Moving Target on rail system design discussion

[me171722]

Hello,

I am working on a target system that needs to move lineally and have a few things I would like to ask the community about.

Attached is a simple diagram of the system but it is basically a cart that attaches to a rail using a carriage ( either roller bearing carriage or sleeve bearings). To move the carriage my idea is to have a cable, belt or chain attached to either side of the carriage and a motor spinning this power transfer device at one end and a free spinning pully at the other. This rail will likely need to be pretty long 50-100 feet and the implications of that are what drive most of my questions below.

Questions:
1. The best power transfer device. I feel a cable seems the easier at this length as I am not aware of belts this long and chains seem heavy and unnecessary
1a. If I use a steel cable what's a good way of transferring power from motor to cable without slippage ect. I
imagine some wheel with a grippy surface to grab the cable but am curious if anyone knows of anything
already out in the market

2. Anyone have experience using sleeve bearings on a standard T-slot fittings as these allows me to use cheap and already long chunks of T-slot fittings from mcmaster ?

3. Any additional comments on design or good starting point for motor to use for this application

 

[3DDave]

You uploaded, but did not attach whatever you thought you did.

I would probably think to put batteries and motor on the device rather than adding a large amount of mass to the motion control problem. Look at the Blue Chip CNC for a way to use a chain.

 

[me171722]

Thank you for letting me know about upload (I have attached drawing here). I thought about that as well and with long distance having the motor on the track using a rotating wheel on the track could make sense, however, the distance to the target is critical and although it can be calibrated regularly I feel this kind of system would result in more error but I could be wrong.

Thanks for the input

 

[racookpe1978]

Horizontal movement for 50 meters?
Loads going on the trolley up-down (like from a crane)?
Trolley is start-stop-reveres-start-stop-reverse? Not continuous motion?

 

[me171722]

Yes. This device is moving horizontally so this view is from the top down. The trolly will have a small vertical load on it but shouldn't be more than 10#.
The motion will be stopping at discrete distances for a short time and then moving to next distance so being able to control motor is important

Hope this helps clarify and next time I will be more precise in original post

 

[handleman]

Discussion probably belongs here:
forum1528

 

[Strong]

If the target is stopped and then shot at there should be no vibration issue with carriage bearings and track. I would consider spring-loaded plastic bearing pads that can grip the T-track for stability (lateral and rocking). Have you considered two steel or plastic tubes spaced apart by supports/anchors to use as a track? I guess you have to specify tolerance/accuracy of track/carriage elevation and lateral position.

Walt

 

[BrianPetersen]

So many unanswered questions.
- Positional accuracy required
- Operating environment (clean? dirty? food-grade? outdoors?)
- Speed
- Frequency of operation
- Expected lifetime
... and that's only the start.

 

[MacGyverS2000]

I'd say look at how a ski lift is built...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[racookpe1978]

Well, if it is a shooting target (as implied) then a little vibration would be irritating, but positional inaccuracy not that critical - compare to a food loading or canning operation where the cart must stop precisely in place to put the lid on or squirt food into a bottle or decoratively on to the top of a food item.

But, what is the failure if a stray shot hits the device or track? Inconvenient only until it can be fixed? Or critical failure if it's during a tournament or for-fee shooting event when time is limiting?

 

[me171722]

Thanks for all the replies and I wish I had more information but I am just beginning this design and currently have limited requirements. I was thinking of used two tracks but the position of the tracks in relation to one another sounds like a real headache vs. a single track.

Some clarification:
1. This device will be used to calibrate a laser system so will only be shot with photons
2. This does mean positional accuracy is important, however, I'm thinking about eliminating this by having laser device on mount with very precise laser range finder to help with calibration of device
3. This will be used in a warehouse environment
4. Speed is not super critical and lifetime and frequency of operation is still to be determined.

Thanks for all the feedback and sorry for lack of clarity but wanted to reach out wile brain storming ideas and see if anyone has seen anything similar or had any input.

Carriages I'm looking at:
Bushing style:

https://www.mcmaster.com/47065t967

Ball bearing style:

https://www.mcmaster.com/6709k22

 

[racookpe1978]

OK, OK, OK.

So after you shoot it with lasers, you could do a couple of things.

Shoot at it with really BIG lasers for a while. A very short while, but still.
Shoot at it with really visible medium sized lasers, but add a "dodge" controller so the thing tries to move randomly whenever a laser inbound shot is sensed by the on-board laser meters. (Could require a second "re-aiming" sensor and targetting device on the medium laser shooter-aimer device so the new position is shot as well.)
Shoot at it with regular shotguns - just for fun and dis-assembly.
Shoot at it with a 3 inch mortar as it runs back and forth. Just to see if random shells falling from a great altitude would ever hit the target.

 

[IRstuff]

Why not just put it on HO train track? Put a Raspberry Pi or Arduino to control the motor; you could possibly use a printed scale that a camera can look at an determine its position.

You did not state the required positional accuracy. A theodolite could get down to mm-scale accuracies, and an RTK GPS receiver could easily get down to sub-cm scale

https://store.emlid.com/product/reachm-plus/

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[tygerdawg]

There are so many options for building a linear track to do this. Google-search for "light duty track rail" or similar search strings and see the dozens of images for ideas and vendors. Systems from $ to $$$$$ could be configured depending on your needs. You could select a suitable rail system, develop mounting system designs, specify & purchase a long timing belt (some are available in this length because they are cut in a spiral from a large drum), and drive it with a stepper motor with open-loop programmable indexer capability.

But accurate positioning on a 50-100 foot track in a warehouse with cracked and wavy floors will be a mechanical challenge.
All is moot until you specify your required positional accuracy.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[tygerdawg]

My entry got corrupted somehow.
It should read $ to $$$$$

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[tygerdawg]

Wow must be a control code glitch. should read dollar sign to five dollar signs

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[me171722]

Thanks for all the input and with positional accuracy being important I am going down the design route of using a laser range finder so I have an accurate position when measurements are taken and can greatly open up the mechanical positional constraints which would be very challenging and costly to tackle. A light rail system is a solid idea as the target will be pretty large 2 meters by 2 meters so I may need a wider base for stability




and for the sake of testing $$$$$

 

[itsmoked]

I've got a buddy who builds 1/8th scale train stuff.

He also has a three track-rail train yard (full size) and services rail equipment nationwide. He's pretty lightly employed at the moment because the idiot running Amtrak hates private rail cars.


Anyway, that scale would probably be very effective for your targets. It's a widely supported size as there are parks of enthusiasts at that scale where they put down hundreds of yards of scale track and everyone rides scaled down trains brought in from all over the place at 'meets'.

That track could be laid and a battery powered VFD driven low cart could be used along with an encoder to run the target all over the place with different accelerations and speed profiles. A Y component could even be added on a base of that stability. That size lends itself to cost effective fabrication as it's not too big nor too small.

If you want to pursue this angle, I could connect you guys.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[IRstuff]

You've still not stated the positional accuracy; the answer to that question would appear to be the most critical design constraint.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[me171722]

itsmoked That's a great size and you mentioned and I will PM you if I go down this route. It does seem like a solid option and more inexpensive and versatile than a sled rail system

As for the positional accuracy I need to get this requirement better defined, however, my guess would be around .5-1mm. As I've previously said my plan is to tightly control the laser position to a highly accurate laser range finder and feed that data into the test so the accuracy of the mechanical system is not very important as I always know the position of the target in relationship to the laser device.

Thanks for all these suggestions. There are so many ways to do this and I really appreciate the different ideas mentioned here