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View Full Version : Safe to cut this area out while body is on the rotisserie?



Bitchin'57
03-23-2016, 04:41 PM
I need some advice. I want to cut this rectangular area out, in order to clear my rear suspension and exhaust pipes. I'll be cutting inside the tape lines. Ignore that lone horizontal piece of tape. After the cut, the plan is to build a frame work out of small square tubing, weld it in place, and then make a removable panel to cover the area. My question is, will I be safe in cutting out this area while the body is on the rotisserie, or am I asking for trouble? If its the latter, I'd be open to adding some support bracing, such as adding braces that span from the rear floor brace to the rearmost body mounts. To indicate a sense of the structural integrity of my '57 2dr Sedan, the floor, floor braces, rockers, rear tail brace, and wider wheel houses are new, and I X-braced across the door openings.

This video illustrates what I want to achieve. At 4:15 into the video, you'll see what the end result will look like. https://www.youtube.com/watch?v=5I-esBZOVxA

http://hemiduster.com/floorcut1.jpg

chevynut
03-23-2016, 06:24 PM
I don't think there's a problem with it. I lifted my Nomad body like this:

http://www.trifivechevys.com/attachment.php?attachmentid=5851&stc=1

Bitchin'57
03-24-2016, 10:11 AM
Thanks, chevynut. Wow, you really brought that Nomad back from the dead!

chevynut
03-24-2016, 11:27 AM
Wow, you really brought that Nomad back from the dead!

Actually the car was pretty solid except for the floors and tubs. The roof was perfect, the doors were solid even at the bottom, the cowl is good, and the fenders had almost no rust and toe boards were good. The tailgate bottom needed repair, and both quarters. tubs and rockers were rusty. I replaced the entire floor, making a custom cargo floor, both rockers, both floor pans, braces, and fixed the tailgate. Hopefully I got it all ;).

http://www.trifivechevys.com/attachment.php?attachmentid=5856&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=5857&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=5858&stc=1

Bitchin'57
03-24-2016, 06:30 PM
Very nice! Nothing like brand new sheetmetal. I like how you framed out the cargo floor. Whoa.....judging by the time stamp, you've been working on that car for 10+ years!!
I just wish that the jugheads who installed the new metal on my car would have sprayed it all with epoxy primer. I had to de-rust the entire bottom with multiple applications of Ospho. The surface rust is all gone, I'm now in the process of cleaning off the black iron phosphate residue with a wire wheel. Once that's done, I'll preserve it with one wet coat of my favorite industrial grade epoxy primer, Axalta Corlar 2.1 ST.

Rick_L
03-24-2016, 07:20 PM
If you have no rust issues in the tail pan area and rear trunk floor - and you have fully welded your new tubs - you'll be fine.

For anyone that has rust issues, you don't want to repair the tail pan/rear trunk floor area on the rotisserie - instead you want to have the body on the frame if it's bad, or support the body at the cowl and at the body mounts just forward of the axle hump if it's not too bad. Then cut out that area to modify if that's your plan.

Bitchin'57
03-25-2016, 11:01 AM
If you have no rust issues in the tail pan area and rear trunk floor - and you have fully welded your new tubs - you'll be fine.

For anyone that has rust issues, you don't want to repair the tail pan/rear trunk floor area on the rotisserie - instead you want to have the body on the frame if it's bad, or support the body at the cowl and at the body mounts just forward of the axle hump if it's not too bad. Then cut out that area to modify if that's your plan.
Thanks, Rick!

Bitchin'57
03-26-2016, 10:57 AM
Just an update. Out of an abundance of caution, I added bracing before I started cutting. I used an air body saw and a 4-1/2" cut-off wheel to make the hole.
The work of building a framework for that area begins. The structure will be made of 3/4" square tubing and some steel angle. Thanks again to Rick and Laz for the advice!

http://hemiduster.com/floorcut3.jpg

chevynut
03-26-2016, 11:37 AM
Caution is never a bad thing, but I think you were fine without the bracing. The inner wheelwells, inner quarters, wheelhouses, and quarters would keep anything from flexing and there's a pretty strong "box" formed at the top of the quarter. It never hurts to be safe, especially if it's easy. ;)

I'm interested in seeing what you have planned for that hole now. :)

Bitchin'57
03-27-2016, 07:35 AM
I'm interested in seeing what you have planned for that hole now. :)
Yeah, me too. LOL I have a general idea in my head, but nothing drawn out yet. It won't be complicated, so I won't bother to make a 3D model in Inventor, although I might draw it out in Autocad, just to get my angular (mitered) cuts and lengths. I already have two lengths of 1" steel angle welded in place, which gives me a flat, straight and parallel foundation to build off of.

Bitchin'57
03-31-2016, 06:46 PM
This thing is almost done. Frame is 3/4" x .062 wall square tubing, top is 14 ga. sheet, and the sides are 18 ga. sheet. I plan on mounting a 60 lb. battery on top, and possibly a small subwoofer box, so I had to build it strong. I'll epoxy prime it this weekend before I finally weld it in place. The opening will be covered by an aluminum access panel.

http://hemiduster.com/trunkhole3.jpg

NickP
03-31-2016, 07:15 PM
Nice work. One assumes the top has some structure to support near 80lbs.

Bitchin'57
04-01-2016, 05:27 AM
Nice work. One assumes the top has some structure to support near 80lbs.
Yes, the the top perimeter is boxed with 3/4" square tubing, with another piece of 3/4" tubing going front to back in the middle of the box frame. There are 3 short legs in the front that will be welded to another length of 1" steel angle. The piece you see on the trunk floor is 1" steel angle.

http://hemiduster.com/trunkhole1.jpg

http://hemiduster.com/trunkhole2.jpg

Bitchin'57
04-02-2016, 09:09 AM
Nice work. One assumes the top has some structure to support near 80lbs.
I gave it the 215 lb. test.

http://hemiduster.com/standon.jpg

Bitchin'57
04-03-2016, 01:44 PM
Epoxy primed, and welded in place. I just need to make an access panel out of aluminum, and it will be held in place by a full length piano hinge and a pair of Dzus fasteners. Perimeter of opening will be sealed with weatherstripping. This was a lot of effort for very little gain, but I had to do something about the clearance issue.

http://hemiduster.com/trunkhole4.jpg


http://hemiduster.com/trunkhole5.jpg


http://hemiduster.com/trunkhole6.jpg

NickP
04-03-2016, 02:44 PM
I gave it the 215 lb. test.I understand that test quite well and hence my question and concern. I have employed the very same test before and still succumbed to a failure of structure. A single time test with 200+ pounds will in no way simulate 60 to 80 pounds of constant vibrating weight applied to an area. I'm not an engineer, never professed to be one but I suggest that this type question be place on the table for discussion. Here's my concern; an 80 pound weight, secured in some fashion to a spot of your choice on the assumed side with the single center bar bouncing up and down and imparting that force for a long trip may cause more damage than a single person perched on top of the same location for a momentary test of strength. JMHO & 3₵

chevynut
04-03-2016, 03:00 PM
Nick, you're starting to sound like someone else here....LMAO! :) :)

IMO the structure is just fine. There's not much load and even a sheetmetal structure would have worked. Reinforcing it with tubing makes it plenty strong, based on my seat-of-the-pants engineering. :)

Bitchin'57
04-03-2016, 05:27 PM
I understand that test quite well and hence my question and concern. I have employed the very same test before and still succumbed to a failure of structure. A single time test with 200+ pounds will in no way simulate 60 to 80 pounds of constant vibrating weight applied to an area. I'm not an engineer, never professed to be one but I suggest that this type question be place on the table for discussion. Here's my concern; an 80 pound weight, secured in some fashion to a spot of your choice on the assumed side with the single center bar bouncing up and down and imparting that force for a long trip may cause more damage than a single person perched on top of the same location for a momentary test of strength. JMHO & 3₵
Boy, its a tough crowd here! If my '57 was going to be attached to one of the solid rocket boosters on the space shuttle, I could agree with your thesis.........LOL

NickP
04-04-2016, 06:59 AM
Boy, its a tough crowd here! If my '57 was going to be attached to one of the solid rocket boosters on the space shuttle, I could agree with your thesis.........LOL

I yield the floor to those that know more. (Pun intended)

Rick_L
04-04-2016, 05:04 PM
My quick analysis agrees with the "215 pound test".

The structure is fine, now it's a matter of how that stuff is attached to that nice box.

Bitchin'57
04-05-2016, 01:01 PM
My quick analysis agrees with the "215 pound test".

The structure is fine, now it's a matter of how that stuff is attached to that nice box.
As of right now, the only piece of equipment that I know is going on the deck will be a Diehard battery, housed in an Artec Industries battery box.

Rick_L
04-05-2016, 03:36 PM
My point on that was that you shouldn't just put a bolt hole out in the middle of the sheet metal with no reinforcement, where it might pull through or distort the sheet metal. Not hard to make right.

55 Rescue Dog
04-05-2016, 03:49 PM
I would look to stash the battery lower, and underneath the cover somehow.

Bitchin'57
04-05-2016, 04:38 PM
I would look to stash the battery lower, and underneath the cover somehow.
???

Bitchin'57
04-05-2016, 04:40 PM
My point on that was that you shouldn't just put a bolt hole out in the middle of the sheet metal with no reinforcement, where it might pull through or distort the sheet metal. Not hard to make right.
Large OD fender washers will take care of that. Keep in mind, that top sheet metal is 14 gauge CRS.

55 Rescue Dog
04-05-2016, 05:18 PM
???
Just something to consider. The lower you can mount dead weight, like a battery would be as low, right, and in between the F/R axels, the better is all.

chevynut
04-06-2016, 05:04 AM
The lower you can mount dead weight, like a battery would be as low, right, and in between the F/R axels, the better is all.

Please explain why it's better to put a battery between the front and rear axles.

55 Rescue Dog
04-06-2016, 05:50 AM
Please explain why it's better to put a battery between the front and rear axles.
Might not be possible on a tri-5, but any mass away from the center of the car increases the polar moment of inertia, and mounted high would raise the CG a bit too. The stock battery location is not a very good spot for a battery either. If it could fit, under the rear seat would be the best spot for extra weight. Mounted high on the right rear would be a good spot for forward traction though.

chevynut
04-06-2016, 06:54 AM
I understand the polar moment of inertia argument and that's why my Porsche handles so well, since the engine is in front of the rear axle. But from a practical point of view it's not very feasible (or safe) to mount a battery inside the car. Maybe I should have put mine in the console. :) Since these cars are usually front heavy, wouldn't mounting the additional weight at or behind the rear axle improve weight distribution? Mine is behind the right rear tire, in the wheelwell, about at cargo floor level.

You can nitpick about what's best all day, but in the end the location of a 40 pound battery isn't going to make much difference on anything but an all-out race car, and not much there either. The driver would be better off losing a few pounds. :)

55 Rescue Dog
04-06-2016, 09:31 AM
I understand the polar moment of inertia argument and that's why my Porsche handles so well, since the engine is in front of the rear axle. But from a practical point of view it's not very feasible (or safe) to mount a battery inside the car. Maybe I should have put mine in the console. :) Since these cars are usually front heavy, wouldn't mounting the additional weight at or behind the rear axle improve weight distribution? Mine is behind the right rear tire, in the wheelwell, about at cargo floor level.

You can nitpick about what's best all day, but in the end the location of a 40 pound battery isn't going to make much difference on anything but an all-out race car, and not much there either. The driver would be better off losing a few pounds. :)
If battery placement makes little difference, why do some OEM's mount the battery under the rear seat, or in the rear?
Even the C3 Corvette had the battery mounted directly behind the driver seat, and it was acid filled! I would definitely use a AGM battery, which is what I used when I had a C3. The battery can be useful ballast, and actually in the console would be a great place.:)

chevynut
04-06-2016, 10:27 AM
If battery placement makes little difference, why do some OEM's mount the battery under the rear seat, or in the rear?


Because that's where it fits ;).

How much difference does location really make with a 40 pound object in a street car? My Porsche battery is located at the base of the windshield...that's where it fits the best and happens to be a good location for it. Why didn't they put it behind the seats if that's better?


Even the C3 Corvette had the battery mounted directly behind the driver seat, and it was acid filled!

Why didn't the C4, 5, 6, or 7 Corvette put it behind the seats if that's the best place for it? The C4, 5, and 6 had it under the hood near the firewall. The C7s put it in the extreme rear of the car, just forward of the rear bumper on the right side. That's probably because that's where they had room for it, and perhaps for better weight distribution...I doubt it has anything to do with polar moment of inertia.

Batteries can be dangerous, and putting one in the car near passengers isn't a good idea, imo. Even an AGM battery can explode, I've read. So can a LiIon battery...just ask Boeing. BTW, it's also a violation of SCCA rules to put a battery in the passenger compartment, if that matters.

"15.9 (C):
Relocation of the battery or batteries is permitted but not into the passenger compartment. If the battery is relocated and the original battery tray can be removed by simply unbolting it, the tray may be removed, or relocated with the battery. Holes may be drilled for mounting or passage of cables. Longer or shorter cables may be substituted to permit relocation. The number of battery or batteries may not be changed from stock. The area behind the rearmost seat is not considered to be within the passenger compartment. The area under the rearmost seat is considered to be within the passenger compartment."


What OEMs mount the battery under the rear seat? :)

markm
04-06-2016, 10:32 AM
My folks old 2005 Caddy Deville had the battery under the back seat cushion from the factory without much of a tray. It has become increasingly obvious that Cnut has never been a drag racer.

567chevys
04-06-2016, 10:39 AM
Wow ,

My dads 1937 Chevy Has the battery in the Passenger side front Floor Board(under) , It's OEM installed .

Olderthandirt
04-06-2016, 03:02 PM
For what it's worth the eight generation Riviera had the battery under the passenger side of the rear seat. It was vented through the floor from each end of the battery.

55 Rescue Dog
04-06-2016, 03:20 PM
I cannot wrap my head around why wouldn't putting one plus percent of the cars weight, in the best place possible it will fit, that would improve weight distribution? Weight does matter, and always try to look for a better spot, and seal/protect it securely from the passenger compartment is common sense of course, with a disconnect easily reached by the driver is a plus. That's what I did on my hot rod.
AGM battery mounted outside the interior, frame level, ahead of the right rear axel, with a steel frame welded to the chassis. Battery disconnect in easy reach, and all positive battery cables out of harms way, enclosed in 1/2 air hose for additional protection. In addition, all the front wiring to the lights, fan, etc. was also installed in air hose inside the frame, to make it disappear. As far as ideal battery locations on the C5, the genius engineers put it right above the ECM, to which sunk a lot of C5's from acid leaking on to it.

Rick_L
04-06-2016, 03:46 PM
I can't wrap my head around putting the battery in an inaccessible or possibly unsafe place. Anyone who's had a car with the battery under the seat or in the fenderwell curses it.

Seems to me that putting it over the rear axle like is being discussed is a very good place.

Bitchin'57
04-06-2016, 06:56 PM
Not everything that auto manufacturers did was smart. Early Jeeps had the gas tank directly underneath the driver's seat. So, does that automatically mean it was a safe spot? I don't think so!
If I was going to do more than just the occasional trip down the 1/4 mile with this car, and it was going to run much quicker than the mid 12's I think it will run, then I'd mount it in the far rear corner of the trunk, on the passenger side. For drag racing, that's the best place. That's where I mounted it in my last street/drag car, but that was a much more serious ride than what I'm building now.

http://hemiduster.com/4sale10.jpg

markm
04-07-2016, 06:18 AM
My 72 Cheyenne Super has the gas tank behind the seat and I think that is a safe place, we all know about the issues they had with my 87 GMC 4x4s, can you say class action lawsuit. My Dads 46 Chevy truck has the tank under the seat. My 55 has the battery in the right rear corner of the truck, I felt that was the ideal location.

55 Rescue Dog
04-07-2016, 06:59 AM
In this article, it claims that simply moving the battery from the front of the car to the rear, is the equivalent to moving the engine back 10 inches, with up to
a 2% change in front to rear weight distribution.
http://www.superstreetonline.com/how-to/additional-tech/0806-turp-hows-and-whys-of-battery-relocation/

chevynut
04-07-2016, 08:06 AM
My folks old 2005 Caddy Deville had the battery under the back seat cushion from the factory without much of a tray.

Yeah, and that sure helps that fine-handling sports car. :p Like I said, they put them where they fit.


It has become increasingly obvious that Cnut has never been a drag racer.

No I haven't, but if I was I'd certainly try to follow the rules:

"Excerpts from the NHRA Rule Book: "8:1 Batteries may not be relocated into the driver or passenger compartments. Rear firewall of .024-inch steel or .032-inch aluminum (including package tray) required when battery is relocated in trunk. In lieu of rear firewall, battery may be located in a sealed .024-inch steel, .032-inch aluminum, or NHRA-accepted poly box. The sealed box may not be used to secure battery and must be vented outside of body. Relocated battery must be fastened to frame or frame structure with a minimum of two 3/8-inch-diameter bolts. Mandatory when battery is relocated, an electrical power cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car body. This cutoff switch must be connected to the positive side of the electrical system and must stop all electrical functions including ignition."

http://www.nhra.com/UserFiles/file/General_Regulations.pdf

It's becoming increasingly obvious that some of you don't follow rules or laws. ;)

chevynut
04-07-2016, 09:10 AM
In this article, it claims that simply moving the battery from the front of the car to the rear, is the equivalent to moving the engine back 10 inches, with up to a 2% change in front to rear weight distribution.

Yeah, it changes it 2% (2") on a 2500 pound car with a 102" wheelbase by moving it into the trunk. It's half that by moving it into the middle of the car.

On a typical 3600 pound 115" wheelbase tri5 it's about 1%. It might be something good to do, but the change is pretty small. If you're trying to optimize everything on race car, it's a move in the right direction. But certainly not the same as moving the engine back 10".

markm
04-07-2016, 02:00 PM
It's becoming increasingly obvious that some of you don't follow rules or laws.

Really, you figured that out all by your self.:)

55 Rescue Dog
04-07-2016, 02:56 PM
It's becoming increasingly obvious that some of you don't follow rules or laws.

Really, you figured that out all by your self.:)
That's Hot Rodding!

chevynut
04-07-2016, 04:09 PM
I just ran through the numbers and assuming a stock tri5 (56 BA sedan) moving the engine back 10" moves the CG back 1.9%. Moving the battery to the trunk directly over the rear axle moves the CG back a little under 1%.

chevynut
04-07-2016, 04:11 PM
That's Hot Rodding!

That's what will be the END of hotrodding, if you piss off the authorities enough by breaking laws. Look at the BS they have to go through in Australia to own a hotrod. Thank God for SEMA.

Bitchin'57
04-23-2016, 12:46 PM
Done.

http://hemiduster.com/lid1.jpg