CJDave... Is this what you mean by sill? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 08-23-2000, 01:02 PM
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CJDave... Is this what you mean by sill?

CJDave,

Is this what you mean by the sill? It is red in the picture. It will follow the contour of the step and be attached to the frame viw brackets, sandwiching the body.

Just want to be sure.

Once, again. <font color=blue> I might not be the fastest buffalo in the heard, but at least the lion hasn't caught me yet. </font color=blue> [img]/wwwthreads_images/icons/wink.gif[/img]

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post #2 of (permalink) Old 08-23-2000, 02:37 PM
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Re: CJDave... Is this what you mean by sill?

[img]/wwwthreads_images/icons/smile.gif[/img] We are only using the vertical half of that shape. The roll bar has it's own pads which sit flat on the floor and through-bolt to the thick piece below in just the two spots. The strength that we were looking for is SECTIONAL for the downthrust, hence the vertical section only.[img]/wwwthreads_images/icons/smile.gif[/img] Boy.....those are nice graphics.[img]/wwwthreads_images/icons/wink.gif[/img]

CJDave
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post #3 of (permalink) Old 08-23-2000, 05:47 PM
 
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Re: CJDave... Is this what you mean by sill?

We do just what he showed in the modified cars, then re-enforced the frame with heavy angle iron for the tubes to weld to .

That is just SO close to exactly what I described!!

You do REALLY good work, even from my abstract descriptions!!
You have REAL talent. No question about it.

I like the extra side bars on top. Looks like a good idea.
As for the top of the back 'X' brace on the main hoop....
I think you could drop it even with the down and back legs for some more of the head clearance you suggested, and add gussets, and I don't see why it would be any weaker...

If a guy was going hill climbing, I'd want a vertical tube right straight up from the back 'X' to the hoop.
Not necessary for slow speed roll over protection, but might be a good idea if the potential for violent and repeated landings on the top of the top of the cage on a hill side littered with big rocks, I'd add it.

What are the chances of that if you aren't rock climbing or hill climbing...

I'd go trail riding almost anywhere with the design you have right now!!
That really looks strong, and it looks real good too.



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post #4 of (permalink) Old 08-23-2000, 06:01 PM
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Re: CJDave... Is this what you mean by sill?

[img]/wwwthreads_images/icons/crazy.gif[/img] OK......let's get crazy here. HOW ABOUT taking a HUGE round tube section and putting four bends in it. Beginning on the floor behind the driver, it goes up at a slight angle toward the rear like the stock bar does, then it lays over and levels out towards the FRONT.....goes along the top edge of the window....then it turns 90 degrees and goes crosswise just behind the top edge of the windshield....then another 90 toward the rear and another more-than-90 bend to get back down. Install the top "X" to keep the rocks out, install the rear angle tubes to the fenders, and an "X" in the space just back of the seats. Make this bar HEAVY......like maybe .250 wall....and forget trying to shoehorn the front vetical bars in around the dash. I noticed that some heavy equipment is that way, to allow more egress for the operator....a CANTILEVERED top cage.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #5 of (permalink) Old 08-23-2000, 07:41 PM
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Re: CJDave... Is this what you mean by sill?

If I may comment - The drawing is amazing! Wish I had real computer skills, and software that I understood. My comment, I like the gussetts, except....my brother in law, who has built many cages for Off-Road racing, suggests that if you are to use gussetts made of plate steel they should not be inserted where your drawing shows them. This type of plate steel gussett, while sufficient to achieve the desired triangulation, should be either on top or on the bottom of the adjacent tubes. When placed in the plane they are shown in your drawing they could "slice" into the primary roll bar tubing. Some folks have used a smaller diameter piece of tubing (most often 1" diameter)and it may just punch through the larger cage pieces in a severe crash. Using a section of tubing (maybe 3-4 inches in length) equal to the diameter of the primary bars is preferred. Fish-mouthing them to fit is a bit of a hassle but they are far superior. Food for thought, not meant as criticism. John

post #6 of (permalink) Old 08-23-2000, 11:47 PM
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Re: CJDave... Is this what you mean by sill?

That does look good!! but if you need those gussets, it probably would be a good idea to use a flat square and weld to the top or bottom of the bars instead of in the middle - one piece to cover all four of the angles at the X.

Doug '97 TJ
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post #7 of (permalink) Old 08-27-2000, 03:45 PM
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Re: CJDave... Is this what you mean by sill?

How about covering the top with heavy guage sheet metal? This would protect the passengers when rolling over in sand or mud and help in rocks, too.

post #8 of (permalink) Old 08-27-2000, 09:12 PM
 
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Re: CJDave... Is this what you mean by sill?

Heavy gauge sheetmetal for a roof on the cage would put a whole lot of weight way, way up high and probably cause more rolls than its worth. This cage isn't for high-speed work, so the design should be sufficient enough already...

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post #9 of (permalink) Old 08-27-2000, 09:54 PM
 
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Re: CJDave... Is this what you mean by sill?


SHEET METAL..... Not plate steel!!
It wouldn't add three pounds...

I have never seen a gusset punch through a bar.
I have seen crashes bad enough to tear the bar in two after the gusset, I've seen the tubes smashed flat against the gussets and the gusset not punch through.
I have seen the cage get caught on something and pull it corner to corner tot he point of the bars failing, and not pull the gussets apart or punch them through the bar.

I have seen gussets welded on top of the bar.
When you apply force, the weld on the gusset tears the bar open, but the gusset doesn't fail.

I'm not nuts about having the bars torn open, so I do it in the middle, unless it's a joint you need two gussets on, then it's top and bottom.

In racing, you normally only have one really hard knock on the cage, then some smaller ones, so the tubes torn open may not be too much of an issue.....
BUT....
If I were hill climbing, and there was the potential for the vehicle to roll down the hill for 500 feet, then I think that having a tube torn open on the first bounce would be a bad thing...

If you put them on the top, put one on the other side of the joint, and fill in between them to reinforce them.

This here is the other view point...

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post #10 of (permalink) Old 08-27-2000, 11:58 PM
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Re: CJDave... Is this what you mean by sill?

OK - I've been watching and learning and admiring in this ROPS theme in several threads. I am humbled by this board and never cease to be amazed at the depth of discussion.

Anyway - I have built sand rail buggies. Several of them as well as various trailers. The reason I mention trailers is that I HATE extra heavy trailers. Build them light and strong and it'll be easier to STOP! To build them and sand rails light you have to use good injuneerrun principles. I am not an engineer but I do listen when I talk to one and I learn as I am doing here. My other qualification to contribute at this point is that I have done a double high speed endo in a sand rail I designed and built. I walked away with my companion in the crash-and-didn't-burn who was my son (nine years old at the time) with out an injury other than the deep bruises from the a)seatbelt - across the hips, b) the shoulder straps - over both shoulders and c) the helmet straps - under our chins. The crash was semi-serious at least in that we went from about 55 mph to 0 in a measured 43 feet on effectively flat wet sand.

1) First things first. Stretch! Belted in (4 point 4" x 2" Simpson harness) with helmet, the top of the helmet was at least 2-1/2" from the overhead fore-and-aft spreader. There were on the SIDE of the helmet, down at least 3" vertical dimension, brown marks on the white. The brown was from the metallic paint on the frame and the white is the color of the helmet. Makes for good tattletale evidence. (I probably wouldn't be writing this now if I hadn't had a helmet on that day - maybe I'd just be babbling)(don't take that and run with it!) Now I don't know how much is more or less than the others but here is what we all need to learn from this as I see it now - years later. a)Frames, roll cages, and elements of each STRETCH and MOVE! b)Seat belts and related parts STRETCH and MOVE! c)Body parts STRETCH and MOVE! - this is so important I want to say it again - body parts STRETCH and MOVE! - especially the long ones - like your spinal assembly! YOU HAVE TO HAVE CLEARANCE AND PROTECTION FROM YOUR ROPS!!!! Sorry for the yelling but I learned a lot from my experience and am simply emphasizing a point. Use common sense when designing and use padding when building.
2)The roll bar design was conventional but I had added a personal touch which was a plexiglass (dark bronze to match the metallic brown of the rail) top between the rails and bars of the top. It was glued in place with silicone around the edges and held by some small tabs at the corners. I'm giving this detail to give you all some idea of the value of what TR just said about sheet metal between the spreaders overhead. The plex held. Laterally, diagonally, in plane and out of plane. The frame flexed so much the 1/4" bead of silicone was fractured which means crushed. But the frame was not deformed here. The frame was seriously compromised elswere, though! Filling in the space between the bars and spreaders with something with strength is amazing in a crash. Mine was PLASTIC and it's contribution to the mix cannot be overemphasized!
3)The cantilevered top cage was used by some friends of mine for their sand rails some 25 years ago. Some of them were roll tested. ALL of them held. It is an effective design in my opinion. All of them I am familiar with did have a lightweight, angled brace at the front, however.

None of this is exactly scientific but I can add one more thing that I have learned from engineers who have worked for me on projects entirely unrelated to anything automotive: light weight is good. Light weight is GOOD! Overbuilt is more mass and that means more power of destruction when the roll does happen!

JM2CW!

sln

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