cage fabrication equipment advice

For Sale (FS), Want to Buy (WTB), or Free cars or car parts
User avatar
Shenglehoffer
Posts: 31
Joined: Fri Sep 02, 2011 7:31 pm
AntiSpam: No

Re: cage fabrication equipment advise

Post by Shenglehoffer »

The wiser man learns from another mans mistakes...

I have a JD2 model 3 bender and their Notchmaster tubing notcher. I love them both. Swag Offroad makes a "reach around" arm for the notchmaster that allows you to do any angle you want. Don't buy shitty hole saws! Get some nice fine tooth saws from a tool suppler,(mscdirect.com, mcmaster.com), not the crap at Lowes. If you have access to a Bridgeport, a 1.5" endmill makes pretty killer notches too.

Fitment fitment fitment! Tight joints are key to a solid weld, esp. if you are planning on having it tig welded. Your welder will stab you with a hot tungsten if your joints are sloppy. There are some sites on the internets that will print out a coping template based on the angles and dimensions you supply. As geek as you are, this should help you immensely. http://www.metalgeek.com/static/cope.pcgi I cannot remember the other site. Clean the mill scale off the joint area prior to fitment. I like to use 120 grit emery cloth in long strips, 1.5"x20", sand the tube like you're shining shoes all the way around in about a 8" section. Clean the joints with Acetone inside and out prior to tacking.

If you are planning to get a tig welder and tack everything together yourself, food for thought. Amperage for mild steel tubing will be ~1 amp per thousandths of wall thickness +10 amps. 095" A513 tubing, try 115amps. That said, when tacking tubing w/o filler metal, double the amperage and give it a quick full load tack. for 095 wall, I run 220 amps and hit it with a 1ish second tack. Don't ease into pedal, hammer it! It works like a dream.

Find a good metal supplier. I use Marmon/keystone. Not only do they have good stuff, they were nearly 2x cheaper than my old supplier and they deliver it for free. True factory direct. A513 is the designation for DOM carbon steel.

That's all for now.
-Erik
Erik Saunders
Troyer mod (needs a better name)
Death Mod (RIP)
Shenglehöffer E30 (RIP)
Chief Geek
Posts: 302
Joined: Sun Feb 07, 2010 2:36 pm
AntiSpam: No

Re: cage fabrication equipment advice

Post by Chief Geek »

Wow. Thanks everyone. I knew there was plenty of experience out there and, to pull this project off, was counting on people to speak up when I have questions.



Can someone (or several someones) discuss MIG vs TIG for me?

I understand the difference in metalurgy, but I don't have a clue about the "ease of use". In skilled hands, TIG is prettier and can be more ductile (good for absorbing kinetic energy against a tree) but, I don't own skilled hands.

At the moment, my plan is to tack the cage w/ MIG and have a steel fabricator do all the main welding (with MIG). This local fabricator is a father and son team that does all of my custom steel weldments, brackets, and moment frames for the structures of my buildings. Their work is precise, pretty, and I have zero concerns about their welds being at least as strong as my textbooks say. Honestly, it's a shame most of their stuff gets hidden within walls.

But... even with their combined 60+ years of experience and their stated comfort with "thin wall" tubing, I don't know if "welding is welding" or if there are specific gotchas that prevents their experience from being directly applicable. Any advice? I don't have to use them, but if it's low risk, they're convenient and cost effective.



I've collected several hundred images from the web of ideas and joinery to steal. Also, the popularity of spec miata racing means that there are many, many caged miata crash videos on youtube and post-crash pictures. I've been studying these to sniff out any trends or common mistakes.

I've looked at, and decided to pass on, pre-welded cages and cage sections because the need to get them in the car, without cutting the car in half, limits their frontal protection. Also, my car already has a main hoop w/ diagonal and back stays that Eric S. made while Dave E. owned the car. I need to add diagonal to the back-stays and a harness bar to Eric's work, but everything else will be in front of that.

There are pre-cut, pre-notched kits available, but melding those parts with an existing cage seems sketchy. Odds are, things won't fit.



One thing spec miata crash videos have revealed is that, apparently, it's legal in the SCCA to have door bars mounted to the door. There are several instances of the doors being ripped open and the door bars are clearly mounted on the door's hinges or on their own.

The Miata has a small door opening and neither Rich nor I are gymnasts (nor the size of a gymnast), but my door bars are going to be fixed to the rest of the cage. (Probably wouldn't pass the Don-and-Walter-test any other way.)


Thanks again.
Last edited by Chief Geek on Fri Dec 06, 2013 10:56 am, edited 1 time in total.
"Christina", New #13/#55x, '90 Miata: In progress
"Keiko", Old #13x/#55x, '96 Miata: R.I.P.
Daily Driver: '11 Mazda2 (small cars... some men have nothing to compensate for)
User avatar
sdwarf36
Posts: 822
Joined: Thu Dec 30, 2004 6:06 pm

Re: cage fabrication equipment advise

Post by sdwarf36 »

If you have a cage you don't need to run the roof. That should make easier to get in + out of.
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
Chief Geek
Posts: 302
Joined: Sun Feb 07, 2010 2:36 pm
AntiSpam: No

Re: cage fabrication equipment advice

Post by Chief Geek »

sdwarf36 wrote:If you have a cage you don't need to run the roof. That should make easier to get in + out of.
True, but my plan was to keep the roof. Dry, shaded, and heated sounds more comfortable.

I did notice that in serious spec miata crashes the roofs often come off. Because of this, my plan is to create something to function like a window net for the roof so if I totally screw up, I get to keep my arms. Maybe metal mesh, aluminum sheet metal, or a re-purposed window net. Thoughts?

Speaking of, I see pictures IMSA and Lemans GT cars with a triangular net thing running from behind the drivers right shoulder to the dash. It looks like window net material but is clearly shaped for specifically for this job. Is this to prevent dislocated shoulders while your arms are flailing around during your 14th barrel roll? It looks too far away and too low to support the drivers head.

Paul
Last edited by Chief Geek on Fri Dec 06, 2013 10:56 am, edited 1 time in total.
"Christina", New #13/#55x, '90 Miata: In progress
"Keiko", Old #13x/#55x, '96 Miata: R.I.P.
Daily Driver: '11 Mazda2 (small cars... some men have nothing to compensate for)
User avatar
sachilles
Posts: 1189
Joined: Thu Jun 26, 2003 3:11 pm
Location: Waitsfield, VT

Re: cage fabrication equipment advise

Post by sachilles »

Chief Geek wrote:
sdwarf36 wrote:If you have a cage you don't need to run the roof. That should make easier to get in + out of.
True, but my plan was to keep the roof. Dry, shaded, and heated sounds more comfortable.

I did notice that in serious spec miata crashes the roofs often come off. Because of this, my plan is to create something to function like a window net for the roof so if I totally screw up, I get to keep my arms. Maybe metal mesh, aluminum sheet metal, or a re-purposed window net. Thoughts?

Speaking of, I see pictures IMSA and Lemans GT cars with a triangular net thing running from behind the drivers right shoulder to the dash. It looks like window net material but is clearly shaped for specifically for this job. Is this to prevent dislocated shoulders while your arms are flailing around during your 14th barrel roll? It looks too far away and too low to support the drivers head.

Paul
http://www.safedrives.com/proddetail.as ... SafeSolC5R
Sachilles
02 Subaru impreza (Donut) #66
Chief Geek
Posts: 302
Joined: Sun Feb 07, 2010 2:36 pm
AntiSpam: No

Re: cage fabrication equipment advice

Post by Chief Geek »

Thanks.

Are these "driver nets" intended to do the same job as the seats with full head supports (like the seats in #25 & #33)?

I've checked and there's no way I can get a full-head-support seat into the car. Well, maybe the seat would fit, but I'd never be able to fit through the remainder of the door opening. Might have to think about one of these.

If it were close to the driver and mounted to the cage, would the window net begin to perform the same function?
Last edited by Chief Geek on Fri Dec 06, 2013 10:57 am, edited 2 times in total.
"Christina", New #13/#55x, '90 Miata: In progress
"Keiko", Old #13x/#55x, '96 Miata: R.I.P.
Daily Driver: '11 Mazda2 (small cars... some men have nothing to compensate for)
User avatar
sachilles
Posts: 1189
Joined: Thu Jun 26, 2003 3:11 pm
Location: Waitsfield, VT

Re: cage fabrication equipment advise

Post by sachilles »

I think their intent is to contain the whole occupant, whether it be head, arms or whatever.
Walter probably has more real info than I can offer.

My wild ass guess is that, it can support the driver in a number of ways including if the seat fails(or it's mounts). I like the idea of them, as I don't have a containment seat.
Sachilles
02 Subaru impreza (Donut) #66
User avatar
walterclark
Posts: 1442
Joined: Sun Feb 08, 2009 12:57 pm
Location: Dover, MA.
Contact:

Re: cage fabrication equipment advise

Post by walterclark »

The inside triangular net is there mostly to limit head and upper torso movement in a side impact and to help guide them back toward the seat. They are triangular to allow access to the shifter, handbrake, etc on the bottom and reduce visual impairment to the right thru the windshield.

If you look at that Simpson "15 minutes..." video at around 45 seconds in the driver hits something and is thrown to his right. You can see the head and shoulder containment in this seat simply bend (or break) out of the way. I guess they might have slowed him down while absorbing that first impact, but what happens if he hits something else? I dont know what seat that was but it looks like something made of aluminum and none too sturdy. One of those nets would have been good there.
The older I get the better I was.
Chief Geek
Posts: 302
Joined: Sun Feb 07, 2010 2:36 pm
AntiSpam: No

Re: cage fabrication equipment advice

Post by Chief Geek »

Being that I have a bad disk in my neck, I'm taking a conservative approach.

Roy's accident sold me on the NexGen head restraint. After some research and watching the Simpson video, I'll be installing a side net on my right. Because Miata doors seem to open and come off regularly in Spec Miata races, my window net will be mounted to the cage (not the door).

Does anyone know how to provide the same functionality as a side net for my left side?

My first choice would be something that will still work with no door at all.

Paul

PS The amount of driver movement in the Simpson video is amazing. I guess this explains why I've seen F1 mechanics with a 4' long, pole that has a slot in the end and a t-handle at the other. The driver threads the end of the shoulder strap through the slot and a burly mechanic leans down hard on the top of the T to gain great leverage tightening the straps.
"Christina", New #13/#55x, '90 Miata: In progress
"Keiko", Old #13x/#55x, '96 Miata: R.I.P.
Daily Driver: '11 Mazda2 (small cars... some men have nothing to compensate for)
User avatar
walterclark
Posts: 1442
Joined: Sun Feb 08, 2009 12:57 pm
Location: Dover, MA.
Contact:

Re: cage fabrication equipment advise

Post by walterclark »

You should see some of the crash test videos...You would be amazed at how much a properly restrained driver moves in an impact. People look at Don and I like we are crazy when we tell them to put cage padding here or there in places their helmet cant reach while they are strapped in. We have seen some of the videos, and race crash investigators have shown helmet impacts in places on the cage that you would not think someone would be able to hit and still be alive. Those belts stretch a LOT - which is what they are supposed to do. They are also weakened. And that is why we say to replace them after each crash when there was impact that may have stressed them. When I was chief scrutineer at RNY I used to cut belts involved in a crash to ensure they would not be reused. I got endless crap for that, and teams sometimes went to the trouble of collecting the car and getting out of Dodge before I could see it to avoid a post crash tech and things like cutting belts or describing the damage to the cage in their logbook, which exactly why I did it. Those belts WOULD be reused otherwise.

Anyway...

A standard window net, mounted to the side (door) bar and upper side bar (or halo) will do that. It should be mounted so its under tension when clipped in and ideally have rods top and bottom to spread any load and keep it evenly flat otherwise. Most places that sell window nets also sell a kit with rods, weld on tabs for the rods, clips for 3 corners and usually something like a "GM seatbelt buckle" for the 4th corner. The tabs weld to your cage and obviously you either have to get lucky or have the net while you are fabricating the cage to be able to locate that door bar at the right height.

Image
Image

An alternative to welding the tabs to the door bar - say if the bar is too low or at an angle - is an extension kit for the lower rod that lets you pick a pair of spots lower on the cage to anchor the bottom net rod and then reach between them with straps or steel cables.

Image

There are even complete packages like this from Schroth:

Image
The older I get the better I was.
Post Reply