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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, Dec-13-2017, 05:42:04 PM   #141
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Default Re: CMP Auto Engineering subframe kit

Tuned in! I’ve been searching for a GTR brace but have been reluctant due to the fact that currently available braces only reinforce the rear mounts. Also, I like your CAD skills.
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Old Wed, Dec-13-2017, 07:44:19 PM   #142
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Default Re: CMP Auto Engineering subframe kit

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Originally Posted by AussieE46M3 View Post
Hi Hal,

Compared to general strut braces the tubing used is likely slightly larger than normal however, I designed it in accordance with the regulations set by the Confederation of Australian Motor Sport (CAMS) as well as the local Australian Design Regulations (ADR LK76-2011) for road/track compliant roll over protection systems/safety cages. More specifically focusing on guidlines for cross bracing/additional bracing and mountings.

I chose to do so as I am contemplating one day developing a bolt in roll cage that I may try to link to this brace. Drifting is fairly popular where I live and it's something I'd like to get into using an E46 coupe chassis likely paired with an LS1 engine. There's a large Matsuri event held twice a year at the local track which will require compliance to the above regulations in order to participate.

These standards outline everything from tube diameter, wall thickness, fastener types/quantity, mount plate thickness and area etc.

For example, the tube is 1.5"/38.1mm diameter, 0.102"/2.6mm thick (the X brace is 1" x 2mm wall) and mounted using 3mm thick plates and M8 8.8 grade fasteners. The brace is entirely bolt in so the shock towers are secured using the shocks studs/nuts, the 'X' brace is linked to the top face of the Topside beam kit using 3x M8 bolts each side and the front extensions are fastened through the centre of the short tube length using a single M8 bolt.
I'm not concerned with the tubing size. I understand your approach. But a frame is only as rigid as its connections. Increasing member sizes without setting up the connections to adequately transfer the forces and bending moments eats up trunk space and adds weight for little/no gain. The welds at the frame rails for the lower bar look like they form fully developed connections for your goals but I'm skeptical of the others because they thin out sharply at the attachment points, and those attachment points are critical for ensuring that local bracing rigidity translates into global chassis rigidity. Just something to consider if you want to make the best part, and when designing more safety-critical parts.
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Old Wed, Dec-13-2017, 09:04:55 PM   #143
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Default Re: CMP Auto Engineering subframe kit

Quote:
FYI that list has the GTR race car and standard e46, but not the e46 M3. The M3 was ~19,000 NM/deg.
(couple extra stitch welds, thrust plate, V brace, and strut tower brace being the significant differences)
Thanks Obioban,

I couldn't find the torsional rigidity for the M3 at the time. That brings the E46 M3 to almost half that of the current gen M3.

My M3 was an early 02 build and didn't come with the front strut brace but it is interesting to see that relatively simple bracing features managed to increase the torsional rigidity of the chassis by over 50%.

Quote:
Tuned in! I’ve been searching for a GTR brace but have been reluctant due to the fact that currently available braces only reinforce the rear mounts. Also, I like your CAD skills.
Thanks M3 pilot. Just need to learn to do renderings and I'll be able to do very pretty pictures.

Quote:
I'm not concerned with the tubing size. I understand your approach. But a frame is only as rigid as its connections. Increasing member sizes without setting up the connections to adequately transfer the forces and bending moments eats up trunk space and adds weight for little/no gain. The welds at the frame rails for the lower bar look like they form fully developed connections for your goals but I'm skeptical of the others because they thin out sharply at the attachment points, and those attachment points are critical for ensuring that local bracing rigidity translates into global chassis rigidity. Just something to consider if you want to make the best part, and when designing more safety-critical parts.
Sorry M3 Hal,

I misunderstood. I know what you're saying. I have seen some braces where they use narrow little fingers with long elongated holes to compensate for their manufacturing tolerance and end up looking somewhat flimsy.

I'll share some pictures of the first test braces I made. At the strut mount, the top plate is 4mm thick and the vertical face the tube welds onto is 3mm thick. I have since made both 3mm.

the vertical plate is constant fillet welded (CFW) to the top plate on both side and curls around the top plate to provide ribs up to the studs slots for a rigid shock connection.

The other mounting plates are simple flat and large enough so that the bolt hex doesn't fowl on the weld bead. The mounting plates that are welded down are full perimeter welded and also have spot welds around the female thread holes.

Excuse my welds, it had been sometime since I had last used a welder. I'm afraid I couldn't find any close up shots of the left shock mount with the tube welded on.








Last edited by AussieE46M3; Wed, Dec-13-2017 at 09:09:16 PM.
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Old Thu, Dec-14-2017, 03:37:03 PM   #144
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Default Re: CMP Auto Engineering subframe kit

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Originally Posted by AussieE46M3 View Post

Yes. Assume an upward force on the bar is creating a bending moment there. The connection would either bend along the flat 3mm plate, or the 3mm plate with the 10mm (or however they measure out) uprights on the end. That is significantly less stiff than the 38mm tube that it is feeding into it. Welding or bolt-thru on the vertical face of the shock tower would increase the stiffness.
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Old Thu, Dec-14-2017, 05:24:59 PM   #145
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Default Re: CMP Auto Engineering subframe kit

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Welding or bolt-thru on the vertical face of the shock tower would increase the stiffness.
Which is what the Mason x brace/GTR bar does.
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Old Sun, Jan-07-2018, 11:20:01 PM   #146
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Default Re: CMP Auto Engineering subframe kit

Quote:
Yes. Assume an upward force on the bar is creating a bending moment there. The connection would either bend along the flat 3mm plate, or the 3mm plate with the 10mm (or however they measure out) uprights on the end. That is significantly less stiff than the 38mm tube that it is feeding into it. Welding or bolt-thru on the vertical face of the shock tower would increase the stiffness.
Morning guys,

Firstly, sorry for my very delayed response. I was fairly active over the Christmas break this year and wanted to focus on being present with the family with what time I had.

I think I know what you're saying now however, the benefit of the additional single shear bolt in the vertical face of the brace seems to be dependent on the perspective you take.

Regarding what you've said above M3 hal, I do not believe the bending moment in the vertical plate is of any significant concern. The tubes mating onto that plate would make any potential strains from the bending moment negigable. I've included a cross section shot below to show where they overlap.



The benefit of the bolt is dependent on perspective. Given the bending moment is negligible, the only benefit I can see of adding the single shear bolt in the side of the shock tower would be if there were differential movement between the side of the shock tower and the vertical plate of the brace.

Given the shock tower is linked directly to the chassis rail below it and the brace is linked to the topside beam kit which is welded directly between the chassis rails I suspect any potential differential movement between the two would be also negligible. If there's no movement between, there's no stress to support.

I believe the majority of elastic deformation occurring would be vertically, perpendicular to the face where the top of the dampener bolts on as is most common. As I said before, if there is no differential movement between the side of the shock tower and brace, a shear bolt in that location does not contribute any rigidity to the brace mount and the best thing to do is add bending rigidity to the top face which I have done to a feasible extent.

I suspect the mason brace includes the shear bolt as it does not tie into the chassis rails and uses this as an anchor point. The Mason brace would also be supporting the greater stresses of both the rear 2 subframe mounts and shock towers.
Having briefly looked at the brace, The Mason brace appears to use thinner steel without any ribbing on the vertical face offering less rigidity at the mount than my own design.


On another note,

The latest batch of parts have arrived from my laser cutter with the components for the first few prototype front mount extensions and 6-point race braces however, during the wait, I had actually chosen to re-engineer the front mount extensions.

The latest design spans between the chassis rails for better rigidity and to support the failure prone spot welds in this area underneath the rear seats and to offer a much neater, lower sitting factory inspired look similar to the E92 chassis. This will also allow a custom floor board to completely cover all the additional structural support right up to and under the rear seats.





Unfortunately, this means the parts I received for the front mount extensions will not be used and the revised parts will be received in several weeks adding further lead to producing the first few prototype braces.

In addition to the new design benefits, it has enabled me to bring the points the race brace contacts the front mounts much closer to the subframe mount for better triangulation however, has created a shorter mounting tubes requiring me to reduce the front extending tubes to 1".





I should be able to disclose pricing for the front mount extensions later this week for those interested.
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Old Thu, Jan-11-2018, 10:46:12 PM   #147
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Default Re: CMP Auto Engineering subframe kit

Quote:
Originally Posted by AussieE46M3 View Post
Morning guys,

Firstly, sorry for my very delayed response. I was fairly active over the Christmas break this year and wanted to focus on being present with the family with what time I had.

I think I know what you're saying now however, the benefit of the additional single shear bolt in the vertical face of the brace seems to be dependent on the perspective you take.

Regarding what you've said above M3 hal, I do not believe the bending moment in the vertical plate is of any significant concern. The tubes mating onto that plate would make any potential strains from the bending moment negigable. I've included a cross section shot below to show where they overlap.



The benefit of the bolt is dependent on perspective. Given the bending moment is negligible, the only benefit I can see of adding the single shear bolt in the side of the shock tower would be if there were differential movement between the side of the shock tower and the vertical plate of the brace.

Given the shock tower is linked directly to the chassis rail below it and the brace is linked to the topside beam kit which is welded directly between the chassis rails I suspect any potential differential movement between the two would be also negligible. If there's no movement between, there's no stress to support.

I believe the majority of elastic deformation occurring would be vertically, perpendicular to the face where the top of the dampener bolts on as is most common. As I said before, if there is no differential movement between the side of the shock tower and brace, a shear bolt in that location does not contribute any rigidity to the brace mount and the best thing to do is add bending rigidity to the top face which I have done to a feasible extent.

I suspect the mason brace includes the shear bolt as it does not tie into the chassis rails and uses this as an anchor point. The Mason brace would also be supporting the greater stresses of both the rear 2 subframe mounts and shock towers.
Having briefly looked at the brace, The Mason brace appears to use thinner steel without any ribbing on the vertical face offering less rigidity at the mount than my own design.


On another note,

The latest batch of parts have arrived from my laser cutter with the components for the first few prototype front mount extensions and 6-point race braces however, during the wait, I had actually chosen to re-engineer the front mount extensions.

The latest design spans between the chassis rails for better rigidity and to support the failure prone spot welds in this area underneath the rear seats and to offer a much neater, lower sitting factory inspired look similar to the E92 chassis. This will also allow a custom floor board to completely cover all the additional structural support right up to and under the rear seats.





Unfortunately, this means the parts I received for the front mount extensions will not be used and the revised parts will be received in several weeks adding further lead to producing the first few prototype braces.

In addition to the new design benefits, it has enabled me to bring the points the race brace contacts the front mounts much closer to the subframe mount for better triangulation however, has created a shorter mounting tubes requiring me to reduce the front extending tubes to 1".





I should be able to disclose pricing for the front mount extensions later this week for those interested.
Any update on your brace design and complete subframe kit?

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Old Fri, Jan-12-2018, 01:32:38 AM   #148
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Default Re: CMP Auto Engineering subframe kit

Crickets...

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Old Fri, Jan-12-2018, 05:11:54 AM   #149
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Default Re: CMP Auto Engineering subframe kit

Quote:
Any update on your brace design and complete subframe kit?
Sorry guys.

I'm still waiting on a quote form my laser cutter for the revised front mount extension design. The first batch is a couple of weeks away still.

Once I have the parts for the revised front mount extensions, I can install it along with the first prototype brace into my own car (I'm hoping 26th-28th of Jan) and soon after wrap up the supporting documentation and have it available to the public.

So in short, I'm planning on having the front mount extensions available by the start of February. The brace's will come some time after.

I've had a few enquiries from fabricators who just want the mounting plates from the brace so they may source the tube locally and fabricate it themselves. I have the mounting plates now and can provide them with a front mount extension for those who wishes to do similarly.
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Old Sat, Jan-13-2018, 01:37:45 PM   #150
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Default Re: CMP Auto Engineering subframe kit

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Originally Posted by AussieE46M3 View Post
Sorry guys.

I'm still waiting on a quote form my laser cutter for the revised front mount extension design. The first batch is a couple of weeks away still.

Once I have the parts for the revised front mount extensions, I can install it along with the first prototype brace into my own car (I'm hoping 26th-28th of Jan) and soon after wrap up the supporting documentation and have it available to the public.

So in short, I'm planning on having the front mount extensions available by the start of February. The brace's will come some time after.

I've had a few enquiries from fabricators who just want the mounting plates from the brace so they may source the tube locally and fabricate it themselves. I have the mounting plates now and can provide them with a front mount extension for those who wishes to do similarly.
Looking forward to this set please let us know how it goes

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Discussing CMP Auto Engineering subframe kit in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)