I'm seeing, get this --·a collapsible Trebuchet on glide-rails (instead of wheels), platform-mounted on the FHR/5HR, or maybe the StingRay, whatever, hurling thermite grenades, by remote control.· That'd be awesome.
Post Edit -- And use the artificial horizon from Harprit's·new book on "Spin" to keep the trebuchet platform level.
Actually the rebreathers the SEALS use are not Heliox rebreathers (at least the ones they use for covert insertion/extraction). Do a web search for LAR-5. This greatly simplifies their design vs. heliox rebreathers, but I think they're not intended to be used below 21 feet in depth.
You have been taking quite a beating here.... much of it undeserved, but to some degree understandably because you have stated some lofty goals using some materials that could be dangerous if not used properly, but mostly, I think, because of insufficient explanation of your plans.
However, I believe you to be an industrious and inquisitive fellow in search of solutions to somewhat wild ideas on a shoe-string budget, and to aid you in your quest I am sending you a used analog style (tube screen, digital memory) older dual channel Tektronix oscilloscope that I no longer have a use for.
I upgrade scopes every couple of years, and it will have a much better remaining life in your hands than on my shelf where it's future will be the trash bin.
I have your co-ordinates from UPEW, so it will ship today.
Learn lots, have fun but above all, in a safe manner.
pjv.
Good for you. I have been trying to offer some real engineering input here rather than just trash talk. I just felt that experiments with thermite isn't something to inspire over the web. It all started out very vague, as if someone really wasn't trying to build something.
Tektronix product is very nice. I had a rather huge old dual channel with vacuum tubes that I picked up for about $30USD at a Foothill College HAM swap meet. I think it was up to 20Mhz. Rather large, but very useful. But that was long before BasicStamps were available.
If you run into any of those old vacuum tube scopes with plug in front ends, the dual channel one can be cannibalized and makes an extremely nice stereo audio pre-amp. Absolutely flat response from 1Hz through audio and way way beyond. It runs on 12AX7 matched pairs and I bought a dozen sets for about 25 cents a pair at the same time. They actually used silver circuit boards to bring down the resistance.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Ain't gadetry a wonderful thing?
That's very generous of you! An oscilloscope is an excellent tool, helps a person analyze a system, break it down and think it through step by step. I love explosions, and rockets hitting Mach 6 at sea level, had my fair share of near-death experiences and "Oh look, guys, and I've still got all my fingers!" But some of the most exciting experiences I've ever had were watching small traces wiggle across the face of an oscilloscope tube. Thanks to instruments like that, there are times when you feel that you've seen the invisible and accomplished the impossible.
Alright, I give in. Here's a full explanation of my new plan:
Although thermite is great, I think I'll go for an omni-fuel source of energy instead. The Core where it is burned will be made of cement or metal depending on what I decide is best later on. It will have a valve for liquid and gas fuel intake, and an intake for air. It may also have an auger for solid fuel intake/solid fuel output. There will be an ignitor so the engine will only burn fuel when necessary. Around this core will be metal tubing for water to turn to steam, and there will be two or more of these so the steam can constantly flow even when one of the pipes are reset.
Since the water is recycled, there will be a small water tank for each set of tubes. The valve on the pressure side must close before the valve to intake more water is opened. Once refilled it will go back to the previous position again and a small pump will push the water through as necessary, not requiring much force because of the equalization of the pressure in the tank to that of the line.
All the steam will go to a main set of tubing which stores the pressure until it can be used. This line will be kept near to the core to keep heated and insulated to prevent cooling and pressure loss. When it is used, a valve will be opened and it will blow into a metal cylinder where it will push against a divider between the steam and hydraulic fluid. Since the hydraulic fluid can stretch to the robotic arms/legs the steam doesn't need to, preventing heat loss and allowing for the use of flexible tubing that would melt with steam.
When the robotic limb needs to relax, the steam will depressurize into a set of cooling pipes. Although unnecessary, I intend to have peltiers connected to these tubes to generate some power for the robot as well as power cooling fans to quicken the heat dissipation. Then, the water collected can be pumped back into the water tank for re-use.
Hopefully later I can show how I imagine it to look through cad, but for right now I'm going to go work on my robot...
pi'd said...
...but for right now I'm going to go work on my robot...
Robotics sounds like a good place to start.
Just one quick comment: one of the reasons designers will use hydraulics instead of pneumatics has to do with the springiness of the fluids. A liquid is much stiffer than a gas when it's used inside of a cylinder, therefore a liquid, such as hydraulic oil, will give a robot more precision than, say, a pneumatic cylinder. So consider what you will have if a hydraulic actuator is being driven by a gas, such as steam. The steam will still have some springiness to it, so the entire steam-hydraulic system will exhibit some springiness, too. If your robot needs to move with precision, you might find that this springy steam will present some control issues. I'm not saying it's impossible or anything, I'm just giving you a heads-up. Sometimes very clever control systems can overcome the otherwise disastrous limitations of the material world. So getting started on the robotics end of things, now armed with pjv's oscilloscope, sounds like an excellent path.
The springiness is actually beneficial in walking robots because it adds extra balance. If a two legged android starts to tip over, the feet would offer more pressure against it as it started falling. If a multi-legged robot were to set a foot into soft ground, even though it expected the foot to stop moving sooner the pressure will keep pushing down until it hits a hard spot without lifting the robot as it does in a more precise system.
Handling a precise robotic arm may not work quite so well with this system but I'm not going to worry about that, it's not my expertise.
Oh, another benefit: multiple hydraulic rams can be used in places where extra strength is required. Using one of the rams results in twice the speed but half the strength, using both gives the strength without the speed.
I have a story about the springiness of air controls. Years ago my company built a bunch of hopper scales for a catfish plant. These were fed automatically by a conveyor which we could control, and after weighing 30 to 40 pounds of fish we would open a guillotine style door with an air cylinder to empty it. I specified 2 inch diameter air cylinders to open the doors because the fish piled up against the door offer quite a bit of resistance to its opening.
Well the mechanics shop that built them for us unilaterally decided to use 1/2 inch cylinders instead. Admittedly, they were quite a bit cheaper. But what would happen is that when the air valve opened, nothing would happen. More nothing would happen. More nothing would happen. Then, when the air pressure finally became high enough to start the door moving, VROOOOM up it would go like a rocket slamming into the top of the frame. Every. Single. Time. Needless to say, this constant shock loading wasn't a healthy thing for the scale.
When I called the shop on its decision they stood by their guns INSISTING that there was no need for a larger cylinder because the air pressure multiplied by the area was more than sufficient. I had to threaten to cancel the entire sale to get them to grudgingly try a 1 inch cylinder on one of the scales "just to prove I was wrong." Needless to say, it much improved the situation, and before long we were up to 1.5 inch cylinders, which made the problem tolerable.
The problem rapidly gets worse the further the cylinder is from the air valve; air lines can hold a surprisingly large amount of air compared to a cylinder bore, and this air gets compressed too. In the fish scales all the air valves were located at a common panel so some of the air lines were 30 feet long. That kind of thing can make good control with air hardware all but impossible.
Why else would I have thought up an engine that could create pressurized force like I did?
But to better answer the specifics of your post:
Animals such as humans rely on pressure for movement. Just stand on one foot and you'll feel your muscles create pressure to counteract imbalance. In fact, that's how muscles work. Most everyday tasks use slow-twitch muscle to accomplish the tasks at hand, using an estimated amount of muscle strands at first then changing once it decides how much pressure is necessary to lift an object/move something. Each strand is either on or off, but since we have thousands of slow-twitch and fast-twitch muscle strands we can decide where to move our limbs by deciding how much pressure is needed.
The reason the door had problems with slamming open is the same reason why someone opening a stiff door can have it slam open or someone playing tug-a-war can fall backward. The reason why we usually don't have too much trouble everyday, however, is because we have the intelligence to use muscles in the opposite direction if something like a stiff door suddenly swings open. This slows it down and keeps it from hitting the end, unlike your mechanism where all it's able to do is push.
Another thing you mentioned was that control was lost with distance. Hate to mention it, but it's not the air that's your problem, it's your setup. It's obvious that your valve is a long distance from the ram which never was a good idea. Considering electricity travels at the speed of light it doesn't make sense that an electric valve couldn't be added right at the location of the ram. It would be like getting a 30 foot long spring and trying to open the door yourself if you didn't, it just isn't smart.
I don't even know why you brought that up as a valid point anyway, unless you didn't read about my intention to use pneumatic to hydraulic conversion. This is about the only way one can effectively control a pneumatic system with a valve a long distance away, by converting it to something other than pneumatic.
Pi'd....... calm down; you are getting too excited and defensive now!
LocalRoger was just expanding insight to the forum from his personal experience on a related issue. No need to take him to task on that. He is a very clever person. Be happy he is interested enough to read your posts and comment on them.
Thanks for the shout out pjv. I was just aiming to clarify ElectricAye's point with a personal anecdote that cost some people a lot of money. My experience is that you can get fine control with air if you use large bore cylinders and keep the valves close to them, but it's easy to cross a line where you're compressing air against frictional resistance and that quickly causes problems.
I've been using pneumatic controls for 25 years and my experience is that in all real world cylinders friction is pretty considerable. That is going to cause serious problems with using air compression for rebound control. Not to say those problems can't be solved or controlled, but they aren't trivial either.
Sorry about that localroger, I can get a bit carried away. You did get me thinking about the necessity for a good method of stopping the ram, and for that I thank you for my new idea. I'm thinking of having an extra valve that can stop the hydraulic fluid, giving the robot the extra precision most roboticists crave and preserving the springiness necessary for balance.
@wastehl--you're behind the times.
@mctrivia--congrats, you've come up with part of my plan by guessing! In this particular application I'm not really worried about the pressure of which the system operates, I expect that to be low. The primary thing I'm worried about is quantity, which I hope this engine can offer. There is a major problem with it, however, in the fact that it would take a while for the engine to make enough heat once it started to create any work. This means that in a military or a security setting the engine would have to run nonstop. But, if you include a compressor run when the engine is on to pump air into a separate tank, it can be effectively used as a battery of sorts, allowing immediate functionality while the engine is warming up. Then, once the engine takes over with steam, the compressor can be turned on and the air tank can be rejuvenated for the next time it is needed.
Do you plan on posting a schematic of your system? It might help if we could see a diagram - even a hand drawn sketch - of how all your pieces are designed to masterfully interact.
Also, do you have any estimations of what your loads might be? Is this machine going to do only delicate operations or is this thing sized to pick up boulders, crack H-bombs like acorns, and lay waste to the armies of the world?
Finally, I suppose by telling wastehl that he's "behind the times", we are to presume that you now have a solution to your ignition problem, true? Or were you commenting on his personal observation that people have died while working with thermite?
I'll post something hand-drawn later today or tomorrow when I have time, I have to re-think about it since it will be omni-fuel, not thermite.
As for the loads, somewhere in the middle.
He's behind the time's because I've said multiple times I'm thinking of using omni-fuel now, not thermite. This makes more sense anyway because in Alaska where fuel costs are expensive it may be better to burn wood chips or pellets instead of gas. Or during a war when there is plenty of diesel or gasoline it may be better to use that. But, if it's working for the FBI or a large company that needs security in a city it may be better to burn propane for cleaner emissions instead.
my point was not that you should use an air compressor and your complex steam generator. what is wrong with just using an air compressor to charge a tank and when it gets low charge the tank up again. It seems electric batteries will not likely last long wnough for you so make an air compressor that can run off a belt. You then hook up a small gas motor, a generator to charge the batery for your electronics, and the air compressor. If you gear everything right you could have the motor start up when the tank reaches a lower psi limit and turn off at an upper limit. The length of time this would take would be the same to fully charge your batteries. This would probably be a much more efficient system and much lighter.
Air compressors do not have to be loud. nor do gas motors. Look at BMO motorcycle engines. As an alternative you could just use a really hi compression nitrogen system. I built a paint ball gun that used 4500 psi nitrogen tank. A 68cu inch tank would run all day and was supper quiet. If you used a much larger tank you could run all day withot charging.
How stealthy is a robot with a large heavy steam engine going to be?
@mctriv--it doesn't have to be large, and it doesn't have to be heavy. Heck, it probably won't even be noisy. There might even be leeway for attaching different types of furnaces for different tasks necessary. Using a furnace that can take solid fuels like wood chips or coal may be cheaper to run in some areas, but it will also be much larger. Burning liquids will be lighter because they don't require strong tanks for containment and have fewer explosive dangers because it doesn't involve flammable gas under pressure. Gas fuel offers benefit in the fact that it burns cleaner and is simpler to ignite than liquids and doesn't have corrosive nature when spilled.
The furnace really only needs to be like a long cylinder with the fuel ignited on one end and heat absorbing tubing along the exhaust portion. Then it all needs to be surrounded with fireproof insulation and the whole pressurized system covered in bullet proof material such as kevlar and ceramic to prevent a steam explosion if shot at.
Yes, it's very fuzzy, especially the bottom part. Any chance you can scan it? Or try to photograph it in brighter light?
Seems you need something to control the pressure in the combustion chamber so the exhaust doesn't just whoof out the exhaust pipe all the time rather than building up pressure.
Also, how do the hydraulic cylinders retract so their actuators can be repositioned? or is this supposed to be a one-shot deal, like an automobile air-bag?
Well, it is interesting and indeed a thermo-dynamic engine. What are you going to try to do to optimize performance beyond what has been done by others? Are you going to try to hold pressure steady? or are you going to try to hold temperature steady? Heat always goes in one place and out the another, but there are different schemes about using the heat that is passing through. The idea is to use as much of that heat transfer as one possibly can.
So what I am talking about is a choice between the Rankine cycle and the Carnot cycle. Up until now, you have only been addressing the furnace (and maybe a bit of the boiler). There is more to getting a real bench model of an engine in place that just a really hot fuel.
You also need to consider your choice between pistons or a turbine. These days turbines really seem to handle the heavy heavy work. Pistons always require some sort of valves (except two cycle engines) and those valves rob a lot of useful power. Of course, you might be thinking of something in between like a steam driven Wankel engine. I find it exotic to have pistons without a crankshaft connected. It looks as if you envision some sort of a pulse drive. That might work well for pumping a liquid (like supply sea water to Jordan for their soon to be built desalination plant), but most engines take advantage of rotation.
I am over-simplifying. There are more thermo-dynamic cycles. Maybe you hit on a new one. Take a look here.
@Electric--it depends, if you look at the picture again you can see it shows a pressure release valve which goes to the cooling section for recycling. To reset the ram after this any three options can be used:
-Gravity pulls the ram down to reset position
-Spring pulls the ram down
-Opposing ram resets it
@Loopy--Somewhat pressure, but not really. The pumps that let the water into the furnace will be able to keep the pressure at a somewhat stable position but there will still be a lot of fluctuation every time a ram is engaged. To make up for this, the software of the robot/machine will have to accommodate for it depending on the speed of which it wants the ram to move. Since I intend the valves to be servo operated the rate of which the steam enters the ram can be controlled precisely, allowing the valve to be opened more when the pressure is low or vice versa depending on what the computer wants the ram to do.
Side note: I was able to getter a better picture of my drawing. It is attached below.
Every time you add a pump or a controller to make up for some deficiency, you are likely loosing energy that could go into the primary system. If seems to be pumping water around quite a bit. Try to use gravity and siphons.
Thermodynamic engines usually tend to be entirely mechanical for one good reason. There is less inherent waste in the support and control systems. Some do have 'start up' engines attached, but once running they provide all the services to keep running.
You are going to have to externally provide both heat and electricity for this unless you have a mechanical take off to generate electricity for micro-controllers and motion for pumps.
Comments
It's Goddard, Robert Goddard.
K2 -- Needs some rest.
Post Edit -- Screw all these old ladies, pi'd.· Just make sure that if anything goes awry that it's gonna be·strictly your tough ****.
Post Edited (PJ Allen) : 8/5/2010 4:00:15 AM GMT
I'm seeing, get this --·a collapsible Trebuchet on glide-rails (instead of wheels), platform-mounted on the FHR/5HR, or maybe the StingRay, whatever, hurling thermite grenades, by remote control.· That'd be awesome.
Post Edit -- And use the artificial horizon from Harprit's·new book on "Spin" to keep the trebuchet platform level.
And... http://www.pbs.org/wgbh/nova/lostempires/trebuchet/wheels.html
Post Edited (PJ Allen) : 8/5/2010 4:37:26 AM GMT
Go for it!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Stephen
-phar
Coincidentally, I agree. Let me PM you my boss' phone number.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
You have been taking quite a beating here.... much of it undeserved, but to some degree understandably because you have stated some lofty goals using some materials that could be dangerous if not used properly, but mostly, I think, because of insufficient explanation of your plans.
However, I believe you to be an industrious and inquisitive fellow in search of solutions to somewhat wild ideas on a shoe-string budget, and to aid you in your quest I am sending you a used analog style (tube screen, digital memory) older dual channel Tektronix oscilloscope that I no longer have a use for.
I upgrade scopes every couple of years, and it will have a much better remaining life in your hands than on my shelf where it's future will be the trash bin.
I have your co-ordinates from UPEW, so it will ship today.
Learn lots, have fun but above all, in a safe manner.
Cheers,
Peter (pjv)
Good for you. I have been trying to offer some real engineering input here rather than just trash talk. I just felt that experiments with thermite isn't something to inspire over the web. It all started out very vague, as if someone really wasn't trying to build something.
Tektronix product is very nice. I had a rather huge old dual channel with vacuum tubes that I picked up for about $30USD at a Foothill College HAM swap meet. I think it was up to 20Mhz. Rather large, but very useful. But that was long before BasicStamps were available.
If you run into any of those old vacuum tube scopes with plug in front ends, the dual channel one can be cannibalized and makes an extremely nice stereo audio pre-amp. Absolutely flat response from 1Hz through audio and way way beyond. It runs on 12AX7 matched pairs and I bought a dozen sets for about 25 cents a pair at the same time. They actually used silver circuit boards to bring down the resistance.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Ain't gadetry a wonderful thing?
aka G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan
That's very generous of you! An oscilloscope is an excellent tool, helps a person analyze a system, break it down and think it through step by step. I love explosions, and rockets hitting Mach 6 at sea level, had my fair share of near-death experiences and "Oh look, guys, and I've still got all my fingers!" But some of the most exciting experiences I've ever had were watching small traces wiggle across the face of an oscilloscope tube. Thanks to instruments like that, there are times when you feel that you've seen the invisible and accomplished the impossible.
Although thermite is great, I think I'll go for an omni-fuel source of energy instead. The Core where it is burned will be made of cement or metal depending on what I decide is best later on. It will have a valve for liquid and gas fuel intake, and an intake for air. It may also have an auger for solid fuel intake/solid fuel output. There will be an ignitor so the engine will only burn fuel when necessary. Around this core will be metal tubing for water to turn to steam, and there will be two or more of these so the steam can constantly flow even when one of the pipes are reset.
Since the water is recycled, there will be a small water tank for each set of tubes. The valve on the pressure side must close before the valve to intake more water is opened. Once refilled it will go back to the previous position again and a small pump will push the water through as necessary, not requiring much force because of the equalization of the pressure in the tank to that of the line.
All the steam will go to a main set of tubing which stores the pressure until it can be used. This line will be kept near to the core to keep heated and insulated to prevent cooling and pressure loss. When it is used, a valve will be opened and it will blow into a metal cylinder where it will push against a divider between the steam and hydraulic fluid. Since the hydraulic fluid can stretch to the robotic arms/legs the steam doesn't need to, preventing heat loss and allowing for the use of flexible tubing that would melt with steam.
When the robotic limb needs to relax, the steam will depressurize into a set of cooling pipes. Although unnecessary, I intend to have peltiers connected to these tubes to generate some power for the robot as well as power cooling fans to quicken the heat dissipation. Then, the water collected can be pumped back into the water tank for re-use.
Hopefully later I can show how I imagine it to look through cad, but for right now I'm going to go work on my robot...
Robotics sounds like a good place to start.
Just one quick comment: one of the reasons designers will use hydraulics instead of pneumatics has to do with the springiness of the fluids. A liquid is much stiffer than a gas when it's used inside of a cylinder, therefore a liquid, such as hydraulic oil, will give a robot more precision than, say, a pneumatic cylinder. So consider what you will have if a hydraulic actuator is being driven by a gas, such as steam. The steam will still have some springiness to it, so the entire steam-hydraulic system will exhibit some springiness, too. If your robot needs to move with precision, you might find that this springy steam will present some control issues. I'm not saying it's impossible or anything, I'm just giving you a heads-up. Sometimes very clever control systems can overcome the otherwise disastrous limitations of the material world. So getting started on the robotics end of things, now armed with pjv's oscilloscope, sounds like an excellent path.
Handling a precise robotic arm may not work quite so well with this system but I'm not going to worry about that, it's not my expertise.
Oh, another benefit: multiple hydraulic rams can be used in places where extra strength is required. Using one of the rams results in twice the speed but half the strength, using both gives the strength without the speed.
Well the mechanics shop that built them for us unilaterally decided to use 1/2 inch cylinders instead. Admittedly, they were quite a bit cheaper. But what would happen is that when the air valve opened, nothing would happen. More nothing would happen. More nothing would happen. Then, when the air pressure finally became high enough to start the door moving, VROOOOM up it would go like a rocket slamming into the top of the frame. Every. Single. Time. Needless to say, this constant shock loading wasn't a healthy thing for the scale.
When I called the shop on its decision they stood by their guns INSISTING that there was no need for a larger cylinder because the air pressure multiplied by the area was more than sufficient. I had to threaten to cancel the entire sale to get them to grudgingly try a 1 inch cylinder on one of the scales "just to prove I was wrong." Needless to say, it much improved the situation, and before long we were up to 1.5 inch cylinders, which made the problem tolerable.
The problem rapidly gets worse the further the cylinder is from the air valve; air lines can hold a surprisingly large amount of air compared to a cylinder bore, and this air gets compressed too. In the fish scales all the air valves were located at a common panel so some of the air lines were 30 feet long. That kind of thing can make good control with air hardware all but impossible.
Why else would I have thought up an engine that could create pressurized force like I did?
But to better answer the specifics of your post:
Animals such as humans rely on pressure for movement. Just stand on one foot and you'll feel your muscles create pressure to counteract imbalance. In fact, that's how muscles work. Most everyday tasks use slow-twitch muscle to accomplish the tasks at hand, using an estimated amount of muscle strands at first then changing once it decides how much pressure is necessary to lift an object/move something. Each strand is either on or off, but since we have thousands of slow-twitch and fast-twitch muscle strands we can decide where to move our limbs by deciding how much pressure is needed.
The reason the door had problems with slamming open is the same reason why someone opening a stiff door can have it slam open or someone playing tug-a-war can fall backward. The reason why we usually don't have too much trouble everyday, however, is because we have the intelligence to use muscles in the opposite direction if something like a stiff door suddenly swings open. This slows it down and keeps it from hitting the end, unlike your mechanism where all it's able to do is push.
Another thing you mentioned was that control was lost with distance. Hate to mention it, but it's not the air that's your problem, it's your setup. It's obvious that your valve is a long distance from the ram which never was a good idea. Considering electricity travels at the speed of light it doesn't make sense that an electric valve couldn't be added right at the location of the ram. It would be like getting a 30 foot long spring and trying to open the door yourself if you didn't, it just isn't smart.
I don't even know why you brought that up as a valid point anyway, unless you didn't read about my intention to use pneumatic to hydraulic conversion. This is about the only way one can effectively control a pneumatic system with a valve a long distance away, by converting it to something other than pneumatic.
LocalRoger was just expanding insight to the forum from his personal experience on a related issue. No need to take him to task on that. He is a very clever person. Be happy he is interested enough to read your posts and comment on them.
Cheers,
Peter (pjv)
I've been using pneumatic controls for 25 years and my experience is that in all real world cylinders friction is pretty considerable. That is going to cause serious problems with using air compression for rebound control. Not to say those problems can't be solved or controlled, but they aren't trivial either.
@wastehl--you're behind the times.
@mctrivia--congrats, you've come up with part of my plan by guessing! In this particular application I'm not really worried about the pressure of which the system operates, I expect that to be low. The primary thing I'm worried about is quantity, which I hope this engine can offer. There is a major problem with it, however, in the fact that it would take a while for the engine to make enough heat once it started to create any work. This means that in a military or a security setting the engine would have to run nonstop. But, if you include a compressor run when the engine is on to pump air into a separate tank, it can be effectively used as a battery of sorts, allowing immediate functionality while the engine is warming up. Then, once the engine takes over with steam, the compressor can be turned on and the air tank can be rejuvenated for the next time it is needed.
Also, do you have any estimations of what your loads might be? Is this machine going to do only delicate operations or is this thing sized to pick up boulders, crack H-bombs like acorns, and lay waste to the armies of the world?
Finally, I suppose by telling wastehl that he's "behind the times", we are to presume that you now have a solution to your ignition problem, true? Or were you commenting on his personal observation that people have died while working with thermite?
As for the loads, somewhere in the middle.
He's behind the time's because I've said multiple times I'm thinking of using omni-fuel now, not thermite. This makes more sense anyway because in Alaska where fuel costs are expensive it may be better to burn wood chips or pellets instead of gas. Or during a war when there is plenty of diesel or gasoline it may be better to use that. But, if it's working for the FBI or a large company that needs security in a city it may be better to burn propane for cleaner emissions instead.
How stealthy is a robot with a large heavy steam engine going to be?
You mean you haven't heard of India's latest steam-powered stealth trains? They are covered in a special Top Secret radar-absorbing material...
The furnace really only needs to be like a long cylinder with the fuel ignited on one end and heat absorbing tubing along the exhaust portion. Then it all needs to be surrounded with fireproof insulation and the whole pressurized system covered in bullet proof material such as kevlar and ceramic to prevent a steam explosion if shot at.
Yes, it's very fuzzy, especially the bottom part. Any chance you can scan it? Or try to photograph it in brighter light?
Seems you need something to control the pressure in the combustion chamber so the exhaust doesn't just whoof out the exhaust pipe all the time rather than building up pressure.
Also, how do the hydraulic cylinders retract so their actuators can be repositioned? or is this supposed to be a one-shot deal, like an automobile air-bag?
So what I am talking about is a choice between the Rankine cycle and the Carnot cycle. Up until now, you have only been addressing the furnace (and maybe a bit of the boiler). There is more to getting a real bench model of an engine in place that just a really hot fuel.
You also need to consider your choice between pistons or a turbine. These days turbines really seem to handle the heavy heavy work. Pistons always require some sort of valves (except two cycle engines) and those valves rob a lot of useful power. Of course, you might be thinking of something in between like a steam driven Wankel engine. I find it exotic to have pistons without a crankshaft connected. It looks as if you envision some sort of a pulse drive. That might work well for pumping a liquid (like supply sea water to Jordan for their soon to be built desalination plant), but most engines take advantage of rotation.
I am over-simplifying. There are more thermo-dynamic cycles. Maybe you hit on a new one. Take a look here.
http://en.wikipedia.org/wiki/Thermodynamic_cycle
-Gravity pulls the ram down to reset position
-Spring pulls the ram down
-Opposing ram resets it
@Loopy--Somewhat pressure, but not really. The pumps that let the water into the furnace will be able to keep the pressure at a somewhat stable position but there will still be a lot of fluctuation every time a ram is engaged. To make up for this, the software of the robot/machine will have to accommodate for it depending on the speed of which it wants the ram to move. Since I intend the valves to be servo operated the rate of which the steam enters the ram can be controlled precisely, allowing the valve to be opened more when the pressure is low or vice versa depending on what the computer wants the ram to do.
Side note: I was able to getter a better picture of my drawing. It is attached below.
Double check your logic, I think you placed a NOT were you needed an AND.
Thermodynamic engines usually tend to be entirely mechanical for one good reason. There is less inherent waste in the support and control systems. Some do have 'start up' engines attached, but once running they provide all the services to keep running.
You are going to have to externally provide both heat and electricity for this unless you have a mechanical take off to generate electricity for micro-controllers and motion for pumps.