ROPS regulation

[SethO]

I started a thread about a cheap work light that I installed, but most of the discussion appeared to focus on the issue of how one should mount attachments to the ROPS.

I believe that this issue merits its own thread, while it relates to safety, I feel that since it involves possible modifications it can be posted under the Build-It-Yourself forum

Is there any regulation requirement for these ROPS in terms of what the distribution of forces should be, the tolerances of the frame and what impact they are designed to withstand?

 

[RobS]

There are SAE standard for both ROPS and FOPS. SAE.org sells copies but does not have free services. My very outdated set of SAE handbooks is at home but I can check tonight if you'd like. Perhaps someone else has something handier /forums/images/graemlins/smile.gif

 

[RonR]

Were it not fear of a lawsuit........

I'd cut the ROPS on my BX2200 and make it fold like a BX22, so I could get it in a shed for winter storage.
I don't think they are interchangeable, or I would buy one.

I work on flat land, but just in my yard, I've had one rear wheel come of the ground MORE THAN ONCE! So, I'm
less willing to cut it now. And if I were the sole operator forever, I'd likely do it. But I can't guarantee that.

And even though I could make it as strong as a BX22 and (Probably) as strong as original by getting an informal
Engineering opinion on it (No sane Engineer would document it as OK, for fear of lawsuit), I don't think the risk is worth it.

I might end up drilling some small holes to mount lights--I can take that risk--but doubt that I do my structural mod.

Ron

 

[enbloc]

Re: Were it not fear of a lawsuit........

I think you're right in the conclusion that it's not practical to get an engineer to ok your modifications, because it would be very expensive. But this is what engineers do. That's why they're licensed, and not just called "engineer" because they graduated from an engineering school and are gainfully employed. But an engineer would almost certainly want to be involved before you did anything, and not just check your design modifications after the fact.

Even if your son is engineer who will give you free advice, and a couple weeks of design time, he'd probably not be willing to sign his name on anything that he's not getting paid for. He might personally assure you you could set off bombs on it, but the only point of signing off is to assume liability if the design proves faulty.

 

[RobS]

I dug up my SAE handbooks, 1982 edition. The standard is SAE J1194 - Roll-over protective structures (ROPS) for wheeled agricultural tractors . There are seperate standards for industrial, construction and mining equipment. It is quite likely that changes to the standard have been implemented since my book was published.

I cannot scan and post the standard due to copyright laws. It is seven pages and covers static loading, crush, impact and field upset. All of the requirements are calculated based on tractor mass making it difficult to provide any easy answers here. I'll quote the first paragraph in the static test procedure to give you an idea.

"Apply the rear load per Fig. 4 or 5 and record F and D simultaneously. Rear load application shall be uniformly distributed along a projected dimension no greater than 686 mm (27 in) and an area no greater than 0.1032 m^2 (160 in^2) normal to the direction of load application. The load shall be applied to the upper extremity of the ROPS at the point which is midway between the center of the ROPS and the inside of the ROPS upright. If no structural cross member exists at the rear of the ROPS, a substitute test beam which does not add strength to the ROPS may be utilized to complete this test procedure. (see paragraph 6.4.1.1) if field upset is to be omitted. Stop this test when: (a) The strain energy absorbed by the structure is equal to or greater than the required input energy Eir (paragraph 6.1.2) or (b) deflection of the structure exceeds the allowable deflection (paragraph 7.1.1). "

Clear as mud now, right???

Practically speaking, there are probably a lot of modifications you could do to your ROPS that would not affect it's performance. From a liability and certification perspective though, you would have to rerun the entire test sequence on your proposed modification and demonstrate that it meets the requirements. Many of the tests are destructive tests so you would have to make several sets of your proposed hardware to get through the standard. Once you did all that, document it all in an engineering report and archive all documentation and test hardware for future reference.

This is a very abbreviated explaination of why cars, trucks and tractors cost as much as they do /forums/images/graemlins/smile.gif

 

[RonR]

Yep, RobS, that clarified it!

If I decide to mod my Rops, I'll go buy 10 extra ROPS and do the mod and test it--likely would have the cost of several new CUTs by the time that was done.

The only reason to go through that hassle was if you were going to SELL your mod.

If you did mod your own and the unthinkable happened (Injuring someone else, maybe even subsequent owners of the hardware), then all the testing and analysis would be done as part of the lawsuit to assess who was liable.

I've worked around equipment for 30+ years and have developed an eye for seeing where the weak points are in equipment. Would I risk my life by drillng two 3/8" holes in my ROPS? Probably. To me that would be very low risk. Would I risk the hassle of lawsuits if someone else got hurt and I had to defend two 3/8" holes in my ROPS? Probably not. Especially with all the warning labels and decals about not doing anything to the ROPS.

I'm not an engineer and I've not studied the specs on a CUT and ROPS, but common sense tells me the strength of the ROPS in relation to the weight of the tractor there is a LOT of excess strength in the rops.

Anyone got any photos of a CUT that's rolled that shows damage to the ROPS?

Thanks for posting the requirements.
Ron

 

[SethO]

RobS,

Thanks for the information.

I think what manufacturers should do is provide anchor points on the structure for attachments. The maximum weight or size that can be attched can then be specified as they do with implements.

SethO

 

[Mrwurm]

Re: Yep, RobS, that clarified it!

</font><font color="blue" class="small">( Especially with all the warning labels and decals about not doing anything to the ROPS. )</font>

Interesting. My TC30 has no warnings about ROPS modifications. Can't say I ever noticed any stickers on any other brand I compared while shopping. Did I overlook this ?

 

[Mrwurm]

Re: Yep, RobS, that clarified it!

Ok, heres some additional thoughts:

When a tractor rolls, it rolls onto the ROPS and the hood. Are there saftey specs for hood strength? Should we be cautioned against drilling holes in the hood? Most CUTs now have a plastic hood. Does this meet the safety requirements?

 

[Mrwurm]

Re: Yep, RobS, that clarified it!

Many of know that I have no reservations about modifying a ROPS. Here's part of the reason why.
The ROPS on my TC30 is split into two indentical halves. The split being at the top in the center. There is a small strip of metal (about 3/4 wide by 2 in long by 1/8 thick) that joins the two sides. There is one small bolt on each side that joins the whole thing together. This is so light duty it is unbelievable to me. I can't imagine that drilling a few small holes (1/4 in) in the upright solid area of the ROPS can endanger me anymore than this light-duty NewHolland engineering.