Something got me thinking, most people who have read my post outlining the chassis reinforcements done to my Terminator while I'm sure most find it interesting are saying to themselves "this is all fine and dandy but how is any of this of benefit to me? Someone bringing up the topic for a 500 mega joule ignition system for a mod motor from my perspective has no basis in reality or perhaps why I should buy a Bugatti Vayron which will never happen. What I will address here are steps you can take in a fairly well equipped shop that go beyond what the aftermarket can offer without going overboard like I did
After what I have been through I know every nook, cranny and sheet metal structure in this car and there are some things you can do to stiffen the chassis in a more practical manner then what has been done on my car. My engineering position has me solving the problems everyday and if I screw-up bad enough in my line of work puts my livelihood in jeopardy and perhaps my employer as well which is the last thing I want. In this business reputation is everything! If I'm not sure of what I'm doing I find someone who “is” and I tell my boss I'm a bit out of my league on this one.
One thing that needs to be said is please forgive me for my writing style. My posts tend to read more like a technical manual which can be very “dry” at times but there is a good reason for that as I want to be as clear as possible with minimal ambiguity. I can't help that I've been programmed to write like that and my employers like it that way as Joe Fridays says “just the facts mam”.
Having said that I will add 2 post on this thread what can be done in a practical manner to improve the stiffness of both an SN95 coup and the other posts will cover the vert. This will go beyond adding sub-frame connectors or strut tower braces. Keep in mind you could do more harm then good if you are not giving careful consideration on the dynamics involved. This will include anti-corrosion steps needed after welding were certain areas will not be accessible after the work is done. What is fine in So Cal won't cut it in Seattle Washington or New England even if you don't drive it on wet roads. Aluminum oxide “sleeps”, iron oxide doesn't according to Neal Young.
Keep this in mind, these are just suggestions on how someone might want to take their SN95 chassis to the next level regarding stiffness but does so at their own risk. I take no responsibility for what others do to their cars. Read this as “reference only” and modify things as you see fit. Even if you have no plans on doing any of this you can still gain a new perspective on the chassis structure which applies to any car not just the Mustang
A few basic ground rules and equipment needed:
Metal: Only use 4130 chromolly steel, no low carbon mild steel with the number “10” in it's alloy designation like 1018 which is in the 30K psi tensile strength range vs. 130K psi for 4130. The reason for this is you can use thinner and lighter stock to achieve the same strength. Aircraft Spruce sells it for a reasonable price vs. most industrial suppliers or McMaster-Carr.
Patterns: Make patterns from cardboard then transfer the shape to the sheet metal using a sharpie. Using this method will result in an oversize part that can be ground with an abrasive wheel or air tool to fit closely to the feature you want to reinforce. Don't worry about gaps as long as they are not too big the welder can fill those in. Label each pattern and include LH and RH designations as required. Lots of the patterns I made worked on both sides. After you transfer the pattern to the sheet metal label it using a bold black sharpie so you know where it goes after it's been cut to shape.
Transferring the pattern to the sheet metal: It's best to get a get a bunch of cardboard patterns made and then arrangement on the sheet metal to maximize the yield while minimizing waste. If you have long straight sections use the outside edge of the sheet which for that piece will save you some cutting time, Always consider how the blade cut will enter the sheet and how you can minimize the cut before the blade reaches the pattern to minimize cutting time. You can drill a hole if you need to start a cut that not close to an edge or to cut an edge that bends to sharp for the blade to negotiate.
Weld type: MIG weld only, plain old arc welding results in a messy oxidized beads, TIG welding won't fill-in the gaps as well and will take twice as long.
Primer: Use “weld thru primer” on the surfaces you won't have access to after your done welding that section like a closed box. I have been very impressed with how well this type of paint holds-up after being exposed to so much heat. You will need to grind off the paint directly where the weld bead is going to be laid. You can get this at most automotive body supply stores
Surface abrasion: Buy a box of coarse (red) 3M Scotch and use brake cleaner on everything before painting and welding.
Metal thickness: plan on using mostly .050 thick 4130, .040 thk is the minimum you can easily MIG weld, .060 starts to get heavy but is useful in higher stressed areas, .090 - .125 where you really need streangth but that gets heavy us it sparingly. Welding thick steel is much easier than thin sheet metal. If you don't have experience welding sheet metal find someone who is or you will make a mess of things. If you have a welder come in a do the job like I did do as much of the fitting a prep work as possible. The welder just wants to attach metal to your car and wants to get in and out with minimal delays. If your brackets are sloppy or not prepped (cleaned , painted and masked) it will slow him down but a good one will make sure the job is done right.
Welding sequence: Weld parts to the chassis in a symmetrical fashion. Chances are the majority of the brackets will have both left and right hand parts. Don't weld-up one side of the car and let it sit there for a week then come back and weld the other side. By then the chassis a cooled, shrunk and taken a “set”. Weld a few parts on the LH side then weld the same RH parts to maintain even geometry on both sides of the chassis
Cooling: Use a wet rag to cool the welded panel immediately after the welder has finished attaching a part to the chassis or half way thru a long bead. Sheet metal is thin in the “Z” plain but it's going to be much longer in the “X” and “Y” plain meaning it will expand in 2 directions way more then the third. Long panes may start to warp and bow if not cooled in a timely manner. This is what happened to my rocker panels but the shop was able to remove most of it. Maximum heat transfer works best when the wet rag is folded in a neat fashion as opposed to having it bunched-up in a ball. Rotate the rag on the hot panel often as the moisture soaks up the heat like a sponge. Towels work best as they can hold a lot of water. The rag should be wet enough but does not drip all over the place. A rag that is merely “moist” won't absorb the heat very well which may result in warping. Have an outside faucet close buy to to cool the rag and replenish it will water as need be, The colder the better.
Avoid quenching the metal while cooling: Be careful placing a cool wet rag too quickly on a red hot surface. You don't want to “quench” the metal making it harder. If there is a red hot panel I will dab it to slow down cooling process once its no longer red hot I will place the rag directly on the panels and cool it down while flipping the rag over once that side is saturated with heat which only takes a few seconds.
Warping: Sheet metal sucks with regard to heat propagation and cools very quickly due to the fact the heat path is very thin in relationship to the surface area exposed to ambient temperature. Just keep in mind that it expands like crazy in the X & Y planes and not the Z which is the thickness.
Ambient temperature: Avoid welding sheet metal in very cool ambient temperatures like in the winter. Ice cold metal will expand at a much greater rate then if welded during the summer and there is more thermal shock involved. August in a good time to do this. Avoid January sheet metal welding which create all sorts of thermal expansion dynamics. If the water used to cool the rag comes out of the tap rather warm just open it up and swing it back and forth even on a hot day evaporation will cool it below ambient.
Bio-metric thermometer: The threshold for thermal pain on the human body is approximately 120° F if you can touch a surface and leave your finger on it without having to yank it away generally means the surface is 120° F or less.
Drain holes: Be mindful of the need for drain holes or sloping features what will allow water to purge itself after a rain storm or car wash. The ability for the structure and vent the moisture away is important
Grinding welds: Don't ground the weld bead flush to the surface of the panels just to make them look good. Leave some excess weld to over lap the joint and avoid over grinding the metal. We welded in some gussets inside the front windshield cavity where the windshield wiper arms are housed under neath the front wind shield. Afterwords I went to to get us both lunch and upon my return to my horror the welder took the initiative and decided to grind the welds flush yet managed to work himself into a trance and ground the beads about .010 below flush. I freaked out what was taking place and stopped him immediately. What he didn't realize he was grinding metal that was only .032” thick meaning it lost whopping 30% of the metal thickness which by that time was about the thickness of fingernail and is now harder to weld without blowing big holes in the metal. I ended up having to place thin strips of steel on both sides of the gusset where it was over ground to prevent the welder from blowing thru the metal. This was an honest mistake but under no circumstances are you to overlook flaws such as this. Can you imagine finishing the car only to find out the welds are cracking because they are too thin allowing rain water to intrude inside the vehicle which will rust out the floor boards and what's involved in correcting it? Mistakes are one thing stupidity is another. He apologized and the problems was corrected. I make mistakes right along with the best of them but its way better to acknowledge them and take corrective action before they turn into big problems.
Plasma cutter a big “no no”:Don't use a hand held plasma cutter to cut out the brackets. They harden the edge of the metal to the point it will turn a metal saw blade to dust just touching the surface.
Jig saw: The best method for cutting the metal is to use a jig saw. The best blades to is are Skill metal jig saw blades. The 18 TPI (med) is best for cutting 4130. The 36 tpi will cut but is too fine, slow and will dull quickly. The 14 TPI will work but is too coarse and will dull quickly as well. Buy lots of blades. Don't over heat the blade. Have 2 pieces of thick flat aluminum close by when cutting the metal. Stop before you “blue” the blade then quickly sandwich it between by squeezing both sides with the aluminum while pulling the blade out from the saw exposing the maximum amount of blade to cool which happens very quickly.
You can also use a band saw but those blades tend to be rather wide and not as good cutting sharper curbs which can over heat the blade
Abrasive cut-off wheel: These are faster then the jig saw when you have straight section to be cut. I buy the 4 1/2” right angle electric grinder from Harbor Freight Tools for $20-30.
Welding wire: Plan on using mostly #30 or #35 wire
Grinding abrasives: The green 3M 2” sanding discs are the best and last a long time. I prefer to by a box of 25 which is about $50. 24 or 36 grit is best for fast cutting. 80-120 are best for surface prep
Hearing protection: Get a set of over-the-ear hearing protection. Sheet metal drums like crazy ans is very loud
Eye protection: I need reading glasses which won't fog up like full coverage goggles will. Use common sense here
Sliver removal: I bought a real sharp precision tweezers from a swap meet and have a jewelers eye piece handy on the shelf all the time. Even if you get the tiniest shard of metal in your finger the eye piece and tweezers will make short work of it.
Fire protection: I needed this a few times as sparks will fly. A dual halon works best and doesn't leave white powder all over the place so there is nothing to clean up. Have it in a hand place where you can get to it quickly and always put it back in the same place so you won't having to think about where it is where you need it in a hurry. Halon just sucks-up the oxygen out of the air and is absolutely brutal on fires you will only need a quick burst to extinguish most fires. Cardboard works pretty good protecting items for the welding splatter. DO NOT USE CLOTH OF ANY KIND I made the mistake of covering the dash pad with a towel when welding in the back of the car and a spark jumped over landing on it. The fine thread burned invisible until I saw the heat plume in the corner of my eye before I yanked it off but by then I was too late. Beware of having paper towel around a welder. A spark land on that stuff will smolder as it consumes the paper often you will smell it before seeing it.
Corrosion protection: Keep in mind exposed bare metal after everything is welded will start to rust. Here the weld-thru primer is your friend if you are welding a flat piece of metal over a flat section of the metal in the chassis like the top of the shock towers paint the underside of the metal before you weld the two together. If your welding to a section like the rocker panels and won't be able to access it to clean and paint you may not want to weld to that area. Living in So. Cal of Arizona is not as much of a concern but if you live in a wet and humid climate you will want to put some thought to were you can weld and where you don't want to weld if you cant clean and paint it. I used a cold zinc galvanizing spray paint from McMaster car in hard to reach places and self etching primer on places I could reach. I there are places of bare metal with surface rust you can apply metal prep which is phospharic acid mixed with water which will turn the rust into an inert substance with will naturalize the corrosion process which can be painted later. I'm a real stickler with corrosion protection and you should be to.
Wire brushes: Have an assortment of wire brushes which can be chucked onto a cordless drill and 1/4” drill extensions of various lengths to clean the welds. A flexible 1/4” drill shaft comes in handy as well. A dremel with a flexible shaft comes in real handy for tight corners as well. Harbor Freight sell a nice assortment of bits dremel for a bargain price of $20 last time I checked.
Ball peen hammer: The welder will need this to hammer some of the panels to shape.
Access to a bend or box brake: This will be needed to put folds in some places where you might needed it. I often will bend a 90° lip in an edge which makes it super stiff. 4130 can be a real tough is the bend is too long or the metal too thick. When that happens I use my 20 ton arbor press and one of the bending dies off my brake. Here you will learn just how tough chromolly steel is. I use a 36” Harbor Freight bend brake from Harbor Freight which comes in real handy around the shop
Masking tape: 3M 1” and 3” wide used to tape patterns and cut finished brackets to the car, to protect surfaces from the grinder and to use for long straight guidelines you can easily see for cutting with the abrasive wheel.
Repainting to factory finish: Keep in mind you are going to want to repaint the visible areas you will see where the paint has been ground-off or burned away. This will primarily be in the engine compartment. The area in the fender wells, interior, undercarriage and the trunk won't be visible and won't require accurate color matching.
Patients: if you don't have much of this it may not be something you want to do depending on the extent of work you plan on doing. Don't start something you can't finish you better off leaving well enough alone
If this hasn't scared you off by now then that is a good start. Keep in mind this gets addicting once you see the progress being made you are going to start looking downstream of where you welded and want to do more. You need to resist this and stick to your plan. You will start to look at the chassis structure in a different way. When I'm in a shop I look at how the various car manufactures piece there cars together looking at details most others don't notice. Being a mechanical engineer helps but it's certainly not a requirement if you know the fundamental principals of geometry, loads and how they interact. It will change the way you think about this kind of stuff and will learn a great deal about chassis structures but it's a lot of hard work getting there. If you keep your goals simple and within reason you can make improvements to the chassis where no others have without cutting up the car and adding a multi-point roll cage that more or less renders the car useless of the street, will be hidden from view, will tighten-up the cars handling, reduce raddling and reduce chassis structure fatigue and in an extreme case such as mine will transmit more hp to the real wheel not having the engine to twist and hold the chassis in torsion like a rod of rubber.
As stated I will break this up into two categories one to address the SN95 coup and another for the vert but will be a much simpler and practical version of what been done with my car but will use that for a basis of discussion.
After what I have been through I know every nook, cranny and sheet metal structure in this car and there are some things you can do to stiffen the chassis in a more practical manner then what has been done on my car. My engineering position has me solving the problems everyday and if I screw-up bad enough in my line of work puts my livelihood in jeopardy and perhaps my employer as well which is the last thing I want. In this business reputation is everything! If I'm not sure of what I'm doing I find someone who “is” and I tell my boss I'm a bit out of my league on this one.
One thing that needs to be said is please forgive me for my writing style. My posts tend to read more like a technical manual which can be very “dry” at times but there is a good reason for that as I want to be as clear as possible with minimal ambiguity. I can't help that I've been programmed to write like that and my employers like it that way as Joe Fridays says “just the facts mam”.
Having said that I will add 2 post on this thread what can be done in a practical manner to improve the stiffness of both an SN95 coup and the other posts will cover the vert. This will go beyond adding sub-frame connectors or strut tower braces. Keep in mind you could do more harm then good if you are not giving careful consideration on the dynamics involved. This will include anti-corrosion steps needed after welding were certain areas will not be accessible after the work is done. What is fine in So Cal won't cut it in Seattle Washington or New England even if you don't drive it on wet roads. Aluminum oxide “sleeps”, iron oxide doesn't according to Neal Young.
Keep this in mind, these are just suggestions on how someone might want to take their SN95 chassis to the next level regarding stiffness but does so at their own risk. I take no responsibility for what others do to their cars. Read this as “reference only” and modify things as you see fit. Even if you have no plans on doing any of this you can still gain a new perspective on the chassis structure which applies to any car not just the Mustang
A few basic ground rules and equipment needed:
Metal: Only use 4130 chromolly steel, no low carbon mild steel with the number “10” in it's alloy designation like 1018 which is in the 30K psi tensile strength range vs. 130K psi for 4130. The reason for this is you can use thinner and lighter stock to achieve the same strength. Aircraft Spruce sells it for a reasonable price vs. most industrial suppliers or McMaster-Carr.
Patterns: Make patterns from cardboard then transfer the shape to the sheet metal using a sharpie. Using this method will result in an oversize part that can be ground with an abrasive wheel or air tool to fit closely to the feature you want to reinforce. Don't worry about gaps as long as they are not too big the welder can fill those in. Label each pattern and include LH and RH designations as required. Lots of the patterns I made worked on both sides. After you transfer the pattern to the sheet metal label it using a bold black sharpie so you know where it goes after it's been cut to shape.
Transferring the pattern to the sheet metal: It's best to get a get a bunch of cardboard patterns made and then arrangement on the sheet metal to maximize the yield while minimizing waste. If you have long straight sections use the outside edge of the sheet which for that piece will save you some cutting time, Always consider how the blade cut will enter the sheet and how you can minimize the cut before the blade reaches the pattern to minimize cutting time. You can drill a hole if you need to start a cut that not close to an edge or to cut an edge that bends to sharp for the blade to negotiate.
Weld type: MIG weld only, plain old arc welding results in a messy oxidized beads, TIG welding won't fill-in the gaps as well and will take twice as long.
Primer: Use “weld thru primer” on the surfaces you won't have access to after your done welding that section like a closed box. I have been very impressed with how well this type of paint holds-up after being exposed to so much heat. You will need to grind off the paint directly where the weld bead is going to be laid. You can get this at most automotive body supply stores
Surface abrasion: Buy a box of coarse (red) 3M Scotch and use brake cleaner on everything before painting and welding.
Metal thickness: plan on using mostly .050 thick 4130, .040 thk is the minimum you can easily MIG weld, .060 starts to get heavy but is useful in higher stressed areas, .090 - .125 where you really need streangth but that gets heavy us it sparingly. Welding thick steel is much easier than thin sheet metal. If you don't have experience welding sheet metal find someone who is or you will make a mess of things. If you have a welder come in a do the job like I did do as much of the fitting a prep work as possible. The welder just wants to attach metal to your car and wants to get in and out with minimal delays. If your brackets are sloppy or not prepped (cleaned , painted and masked) it will slow him down but a good one will make sure the job is done right.
Welding sequence: Weld parts to the chassis in a symmetrical fashion. Chances are the majority of the brackets will have both left and right hand parts. Don't weld-up one side of the car and let it sit there for a week then come back and weld the other side. By then the chassis a cooled, shrunk and taken a “set”. Weld a few parts on the LH side then weld the same RH parts to maintain even geometry on both sides of the chassis
Cooling: Use a wet rag to cool the welded panel immediately after the welder has finished attaching a part to the chassis or half way thru a long bead. Sheet metal is thin in the “Z” plain but it's going to be much longer in the “X” and “Y” plain meaning it will expand in 2 directions way more then the third. Long panes may start to warp and bow if not cooled in a timely manner. This is what happened to my rocker panels but the shop was able to remove most of it. Maximum heat transfer works best when the wet rag is folded in a neat fashion as opposed to having it bunched-up in a ball. Rotate the rag on the hot panel often as the moisture soaks up the heat like a sponge. Towels work best as they can hold a lot of water. The rag should be wet enough but does not drip all over the place. A rag that is merely “moist” won't absorb the heat very well which may result in warping. Have an outside faucet close buy to to cool the rag and replenish it will water as need be, The colder the better.
Avoid quenching the metal while cooling: Be careful placing a cool wet rag too quickly on a red hot surface. You don't want to “quench” the metal making it harder. If there is a red hot panel I will dab it to slow down cooling process once its no longer red hot I will place the rag directly on the panels and cool it down while flipping the rag over once that side is saturated with heat which only takes a few seconds.
Warping: Sheet metal sucks with regard to heat propagation and cools very quickly due to the fact the heat path is very thin in relationship to the surface area exposed to ambient temperature. Just keep in mind that it expands like crazy in the X & Y planes and not the Z which is the thickness.
Ambient temperature: Avoid welding sheet metal in very cool ambient temperatures like in the winter. Ice cold metal will expand at a much greater rate then if welded during the summer and there is more thermal shock involved. August in a good time to do this. Avoid January sheet metal welding which create all sorts of thermal expansion dynamics. If the water used to cool the rag comes out of the tap rather warm just open it up and swing it back and forth even on a hot day evaporation will cool it below ambient.
Bio-metric thermometer: The threshold for thermal pain on the human body is approximately 120° F if you can touch a surface and leave your finger on it without having to yank it away generally means the surface is 120° F or less.
Drain holes: Be mindful of the need for drain holes or sloping features what will allow water to purge itself after a rain storm or car wash. The ability for the structure and vent the moisture away is important
Grinding welds: Don't ground the weld bead flush to the surface of the panels just to make them look good. Leave some excess weld to over lap the joint and avoid over grinding the metal. We welded in some gussets inside the front windshield cavity where the windshield wiper arms are housed under neath the front wind shield. Afterwords I went to to get us both lunch and upon my return to my horror the welder took the initiative and decided to grind the welds flush yet managed to work himself into a trance and ground the beads about .010 below flush. I freaked out what was taking place and stopped him immediately. What he didn't realize he was grinding metal that was only .032” thick meaning it lost whopping 30% of the metal thickness which by that time was about the thickness of fingernail and is now harder to weld without blowing big holes in the metal. I ended up having to place thin strips of steel on both sides of the gusset where it was over ground to prevent the welder from blowing thru the metal. This was an honest mistake but under no circumstances are you to overlook flaws such as this. Can you imagine finishing the car only to find out the welds are cracking because they are too thin allowing rain water to intrude inside the vehicle which will rust out the floor boards and what's involved in correcting it? Mistakes are one thing stupidity is another. He apologized and the problems was corrected. I make mistakes right along with the best of them but its way better to acknowledge them and take corrective action before they turn into big problems.
Plasma cutter a big “no no”:Don't use a hand held plasma cutter to cut out the brackets. They harden the edge of the metal to the point it will turn a metal saw blade to dust just touching the surface.
Jig saw: The best method for cutting the metal is to use a jig saw. The best blades to is are Skill metal jig saw blades. The 18 TPI (med) is best for cutting 4130. The 36 tpi will cut but is too fine, slow and will dull quickly. The 14 TPI will work but is too coarse and will dull quickly as well. Buy lots of blades. Don't over heat the blade. Have 2 pieces of thick flat aluminum close by when cutting the metal. Stop before you “blue” the blade then quickly sandwich it between by squeezing both sides with the aluminum while pulling the blade out from the saw exposing the maximum amount of blade to cool which happens very quickly.
You can also use a band saw but those blades tend to be rather wide and not as good cutting sharper curbs which can over heat the blade
Abrasive cut-off wheel: These are faster then the jig saw when you have straight section to be cut. I buy the 4 1/2” right angle electric grinder from Harbor Freight Tools for $20-30.
Welding wire: Plan on using mostly #30 or #35 wire
Grinding abrasives: The green 3M 2” sanding discs are the best and last a long time. I prefer to by a box of 25 which is about $50. 24 or 36 grit is best for fast cutting. 80-120 are best for surface prep
Hearing protection: Get a set of over-the-ear hearing protection. Sheet metal drums like crazy ans is very loud
Eye protection: I need reading glasses which won't fog up like full coverage goggles will. Use common sense here
Sliver removal: I bought a real sharp precision tweezers from a swap meet and have a jewelers eye piece handy on the shelf all the time. Even if you get the tiniest shard of metal in your finger the eye piece and tweezers will make short work of it.
Fire protection: I needed this a few times as sparks will fly. A dual halon works best and doesn't leave white powder all over the place so there is nothing to clean up. Have it in a hand place where you can get to it quickly and always put it back in the same place so you won't having to think about where it is where you need it in a hurry. Halon just sucks-up the oxygen out of the air and is absolutely brutal on fires you will only need a quick burst to extinguish most fires. Cardboard works pretty good protecting items for the welding splatter. DO NOT USE CLOTH OF ANY KIND I made the mistake of covering the dash pad with a towel when welding in the back of the car and a spark jumped over landing on it. The fine thread burned invisible until I saw the heat plume in the corner of my eye before I yanked it off but by then I was too late. Beware of having paper towel around a welder. A spark land on that stuff will smolder as it consumes the paper often you will smell it before seeing it.
Corrosion protection: Keep in mind exposed bare metal after everything is welded will start to rust. Here the weld-thru primer is your friend if you are welding a flat piece of metal over a flat section of the metal in the chassis like the top of the shock towers paint the underside of the metal before you weld the two together. If your welding to a section like the rocker panels and won't be able to access it to clean and paint you may not want to weld to that area. Living in So. Cal of Arizona is not as much of a concern but if you live in a wet and humid climate you will want to put some thought to were you can weld and where you don't want to weld if you cant clean and paint it. I used a cold zinc galvanizing spray paint from McMaster car in hard to reach places and self etching primer on places I could reach. I there are places of bare metal with surface rust you can apply metal prep which is phospharic acid mixed with water which will turn the rust into an inert substance with will naturalize the corrosion process which can be painted later. I'm a real stickler with corrosion protection and you should be to.
Wire brushes: Have an assortment of wire brushes which can be chucked onto a cordless drill and 1/4” drill extensions of various lengths to clean the welds. A flexible 1/4” drill shaft comes in handy as well. A dremel with a flexible shaft comes in real handy for tight corners as well. Harbor Freight sell a nice assortment of bits dremel for a bargain price of $20 last time I checked.
Ball peen hammer: The welder will need this to hammer some of the panels to shape.
Access to a bend or box brake: This will be needed to put folds in some places where you might needed it. I often will bend a 90° lip in an edge which makes it super stiff. 4130 can be a real tough is the bend is too long or the metal too thick. When that happens I use my 20 ton arbor press and one of the bending dies off my brake. Here you will learn just how tough chromolly steel is. I use a 36” Harbor Freight bend brake from Harbor Freight which comes in real handy around the shop
Masking tape: 3M 1” and 3” wide used to tape patterns and cut finished brackets to the car, to protect surfaces from the grinder and to use for long straight guidelines you can easily see for cutting with the abrasive wheel.
Repainting to factory finish: Keep in mind you are going to want to repaint the visible areas you will see where the paint has been ground-off or burned away. This will primarily be in the engine compartment. The area in the fender wells, interior, undercarriage and the trunk won't be visible and won't require accurate color matching.
Patients: if you don't have much of this it may not be something you want to do depending on the extent of work you plan on doing. Don't start something you can't finish you better off leaving well enough alone
If this hasn't scared you off by now then that is a good start. Keep in mind this gets addicting once you see the progress being made you are going to start looking downstream of where you welded and want to do more. You need to resist this and stick to your plan. You will start to look at the chassis structure in a different way. When I'm in a shop I look at how the various car manufactures piece there cars together looking at details most others don't notice. Being a mechanical engineer helps but it's certainly not a requirement if you know the fundamental principals of geometry, loads and how they interact. It will change the way you think about this kind of stuff and will learn a great deal about chassis structures but it's a lot of hard work getting there. If you keep your goals simple and within reason you can make improvements to the chassis where no others have without cutting up the car and adding a multi-point roll cage that more or less renders the car useless of the street, will be hidden from view, will tighten-up the cars handling, reduce raddling and reduce chassis structure fatigue and in an extreme case such as mine will transmit more hp to the real wheel not having the engine to twist and hold the chassis in torsion like a rod of rubber.
As stated I will break this up into two categories one to address the SN95 coup and another for the vert but will be a much simpler and practical version of what been done with my car but will use that for a basis of discussion.
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