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Do you plan to use a tube notcher? if not. i know of a way to get really good templates for every one of you pipe joints. i plan to you paper template for all my tube ends... well all of them that are more than a simple angle cut.

The trick is in SW make a copy of the weldment profiles you intend to use. open the weldment profile copy and cut a slit though one corner. make this slit like .001 wide. Also you need to make the wall thickness of your tube only .001 or less otherwise it will lie to you terribly. At this point id also probably make a copy of your main file. then in the copy replace the weldment profiles with the new cut and thin versions. Then for each tube you select one of the edges of the cut profile along the cut surface. Go to the sheet metal menu and select "Bends" and hit OK. now unsuppress the flat pattern feature and what is displayed can be printed 1:1 scale and wrapped around your tube for custom notching.

If i didn't explain that very well or if you like i can find/ make screen shots of the process.

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Anyone who has never made a mistake has never tried anything new. ~Einstein

Build log http://locostusa.com/forums/viewtopic.php?f=18&t=15177

I've known for a while that Solidworks could print flat patterns of tube cuts but didn't know how to do it, I've been planning on trying that. But first I will look into a tube notcher as it should make most of them much easier.

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im CAD hat's passt

Time seems to be flying all around me...

I'm still making very slow progress on the chassis design but it's nearing completion. I don't yet have provisions to mount all manner of small things yet but that will come in time, for now I'm focused more on the bigger picture while trying to leave room to account for the small later.

I'm on my 4th design of the chassis and I think I'm done with "restarts" at this point; all major issues have been solved (in theory at least) and it's all down to details now. The major shape of the chassis has not changed but a number of smaller things have. I took a break for quite some time while I tried to figure out the "interior" tubes...tunnel, cockpit bracing, etc... but last night I make some breakthroughs that should push me onward from here.

I've been mulling over suspension a lot recently, not so much on shocks and springs but over the uprights, bushings, ball joints, hubs and the like. Every time I think I can start to design something I get mired in the details of how to attach ball joints, what components to use, rod ends vs. poly bushings, off-the-shelf vs. custom, depths, thicknesses, strength....then I have to get back to my job so that all gets put on hold. But I've made a lot of decisions and will very shortly be moving forward.

In the next few days I'll post up some more chassis work, I'm excited about where I'm at with it. After that's largely complete I will be moving on to suspension components which, for me, is very exciting.

In other (both related and unrelated) news though my donor/daily has been a bit of a nuisance recently. I was having a knock issue that turned out to be injector seals, although I had to try everything in the book to figure it out. A month long trip down that rabbit hole left me worn out on troubleshooting cars so the next problem was easy to find...my turbo was going out. I started billowing smoke about a week after getting the injector seals in. I managed to tune the issue out (literally, made some tune adjustments) but it's a known problem and bandaids only do so much and for so long so I found a replacement, a garrett GT3071 with a mazdaspeed exhaust flange from ATP (known as drop-in turbos) for a good deal. I've spent the past month or so tuning and have a good 350/370 on tap with a flick of the loud pedal now.

So that should be fun in a car half the weight. And right wheel drive.

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im CAD hat's passt

As promised, a few screen shots of the current design. Main tubes are 1.75" .095, smaller round tubes are 1" .065, square floor tubes are standard locost 1x1 and suspension pickups are 1.25x2" .125.

Right now I still need a few more parts....a cross member to mount the front suspension, some bracing for the scuttle, harness bars in the roll bars. I'll be running an FEA soon (if my computer can handle it...which is questionable) to prove it out theoretically and in the mean time I'll work on suspension arms. I have most of the suspension hardware selected, need to dimension the front and rear hubs.

Always open to criticism.

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im CAD hat's passt

Despite my previous declaration of being done with the major design work....I don't think I am. It looks like I'll be doing at least one more iteration, as much as I want to be done.

Yesterday I started working on control arms and they just aren't coming together like I wanted them to. For the rears I'll pretty much have to deal with whatever space I have, there's nothing I can really change back there. The fronts seem too short and there are too many things in the way for me to feel comfortable with them. I really need to fiddle with some shapes, move the front pickups closer together (currently 14" center-center), and get a handle on everything. I'd like to narrow up the whole front end but doing much narrowing results in needing a new steering rack, which is not favorable. I also don't want to shorten the miata rack if I can avoid it.

So...much to come. I've got a head of steam for it now though so I hope to work quickly. I also may try out SW2014, see how that holds up.

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im CAD hat's passt

I've resigned myself to not provide many updates here while I really have nothing to show and I've done a pretty good job of it I think, but now I feel like posting just to keep it up to date.

I'm on rev 6 of the chassis design and have made some major changes, some for manufacturability and others for strength/weight/safety.

-Besides 6 main constant-radius curves the tubes are all straight. This has allowed me to slightly increase the main tube diameter (2" instead of 1.75") while decreasing wall thickness (.065" instead of .095") which saves 20% on tube weight while increasing torsional stiffness. This also reduces my need for expensive tools in the forthcoming build.

-Front suspension has its own dedicated box which will connect to the upper and lower main rails and provides better steering rack mounting as well

-Cockpit has been slightly widened to accommodate the seats I want to use

-I've decided to use all the hubs from my donor car and will modify the front macstrut knuckles to convert to double wishbone use in the rear. The reason for this is the modern control system which uses ABS sensors to run the speedometer....and of course the sensors mount inside the knuckles.


I didn't mention it at the time but my daily/donor's turbo let go at 90k miles (a long life for it admittedly) so I replaced it with a bit of a larger one. The once k04-powered 07 speed3 now has an ATP/Garrett GT3071 and is making around 350/375 at the wheels. It still needs a bit of fine tuning but the car is running quite well and is very fun to drive, I can't wait to get this build actually going.

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im CAD hat's passt

Great donor!! There's a lot going on in that chassis, glad Im not the one building it. Look forward to your progress.

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30 years old, not sure what I want to be when I grow up…

the chassis is now much simpler, at least in terms of removing the multitude of bends. I haven't yet figured out the scuttle position or height or "interior" tubes but that should largely be functional placement without too much additional thought really.

I haven't run any analysis on the chassis yet but because I'm doing it in solidworks I should be able to do a simple torsion test. Having looked at a multitude of chassis designs and read a couple books on the subject I'm confident that it is plenty stiff as-is (or as will-be), especially looking in comparison to the standard locost chassis.

Regarding the speed3 as a donor, I'm mixed on that decision. I know this car and this engine better than any other and, despite its flaws, it is an absolute power house. The torque delivery is insane and the transmission is bullet proof with a built in LSD as stock.

That said it really can be a finicky beast. When it runs well it's magical; when it doesn't it's a massive headache. Due to the complexity of the engine controls I'm limited to the stock ECU and I have to use the stock gauge cluster and key as well, which means using the stock ignition. All of this is not necessarily an issue as long as I design for it, but it is definitely not conducive to a simple and clean build.

But that torque delivery.....

Anyway I'm once again rethinking my front end design. My idea and reality are clashing a bit and it's tricky to reconcile but I'm definitely getting there. This is where having computerized modeling really wins out in the ability to visualize and analyze a design before every buying or cutting a tube.

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im CAD hat's passt

Oh dear god please tell me this project is still active... besides the powerplant its exactly what i had in mind for a chassis except you actually know how to engineer it properly. You have to update us on this, please, im begging

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What could have been a low budget V8 midi has planned itself into something pricier...of course
My Build

Your main tubes (2"x0.065") have a d/t ratio of 30. This may affect the compression capacity of these tubes. Does your analysis program consider this?

I guess an update is in order given the time since the last one, huh?

I don't have much done since the last update unfortunately, my brain stalled for a while and I got busy with life and a new toy in the garage. But I for sure haven't forgotten this or given up on it, just delayed things a bit.

After my last iteration I realized that the front end needed to be re-designed again. The problem keeps coming back to structural rigidity vs. desired dimensions vs. required space. In this last instance I had the front suspension box being substantially smaller than the chassis section it was sitting in meaning long members to join the box to the upper rails of the chassis which I'd like to avoid, but that doesn't then leave me with enough space for things like a radiator (of which I'll need a massive one to cool this beast). While mulling that over I realized that using the Miata steering rack like I wanted to also meant a not-so-subtle array of u-joints and shafts to actually get to the rack which was to be mounted on the front of the suspension box led me to rethink this whole area.

So I went back to the proverbial drawing board with it and decided I could just use the speed3 rack and column to make it all nice and simple, but that changes other things like the width of the suspension box, nose width, and ultimately the length and angle of the a-arms if I want to keep the same track width, which I currently do.

While coming to those realizations I stepped away from Solidworks for a couple days, which then turned into weeks and months. But recently I've been coming back to it, and while I don't remember what any of my original dimensions were I have all the old models which I've been pulling up again and examining for other design flaws to work out. And I've found many.

I don't like how the mid rail joins to the engine box. Or the front for that matter. I plan to remedy this by connecting directly to the upper engine tube and lower front suspension tube, but this causes a problem with interior width and overall ID. Plus to do it properly I can't really modify a previous iteration as it would involve basically wiping out everything attached to those rails...which is the entire chassis.

Seeing a couple responses in here is motivating though so I'm going to get back into CAD with this thing and see what I can do. I want to have a full CAD model of the car before starting to build it, but that may be unrealistic. We'll see. I happen to know a guy who has a parts car, and I have an engine torn apart in my garage so it may come about faster than I anticipate.

A closing note to these thoughts: The more I work on this and mull over the consequences of all design decisions the more I hold the Ar-i-el engineers in high regard. As much as I want to shy away from cloning the atomic one it is difficult to do because what they designed is perfectly simple as far as exo cars go and replicating its simplicity in a different suit is harder than I imagined.

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im CAD hat's passt

Just a tip but the stock 2 generation ford taurus radiator fan flows something like 1250CFM. im not sure if there is a way to calculate how much flow someone would require, but its an easy to find and inexpensive fan that performs like a high peformance aftermarket model.

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What could have been a low budget V8 midi has planned itself into something pricier...of course
My Build

It shouldn't be a big issue. Cooling is more a problem in slow traffic or even just idling. The heat comes from the power you use, how long can you use power in a car like this without getting a good supply of cooling air? Once you're going more then 50 MPH, you have plenty of cooling air.

The problem with these curved tube builds is that the tubes are arranged to be pretty, not to be structure, that makes things harder.

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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!"
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The problem comes down to size though, and I haven't found anything yet that really meets the dimensions I want to use.

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im CAD hat's passt

I'm sure it's less of an issue in reality than it is in my mind but I've seen plenty of instances where running 215* temps or more is expected when pushing the engine even in open air running. So I need to account for that. Granted this will be in a much lighter vehicle but I'd rather not risk it if I can avoid it.

Most of the curved tubes are being done away with, I just don't have a model I'm happy with to show it all yet. Aesthetically they look good but I've always known that fabrication will be an issue...and a lot of the bends are taking up space that I want to use.

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im CAD hat's passt