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Power Transister or Relays??
I finally located a stronger 12 volt linear drive unit for the tiller pilot
on my 13 ton Ingrid 38. It has all the power and length of stroke that I feel I need (when the going gets tough). This unit has a 14" stroke (stop to stop) 1000# dynamic, 1500# static and overload clutch rated at 1200-1600# w/auto thermal overload. However; the drive motors max current draw is 14 amps.. Now that sounds like a lot but under normal operating conditions it shouldn't take more than 5-6 amps and then only in pulses since the tiller load is normally fairly light. (from my observations of the AP performance recently, the duty cycle is about 1sec on/15sec off. ) Under heavy conditions, I'm sure this will be different and I have not data since the tiller load is too great for the OEM linear drive. I will be using this AP set up mostly while motoring so power consumption will not be a primary factor. I will still be using the very reliable AH3000 tiller pilot control head but since this unit is limit to only a couple amps output to the old linear drive, I need to build a power controller circuit (not sure that the right term), to deliver the full 14 amps to the new linear drive motor. Both the old and the new linear drive was controlled by the switching of polarity to the drive motor. I would use this same output from the control head to switch the output polarity of the power controller.. First I would like to know which would be the most effiecent and reliable, Transistors or Relays in this controller.?? I realize I could build it from regular, off the shelf automotive relays and if they fail, I can just plug in a spare, but then if I mount my transistors in sockets, I could do the same thing. BTW. Either controller will be protected, below deck in a sealed box. Can anyone offer a curcuit diagram for either transistor or the rely power controller. I'm not an elex. whiz but I can build just about anything that you guyz can sketch up for me. Or a good reference that might have such a circuit. Thanks, Steve s/v Good Intentions |
Power Transister or Relays??
Steve,
I would use neither. MOSFETs would be my choice. Check out International Rectifier's website. Doug "Steve" wrote in message ... I finally located a stronger 12 volt linear drive unit for the tiller pilot on my 13 ton Ingrid 38. It has all the power and length of stroke that I feel I need (when the going gets tough). This unit has a 14" stroke (stop to stop) 1000# dynamic, 1500# static and overload clutch rated at 1200-1600# w/auto thermal overload. However; the drive motors max current draw is 14 amps.. Now that sounds like a lot but under normal operating conditions it shouldn't take more than 5-6 amps and then only in pulses since the tiller load is normally fairly light. (from my observations of the AP performance recently, the duty cycle is about 1sec on/15sec off. ) Under heavy conditions, I'm sure this will be different and I have not data since the tiller load is too great for the OEM linear drive. I will be using this AP set up mostly while motoring so power consumption will not be a primary factor. I will still be using the very reliable AH3000 tiller pilot control head but since this unit is limit to only a couple amps output to the old linear drive, I need to build a power controller circuit (not sure that the right term), to deliver the full 14 amps to the new linear drive motor. Both the old and the new linear drive was controlled by the switching of polarity to the drive motor. I would use this same output from the control head to switch the output polarity of the power controller.. First I would like to know which would be the most effiecent and reliable, Transistors or Relays in this controller.?? I realize I could build it from regular, off the shelf automotive relays and if they fail, I can just plug in a spare, but then if I mount my transistors in sockets, I could do the same thing. BTW. Either controller will be protected, below deck in a sealed box. Can anyone offer a curcuit diagram for either transistor or the rely power controller. I'm not an elex. whiz but I can build just about anything that you guyz can sketch up for me. Or a good reference that might have such a circuit. Thanks, Steve s/v Good Intentions |
Power Transister or Relays??
Steve
I can't help you with how to do it, but I feel your solution has to be electronic, not relays. You are talking about switching up to 14 amps DC perhaps 4 times per minute - that's about 40,000 cycles in a week of continuous use. That's a number of duty cycles that would have one looking carefully at specifications if it were an AC load. I don't think automotive components will cut the mustard. No-one expects to start their car 10 times per day, 365 days per year for 10 years! So the solution has to be solid state; question is how you get it designed and then prove it's reliability ..... Hope this helps. David "Doug Dotson" wrote in message ... Steve, I would use neither. MOSFETs would be my choice. Check out International Rectifier's website. Doug "Steve" wrote in message ... I finally located a stronger 12 volt linear drive unit for the tiller pilot on my 13 ton Ingrid 38. It has all the power and length of stroke that I feel I need (when the going gets tough). This unit has a 14" stroke (stop to stop) 1000# dynamic, 1500# static and overload clutch rated at 1200-1600# w/auto thermal overload. However; the drive motors max current draw is 14 amps.. Now that sounds like a lot but under normal operating conditions it shouldn't take more than 5-6 amps and then only in pulses since the tiller load is normally fairly light. (from my observations of the AP performance recently, the duty cycle is about 1sec on/15sec off. ) Under heavy conditions, I'm sure this will be different and I have not data since the tiller load is too great for the OEM linear drive. I will be using this AP set up mostly while motoring so power consumption will not be a primary factor. I will still be using the very reliable AH3000 tiller pilot control head but since this unit is limit to only a couple amps output to the old linear drive, I need to build a power controller circuit (not sure that the right term), to deliver the full 14 amps to the new linear drive motor. Both the old and the new linear drive was controlled by the switching of polarity to the drive motor. I would use this same output from the control head to switch the output polarity of the power controller.. First I would like to know which would be the most effiecent and reliable, Transistors or Relays in this controller.?? I realize I could build it from regular, off the shelf automotive relays and if they fail, I can just plug in a spare, but then if I mount my transistors in sockets, I could do the same thing. BTW. Either controller will be protected, below deck in a sealed box. Can anyone offer a curcuit diagram for either transistor or the rely power controller. I'm not an elex. whiz but I can build just about anything that you guyz can sketch up for me. Or a good reference that might have such a circuit. Thanks, Steve s/v Good Intentions |
Power Transister or Relays??
Larry W4CSC wrote:
Larry W4CSC US Supports Apartheid! Vetoes UN resolution condemning Apartheid Wall. http://www.antiwar.com/hacohen/h052103.html http://www.theage.com.au/articles/20...917478560.html Can apartheid at home be far away?.... Apartheid NOW! Wall off Mississippi! Well, Larry, I see you are still cloaking your hatred of Jews behind support for the so-called Palestinians. Nothing much changes for you except your meds, eh? How sad. -- __________________________________________________ __________ Email sent to will never reach me. |
Power Transister or Relays??
Hmm....from the sound of an Autohelm, I was under the impression the
motor drive was a STEPPER motor, which varies with the number of steps/second delivered from a digital drive. Listen to it run. It doesn't cut on and off at all. Take it out into the waves and listen to the FREQUENCY fed to the motor change from that low RPM, intermittent bzzt,bzzt,bzzt that drives me crazy as it makes little course corrections in calm waters, constantly, those little jerky motions, to the full blown hardovers trying to keep up with the swells offshore. It's not just turning on and off like your water pump. As to the drive on a hydraulic ram, I believe it is driven from analog electronics controlling motor speed, therefore hydraulic pressure. We just installed a B&G Network Pilot with electro-hydraulic A unit on Lionheart, an Amel Sharki 41 ketch. It looks like a perfect human is piloting the helm...scary. If you go under the aft cabin bunk and watch it work, you can hear the power to the drive motor vary as it runs this way, stops, runs that way backwards. It doesn't come "on and off" like a relay. To make small course corrections, it comes on at a low level and power is applied gradually until the rudder position sensor tells the electronics the rudder is, in fact, moving slowly in the desired direction. At that point the motor stays at that level of power until it approaches the correct course, then it slows to a stop and reverses, bringing the helm, very gently, back to center as the correction becomes reality. It's the smoothest operating autopilot I've ever seen, and very quiet unless you're sleeping on top of its motor. If someone orders a 10 degree turn on the Pilot's controller, the motor comes on hard to pull the helm over, but not to the stops. B&G Pilot's manual says the computer "learns" the boat's handling characteristics, constantly, and figures out how hard it needs to pull over to make a nice, coordinated turn. As soon as the boat responds, felt by B&G's fluxgate, the motor reverses very gently and pulls the helm back to center....arriving uncannily AT center just as the new course shows up on the display. Sure wish I could steer it by hand as accurately as that...never oversteering, which is real easy to do on the Amel's big rudder...(c; I don't think any autopilot's control is an on-off simple switch....Autohelm or hydraulic. Watch carefully when it's working. It doesn't turn at a set speed on either. Larry W4CSC US Supports Apartheid! Vetoes UN resolution condemning Apartheid Wall. http://www.antiwar.com/hacohen/h052103.html http://www.theage.com.au/articles/20...917478560.html Can apartheid at home be far away?.... Apartheid NOW! Wall off Mississippi! |
Power Transister or Relays??
I've had both the AH4000 wheel and this AH3000 tiller pilot apart and there
is no digital drive. Just a simple little 'weenie' motor and a set of plastic reduction drive gears. (BTW the more recent, to 2000, Autohelm/Ratheon APs still continued to use the same drive motors as the old British Nautic and AH units. I can put a meter on the motor leads from the control head and note the switch of polarity from port to stbd. The high freq. you maybe refering to could be from a pulse control to the motor but from the circuit diagram of the control head, I can't see this as 'digital'. You can download and look at the ciruit diagram on my web site.. http://hood.hctc.com/~esteve/private/manuals/ The document name is AHcontrol head CCT1.doc Steve s/v Good Intentions |
Power Transister or Relays??
Steve,
Assuming there is no ambiguity about the AP circuit. If you just need a relay you can buy a solid state one already designed and packaged with surge and arc circuitry built in. Google for electronic suppliers, they shouldn't be hard to find. Regards , Ron |
Power Transister or Relays??
Massive SNIP
The controller circuit: Here is a site I ran across. It is a run-down on FET H-Bridges for FD/REV control of a DC motor. It presents a simple circuit, no special FET driver chips. The down side is that you have to build (included in article) a small device to provide 24v to operate the FETS. Haven't tried it, but looks reasonable. Link below.... http://www.armory.com/~rstevew/Publi...Blanchard/nch- brdg.htm Woody |
Power Transister or Relays??
Beware of link. It got a NewLine added... Append to use. _W_
___________________________________________ In article t, says... Massive SNIP The controller circuit: Here is a site I ran across. It is a run-down on FET H-Bridges for FD/REV control of a DC motor. It presents a simple circuit, no special FET driver chips. The down side is that you have to build (included in article) a small device to provide 24v to operate the FETS. Haven't tried it, but looks reasonable. Link below.... http://www.armory.com/~rstevew/Publi...Blanchard/nch- brdg.htm Woody |
Power Transister or Relays??
"Steve" wrote in message ... I finally located a stronger 12 volt linear drive unit for the tiller pilot on my 13 ton Ingrid 38. It has all the power and length of stroke that I feel I need (when the going gets tough). What make of linear drive did you go for then? garry |
Power Transister or Relays??
The linear drive I finally located (haven't purchased yet) is non-marine.
Rather commercial, industrial for gates, wheel chair lifts and positioning appliactions. I is presently available from Surplus Center http://www.surpluscenter.com/item.as...&item= 5-1474 I'm anticipating that I will have to give some attention to marinizing the unit, but that's what DIYs do. Steve s/v Good Intentions |
Power Transister or Relays??
"Steve" wrote in message ... The linear drive I finally located (haven't purchased yet) is non-marine. Rather commercial, industrial for gates, wheel chair lifts and positioning appliactions. I is presently available from Surplus Center http://www.surpluscenter.com/item.as...&item= 5-1474 I'm anticipating that I will have to give some attention to marinizing the unit, but that's what DIYs do. The other thing you may need is some sort of a clutch to decouple it whenever the autopilot is not in use. I know that the raymarine use a sort of a magnetic affair that energises and locks (by friction) two plates together whenever the autopilot is switched on. God knows how you will build that into it!! garry |
Power Transister or Relays??
The tiller pilots are engaged by simply lifting the end of the linear drive
piston off the tiller pin. With my OEM linear drive, when not engaged on the tiller pin, it swings out of the way to a storage clip on the stern rail. BTW. The AH or ST wheel pilot, have internal belt drives with idler rollers on a clutch lever. Not magnetic (couldn't/shouldn't have mag. around the cockpit) or friction clutches in these. Trust me, I've had one apart for voyage repairs in my last boat. Steve s/v Good Intentions |
Power Transister or Relays??
"Steve" wrote in message ... The tiller pilots are engaged by simply lifting the end of the linear drive piston off the tiller pin. With my OEM linear drive, when not engaged on the tiller pin, it swings out of the way to a storage clip on the stern rail. O.K I understand, I was thinking that you were going to use it below deck directly attached to the quadrant. In that situation you would need some sort of a clutch. The marinising aspect might take a lot of work, that is usually the bit where the manufactured models fall down, hence the desire to mount them below decks if possible BTW. The AH or ST wheel pilot, have internal belt drives with idler rollers on a clutch lever. Not magnetic (couldn't/shouldn't have mag. around the cockpit) or friction clutches in these. Trust me, I've had one apart for voyage repairs in my last boat. Yeah, I know, have had to strip down those friction clutches myself, a real PITA. The one on the ST4000 is attached via two tiny roll pins that have a tendency to shear off at awkward moments. Re the magnetic clutch, I have seen them on the linear drive of the ST7000 ST6000 and havent noticed any problem with them affecting the compass. But then I suppose it is fairly minimal, compared to the magnetism created within the actuator motor itself. good luck garry |
Power Transister or Relays??
Regarding marinizing: if the cylinder ram plain steel, I will replace it
with stainless. (I have a machine shop) Pack and seal the gear case. And epoxy coat the exterior. Have to wait and see how well it's built.. If I don't like what I see, I'll return it before I modify it. Steve s/v Good Intentions |
Power Transister or Relays??
Keep us posted on how you get on....
That ram sure is a lot cheaper that equivalent marine models garry "Steve" wrote in message ... Regarding marinizing: if the cylinder ram plain steel, I will replace it with stainless. (I have a machine shop) Pack and seal the gear case. And epoxy coat the exterior. Have to wait and see how well it's built.. If I don't like what I see, I'll return it before I modify it. Steve s/v Good Intentions |
Power Transister or Relays??
VERY bad idea. That drive is not going to be any where near fast enough
for an autopilot. It is a screw drive. A LOT slower than a hydraulic. Also a hydraulic cylinder needs to be a "balanced" type with the rod going all the way through so the displacement is the same in both directions. Regular single ended double action cylinders have less displacement on the rod side because of the volume of the rod. With a constant pump speed it retracts faster than it extends and with less force. You would never get an autopilot logic unit to control it properly. These are more what you will need: http://www.surpluscenter.com/sort.as...ke yword=HCP1 and the pump has to be reversable like these: http://www.surpluscenter.com/sort.as...ke yword=HPSD Steve wrote: The linear drive I finally located (haven't purchased yet) is non-marine. Rather commercial, industrial for gates, wheel chair lifts and positioning appliactions. I is presently available from Surplus Center http://www.surpluscenter.com/item.as...&item= 5-1474 I'm anticipating that I will have to give some attention to marinizing the unit, but that's what DIYs do. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
I had considered hydraulic and if I already had hydraulic on the engine, I
probably would reconsider it. Originally I had planned on hydraulic for the anchor windlass but found the Lewmar 1000 vertical and I'm now happy with that. Also any hydraulic cylinder and hoses would be right in the cockpit since my rudder is 'outboard' and no provision for an inboard cylinder. Additionally, I would have to find or build some kinda electrical to hydraulic control valve for the AP control head to operate. After reading Glenns comments regarding the operating speed of the screw drive, I went to the boat and did a test to determine the rate of travel of the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load. The unit I'm considering is 3/4 inch per min.. 25% slower, however since the this unit has 3 times the thrust I could move the tiller attachment pin aft an appropriate amount to increase the rudder stop to stop travel time and still have the advantage of the increased dynamic and static load. I'm going to contact the fellows at Surplus Center and see if I can get some more spec. info on this unit. They have been very help full in the past. I am however taking Glenns warnings into consideration and thanks for the heads up. Steve s/v Good Intentions |
Power Transister or Relays??
WOW! I am amazed that the AH3000 is that slow. How long does it take
to go hard over to hard over? I was thinking that 15 or 20 seconds would be the bare minumum. 1" per minute on a 6" tiller arm would take more than 3 minutes. Steve wrote: I had considered hydraulic and if I already had hydraulic on the engine, I probably would reconsider it. Originally I had planned on hydraulic for the anchor windlass but found the Lewmar 1000 vertical and I'm now happy with that. Also any hydraulic cylinder and hoses would be right in the cockpit since my rudder is 'outboard' and no provision for an inboard cylinder. Additionally, I would have to find or build some kinda electrical to hydraulic control valve for the AP control head to operate. After reading Glenns comments regarding the operating speed of the screw drive, I went to the boat and did a test to determine the rate of travel of the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load. The unit I'm considering is 3/4 inch per min.. 25% slower, however since the this unit has 3 times the thrust I could move the tiller attachment pin aft an appropriate amount to increase the rudder stop to stop travel time and still have the advantage of the increased dynamic and static load. I'm going to contact the fellows at Surplus Center and see if I can get some more spec. info on this unit. They have been very help full in the past. I am however taking Glenns warnings into consideration and thanks for the heads up. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
Wow, my WH moves the rudder from stop to stop in about
3 or 4 seconds! Doug "Glenn Ashmore" wrote in message news:8_llb.85875$sp2.29546@lakeread04... WOW! I am amazed that the AH3000 is that slow. How long does it take to go hard over to hard over? I was thinking that 15 or 20 seconds would be the bare minumum. 1" per minute on a 6" tiller arm would take more than 3 minutes. Steve wrote: I had considered hydraulic and if I already had hydraulic on the engine, I probably would reconsider it. Originally I had planned on hydraulic for the anchor windlass but found the Lewmar 1000 vertical and I'm now happy with that. Also any hydraulic cylinder and hoses would be right in the cockpit since my rudder is 'outboard' and no provision for an inboard cylinder. Additionally, I would have to find or build some kinda electrical to hydraulic control valve for the AP control head to operate. After reading Glenns comments regarding the operating speed of the screw drive, I went to the boat and did a test to determine the rate of travel of the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load. The unit I'm considering is 3/4 inch per min.. 25% slower, however since the this unit has 3 times the thrust I could move the tiller attachment pin aft an appropriate amount to increase the rudder stop to stop travel time and still have the advantage of the increased dynamic and static load. I'm going to contact the fellows at Surplus Center and see if I can get some more spec. info on this unit. They have been very help full in the past. I am however taking Glenns warnings into consideration and thanks for the heads up. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
Correction::
That was suppose to be 1"/sec. for the AH3000 linear drive. The ram (if you wanna call it that) total travel is 10.5 inches and it take a little over 10 sec from stop to stop. Sorry about the error. Steve s/v Good Intentions |
Power Transister or Relays??
I think you misunderstand the typical hydraulic auto-pilot for
mid-size boats where the manual steering is not hydraulic. They typically have a dedicated reversible hydraulic pump driving (as Glenn points out) a balanced cylinder. The AP electronics turns the electric motor driving the pump on and off in the required direction. Larger vessels, including Fintry, have a setup like the one you describe below, where an hydraulic pump runs continuously with hydraulic servos (fluid operated relays) supplying the fluid to the ram(s) as required. This is similar to automotive power steering. I think I'd rather have an hydraulic cylinder and hoses back there rather than an electrically driven screw about the same size. The hoses would be bigger than the wires, but the Surplus Center drive is not designed for your environment. Finally, think harder about the broader design issues here. In particular, what happens when a big wave pushes the rudder harder than the AP can push back? This is the touchy area for screw drive APs, as the drive has to stall safely, and then go on pushing as soon as it's able. An hydraulic unit does this easily, but a direct electric drive has problems -- electric motors don't like to stop and you can't just un-clutch the thing, as it has to stop, not backdrive. Also think about duty cycle and design life. An AP is working all the time, back and forth. Very few applications require this kind of activity, so it may be an area where adapting something from elsewhere is difficult. As a complete aside, I wonder about the need for a balanced cylinder in a hydraulic drive. As Glenn says, with an ordinary single ended cylinder, you have different thrust in the two directions. But, modern autopilots are pretty sophisticated and adjusting for that in software might be cheaper than the extra cost and maintenance (two seals rather than one) of a balanced cylinder. Jim Woodward www.mvFintry.com "Steve" wrote in message ... I had considered hydraulic and if I already had hydraulic on the engine, I probably would reconsider it. Originally I had planned on hydraulic for the anchor windlass but found the Lewmar 1000 vertical and I'm now happy with that. Also any hydraulic cylinder and hoses would be right in the cockpit since my rudder is 'outboard' and no provision for an inboard cylinder. Additionally, I would have to find or build some kinda electrical to hydraulic control valve for the AP control head to operate. After reading Glenns comments regarding the operating speed of the screw drive, I went to the boat and did a test to determine the rate of travel of the OEM (AH3000) linear drive. It is exactly 1 inch per min. with no load. The unit I'm considering is 3/4 inch per min.. 25% slower, however since the this unit has 3 times the thrust I could move the tiller attachment pin aft an appropriate amount to increase the rudder stop to stop travel time and still have the advantage of the increased dynamic and static load. I'm going to contact the fellows at Surplus Center and see if I can get some more spec. info on this unit. They have been very help full in the past. I am however taking Glenns warnings into consideration and thanks for the heads up. Steve s/v Good Intentions |
Power Transister or Relays??
In article k9elb.83730$sp2.44153@lakeread04,
Glenn Ashmore wrote: Regular single ended double action cylinders have less displacement on the rod side because of the volume of the rod. With a constant pump speed it retracts faster than it extends and with less force. You would never get an autopilot logic unit to control it properly. The above is NOT a correct statement considering that most AutoPilots use an Electonic Feedback Loop for Rudder Position. This is accomplished by having a Rudder Position Encoder mounted to the Rudder System that then feeds back to the Pilot Logic directly. In this type of system, the travel time of the Piston isn't even considered, unless the Hydrolic Pump that feeds the system is so underrated that the movement of the piston is slower than the Pulsewidth Modulation of the Feedback Loop. All the AutoPilot OEM's I am familiar with take this into account when designing the Feedback Loop in the first place, and therefor it is a NONISSUE for the end user. Bruce in alaska -- add a 2 before @ |
Power Transister or Relays??
I think you misunderstand the typical hydraulic auto-pilot for mid-size boats where the manual steering is not hydraulic. They typically have a dedicated reversible hydraulic pump driving (as Glenn points out) a balanced cylinder. The AP electronics turns the electric motor driving the pump on and off in the required direction. I was kinda thinking the same thing. Infact, at first, I thought this unit was a electro-hydraulic unit. Since I'm not going to drive the hydraulics off the engine I really need to find a compact efficient 12vdc power unit. I don't think I need to get into a continious running pump since the boat has a full keel and maintains it's course very well. 90% of the time, the AP linear drive is just holding the tiller in position (static load). Something that a hydrualic cylinder it very good at. The main reason the AH3000 linear isn't satisfactory, is because in heavy weather, the rudder tiller exerts enough force against the linear drive to force the motor to turn in reverse. I'm afraid of what this is doing to the planetary gear reduction. Thanks to your comments and that of Glenn, I will look farther for a 12vdc (reversiable) PowerPack.. If anyone knows of something like this, please let me know.. The pumps that Glenn referenced were just the pumps.. gotta be a complete unit someplace, like truck power lifts, etc. Steve s/v Good Intentions |
Power Transister or Relays??
Steve,
You might contact WH. The power pack I have is a simple 1/4 HP DC motor the drive a hydraulic pump via a belt. Pretty compact. I suspect they would sell you a unit for a reasonable price. Motor only runs when moving the runner. But that is a function of the controller rather than the powerpack itself. Doug s/v Callista "Steve" wrote in message ... I think you misunderstand the typical hydraulic auto-pilot for mid-size boats where the manual steering is not hydraulic. They typically have a dedicated reversible hydraulic pump driving (as Glenn points out) a balanced cylinder. The AP electronics turns the electric motor driving the pump on and off in the required direction. I was kinda thinking the same thing. Infact, at first, I thought this unit was a electro-hydraulic unit. Since I'm not going to drive the hydraulics off the engine I really need to find a compact efficient 12vdc power unit. I don't think I need to get into a continious running pump since the boat has a full keel and maintains it's course very well. 90% of the time, the AP linear drive is just holding the tiller in position (static load). Something that a hydrualic cylinder it very good at. The main reason the AH3000 linear isn't satisfactory, is because in heavy weather, the rudder tiller exerts enough force against the linear drive to force the motor to turn in reverse. I'm afraid of what this is doing to the planetary gear reduction. Thanks to your comments and that of Glenn, I will look farther for a 12vdc (reversiable) PowerPack.. If anyone knows of something like this, please let me know.. The pumps that Glenn referenced were just the pumps.. gotta be a complete unit someplace, like truck power lifts, etc. Steve s/v Good Intentions |
Power Transister or Relays??
That's why the quality APs have a rudder position sensor. Good control
cannot be acheived without one. DOug s/v Callista "Bruce in Alaska" wrote in message ... In article k9elb.83730$sp2.44153@lakeread04, Glenn Ashmore wrote: Regular single ended double action cylinders have less displacement on the rod side because of the volume of the rod. With a constant pump speed it retracts faster than it extends and with less force. You would never get an autopilot logic unit to control it properly. The above is NOT a correct statement considering that most AutoPilots use an Electonic Feedback Loop for Rudder Position. This is accomplished by having a Rudder Position Encoder mounted to the Rudder System that then feeds back to the Pilot Logic directly. In this type of system, the travel time of the Piston isn't even considered, unless the Hydrolic Pump that feeds the system is so underrated that the movement of the piston is slower than the Pulsewidth Modulation of the Feedback Loop. All the AutoPilot OEM's I am familiar with take this into account when designing the Feedback Loop in the first place, and therefor it is a NONISSUE for the end user. Bruce in alaska -- add a 2 before @ |
Power Transister or Relays??
The 12VDC powerpacks like Barnes and Fenner are not designed for
reversing. Will Hamm's system is simple and and an elegant use of off the shelf parts. It looks like a fairly standard 2" bore steering cylinder mounted at one end on a custom made swivel. The power unit is a very small pump with a belt drive to what looks like a 1/4 HP DC permanent magnet motor. The motor would have to be compatable with the control unit but that means either a PM (2 wire) split field (3 wire) or series wound (4 wire). The thing is you have to balance the tiller arm length to the throw of the cylinder to get 72º of movement then match the displacement of the cylinder with the capacity of the power unit to get an acceptable hard over time with suficient force. Then you do it backwards using available parts to get the final tiller arm length. The thing is any compromise reduces efficiency so components made for the purpose usually work out better. Here are some handy formulas. I did the calculations for Rutu and it took 3 pages of scribbling and then decided to let a pro do it. :-) Maximum pressure on the rudder = 1.6 x area of the rudder in sq. ft. x boat speed in knots squared. If the hull is capable of surfing double it. Torque = max pressure X distance from the cneter of force of the rudder to the centerline of the rudder post. (The center of force on the rudder is usually about 30 to 40% of the cord length. ) Cylinder force required = Torque/tiller arm length Hydraulic pressure required (psi) = req'd force/net area of piston in sq. in. Net area is the area of the cylinder less the area of the rod. Hydraulic volume required (GPM) = net area of piston x throw length/231 Output of pump (GPM) = displacement x RPM/231 Horsepower required = GPM x PSI/1714 x .80 (efficiency of pump) (multiply by 4 for a 15 second hard over time) Steve wrote: I think you misunderstand the typical hydraulic auto-pilot for mid-size boats where the manual steering is not hydraulic. They typically have a dedicated reversible hydraulic pump driving (as Glenn points out) a balanced cylinder. The AP electronics turns the electric motor driving the pump on and off in the required direction. I was kinda thinking the same thing. Infact, at first, I thought this unit was a electro-hydraulic unit. Since I'm not going to drive the hydraulics off the engine I really need to find a compact efficient 12vdc power unit. I don't think I need to get into a continious running pump since the boat has a full keel and maintains it's course very well. 90% of the time, the AP linear drive is just holding the tiller in position (static load). Something that a hydrualic cylinder it very good at. The main reason the AH3000 linear isn't satisfactory, is because in heavy weather, the rudder tiller exerts enough force against the linear drive to force the motor to turn in reverse. I'm afraid of what this is doing to the planetary gear reduction. Thanks to your comments and that of Glenn, I will look farther for a 12vdc (reversiable) PowerPack.. If anyone knows of something like this, please let me know.. The pumps that Glenn referenced were just the pumps.. gotta be a complete unit someplace, like truck power lifts, etc. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
That is fine if you are designing from scratch and can program the
controller for PWM to run the motor faster in one direction than the other but for a home brew match up it would be close to impossible. Bruce in Alaska wrote: In article k9elb.83730$sp2.44153@lakeread04, Glenn Ashmore wrote: Regular single ended double action cylinders have less displacement on the rod side because of the volume of the rod. With a constant pump speed it retracts faster than it extends and with less force. You would never get an autopilot logic unit to control it properly. The above is NOT a correct statement considering that most AutoPilots use an Electonic Feedback Loop for Rudder Position. This is accomplished by having a Rudder Position Encoder mounted to the Rudder System that then feeds back to the Pilot Logic directly. In this type of system, the travel time of the Piston isn't even considered, unless the Hydrolic Pump that feeds the system is so underrated that the movement of the piston is slower than the Pulsewidth Modulation of the Feedback Loop. All the AutoPilot OEM's I am familiar with take this into account when designing the Feedback Loop in the first place, and therefor it is a NONISSUE for the end user. Bruce in alaska -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
Thanks for the formulas Glenn.
I ran the numbers to get some idea of what I might be looking for. Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm. Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor to achieve the 15 sec. hard over time. Seems do-able on paper. I just don't know what the max current draw might be for this motor. I'm sure someone has a formula for this as well. Steve s/v Good Intentions |
Power Transister or Relays?? (correction)
Sorry, another typo..
"Steve" wrote in message ... Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm. Should read .... 2"X20"X 1 1/8" cylinder, ....... Steve s/v Good Intentions |
Power Transister or Relays?? (correction)
Your power requirement is pretty close to what I got for Rutu. Now you
will find that there are so many alternatives that your brain will start fogging over. You have a starting point but the cylinder is going to be pretty big and heavy and the tiller arm will have to be 18 to 19" long. You have plenty of room to work with the pressure. With 700 lb. on a 12" throw you can get by with a much smaller rod diameter. Look for a 1.5" to 2" cylinder with a 5/8 to 3/4" rod and 12 to 14" of throw. It will be a lot lighter and you can use a shorter tiller. The displacement will be less and the pressure will go up about the same so the required HP will be about the same. Also, small 12VDC motors develop HP with RPM more than torque and the lower you gear it the less efficient it gets. Try to stay under 3:1. For example a 2x12x.625 cylinder will take about 34 cu. in. for a full throw or about 136 CI/minute for a 15 second hard over. Now say we choose a 3600 RPM PM motor (Surplus Center #10-1779 would be close but a little over powered) and start with a belt ratio of 2:1 so the pump is running 1800 RPM. 136/1800 is .075 so we need a pump with about that displacement. The Surplus Center #9-5567 is a little small so the belt ratio would have to be more like 1.8:1 Admitedly that is not an ideal setup but it will be very hard to get the perfect match with surplus parts. The thing is, when you add up the cost of all the parts including the mounts, fittings, hoses etc, you will come out spending $500-600 and many hours of thinking and labor and still not be quite sure that it will work the way you want. That makes the $1,200 price of a complete professionally designed unit seem a lot more attractive. You would have to be a compulsive DIYer like me to rationalize it. :-) OTOH, if you go through the exercise of designing one you have a lot better understanding of how they work and know more about how to select the correct one for your boat. Steve wrote: Sorry, another typo.. "Steve" wrote in message ... Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm. Should read .... 2"X20"X 1 1/8" cylinder, ....... Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
Steve,
15 second hard over time seems slow to me. May not be able to track well in a seaway. Doug s/v Callista "Steve" wrote in message ... Thanks for the formulas Glenn. I ran the numbers to get some idea of what I might be looking for. Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm. Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor to achieve the 15 sec. hard over time. Seems do-able on paper. I just don't know what the max current draw might be for this motor. I'm sure someone has a formula for this as well. Steve s/v Good Intentions |
Power Transister or Relays??
15 seconds is a bit slow for a fin keel but you are spoiled. ;-) Will
likes the WH to run under 10 seconds with full load and usually closer to 6 seconds. Doug Dotson wrote: Steve, 15 second hard over time seems slow to me. May not be able to track well in a seaway. Doug s/v Callista "Steve" wrote in message ... Thanks for the formulas Glenn. I ran the numbers to get some idea of what I might be looking for. Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm. Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor to achieve the 15 sec. hard over time. Seems do-able on paper. I just don't know what the max current draw might be for this motor. I'm sure someone has a formula for this as well. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays?? (correction)
Thanks again Glenn.. Makes sense, however (as always), as you can see in
this picture http://hood.hctc.com/~esteve/launch15.jpg the rudder pintle line extends up and behind the head of the rudder. So this would require a tiller arm of at least 20" and even that is awkward due to the rudder angle of 37.5 degrees. The cylinder could be rail mounted and reach over the tiller head but that wouldn't be very elegant. Looking at this problem and the picture, I am thinking of a cylinder mount on the boomkin and a tiller arm lower down and perpendicular to the rudder. I could resolve this by installing the tiller arm though the stern post into the lazarette, but I really hate to give up all that storage. And then there is the engage/disengage problem and sealing up the opening for the tiller arm Just about anything that is behind the stern rail would require a method to remotely engage, disengage from the helm position. Strange how a serious cruiser would call it a problem while DIYer will see this as a mental challenge. The (mental) wheels are turning. I'll start a new topic in Rec.boats.cruising when I get some ideas. Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller design. Haven't actually found anything here that I could get my head around. Thanks again. Steve s/v Good Intentions |
Power Transister or Relays??
Doug,
Several metions of WH and I thought I saw it referred to as 'something' Harris but I'm not familiar with WH. I assume he designs and provides hydraulic packages. Need a little help here.. Steve s/v Good Intentions |
Power Transister or Relays?? (correction)
oh,oh,oh, I forgot you have an outboard rudder. 15 seconds is probably
a pretty good rate. That ol' girl should keep her head pretty well with no help and probably will not want to turn any faster than that anyway. Don't ask me about the control box. The electronic side of my brain overheated on that remote control light switch and blew out completely after figuring out the automatic flush/backwash circuit for the watermaker. :-) Steve wrote: Thanks again Glenn.. Makes sense, however (as always), as you can see in this picture http://hood.hctc.com/~esteve/launch15.jpg the rudder pintle line extends up and behind the head of the rudder. So this would require a tiller arm of at least 20" and even that is awkward due to the rudder angle of 37.5 degrees. The cylinder could be rail mounted and reach over the tiller head but that wouldn't be very elegant. Looking at this problem and the picture, I am thinking of a cylinder mount on the boomkin and a tiller arm lower down and perpendicular to the rudder. I could resolve this by installing the tiller arm though the stern post into the lazarette, but I really hate to give up all that storage. And then there is the engage/disengage problem and sealing up the opening for the tiller arm Just about anything that is behind the stern rail would require a method to remotely engage, disengage from the helm position. Strange how a serious cruiser would call it a problem while DIYer will see this as a mental challenge. The (mental) wheels are turning. I'll start a new topic in Rec.boats.cruising when I get some ideas. Oh Yah! before we abandon this Elex topic, I still need a 12vdc controller design. Haven't actually found anything here that I could get my head around. Thanks again. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
WH autopilots. Will Ham makes an un-sexy, but elegant and bulletproof
autopilot system in a little shop out on Banbridge Island. Extremely popular with serious cruisers and small commercial boats. The Dashews love them if that means anything. It does not have some of the "smart" and "learning" features of some fancier brands but you can set just about everything for the best performance. I think in a PS owner survey it was the only brand that reported no failures and had the lowest failure rate in the SSCA survey. Steve wrote: Doug, Several metions of WH and I thought I saw it referred to as 'something' Harris but I'm not familiar with WH. I assume he designs and provides hydraulic packages. Need a little help here.. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
In article XDElb.87781$sp2.47416@lakeread04,
Glenn Ashmore wrote: That is fine if you are designing from scratch and can program the controller for PWM to run the motor faster in one direction than the other but for a home brew match up it would be close to impossible. Bruce in Alaska wrote: In article k9elb.83730$sp2.44153@lakeread04, Glenn Ashmore wrote: Regular single ended double action cylinders have less displacement on the rod side because of the volume of the rod. With a constant pump speed it retracts faster than it extends and with less force. You would never get an autopilot logic unit to control it properly. The above is NOT a correct statement considering that most AutoPilots use an Electonic Feedback Loop for Rudder Position. This is accomplished by having a Rudder Position Encoder mounted to the Rudder System that then feeds back to the Pilot Logic directly. In this type of system, the travel time of the Piston isn't even considered, unless the Hydrolic Pump that feeds the system is so underrated that the movement of the piston is slower than the Pulsewidth Modulation of the Feedback Loop. All the AutoPilot OEM's I am familiar with take this into account when designing the Feedback Loop in the first place, and therefor it is a NONISSUE for the end user. Bruce in alaska You missed the point entirely with the above. The PWM for the rudder position is set in the controller design and does not care what mechanism is moving the rudder, andlong as it has postive control over that mechanism. (ie move right, oir move left) The rest is already designed into the controller feedback loop, and a nonissue for the user. It could be an issue if you were designing an AP controller from scratch, but that is not the case in this thread. Bruce in alaska -- add a 2 before @ |
Power Transister or Relays??
You can find them at www.whautopilots.com. One of the things
I really liked about it is the fact that the major controls come out as knobs. Gain, Yaw, and Counter Rudder can be easily adjusted. In all sorts of conditions I have rarely adjusted anything except the Gain, and then not by much. Doug s/v Callista "Glenn Ashmore" wrote in message news:YZUlb.90635$sp2.28254@lakeread04... WH autopilots. Will Ham makes an un-sexy, but elegant and bulletproof autopilot system in a little shop out on Banbridge Island. Extremely popular with serious cruisers and small commercial boats. The Dashews love them if that means anything. It does not have some of the "smart" and "learning" features of some fancier brands but you can set just about everything for the best performance. I think in a PS owner survey it was the only brand that reported no failures and had the lowest failure rate in the SSCA survey. Steve wrote: Doug, Several metions of WH and I thought I saw it referred to as 'something' Harris but I'm not familiar with WH. I assume he designs and provides hydraulic packages. Need a little help here.. Steve s/v Good Intentions -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
Power Transister or Relays??
How big is Good Intentions, Steve? 1/4 horse is bigger than the
autopilot pump on Swee****er (Swan 57, actual weight about 60,000 pounds in round-the-world trim). I don't remember how strong it was, but both physical size and power consumption suggest around 1/10hp. As an extremely rough check on the sensibility of your numbers from Glenn's formulas, the motor driving Fintry's hydraulic steering was a 2hp 220VDC. She was designed to be bulletproof -- Lloyds 100A1 Maltese, for navigation on the North Sea -- so I suspect that half that would have done fine. Since rudder area varies as displacement to the 2/3 power and speeds are probably similar (under 10 knots), 1/4 horse should be good up to around 1/4 of Fintry's displacement, say 37 tons. 1/4 horse is 186 watts, so a perfect motor would draw 15 amps at 12VDC. Your results will vary with reality, maybe double -- small DC motors aren't very efficient. Jim Woodward www.mvFintry.com "Steve" wrote in message ... Thanks for the formulas Glenn. I ran the numbers to get some idea of what I might be looking for. Seems I should be using about a 2"X20"X1.5" cylinder, 318psi @ .186gpm. Using a slightly oversize pump at a lower RPM, I would need a 1/4hp motor to achieve the 15 sec. hard over time. Seems do-able on paper. I just don't know what the max current draw might be for this motor. I'm sure someone has a formula for this as well. Steve s/v Good Intentions |
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