The whole idea of a geometry car seems daunting because of the number of tests required. Why not start out with something simple like a car that measures track gauge in decimals. As it runs around the track, a green LED would be lit to show in gauge and a red LED to show out of gauge.
Rich
Alton Junction
Here are some basic cars I made using Tichy trucks, Intermountain wheelsets and #148 Kadees.
The plastic was given to me so I have no details on it.
gregcordered I2C compatible MPU 6050
https://circuitcellar.com/wp-content/uploads/2012/06/CC2012050461.pdf
gregc 7j43k If ALL of you are incompetent in this matter, you DO have a problem! don't understand how such comments help with the design of a geometry car ??
7j43k If ALL of you are incompetent in this matter, you DO have a problem!
don't understand how such comments help with the design of a geometry car ??
You are quite correct that it doesn't help with the design.
It questions the NEED for such a device, at least one as complex as you want to build.
I can see that you are beyond this question, so any further comments from me will be on the design, only.
Ed
ordered I2C compatible MPU 6050
greg - Philadelphia & Reading / Reading
gregca single car with accelerometer would handle 3 dimensions and code would be fairly cookbook, just a matter of recognizing a big enough jolt in any direction and turning on an LED.
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OvermodI don't think it would be rocket science to make something with two cameras
i don't think a camera is infeasible, but have little experience with image processing.
OvermodMy two cents here is that perhaps one railcar shouldn't take all these measurements.
i've suggested "different cars with different purposes". i doubt all the electronics and any mechanical stuff could fit on a single car.
a single car with accelerometer would handle 3 dimensions and code would be fairly cookbook, just a matter of recognizing a big enough jolt in any direction and turning on an LED. still unsure about recognizing a lack of easement
OvermodI do not know if weighting the car to give a better inertial reference frame
i wondered about this. the accelerometer needs to move to register. so the wheels need to have little lateral or vertical play and the platform needs to be light (but not too light)
My appologies.
I stayed out of this topic because it seemed? I don't know a polite word? Not necessary......
I was only courious to understand the track problems you are facing.
You are a better man than me, I would just tell them/him "this is not the right way to do this, and the workmanship is sub par".
I build things for a living. After having the opportunities in life to be a "boss", an engineer, an "office worker", I found much more satisfaction (and just as much money) in actually creating the finished product.
Much of what I do is designed and built by my hands.
I have little tollerence for lack of skill, or poor workmanship.
I know this is just a hobby, but it requires skills......
Sheldon
ATLANTIC CENTRALJust my opinion, but I don't see any one railcar tracking in a way to accurately take these measurements.
I have no question about using small high-resolution cameras or 'mouse sensors' in a track-geometry project, as an enormous amount of the work in making the devices and their interfaces is now at obsolescent-cheap levels of cost (thanks to many generations of feature-packed phones, high-resolution gaming and CAD pointing devices, structured light experimentation, etc.)
I don't think it would be rocket science to make something with two cameras with acceptable width of field and an appropriate light source (perhaps polyspectral) to allow small device aperture and hence long depth of field for resolution). A similar arrangement with cameras in quadrature could remotely sense the end of the elongated indicator wire or pointer to get long baseline that was mentioned earlier, with far more precision than I think a commercial accelerometer core might practically furnish.
I do not know if weighting the car to give a better inertial reference frame is going to work at smaller scales -- it should for short track defects traversed relatively quickly, but it would have to be tried and tinkered with.
ATLANTIC CENTRALBut What do I know...
wow
gregc at some point, i'm imagining this car being part of a train during operation. having a sounder (beeper) and leds visible from either side. it would generate a beep when a defect is detected and turn on an LED for a short time (~5 sec). different colored leds would indicate a verticle, horizontal, ... displacements using accelerometer. sensitivity would need to be made adjustable, presumably made more sensitive as more major problems are corrected (is this pie in the sky? the interlock project started pre-covid is finally getting installed)
at some point, i'm imagining this car being part of a train during operation. having a sounder (beeper) and leds visible from either side.
it would generate a beep when a defect is detected and turn on an LED for a short time (~5 sec). different colored leds would indicate a verticle, horizontal, ... displacements using accelerometer.
sensitivity would need to be made adjustable, presumably made more sensitive as more major problems are corrected
(is this pie in the sky? the interlock project started pre-covid is finally getting installed)
The interlock project is interesting, and that is likely as good of an approach as any. But I could easily do that with about 30 ice cube relays @ $3 each - given we would both need the same buttons and lights, what did you spend on hardware?
In fact my staging yards will all have one button route control, and my interlockings will be similar requiring only one to three buttons to fully select routes.
Just my opinion, but I don't see any one railcar tracking in a way to accurately take these measurements.
But What do I know...
hgodlingIf you want to go the optical route, you want to be sure there is nothing between the camera and the track
no camera. had suggested using reflection off top of rail to measure gauge using narrow slotted apertures.
wouldn't expect that approach to work with points. thinking accelerometer may detect a wide point
7j43kIf ALL of you are incompetent in this matter, you DO have a problem!
the east end trackwork (only partially shown in right hand photo) was similarly constructed and works. eyeball inspections and testing with cars identified problems that were corrected.
there's little need for a geometry car if there are no problems. with so many turnouts a geometry car can hopefully identify problems less noticable by eye/feel, without having to get on top of the layout.
gregc i think it would be helpfull to be able to detect a point that is not tight against the stock rail using a geometry car and am now becoming more curious what an accelerometer can do
i think it would be helpfull to be able to detect a point that is not tight against the stock rail using a geometry car and am now becoming more curious what an accelerometer can do
I am not understanding why your eyeball is not telling you a point "is not tight against the stock rail".
If it cannot, perhaps you should find someone else to build turnouts.
If ALL of you are incompetent in this matter, you DO have a problem!
gregc ATLANTIC CENTRAL First, what do you mean by alignment of points? Length? Gap on open side? Gauge? these are fasttrack turnouts. 35+ on the west end of a passenger station, many more on the east end which took very long to get working there are inconsistencies in construction. solder blobs between the points and stock rail preventing tight closer. distance between the points is narrow requiring more switch machine travel. throwbar is tight requiring more switch machine force turnout not spiked near throwbar as well as other problems as we've been installing switch machines, manual inspection, some filing, bending, spiking and resoldering fixed many issues allowing a car to properly track both turnout routes using a tortoise machine to switch the points. expect more issues with trains i think it would be helpfull to be able to detect a point that is not tight against the stock rail using a geometry car and am now becoming more curious what an accelerometer can do please recognize this thread is about the a geometry car, not layout construction. this is what has been done and is not going to be replaced (not my layout). of course you may not do it this way on your layout.
ATLANTIC CENTRAL First, what do you mean by alignment of points? Length? Gap on open side? Gauge?
these are fasttrack turnouts. 35+ on the west end of a passenger station, many more on the east end which took very long to get working
there are inconsistencies in construction.
as we've been installing switch machines, manual inspection, some filing, bending, spiking and resoldering fixed many issues allowing a car to properly track both turnout routes using a tortoise machine to switch the points. expect more issues with trains
please recognize this thread is about the a geometry car, not layout construction. this is what has been done and is not going to be replaced (not my layout).
of course you may not do it this way on your layout.
I will go back to sleep now and leave you to it. Seems to me you just need someone who knows how to lay track.
If you want to go the optical route, you want to be sure there is nothing between the camera and the track. Even clear pieces will distort the image and mess with the contract making things more difficult.
There is a software called OpenCV that you may find helpful. I don't know if this runs on an Arduino. I know a few people that have had some success in object tracking in openCV. It has a bunch of libraries that may save you some time and keep you from reinventing the wheel.
ATLANTIC CENTRALFirst, what do you mean by alignment of points? Length? Gap on open side? Gauge?
gregc gregc i'm working on a layout with a lot of hand built turnouts with lots of issues. And would not be surprised if problems develop with use especially interested in alignment of points. (how?)
gregc i'm working on a layout with a lot of hand built turnouts with lots of issues. And would not be surprised if problems develop with use
especially interested in alignment of points. (how?)
OK, now I have some questions.
First, what do you mean by alignment of points? Length? Gap on open side? Gauge?
Second, what is the method of turnout construction? Fastracks? Why are turnouts in place without ties? Is that paper under all of this with the track plan?
What is under the paper? Does the paper stay? (seems like a bad idea to me)
I don't a have a detailed track plan to understand, but just in these two photos I see track geometry that makes little sense and seems less than ideal.
When I need or want to, I have been hand laying track and turnouts since the early 70's, and everyone has their own methods and were taught different approaches, but I see a lot going on here I would not be doing.
There are a few S curve alignments the prototype would not even tolerate in a yard?
Is that commercial track? Then why are we hand laying turnouts?
gregci'm working on a layout with a lot of hand built turnouts with lots of issues. And would not be surprised if problems develop with use
7j43k It does seem that there's no need for this after-the-fact tool if the layout builder did it right the first time. And if he didn't, the time to have caught it is during initial construction, when there's not any scenery in place. I think there is a possible use for one in modular setups, where the joints may need fine tuning, or someone brings a module that has awful trackwork. Just run it around the mainline and see if it squawks. Loudly. There ARE egos big enough, by the way, to get offended when it is pointed out that their module has awful trackwork. "Really? YOU'RE offended? WE have to deal with this thing." Ed
It does seem that there's no need for this after-the-fact tool if the layout builder did it right the first time. And if he didn't, the time to have caught it is during initial construction, when there's not any scenery in place.
I think there is a possible use for one in modular setups, where the joints may need fine tuning, or someone brings a module that has awful trackwork. Just run it around the mainline and see if it squawks. Loudly.
There ARE egos big enough, by the way, to get offended when it is pointed out that their module has awful trackwork. "Really? YOU'RE offended? WE have to deal with this thing."
Just one reason why I have decided that clubs or modular groups are no longer my cup of tea. I will build my railroad, then invite those who I desire, and who are interested, to come play.
I measured the "straighness" of my trackwork with a lazer after the fact when asked about getting track perfectly straight:
Since I have never had these issues Greg is referring to, even when I was only 15 and hand laying/building my own turnouts, I would have no need for his proposed tool.
I can't imagine measuring gauge effectively in a 'model' context any way but optically, probably reading the railheads or point structure with a magnified camera input and using optical-mouse approaches for edge detection and discrimination.
A problem that remains is the absolute reference or baseline that the car would use. Inertial is nonstarting; accelerometers even remotely practical in this application, as noted, are useful only for short-period differential.
I suspect there may be a use for making the car capable of 'telemetering' data or storing it quickly on board, and only processing to find flaws 'later'. Although there is a sort of elegant satisfaction (to me at least) in the prospect of a scale Sperry car that goes around the layout making tiny colored marks on the rails corresponding to type and severity of defects...
I suspect making a "gage checker" is doable, using Greg's spring-loaded individual wheels.
A problem shows up, though, when the gage checker goes through a frog. It's especially bad when it approaches from the pointy end, as the wheel that approaches the frog will be spring-loaded to take the other route.
And you have a big mess.
While all the other information described is nice, my main goal would be vertical changes. That is simple to do, though the way-cool alarm system and flashing lights is a bit more work.
One POSSIBLE super simple method would be to connect the two test cars with couplers that have had their knuckles filed down to a lesser than normal height, say, arbitrarily, half the normal knuckle height.
If the car(s) separate, you gotta fix it!
Looking at the NMRA standard the tolerance for gauge in HO is only +/-0.006 in. It is hard to find a device that can measure that accurately, let alone while moving and getting it to fit on a car. I think the wobble in the mounting of the trucks would exceed any error you are looking for in the track.
To judge the easement you need the slope of the acceleration. This is very hard to get from an accel. Accels tend to be very noisy (even the very expensive $1k ones). Phone use filters to make it work, but anything we would be interested would be very short, and likely filtered out along with the noise.
I have thought about putting a magnet on a flat car so I can mount a digital level to measure the grade.
I think it would be hard to get a car that would be more useful then your NMRA gauge and running your finger along the track. However, even if it doesn't work real well, it sounds like it could be a fun project and could make for an interesting conversation piece when showing off the layout.
gregc not sure how to measure gauge. which is more critical too tight or too wide?
not sure how to measure gauge.
which is more critical too tight or too wide?