roll bar question

[SPYDERLK]

pins, bolts makes absolutely no difference if the "shear strength" of the pin meets or exceed that of bolt in question. Why is it that many new folding ROPS rely on hitch pins?

JC,

If it's designed for pins, fine. If it's designed to be clamped with bolts, that's different. To meet certification, the ROPS needs to be maintained as originally designed.

I only throw this out there because in the event of a failure, liability falls upon the individual who made the modifications.

That is true enough. Let's just say the bolt is class 2 and one replaces with class 5 equivalent pin. In the case of law suit obviously manufacture blames owner modification, case closed even if the replacement exceed original specs. We're simply giving opinion to the OP based our personal experience or knowledge. Op is the one that will sort it out and would make his decision as an adult.

JC,

Well, heres some fact. As was intimated back in Post#20 ... Shear relies on joint surfaces restrained to position very close to each other. If it spreads under force the shear is greatly affected because the pins/bolts are bent instead or additional to shear. A bolt clamped joint will not spread. The safe side is to use Gr5 bolts with shank crossing the full shear zone. Tighten them to a few foot lbs - not a hundred - to clamp while not crushing the uprights.
larry

 

[JC-jetro]

Well, heres some fact. As was intimated back in Post#20 ... Shear relies on joint surfaces restrained to position very close to each other. If it spreads under force the shear is greatly affected because the pins/bolts are bent instead or additional to shear. A bolt clamped joint will not spread. The safe side is to use Gr5 bolts with shank crossing the full shear zone. Tighten them to a few foot lbs - not a hundred - to clamp while not crushing the uprights.
larry

Larry,

I don't have any issue about clamping the assembly together, properly torqued is a better and efficient set up to benefit the max shear available from the bolt. What I'm saying is in the case of folding ROPS the hitch pin has enough safety it might bend some (due to not being tight) but will not fail or shear off. The manufacturer will have huge liability if one of these ROPS fails and I'm sure they have done controlled rollover of their rigs to evaluate their ROPS design.

JC,

JC,

 

[barbqranch]

I expect a hitch pin is a lot stronger in shear than is the threaded portion of a bolt.

 

[JC-jetro]

I expect a hitch pin is a lot stronger in shear than is the threaded portion of a bolt.

That is so true and a good point. Threaded part of the bolt with smaller dia and a lot more chances of surface or deeper rust accumulation. We have Sch 40 and 80 steel pipe for our chilled/hot water and steam systems. Pipe failure at threaded parts are a lot more prevalent.

JC,

 

[barbqranch]

That is so true and a good point. Threaded part of the bolt with smaller dia and a lot more chances of surface or deeper rust accumulation.
JC,

Not only that, but most any machinist will tell you that a sharp change in diameter is asking for trouble, as the bending forces are concentrated there. When turning down a shaft to a smaller diameter in one section (say for a bearing on a conveyor shaft) they will ease it over an 1/8 inch or so if the design permits. Makes it much stronger.

 

[Grayson Klassen]

Agree that machining a step change in a shaft abruptly leads to significant weakening of the structure, however I am pretty sure a new shop would solve all the woes.

 

[SPYDERLK]

Larry,

I don't have any issue about clamping the assembly together, properly torqued is a better and efficient set up to benefit the max shear available from the bolt. What I'm saying is in the case of folding ROPS the hitch pin has enough safety it might bend some (due to not being tight) but will not fail or shear off. The manufacturer will have huge liability if one of these ROPS fails and I'm sure they have done controlled rollover of their rigs to evaluate their ROPS design.

JC,

What Im saying is if the outer part of the joint can spread, and does under the applied load, then the situation becomes quickly critical ... sorta like a chain reaction. A joint cannot spread with a snugged bolt. --- Also this is not a folding rops and the fine points of its design are not evident from the photos.
larry

 

[SPYDERLK]

I expect a hitch pin is a lot stronger in shear than is the threaded portion of a bolt.

That is so true and a good point. Threaded part of the bolt with smaller dia and a lot more chances of surface or deeper rust accumulation. We have Sch 40 and 80 steel pipe for our chilled/hot water and steam systems. Pipe failure at threaded parts are a lot more prevalent.

JC,

Well, heres some fact. As was intimated back in Post#20 ... Shear relies on joint surfaces restrained to position very close to each other. If it spreads under force the shear is greatly affected because the pins/bolts are bent instead or additional to shear. A bolt clamped joint will not spread. The safe side is to use Gr5 bolts with shank crossing the full shear zone. Tighten them to a few foot lbs - not a hundred - to clamp while not crushing the uprights.
larry

Im glad yous see that point, intimated prior, and find it odd that there is disagreement in consensus.
larry

 

[sweep]

My local dealer has a bunch of parts tractors on the back lot with folding rops on them. I would bet if you hit your local tractor salvage yards you can find something that would work on your tractor-maybe with some slight modification.

In terms of welding/modifying a bar I would have no problem with that. NH say's not to weld on the rops for legal reasons because they don't want amateur welders with their Home Depot $100 welder mucking up the bar with some weak welds.

A certified proffesional welder would make sure the roll bar is stronger than stock to protect himself -probably with extra gussets/traingulation points etc.

A local guy restored a MF 135 tractor and the local fab shop built him a roll bar ( I live in appalacian hill country). They apparantly had enough confidence in their work to send it out the door.

 

[wood butcher]

It will take some fab work, but I would strongly recommend a hinge set up so you can leave it on then just pull 2 pins an go with it. remember when you need it it will be to late to put on, there are a lot of dead an phucked up men from not having them or a case here in ga a fellow just didn't fold it up. an tr. rolled he expired. that was only a few years back.
Army Grunt

There was a guy who was killed around here who didnt have a ROPS. Tractor rolled right over on him. I didnt get one with my 1920 but I am looking for one.