oltmannd They were using cylindrical? What the heck for? Amtrak uses 1:40 and it's 85' cars are stable at 125 mph. You usually only need cylindrical for hunting stability at really high speeds - (or short equipment)
They were using cylindrical? What the heck for? Amtrak uses 1:40 and it's 85' cars are stable at 125 mph. You usually only need cylindrical for hunting stability at really high speeds - (or short equipment)
oltmannd rcdrye Milwaukee Road's Karl Nystrom did some extensive studies on wheel tread along with his work on high-speed truck design. His wheel tread results can be summarized in a few paraphrased statements: 1. Ground wheels and good track maintenance will give reasonable results. 2. Wheels that are out-of round are impossible to correct for. 3. Good riding is not necessarily a function of wheel base; and 4. Wheel shimmy is caused by the shape of a worn wheel and does not depend on the shape of the tread when new. Nystrom was not able to predict wheel wear on the basis of truck design. Nystrom tried both cylindrical and conical treads and ended up recommending a shallower-than-normal conical tread. He also pointed out that trucks for low-speed suburban operations require stiffer damping than trucks for high-speed operation. Interesting. Milwaukee Road certainly was a pioneer... What's changed in the last 30-40 years since is welded rail. Jointed rail had just enough irregularity to damp out incipient truck hunting. Things that lower the hunting threshold speed are: - shorter distance between bolster centers - higher polar moment of inertia (e.g. bulk head flats) - greater tread conicity As wheels wear, the effective conicty increases which is why high speed train set are constantly getting their wheels trued as part of regular maintenance. In freight world, all sorts of games are played to stop hunting. The most common is the constant contact side bearing. The downside of this device it always keep the truck a bit off running "true".
rcdrye Milwaukee Road's Karl Nystrom did some extensive studies on wheel tread along with his work on high-speed truck design. His wheel tread results can be summarized in a few paraphrased statements: 1. Ground wheels and good track maintenance will give reasonable results. 2. Wheels that are out-of round are impossible to correct for. 3. Good riding is not necessarily a function of wheel base; and 4. Wheel shimmy is caused by the shape of a worn wheel and does not depend on the shape of the tread when new. Nystrom was not able to predict wheel wear on the basis of truck design. Nystrom tried both cylindrical and conical treads and ended up recommending a shallower-than-normal conical tread. He also pointed out that trucks for low-speed suburban operations require stiffer damping than trucks for high-speed operation.
Milwaukee Road's Karl Nystrom did some extensive studies on wheel tread along with his work on high-speed truck design. His wheel tread results can be summarized in a few paraphrased statements:
1. Ground wheels and good track maintenance will give reasonable results.
2. Wheels that are out-of round are impossible to correct for.
3. Good riding is not necessarily a function of wheel base; and
4. Wheel shimmy is caused by the shape of a worn wheel and does not depend on the shape of the tread when new. Nystrom was not able to predict wheel wear on the basis of truck design.
Nystrom tried both cylindrical and conical treads and ended up recommending a shallower-than-normal conical tread. He also pointed out that trucks for low-speed suburban operations require stiffer damping than trucks for high-speed operation.
Interesting. Milwaukee Road certainly was a pioneer...
What's changed in the last 30-40 years since is welded rail. Jointed rail had just enough irregularity to damp out incipient truck hunting.
Things that lower the hunting threshold speed are:
- shorter distance between bolster centers
- higher polar moment of inertia (e.g. bulk head flats)
- greater tread conicity
As wheels wear, the effective conicty increases which is why high speed train set are constantly getting their wheels trued as part of regular maintenance.
In freight world, all sorts of games are played to stop hunting. The most common is the constant contact side bearing. The downside of this device it always keep the truck a bit off running "true".
Interesting as the original CNW St. Louis Gallery cars used to go ape shxxt on the jointed rail on the eastbound track between Elmhurst and Mannheim Road, they really settled down when we hit the welded rail east of there.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
The problem that I heard about with the conical profile is that it wears hollow and then you really have problems with "hunting" and the resulting rough ride.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Electroliner 1935 Since this thread is about wheel-rail interaction, I will again ask about what can cause the experience I had back in the early '90's. On one of my trips on an All Aboard America fare, I was going from Chicago to NYP on the Lake Shore Limited. We had changed locomotives at Albany-Renssalaer and with an FL-9 leading us, we accelerated up to 90 mph. On some of the curves, it felt like a sledge hammer hit the side of the truck multiple times. It made me think of a croquet mallet hitting a ball. I had some concern about what could cause such a sensation, (could a wheel be trying to climb the rail?) but have only experienced it one other time and that was when riding in the front of the BC Rail's Cariboo RDC going North to Prince George, BC. The train was running late because North of Lillooet, one of the diesel engines had shut down on the grade and we waited for a Road Forman of Engines who was on a SB freight to arrive and get us help. He got it going and we were running about 45 minutes late. At Williams Lake, the crew changed and a senior Engineer took the controls and he was determined to make up the time. Forget about speed limits, this was his territory and we were exceeding the speed limit. I had an ETT and IIRC the passenger speed limit was 70 and some curves were 50 mph. We entered one 50 mph curve at 70 and about halfway thrugh it we were down to 60, and he opened the throttle. The Budd car felt like it was trying to climb the rail as the feeling was like the wheel was lifting up and dropping down. Not the side bang that I experienced on the above Amtrak trip. The fun thing on the BC rail trip that I would not have seen if I was not riding up front was a black bear that almost got goosed by us. It was loping along the track as we approached and didn't seem to want to get off the ROW. I was thinking this might get messy but when we got to within about ten feet, it went to the side and lived. We arrived in Prince George about ten minutes late. So my question is, what might cause a sharp side impact sensation on a passenger car taking a curve at speed?
Since this thread is about wheel-rail interaction, I will again ask about what can cause the experience I had back in the early '90's. On one of my trips on an All Aboard America fare, I was going from Chicago to NYP on the Lake Shore Limited. We had changed locomotives at Albany-Renssalaer and with an FL-9 leading us, we accelerated up to 90 mph. On some of the curves, it felt like a sledge hammer hit the side of the truck multiple times. It made me think of a croquet mallet hitting a ball. I had some concern about what could cause such a sensation, (could a wheel be trying to climb the rail?) but have only experienced it one other time and that was when riding in the front of the BC Rail's Cariboo RDC going North to Prince George, BC. The train was running late because North of Lillooet, one of the diesel engines had shut down on the grade and we waited for a Road Forman of Engines who was on a SB freight to arrive and get us help. He got it going and we were running about 45 minutes late. At Williams Lake, the crew changed and a senior Engineer took the controls and he was determined to make up the time. Forget about speed limits, this was his territory and we were exceeding the speed limit. I had an ETT and IIRC the passenger speed limit was 70 and some curves were 50 mph. We entered one 50 mph curve at 70 and about halfway thrugh it we were down to 60, and he opened the throttle. The Budd car felt like it was trying to climb the rail as the feeling was like the wheel was lifting up and dropping down. Not the side bang that I experienced on the above Amtrak trip. The fun thing on the BC rail trip that I would not have seen if I was not riding up front was a black bear that almost got goosed by us. It was loping along the track as we approached and didn't seem to want to get off the ROW. I was thinking this might get messy but when we got to within about ten feet, it went to the side and lived. We arrived in Prince George about ten minutes late. So my question is, what might cause a sharp side impact sensation on a passenger car taking a curve at speed?
I've felt that, too. To me, it always seemed to be some track misalignment coupled with the truck suspension running out of lateral suspension and hitting the stop. I don't believe every vehicle in the train experience the jolt. It was just an unlucky combination of an unperfect spot in the track, plus not quite up to par truck suspension plus where the car was in at the moment in it's lateral suspension travel. Not pleasant at all.
Simple answer without more data is flange climb. Used to experience it regurlarly on the Bakerloo Line on the curve between the Regents Park and Baker St stations when riding in trailer cars.
JL ChicagoI'm pretty sure that the Chicago CTA still use cylindrical wheels. Several CERA books I have document this although I admit they're from the 1980s and 1990s. But that explains the very loud squeel of CTA trains at speed. And probably the lurchings as well.
Those short CTA cars probably need it to keep hunting down to a dull roar as the wheels wear. The longer the car, the higher the hunting threshold.
Unfortunately the reality is that this year's "'off the shelf' modern modules" quickly become last year's antiquity in electronics. Sourcing replacement components will continue to be an issue when life cycle of most rail equipment far exceeds that of the electronics design and manufacture.
And this on top of the $1M per mile installation of those rail dampers between Balboa Park and Daly City, which are supposed to among other things reduce
... the well-known screeching noise when trains travel over the track.
That the screeching is not all that well-known on better-designed systems is perhaps relevant here.
oltmanndThey were using cylindrical? What the heck for?
Because some engineers 50 years ago thought they had 'a better idea':
http://sf.streetsblog.org/2016/04/07/new-bart-cars-show-agency-is-on-the-right-track/
http://www.sfgate.com/bayarea/article/BART-set-to-turn-down-the-volume-on-screeching-9196353.php
BART is notorious for not correcting other bad decisions made at the project start like, for instance, putting carpet on the car floors. Predictably, they looked and Smelled bad after a few years but they only started using rubber floor mats recently.
Ironically, one of the better ideas that worked were the advanced electronic control systems. It has been a nightmare to source replacement components for what is now truly ancient technology, so hopefully the replacement cars will use more 'off the shelf' modern modules.
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all the Chicago area Insull electric roads used cylindrical, I believe CTA still does, not sure about the South Shore.
BART is starting to use a "slightly tapered" wheel profile designed with its new generation of equipment.
http://m.railwayage.com/index.php/passenger/rapid-transit/bart-revised-wheel-profile-quiets-flange-squeal.html
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