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Old 12-14-2006, 03:45 PM   #1
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Default DIY Subframe bracing?

Anyone who has taken their engine out or done a diff swap. Have you thought of or done any diy bracing to them?

I've got mine out now and am interested in welding some bar's onto them or plate to box in/triagulate certain areas.

I'll be taking some pictures of mine tonight for refference but has anyone had any ideas?
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Old 12-14-2006, 03:53 PM   #2
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I'm going to design my own tranny brace, similar to the one Moss sells. I will spend half as much and it will be lighter.
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Old 12-14-2006, 04:50 PM   #3
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im interested in doing something similar but im trying to work out the whole bushing thing as solid mounting it probably isnt wise with the engine mounts and diff mounts having some give
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Old 12-14-2006, 05:48 PM   #4
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Something like the FM butterfly brace would be cool...
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Old 12-15-2006, 12:07 AM   #5
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Quote:
Originally Posted by Sirnixalot View Post
im interested in doing something similar but im trying to work out the whole bushing thing as solid mounting it probably isnt wise with the engine mounts and diff mounts having some give
poly bushings will work fine.
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Old 12-15-2006, 01:32 AM   #6
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Quote:
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Something like the FM butterfly brace would be cool...
Yes, yes it would. But for only 400 dollars its not too bad.
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Old 12-15-2006, 01:45 AM   #7
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if you have a friendly neighbor who is a master welding tech, things become much easier.
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Old 12-15-2006, 08:05 AM   #8
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i have a good friend who is a talented welder, has done all my past welding work on my cars.

I was figuring something like a permanent cannon brace, get rid of the tubular ladder bars in the back and make a one piece square framed ladder bar.

I'm just not sure if there is any way to brace the front subframe (engine cradle?* or re-enforce it while its out.

I guess making an L bracket to bolt this to the tranny would work
http://store.summitracing.com/partde...0&autoview=sku
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Old 12-15-2006, 09:36 AM   #9
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The problem with making your own subframe bracing is not the welding but the forces passing through the welds. I would find someone who had a waterjet or CNC mill. Through it in autocad and get it made. Then sell it to people.

If you do put it in Autocad, or draw it out by hand I can model it for you in a few minutes. I can also run it through Mechanica and optimize it.
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Old 12-15-2006, 09:47 AM   #10
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thats way too advanced for me at the moment. I dont have the software for that, i can do a drawing in paint with the measurments but thats about it.

Also no one on island has that kind of equipment lol

i was planning on making some frame rails like FM's....basically its just some sheet steel with 4 bends in it, i might be able to get holes drilled and chamfered as well.
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Old 12-15-2006, 10:07 AM   #11
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Use the mazda technique and just pinch down the ends of tubing, drill holes and bolt up. I found the entire bracing assembly off a later 1.8 in the dumpster.
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Old 12-15-2006, 10:19 AM   #12
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I have the two subframe braces out of a '94 available. PM me if interested.
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Old 12-15-2006, 10:52 AM   #13
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Loki...using Mechanica or some other FEA-based program to optimize would be great, but only if you know the loads being put onto the thing. If you can accurately determine the loads by yourself, you've got yourself a job with any auto company. Any "optimization" is based solely on a specific loading. Since a car is under arbitrary dynamic loading, it takes a lot more brain-power to "optimize" than to throw it into Mechanica. I think you're over-simplifying part design.
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Old 12-15-2006, 01:48 PM   #14
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Heres a good write-up. Just click the next button to scroll through.

http://www.miata.net/hakuna/0007/h0001.htm
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Old 12-15-2006, 05:46 PM   #15
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Quote:
Originally Posted by Atlanta93LE View Post
I think you're over-simplifying part design.
All of engineering is a huge simplification. And i was just going to use mechanica to check for stress risers and such.
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Old 12-15-2006, 06:35 PM   #16
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Of course engineering involves simplification. But we only do it in the absence of accurate information. Much better to get data when possible.

I'm currently working on my Phd in structural engineering, mechanics and materials. One of my office-mates is doing his entire dissertation about effective, lightweight chassis-bracing schemes. He's doing some really cool stuff, but it is way more involved than it seems at first glance. I wish he were using a Miata, but it isn't exactly an archetype chassis.

Some of his general conclusions are that it is much more effective to avoid bending in braces, and design them to be in tension (duh), or concede to the fact that you never truly know the loading.

Bent-tube braces are great for "get'er done" type diy braces to get rid of certain bad dynamic characteristics. But be careful...placed incorrectly and you can get some other weird things happening...
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Old 12-15-2006, 06:40 PM   #17
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Well by doing what I can to help Sirnixalot, its defiantly not going to make things worse.
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Old 12-15-2006, 06:45 PM   #18
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I'm not trying to discourage anybody from trying stuff. Just trying to remind ourselves that not everything will improve the car.
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Old 12-16-2006, 12:20 PM   #19
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im doing a motorsport engineering degree and i understand some of what your friend is doing but not to that degree obviously.

all help is welcome

i never intended to use flatened round tubing like mazda. what i wanted to do was make a rectagular tubed ladder frame with everything welded together then bolted to the underside using all the existing holes
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Old 12-16-2006, 12:40 PM   #20
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Wait instead of using loads, what about displacements? Then its not so complicated.

Last edited by Loki047; 12-16-2006 at 01:07 PM.
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