder height top rail dangers...
Very good concerns have been stated. If your noggin hits a metal tube you are going to lose. So you do not want a tube in reach. That is why the new cars with side curtain airbags are a huge leap forward in safety. A side impact is generally going to do some serious damage to the occupants. Much worse than a front or rear impact where the seat belts and headrest gives you some protection.

Of course, what is shoulder height for one person is forehead height on another. I consider the Ar-i-el At-om top tubes to be slightly too high for the average driver I have seen pictures of sitting in the car. But most of our designs have no side impact safety. No more really than a motorcycle. Unless of course, the side impact is something lower than knee high. :? I enjoy doing exciting things but I want to be as safe as I can reasonably be too. We each have to find our own comfort of safety zone, eh?

I feel the most vulnerable when sitting at a red light at the intersection knowing some idiot may well think he can make the corner on the ice at the speed he does in the dry, and slides into those of us sitting there. That is a fairly common collision up here, T-bone the stationary cars at an intersection. Very, very bad results. When you are driving you can do something to avoid a crash, but sitting? Maybe that is the "sitting duck" syndrome.

I realize I look at things from a different viewpoint from many. For one thing I am 6'-4" and another reason is that the common vehicle on the road up here is an SUV with a bumper height of at least 24" and many seem to be right at shoulder height when I am in my Miata. I have lowered the seat in my car to I fit me which puts the top of the door (beltline) at shoulder height for me. My wife (5'-1" if she stretches) has to sit on a pillow to see over the steering wheel.

(EDIT) I checked my door height when driving home last night and it is actually just above my arm pit (for lack of a better way to explain) height or about 3" lower than my shoulder. When I rest my arm on the door with the window down, my arm goes UP a bit. So when I have spoken of shoulder height side tubes, that is what I mean.

As for head smacking dangers, everyone would be smart to take a close look at their roll bars. From looking at many pictures posted here, there, and everywhere, the occupants head WILL contact the side upright part of the roll bar which is not padded on any photos I have seen. Yes, the seat headrest should keep you from hitting the bar behind and/or over your head, but in any kind of side-rear impact or just sliding into a curb hard will throw your noggin sideways and backwards and quite possibly off the protection of the seat headrest. Something to think about.
(end EDIT)


I have some funny pictures of my car parked in the middle of a row of SUV's and 4x4 trucks that makes it look like a kiddie pedal car. I do get some strange looks from other drivers in the middle of our Alaskan winter.

Top quality foam padding on all tubes in the danger area is a smart move. Many of the online racer supply shops sell both the soft foam everyone used to use, and now the much firmer approved high density foam that is required by most, if not all, race event sanctioning bodies.

A lot of important safety things to consider when building our own cars. Especially if you think you may someday sell it...


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PostPosted: February 8, 2008, 10:56 pm 
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Joined: December 6, 2006, 10:49 pm
Posts: 50
Location: Buffalo, NY
First of all, I haven't been on here lately and it's nice to see new people and new content...to argue with! Just kidding. Kinda.

Your spine can stretch 6"? I have a hard time believing that, and I would really like to see some data. You have 26 vertebrae in your back. That makes for 27 spaces between bones... each gap opening .220". My wife just found an article suggesting that more than .25" of elongation would rupture the spinal cord. That would be .25" over the whole length.

If anyone was looking between the dash and the steering wheel, thier car got shorter rather than thier spine getting longer.

I definetly agree that having tubes in the region of your head is bad though, especially unpadded.

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PostPosted: February 9, 2008, 8:34 am 
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Posts: 5727
I don't know anything about the stretchy thingy, but I do know that oem seat belts have a folded flap of material with sticthing designed to rip during a crash. this absorbs some of the energy but allows the occupant to move that much further. Stretching neck or not, the rest of the body can do some terribly interesting things under load.

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PostPosted: May 6, 2008, 11:43 pm 
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Joined: April 16, 2008, 11:15 pm
Posts: 32
Location: Grand Rapids, MI currently Denver, CO
In what format did you draw up the car in 3d? I was wondering because my new ideas are somewhat the same and I like your front half - up to the seat backs, mine will be different in the back, as its going to be a BEC

If its in sketchup, 3ds, dxf, or many others than I would like to take a look at it.

Good job - keep up the good work

How are the side vents gonna work...just holes, or are they gonna be venturi or scoops? just wondering


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PostPosted: May 7, 2008, 12:32 am 
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The voice of reason
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Joined: January 10, 2008, 4:47 pm
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Location: Massachusetts
Don't want to abuse this thread. I looked a little bit and didn't see any data for how much you stretch your spine in an accident. I was told that in a driver school twenty or more years ago and took it at face value.

Roll bars without stiff padding are more dangerous then no roll bar. And I know you can hit things with your body in an accident that you wouldn't expect to be possible.

If the chassis bars are properly padded, do you think it's dangerous to have relatively high braces? I am thinking once padding is in place your better with more tubing then less.

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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: May 7, 2008, 5:45 am 
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mattlofbc wrote:
In what format did you draw up the car in 3d? I was wondering because my new ideas are somewhat the same and I like your front half - up to the seat backs, mine will be different in the back, as its going to be a BEC

If its in sketchup, 3ds, dxf, or many others than I would like to take a look at it.
You're either going to laugh or vomit when I tell you how that 3D image originated :D I had a list of the tubes in a spreadsheet (I was setting them up to go into Grape FEA) and I used Excel to export the file into a format I could pick up with some macros in POVray and rendered the chassis there. CAD it most certainly aint :) I've had a few stabs at drawing it in Sketchup, with mixed success. I did Sketchup a first attempt at my nosecone last night, mostly to prove to myself that the design (which is almost all single curvature) would work OK.
Image
Quote:
How are the side vents gonna work...just holes, or are they gonna be venturi or scoops? just wondering
In the design actually being built (as opposed to the little 1:10 model) there are three vents above and below the belt-line. They'll all be holes with slightly rolled in edges and black mesh behind them. My gut feeling is that the upper ones will be fairly useless for anything but looks. The lower ones however should be in a reasonably high pressure area where air builds up in front of the rear wheel arch and is trapped somewhat by the outwards slope of the side panel. I intend to duct from them into the engine bay. I've done a little CAD (Cardboard Aided Design :) ) to check clearances etc on the actual chassis. Real road testing will show if it works or not.
Image

Hope this is helpful,

Dominic


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 Post subject: head banging
PostPosted: May 7, 2008, 12:55 pm 
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Joined: January 31, 2008, 5:34 pm
Posts: 724
Location: SW Wes Consin
Here in the states the government decided on a standard impact beam for cars should be at 18". Unfortunately this standard doesn't cover trucks which until this summer ($4+ gas) many seemed to want. So once again we are screwed by a half measure.

Regarding banging one's head. My cockpit isn't wide enough to have my shoulder inside the frame rail (40") but I will have structure out there. My car is 62". I have thought about filling the space with foam as is done on some 7 type cars used in racing. Filing the space with steel seems unwise as steel doesn't crush very well, if at all. This won't do much to deal with truck bumpers though.


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PostPosted: July 2, 2008, 9:59 am 
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Posts: 317
Time for a sort-of update mostly because I wanted to show off all of the shiny new parts I collected from my machinist friend tonight. Spherical bearing top plates for my strut rear with integral camber adjustment, all custom made to suit. The tubes started out as heavy wall - about 5mm(0.2") thick - which were turned down to about half that. Then a support ring was welded in just below the top and the camber/bearing plate bolts up under that. The photo sequence tells the story.
ImageImage

ImageImage

Now that I have all the parts and can confirm final dimensions the strut tubes can be welded into the chassis which will allow the back 1/3 of the chassis to come together finally.

Anyway, not much of a build update but it's nice to show off shiny new parts :)

Dominic


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