Spartan v8

[sbcrx007]

Hello there - first of all, my name is Jesse, I've been surfing this forum for a while but never posted. I've been designing off/on for a few months now my own home built exo car. A little different then some other cars here, but still very exoskeleton. I'm a 26 year old from Ohio, so bear with me here.. I have a mechanical engineering degree, but not so much experience, and no FEA software.

I'll put a pic up later tonight, but wanted to get first impressions. Here's what I'm designing:

Steel space frame chassis, 1" square tubing

Front engine rear drive layout (a first here as far as I can tell, hopefully that doesn't make it the devil =)

Roughly 98" wheelbase

Built from donor C4 Corvette (I'm cheating here, using the suspension A-arms)

LT1, LS1, or LS2 powered, whatever I happen to be able to afford

T56 5 spd or ZF 6 speed, depending on my donor and what I'm able to get as a motor/tranny combo

Target weight, 1600 lbs curb weight + me

Target weight distribution, 50/50

Target power/weight is then 1:5.33 to 4.00 depending on motor, assuming I can meet the target weight


Without meaning to, I took some design cues from the Atom, SLR, and X-bow, but otherwise it turned out like it did from design considerations, much less so than aesthetics. One major concern was tube bending - I don't reckon I'll be able to do it myself, so no bent tubes, all straight! This will require a few more welds, and ends up with a very straight edged shape, but it grows on you.

I'll get pics up tonight, I'm very interested in some constructive criticism =)

Thanks!

Jesse Busby

[mkim1]

Sound great, Jesse!

If you can somehow package T-5/T56 with LS1/LS2 engine in a rear-engine exocar setup, you'll be a trailblazer, besting Factory Five GTM! Look forward to seeing your pics! : )

[Karlo]

Welcome Jesse

[CMC#5]

That sounds like a lot of fun Jesse. I would suggest you rethink your "no bent tubes" strategy though. You might end up making quite a few compromises to avoid something that is really cheap and straightforward. Since you probably dont want to buy a bender, once you have dimensions, a local race car roll cage shop can bend you some tubes on the cheap.

Once upon a time, we bent tubes for off road cars by: a) make a jig of the inside radius using wood, b) fill the tube with sand, c) heat the tube with a torch and pull it against the jig :) keep plenty of water handy!

[sbcrx007]

Thanks guys -

mkim1, I'd use the fwd setup from a newer impala ss or monte carlo ss, whichever was the one with the lt1 fwd setup... although I don't recall if manual was an option.. In any case, I'd still prefer the front engine/rear drive route...

cmc#5, I've thought about it, and I'm not opposed to trying something like that method, but it just doesn't seem to be worth it.. I'd definitely have a cage shop do the bends for me if I were to do any. I don't think I could do it accurately enough, nor avoid kinks. More than that, its just too much work! I like how things turned out with lots of angles, see what you think when I get back to my pc and post a solidworks screenshot or two.

I also just finished a balsa model of the frame, that's been fun and has spotlighted some of the construction problems I'll run into..

[mkim1]

Yeah, LT1 from Impala SS & Monte Carlo SS would be cheap to get, especially if Jesse wants an auto. trans., but maybe he can get the trans. separately and still get it reasonably cheap. Based on his post, it seems like he wants to do RR engine/ RR drive. Let's see what his design looks like!

[mkim1]

Oh, my bad, Jesse! I misread the post. O.K. you want FR drive, RR drive. A superlight Cobra! Nice! : )

[sbcrx007]

Here is a screen shot from solidworks. Please note that the windshield/windscreen is hopeless and constantly in flux...

[sbcrx007]

Here's a shot of the balsa model

[sbcrx007]

Screenshots of the frame

[mkim1]

Looking good! One small suggestion: Adding a couple more members around engine bay / front suspension area might triangulate the front end and strengthen it. Just my 2 cents. Good luck!!!

[sbcrx007]

Ah, yeah, I forgot to mention that =)

As I don't know exactly which motor I'm going with (and don't know the exact motor mounting points, or the exact suspension mounting points) I can't yet triangulate that area how I want to. I want to make sure I make joints at each suspension mounting point and engine mount.

Good point though just the same. Torsionally, my main concern is the torque thru the cockpit section as there isn't much more triangulation that can be done, without making the sides thicker or multilayered.

[sbcrx007]

Here is a current shot.. As you've probably seen, I haven't figured out how I want the cowl and windscreen to look...

[sbcrx007]

Here is an older design that I still like.. It started getting too much like the x-bow however, especially in orange. It looked good at certain angles, but other angles not so. Too much flat space.

[Karlo]

Looks like you have all the right tools to get started!!!

[cheapracer]

Personally I would go for a larger section tube to get away from the spagetti look. Your balsa wood mock up shows the larger tube looks better/tougher IMO. (besides the safety margin).

I would use 40 to 50 mm, at least 30mm at the minimum.

Have a look at this thread for another V8 front engined special.

http://forums.autosport.com/showthread.php?s=&threadid=105210&perpage=40&display=&pagenumber=1

[sbcrx007]

...but I like spaghetti...

Seriously though, yours is looking pretty good.. Definitely different, I like.

A big part of why I went thin is weight - my chassis weighs in at 168 lbs curently, at least per solidworks. That said, I do like the look of the bigger tubing better, definitely a thought..

[cheapracer]

Mate at 200 lbs with a V8 unit your not going to notice a thing!

Maybe check out some Australian Locost forums because our rules there dictate different torsional levels for 4, 6 and 8 cylinder engines so you might talk to some people how they go about getting the extra rigidity into theirs.

I would consider running another seperate sill tube further out or inside and making that area triangulated.



....../
..../.l
../...l
/___l looking from the front at the righthand side, pretty bad keyboard drawing but

hope you get it.

It will have to do cause on off to Oz, sunshine and beach (and topless babes!) here I come....


.

[cheapracer]

...and I'm suprised you got The Michelin Man to pose for your car, Wow you must know people!

[sbcrx007]

I like the idea of the triangular cross section in each of the cockpit sides, I think I'll try mocking that up tonight.. I'm not real partial to how I think its going to look, but it would certainly stiffen things up! Maybe flip that triangle up side down, have the point at the bottom; the car might fair a bit better in a side impact that way, considering the sides are only 16" high from center of bottom tube to center of top tube..

And the Michelin man eh? My human mockup does leave a bit to be desired.. I never did get around to giving him arms, oh well.. He's to my dimensions, so at least I can see where my head is at, see what I can see, and see where my legs and feet end up.

I was really hoping to keep the chassis down around 150 lbs, cut weight anywhere I can to keep her weight in Exo car territory. The damn motor weighs 500-550 lbs, so anything I can lighten up is great.

@Karlo - All the right tools? That's a laugh, I don't even have a Mig or a chop saw yet! =)

[cheapracer]

I .. He's to my dimensions,

I was really hoping to keep the chassis down around 150 lbs, cut weight anywhere I can to keep her weight in Exo car territory. The damn motor weighs 500-550 lbs, so anything I can lighten up is great.

@Karlo - All the right tools? That's a laugh, I don't even have a Mig or a chop saw yet! =)

My God man, theres surgery available!

Go for a GMV6 with blower, I'm starting to sound like a broken record on that one! It's going to save you 100lbs and is shorter in the chassis, leaves more room for radiator etc and better car balance.

I think Karlo meant your 3D tools?

I'm at my first stopover, HK tomorrow then Oz on Friday. Beating around the bush but was bloody cheap tickets.

[cheapracer]

http://www.exocars.net/showthread.php?t=297

Mate have a gig at that frame for some side triangulation ideas...

[sbcrx007]

Lol, what surgery is that, weight loss surgery? Well,the model is my vertical dimensions anyway, how about that? hahaha

My ideal motor would be the ls1 or ls2, even over the sc v6 for a few reasons..
first, the horsepower is just there, no boost required.
2nd, less complexity = more reliability.
3rd, its tried and trued - plug it in and go, no massive retune necessary.
4th, IF I ever wanted/needed more power, I could use forced induction with the V8.
5th, the power to weight for the motor is excellent (at least for an american motor!), and adding a sc to the V6 will add more weight that you think by the time you add all the add'l plumbing and intercooler, etc..
6th, a "stock" or close to it LS motor will run for well over 100,000 miles and still lay down full hp, no sc rebuilds or burnt pistons
7th, Given that this will be a sunny day car/track day car/autocross/drag race/road trip car, a lot of compromises are necessary. The inherent reliability is a huge point for me.
Yes, a 4 cylinder honda motor or whatever would motor the car along just find, quickly even, with excellent reliabilty, but I'm really looking forward to having a car with phenominal power to weight.

I've got an older mazda rx7 with a motor swap that has about a 1:10 power to weight, its quick and fun to drive, but feels slow anyway. Imagining a power to weight that is double that just makes me smile.


That link with the side triangulation is more what I was thinking earlier, and very nicely done in that case.

Is anyone here any good with some FEA software? I'd be grateful to find out what the ft-lbs/degree is from front to rear, I understand it should be double or triple the car's weight, as a basic rule of thumb...

[FIAROADSTER]

one interpretation, frame only
http://www.rmotorsport.info/Roadster.html

[sbcrx007]

As soon as I get some time I'll try changing the cockpit sides to have a triangular cross section to see how it looks, and how to blend it with the rest of the car.

Another thought was to change them from being exactly vertical walls to leaning outwards from the center... Wouldn't that stiffen that area somewhat?

Lacking decent FEA software is hurting me here, and all the free ones I tried were limited to only a few nodes. I'd really like to use cosmos, solidwork's FEA, but I just have a student copy and its not included. Anyone with access to Cosmos that might be able to take a look at my frame?

Thanks!

[sbcrx007]

Was also just checking out JonW's car, that X shaped roll cage is almost exactly what I was considering adding, along with a windshield frame. This would really stiffen up the cockpit area of the car. I really didn't want a full windshield though, wanted to go the windscreen route if anything.
I suppose I could make the windshield glass removable for racing or whatever, leave it in for longer drives...

Opinions?

[sbcrx007]

A first attempt... I think I need a steeper windshield, more roof area.

Not sure I like the idea of the overhead roll bars though, seems to take away a lot from the roadster feel of it..

Thoughts?

[sbcrx007]

Played with the X shaped roll cage a bit more, but I can't get it to look right on this car..

Still working on whether or not to add more to the cockpit sides.. The problem there is that the body is wide enough already, I don't want to go wider, yet I'm not really willing to cut into the interior space either. I'm shooting for the somewhat strange combination of track day/cross country/sunday drive car...

When and if I can get a FEA done for torsional stiffness, then I'll know if it needs anything added to stiffen it up.



What I'm really going to need is much more detailed info on the C4 Vette's suspension that I'll be borrowing.. Until I have that, the front and rear sections of the frame don't really have a set width. I almost need a corvette in good shape to put up a rack and take measurements on, unless some detailed drawings are available..

[sbcrx007]

Made some progress on how I want the cowl and windscreens to be shaped... Also added a couple tubes that should stiffen the engine bay to cockpit area, as well as improving the look of the transition (I like it anyway).

Enjoy, opinions welcome as always!

[sbcrx007]

Just added in some paneling, I'm liking how the cowl and windshield is turning out this time round..

Soon as school starts back up here, I'm going to see if I can use their lab to do an FEA on the frame, I'm pretty sure they've got Cosmo there..

[sbcrx007]

just the latest..

[cheapracer]

Well you don't see many of those parked out front of a hambuger shop on Main St on a Saturday night!!

[Gage]

LoL =0)

[sbcrx007]

Indeed, thanks! Working on FEA stuff still.. I'm at a calculated 6241 ft-lbs/deg, but I'd really like to do away with a few tubes, I think 4500-5000 range would be plenty. Here's a screenshot of the stress plot and displacement plot from earlier today..

[Karlo]

That is an amazing program!!

[sbcrx007]

I'm using Solidworks and Cosmoworks 2008. Well, well, wellllllll out of my price range, but my university happens to have it on their computers. =)

Jesse

[cheapracer]

Phhlllltttt, 50 cents on the streets here for those programs!

[sbcrx007]

Well, no real news.. Got laid off of work and am taking some time to reflect on whats next. I should be working again soon, one way or another, then I'll start buying my vette suspension pieces. Then I can FINALLY get the front and rear suspension set up properly in the model, and get all the associated brackets and mounts designed..

Little by little...

Oh and the latest on torsional stiffness was up over 10,000 ft-lbs/deg.... that should be enough!

[sbcrx007]

Been working on designing the front suspension... here's a quick updated pic :old:

[Karlo]

Did you find work? Project like this do not go far without $$$

[sbcrx007]

Eh, not yet. On the plus side, I've got more time to work on the design 8-)

[sbcrx007]

Another update.. Front suspension is pretty well set, still modeling rear components :old:

[Karlo]

www.spartanv8.com

[sbcrx007]

thanks Karlo, that's my project! =)

I couldn't keep up with all the forums, found it easier to just update my website..

[sbcrx007]

Here's a teaser shot...

Front and rear suspension completely modeled, just about ready to start building. Have purchased and been working on my engine, an all aluminum 5.3 liter V8. Now just need the transmission, then model that, add to the main model, then ready to actually start!

[sbcrx007]

still playing.. work really gets in the way of getting anything done now!

[Karlo]

I like the green fenders.

[cheapracer]

jesse, cant get to your spartan web so the odd snippet here or Locost is appreciated, thanks.

[sbcrx007]

Really? Because of filters in China?

Quick update:

Wire harness is ongoing... always another wire to add, solder, heat shrink, etc..
Motor... is awaiting assembly, it's been cold out in the garage..
Trans... picked a T56 up last weekend! Unknown condition though.. we'll see..

Jesse

[cheapracer]

Yeah I guess the nuke rocket building plans on your site did it.

I still say your using the wrong triggers by the way.

[sbcrx007]

Yeah, well that's just like, your opinion, man..

(Big Lebowski) :)

[cheapracer]

Yeah. Well, the Dude abides.

[LS-Fbomb]

Nice!

[Gas]

Great Work so far! I like your donor car. I am a big guy so building a car around a Corvette makes a lot more sense to me. I want space for at least 2 big Americans, without feeling cramped. C4 Corvettes are one of the best automotive component deals out there! Especially if they are damaged! I bought my wife one for her birthday. It is now pretty much her car, because I can barely fit in it. C5 has a lot more room. The C6 gets small again (guess they figured Americans are shrinking).