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I'm a safety professional that has operated numerous farm tractors and backhoes with front loaders, large all-terrain forklifts, graders, dump trucks, skid loaders, mining equipment, etc. I have investigated numerous fatal 'accidents' involving heavy equipment, some of which has easily exceeded 50 tons. This has included some instances where hydraulic valves jammed and caused backhoes or loaders to move to full travel, ultimately flipping the tractor or leading to a loss of control or some other serious problem. I have also designed and built roll cages and seat/seat belt setups for everything from sprint cars to forklifts and antique tractors. Since most backhoes are mounted on tractors with front loaders, it is important to have a strong 4-post ROPS with at minimum a heavy expanded steel mesh 'roof', or much better a solid steel roof. This will prevent a load from falling out of the front bucket onto the operator. The ROPS should be built and installed to exceed minimum safety standards. Some cabs that offer weather protection are not designed as a ROPS frame. This is not the place for light-gage materials or amateur welding. It is absolutely critical to have both a working seat belt and seat combination to prevent ejection. Chewed up/greasy/dirty belt webbing and rusted/dirty belt buckles and retractors are all big trouble. Lap belts must be snug. Avoid slack belts, they will allow greatly increased head and torso excursion in a rollover. If the tractor has a vertically-articulating seat, make sure the tether belts are tight when the seat is in its upper range of travel. Very few seats are strong enough to withstand belt loads, so make sure belts are properly anchored with strong hardware. Lap belts in cars must withstand 5000 pound minimum static load. Seats unfortunately only have to withstand less than 300 pounds static load. Contaminated, cut/abraded belts can be dangerously weak. Same goes for webbing and plastic hardware exposed to excessive sunlight. NAPA sells a lap belt with an Automatic Locking Retractor and all hardware for less than $50. Many salvage-yard automotive belts can also be adapted for very little money. Just make sure they were not worn in a significant crash. The seat belt is no better than the seat it is matched with. Never use a backhoe without using stabilizers first, plus downforce on front bucket. Some older backhoes will allow seated operator feet to get pinched, and they are all great for trapping hands and other body parts. Never operate the hoe or front loader while standing beside the tractor, and never try to operate the hoe while facing forward, or the loader while facing rearward. Never allow anyone to stand within the operating range of the hoe. They can slap sideways faster than a person can move out of the way. For the same reason, never let anyone stand under or ride in the loader. Some ROPS do not account for the operator in a separate or rearward-positioned backhoe seat. Take the time to watch an experienced operator that actually follows safety rules, working in the field. Unfortunately, such folks are hard to find because most act like safety equipment is for sissies. The seat belt actually helps one to be more efficient and to incur less fatigue because it keeps the operator securely in the seat instead of bouncing around. It takes extra muscle action to resist that bouncing and to try to keep oneself in the seat otherwise. Fact is, most tractor rollovers and other injury-producing incidents occur in 3/4 second or less, which is faster than human perception/reaction time. Just about the time you realize you have a serious problem, you get slammed into the ground, etc. There is almost never time to jump clear. In automobile crashes, one is vastly more likely to get killed or seriously injured if ejected from the vehicle, and the same principle applies to tractor rollovers. The ROPS can only do its job if the operator is restrained within that controlled environment which supplies adequate "survival space." The seat belt and seat and ROPS must work together as a system, and if any one of those fail, all bets are off. Older non-ROPS tractors may have ROPS available as kits from manufacturers. They are supposed to sell them at cost but good luck finding one. I have seen decent shop-built ROPS made with minimum 2- 3/8" or 2-7/8" OD heavy wall (3/16" or heavier) steel drill pipe, using lots of gussets and heavy mounting plates and multiple 3/4" dia. or bigger bolts with heavy washers. 3/16" is the minimum tubing wall thickness for these applications. The 2-3/8 drill pipe fits neatly inside the 2-7/8 pipe, by the way. Makes for great joints. Similar efforts can be made with heavy square tubing. Bolts should be minimum SAE Grade 5. Large U-Bolts that encircle the rear axle, and/or multiple pass-thru bolt plates above and below to clamp the axle are best. 1/2" or heavier plates are needed. Again, this is absolutely not a place for an amateur welder. This heavy stuff requires high amperage and someone who understands proper weld penetration of thick materials. Check out a 4-post ROPS on a modern construction-grade backhoe, take measurements and photos, including head clearance above seat. Do not rely on tapped blind holes in the axle housing normally used to secure fender mounts. The bolt sizes used are normally inadequate for anything more than fenders. Take a look at how a competent race car builder installs a full roll cage in a race car. They bolt it to the frame using large U bolts and backing plates. Such a roll cage builder may be willing to build a ROPS using the heavier gage materials. Why the need for such heavy ROPS materials? Typical passenger cars weigh well under 5000 pounds, while even a relatively small tractor with loader and backhoe can weigh in at triple that much. Decide if you would like a cage that will absolutely keep all that weight off of you in a dynamic rollover event. Make sure there is at least 42" of minimum head clearance between the ROPS and the seat when it is in its highest position. That is the only way to insure adequate headroom. Colorado State University Ag department website has videos of ROPS in action in rollover tests. ALso lots of info at Marshfield Clinic in Wisconsin. Sorry for the long response, but you have lots of safety issues to consider. Hope this helps.
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