Senior Design project, Roll Cage - JeepForum.com
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post #1 of 72 Old 11-12-2008, 08:01 AM Thread Starter
Scotch740
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Senior Design project, Roll Cage

I am in my final year of school at ODU and we have to do a senior design project. I am planing on designing a roll cage. I am looking for information on the design of cages for offroad vehicles or race cars. Looking for information on forces, regulations, design ideas, ect. If anyone knows of a published source I can use I would appreciate it. Unfortunately I don't think the "*Official* Cage idea/pic/discussion thread" would count as a reference.


Here is a very rough outline I have prepared. Feel free to toss out more ideas.

Introduction:
I. What is a Roll Cage
II. Why is it needed
III. Stock Roll cage

Discussion:
I. Intended use
a. Off-road
b. Rollovers

II. Parts of a roll cage
a. Different bars (links)
b. Gussets
c. Seat and restraint mounting
d. Frame tie ins.
III. Design

IV. Materials
a. Types of tube
b. Size
V. Construction methods
a. Welding
b. Bending
c. Bolt in Links

Summary and Conclusion:
I. Purpose and Use
II. Main points of design, materials, and construction
III. Improvements over Stock Roll cage

References:
Appendices:

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post #2 of 72 Old 11-12-2008, 08:08 AM
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Have you checked the WEROCK or Jeepspeed sites/rules?

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post #3 of 72 Old 11-12-2008, 08:18 AM
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Werock rules

Quote:
Originally Posted by WEROCK
6.15: Roll bars/Cages
W.E.Rock considers the cage as the safety bars surrounding the driver. Cages must be designed
to protect the occupant in the event of a rollover.
The following are roll bar/cage guidelines for competition:
6.15.1: Six (6) point mounting cages covering the driver are required.
6.15.2: OEM bars are approved for a portion of the roll cage.
6.15.3: Handles are required on the interior portion of the roll-cage or vehicle.
6.15.4: Round steel tubing (D.O.M Preferred) 1.5” O.D with 0.095” wall is compulsory for the
basic roll cage. Aluminum and/or soft metals are not permitted. Roll bar construction must be
welded. A W.E.Rock official must approve roll cages made of other material or in other wall
thickness/diameters.
6.15.5: Connection positions of the roll cage must tie in to the frame of the vehicle; Body mounts
are considered a tie in point.
6.15.6: The front-most position must be no farther toward the rear of the vehicle than fifteen (15)
inches behind the throttle and brake pedals.
6.15.7: The Cage must have a space no wider than 24” above the driver’s head, and at least 1
spreader bar between the front main bar and rear main bar are required unless the cage top is
24” wide or less.
6.15.8: Gussets must be welded in the four corners of the “halo”. Gussets may be tubing or plate
steel.
6.15.9: A minimum of.040 magnetic expanded or flat sheet metal, or 1/8” aluminum, must cover
the area immediately over the driver seat and be welded or bolted to the roll cage. Steel tubing
must surround the roof panel.
6.15.10: W.E.Rock recommends a spreader bar to be mounted under the dash area to connect
the right and left “A” pillars.
6.15.11: If doors are not ran, a bar running from the “B” pillar, at approximately shoulder height, to
the “A” pillar, at approximately shin height, must be ran. This can be a bolt in piece.
6.15.12: A “periscope bar” may be no longer than 12” above the “halo” bar. This may be used as
an attaching position for tow straps.
6.15.13: Cage height must be a minimum of 3 inches from the entire helmet of the driver
6.16: Seating
The following are seating guidelines for competition:
6.16.1: All W.E.Rock approved seats must have padded rib protectors and seat leg extensions on
the left and the right side.
6.16.2: Adequately padded headrest or neck support acceptable to W.E.Rock official inspectors
is required.
6.16.3: Single seat configurations acceptable.
6.16.4: Seats must be mounted to the roll cage. Mounting to the body is not permitted.
6.16.5: An approved Five-point harness is mandatory and must be worn at all times while on an
obstacle.

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post #4 of 72 Old 11-12-2008, 09:58 AM
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Quote:
Originally Posted by scotch740 View Post
Here is a very rough outline I have prepared. Feel free to toss out more ideas.

I'd also put a "loads" section in there. All the discussion points you have listed are steering you towards the main factor in the design - what are the loads that the structure is expected to see? Loads are the starting point for all structural design and analysis.

I think automotive standard for rollovers is something like a 2 gee load. You might want a discussion in there saying that a slower speed vehicle might need a cage designed for 2 gees, but a high speed desert racer would need a 4 or 6 gee cage. But for it to be a good design project, you have to settle on a number.

You should also include a section on the definition of success. You're probably not going to design the cage to keep stresses below material yield, but to a deflection criteria that limits cage intrusion to the passenger area.

There's probably some SAE literature on rollover protection standards - if you find a good paper in pdf, post it here!
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post #5 of 72 Old 11-12-2008, 11:14 AM Thread Starter
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I have seen the W.E. ROCK rules, but will check out the jeep speed rules also.

Good point about the loads, I can believe I left that out. I will be doing stress analysis's on the cage so knowing the loads will be very important.
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post #6 of 72 Old 11-12-2008, 12:13 PM
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Check SCCA's website. Check NASCAR's website. Check IMSA's website.

Basically, Google "race sanctioning body" and check their website for cage rules. If you need x number of published references, these sanctioning bodies publish hard copies of their rules as well.

I'm pretty sure that Googling "books on roll cage design" would yield some books for you to cite.
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post #7 of 72 Old 11-12-2008, 02:55 PM
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Quote:
Originally Posted by scotch740 View Post
Good point about the loads, I can believe I left that out. I will be doing stress analysis's on the cage so knowing the loads will be very important.
The more you can define your problem statement, the easier it is to do the design and analysis.

You can probably make some simplifying assumptions to reduce the number of load cases too. I think normally, rollover design assumes that all load acts through the vehicle CG, and that the vehicle is impacting a flat surface.

If you're intending this cage for crawling, you could also study some pictures and video of rockcrawler rollovers (sure are enough of them out there). Try to estimate velocity and orientation at impact. You might find typical motorsport cage specs aren't suited for crawling.. who knows.
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post #8 of 72 Old 11-12-2008, 04:36 PM
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This is from SCORE Internationals rule book.

CR33 Roll Cages
All vehicles in competition except Motorcycles and ATV’s must be equipped with a roll cage. Minimum design and tubing size based on seamless 4130 chromoly tubing or ASTM 1018/1026 CDS/DOM. No aluminum or other non-ferrous material permitted.

Material

Material for roll cage construction must be 4130 chromoly tubing or ASTM 1018/1026 CDS/DOM.
All welding must be of the highest quality with full penetration and no undercutting of the parent metal. All welds shall conform to the
American Welding Society D1.1, Structural Welding Code, Chapter 10, Tubular Structures and Standards for the material used (see AWS. Org). It is strongly recommended that the welder inspect all welds using Magnaflux™, die-penetrate, or other effective methods.
All tubes must be welded 360-degrees around the circumference of the tube.
No oxy-acetylene brazing or welding allowed. Good external appearance of a weld does not necessarily guarantee its quality, poor looking welds are never a sign of good workmanship.
None of the tubing may show any signs of crimping or wall failure. All bends must be mandrel type. The center radius of the bends may not be less than three (3) times the outside diameter of the roll cage tubing.
It must be emphasized that the use of heat-treated or high carbon steels may cause problems and that bad fabrication may result in a decrease in strength (caused by brittle heat-affected zones), inadequate ductility and internal stress.
Roll Cage Tubing Sizes
For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver. Note: There is an allowance of minus 0.010 inches on all tubing thicknesses. Minimum tubing size for the roll cage is:

Up to 2000 lbs. - 1.500” x 0.095” CDN/4130/Seamless or ASTM 1018/1026 CDS/DOM
2001 - 2500 lbs. - 1.500” x 0.120” CDN/4130/Seamless or ASTM 1018/1026 CDS/DOM
2501 - 3000 lbs. - 1.750” x 0.095” CDN/4130/Seamless or ASTM 1018/1026 CDS/DOM
3001 - 4000 lbs. - 1.750” x .120” CDN/4130/Seamless or ASTM 1018/1026 CDS/DOM
Over 4000 lbs. - 2.000” x 0.120” CDN/4130/Seamless or ASTM 1018/1026 CDS/DOM
Construction Procedures
Cages must be securely mounted to the frame or body and gusseted and braced at all points of intersection. Cab or body mounted cages must not be attached to the body structure by direct welding, but must be bolted through and attached by the use of doubler plates (one on either side) with a minimum thickness of .187”, see Figure 4. Where bolt and nuts are used the bolts shall be at least .375” diameter SAE Grade 8 or equivalent. Roll cage terminal ends must be located to a frame or body structure that will support maximum impact and not shear.

Minimum material dimension requirements for roll cages apply to the following members of the roll cage:

Front and rear hoop
Front and rear interconnecting bars
Rear down braces
Lateral bracing
Elbow and door bars
Lower A-pillar tubes, and lower B-pillar tubes
Roll Cage Design
All roll cages must be constructed with at least one (1) front hoop (top of cage to floor), one (1) rear hoop (top of cage to floor), or two (2) lateral hoops, two (2) interconnecting top bars, two (2) rear down braces and one (1) diagonal brace and necessary gussets, see Figure 1. If front and/or rear hoop terminate at elbow/door bar, lower A-pillar and/or B-pillar must be made of same tubing size as roll cage. Upper main, front, rear, and lateral rollbar hoops must be made in one piece without joints. Centerlines of all required tubes must converge at intersections.

Any vehicle that is not provided with stock steel doors for its driver and co-driver must be equipped with sidebars, at least one on each side that will protect the occupants from the side. These bars must be parallel to the ground (or as close to parallel as is practical) and be located vertically in relation to the occupants to provide maximum protection without causing undue difficulty in entering or exiting the vehicle. The sidebars must be formed of tubing of the same material and dimensions as the roll cage itself and must be securely attached to the cage’s front and rear members. Additional side tubes may be required to limit cockpit intrusion, these additional tubes must be of the same size tubing as the roll cage. Tubes must be placed in such a manner as to limit openings adjacent to the occupants. Maximum opening size in this area is limited to 370 square inches.

All roll cage bars must be at least 3” in any direction from the driver and co-driver’s helmets while they are in their normal driving positions.

Gussets must be installed at all main intersections on the main cage including diagonal and rear down braces, and where single weld fractures can affect driver’s safety. Gussets may be constructed of .125” X 3” X 3” flat plate, split, formed and welded corner tubing, or tubing gussets the same thickness as the main cage material, see Figure 2 and Figure 3. Rear down braces and diagonal braces must angle no less than 30 degrees from vertical.

An inspection hole of at least .187” diameter must be drilled in a non-critical area of the roll bar hoop to facilitate verification of wall thickness. It is the prerogative of SCORE to drill a second hole if deemed necessary.

Any cage or chassis that has been built after January 1, 2006 must be identified by means of an identification plate affixed to it by the manufacturer; this identification plate must be neither copied nor moved (i.e. embedded, engraved or self destroying sticker). The identification plate must bear the name of the manufacturer, a serial number, and the date of manufacturer.

Head/neck restraints designed to prevent whiplash are required on all vehicles. These restraints must be a headrest of approximately 36 square inches, with a resilient padding at least 2” thick. Any portion of the roll bar or bracing which might come in contact with the helmet must be padded.


Roll Cage and Vehicle annual inspection

All vehicles must have their cages approved prior to racing in a score event. The inspection will be preformed at the Score Technical office. After passing inspection and paying Inspection fees all vehicles will receive a Score I.D. tag, that is to remain with the vehicle at all times. If tag is removed or lost vehicle must be re-inspected and retagged. Any modification to an approved cage may render its approval invalid, and may need to be re-approved. All repairs to a roll cage damaged after an accident must be re-approved by SCORE International.


All vehicles built before January 1, 2006 may be required to have an inspection every six months.

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post #9 of 72 Old 11-12-2008, 06:12 PM
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you may also mention windshields are an integral part of many factory 'roll cages', aka the passenger cabin. all windshields have a unique manufacturing property where the outer surface of the glass is in tension, the center is in compression and the other outer surface is in tension, then the plastic laminant. they acheive this through specific cycles of heating and tempering. if you're a mechanical engineer, its kinda neat. most vehicles with a curved windshield (especially smaller cars) are actually designed to use the windshield as part of the A-pillar to support the vehicle in rolls and crashes. because of that unique tempering process, combined with the laminant, the glass can support lots of force for short instances until it shatters, then the laminant keeps it together. this property also prevents cracks in your windshield if the crack doesn't go past the tension section (a crack in tension won't spread, but one in compression will)

You can also look at different college SAE Formula race teams - they have to meet specific design specs.

try Google Scholar and Web of Science for journals. To get to stuff like you're looking for, you will need to search for crash data. Try researching NHTSA & IIHS crash testing, military testing, aircraft, trains, military transport, etc. I'm guessing most of the articles of interest will be pretty old. You can also tie in the metalurgy of welding, and how the heat effects the steel - the weld is far stronger than the bulk steel, but the neighboring bulk steel directly next to the weld point is significantly weakened by the heat...and therefore the common failure point. Most of the newer journals you will find are all materials science related...carbon nanostructures and their mechanical properties have been all the rage for the past 10-15 yrs.

also if you have access to Solidworks and COSMOSWorks, you can use the 'pipe' feature to make nearly any configuration of Schedule 40 you want, then custom edit the material properties to be DOM, and bingo...you've got an FEA of a roll cage done in an hour or so.


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post #10 of 72 Old 11-13-2008, 01:11 AM
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Here's a couple quick Yahoo hits. You should also check out Barnes & Noble, etc. I was there today and they had a couple of chassis design books (not to mention a killer welding book - WAY better then any other I've seen) in the automotive section!

http://www.amazon.com/Racing-Sports-.../dp/0837602963

http://www.amazon.com/dp/1557880557?...89&camp=211189

http://search.barnesandnoble.com/Fou...18157/?itm=118



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post #11 of 72 Old 11-13-2008, 05:46 AM
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Hey man, looks like the guys dug up a bunch of info for ya already, but I just wanted to say as an Alum of ODU's engineering dept... good luck on it!

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post #12 of 72 Old 11-27-2008, 11:40 PM
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You should post your paper when you're done. I found a decent cage rules site here if you're still looking-
http://www.therangerstation.com/tech...y/rollcage.htm
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post #13 of 72 Old 11-28-2008, 06:03 PM Thread Starter
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Some good info surfacing on here. I do plan to post the paper and design for you all to tear apart. The project is suppose to take place in Spring 09, so some time around May 09 I should have it done. If the prof ever responds to me about approval

The actual construction will be at a later date and probably vary from the projects design a little. Mostly for function as a daily driver.

Please post up anything you guys know of. I went to order some of those books only to get an Email a week later saying they were out of stock so I got to reorder.
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post #14 of 72 Old 04-05-2009, 08:15 PM Thread Starter
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Well graduation is getting closer so guess I should start working on this.
Actually I have been busting my brain all semester to learn Inventor and have gotten pretty decent.

Here is the "stock" version. Yes, it is not stock because it has front pillar bars but it represents the stock cage where the windshield would be.


Here is the Finite Element Analysis, FEA done on it. The loading is a vector 2000lbs horizontal and 2000lbs vertical resulting in that black arrow you see on the corner. The analysis contours show the factor of safety. The deflection shown is not the actual but just represents the direction.



Here is what I am working on to do an FEA on.









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post #15 of 72 Old 04-05-2009, 08:39 PM
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Dude that has to be the most complex roll cage I have ever seen


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