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Hoping to get this thing on some scales next week and see where I am at. I am trying to determine where to put a fuel cell. I am thinking 5 gallons and towards the front, but the area in front of the driver's rear wheel looks wide open.... Decisions

Get the seats mounted in there, the steering wheel mounted and then have my brother push me around.

I've never built a chassis before but I've detailed a few bridges over the years. I've also done countless vectored load diagrams. All with pencil & paper, so that program shown on the previous page sure looked interesting!

Connections offset from the node is fairly common on certain tube-truss bridge designs. But they are usually within the width of the members being joined. If the force vectors don't zero at the node it has the potential for failure. That being said, I see two problem areas: the top tubes that are bent outwards ruin the truss concept because it's not a single plane. I think a computer fea analysis would show that point as a place for failure. The second place is the radiused tubes at front, they will end up being in shear, with some strange moment forces as well.
Without number crunching tho, it's entirely possible for everything to still be within safety tolerances.
Enjoying your build thread. Keep up the good (and inspirational) work!

Thanks Mach68!

I have some pictures of the front suspension and the rear suspension. I like how the front is working and I am redoing the rear.





Here is the rear my cage guy did:




And this is similar to what I am redoing it to:

Rolling chassis!!!

Looking at the design even with it's other limitations, I would suggest you add where the red lines are both sides or for you where the blue lines are - you have only the bending strength of the tubes holding the rear end up and preventing your roll bars from collapsing forward in an accident or a very bad bump otherwise.

But anyway, great going, the engineering maybe isn't what some would like to see for your own interest but it's all happening and you are shortly going to be driving around with a big grin on your face which is just fantastic

Thanks cheapracer, that is a great idea and I will try for the red line We are also going to put one between the front shock towers.

Got some parts ordered:

Gas tank filler neck
Push pull cables for clutch and throttle

Now to wire up the engine and get the brake and fuel lines run. Coolant lines and a diff carrier and we are almost drivable! This build is turning out better than I had hoped. Thank you to all of those who have had helpful input.

what's your wheelbase and track width?

also is that all stock miata driveshafts in the rear?

also also wondering how much it's costing to have someone else do the frame if you don't mind me asking.

Just wondering,
doesn't the OBX LSD need to be enclosed and needs LSD oil to lubricate the LSD when its running?

Are you going to build a diff housing later in the build?

Cheers

Just wondering, could some gussets be added in where the tubes don't meet at the nodes and resolve/improve the issue without taking the frame apart and rebuilding it? What do you engineering types think?

I think it has to be figured on a case by case. My experience is only static loading (ie structural) not dynamic loading. So I kinda tend towards taking the maximum dynamic load and looking at it as the base static load.

But the key is that the forces at the node need to be balanced. If a load is introduced near a node, say 4" from the node, that load introduces a moment force at the node, as well as a bending force on the supporting member. (this would probably more significant on round tube than square) In the case of a welded connection at the node, the welds are put into more tension (and compression) than would be normal. Weld penetration would become more crucial here. Sooooooo if you can overcome those challenges..... I think I'd still cut it apart and redesign.

Project is still alive, just moving slowly. It sat like this for a while



timmay - I have not measured the wheelbase yet, but the track width is going to be the same as the miata as I am using the diff, axles, hubs, and wheels for a miata

CHB - Still looking into that part of the build, that headache is one of the reasons that I too a break from it

I hope to have some time in the fall to work on it...