Fitted Roll Cage

[Blown03SVT]

So I've been scratch building a roll cage for a fire Fighter Mustang II Pro Stock and I am wondering how to get the roll cage to fit tighter to the body as it would in 1:1. I am having difficulty as it is impossible to get measurements from the outside with the interior tub mocked up in the body. Other methods I have tried have been bending beading wire to an approximate shape based on the window and windshield line but have not been successful. I am sure it would be easier if the doors were cut open but thats not were I was heading with this project.

[Jantrix]

In the past I have utilized the kit supplied roll cages, which are often pretty terrible, adding material to it until it fit right and then based my measurements for the new one off that.

[Ace-Garageguy]

Building roll cages that fit tightly in 1:1 cars, where you have plenty of access and can actually get IN the car is difficult and requires careful measurement and skill that comes from experience. Building tight cages in scale models, where access is limited severely, as you noted, is difficult too, and the emphasis is on CAREFUL measurement and repetitive fitting.

I prefer to use styrene rod in the appropriate diameter to represent roll-cage tubes, cold-bent. As Rob mentions above, you'll save yourself a lot of work if you can use some kit-sourced cage elements.

1) First, it's necessary to get the chassis set up so it will always go back in the car body in the same place. EXACTLY. This sometimes requires making temporary stops, locating tabs, pins, or whatever works.

2) Second, start with the rear main hoop. Measuring the approximate height and width to fit up in the body shell, with the right spread at the ends of the legs is easy. Rough bend the hoop and fit it up into the body, adjusting the bends slightly as necessary. Take it out and place the chassis in the body. Mark the inside of the body where the top of the floor will be. Take the chassis back out and re-install your main hoop. Mark the legs a little long, based on the marks you just made for the chassis, and cut them. Tack the hoop in the body (making SURE to keep it symmetrical...this is important for later!!!) Try to fit the chassis back in, and carefully trim the legs as necessary to get a good snug fit, being sure to leave enough headroom for things like the clear runners between front and rear glass (on some models). Take it all apart and glue your roll bar main hoop to the chassis, again MAKING SURE IT'S SYMMETRICAL. When it will support itself enough, slip the body back over the chassis and double check the fit. If it's good, you're done with step 2. Let it dry thoroughly. You'll need it to be stable for the next steps.

3) The next bit is tricky, and you have to decide whether you want to use a front hoop, or side bars that go inside the door shells and tie into upper main longitudinal bars. The techniques are all similar, but you have to fit them to the particular design. Let's assume you want to use a front hoop. Decide where you want it, how high it has to be to carry instruments and steering attachments, then build it pretty much like the rear hoop. Keep it SYMMETRICAL. Let it dry hard.

4) To fit the kinked bars that run from the rear hoop forward just under the roof panel and bend to follow the windshield pillars down to the front hoop, and fitting tight inside the body shell is the hardest bit. The only way I've found that always works, eventually, is you eyeball the whole thing, then bend a tube that looks about right but too long on both ends, and tack it in place. Try to fit the body shell. 1 time out of 20, you'll hit it dead on. If not, just trim to fit better, re-tack, fit...trim to fit better, re-tack, fit...repeat as necessary. There's no real shortcut, because there's no way I know of the get inside the car and make a template like you'd do in 1:1. Just work it until it's right.

5) Once you're satisfied with the fit, take the side bar out before the glue joints get hard. This is where the symmetry you maintained above comes in. If you made your first parts symmetrical and square to the chassis, all you have to do is to copy the side bar you just made, EXACTLY, and glue it in place on the other side of the car. Glue the first side bar back in, and as they set up, continually adjust and keep it all jigged with you fingers so it all drys, again, SYMMETRICAL, with the elements of the side bars parallel to each other.

6) Once all of that is dry, you have all of the hard parts done. Make your lateral and diagonal tubes and braces to fit what's already there, occasionally fitting the body shell to keep everything honest.

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I built everything here ABOVE the kit-sourced side cage elements, including the main hoop, top bars and the rear bracing exactly this way.

Like Jantrix, I'll use kit-supplied cage elements where possible, and modify as necessary. These are generic stock-car side elements fitted to C5-R main frame rails that have been lengthened to the Chevelle wheelbase.

Though the lower part of the cage, the main hoop and the rear bracing fit very well, I didn't take enough time fitting the side upper bars...contest deadline. With another hour's effort, they could have been near perfect, with the downward bend of the upper tube moved a little forward.

Edited June 6, 2013 by Ace-Garageguy

[Blown03SVT]

Bill, I was hoping you would chime in. You always seem to have a tactful and very descriptive way at skinning the proverbial cat. #4 you listed in your post is the main issue I am having, I sort of cheated initially and used most of the kit cage but deleted the halo bar and a-pillar down tubes as they looked sort of like a vintage funny car cage (cube like) rather than a pro stock cage. I should have built it completely from scratch as the kit tubing is .100" and thats the plastistruct rod size I procured to replace the kit sections which seems to be WAY too thick. I am also working around the thickness of the "glass" insert that is probably about 3 scale inches thick so that is affecting the tight fit as well.

This is the most involved roll cage I have ever attempted so bear with me, trying to alleviate starting several other posts dealing with different aspects of the topic. How do you accurately cut the tubing angles for say maiking the x braces that would fit inbetween the two down tubes that run to the back part of the frame? I have a simple miter box, but marking the angle on the tubing and getting them to cut squarely is proving to be challenging.

[Ace-Garageguy]

How do you accurately cut the tubing angles for say maiking the x braces that would fit inbetween the two down tubes that run to the back part of the frame? I have a simple miter box, but marking the angle on the tubing and getting them to cut squarely is proving to be challenging.

Good question. The quickest way I've found to do it (so far) takes a little practice, but works well (after you waste a few too-short pieces). I'll usually cut a brace a little too long, then dress one end to the angle I want to make with a flat-file, and then simulate a fish-mouth on the tube-end with a round needle file.

File-fit-file-fit etc. The other end is the same process, taking a LITTLE off at a time and fitting as you go. File-fit-file-fit. It's really easy to go too far so resist the temptation to rush it. After about 10 or so tubes, it actually goes quite fast.

[Art Anderson]

Of course, a simple pair of "inside" (not sure of the correct term here!) calipers would help in determining the width available on the inside of the model kit body shell for making roll cages that fit more closely to the inner surfaces/contours of the body shell, would they not?

Art

[John Pol]

what I use it wire to make my roll cage once I`m happy with the shape of the wire inside the body.Than I transfer the shape of the wire to plastic rod I hope understand what I`m trying to say.

John Pol

[Ace-Garageguy]

Of course, a simple pair of "inside" (not sure of the correct term here!) calipers would help in determining the width available on the inside of the model kit body shell for making roll cages that fit more closely to the inner surfaces/contours of the body shell, would they not?

Art

Excellent point, Art. Inside calipers (or dividers as they're sometimes called) are the perfect tool to measure up inside the body shell, or even to poke through a window to locate the start of a bend.

The vernier calipers don't work well inside the body because the taper of the long measuring legs will interfere with the rocker panels, and the short, inside-measuring legs are TOO short to get up in the body. They can be very helpful other places though.

(images re-posted from online sources under definition of "fair use" of copyrighted materials)

Edited June 6, 2013 by Ace-Garageguy

[Blown03SVT]

I think I might have a set of those dividers some where from my quartermaster plotting ships position days. Once again you guys amaze me with different clever idea's that I had not thought of. Thanks all

what I use it wire to make my roll cage once I`m happy with the shape of the wire inside the body.Than I transfer the shape of the wire to plastic rod I hope understand what I`m trying to say.

John Pol

John I am thinking something like 16 gauge solid strand would work well, no?

[ScaleDale]

I have calipers similar to the ones posted above and they have a depth gauge that extends from the bottom end for measuring in tight spaces.

My approach is quirky. I scan the drawing from the first page of the instructions or the decal placement page to get a clear side and top view of the car in question. Then I find the factory wheelbase and scale it to 1:25 and set guides at that distance in a PhotoShop document and place the scan into it. Then I resize the scan until the wheelbase of the car matches the guides. Now I have a 1:25 scale image that I can either measure on screen or print and measure for chassis fitting. All that said, roll cage and chassis scratch building will keep one busy for a few days.

As far as gauge/size goes, 1.6 mm (1/16 in)scales up to around 1.6 inches. Standard is something like 1 5/8 inch. That's 1.625 in. A lot of builders go to 2 mm which is scale 2 inches. A tad big.

Dale

[Blown03SVT]

Roger apparently I am not the first person to have been left for wanting with this kits roll cage. I did get it done, its better than the kit piece by leaps and bounds but it could be better. Just practice for the next one I build with the excellent tips you all have shared.

[John Pol]

I think I might have a set of those dividers some where from my quartermaster plotting ships position days. Once again you guys amaze me with different clever idea's that I had not thought of. Thanks all

John I am thinking something like 16 gauge solid strand would work well, no?

Yes it would that way you don`t waste any material to make your roll cage

[rel14]

i turn the body upside down,, build the cage to fit inside the body,, then mount cage to frame,, works for me..

[Mike Kucaba]

I have used a contour tool. It's a group of small wires that push into what shape you want to copy. The wires form to it,

and you tighten the clamp. It's been around for years and most carpenters that do trim usually have one.

[VW Dave]

While this idea was for just an aluminum rod single hoop in a Meyers Manx buggy, it could also apply to a whole cage:

I used index card material to make a template, based on fitting to the model body(and measurements of my 1:1 Manx's roll bar), and I made a rudimentary bending jig with scrap wood from my dining room floor install and a few roofing nails.