Car stability paper

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aopagary
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Re: Car stability paper

Post by aopagary » Tue Jan 02, 2018 1:38 pm

tornitore45 wrote:I do not know if these cars have springs, if they do is also a factor. Center of Gravity is a static thing but in a moving car the springs define the natural oscillation response and that can amplify the swing up to the static tipping point.
if you notice, in every mention of using a prototype freight car for passenger service, i always included words to the effect of "well built". i'll also add to that, "well maintained" which does not preclude replacing worn-out springs or making sure the springs and the trucks in general are a good match for the load. i often witness freight cars which may ultimately track well, but exhibit far too much sway to hopefully never be considered for passenger service.

not sure if trucks are the biggest problem here, however. i don't mean to shed any negative light on those who maintain club tracks, but if blown up to 8x scale, i doubt if many would pass as Class 1 mainline tracks.

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cbrew
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Re: Car stability paper

Post by cbrew » Tue Jan 02, 2018 2:56 pm

NP317 wrote:CG stability is a reason for the increasing adoption of straddle cars for passenger hauling, especially on a public railroads.
Not having feet trapped inside car walls contributes to safe riding.
~RN
i used to agree with this mindset until i have watched a few derailments where the feet had slid off the deck and hit ground object. if that rider would have been wearing open toe shoes, they likely would have had a very bad day. so imho, the best solution is a hybrid of the two. still have a drop center car with straddle style seating but also have a 2 to 3 inch side that will keep the feed inside the car. the car will still benefit of having the low CG and the lower platform will still come to rest on the rail head providing the stability in the event of a derailment. and also taking steps to prevent a loose foot from losing a toe.
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NP317
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Re: Car stability paper

Post by NP317 » Tue Jan 02, 2018 7:43 pm

cbrew has an excellent suggestion about added low car sides to keep feet safe.
Club tracks I have steamed at don't allow people to ride unless they are wearing "closed" shoes.
Simple decision there.
~RN

Oilcan
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Re: Car stability paper

Post by Oilcan » Thu Jan 04, 2018 8:23 am

Bill Donovan (Real Trains) wrote a nice article on the stability of 7-1/2" riding cars that was published in the Nov-Dec 2012 issue of Live Steam & Outdoor Railroading. If you have the issue, check it out. Otherwise, it's still available as a back issue.
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Kimball McGinley
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Re: Car stability paper

Post by Kimball McGinley » Thu Jan 04, 2018 3:23 pm

At the OCME, our conductors sit back to back with the engineer. That way they can make eye contact with the riders and watch for straying feet, but sides are a great idea. I also learned the phrase "Levante los pios!" for our Spanish-speaking riders.

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Re: Car stability paper

Post by Glenn Brooks » Thu Jan 04, 2018 6:58 pm

Oilcan wrote:Bill Donovan (Real Trains) wrote a nice article on the stability of 7-1/2" riding cars that was published in the Nov-Dec 2012 issue of Live Steam & Outdoor Railroading. If you have the issue, check it out. Otherwise, it's still available as a back issue.

Oilcan,

This might be the article I am looking for. Do you know if it is available on line?

Thanks
Glenn
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BigDumbDinosaur
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Re: Car stability paper

Post by BigDumbDinosaur » Thu Jan 04, 2018 8:21 pm

Kimball McGinley wrote:At the OCME, our conductors sit back to back with the engineer. That way they can make eye contact with the riders and watch for straying feet, but sides are a great idea. I also learned the phrase "Levante los pios!" for our Spanish-speaking riders.
I believe you meant to say Levanta tus pies, por favor! The phrase ¡Levante los pios! would be nonsensical in Spanish.

"Píos" is the plural of "pío," the latter which has several meanings that are determined by context. As an adjective, "pío" could mean "devout," "pious," or "sanctimonious," e.g., "Diego es tipo muy pío." Translated, that could be "Jim is a very devout guy." How "pío" would translate would be determined to some extent by inflection and context.

When used as a noun, "pío" usually refers to the sound made by a bird (tweeting). For example, "Un pájaro pequeño aterrizó en el comedero y dejó escapar pío fuerte." "A small bird landed on the feeder and made a loud tweet."

So I'm pretty sure you don't want your passengers "lifting" any loud tweets or hurting their backs trying to elevate the pious ones among them. :D
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STRR
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Re: Car stability paper

Post by STRR » Thu Jan 04, 2018 9:00 pm

Glenn,

If you can't find it on line, let me know, I have that Live Steam issue. I just have to dig it out and find the article.

Terry

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makinsmoke
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Re: Car stability paper

Post by makinsmoke » Sat Jan 06, 2018 9:49 am

Maybe I'm missing something.

Comparing a "rider gon" to a T or I beam rider
or the steel engineer cars with seats..

My first take is most of the time center of gravity is not all that different. Think about where and how high the rear end is on a seated passenger. The height of all three cars is not that different.

Where you get some help in stability is the feet are lower, where the gain there is only where gravity and centrifugal force push your body in different directions. Starting and stopping the body would tend to rotate downwards at a sharper radius versus with the feet higher.

To me, that is the only gain with the T or I beam car as far as feet placement.

The real gain in stability from the flat plate engineer car with seats is the massive weight gain very close to the axle centerline due to the design and covstruction using steel tubing and plate. Those cars are pushing 250-300 pounds empty, and most of that weight is within inches of the axle centerlines.

Again, having folks riding around on boxes or seats all pretty much at the same height is a common factor that can't be overlooked.

Most important with all of these cars is proper function of the suspension. Correct spring loading as well as truck and car body bolster pads with the proper clearance. If the gap is too great and/or springs are too light excessive car body sway is unavoidable, no matter what design you utilize.

Just my two or maybe three cents.

Brian

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Re: Car stability paper

Post by Cary Stewart » Sat Jan 06, 2018 7:17 pm

Another aspect of this problem is the size of the adults (and maybe some older children) that can add to car instability. In California after a tragic loss of life at Disney Land when a very obese lady who had the safety bar in place was thrown from the ride car in a very severe move of the roller coaster. The result was that the state ruled that a ride operator has the right to refuse any very obese person a ride. The exception to this is that if the lady is pregnant and not extremely obese you must let her decide to ride or not. It is the operators choice in the case of extreme obesity, even for pregnant women whither to allow her to ride. At LALS the straddle car seat height is less than the height of those tracker seats that many use on cons and flats. The worst case is if you have a Pullman coach with built in seats the passenger must have a slim enough bum to fit in the car. They may not ride on top of the seat back. We have the experience to know these things. A safety engineer consulted with us and said we had to add 180 pounds of weight under the straddle cars and other safety measures. You can imagine the weight of the enhanced cars. We did some testing and found that a lessor weight was acceptable. We also limit the number of people we allow on each car based on the size of them. Best not to have your truck springs fully compressed.
Cary

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Atkinson_Railroad
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Re: Car stability paper

Post by Atkinson_Railroad » Sat Jan 06, 2018 7:38 pm

Decisions made by those shaping this hobby before us have dictated what we have today.
Historically, car stability in building miniature railroad equipment was an afterthought.

As Bill Donavan writes in his IBLS article mentioned earlier by pat1027 and oilcan,
park trains designed with the goal of giving a person a “ride’ were built to accommodate that objective.

Reference again here: http://ibls.org/mediawiki/index.php?tit ... -On_Trains

When it comes to the efforts of the industrious hobbyist building within their own means,
working in narrower than park gauge sizes, the story winds a little different.

Tracing far enough back into the past related to miniature railroading, the idea of actually getting aboard
a small moving train was one of personal challenge or novelty and not necessarily about a stable functioning ride.

Early emphasis was focused on building the locomotive and getting it to “move” on its own while rolling stock to ride on, was a lesser.

Today, the straddle type car design could be labeled a “safest” car for adults as mentioned in the topic but not so much for little people.
The straddle type car safety factor or effectiveness of actually being a SAFE riding car ranks quite poorly for small children.

Proof of this statement is pointedly illustrated in one of the earlier photos posted in this thread.
Scroll back to the picture and note how there's an older person holding on snugly to each small child riding the straddle type cars.

It reads like there are some good ideas here to further improve its design though in combating the top heaviness factor.

Interestingly, a tank car (those built with a center sill and modeled walking platforms for placing one’s feet) could be viewed as a first generation straddle type car. I fondly remember from childhood (1960’s) how there could be a fight over who got to ride on the tank car if someone didn’t get to it first.

Noting to Glenn who started this conversation, you have a [luxury] because you’re working in a larger gauge.
You have more freedom to push the teetering limits and do not have to consider the stability issue the way those
working in the popular ‘7’ and smaller gauges have to manage.

John
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Glenn Brooks
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Re: Car stability paper

Post by Glenn Brooks » Sat Jan 06, 2018 9:08 pm

John,

Thanks! This is the very article I was trying to locate. For me, Bill Donovan’s four case examples are perfect descriptions why we have derailments and rollovers, and more Importantly, how to mitigate them.

Iam particularly interested in how Donovan describes how a rider’s center of gravity rotates about a car’s pivot point - usually the contact point between wheel and railhead - throughout the full arc of motion, from sitting upright, to leaning over to the point where the turning moment of the passengers CG overcomes the weight of the car CG - and the wheels lift up and it rolls over.

What I observed over and over again in the amusement industry, is that passenger safety depends how well we anticipate and mitigate all the UNUSUAL behaviors of people rising in cars, not just the safe and usual ones.

Thanks for pointing out where this write up can be found.

Glenn
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