Bayside Fabrication S54 E30 Subframe Solution

[digger]

For nearly two decades I’ve designed, detailed and signed off on multiple vehicle bodies, super structures and body mounted equipment all of which were highly optimised safety critical fabricated components operating in a dynamic environment. Accordingly I’ve had to meet strict design codes and requirements to achieve certification.

Typically this involves lots of verification and validation using hand calculations, FEA, static and dynamic strain gauge testing. These days i do lots of consulting work and regularly come across issues where designers haven’t though about load paths and have used exceptionally poor weld joint details. Things don’t usually snap in half due to overload except in collision scenarios they usually crack over time due to fatigue. In a dynamic environment any weakness in the design will always be found out its just a matter of how far down the line.
My comments were not because i am an asshole or picking on this design (others around are not really great either) it was free advice as i know when something doesn’t really look right. It’s always a good idea to draw free body diagrams, look at load paths and force flow to make them as continuous and direct as practical, minimise discontinues and minimise welding if you dont have access to fancy analysis tools.

[dynoclimb]

The forces and moments can be resolved with a free body diagram, but the geometry of his metal looks fairly complex. I wouldn't want to try to figure out the stresses by hand.

Yes but you could generalize a lot of this to get the idea of how it looks.
Yes the fore/aft suspension loads with the extra gusset tube are nice(But what, that just get dumped into the fire all.....) then the steering lateral loads get simplified into compression/tension over the cross tube and its offset connection to the old sub-frame. even starting at looking at it to this level would be reasonable.



edit:
I just don't like the blanket, of course its better, because "insert my opinion" it is argument. This could be looked at a lot of ways. I also get that this what we're doing, but we're just asking for proof of why its better, not just being told its better.

[The Dark Side of Will]

Even just hand calcs breaking things down with a basic freebody diagram would cover the commentary...(FEA/FEM is overkill for this) there are aspects of this that look simpler to fabricate, but just stating without data that its better, and then only backing it up with an "I know better, of course it is" doesn't ring...

The forces and moments can be resolved with a free body diagram, but the geometry of his metal looks fairly complex. I wouldn't want to try to figure out the stresses by hand.

[The Dark Side of Will]

IF

You put a shear plate in here that connected both ball joint bosses to both rack bosses...

AND

Made your lower rack mounts triangular so they have very wide bases to react transverse forces

THEN

I think your design would be much stiffer in reacting transverse forces from cornering loads.

Also, you have a lot of places where three beads meet where you're welding three pieces of metal together at a corner. This promotes stress fractures at the point where the beads meet. As a bead cools, it contracts and puts tensile stress into the metal next to it. When you join a second bead up to the end of a first bead, you increase that tensile stress at the point where the beads meet because the second bead pulls more on the surrounding metal where the first bead already pulled. Loads in a structure tend to produce the highest stresses at the corners. Joining the beads creates a small area of high stress and the fact that the loads naturally produce higher stresses at the corners of the structure combine to create the perfect circumstances for nucleating a crack.

True structural welding rarely joints beads.

ETA: I just noticed the HoHo in the background. Bump that transverse ball joint load up to 2000#...

[dynoclimb]

Where's the data? What is the deflection of your ball joint mount with 1000# of lateral load vs deflection of the ball joint mount in the stock crossmember?

Don't have structural test data? Ok, just post screen caps of your FEA with the same load conditions.

Don't have either of those?

Then you really have no idea how its strength compares to stock.

Sure, you made a lot of welds and because of that you really WANT it to be stronger than stock because you're personally invested in the product.

But you should not let that blind you to the fact that you are presenting the argument that your product is stronger WITH ZERO DATA.

To me it looks like you've braced it well against braking loads (the braces that go back to the firewall) but it's going to be fairly floppy for cornering loads.

Even just hand calcs breaking things down with a basic freebody diagram would cover the commentary...(FEA/FEM is overkill for this) there are aspects of this that look simpler to fabricate, but just stating without data that its better, and then only backing it up with an "I know better, of course it is" doesn't ring...

[The Dark Side of Will]

This setup is exponentially stronger than the factory subframe.

Where's the data? What is the deflection of your ball joint mount with 1000# of lateral load vs deflection of the ball joint mount in the stock crossmember?

Don't have structural test data? Ok, just post screen caps of your FEA with the same load conditions.

Don't have either of those?

Then you really have no idea how its strength compares to stock.

Sure, you made a lot of welds and because of that you really WANT it to be stronger than stock because you're personally invested in the product.

But you should not let that blind you to the fact that you are presenting the argument that your product is stronger WITH ZERO DATA.

To me it looks like you've braced it well against braking loads (the braces that go back to the firewall) but it's going to be fairly floppy for cornering loads.

[wazzu70]

This design is a lot better than the “other” style. I agree with diggers comments as a good place to add bracing to tie things together better.

As mentioned, you added a lot of plating which will strengthen the cantilevered mounts. The plating thickness you used is beefy!

[Widebody325]

Give the people what they want lol. All jokes aside i perfer something like Tyler but adding what you feel needs improvement such as reinforced mounting points. Adding the option for a e46 ps rack is a plus for me and I’m sure for other people doing the swap. If it’s something you can work out for me i will be happy for your service.

No offense to Tyler but his early options had issues cracking and were not up to what I would consider to be “the best way”. My design keeps oil pan almost stock configuration. Also the rack you see in my setup is a e46m3 rack.

[ararod9]

Give the people what they want lol. All jokes aside i perfer something like Tyler but adding what you feel needs improvement such as reinforced mounting points. Adding the option for a e46 ps rack is a plus for me and I’m sure for other people doing the swap. If it’s something you can work out for me i will be happy for your service.

[Widebody325]

I am definitely interested since Tyler is no longer providing the service. However I am not entirely sold on it until it's been mass produce and flaws that are not notice has been fixed . Is the product in the picture the first one you made? Also is the rack mounts custom for e30 ps rack or e36/e46 ps?

This is the first one and it’s in my car. I understand your concerns since there isn’t a bunch out there. As far as flaws I’m not sure what you are referring to. It’s a reinforced steel subframe with additional mounting provisions. There’s nothing really crazy going on here other than being super beefy. The rack is spaced for stock e30. Or you can just run spacers and do a e36/46 rack too. I mean if people want me to make a subframe like Tyler’s because they trust I can. I just feel it’s a inferior product compared to this.

[ararod9]

product knowledge

I am definitely interested since Tyler is no longer providing the service. However I am not entirely sold on it until it's been mass produce and flaws that are not notice has been fixed . Is the product in the picture the first one you made? Also is the rack mounts custom for e30 ps rack or e36/e46 ps?

[Widebody325]

With this subframe, would you have to pull the engine to remove the rack? Or is the enough room to support the motor independently and remove the subframe/rack to finagle the rack out? Just thinking about future maintenance/mods. Looks cool either way.

I think you'll be fine with this style. It's real similar to the way I modded my subframe to fit the volvo turbo motor, except you added more bracing! Ha.

There’s definately no issues with this style or design. It’s certainly stronger than oem. To remove rack you have to pull the subframe. However, all I do is lay 2-2x6 on edge and bridge across engine bay. Then I take the weight off the engine with a ratchet strap to the lift eye. Takes about 5 mins but you have to pull fenders.

[iansane]

With this subframe, would you have to pull the engine to remove the rack? Or is the enough room to support the motor independently and remove the subframe/rack to finagle the rack out? Just thinking about future maintenance/mods. Looks cool either way.

I think you'll be fine with this style. It's real similar to the way I modded my subframe to fit the volvo turbo motor, except you added more bracing! Ha.

[Widebody325]

The tube will support the rack but not the engine mount forces it's too far away and not enough stiffness to be affective. IMO you need to form a torsion box and gusset to the memeber that spans across. a rectangular hollow section is the preffered section you end up with much better weld details

I’m going to disagree with you’re opinion. This setup is exponentially stronger than the factory subframe. Everything is plated with 1/8” plate and there is 3/16” angle reinforcing the original subframe. There’s additional mounting points to further support the setup. This design works and works well even if you don’t think so.

[digger]

The tube will support the rack but not the engine mount forces it's too far away and not enough stiffness to be affective. IMO you need to form a torsion box and gusset to the memeber that spans across. a rectangular hollow section is the preffered section you end up with much better weld details