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Design of occupant arm protection cage
9

Design of occupant arm protection cage

Design of occupant arm protection cage

(OP)
Hi all,

I am working on a job where the client has asked for a protection cage against on-coming traffic. More specifically, the cage is to be mounted to a line marking truck whereby the occupant reaches out from the side of the truck in order to place road markers. The client wants a cage to protect the arm of the occupant in the event of on-coming vehicles passing too close. The maximum speed of all on-coming traffic will be limited to 40 km/hr (25 mph) while the truck will be moving at walking speed.

I was wondering if there are any available standards/guides to design the cage to. I am aware that there are multiple standards for direct impact protection, however, they do not give anything relating to side swipe actions.

Cheers,

RE: Design of occupant arm protection cage

Welded, gusseted 1" thick steel plate in a wedge shape MIGHT be enough to push your truck out of the way of an oncoming 40MPH semi. Otherwise, I don't see how you can build a cage to protect the person's arm. Unless your spec is only to protect against side mirrors or other relatively weak protrusions, I would think that a high-visibility large structure to deter drivers from getting too close would be about all you can do.

-handleman, CSWP (The new, easy test)

RE: Design of occupant arm protection cage

ExtraSalty

Is that mechanically/electronically limited to 40kph, or politely asked to not exceed 40kph?

--
JHG

RE: Design of occupant arm protection cage

ExtraSalty,

Can you prominently place a couple of day-glo orange steel spikes on handleman's 1" thick gusseted plate? Your worker may be expendable, but there will be concern for the oncoming car's grille and headlights.

--
JHG

RE: Design of occupant arm protection cage

I would look to something that might deflect the other vehicle, rather than an outright barrier, i.e., have a slope. The structure may need to be built like a roll cage, and may need to have safety colorization. Blinking lights probably couldn't hurt.

Some possibly useful information on roll cages:
http://www.msauk.org/uploadedfiles/msa_forms/blueb...

Nonetheless, any sort of absolute protection would be essentially impossible. Moreover, building the structure to withstand requirements that exceed crash safety requirements would be difficult to justify.

TTFN
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Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers

RE: Design of occupant arm protection cage

I'd start by talking to these guys and their competitors if there are any. http://www.energyabsorption.com/products_workzone....

No sense reinventing the wheel - with the attending liability.

Alternately, drop your cones from one of these



RE: Design of occupant arm protection cage

As IRStuff said, absolute protection is a near impossibility. One could engineer this solution to a nonsensical death, and drive the project cost through the roof. Very common in the realm of road construction safety management are simple warning markers. When is the last time you've seen a flagman at the side of the road protected inside of a crash cage? They are far more exposed than a worker on a vehicle.

Is a lightweight horizontal pole (or poles) with breakaway hinge protruding from the side of the vehicle with appropriate flags or banners, far enough out to encourage oncoming traffic to slow and keep their distance, together with some ordinary, common sense vigilance on the part of the person dropping the cones, not adequate somehow?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Design of occupant arm protection cage

I had in mind a snow plow when I read IRstuff than I saw MintJulep' picture. Also perhaps a similar design to crash protection trucks but with the energy absorbing system upfront and extended side ways.

RE: Design of occupant arm protection cage

(OP)
Thanks for all the replies! With regards to handleman, drawoh and MintJulep's snowplow with steel spike ideas, I'll definitely keep them in the back of my mind just in case of a zombie apocalypse.

But in all seriousness, my initial thoughts were also more on deterrence than absolute protection. The cage itself has to be able to fold out from the truck so that it doesn't obstruct traffic when the truck is moving to/fro the stretch of road it needs to mark. This means the actual cage can't be solid and energy absorption systems are not economically/practically feasible.

The cage will most likely be there to just appease the client/occupant. I guess the main factor will be painting the cage with warning colours and hope all oncoming traffic is smart enough to steer clear.

Cheers all and thanks again for the the ideas.

RE: Design of occupant arm protection cage

A cage will do "zilch" and could even aggravate the injury to the worker in the event of an impact.

RE: Design of occupant arm protection cage

You want the cage to be highly visible to oncoming traffic. Bright paint on slender tubes won't make them stand out from the usual visual clutter near the road surface. Think big tubes, like a set of 'roo bars', hinged at the lower corner so they can be swung up. If they don't extend too far up in deployed position, they might fold over out of the driver's sight line in stowed position.

Or just use an actual wing plow with big diagonal stripes.


Mike Halloran
Pembroke Pines, FL, USA

RE: Design of occupant arm protection cage

Quote (ExtraSalty)


Thanks for all the replies! With regards to handleman, drawoh and MintJulep's snowplow with steel spike ideas, I'll definitely keep them in the back of my mind just in case of a zombie apocalypse.

...

Are zombies bad drivers?

Can you place the worker so that they are facing traffic, and can always see what is coming at them? They should be facing forward, and sitting low so that their heads are not down when they are working. Obviously, they need somewhere to dive to when they see something coming at them.

--
JHG

RE: Design of occupant arm protection cage

The purpose-designed vehicles I've seen are precisely that way; there's a platform with a seat that's about 1 ft off the ground with the rider facing traffic. Their bodies are mostly overlapped by the body of the truck, but their arms are exposed when they're actually placing the traffic cones on the ground.

Caltrans, on the other hand, has at least a few traffic cone placement trucks that use a mechanical placer, so no body parts are at risk:
http://www.dot.ca.gov/research/researchreports/two... which is an option if the cost of infrastructure to protect the worker is too high. I could see possibly only implementing the placement equipment and manually feeding it cones to cut down the cost.

Other:
http://www.centrevilletrailer.com/trailerDetails.c...
http://ahmct.ucdavis.edu/?projects=test-deployment

TTFN
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RE: Design of occupant arm protection cage

(OP)

It is as drawoh says. The occupant placing the reflector markers are facing the oncoming vehicles. Problem is that they need to look down at where they want to place the reflector marker, eject a glob of glue onto that spot, then place the marker over the glue. This needs to be repeated every few metres over a good 50 km stretch of road.

The truck set up is basically identical to what IRstuff has seen. I'm in Australia and the idea of automating the process is too costly for the state road authority here. As far as I know, the thing with the occupant arm protection cage to be fitted to the side of trucks has never been done before. This is why the client wants to know if the cage can be designed to any relevant standards/codes (regardless of local or international). Does anyone know of any standards to this effect (other than the generic steel design standards - e.g. LRFD, AS4100, AS3990).

Cheers,

RE: Design of occupant arm protection cage

OK, how about doing this another way.

Can the need for the operator to put his arm into traffic be eliminated without automation.

Can some kind of chute or similar be developed that allows the operator to stay within the footprint of the vehicle while allowing the glue and reflector to be deposited?

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RE: Design of occupant arm protection cage

I don't see that as a possibility, since that would mean that truck has to be rolling over the reflectors.

One possible approach is to get either a sonar or radar so that the operator can be warned about oncoming traffic. Something with about 50 ft range would give you at least a half-second of warning.

Another option is to put the operator seat and roll cage deflector on a pivot with a breakaway, so that if the roll cage is hit, the breakaway would cause the seat and roll cage to pivot toward the centerline of the truck. The breakaway would also be used to stow the seat closer to the truck centerline for transport.

TTFN
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RE: Design of occupant arm protection cage

I believe Kenat was referring to some sort of articulated mechanical linkage that could be manually operated from a safe location inside the vehicle.

-handleman, CSWP (The new, easy test)

RE: Design of occupant arm protection cage

Thanks handleman, that is indeed what was meant to be implied by "or similar".

I can imagine getting accurate positioning could be a bit trickier but I'm sure someone brighter than me could address that issue.

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RE: Design of occupant arm protection cage

ExtraSalty,

How about applying something like Scotch VHB structural tapes to the bottoms of the cones? The worker peels away the backing while looking forwards for oncoming vehicles, and places the cone.

--
JHG

RE: Design of occupant arm protection cage

I would think the ergonomics of reaching out and down all the way to the road would be terrible... RSI waiting to happen.

If the glue could be applied to the bottom of the reflector, the operator could put the reflector onto some sort of gripper or vacuum pad at a comfortable work height, then push the arm out and down to position the reflector on the road.

-handleman, CSWP (The new, easy test)

RE: Design of occupant arm protection cage

Has anyone talked to the people who actually place the cones, dots, etc.?

Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

RE: Design of occupant arm protection cage

I don't think cones are glued or otherwise attached to the road surface. A lot of reading between the lines is being done here. Anyone who has ever handled traffic cones can tell you that they have sufficient weight and proper weight distribution to stand on their own without worry of draft from passing vehicles displacing them.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Design of occupant arm protection cage

2
Actually, a lot of not reading the actual lines is being done.

The OP actually outlined the process in question pretty clearly. This is not cones. It's reflectors glued to the road.

Quote (ExtraSalty )

The occupant placing the reflector markers are facing the oncoming vehicles. Problem is that they need to look down at where they want to place the reflector marker, eject a glob of glue onto that spot, then place the marker over the glue. This needs to be repeated every few metres over a good 50 km stretch of road.

-handleman, CSWP (The new, easy test)

RE: Design of occupant arm protection cage

Quote (MintJulep)

There's already at least some development on an automated system for this.

http://www.youtube.com/watch?v=_635Xt3We4E

Can't see why anyone would attempt to do build a cage when a solution like that is so simple (and safe). Of course now you've just put another person out of a job (but a dangerous job obviously).
One could easily build a system like that for a few thousand dollars.

RE: Design of occupant arm protection cage

Heck.. keep the person employed but just sitting in the back of a truck watching a camera, loading more reflectors into a tray and pressing the green button. No need to distract the driver which poses more of a danger than anything in my opinion..

RE: Design of occupant arm protection cage

MintJulep:
RE: your 4SEP13, 10:52 post.... I like the plows and the big truck. But, there seems to be a bit of a scale problem with the picture. Notice that the circle sawn pine board fence behind the truck must have about 4' +/- wide boards, 20' + high, or there is something fishy about that truck. That’s one hell of a snow fence.

RE: Design of occupant arm protection cage

Obviously it snows a lot there

RE: Design of occupant arm protection cage

Good on ya, Handleman! Thanks for pointing that out. My bad.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

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