Hey everyone. Third post so I'm very new here.
I'm looking to buy or build a new microcogen that is responsible for a lot of house duties on a large sailboat.
This boat is used for well to do guests who come and vacation on it. My full time job is bringing these people on vacation and I am currently still building our next charter boat (full time).
I was considering a bunch of different propulsion ideas, but outboards won out due to weight and drag considerations. For you boat folks, this is a very fast boat - 20 knots under sail.
Now to the microcogen.
Let me explain, first, what I'm trying to do, then explain how I am thinking I can do it. Please let me know where I'm wrong and where I can do things in a more simple and efficient manner in terms of meeting the needs.
The Needs
*Air Conditioning
*Heat
*DC Power
*Fresh water from salt water (desalinization / reverse osmosis)
*Hot Water
*Quiet System
*Not Looking Like a Junkyard - Must Be Elegant
The Plan (needs your expertise!)
*3 Cylinder Kubota Diesel with sea water heat exchangers for cooling and for cooling the mainifold (off the shelf item) - nearly all accessories mentioned below should be run from belts off the flywheel side to get full rated power out of a very small engine.
*Twin 3 ton Sanden compressors to run air conditioning or maybe a reverse cycle heat pump - should be able to kick in a control to run at a moderately high RPM when compressors are on, but slow down a bit when they are off to save fuel.
*1/2" chiller and heater lines to run to 6 different zones on the boat
*Local fans to control amount of heating or cooling in each zone
*Huge alternator to provide DC amps out, run at the flywheel for efficiency - when running, should be able to kick in a control that varies the RPM based on what kind of draw the inverter needs... just like the control on a Honda EU2000. Would be nice if it auto-started based on battery charge state.
*Belt driven high pressure water pump for watermaker (reverse osmosis) system
*Coolant heat exchanger to make hot water via standard marine hot water heater (they have a coolant loop for heating)
****Possibly use the exhaust heat to heat the boat, but not so sure about that. Probably have reverse cycle heating with the air conditioning compressors... need input here.
I know, it's one complicated beast, but all of these systems are required for the boat. They are all available off the shelf as individual AC powered items, but the total weight of the items, plus the total weight of a large generator to power them would be less than ideal.
The objects in this design are both weight savings and fuel efficiency.
Well, what do you all think?
Any input from this brief introduction?
My weak points are:
1) Setting up a reverse cycle heat pump - I can set up marine refrigeration and air conditioning, but have never made a reverse cycle system
2) Connecting all of these to the flywheel output - do they make a huge pulley set I could attach to the flywheel and have all of these pumps laid out everywhere running from belts?
3) Controls - I'd really like the Honda EU2000 "Eco throttle" type control when making power and then also would like to have the engine run efficiently as the air conditioning compressors kick in and out. A regular governor type speed control would be best running the watermaker pump. Lots of controls, but I do have some experience... just very rusty. I made controls for a NASA spacecraft in the 1990's.
Any advice?
Are there any threads I need to look at on here you'd recommend?
Thank you very much in advance. This thread will be long and we can all participate in the design if you like that kind of stuff.
I think I would start out by first figuring out (and minimizing where possible) my total electrical loads (AC and DC power) and mechanical loads (AC, RO, etc)...and you might want to pad this number by X% so as to have some design margin. That will determine what size alternator and engine you will need. I find that all too many people start acquiring engines/alternators without first doing this most basic of pre-planning.
Then you can think about how best to extract the resulting heat available and relative to what's required for hot water and general heating. As you say, this has all been done already, many different ways, and is commercially available. So your effort is more about sizing what you need, developing an overall generic integrated design solution that accomplishes the mission, and then selecting all the specific off-the-shelf components required to complete the mission within your budget. And keep in mind that the marine environment is very harsh on electrical/mechanical equipment and there is good reason why marine equipment is pricely. Sometimes going cheap on critical marine equipment can be false economy...especially if this is bluewater mission with lee shores...
If you don't have a copy already, you might want to get Nigel Calder's "Boatowner's Mechanical & Electrical Manual".
Bob B.
Build an ass kicking DC electrical system and invert as needed.
Electric outboards?
I went on Black Beards SCUBA cruise (that's how I sold it to her). We knew it was time to get up when they turned the air conditioner off to cook breakfast. "Twice the fun - Half the money".
Casey
I made controls for a NASA spacecraft in the 1990's.
Welcome aboard Sully. Awesome! Did you make the outside doorbell for the International Space Station? ;)
The US allegedly spent a million bucks developing a pen that would work in zero G. The Russians solved the problem with a lead pencil. In similar spirit of saving money the outside doorbell on the MiR was an old brass cowbell and a cast iron striker with a stainless steel cable so the unshielded rays of the sun wouldn't rot the cord. Didn't matter that sound waves won't travel in a vacuum although the cosmonauts might have heard it through the station's bulkhead by conduction. If you buy any of this we need inventive people like you! :D
Quote from: LowGear on February 22, 2012, 06:41:31 PM
Build an ass kicking DC electrical system and invert as needed.
Electric outboards?
I went on Black Beards SCUBA cruise (that's how I sold it to her). We knew it was time to get up when they turned the air conditioner off to cook breakfast. "Twice the fun - Half the money".
Casey
Casey, this is a real possibility, if I can find some appropriate, submersible electric motors. In that case, I wouldn't have to invent a micro cogen setup at all. This is probably the most simple, but the propulsion of the boat, of course, has to be rock solid. I'd have to find some 15-20KW AC motors and generators (probably putting out 3 phase) to run them. They also have to be thin (like a submersible pump) so as not to get in the way of the props they would be turning.
I am looking into this option right now, which might save me countless hours of putting together a reverse cycle heating and cooling system. Then, I could buy one off the shelf, using the DC gen to power and invert as you were saying.
Yes, Bob. It is all about sizing and finding off the shelf parts, but I am not entirely sure where to do so. Where do you find the type of things that I was mentioning?
*Multiple crankshaft pulleys for taking power off the flywheel side?
*Controls for engine/throttle?
*Components for a hydronic reverse cycle heater?
Do you guys have any particular places you buy things at that you like?
I do have a handle on my electrical loads though...
I am trying not to sound too cocky (unsuccessfully), but I could write that Nigel Calder book. It's for people just starting out with boats. I've owned an ocean going sailboat for more than 20 years now and have actually owned about half a dozen. I've done ABYC compliant upgrades to all and do all my own work. I also live full time on these charter boats and I'm 100% responsible for all maintenance work. I'm a 100T Master with STCW-95, sailing endorsement, etc... etc... Nigel Calder is for beginners. I've already analyzed my power consumption needs as the first step. This is a very advanced topic for boaters, which is why I stopped in to visit you folks. A lot of people on boating forums just have no experience with anything but buying complete systems off the shelf.
I am building a very advanced boat right now - 20 knots under sail - using vacuum resin infusion techniques, etc... I need to keep as much weight off the boat as I can to keep the performance. Performance is part of what I'm selling to the charter guests.
Anyway, I will explore making some electric outboards. They don't make any large enough for this boat off the shelf. I would normally need twin 30HP marine diesels for it.
Thanks for the input, guys. I'll be back... when I'm finished taking a second look at the outboard vs electric outboard issues. Previously, I found that the weight of the generators, plus electric motors was too heavy as compared to either just diesels or just gasoline powered outboards. I will revisit that again and post back.
Here is a 30HP electric outboard
http://www.gizmag.com/30hp-aquawatt-most-powerful-electric-outboard-motor-in-the-world/18511/
(http://www.microcogen.info/index.php?action=dlattach;topic=709.0;attach=4095;image)
http://www.microcogen.info/index.php?topic=709.0 (http://www.microcogen.info/index.php?topic=709.0)
Think DC power plus Bats, now think Multi volts plus bats.
4-8 kw DC power, house loads.
10-18 Kw prop loads
How much Heat?
How much cooling, refer/freeze not in included?
A/C think rolling piston variable speed DC.
Propulsion Drive think DC.... all the gear doesn't have to be under water
L
Quote from: Sully on February 23, 2012, 06:04:10 PM
Quote from: LowGear on February 22, 2012, 06:41:31 PM
Build an ass kicking DC electrical system and invert as needed.
Electric outboards?
I went on Black Beards SCUBA cruise (that's how I sold it to her). We knew it was time to get up when they turned the air conditioner off to cook breakfast. "Twice the fun - Half the money".
Casey
Casey, this is a real possibility, if I can find some appropriate, submersible electric motors. In that case, I wouldn't have to invent a micro cogen setup at all. This is probably the most simple, but the propulsion of the boat, of course, has to be rock solid. I'd have to find some 15-20KW AC motors and generators (probably putting out 3 phase) to run them. They also have to be thin (like a submersible pump) so as not to get in the way of the props they would be turning.
I am looking into this option right now, which might save me countless hours of putting together a reverse cycle heating and cooling system. Then, I could buy one off the shelf, using the DC gen to power and invert as you were saying.
Yes, Bob. It is all about sizing and finding off the shelf parts, but I am not entirely sure where to do so. Where do you find the type of things that I was mentioning?
*Multiple crankshaft pulleys for taking power off the flywheel side?
*Controls for engine/throttle?
*Components for a hydronic reverse cycle heater?
Do you guys have any particular places you buy things at that you like?
I do have a handle on my electrical loads though...
I am trying not to sound too cocky (unsuccessfully), but I could write that Nigel Calder book. It's for people just starting out with boats. I've owned an ocean going sailboat for more than 20 years now and have actually owned about half a dozen. I've done ABYC compliant upgrades to all and do all my own work. I also live full time on these charter boats and I'm 100% responsible for all maintenance work. I'm a 100T Master with STCW-95, sailing endorsement, etc... etc... Nigel Calder is for beginners. I've already analyzed my power consumption needs as the first step. This is a very advanced topic for boaters, which is why I stopped in to visit you folks. A lot of people on boating forums just have no experience with anything but buying complete systems off the shelf.
I am building a very advanced boat right now - 20 knots under sail - using vacuum resin infusion techniques, etc... I need to keep as much weight off the boat as I can to keep the performance. Performance is part of what I'm selling to the charter guests.
Anyway, I will explore making some electric outboards. They don't make any large enough for this boat off the shelf. I would normally need twin 30HP marine diesels for it.
Thanks for the input, guys. I'll be back... when I'm finished taking a second look at the outboard vs electric outboard issues. Previously, I found that the weight of the generators, plus electric motors was too heavy as compared to either just diesels or just gasoline powered outboards. I will revisit that again and post back.
Wow I think I just got battery cable envy ;D :P
Quote from: squarebob on February 23, 2012, 08:33:24 PM
Here is a 30HP electric outboard
http://www.gizmag.com/30hp-aquawatt-most-powerful-electric-outboard-motor-in-the-world/18511/
Aside from being incredibly overpriced and not available for sale in the USA, there is a little boating detail that must be understood in order to talk outboards...
There are basically two kinds of boats: Planing boats and displacement boats. There are more, but we'll keep it simple.
Planing boats are what the vast majority of outboards are made for. These outboards have a small diameter prop that spins very fast in the water and is optimized for high speed while the boat is above the water. 90%+ outboards are made for this type of boat. The Aquawatt is also made for this type of boat.
All sailing vessels are what is called a displacement boat. This means the boat's hull does not plane on top of the water. It stays sunk down in the water, just like it would at rest, even when going full speed. These types of boats require large diameter props that turn at a slower rate, which gives way more torque and low end power. It is necessary to use that kind of prop on a displacement boat. The Aquawatt does not work on a displacement boat. Outboards like the Honda "Power Thrust" and Yamaha "High Thrust" and Mercury "Bigfoot" are the types you can run on a displacement boat. They have geared down lower units that turn the prop more slowly and have larger diameter props.
For that reason, there are no suitable electric outboards in existence. I would have to build it.
OH MY GOD LLOYD! :o :o
Thank you! That's exactly the type of thing I was envisioning. Let me take a good read through that entire thread and I will post back here to answer your questions. Beautiful!
Quote from: Lloyd on February 23, 2012, 08:47:05 PM
(http://www.microcogen.info/index.php?action=dlattach;topic=709.0;attach=4095;image)
http://www.microcogen.info/index.php?topic=709.0 (http://www.microcogen.info/index.php?topic=709.0)
Think DC power plus Bats, now think Multi volts plus bats.
4-8 kw DC power, house loads.
10-18 Kw prop loads
How much Heat?
How much cooling, refer/freeze not in included?
A/C think rolling piston variable speed DC.
Propulsion Drive think DC.... all the gear doesn't have to be under water
L
Quote from: Sully on February 23, 2012, 06:04:10 PM
Quote from: LowGear on February 22, 2012, 06:41:31 PM
Build an ass kicking DC electrical system and invert as needed.
Electric outboards?
I went on Black Beards SCUBA cruise (that's how I sold it to her). We knew it was time to get up when they turned the air conditioner off to cook breakfast. "Twice the fun - Half the money".
Casey
Casey, this is a real possibility, if I can find some appropriate, submersible electric motors. In that case, I wouldn't have to invent a micro cogen setup at all. This is probably the most simple, but the propulsion of the boat, of course, has to be rock solid. I'd have to find some 15-20KW AC motors and generators (probably putting out 3 phase) to run them. They also have to be thin (like a submersible pump) so as not to get in the way of the props they would be turning.
I am looking into this option right now, which might save me countless hours of putting together a reverse cycle heating and cooling system. Then, I could buy one off the shelf, using the DC gen to power and invert as you were saying.
Yes, Bob. It is all about sizing and finding off the shelf parts, but I am not entirely sure where to do so. Where do you find the type of things that I was mentioning?
*Multiple crankshaft pulleys for taking power off the flywheel side?
*Controls for engine/throttle?
*Components for a hydronic reverse cycle heater?
Do you guys have any particular places you buy things at that you like?
I do have a handle on my electrical loads though...
I am trying not to sound too cocky (unsuccessfully), but I could write that Nigel Calder book. It's for people just starting out with boats. I've owned an ocean going sailboat for more than 20 years now and have actually owned about half a dozen. I've done ABYC compliant upgrades to all and do all my own work. I also live full time on these charter boats and I'm 100% responsible for all maintenance work. I'm a 100T Master with STCW-95, sailing endorsement, etc... etc... Nigel Calder is for beginners. I've already analyzed my power consumption needs as the first step. This is a very advanced topic for boaters, which is why I stopped in to visit you folks. A lot of people on boating forums just have no experience with anything but buying complete systems off the shelf.
I am building a very advanced boat right now - 20 knots under sail - using vacuum resin infusion techniques, etc... I need to keep as much weight off the boat as I can to keep the performance. Performance is part of what I'm selling to the charter guests.
Anyway, I will explore making some electric outboards. They don't make any large enough for this boat off the shelf. I would normally need twin 30HP marine diesels for it.
Thanks for the input, guys. I'll be back... when I'm finished taking a second look at the outboard vs electric outboard issues. Previously, I found that the weight of the generators, plus electric motors was too heavy as compared to either just diesels or just gasoline powered outboards. I will revisit that again and post back.
Quote from: Lloyd on February 23, 2012, 08:47:05 PM
http://www.microcogen.info/index.php?topic=709.0 (http://www.microcogen.info/index.php?topic=709.0)
Think DC power plus Bats, now think Multi volts plus bats.
4-8 kw DC power, house loads.
10-18 Kw prop loads
How much Heat?
How much cooling, refer/freeze not in included?
A/C think rolling piston variable speed DC.
Propulsion Drive think DC.... all the gear doesn't have to be under water
L
Hi Lloyd. I am happy to find someone who has done something similar to what I'm looking to do.
I am still not convinced about the diesel electric propulsion at this point and my go with outboards. I have to do a weight analysis on that choice. Even the guys on the electric boat forum suggested that my usage pattern would be better suited to outboards, if I wanted to props clear of the water when sailing. So, I'll take the DC power for propulsion out of the mix for now.
Heat: 36,000 BTU
Air conditioning: 3-4 ton. Have had mixed estimates. My estimate was 4 ton. Other people say 3 ton.
Refrigerator and Freezer: I prefer these run from solar, since I do not want to chew through batteries, cycling them to run those loads. I also prefer not to do daily generator runs to support refrigerators and freezers. I prefer those run automatically, so I'm not a captive slave to my boat. I can leave for a week and still come back to well frozen items when that runs from solar. Have owned boats with both setups. Much prefer the automatic, always on, no maintenance solar refrigeration.
A/C: When you say "rolling piston", do you mean a scroll compressor? I think that's what you are saying. They make those belt driven as well, but it's a lot easier to buy that stuff off the shelf, I guess.
The whole microcogen idea was to use the diesel engine to run the huge loads that solar can't handle. Solar can handle a microwave, a hairdryer, refrigeration and freezers, etc... What solar can almost handle, but not quite, is air conditioning and heat. I had envisioned that the small diesel could be kicked in for HVAC purposes, then figured I'd add the high pressure pump for the watermaker and a high output alternator for an extra battery boost if I get behind on solar.
That is the main idea behind the microcogen... as a supplement to the solar system that runs all electric. Just kicked in for extremely huge, long time period loads and for odds and ends like watermakers.
My thought is to make it one big system. When you're not on the boat the only loads will be refrigeration and the solar will handle that.
Still at it here.
Boats can be fairly complex, since one decision affects the next and I have to minimize weight above all else.
Looking more closely at this microcogen, I am thinking of just making it into a big DC power source and running everything through inverters. That way, solar can do some work and the micro diesel can do some work.
Is it possible to buy or make a throttle assembly for the diesel that allows it to up the RPMs in response to a load coming online, like a Honda EU2000 generator does? Does anyone know about these types of control systems?
Ok, I asked a pretty hard question about the throttle control.
Here is a more simple question:
Does anyone know where to find good deals on used diesels - especially 10-14HP marinized diesels?
Craig's list in the SF bay area frequently has diesel generators pulled from sail boats.
Concerning the throttle control, I haven't seen one yet that acts like the honda's eco mode. I plan on building on into my system that I posted about. Measure the current going to the inverter, and choose a throttle position. I plan on using an Arduino micro controller to do the job. It has built in PWM output, so I can use a simple solenoid, and get variable positions. Add a rpm pickup, and you have feedback, but the feedback isn't required.
Now to get the time to build it, and program the controller.
Another option is to use a PWM chip (part numbers are at work), to control the solenoid. The chip I've looked at will output from 10% to 90%, and is controlled with a voltage. Use a current to voltage converter circuit, feed the voltage into the chip, and let the chip power the solenoid. More current gives more throttle. Set the gain, add some filtering, and its an analog control circuit.
Yet another option is to get a DC linear actuator. Measure the current with a shunt. Use that voltage, and compare it to a voltage produced by a potentiometer connected to the linear actuator (position sensor), and use a simple comparitor. Feed the comparitor output to the motor drive/relay. If the current sensing voltage is higher than the position voltage, the motor turns on, and adds throttle. If its lower, it reverses it. Make sure you have a dead band in the middle to prevent hunting, and it should work.
Hopefully someone can pipe in with something similar thats off the shelf already.
Michael
Edit: take a look at the Woodward 828 Digital Control. Analog inputs, so you could use a current sensing transformer with a resistor as an input. Probably expensive, but they're made for marine use.
Artificer,
Most available solenoids don't react linearly to variable input. They are unpredictable in other than end positions. Linear actuators/motors and solenoids are different animals. You would also need some type of interface driver (such as FET) between your PWM device and any coil driven "work" device to handle the current demands of that device.
Terry
I think Arificer's on the right track with his preferred approach. With an Arduino or Pic or Picaxe you could cope fairly easily with the extreme non-linearity of the solenoid, and also the non-linearity of the throttle. By using a table driven compensation, you can just take a WAG at the initial values, then "tune" it experimentally with your debugger software.
As Arificer suggests, this could be done in analog circuitry, too, but with more development time and circuitry. Creating non-linear curves (multiple linear approximations, actually) can be done readily with diodes and zener diodes in an op amp amplifier feedback loop. With a wireless breadboard wired into the running setup and a handful of zeiners of different values and some trim pots for setting the gain of each zeiner's feedback, you COULD do it. (You'd want to opto-isolate the Mosfet drive circuit.) This is a valid approach for someone very handy with op amps for linear circuits and a strong disinclination to software.
It was enjoyable for me to read your the gamut of ways to "skin this cat", Artificer. Bravo.
Best Wishes,
Bruce
If I'm not mistaken most of the Woodward solenoids are capable of position control, not just on/off. Here's a video of a listeroid controlled by a Woodward electronic governor. (http://www.youtube.com/watch?v=K7Qmw_AtPdo) Sully could use a similar solenoid and DIY circuit, or if the budget allowed, just use the production/off the shelf controller. The controller has speed feedback, so the closed loop control takes care of all of the unpredicatbility.
One way to get around the problems of PWM and unpredictability is to use several solenoids in full stop mode to get several run speeds. None energized is low rpm. Energize another and its high idle. Another gets you mid-range, and another gets full speed. You can use off the shelf components like current sensing relays to control the setup. Use as many solenoids as you want set points. The solenoids will be cheaper, since you only have two positions, so that should counter the cost of needing more. I'm not sure if this is better than just going with a heavy duty servo control. Do they make marine duty servos that are affordable? I'd be a bit hesitant to use hobby servos on a commercial vessel. At least with the DIY circuitry, you could pot the unit to keep the nasty environment out.
The chip I mentioned (I'll look it up when I get to work) can directly drive up to 2.5 amps. I have no clue how much the Woodward solenoids draw, so not sure if they are adequate.
Thinking about it this morning, I'm not sure how appropriate a solenoid control system would be. If it was part of the Woodward system, and its designed in, thats one thing. But the engines will already have governors, so you don't need high speed control. You just want to change the rpm setting based on the current draw. Slower is better in a way, since you'll moderate the speed changes due to transients.
I'm interested in this topic because its central to the power unit I'm designing. For me, since I'll be using the Arduino controller, PWM to the solenoid only requires a driver and the solenoid. If the solenoid ends up being too expensive, I'll go with a large RC servo. The Arduino has a library of servo functions, and can drive them directly. I guess its time to research hobby priced servos, and see if they can handle hundreds of hours of use, if not thousands.
Michael
Nice setup with the Woodward Governor. Thanks for that link, Micheal. I'm interested in your take on the servos out there.
I'm interested in homebrew electronic governors as I've long thought about getting rid of my barely adequate (Listeroid) stock governor and replacing it with a servo and my own electronics with rpm sensing from the existing flywheel spoke sensor. This would facilitate a 80% propane mixing scheme by second servo as well.
There are serious safety issues that have to be addressed for my scheme. My pneumatic rack closer actuator could overpower even a jammed servo, and of course there's the pneumatic valve lifter if even that failed. (I already have microcontroller monitoring of rpm and auto shut down if out of range.) I would use a solenoid on the propane line to failsafe that servo metering.
For Sully's situation, a salt water marine environment adds another whole layer of design concerns that I'm largely clueless about.
Here you go off the shelf Linear Actuators and PWM Controllers. http://www.precisiongovernors.com/applications/index.cfm?application=13&type=actuator (http://www.precisiongovernors.com/applications/index.cfm?application=13&type=actuator) I poste about these in my Perky/cat\Volvo thread.
quote:SZ Linear Actuators
The model SZ linear actuator is designed for direct mounting on the engine in place of the fuel shutoff solenoid. This integral type actuator is linkage free and provides precise speed control. The Linear Ball-Bearing design ensures smooth rapid operation of the actuator providing a stable operating speed of the engine when combined with one of PG's controllers. This combined with low operating currents of less than 1.5 amps result in an actuator with consistent performance over a long operating life. PG's linear actuators are designed to respond in milliseconds to changes in the current from a pulse-width modulated signal generated by a PG controller. A magnetic pick-up signal transmitted to the controller provides for closed loop speed control. The actuator and controller maintain engine speed adjusting the fuel requested to obtain preset engine speed settings. This eliminates the droop inherent to mechanical governors.
Lloyd
BruceM: I'm not knowlegable enough with servos to give any advice. About the only think I know is to make sure it has enough torque for the job, and feed it a proper pulse width for position control. They have some really cool RC items out there. Since they're for toys, the prices aren't bad. Under $100 for a servo with 12lbs of pull? Not bad. I'm interested in the Arduino system because of the shields/daughter boards they have. Since its a hobby level controller, its cheap.
Arduin board $30
Servo $50
Proximity sensor for RPM $20 (automationdirect.com)
One safety item you might want to look at is the anti-shudder intake valve on VW TDI's. Block off the egr opening (or use it for propane injection), and find a non-vacuum method to actuate it. On the TDI's, if the key is off, the butterfly is closed. No air, no running, and the seal looks fairly tight. Kinda expensive new, but you could probably find one used. (why do I keep sounding like a cheap SOB? :))
Lloyd: SWEET! Thats exactly the type of unit I was thinking about. Made for the job, quick acting, and with the controller its an easy solution. I've been trying to read the entire forum... but its taking awhile. Apparently I haven't gotten to you thread yet. Thanks
Michael
Nice, very high quality linear pulse actuators, Llyod. Just what Sully needs for his marine application.
My Listeroid IP rack requires very little force to move if the governor linkage is removed- less than a pound. That's why I was thinking "disposable" RC servos. (Replace every ?1000 hrs?) I think a decent servo with ball bearings on the output shaft is under $30. at TowerHobbies.com. The current requirements for the pulsed actuators, plus the EMI, is too much for my application.
BruceM,
I don't have any problem with the circuitry involved, in fact am very well versed on it, but a solenoid is not a servo. A slug of iron in a coil is not variable with any repeatable results. Servos, linear motors, motors with gear train, etc will respond like he describes, but not many plain old solenoids. A typical solenoid takes x current to move from one position to the other (end to end), but can remain there with a 1/10 of that amount of current, with quite a load against it.
Otherwise his description of simple servo control is text book.
The Woodward ACTUATOR in the video is NOT a simple solenoid. (it appears to be a Dyna 2000 or 2500)
Seperating apples from oranges, thats all,
Terry
Thanks for sorting that out, Terry. I've seen pulsed solenoids used in a few linear applications but didn't realize there were special designs for doing so and I've never used one.
How are the solenoids designed for pulsed linear use different than the typical coil and slug? Dual air coils???
+1 Thanks, Terry
In my mind I was thinking of the higher end solenoids, not the type you find on the washing machine door. I think that if you use a return spring of significant force (1/4 of total pull?), you can get in the ball park with just applying a PWM signal. If all you want is idle/solenoid off, fast idle, faster, and wide open, then it not a terribly precise requirement. Getting a unit designed for the purpose, however, is the right way to go.
Michael
I did a little research online and while it is possible to use a conventional solenoid as a linear actuator moving against a spring, the PWM frequencies must be very low to avoid inductive heating. One would have to experiment to insure acceptable heat levels. Position will not be linear with respect to PWM duty cycle, as the magnetic force increases as the slug becomes fully enveloped in the coil. Other issues for a dynamic/linear use of a solenoid would be wear/durability, since constant movement was not part of the original design requirements. Many of the PWM/linear solenoids have linear bearings and such to address that issue.
Older designs of solenoid valves designed for PWM use are often limited to a 30Hz maximum PWM frequency. The modern "linear" designs (used in some newer electronic controlled transmissions) are compatible with high frequency (300KHz) drives, with much smaller inductances.
On throttle control, I am looking to reuse an automobile 'Cruise Control' throttle unit in my DC generator control project. Small DC actuator connected to a pull cable (needs external return spring) and built in limit switches. Plus they have done some level of 'weather protection'. Got mine from a junk yard for under $20.
Will still need to close the loop by monitoring RPMs and deciding needed RPM vs. load being placed on the motor, but for the actual throttle control I have high hopes for these auto throttle cruise control units.
-al-
If you read US Patent 7209020 it explains in detail how the latest "Variable force solenoids" work. The ones that adjust the hydraulic pressure in your transmission or the phase angle of your camshaft if you have that kind of engine. They have eliminated the need for position feedback, but at the same time still have to use a certain strategy when operating the solenoid to get repeatable results because of the hysteresis of the materials in the magnetic circuit.
For a boat, which has to function as a self sufficient "island" (especially with paying guests) one needs reliable solutions, not disposable parts... Generally, getting access to work on things is hardly a comfortable job. Logistics can be very troubling indeed and make the actual cost of a part seem like a secondary consideration. Ideally, one would try to minimize reliance on belts of any kind, lest you find yourself changing it during a force 10 gale... The other thing that comes to mind is redundancy. The recent misery on the cruise ship is a reminder why one does not want single points of failure.
If you need custom 3 phase PM motors, you should look at the "kit motors" sold by Parker http://divapps.parker.com/divapps/emn/pdf/Frameless_Motor_Brochure.pdf (http://divapps.parker.com/divapps/emn/pdf/Frameless_Motor_Brochure.pdf) The power to weight/size ratio of these motors is superb. Yes, you need to put them in your own housing and supply a bushing and shaft, but most of that is straight forward lathe work. Putting the rotor into the stator needs a fixture since the magnetic forces involved are very high. But besides that hassle, these are very competent motors with good speed potential or high torque in the bigger diameters and one can "stack" these cores on a single shaft to multiply torque if needed.
Quote from: Westcliffe01 on February 27, 2013, 07:04:33 PM
If you read US Patent 7209020 it explains in detail how the latest "Variable force solenoids" work. The ones that adjust the hydraulic pressure in your transmission or the phase angle of your camshaft if you have that kind of engine. They have eliminated the need for position feedback, but at the same time still have to use a certain strategy when operating the solenoid to get repeatable results because of the hysteresis of the materials in the magnetic circuit.
For a boat, which has to function as a self sufficient "island" (especially with paying guests) one needs reliable solutions, not disposable parts... Generally, getting access to work on things is hardly a comfortable job. Logistics can be very troubling indeed and make the actual cost of a part seem like a secondary consideration. Ideally, one would try to minimize reliance on belts of any kind, lest you find yourself changing it during a force 10 gale... The other thing that comes to mind is redundancy. The recent misery on the cruise ship is a reminder why one does not want single points of failure.
If you need custom 3 phase PM motors, you should look at the "kit motors" sold by Parker http://divapps.parker.com/divapps/emn/pdf/Frameless_Motor_Brochure.pdf (http://divapps.parker.com/divapps/emn/pdf/Frameless_Motor_Brochure.pdf) The power to weight/size ratio of these motors is superb. Yes, you need to put them in your own housing and supply a bushing and shaft, but most of that is straight forward lathe work. Putting the rotor into the stator needs a fixture since the magnetic forces involved are very high. But besides that hassle, these are very competent motors with good speed potential or high torque in the bigger diameters and one can "stack" these cores on a single shaft to multiply torque if needed.
Look at Precision Governors, the link I posted are the same . They have a retrofit, or a specific fit.
All of them can be retrofitted with a little tool and die.. Much easier then building housings. Plus they are cheep considering they're off the shelf
Lloyd