DIY Tubular Subframe Discussion and Builds
 

So counting myself there are about 5 of us that want/need a tubular front subframe. I've been studying pictures and it looks like you could build these for about $200 a piece. I have about 30hrs of MIG experience so I think I can tackle this project. I planned on getting a 99 subframe, rack, and arms to make the jig out of. Looking for ideas on using DOM tubing, pipe, or square bar? How thick of a wall? Diameter size? How thick for the plates. Best way to make the alignment tabs for the eccentric bolts? I don't want to over build this as its tied into the unibody and supports a light 4cyl engine. I found a few threads for diy Miata subframes, but if you have or are in the process of this post up. I will probably be starting this next month, just in the design idea faze now. I have access to decent welder, water jet, and cheap pipe bender.

Home built subframe
MiataV8 Conversion: Tubular Subframe with Ford 302

no suggestions really, other than you should make a thread and document this when you start!

Otherwise, DOM tubing would make the most sense I Think.

For sure, I will list all measurements, dimensions, material. Once you notice that you can buy a Mustang K member for $300 it starts to make sense to build your own if you have the means. I wonder if I should use 1.5x.095 wall or 1.375x.125 wall, which is lighter? I'm also thinking 1/8" plate is enough for the suspension pickups and mounts to unibody. It needs to be light but also withstand a T-Rex attack.

Pipe bender you're using for this DOM tubing?
I've personally had bad luck with a cheap bender and DOM.

Also, you'll need some type of notcher. I don't see why the kind that hooks to a drill press wouldn't work.

I seriously considered building my own subframe, but in the end, I just bought one from V8 Roadsters. After looking at the one I purchased, it has given me some confidence that I could possibly pull off building a rear tubular subframe for the win.


I think to really pull it off, you need to build a jig around your factory subframe to get it perfectly straight, and so everything aligns properly. That will take more time and more materials.

There is no other way to do it than this way. :party:

Wasn't sure the OP realized that or not.

Yes I realize a jig is a must. Keep the conversation going though.

I'm looking at the JD2 Version 3 bender, I have used something similar to build rollbars, racks, and bumpers before.

https://www.jd2.com/p-32-model-3-bender.aspx

Or this

http://www.pirate4x4.com/forum/shop-...ng-bender.html

I'll probably grab a used miller off of craigslist and my family owns a fab shop in south Texas for the water jet plates.

Past project I did summer of 2012, 2x6 slider rocker replacement, aluminum rack, and front bumper. Ignore the wiring, we did it last minute so we could meet up with some buddies out at P.I.N.S at mile marker 35, last minute after it went dark.

http://i16.photobucket.com/albums/b1...psab471eef.jpg

I did the 4x6 rocker at home with a $100 HF MIG, the rack was with a aluminum spool gun, and the front bumper was with a nice Miller.

God damn it. Once again my skimming habit gets me in trouble.


Onward.

I've been heavily considering fabing my own subframe in hopeful preparation of a future J series swap. Looking at things I started to wonder if I could also fix some geometry issues from lowering too much, as in the a-arm angles and bump steer angle. Moving their mount locations UP would help even everything back out.

The easiest way I pictured doing this would be to first make a jig off the original subframe (obviously)
Then before fabbing the subframe, 1 inch spacers would mount the the frames body mount locations, and motor mount locations if using the stock engine. The jig would have to be made with this in mind so that bolting on spacers would actually move the mount location straight DOWN.
From there, fab as normal.

Once bolted to the car, the a-arm and rack mounts would be moved up from their stock locations, but the motor would stay put.
Now is there enough room to move the mounts up an inch? I can't say.
The main clearance issues would be the steering rack to oil pan, upper arms to the body's frame rail, and possibly the rear mount of the lower arm.
Raising those points any amount should help a car that isn't factory height though, it doesn't necessarily have to be as much as an inch.

Just something to think about when fabbing your own subframe.

J swap sounds cool.

I really wish this thread didn't die, anyone on here build one?

Buying the mountless subframe from v8r is just too easy to fuck about with making your own jig and getting a tube bender. Rough math puts return on investment of setting yourself up to make your own somewhere around 20 subframes, not including your time making them.

What I would REALLY like to see is someone take a oem subframe and move all the control arm mounting points up an inch.

As well as the steering rack of course...

With that the RUCA would pretty much bind on the body right away, wouldn't it?

That's why I said it WOULD be nice.....

Maybe cut holes in the body?

Wouldn't that = drop spindle?

Similar yes.

Both correct roll center and bump steer.

Hey guys i wanted to shed some light on this subject, I am a mechanical engineering student at Cleveland state and have 5+ years of experience of machining and about 3+ years of welding and fabrication experience. I designed a K-member that is similar to the v8R kit in solidworks using a factory 95 miata k-member. I already bent up all the tubes and made all of the tabs I just have to put them in the jig that I made and start welding. if you guys have any questions let me know as I may be able to help, ill post updated photos as I go along. i do not yet have the rack and pinion mounts braced in my solidworks design but I plan to come up with a good solution then add that to the model.

https://cimg3.ibsrv.net/gimg/www.mia...e5be3330d2.jpg
https://cimg4.ibsrv.net/gimg/www.mia...6c2b24bcef.jpg

I think you might want to mimic the NB subframe suspension points and rack mounting.

Nice work, BTW

For the subframe, isn't it only the rack mount point that's raised by some 0.5" or less? The track width was handled in the knuckles/hubs.

I *believe* there is roll center corrections to the lower control arms. I know when I swapped my NA to NB subframe I lost camber but gained caster. Could be tolerances or could be intentional. I think it is intentional.

Just did some googling: NB subframe has more caster (UCA moved back, LCA moved forward) and lowered mounting points on the LCA for improved roll centers. Oh yeah, and the rack was moved up for bumpsteer correction which accompanied outer tie rod mounting point changes in the spindle.

I plan to make a better jig in the future and when that happens I could easily do it for the NB subframe as long as I can get my hands on one. I plan to buy a nice big chunk of aluminum plate that I can drill and tap a million holes in to use as a fixture plate for various projects. the jig pictured is something I threw together in a couple hours just to get mine made up real quick.

below are the pieces I have made so far.
lower control arm mount tabs
front cross over tube for the rack mount
bent side uprights
top subframe mounts with holes drilled for the upper control arm mounting tube to get welded in
side rails of the k-member

tubing is 1.5" .120"
and 1" .120"
rectangle is 1"x2"x .120"
and all tabs are .120" and i do plan to gusset them as well.
according to solid works the k member should be about 23 lbs which is lighter than the stock k-member by about 10 lbs.

here is a picture of the various parts I have made so far
https://cimg0.ibsrv.net/gimg/www.mia...bbabde2d84.jpg

Where you located? I've got an NB subframe that I don't need and may see the scrap bin if Craiglist doesn't show any promise.

So guys here is my progress so far,
Using the crappy jig that i made we got the lower suspension tabs all welded up and the front cross over tube for the rack and pinion welded up as well. this all took longer than expected because i had some issues with the mig welder... Ended up just saying screw the mig and just Tig welded it together. I was trying to avoid Tig because if I make a lot of these I would prefer to mig them as it is much faster, but I am no expert at mig and my welds looked good but I am afraid they may have not had enough penetration so. with tig I know exactly whats going on and i feel a lot more comfortable with my tig welds.

here are some pictures
https://cimg0.ibsrv.net/gimg/www.mia...49771d4936.jpg
https://cimg1.ibsrv.net/gimg/www.mia...4e9854715d.jpg
https://cimg2.ibsrv.net/gimg/www.mia...988d9fee89.jpg

I have one question...

is yours gonna better than the V8R unit?
if so, how?


will it be worth the effort, or is it just for fun?

That's a great question!

I believe that what I am doing is worth the effort and will be better than the V8R kit would be for my application.

so the reason for me building this K-member is pretty much based off of two things.

Reason #1 The V8R kit requires a special oil pan or the stock F-body pan to be modified. as well as fancy headers that flying miata sells or that V8R sells and both those header options are $700+ granted you could probably buy your own block hugger headers and modify them to work with that K-member. My goal with this K-member is to design one that you can buy all off the shelf parts from summit racing or jegs, my oil pan of choice is a sheet metal one from jegs that cost me $120 new, also I have decided to go with a Ford racing Close ratio T-5 transmission with a quick time bell housing and a howe racing hydraulic throw out bearing because it is much cheaper than most of the t56 transmissions I could find. also with the t-5 you don't need to modify the trans tunnel.

so even with the quick time bell housing and the throw out bearing my ford racing t-5 was still cheaper than most t-56 options I could find. price for all my trans stuff is $1500 minus the ZR1 flywheel and pressure plate and ford mustang clutch disk.

Reason #2 I like to make stuff! and I really enjoy fabrication, the stuff I have already made has taken maybe 2 hours of designing and 5 hours of fabrication, all I have left to do is the tubes that go to the upper k-member mount.

The Materials to make the K-member and the jig only cost me $140 at my local metal store and im 21 so my time is pretty much either spent on this or out partying "which i really should be out partying instead of this car crap." So vs the $600 for the mount less V8R yes I would say my kit is better for me.

Here are some pictures of my oil pan and other fabrication projects I have worked on

https://cimg3.ibsrv.net/gimg/www.mia...4f2d0b8a17.jpg
Now I did not design this car, it was designed by a good friend of mine who now works as an engineer at honda. but I did do a lot of the fabrication and most of the machine work and almost all of the welding and I was the driver for all the races this car has been in aswell.
https://cimg8.ibsrv.net/gimg/www.mia...372e24f342.jpg
https://cimg9.ibsrv.net/gimg/www.mia...ede7a59595.jpg
https://cimg1.ibsrv.net/gimg/www.mia...b0f155b290.jpg
https://cimg2.ibsrv.net/gimg/www.mia...cea902c7a4.jpg
https://cimg4.ibsrv.net/gimg/www.mia...cca8093ef0.jpg

So I spent three hours last night finishing up the important stuff on the K-member and it turned out really good I think!
I still need to weld on some nuts to the back side of the rack mount bolt holes and i also need to weld on some gussets to the lower control arm mount tabs as well as the fancy little things to help adjust camber with the elliptical bolts.
Any ways here are some pictures of what i have got done so far!

https://cimg8.ibsrv.net/gimg/www.mia...46963e1963.jpg
https://cimg9.ibsrv.net/gimg/www.mia...df41510e28.jpg
https://cimg0.ibsrv.net/gimg/www.mia...e9bdfad5c2.jpg
https://cimg2.ibsrv.net/gimg/www.mia...7c6932d39e.jpg

I think reason #2 is good enough to make one!

The reason I asked is because as you know, a lot of engineering and suspension geometry goes into a subframe design, specially on a car like the Miata where all your suspension points are on the subframe.
If you tweak the geometry even a fraction, you can have detrimental effects due to ackerman and bump steer, so you may have to end up doing it over a few times which sucks up a lot of time and money.

Now, if you can design a unit that is lighter and stiffer than the V8R unit, and keep the geometry correct, then you are doing pretty dam good.
Find a way to correct the roll centers for lowered/race vehicles and you are going to sell a few of these guys.

The other drawback to aftermarket subframes at least in a restrictive rule set, is that you pay a points penalty for using one.

D

Luckily Suspension Geometry is my favorite subject! The Ackermann is mostly dependent on the spindle so my K-member shouldn't influence that too much, Also if i do anything to effect bump steer i will improve it by moving the rack up on the k-member to make the tie rods more parallel with the lower control arm, but for now i have it in the stock location.

one thing i was tempted to play with was kingpin angle to change the scrub radius so that i could run different offset wheels, but i didn't really feel like machining new spindles because i blew up the 4 cylinder turbo almost 8 months ago and i really just want to drive the damn car!

I also toyed with the idea of changing the amount of castor by moving the locations of the lower control arm mounts forward or backward, i am switching to manual steering "properly de powered rack" and was thinking that it might make sence to take some castor out of the car to make the manual steering a little easier with the have ls1 up front. but after driving my friends car with manual steering i decided to just leave it alone.

In the future i plan to make a K-member for the NB suspension geometry as well as a K-member that uses my own design for suspension, i would like to learn as much about suspension geometry as i can, and yes i know this car is not worth anything that im doing to it but at least it gives me a place to refine my fabrication and design skills so that when im trying to get a job at GM or Ford or Honda or Mazda i can walk out into the parking lot during my interview and show them what work i have already completed.

That's awesome man! Your workmanship is so good.

I own a CAD contracting business in NZ. But I am designing an off road buggy as a hobby, not quite like the baja you built, but similar. I plan on using Miata Knuckles in all 4 corners, and possibly using the suspension geometry too. I would love to ask you some questions and get you to have a look at my design if you are interested?

Cheers, Sam.

have you compared weights between the original and yours?

I'd really hate to see this thread die. Any more material on this?

Sorry guys been super busy with school and work!
But the subframe is completed
https://cimg7.ibsrv.net/gimg/www.mia...6e8b12e526.jpg
https://cimg8.ibsrv.net/gimg/www.mia...25ee7807fd.jpg
https://cimg1.ibsrv.net/gimg/www.mia...f8648229c7.jpg
https://cimg2.ibsrv.net/gimg/www.mia...4389b8ddca.jpgAnd the engine fits perfectly! So does all the suspension as well.
The car currently runs. But I have not had time to finish putting the interior back together or finish the exhaust.

Do you plan on making any more of these?

https://v8roadsters.com/product/ligh...ht-subframe-2/

https://v8roadsters.com/wp-content/u...Product-12.jpg

when i finish school this spring i may look into fabbing up some more as i have had a number of requests!

$600 for one without mounts is the biggest rip off i have ever seen. $1200 with mounts is just stupid. literally cost me about $100 in materials and about three hours to make mine. so yeah V8 Roadsters is a F#@*ing joke. even if i decided to use 4130 instead of 1020 steel it would only be about $150 in materials.

So what you're saying is that you'll sell me one of these with BP mounts for $400 shipped, right?

If its 400 shipped you can put me down on the list for sure

Next project is a complete tubular front and rear subframe and arm assembly.... Riiiiiight?

So how much does an ND Miata cost in just materials? Because we all know that that's how you measure the worth of an item, raw materials cost.

You should complain that the price of a megasquirt kit is only a couple hundred dollars and a completed unit is closer to a thousand or more.

Having professional dyno tune your car should be free as well.

Yeah honestly thats kinda the goal! look at tubular sub frames for mustangs and camaro's. they are in the $350-400 range. also the miata k member is very simple

might look into doing a rear. but the rear is so easy to modify to fit a for 8.8 already so i dont really see a need for one yet. unless i get a lot of requests

Kick ass job, looks great! It would be nice to see some competition on cool Miata stuff like this.

Multiple manufacturers is always a bonus and drives innovation as well as price!

Are you considering selling them?

wow way to look sarcastic and unintelligent. maybe try looking at how much materials cost, the machine time to make the parts and labor needed.

I used a old haas vf3 mill to make all my tabs. took less than 30 minutes ti cut out all my tabs from a single sheet of 1/8" 1020

then cut and bent the 1" x .120" wall tube in my bender which took about 45 minutes "this also includes cutting and bending the 1.25" x .120" wall front cross bar for the rack to mount aswell

the tube for the upper control arm i just bought a steel tube and welded in two slugs with a hole drilled in them for the upper control arm bolt add 20 minutes

the rest of the square tube and 1.25" tube going to the upper frame mounts are just saw cut. add 20 minutes
.
then welding, i could tig them if the customer wants but that would cost extra. I just tossed all the parts in the jig i made and welded the whole thing together in about an hour.

that comes out to about 2.9 hours. so yeah about 3 hours worth of work. and if i was charging what i charge customers for work that would be 60/hr for labor (my labor includes the machine time) that would be $186 and add $100 for material "which included the cost of the jig mind you" that is $286 just for me to make it.

So yeah V8 roadsters is kinda joke. sorry for calling you out but paying a sh*t ton of money for something that isnt worth a lot of money is kinda dumb. and people think that it worth it because they are the only ones who make it. but look at mustang or camaro K members. they are like $350-$400.

Iv worked in manufacturing for a while and went to school for Machining and welding and now am one semester from my mechanical engineering degree. So i would say i kinda know what im talking about with this stuff.

When i graduate school i will try to start making them as long as there are no patents stopping me from doing so. i just dont have time right now with school full time, work full time and being vice president on my schools baja team and you know a i got to make time for the girlfriend as well! so hopefully maybe starting august 2018 i can start making some as i have had many requests! glad to see there is a market!

Well other than you clearly valuing your intellectual property as $0, you didn't mention accounting for your business license and federal taxes, property rent or mortgage, utilities, payroll taxes, medical, dental, excetra. Workers comp is another 27% on top of whatever hourly rate you're paying your workers. And you left off the sublet for sandblasting and powder coating. I have met the guy and can tell you he's not building these like some cobbler in his basement. He has employees and subcontractors and buildings and pays taxes.

I'm happy you have a nice little fabrication hobby. Don't try to act like it's a real business if you only charge $40 an hour on your labor. Inexpensive fabricators make twice that easily in my cheap-ass state. Car detailers and grass cutters charge more than $40 an hour down here for their unskilled work if they are actual businesses paying taxes. My company bills out $120 an hour for a mechanic to change the oil on your piece of heavy machinery. Hell, we even charge $120 an hour for somebody to pressure wash the damn thing if you return it off rent dirty.

So, you are either a hobbyist, a tax evader, a lousy businessman, or all three.

Edit: I missed the part where you were still in school. So the real answer is you just don't know anything yet.

yep still in school so i don't know anything yet!

but i do know that i can build them cheaper and have just as good or better quality!

I apologize for not being a business major as well. but i was not planning on turning this into a full out business yet as i have a day job ( great benefits like dental and medical and workers comp, you name it) and this would be selling them to people on here who ask me to make them for them. so yes i am a hobbyist who is able to make them cheaper than V8-roadsters! i have the equipment, the skill, and for sure the knowledge on how to make them, and people have offered to pay me what i want to charge for them.

So please explain why i should not make them if i can sell them and make the profit i am looking to make off them?

I am aware of that. however this is not going to be a full grown business yet. when that time comes i will do the research i need to do. for now i am concerned with finishing school, and helping people out get a good tubular k-member for the price that they should be. how does QA1 and UPR make mustang K-members for $400? they are large companies and are reasonably priced!

I started in business when your mom was wiping the snot out of your nose and wiping your ass. I have to say, you are the typical overconfident kid with some education who thinks you know everything. You might consider toning that down a bit if you think you will do well here and life in general.

I have been in the Mustang world for years. Two obvious things come to mind. There is no comparison in quality and cost to build Mustang K members because they are used predominantly in drag racing. Road racing K members cost more. Also, there is no comparison in the volume of product moved in the Mustang market compared to the Miata market. It costs much more per unit to keep the lights on at V8 roadsters shop compared to your high volume Mustang parts manufacturer. There is also much more competition in the muscle car market. By the way, your Mustang and Camaro K member costs are total bullshit. You are quoting for the cheapest shit.

I know Shandelle personally, he lives modestly and invests everything he has into that business. Oh, and he has a business and you don't.

OK, here's your first lesson in real business. Since you have announced your intention to go into business selling Miata related products on our forum you will be temporarily banned from the forum until you spend the "overhead" to become a forum sponsor just like the other vendors here (or I get bored). Congratulations, I'll treat you like an adult now. Figure out how many units you will likely sell a month versus the cost of being a forum sponsor and add it to your bottom line.

I'll even give you a few minutes to think about it before I temp ban you, just because I'm such a sweet guy and an earnest instructor. And to be clear, I'm not being mean but just fair to the other vendors because this forum is a business entity.

Like you said, "Everything is a learning process. And there is only one way for me to learn and that is by doing it. "

I have no problem with the work you do, or your ideas. It's the shitting on other people, and the acting like you have conquered the world attitude with very little experience I have a problem with.

I don't understand what the argument is. There isn't one to be made. Dude made a subframe, it's cool, and looks like it was made well.

If he wants to make more and advertise and sell to people on here, he can. He will be charged the same vendor fees that anyone else does, and will be protected against "bashing" same as any other vendor at that point.

I bought a V8R subframe in 2017. It was fine. I would also happily pay less for the same thing if it was made available to me. That's how competition works.

However, this sort of thing works itself out in the end. Someone producing these in their garage at $400 each simply is not going to be able to produce the volume necessary to make a significant dent in V8R's business, so it's not something worth arguing about. Increased volume necessitates more overhead costs necessitates increased product costs or lessened profit margin. Market Analysis 101.

In the meantime, everyone is just yapping at each other.

Banning someone who has point blank said that they're not interested in selling a product at this time for not paying sponsorship fees isn't the right answer either.

I guess I shouldn't have expected a more intelligent response, but I did.

Ah, the impertinence of youth.

i may have zero business experience, but i have enough experience in the fabrication, machining and engineering world to make a bracket that connects an engine and suspension to a chassis. i like the V8R K-member that why you see that i made mine very similar to theirs. im not bashing their part or their business. i am just saying that their cost is too high. they have no competition right now. and i dont expect to be much competition for them as i am not a production shop, nor do i plan to be pumping out a ton of these like they do. if someone asks me to make one then i will. i have had people ask me to make them and when i have the available time i will make them and sell them for the price i decide to sell them at. which will be cheaper than $695 which is the base price for an un-painted and no engine mount K-member.

hey you are the one banning someone for posting about their ideas. i have not sold one yet, and do not plan on doing so for a while. but i can tell you right now, when i do start selling parts and if i do make it into a business, i will not be giving you any money for this forum. if you ask me the only person who loses is you. as an OP im pretty sure your job is to get more vendors to sponsor the site and make it a better place. i do not see that happening here. ban me.