I built a cage in a Miata recently and I thought some folks here might be interested in seeing the process.
The car is a D Prepared autocross car. A local autocrosser recently purchased the car more or less in the condition seen here. He wants a full cage so he can remove the windshield (already done), for safety, and so he can take it to the track if he feels like it.
The first step is to figure out the height of the main hoop and front hoop. The rules say that "...a straight line drawn from the top of the main hoop to the top of the front hoop shall pass over the driver’s helmet..." The Hard Dog roll bar that came with the car made this job easy. The wooden broomstick is in the location of the front hoop.
With that done, it's time to remove the Hard Dog bar and get to work. Next step: mounting plates for the main hoop and door bars:
More progress to follow. I'll keep this updated daily, or close to it.
What is the deal with the no windshield? Is it so they can see better? Does it make the car faster? I would think the open cockpit would cause more air turbulance. Looking forward to more pictures.
It takes a lot of confidence I guess to start cutting away on a car--especially someone elses car, but your past work puts that concern to rest. I'm jealous as heck of your abilities Doug. Thanks for sharing this cage build and all the rest you've shared over the years..
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09:01 AM
sonic50 Member
Posts: 3873 From: All over the USA Registered: Aug 2004
Wasn't the windshield a structural safety feature on those?
Looking forward to the rest of the build
Thank you.
I looks like the windshield added some chassis stiffness and some rollover protection. The cage will stiffen things up way beyond what the windshield did, and the rule I quoted above ensures that the driver is well protected in a rollover. The intent is that the driver's head should never touch the ground.
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Originally posted by Jake_Dragon:
What is the deal with the no windshield? Is it so they can see better? Does it make the car faster? I would think the open cockpit would cause more air turbulence. Looking forward to more pictures.
Thanks!
You would not believe what a difference removing the windshield makes. You get so used to windshield pillars that you don't realize how much view they block until they're gone. You know that feeling you get when you jump into a convertible and you look around and you have zero blind spots? Without a windshield it's like that for the front, too. Very nice.
As for the turbulence, the windshield is an enormous amount of drag because it punches a very large hole in the air. I talked with a gentleman that road raced an X1/9 several years ago and if I remember correctly he said he picked up about 10 mph at the end of the front straight of his home track when he removed the windshield. This Miata is primarily an autocross car and will be less effected because of lower speeds. Still, the rear deck will get paneled in to reduce some drag there.
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Originally posted by maryjane:
It takes a lot of confidence I guess to start cutting away on a car--especially someone elses car, but your past work puts that concern to rest. I'm jealous as heck of your abilities Doug. Thanks for sharing this cage build and all the rest you've shared over the years..
Thanks for the compliment, that's very kind of you. To be perfectly clear, the owner removed the windshield before I got the car. There is plenty of cutting left, though, as you'll see.
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Originally posted by sonic50:
Good luck with the build. Can't wait to see more photos.
Scott
Thank you! Here's the next step.
The main hoop mounting plates are welded in place, and the main hoop is bent and tacked in place.
Very nice! Although I have to admit it kind of makes me want to see the car get rolled just to see how well it holds up!
Hey now, don't be wishing any bad luck on my customers.
Now the hard part. Making the front strut tower braces. This is difficult because you only get one chance to drill the correct hole in the firewall. After spending a couple hours with a ruler, straight edge, level, plumb bob, and calculator, I bullseyed the left one:
I made mounting boxes where the tubing hits the front strut towers. If you're trying to figure out the perspective on the photo below, the camera is above the cowl at the rear of the engine and is looking at the left front strut tower. Those capped off brake lines are where the master cylinder used to be. It needed to be removed for welding access.
The strut tower braces are also finalized in shape and length, and are tacked in place.
Oh, and I have a small question... I happened to be looking at the Fiero cage section, and I saw that your prices had doubled. Is this because of materials, or were you just not charging enough? I was just wondering, because I know that prices of raw materials has taken a huge leap since Katrina. Keep up the good work.
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01:56 PM
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Oh, and I have a small question... I happened to be looking at the Fiero cage section, and I saw that your prices had doubled. Is this because of materials, or were you just not charging enough?
Good question.
Although steel prices have been continually increasing over the past few years, the reason is primarily the second one - I wasn't charging enough before. Building one of the 6 point bars takes 20 - 30 hours so at my shop rate of $50/hr that's $1000 - $1500 that I have invested in labor, not even including materials. As the shop is getting busier I can't afford to spend time on projects where I only end up making $10-15/hr (or less!). I will eventually cease making mail order Fiero roll bars / roll cages altogether because the car I have been using as a jig will get turned into a race car. In the meantime, though, they're still available, but they have to be viable from a business standpoint.
Nice work, when you build something with your own two hands and can stand back at the end of the day and say look I made that. I would love to work in a weld shop again, I welded for 15 years and miss it.
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08:53 PM
Mar 13th, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Although steel prices have been continually increasing over the past few years, the reason is primarily the second one - I wasn't charging enough before. Building one of the 6 point bars takes 20 - 30 hours so at my shop rate of $50/hr that's $1000 - $1500 that I have invested in labor, not even including materials. As the shop is getting busier I can't afford to spend time on projects where I only end up making $10-15/hr (or less!). I will eventually cease making mail order Fiero roll bars / roll cages altogether because the car I have been using as a jig will get turned into a race car. In the meantime, though, they're still available, but they have to be viable from a business standpoint.
Make sense?
Alright, thanks for clearing that up... Makes perfect sense, I was just curious why you had doubled your prices in jut a few months time. Thanks Doug!
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03:27 PM
Mar 15th, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
When you have multi-tube junctions, the notches can get interesting. The picture below is the notch in the rear of the top door bar (shown above) where it meets the main hoop and harness bar:
When you have multi-tube junctions, the notches can get interesting. The picture below is the notch in the rear of the top door bar (shown above) where it meets the main hoop and harness bar:
Yep, been there, done that. WITHOUT one of them angled tubing cutters. All figured, cut, & finished by torch and hand grinder. Had a lot of waste leftover. Nothing as complex as what you are doing though!
Alot of people don't realize just how many manhours go into the construction of a R.O.P.S. I don't think I would do it for sale. People FREAK when you tell them how much! (allmost ALL in manhours)
The work you are doing is some of the best I've seen. I don't think those joints could BE any tighter! Nice!
I use to build these things before I got into computers. The legs are as tall as I am. Scrubber These are about as tall as my leg Cyclones
Man if I keep looking in here I will be out cutting up my car this weekend
Hmm... swinging off topic in the off topic section... that sure looks a lot like how the Dyson vacuums work... I suspect their patents wouldn't hold up in court after seeing those.
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09:26 PM
Mar 16th, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Hmm... swinging off topic in the off topic section...
I don't mind getting off topic in my off topic thread as long as it's interesting. Those cyclone air cleaners are cool. A friend and I talked about making something like this as a part of a two stage air filter for my rally car.
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Originally posted by Boondawg:
Yep, been there, done that. WITHOUT one of them angled tubing cutters. All figured, cut, & finished by torch and hand grinder. Had a lot of waste leftover. Nothing as complex as what you are doing though!
Alot of people don't realize just how many manhours go into the construction of a R.O.P.S. I don't think I would do it for sale. People FREAK when you tell them how much! (allmost ALL in manhours)
The work you are doing is some of the best I've seen. I don't think those joints could BE any tighter! Nice!
A torch? Wow. I use a tubing notcher to do the initial cuts. They still often have to be fine tuned with a bench grinder / angle grinder / die grinder, but I bet this still saves a lot of time over a torch. You are quite right about the amount of hours that go into something like this. LOTS.
So moving on with more on the same topic, here's my favorite notch in the whole cage. This one is on the center diagonal. This piece shares the load of the front strut tower braces and transfers it to the rest of the cage:
The interesting notch is where meets the door bar, main hoop, and harness bar. Looks simple from this angle, right?
Here's what it looks like without the other tubes. Kinda cool, eh?
A torch? Wow. I use a tubing notcher to do the initial cuts.
A torch was all I had. And like I said, lots of mistakes and waste. The end products was NOTHING as fine as what you're doing! All mine was for construction equipment. Not preatty, and never tested in a rollover. Although a huge boulder did fall on one of mine while I was in it. It held, with narry a cracked weld. Quite a bend, though.
Compare your work to Eddie Van Halen. I'm Tiny Tim.
Who would you rather hear play?!
[This message has been edited by Boondawg (edited 03-16-2006).]
The Cyclones were great. They were used to control dust, we could suck up cotton balls and baby powder and none of it would come out the clean side. It would all end up in the bucket at the bottom. I always wondered why they were not used in other operations. We had one over our cut off saw, it would drop the metal dust into a bin and vent the air out side of the building. No filters just the cyclone, it was about twice the size of the one in the picture and made out of steel. The scrubber was the same thing. Water and paper came in and swirled around keeping the paper dust in the bottom but letting the clean air out the top. I had a lot of fun building those and a lot of other stuff. Too bad they closed the door, I would love to moon light and make some side money.
I had a press to notch the pipe for our hand rails, 90 and 45 only. It worked but I could do just as well with a grinder.
Those cyclone air cleaners are cool. A friend and I talked about making something like this as a part of a two stage air filter for my rally car.
You see this alot on construction machinery and ag tractors etc. For certain applications your filter can get completely clogged in as little as 100 hours without them. I could definetly see a rally car as one of those applications.
At Caterpillar we call them Dust Ejectors. I havn't disected one yet but somehow the exhaust gas is used to create the cyclone from a 2" tube off the muffler.
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10:20 PM
PFF
System Bot
Mar 17th, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Man, that is one sturdy cage! There's that much car there? And to think, if everything goes right, it will never be used!
Looking at the structual quality of your work, thank god the ones I did on equipment were never put to the test! I don't think they would have done their job! They did protect my head from falling trees and rocks, though!
[This message has been edited by Boondawg (edited 03-17-2006).]
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02:03 PM
Mar 19th, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
Looking at the structual quality of your work, thank god the ones I did on equipment were never put to the test! I don't think they would have done their job!
Actually this cage doesn't look bad at all. Everything (almost) is triangulated. Triangles are very strong structures. The Miata cage looks a lot more sexy because it's not as square as the one you posted, but yours looks like it should be pretty strong. I'm guessing the person sits in the middle of it facing towards the left side of the picture?
Another thing that makes a difference in strength is tubing quality, size, and thickness. For the Miata cage I used DOM (drawn over mandrel) tubing. It's fairly strong tubing for various reasons. See http://www.steeltubeinstitute.org/domprocesses.htm if you're interested. The tubing used in this car is 1.5" OD x 0.095" wall thickness. This is dictated by the rules and is based on the weight of the car. For larger, heavier cars the requirements go all the way up to 1.75" x 0.120" wall tubing.
If you get a chance, could you include a close-up of one of your welds on one of the multi-angle cuts? I have always had problems keeping up my flow when changing angles.
Ofcourse, i'm still burning with sticks...............
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04:05 PM
Mar 20th, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
If you get a chance, could you include a close-up of one of your welds on one of the multi-angle cuts? I have always had problems keeping up my flow when changing angles.
Ofcourse, i'm still burning with sticks...............
I dug through all my pictures of this build and I don't have any weld close-ups. Once the owner gets the car finished and brings it out to race I'll get some more photos.
Here the driver's side door bars are bent and tacked in place, along with a brace for the a-pillar bar:
I am now done making tubes but the cage isn't done yet. At this point the cage is just tacked together so there is lots of welding to do. Then some interior reassembly is needed. Stay tuned. We're almost there.
Now it's time to weld it all up. There are some places where it is difficult or impossible to weld all the way around a tube. The solution? . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . Weld everything possible while it's in the car, then take it out of the car and weld up the rest.
There are some places where it is difficult or impossible to weld all the way around a tube. The solution? take it out of the car and weld up the rest.
And that was what I was wondering when I was asking about keeping my flow going around all them weird cuts. I did mine already mounted on the equipment. Yes, it sucked!
But next time........................
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05:38 PM
Mar 22nd, 2006
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
And that was what I was wondering when I was asking about keeping my flow going around all them weird cuts. I did mine already mounted on the equipment. Yes, it sucked!
I hear you. I was able to cheat on a lot of the welds by removing the cage from the car, but some, like the strut tower braces (front and rear) and the lower door bars had to be done in the car. That means lying on my back with my head crammed into the footwell and welding above me. It sounds like you know the drill.
This brings us to our last installment. It's time for the finishing details. These were pretty simple on this car because it's so stripped down.
- Before the left front shock tower brace gets welded in place I had to make a slight modification so the brake booster isn't trapped in place. You can see why this was needed in this picture.
- I also needed to move the location of the throttle cable (because of that same bar) and modify the pedal to work with the new location. Forgot to get pictures of that.
- Then re-install the master cylinder, bleed the brakes, and re-route the fuel pump wire.
- The steering wheel needed to be hung, as did the gauge panel:
- The wiring bar (under the right side of the dash) also had to be hung since it was displaced by the bar that goes through the firewall there. You can sort of see it in this picture:
And then it went home:
Here's how the parts tally worked out:
21 pieces of tubing 13 bends 4 tubing ends were flat, square cuts 6 tubing ends were flat, angled cuts 2 tubing ends were rounded, angled cuts 30 tubing ends were notched, and many of these were angled, too
10 mounting plates 6 were simple plates 4 were boxes made out of three pieces each
As you can see, there's more to building a cage than bending a couple tubes.
