I got bored and made a subframe.

[dsmornothing]

So over the past few days I have decided to toy around with some new subframe Ideas. I have built a few now with all straight tube, but whats the fun in that? So this time creativity with bending was the goal! Anyways here are some pictures, hope you enjoy!

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[ChiTownHussla]

nice work. You gonna sell em?

 

[Boosted98gsx]

Did you anneal it? There's a reason why you don't hear of many people running tubular subframes, they often break. All those welds have internal stresses now that you need to get rid of if you want it to last, otherwise, through the harmonics of driving, the welds will fatigue and crack. Especially now that you have no dampers to absorb any harmonics in the subframe, you'll reduce the fatigue life of the frame, since it has to take all those vibrations.

They work well if the necessary steps are taken in manufacturing, but most places that try to make these, don't have the equipment (oven) to properly do after treatment.

There's a reason why most manufacturers use folded mild steel. It can handle road harmonics, and that's worth sacrificing the added mass for.

 

[dsmornothing]

I have no doubt in my mind that this subframe will hold up to anything you throw at it.

 

[Boosted98gsx]

I have no doubt in my mind that this subframe will hold up to anything you throw at it.

I'm glad that you have no doubt, but when someone's car is stuck on the side of the road, or they find themselves in a wall because you didn't anneal it, and a weld breaks on the road, and you are neck deep in a lawsuit you may look back and regret those words. I'm 100% infinitely certain that it CAN NOT handle everything that I can throw at it.

People without engineering degrees shouldn't make such bold statements about something they made in their garage w/o a PE to check their work.

That statement is VERY dangerous.

 

[TSi Kid]

I'm glad that you have no doubt, but when someone's car is stuck on the side of the road, or they find themselves in a wall because you didn't anneal it, and a weld breaks on the road, and you are neck deep in a lawsuit you may look back and regret those words. I'm 100% infinitely certain that it CAN NOT handle everything that I can throw at it.

People without engineering degrees shouldn't make such bold statements about something they made in their garage w/o a PE to check their work.

That statement is VERY dangerous.

I'm guessing he has other things done to it to re-enforce it to make sure it will hold. You don't need to come out and attack him, I've seen his work and he is always 100% with it.

What weight differences come with this?

 

[turbosax2]

I'm 100% infinitely certain that it CAN NOT handle everything that I can throw at it.

People without engineering degrees shouldn't make such bold statements about something they made in their garage w/o a PE to check their work.

That statement is VERY dangerous.

And how is your statement any less bold? I'm not saying you're wrong, but just claiming that you're right because you're an engineer is asinine. How about a specific example of a time you created a part similar to his and had it fail testing, whether that be in real-life testing or a computer model? How about citing some references for your statements? How about telling us what kind of forces you can throw at that thing that it couldn't handle?

Like I said, I'm not saying you're wrong (because frankly I have no idea), but please don't expect people to believe your every word just because you have an engineering degree. I'm sure that doesn't fly elsewhere, so why should it fly on an internet forum?

That being said, I would love to hear what kind of forces you expect this subframe to see, and any other relevant data or requirements it should be designed to meet. Of course, with some way to back up your claims.

 

[Boosted98gsx]

And how is your statement any less bold? I'm not saying you're wrong, but just claiming that you're right because you're an engineer is asinine. How about a specific example of a time you created a part similar to his and had it fail testing, whether that be in real-life testing or a computer model? How about citing some references for your statements? How about telling us what kind of forces you can throw at that thing that it couldn't handle?

Like I said, I'm not saying you're wrong (because frankly I have no idea), but please don't expect people to believe your every word just because you have an engineering degree. I'm sure that doesn't fly elsewhere, so why should it fly on an internet forum?

That being said, I would love to hear what kind of forces you expect this subframe to see, and any other relevant data or requirements it should be designed to meet. Of course, with some way to back up your claims.

I'm not going to regurgitate my solids, manufacturing, and machine design 2 classes for you all, because frankly it would be over your heads w/o the leading courses.

Basically, harmonics, (think the sound you hear when you hum that one pitch and it sounds so much louder than all the rest) that is created through dynamic systems because of interference and movement, are necessarily damped in OEM systems by rubber subframe bushings, and using "softer" steels that have a lower elasticity (the ability for them to rebound after being stressed). This is what I'm referring to. He's made a 100% "rigid" metal subframe, connecting multiple harmonic load sources together (tires and suspension, chassis, and the rear diff / drivetrain). These harmonics could cancel each other out, or they could amplify each other, without modeling or simulation, it can't be known. This is why I said that his statement was dangerous.

I guarantee you, using [only] harmonics, I could make that subframs snap like a twig by propogating a harmonic load through it with enough amplitude based solely on its mass and undamped state. Let alone, I could mount the thing, and break it with a large enough moment across one of the welds.

People don't understand that tubular welded steel in manifolds doesn't break because of a static load from the turbocharger, it breaks because of the vibrations the engine is putting through it. You could hang the turbo off one of the manifolds until the end of the world and never see a crack. Turn the engine on, and subject that manifold to some undamped resonation, and BAM, turbo's on the ground.

 

[2slow4utsi]

I'm not going to regurgitate my solids, manufacturing, and machine design 2 classes for you all, because frankly it would be over your heads w/o the leading courses.

Basically, harmonics, (think the sound you hear when you hum that one pitch and it sounds so much louder than all the rest) that is created through dynamic systems because of interference and movement, are necessarily damped in OEM systems by rubber subframe bushings, and using "softer" steels that have a high elasticity (the ability for them to rebound after being stressed). High elasticity also means that a system can become unstable if subjected to repeated loads without damping. This is what I'm referring to. He's made a 100% "rigid" metal subframe, connecting multiple harmonic load sources together (tires and suspension, chassis, and the rear diff / drivetrain). These harmonics could cancel each other out, or they could amplify each other, without modeling or simulation, it can't be known. This is why I said that his statement was dangerous.

I guarantee you, using [only] harmonics, I could make that subframs snap like a twig by propogating a harmonic through it with enough amplitude based solely on its mass and undamped state. Let alone, I could mount the thing, and break it with a large enough moment across one of the welds.

People don't understand that tubular welded steel in manifold doesn't break because of a static load from the turbocharger, it breaks because of the vibrations the engine is putting through it. You could hang the turbo off one of the manifolds until the end of the world and never see a crack. turn the engine on, and subject that manifold to some undamped resonation, and BAM, turbo's on the ground.

So theoretically, the frame could break or is this fact based on book knowledge? Not talking shit, just wondering.

 

[Alex7747]

So theoretically, the frame could break or is this fact based on book knowledge? Not talking shit, just wondering.

Theoretically, the frame could OR could not break. Thats where R&D comes into play. The only way of knowing for sure whether it will last or not would be through testing the product.

Looks good either way .

 

[Boosted98gsx]

Theoretically, the frame could OR could not break. Thats where R&D comes into play. The only way of knowing for sure whether it will last or not would be through testing the product.

Looks good either way .

And that's the point I'm trying to make. Without actually doing dynamic modeling of it, you cannot know, and making a claim that it can take "anything you can throw at it" is dangerous. Just because you added more and more reinforcing mass to something to combat static forces, doesn't mean that a single low frequency harmonic won't shatter a weld.

This is what harmonics does to things, no matter how statically robust they are...

www.youtube.com/watch?v=gHgQALH9-7M

 

[dsmornothing]

First off this is no where near done. And ANY race part is subject to break and could send you into the wall. Ill say straight up I dont recommend driving over pot holes every day of the year. But There is plenty of supporting and gusseting left to be done. And also the 4 mounting points will NOT remain solid. This is just a prototype so we did this to keep cost down on the first one. And to those who are wondering it should weight 50% less than stock and the stock is 45 lbs. Also for the welds cracking they are all being welded with mild steel for more stretch.

 

[cbarr0288]

I agree with what boosted89gsx is saying. You're opening yourself up to a lawsuit if something major happens. There was (probably) no stress analysis that went into that brace, and design is what makes structures like that efficient. There could be one member of the brace which is essentially a truss structure composed of many two-force members. If you don't analyze it you will never know when it will fail and in which section.

I will say this though. It has GOT to be more sturdy than stock, and by the looks of it a lot of other braces. So at any means you are strengthening the chassis. However because of lack of design you are adding a lot of unnecessary weight too.

 

[dsmornothing]

Have you heard of a magnus breaking? I have not..... And not to mention their design kind of sucks in my eyes. I guess time will tell if my subframe will be sending people into the wall! I really see why so many vendors just give up and leave the DSM scene. Some people are straight jack asses. But to the people who support new thoughts and Ideas I bow down to you! You are few and far between.

 

[hubz91talontsi]

Just 2g's?

 

[Calan]

That being said, I would love to hear what kind of forces you expect this subframe to see, and any other relevant data or requirements it should be designed to meet. Of course, with some way to back up your claims.

Agreed. It would be really interesting to have some accurate static force and constraint numbers for this sub-frame, and then see what some FEA would show. Dynamic loading would be the most critical aspect though, and it would be next to impossible to define an accurate scenario for that without having access to a lab and $$$ worth of accelerometers and test equipment. Not to mention it would vary considerably over different cars.

Good old-fashioned R&D, road time, and over-engineering for safety is the best bet in this case.

 

[marcman804]

Keep up the good work man. Im glad to see some one trying new things and let us know how it goes once you get it tested. No matter how good you make things of course there will always be that "one" who tries to bring you down.

 

[greengoblin]

This thread is full of nice work and 's. Keep it up guys!

Kevin

 

[Calan]

Great, now I have nothing to look forward to

Book knowledge and theory are always good to have in your back pocket. Just don't fall into the trap of believing that the real world always follows the rules.

Over the last 20 years or so, I've seen countless mechanical (and even software) designs that "shouldn't" work, but do. I've also watched people with strings of abbreviations after their name stand around scratching their heads clueless as to why something "should" work but just flat doesn't.

It's not that the real world doesn't follow the laws of physics taught in school; it's just that there are usually countless factors that either aren't known when working out a problem on paper, or the interactions are so complex that it just isn't feasible to design something with 100% theory. Sometimes you just have to build it and see if it breaks, and experience will usually trump theory.

With that said, a solid foundation in engineering principals (along with some common sense) is still the best place to start with a new idea.

 

[viperlp01]

An engineering degree is nothing to shake your head at but its the way people act about it. I am hopefully 2 years away from graduating if I keep my 12-14 hrs a semester going and it is tough. Most of my friends are engineers or damn close and keep it on the DL. They seemed to be talked to differently if they say they are an engineer.

Regardless Cory, that subframe looks narly .. I can't wait to see it finished. It is much different than the one Paul is making. The weight is the biggest thing I am looking forward to as well as how much the diff mounts are beefed up.

 

[SlowChild3]

You must have been really bored! You have alot of time just in the jig! Looks good. Oh and please make sure you FPI the welds! My G.E.D. says so! Lol

 

[buhay6]

Some of the things that Boosted98gsx said are very true, see harmonic vibration cracks all the time on aircraft skins and not to mention a lot of other things; so he not just making that up. But I agree with people his arrogance is unbelievable what and asshole, funny how a lot of high end professions act that way toward people (doctors, fighter pilots) makes you wanna just deck'm in the face.

@dsmornothing
My suggestion to you is just check all of your welds and make sure you have good weld penetration. Then test the crap out of it, litterly destroy it to see where its weak points are so you can correct it first before offering out test models. Personally I'd say use the product yourself for a year first (at lest) before offering it to other DSM'ers, send with a waiver saying its a test model and your not liable if it fails etc etc.... (use at your own risk kinda thing). Then you should be fine lawsuit wise. The best parts are the ones that are tested to perfection. There's a lot of us that are behind you man, keep it up and keep us updated because we'd all like to you succeed!

 

[livedsm4g63]

Someone should get the dimensions and throw it into Catia or NX and see what happens when the load is put on it.
I would but I'm in my last semester. Lots of work going on.

 

[Boosted98gsx]

Someone should get the dimensions and throw it into Catia or NX and see what happens when the load is put on it.
I would but I'm in my last semester. Lots of work going on.

Give me a CAD document (IGES preferred) and I'll throw it on ANSYS for some Modal analysis.

 

[dsmcrzy]

Um, harmonics and model analysis are WAY OVER THE HEAD of most people....

No need to belittle people there really is nothing special about those programs set a monkey in front of them and they can run a test on a model. I think you are thinking too far into this man I doubt the harmonics this subframe will see will break it. I understand where you are coming from but based on the OP's other build posts the dude can weld and weld great! plus he said he made it out of mild steel but that was after you had to show off your degree.

I think a lot of people on here are plenty competent to understand what you think is too much for them.

OP good work and hopefully you will keep us up on the progress!!!