Looking for a part, does it exist?

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The discussion revolves around finding a specific part for a project involving a smooth steel rod and a block that can slide along it while being electrically controlled to secure the block in place. The user is considering magnetic solutions or an electromagnet to achieve this functionality, emphasizing the need for the block to clamp onto the rod when necessary. Various suggestions, including solenoids and brake caliper systems, are proposed, but the user is focused on finding an existing device rather than building one from scratch. The project requires that the block remains loose when no electric current is applied, and the rod has a vertical movement range of about 30 inches while the block can only move within a 4-inch range. The conversation highlights the challenges in visualizing the mechanism and the importance of clear specifications in engineering discussions.
Averagesupernova
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I have a project in which I need to find a part that would work as follows:
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Imagine a smooth steel rod that is for instance .5 inches in diameter. Now imagine a block with a hole in it that fits around this rod. This block needs to slide easily and smoothly on the rod. However, sometimes I want to secure this block to the rod so it does not slide. It needs to be electrically controlled. At this point I'm thinking magnetic so it is just attracted to the rod. However, if it causes something inside the block to move and clamp to the rod that is fine too. This way the rod could be stainless steel or something non-magnetic. The duty cycle does not need to be 100%. Someone PLEASE tell me some type of device exists and point me where to find such a thing.
 
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I can't say I have ever seen or heard of anything like what you are looking for. The closest I can think of off the top of my head is a standard linear bearing/drill rod assembly with a hand actuated clamp.

Have you checked with any motion control specialists?
 
Of course, I would imagine something that doesn't exist. :frown: I have checked nowhere else at this point. It's something that popped into my head in the last hour or so as a solution. It NEEDS to be electrical. It will make enough on/off cycles for manual to be impractical.
 
Just because I don't know of anything doesn't mean they don't exist. I'll keep an eye out and ask some folks in the morning too.
 
I find it hard to believe such a thing does not exist also Fred. I really appreciate your effort. I'll keep following leads here on the 'net. There are a lot of motion control companies out there but I'm just not sure what you would call a part like this. Some kind of brake maybe?
 
Just curious, how heavy is this block?
 
It doesn't need to be very heavy at all. It is used as an indicator and to actuate a switch.
 
How big a switch, like the one to flip on a light?

Also, what/how is it indicating?
 
It might not even be a microswitch. I will most likely make it optical.
 
  • #10
Why can't it be fixed to the rod at some location, and the rod move up and down? It would be easier to clamp the rod at the base to hold the block.
 
  • #11
The rod already moves. Up to 30 inches. The block can only be allowed to move within a 4 inch range. So it needs to slide sometimes. I really don't care to explain any more.
 
  • #12
Top secret eh? :wink:

Well, without more information, it's going to be hard to know what's going on.
 
  • #13
Well, you don't need to know any more about what is 'going on'. I'm tied to what I've already explained. There is no way to 'move this other part instead'. The rod moves. Sometimes the block needs to move with it, sometimes it doesn't. It never moves very far before releasing.
 
  • #14
I don't know. Possibly an electromagnet?
 
  • #15
An electromagnet. That's the assumption cyrus. However, has someone packaged up a handy little device that does what I described?
 
  • #16
Nope, but I'll look online for ya.
 
  • #17
Hi Averagesupernova,

Averagesupernova said:
Well, you don't need to know any more about what is 'going on'. I'm tied to what I've already explained. There is no way to 'move this other part instead'. The rod moves. Sometimes the block needs to move with it, sometimes it doesn't. It never moves very far before releasing.

Just a suggestion: I (and I have found several other engineers) often have difficulty envisioning something described in words alone. Engineers live by drawings, and its why we always start a problem with (how many times have we heard this?) "Draw a Free Body Diagram". :biggrin:

From what I can gather from your write-ups it sounds a bit like an electro-magnetic solenoid might do the trick. This is a device with a solid core (through which current is passed) and the outer "block" could and would be the electromagnet. I know some solenoids with 1-2 inch throws, but I am not sure of 4 inches or more.

If you could do a simple drawing it might help us help you. A solenoid is a discrete (ON/OFF) device such that when you energize it the core is pulled to one extreme of travel and when de-energized a spring holds it at the other extreme. But if you want to be able to continuously vary the position of the rod through the block, then you might want to look at something like a jackscrew or an E/M piston. More power required to operate these devices, however.

Another question that could be important: What sort of external loads might be applied to either the rod or the block?

Rainman
 
  • #18
If I were to build something to that requirement, I'd score the top of the rod with a ****load of 'v'-shaped serrations and incorporate a wedge-shaped solenoid plunger into the block.
 
  • #19
I'm quite familiar with solenoids rainman. The would be device will ride on a vertical rod/rail. It is to slide freely until power is applied. Then it must clamp tightly onto the rod/rail. It is actually part of a motion control project. The would be device pulls an armature and squeezes the rod/rail or if it can just attract itself to the rod/rail strong enough to hold itself against gravity without actually 'clamping' the rod/rail then that is fine too.
 
  • #20
So, something must be controlling this things up and down motion, or it will just fall. Why can't whatever is moving the block just stop?

Said differently, what is fixed and what is moving? The rod or the box. I take it the rod is fixed, and the block is moving, no?
 
  • #21
Hey, Rainman;
Didn't mean to step on your toes there. I didn't realize that there was a page-2 when I posted. :redface:
Average (sorry, I forgot... that's Mr. Supernova to me :biggrin: ), you can also, if you want to, incorporate a brake caliper system into the block, which can still be applied by a solenoid. All that you need is to carve out a section of the block and replace it with a grabber.
 
  • #22
cyrusabdollahi said:
So, something must be controlling this things up and down motion, or it will just fall. Why can't whatever is moving the block just stop?

Said differently, what is fixed and what is moving? The rod or the box. I take it the rod is fixed, and the block is moving, no?

Yes cyrus, something is controlling the rods up and down motion. That's part of the whole project. The rod moves. It has a range of about 30 inches vertically. The block can only move within about a 4 inch range. The block clamps down on the rod right before the rod is to move. When the rod stops, the block let's go. A weak spring will then pull the block up to the topmost position permitted by a stop. This distance that the spring has to pull is not likely ever more than about 4 inches. I had forgotten to mention the spring until now. Make sense?
 
  • #23
Danger said:
Hey, Rainman;
Didn't mean to step on your toes there. I didn't realize that there was a page-2 when I posted. :redface:
Average (sorry, I forgot... that's Mr. Supernova to me :biggrin: ), you can also, if you want to, incorporate a brake caliper system into the block, which can still be applied by a solenoid. All that you need is to carve out a section of the block and replace it with a grabber.

I'm thinking along the lines of a brake caliper Danger but I'm hoping something exists already. Actually, I know for a fact that they do in the searching I've done in the last hour or so, but they are pneumatic and that is not an option for me. It is also important that a no electric current condition leaves the block loose.
 
  • #24
Well, I'm of no use to you. Good luck in finding a solution.
 
  • #25
Averagesupernova said:
they are pneumatic and that is not an option for me.
Maybe this is just because I'm used to jerry-rigging stuff (see my post in the Rube Goldberg thread in GD), but this doesn't seem like a problem to me. To start with, I'd build it myself... which doesn't seem to be an option in your case. Elsewise, though, why not just replace the pneumatic cylinder with a solenoid? :confused:
 
  • #26
This is a production level project danger.
 
  • #27
Hi again,

OK, in reading your last few replies it seems clear to me that what you want is a linear Electro Magnetic Actuator (EMA). My former employer, the venerable Parker-Hannifin "gods" of electro-hydraulic actuation, have been investing heavily in developing EMA technology for aircraft because (duh!) it gets rid of the need for hydraulics. As such, since it is bleeding edge tech, you can expect to pay top dollar for it. But it is available:

http://www.yet2.com/app/insight/techofweek/7466

As I mentioned in my other reply, an assessment and analysis of the loads (static and dynamic) is in order to be able to size the EMA.

Rainman
 
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  • #28
Not even close Rainman. Please re-read this thread. The rod already moves on its own. I don't need a linear actuator.
 
  • #29
Look guy,
Averagesupernova said:
Not even close Rainman. Please re-read this thread.
If you're going to get snooty when I am trying to help you, then why don't you take my other advice and do a drawing? And to be snooty right back, I'd suggest you learn how to write specs. You'll need that talent:
The block clamps down on the rod right before the rod is to move. When the rod stops, the block let's go. (snip) Make sense?

No, to be honest, it doesn't. You say the block clamps down BEFORE the rod is to move. Then you say the block let's go when the rod stops. How about describing the motion itself because I am not understanding your description where it is only talking about a static block. Again, engineers work with drawings. I cannot imagine having to design a complex motin system based on words alone.

Rainman
 
  • #30
Averagesupernova said:
This is a production level project danger.

I don't know what that means. Is it then to be something applied to a commercial product that your company will be selling? If that's the case, I'm outta here.
 
  • #31
RainmanAero said:
Look guy,

If you're going to get snooty when I am trying to help you, then why don't you take my other advice and do a drawing? And to be snooty right back, I'd suggest you learn how to write specs. You'll need that talent:


No, to be honest, it doesn't. You say the block clamps down BEFORE the rod is to move. Then you say the block let's go when the rod stops. How about describing the motion itself because I am not understanding your description where it is only talking about a static block. Again, engineers work with drawings. I cannot imagine having to design a complex motin system based on words alone.

Rainman

I think he's just stressed over his project. :-p

I felt his pain last week.
 
  • #32
I just realized that my last post might have appeared a bit harsh. It wasn't my intent to say that I won't assist in a commercial endeavour; I'm just not qualified to do so. There are too many constraints and liabilities and financial factors for someone like me to deal with.
 
  • #33
I'm no more stressed than usual Cyrus. LOL Danger, I'm wondering why you'd choose to duck out if this is to be sold commercially? While I'll defend anyones right to decline participation in a thread please realize that I'm not asking anyone to design this. I'm asking if a certain part exists. Everyone please concentrate on this instead of questioning what I'm doing, what this is for, suggesting better ways to do it, etc. This sort of thing just adds confusion to the thread. I believe the descriptions I've written thus far in the thread should be enough to get my point across. If not, I'm very sorry. I do not plan on writing any kind of specs until I get a sample part in my hand. I have some flexibility in the devices size and orientation. Writing specs for something that is not available off the shelf that I have no intention of manufacturing myself or having someone else manufacture is a complete waste of my time. I fully realize that the engineering world works in drawings and specs but my situation is comparable to me asking General Motors if they have anything in flying cars and they ask me to write up a spec for it.
 
  • #34
Hey Danger you posted before I was done typing my last thread. You may think you have no qualifications in something but that is not necessarily true. I have countless times had someone who was much less than qualified give me an example of where something similar is used and at least given me a lead. Just keep in mind that I'd like something off-the-shelf.
 
  • #35
Well, then Rainmain is correct I'm afraid. No picture = No help.
 
  • #36
You might want to make a prototype block, using a small solenoid to apply the clamping force. Drill a hole through the block and mount the solenoid so that when activated, its ram presses radially inward. The brake shoe could be as simple as a cylinder of teflon threaded onto the ram with a bit of rubber epoxied to the end. When power is discontinued, the solenoid retracts and the block slides freely. If I'm imagining this correctly, you will want the block to actuate a switch that shuts off power to the solenoid when the block hits its lower limit, then the solenoid ram will retract and the spring will pull the block back to the upper limit. If you have a machine shop and can prototype this block, you will have a chance to refine it before contracting for a production run.

Note: I said production run, because what you're asking for probably does not exist in a form that you would find usable. Your best bet is to prototype it, then get bids for a production run large enough to fill your needs and large enough to keep the per-unit cost down.
 
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  • #37
Okay, I'm back in. :biggrin:
The main thing that I see as a problem is that you're going to have to do some kind of fabrication just to make whatever you find fit into your system. No way will you find something 'off the shelf' that is exactly the right size and shape and has the mounting holes in the right place and etc..
I have an 'iffy' idea about a component that already exists, but you'd still have to build mounting brackets. What I'm thinking of is the fast-idle solenoid from a carbeurator. You could just cram a chunk of rubber (maybe a vacuum cap) onto the end of the plunger and have it poke the side of the rod. There's some good force in those things.
The other thing that I might suggest would be an iris diaphram that encircles the rod. They're pretty expensive, but you can get them at optical houses (maybe even camera stores). If I'm not mistaken, they can be had with actuator motors or solenoids already attached. I have no idea what kind of clamping force you could get out of one, though.
 
  • #38
As a prof of systems engineering, I feel I should address some fallacies and typical causes of problems down the road:
Averagesupernova said:
Everyone please concentrate on this instead of questioning what I'm doing, what this is for, suggesting better ways to do it, etc. This sort of thing just adds confusion to the thread.
Knowledge is a tricky thing. Passing on knowledge is even trickier if your media for doing so is limited. The fact that we are asking questions (to try to visualize) means WE are the ones who are already confused. Your saying this adds confusion to the thread is not borne-out by the fact that you "forgot about the spring" initially, and who knows if that may have not come out but for our questioning. "Forgetting" about key requirements or elements is quite common. It is why systems engineering (up-front) is so crucial to success. That is why we call it "requirements DISCOVERY". :smile:
I believe the descriptions I've written thus far in the thread should be enough to get my point across. If not, I'm very sorry.
One of the greatest tests for a systems engineer who derives & writes technical requirements is this: Take it to THREE other engineers, each of differing speciality disciplines. Ask them to give their interpretation of what is wanted. If all three give reasonably similar interpretations, you have at least an adequate requirement.
I do not plan on writing any kind of specs until I get a sample part in my hand.
MAJOR caution. This kind of thinking results in airplanes crashing, shuttles exploding, and much less severe (although not necessarily less costly) hazards. We live in a business environement where everyone wishes to make somethign with "off the shelf" components... before they have ever even studied their needs, modeled them, or analyzed them in detail. Sometimes, there is no "shelf". How do you think some of us write specs when there IS no part we can hold in our hands?

I have some flexibility in the devices size and orientation. Writing specs for something that is not available off the shelf that I have no intention of manufacturing myself or having someone else manufacture is a complete waste of my time.
I don't often speak this frankly, but you are completely wrong. I deal with this attitude with students and with professional engineers who should know better. Ignorance of requirements and how they are developed is THE SINGLE MOST-CITED "lesson learned" on any failed program. There is at least one spec (I know there are more) which is certainly not a waste of your time... and I have asked you about it and you have not answered. Loading. In fact, this is the MOST IMPORTANT question with regard to size of the device you are looking for, its holding force, and if it is E/M actuated, the power required to hold said load.

I fully realize that the engineering world works in drawings and specs but my situation is comparable to me asking General Motors if they have anything in flying cars and they ask me to write up a spec for it.
I'm not buying that analogy. I think you are making an excuse to be lazy. (Just my opinion). I see it all the time in students.

Like I said, I am willing to help. But if you are going to not answer questions and insist that your way is adequate enough (even though more people than me seem to be confused) then you have not learned enough about engineering to succeed. Sorry, but I call 'em as I see 'em.

Rainman
 
  • #39
Amen!

Actually I would go a one step further than RainmanAero. I could easily think of 10 or 20 questions I would want to know about this device before I could make any rational suggestions about how to design it, but those questions are not the ones to ask first. The first question is very simple, but given the way this thread is going I doubt we will get an answer to it.

The question is: What is the FUNCTION of this device? If we knew that, I bet somebody could come up with a different way of implementing the function that WAS available off the shelf.
 
  • #40
What I am envisioning is a linear bearing that is a standard, off the shelf item. However, this bearing would have some kind of electronic capability that when energized, the bearing locks in place so it, or the rail in this case, can not move. The electromagnetic equivilent to brake shoes.
 
  • #41
It sounds like what you want is an electromagnetic actuator (isn't that what they're called?).

Apply voltage and the piston moves. Bolt the thing in place on the block, and the piston will pop out and bind on the rod, stopping the block.

You could set up the switch any way you want, toggle on/off, pushbutton mometary on, momentary off, etc.


These should be available sold by the kilogram in your local electronics surplus store.
 
  • #42
Hi Dave,
DaveC426913 said:
It sounds like what you want is an electromagnetic actuator (isn't that what they're called?).

I was told an electromagnetic actuator was "not even close" (see above).

I guess as long as we are shooting in the dark (or at least dusk), then I should also mention the magnetic brake which operates on Lenz's Law. It does not even require power, but depending upon the details of how this device has to FUNCTION (kudos to AlephZero who certainly understands systems engineering) it may not be the right part. In any event, here are some details (and diagrams) of one type of magnetic brake.

http://www.cst.com/Content/Articles/article115.aspx

Rainman
 
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  • #43
Well, those suggestions might be the answer or they might not. We don't know what speed this thing is supposed to work at - does it move with accelerations of 0.0001G or 10,000G? What's force spectrum (noise, vibration, acceleration of the device that it's built into) it will feel when it's supposed to be "locked"? What envionment is it supposed to work in (temperature, pressure, lubrication, corrosion? What's the failsafe condition? Etc, etc...

Without a spec (which we have been told we are not going to get) we are just p*ssing in the wind here.
 
  • #44
Given the circumstances here, I think we can safely assume that it's not going to be in a nuclear environment experiencing 1000 g's.

Honestly, I saw this as a question as to whether anything like this existed prepackaged. I didn't see any requests to help with the design or anything else. It's not improper for someone to ask if something exists and then to look at the item's specs to see if it fits their needs. If detailed design criteria is not presented at the beginning then the OP is taking on the responsibility of deciding what is important information to pass along.
 
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  • #45
I agree with Fred on this. It's just a matter of throwing a bunch of ideas at the wall and seeing what sticks.
 
  • #46
Thank you Fred and Danger. I haven't posted recently because I don't want to get into some kind of p!ssing contest with some of the other posters. Sometimes I have a hard to from keeping my mouth shut when it's in my best ineterest so I have decided to let this ride for a few days. I have had some ideas on my own that could possibly make this piece a lot easier to manufacture than I had originally envisioned. In the meantime though, something prepackaged and off the shelf would be welcome. There really is no requirement that the device needs to slide along a rod. Envision a brake caliper sliding along a flat rail. I still prefer the rod because the would be device inherently surounds the rod completely and cannot move sideways. Naturally it is assumed I will have to fabricate something to mount to it to make it interact with the rest of the machine.
 
  • #47
Well, it not having to be a rod makes a world of difference. There is such a thing as you're looking for that works on flat material. Unfortunately, I can't remember what the hell it is. I can picture it in my mind, but not in the context in which it's used. Some sort of a maniplator claw...
I'll keep thinking on it.
 
  • #48
Danger said:
Well, it not having to be a rod makes a world of difference. There is such a thing as you're looking for that works on flat material. Unfortunately, I can't remember what the hell it is. I can picture it in my mind, but not in the context in which it's used. Some sort of a maniplator claw...
I'll keep thinking on it.
Are you thinking of a cam-actuated gripper, similar to those used to hoist large sheets of iron?
 
  • #49
Grippers, clamps, etc. you can name a whole bunch of things but they are all pneumatic.
 
  • #50
No, but I did just remember what it was. Some old-style jukeboxes used something like that to pick a record from the rack and put it on the turntable.

edit: Just saw your post, Average. These things were not pneumatic.
 
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