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Hello,
I have been lurking here for the past few years and have been thinking about building a locost for track and minimal street use. Every time I sit in a seven I start wondering about impact protection, especially the door bars. 1" 16g square tube positioned as a bending load inches from my body is not as confidence inspiring the door bars I am used to on a caged production car. Does anyone else share this concern? I did a really quick mock up of improved impact protection and converting critical tubes to 1.5" round tube. A lot of the details aren't resolved at all, especially the back end. It would also be impossible to do traditional body panels on the sides. Anyone else share this concern? If so, how did you address the issue?

Welcome.
It can be done, but as always, once you change something, other changes will follow. I built a full cage, and the rear section, from 1.5 x 0.095 DOM. But many changes needed to be made to accommodate all that. I left out the windshield, fabbed my own scuttle and made all the body panels removable (lots of tabs with nut plates). It's a blank canvas; build it the way you want it and feel good about it.

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Martin


My build log:
viewtopic.php?f=35&t=14520&start=0
My build video:
https://vimeo.com/143524140 password "matovid"

You cause for concern is real. One other way to address it would be to build a full bodied car like Jack's "Lalo". This would allow an extra 16-18 inches of cross section and allow a greater cushion between the outermost side bars and the soft, squishy cargo. Jacks thread (especially page 5) will show better what I'm talking about. http://www.locostusa.com/forums/viewtopic.php?f=23&t=8984&start=60

Good luck!

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Mike - Read my story at http://twinlakesseven.blogspot.com/

Sevenesques are inherently dangerous, but I think that you're on the right track. External side impact bars are butt ugly, so incorporating some more side protection within the structure makes a lot of sense. Yours will read a bit wider than traditional, but a bit of judicious styling choices could make that a plus rather than a minus. I have a friend whose wife refuses to ride in his Locost, but yours might just make the difference.

While my project is not based on a Seven-style replica, I was concerned about the same issue. I used an extra horizontal tube, triangulated in each direction (not finished in the photo) this adds considerable stiffness, especially for the structurally weaker cabin area, while providing side impact protection. In my case, I am using the side bars as locators for my bodywork and it works a treat.

Here is one that I really like, as it allows the use of side pods for impact, as well as space for ancillaries. I think the shape works well

I did have side impact bars on mine but ended up removing them to save weight as the car is basically just an autocross car.

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2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558

Love the fat, no-nonsense stance!

I just consider the Locost to be a 4wheel motorbike: Crashing is going to hurt.

If I were to build a trackday car (not necessarily a Locost), I would keep the main chassis in tight like a Locost, but add Nascar style door bars with full cage. You just have to resist the temptation to move the seats outboard to make more room (better weight dist. as well). All that DOM steel adds weight, but it will sure come in handy if some 4000lb AMG decides to punt you on a trackday.

Keep in mind that the loads the doorbars see in an impact need to go somewhere. There have been a few cases where the "safe" door bars were tied into weak areas; causing the ends of the strong door bars to enter the occupant area (and possibly the occupants).

Also keep in mind that full cage on the street can put your head pretty close to the cage. Most designs are meant to be used with a helmet (and padding), and would brain you without one. I'd keep seating low with lots of head room to cage.

Cheers.

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Build log: viewtopic.php?t=9291

I kind of liked the simplicity of how cheapracer was going about it with his 'plus sized' 7: http://locostusa.com/forums/viewtopic.php?f=35&t=15967

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

For my Car9 design I read the regulations for roll cages and tried to put that into the frame.

In your design you are trying to build out the tubes around the cockpit, that is stronger is some ways and weaker in others. I think you are better off with that bend happening at the bottom of the dash where you can have a tube across the car to keep that part strong where the angle changes in the top rail. You can put nerf bars on the sides of the cockpit and make sure they are connected to places in the frame with cross tubes so they are strong.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.

I like the look of the sidepods with body panels but I would prefer if the driver compartment was actually larger so that limbs weren't so close to the chassis. I am looking at the way the bauer catfish chassis is wide in the drivers compartment and then narrows to accommodate the suspension. If you aren't familiar with the catfsh: http://bauerltd.com/wp-content/uploads/ ... out-12.jpg


I think the next step is to define all of the suspension points, engine mounting, and driver position details and then design the chassis around them.

The defining aspect with these vehicles, and in particular building your own chassis, is that you can build the car to suit your dimensions and your own requirements for safety (or lack there of) so it is tailored to your needs. The downside is that if you alter the plans of "the Book chassis" for example, you can expect all sorts of changes, such as calculating suspension pickup points, as the chassis geometry has most likely effectively changed.

Just a follow-up from what Marcus said. On my chassis (as per photo further up) I have a cavity either side of the cockpit. Once the sides are sealed I will fill that cavity with 2-part polyurethane expanding foam (not the cheap stuff). It has excellent impact absorbtion qualities and provides fantastic rigidity-vs-weight properties. i will use it at the front end near the hood too. Increases stiffness, provides impact protection

I built an impact attenuator for an FSAE car using 2 lbs/cubic foot polyurethane foam in an aluminum box made from 0.020" sheet. At the time we didn't have to test the entire attenuator - testing a small sample of the material and extrapolating it was acceptable. A few years later that rule changed and testing was mandatory. The attenuator I built was the first one to get tested and it failed miserably. Even thought it was the lightest foam available, it was closer to concrete than foam during an impact. I forget what the exact G numbers were but it was much higher than what was considered acceptable.

The solution was to cut away most of the sides so the foam had room to deform - something to keep in mind if you're trying your own.

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-Andrew
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