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 Post subject: Re: Box Plate Chassis
PostPosted: October 13, 2016, 3:01 pm 
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Yes looking at it I believe you are correct, it could run in AMod but not the usual D/EMod which comes with about a 5 seconds PAX disadvantage (which most people don't care about anyway).

Bobber it is a really cool idea what you are working on. I love working with aluminum it is easier to cut, bend, prepare, is really light and does not rust so you can just use it as it. The only thing is it is an absolute bear to weld. I have successfully managed to join a few piece of aluminium together using my Mig welder with a spool gun but don't know if I could consider it welding ;-).

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 Post subject: Re: Box Plate Chassis
PostPosted: October 14, 2016, 11:47 am 
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Joined: April 15, 2014, 1:54 pm
Posts: 470
Again, great comments.

My (funny looking) roll cage is supported on the rear IRS cradle. I will extend the steel roll cage tubes to attach to the front cradle and, viola, I'm SCCA legal! I could polish this chassis and maybe blind the other drivers?

Welding aluminum really is for the very skilled. I've got my new drill press (Craftsmen 10", 1/2 horsepower) and some pieces of aluminum. I'm going to experiment with bolted construction. I know the highest stress in this chassis so now it's time to go into the shop and break something to see if it will work in reality. When I was diving, we bolted all our marine equipment together so we could dismantle and store it, so its possible to use bolted construction. I looked at solid aluminum rivets - 1/8" AN426, 2117 T4. They're only good for about 200 lb in shear so they would require very close spacing (see airplanes).

On our marine equipment, we typically used No. 10 alloy steel socket head screws (Unbrako or Holokrome). They're strong and when they rusted in place, we just removed them by popping them off with a cold chisel - faster than a wrench. We kept a supply of nuts and bolts on hand and replaced bad ones before every diving operation.

Time to go to the garage and break something. Build on!


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 Post subject: Re: Box Plate Chassis
PostPosted: October 14, 2016, 11:06 pm 
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Joined: October 24, 2008, 2:13 pm
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Location: Carlsbad, California, USA
Using the subframes for the suspension, etc. is a nice idea, and very practical too.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

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 Post subject: Re: Box Plate Chassis
PostPosted: October 15, 2016, 2:39 pm 
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This should be over in the other post, but rat rod guy found someone who wants to build the cradle to put a Camaro IRS into a Honda Passport, along with an LS engine. Now if I can get him to faburcate a couple extras.........


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 Post subject: Re: Box Plate Chassis
PostPosted: October 18, 2016, 11:10 am 
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Here are some details for bolting the box plates together in lieu of welding. This is typically how we built our marine diving equipment, fastening the plates together with angles and screws. The flat head screws prevented tangling of our lines.

The photos show a sample joint that I put together for testing. I used 1 inch by 1/8 inch bars to represent the plates being connected. The principal load is axial along the angle, which will be replicated by loading the bars in compression to transfer shear through the fasteners and angle.

The design load limit for this connection is 690 lbs with a 1.5 safety factor. The failure mode should be bearing at the head of the screw. My load cell goes up to 1,000 lb.

I’m off to the shop to break it.


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 Post subject: Re: Box Plate Chassis
PostPosted: October 18, 2016, 2:54 pm 
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Well, that was a very successful failure. The load cell topped out at 1000 lb with no visible connection distortion. I continued to apply load and the joint finally deformed 1/10 inch before the screw broke. The deformation was primarily from bearing failure at the head of the screw as predicted by analysis, and bending of the screw (the screw was fully threaded).

This joint is successful because it sustained the load without slippage, and then still held the load through a forced slippage of 1/10 inch. This is the way we design stuff for earthquakes – survive not only the earthquake force, but also the earthquake induced movement.
I consider this joint is crash worthy.

Now, what else can I break!?


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 Post subject: Re: Box Plate Chassis
PostPosted: October 18, 2016, 7:50 pm 
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A curious person (me) would like to see a picture of the test rig that you used to break that joint.

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 Post subject: Re: Box Plate Chassis
PostPosted: October 19, 2016, 2:10 pm 
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I used my neighbor's hydraulic press. He's at the TJ orphanage today so I can't photo. The load cell is just a 3"x1" puck type that I got for free from a test lab - the deflection circuit doesn't work but it reads loads and he calibrated it for me. These things are expensive new. You just place it between the ram and the part and squeeze away. It has an internal anvil so you can't crush it. I made up a little fixture to hold the part and keep the load axial.

Ain't nuthin better than breaking somethin! Specially if your life may hang on it.


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 Post subject: Re: Box Plate Chassis
PostPosted: October 20, 2016, 1:21 am 
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Bobber, I really applaud your running a simple test.

Broken pieces are so much stronger than opinions.
:cheers:

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 Post subject: Re: Box Plate Chassis
PostPosted: November 3, 2016, 3:39 pm 
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That felt Good! Yep, I broke something else! I wanted to see how bendable the 1/8 inch aluminum 6061 T6 plate is. I cut a ½ inch wide strip out of some plate and did some bend tests. I ground one edge smooth and left the other jagged to see if stress risers affected anything. They didn’t in this case. The Aluminum Association code recommends a minimum 3t bend radius so I first bent the strip around a ½ inch mandrel and got a 3/8 inch inside radius after spring back (= 3t). Of course, no problems. So I started crushing it in a vise. I easily got down to a 1/4 inch inside radius with no cracks (= 2t). At around a 1/8 inch inside radius bend (= 1.0t), cracks appeared in the back of the angle. Multiple cracks appeared in the back of the angle but not at either the smooth or jagged edge. After initiation of cracks, failure was right now.
Good to know this stuff. Sorry the photos are not better.


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 Post subject: Re: Box Plate Chassis
PostPosted: November 5, 2016, 3:27 pm 
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Location: Norfolk - UK
Have you come across Pugwash's project, over on the Ozclubbies forum?


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 Post subject: Re: Box Plate Chassis
PostPosted: November 6, 2016, 1:38 pm 
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I've built a couple of aluminum frames. For one of them C5 Corvette cradles bolted to it. I kept the C5 stock wheelbase, had the torque tube cut and shortened 23 inches to move the engine rearward. I used an LS6 engine with the T56 transaxle. I made simple Hot Rod inspired fiberglass panels to skin it. Then later made a Lister Knobbly inspired body for it.

The frame that I built used T6-6061 rectangular tubing to which 1/8 inch T6061 aluminum shear panels were seam welded. It had a huge trans tunnel that served as the backbone.


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 Post subject: Re: Box Plate Chassis
PostPosted: November 7, 2016, 11:06 am 
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Stinger, I think I remember your build. I think you machined something to mate to the Corvette transaxle? That was my inspiration for extending the drive thu a Corvette diff to an marine outdrive attached to the rear of the car. The car would have to float, though.
Would the Corvette cradles you used fit the design OmahaVet is putting together?


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 Post subject: Re: Box Plate Chassis
PostPosted: November 8, 2016, 7:43 pm 
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Bobber wrote:
Stinger, I think I remember your build. I think you machined something to mate to the Corvette transaxle? That was my inspiration for extending the drive thu a Corvette diff to an marine outdrive attached to the rear of the car. The car would have to float, though.
Would the Corvette cradles you used fit the design OmahaVet is putting together?


They were standard C5 cradles. So, I think they would fit.


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