LocostUSA.com

Hey Folks,
Nothing new here. I've been dreaming of building a car since I was...blah blah blah. I started! I took a while to post this because I've had a ton of questions over the last few weeks, but I don't want to be "that guy" who asks a question that's already been answered. I also don't want to be "that other guy" who starts a build and doesn't get to even go-cart it because I lost interest or got bogged down in the details. I've been able to work through most of my questions, but there are still a few lingering that I'm tracking down. I decided to post mostly to start documenting in case I can help anyone else by having my progress recorded. I'm sure I'll get some helpful hints along the way, and hopefully if someone will chime in if they see I'm headed for disaster and I don't see it coming.

I'm a mechanical engineer by trade, so I'm trying to nail down every detail I can before going to far to avoid having to re-do things. That's probably my first mistake because as well thought-out as the progress may be, it seems slooow. Long story short, I'm going the Ls1/T56 442e route with a rorty rear using 1-1/4 14ga tube. If anyone takes plagiarism as a compliment, prepare to be flattered. I'm copying ideas from wherever I can, and have gone through Phil and Rod's builds more than a few times each. I have a lot of the design done in Solidworks, but have been bogged down in a few details:

1. Roll cage - specifically how to incorporate it into the chassis. Anyone see anything wrong with replacing the K3 and K4 tubes with the main hoop and running it right down to the floor? Seems stiffer to me. I think I'm going to make my front hoop and connecting bars removable to get them outboard of the body. Otherwise I see an issue coming down the road with notching the scuttle for the, and I think it would complicate the windshield process. There's a slim chance I may straight-line race thins thing on an official track, so I'd hate to miss the opportunity on a technicality.

2. Rear end - I'm trying to nail down my track width. I'm looking at a complete 2016 mustang rear end because it seems cheap (to me - $500) and I know everything goes together - axles, spindles, diff, calibers, rotors, etc. My only concerns are that the one I'm looking at is a 3.15 ratio (72mph in 6th at 1500 rpm...too much?), and if the axles aren't quite the right length, what's involved in getting the right length?

3. Hood/Nose/scuttle - I want it to look "right", I don't have any interest in doing the fiberglass myself, but I want to know how it looks before I commit. I'm eyeing Jack's nose cone (by the way, thanks for the efforts in getting me set up here Jack!) I want to model it into my design so I can plan the hood/scuttle shapes, but I haven't been able to find any CAD of it, and I don't think any does or should exist publicly. I'm not even really sure what my question is on this one, so should I just bite the bullet, hope for the best and buy the nose to keep the forward momentum? I couldn't find any other options.

All opinions welcome, I appreciate constructive criticism. Thanks all!

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Before you start cutting metal, have you looked at the Car9? It was designed for V8-size donor parts, among other things, and has a much stronger chassis, and the cage is part of the basic design.

Howdy and Welcome!
And I second what TRX just said. Check out SeattleTom's Car9 build. He's even using a Chebby V8 like you plan to. Other'n that, keep on with it... Do a little something every day or so, just to stay in practice. It'll get there. Eventually...

JDK

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Just as a thought, you can use the offset of the rear rims to create a small amount of change in track width. That's what I did with mine, and it worked out well. You just have to find a vendor who offers a good range of sizes (most larger ones do) that will move the track in or out as needed.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Thanks for the pointers to Car9! I don't really do enough to promote it. There were several inspirations that started me to work on that project and one of them was the bunch of tubing behind the aft bulkhead the driver sits against. Then one day I saw a picture of Modernbeat's car where all that tubing had been cut off and the car was still a roller! It was a live axle build - but that did explain to me why I wasn't sure what that tubing was doing. Using that stuff to "support" the roll bar made even less sense to me. I think the roll bar is holding the rear tubing there, not the other way around.

In addition the material around the diff which the rear suspension connects to appears to sort of cantilever everything off the short lower tubes which are connected to that bottom cross tube in mid-span?

I wanted to better understand all this and I had a hunch some changes might help things. I used a free FEA analysis tool called "Grape" that works on tubing or truss type structures. It's a much simpler problem than other FEA approaches that involve dividing the material up into little triangles. This model is available in the chassis stiffness and Car9 threads, so yo can play with it. There is also a Locost model in the chassis stiffness thread.

First thing I did was raise the upper chassis rail a bit. Our modern motors tend to be a bit taller and this increased frame stiffness by %25. For safety and proper bracing the upper rail continues around the back of the car at the top of the trunk. More than one person on this board has been hit from behind at a traffic light and my third trip to a track in a formula car I put it backwards into a cement wall. The lower rail also continues around back but it kicks up a few inches. These changes allowed very sturdy bracing for the roll bar.

You did fix one of the little issues on a Locost frame. There is a little jog in the tubing from the engine compartment to the transmission tunnel by the driver's gas pedal foot. With the load we were using to test torsional stiffness, this little jog was lighting up with over 70 KSI in bending. I assume the floor should be strongly welded here and not riveted! In Car9 I kept the stresses to around 12-15 KSI for the same loads.

Another difference over what you are showing is that I chose to use longer trailing arms and a reverse wishbone for the lower control arm and a simple radius rod for the upper arm. This was traditional on many cars of that era and offered a lot of simplicity. The trailing arms feed the fore and aft load into the side of the frame, which is very strong in that direction. The lateral loads are fed into the bulkhead behind the driver, which is also easy to make enormously strong. Again you could remove the rear tubing and the car would be fine. I t just seems so much simpler to me. Later I found pictures of a Super Seven delivered from the factory with IRS. They also chose this arrangement.

One thing is Car9 doesn't have a front roll hoop. I'd like to see one worked in actually, it just wasn't on my first builder's list. Extreme car should be used with the roll cage arrangement because those tubes are just baseball bats aimed at the passenger's heads. In a real accident your spine can stretch a great deal. Several inches in the back and also in the neck. I'm not sure there are good answers here. They sell special padding for this which is quite hard, but even then it may be expected you are wearing a helmet - maybe it's helmet protection...

See if you can find a short oil pan your pushrod motor is probably shorter than a modern 4 cylinder and that's the difficult dimension to package. No problem with your choice but will mention that a small block Ford is much smaller. Think through your power situation a bit, these are light cars and you don't have a lot of traction. Being able to break the back end loose at over 100 MPH - that's serious business. I was thinking on that on my way to that cement wall - remember it pretty clearly and it was 40 years ago...

There's lots of great info on this site and plenty of people willing to hep and encourage you. Have fun! Any questions, just ask.

Here's a couple of pictures of Tom's build. He's all grown up now though.

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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.

Another pic which shows the frame better.

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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.

+1 on the Car9 design comments. Also having an ME background, I chose to go the Car9 route after pondering all the mods necessary to improve the classic 442-type chassis design to handle V8 power.
Well, to paraphrase Jimmy buffet: "Grown old, not up"
I really like the intrinsic shape of the Kinetic nose. To make it better fit my chasiss, I've widened and sectioned Jack's stock nose piece and when the weather warms up a bit will lengthen it 4" to blend with the engine setback. Minimal fiberglass work that (in my opinion) actually enhances the original shape. My scuttle will be aluminum sheet--a simple ruled surface.

Here's a current pic of my Car9 build. More info in my build log.

Have a great build whichever way you go. Lots of help available here on the forum.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."
Ultima Spyder, Northstar 4.0, Porsche G50/52

Thanks for all the info guys. I had read a few posts on the car9 design, but didn't really understand the application/design advantages at the time. With the understanding that it's geared towards a stiffer chassis and larger power plant, I'll give it a second look. Too late on "before you start cutting" though. I have the table built and laid out, and the lower members all cut and placed. I think I only have a little over an hour into cutting tubes though. One thing I can finally contribute is a great way to cut tubes. I have a ridgid miter saw that spins around 5500 rpm. I put a diablo steel demon blade on it, but the trick is that I have a 7-1/4" blade on a saw designed to run a 10" blade. That keeps the rpm of the saw matched to the blade, and while I can't cut through a wood 2x6, I can make it through a 2x2 thin walled tube in seconds with 1/4° accuracy. It leaves an almost machined surface with no bur. The saw has a clamp so the tubing is held securely, and I can trim 1/32" if I happen to leave it long. A little paraffin helps the teeth last longer, but isn't totally necessary. Back to the car9 thoughts - my only other concern is that it seems to be a lot of round tube. I don't currently have a way of notching and I have no round tube. I do have an almost unlimited supply of 12' long 1-1/4 x 14ga tubes leftover from a job my shop did years ago...hundreds of them. I'll price out the round steel and notcher and see how things look.

Regarding the engine choice, I didn't see enough of a size difference to warrant going towards a ford small block. Also, I have the LS1, I don't have a small block ford so 90% of the decision is made right there.

Back to reading the forum...targeting on car9 this time.

The Car9 chassis can be built using mostly square tube instead of round. IIRC, Marcus (aka Horizonjob) has a square tube version available online.

I used round tube for the experience, but square tube would definitely make for a faster build with a likely cost advantage.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."
Ultima Spyder, Northstar 4.0, Porsche G50/52

Using tubing and a motor you already have makes plenty of sense. I'm not too opinionated about these things. I'd suggest getting a little lighter material for some of the frame, but the main rails and things the suspension tabs weld onto and a cross tube in the dash and behind the drivers back can be the strong stuff. Diagonals and some other stuff can be lighter.

With where you are at you can still go either way, the tubing pieces in the floor can be mostly re-used and it seems you have a good supply. We're going to encourage you any way you decide to go, no problem. The basic frame goes together pretty quickly. Then the details seem to multiply a bit.

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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 did a bit of reading on the car9 designs. I really like a lot of the features of the car9, mainly the integrated roll cage, but I think I'll stick to the more traditional route. It's been done so many times that if I run into an issue along the way, and answer is much more likely to be just a google away. I also prefer the looks/proportions I'm headed towards now.

On a different note, I thought I made some headway with a mustang rear dropout assembly, but the mounting face-to-face is about 67.5" and without some serious offset, the tires will be sticking way out there. The axles are a 34 spline so I'm not even sure what other vehicles use that, or if their axles would be any shorter, and custom axles are out of the budget. I may revert back to my original idea of an '06 explorer rear diff with a lot more axle choices. I was looking forward to having a whole bunch of parts that were actually designed to work together.

The stock Mustang wheels already have a lot of offset; rather than measuring the axle, find a Mustang and measure inside-to-inside and outside-to-outside sidewalls. A couple of yardsticks and a helper or bungee cord will make things a lot easier.

The Mustang axle has been used plenty of times; Lonnie-S's build viewtopic.php?f=35&t=5886 is one of the more-detailed Mustang donor builds, and shouldn't take you long to zip through, it's only 132 pages long...

Can anyone tell me what's common for space between the inside of the wheels to the outside of the frame? The rear track width is driving me nuts because I haven't been able to find a good source for axle dimensions and I want to know what track width a set of axles will put me at before I buy them. I did find the Ford 8.8 IRS Components V1.0 writeup - is there a newer version of that that covers additional vehicles? I beleive Rod's build used a couple drivers side explorer axles, but I can't find the lengths listed on them. When my frame is 46" wide, and the wheel mounting surfaces are coming out to around 63-1/2" it seems to me that I'm going to need nearly 3.5" of offset in my wheels to get them within 1-1.5" of the frame. Am I missing something, or (sorry to be lazy) can someone just tell me what axles to look for that will work with my 31 spline rear end? I'm looking to use 17x9 rims in the rear.

TRX, I understand the mustang has been used plenty, but the one I was specifically mentioning was a 2015-18 rear setup. I'm not comfortable walking up to a strangers car and crawling under it. Maybe I can find one at a dealership. Not a ton of info on them out there, and there are some additional links on the rear suspension that I'm not familiar with and don't want to get crazy into suspension design. Very different from Lonnie-S's build...I tried to skim through it, but didn't have the attention span to get past 20 pages or so.

If you're going with an IRS, I can't be of much help as I have a live, 7.5" Mustang rear axle from a 1994. I can't tell you which IRS rear axles will work best. Is that the question you want answered?



Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Hey Lonnie,
No direct question towards you, I was just responding to someone who mentioned I should look at your build for mustang references, but I agree, your live axle is very different from what I'm looking to do. Do you get a notification when someone mentioned your name in a post? That was a quick reply.

I'm looking to find out:

Common clearance between inside of rear tires and outside of frame
Any compilation of information for ford 8.8 IRS half shafts by vehicle (lengths, spline count primarily)
Or if someone knows what half shafts will work for my situation, please advise. (2008 ford explorer 31 spline rear carrier, 9" wide wheels, markviii uprights and spindles)

On the plus side, I picked up my uprights last night form a local used parts place - they look almost brand new, and someone recently did the bearings and it looks like hubs as well!