Design of occupant arm protection cage 9

[ExtraSalty]

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,

 

[handleman]

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)

 

[drawoh]

ExtraSalty

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

--
JHG

 

[drawoh]

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

 

[IRstuff]

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/..._Regulations_for_Competitors_(Safety)_(K).pdf

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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[MintJulep]

I'd start by talking to these guys and their competitors if there are any.

http://www.energyabsorption.com/products_workzone.asp

No sense reinventing the wheel - with the attending liability.

Alternately, drop your cones from one of these

 

[ornerynorsk]

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.

 

[chicopee]

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.

 

[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.

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.

 

[chicopee]

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

 

[MikeHalloran]

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

 

[drawoh]

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

 

[IRstuff]

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-page_summaries/ahmct_cone_machine_070522_B.pdf

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.cfm?modelID=57

http://ahmct.ucdavis.edu/?projects=test-deployment

TTFN
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[ExtraSalty]

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,

 

[KENAT]

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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[IRstuff]

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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[handleman]

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)

 

[IRstuff]

Yeah, I see that now. Should have gone to bed...

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[IRstuff]

One thing that hasn't been mentioned is how the reflectors get attached to the road, as that might make some difference in what solutions are possible. Are these the ones that require a blowtorch?

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[KENAT]

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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