Re: [RCSE] line tension
At 01:18 PM 12/23/2007, you wrote: So Chuck, Tell us how the tension limiter worked and how well it worked. What were the good points and problems? Could such a scheme be used effectively today? The Jam/Feb 1977 issue of Sailplane contained an article by Chet Tuthill describing the winch system developed by Jim Robinson and other members of the Coffee Airfoilers model airplane club. The tension limiter was a major part of that article. The tension limiter was a separate base for the standard winch. For normal flying, the winch was removed from the base and used like any other winch. The base for the winch had a pivot just ahead of the CG of the winch and battery and had a microswitch at the rear of the platform. The tension limiter switch was wired in series with the foot peddle. A spring held the platform against the switch until line tension caused the platform to rock forward opening the tension limiter switch. When line tension decreased, the spring forced the platform aft closing the switch. The inertia of the winch and battery gave a very smooth pulsing when launching larger models if the contestant held the foot peddle down and let the winch do the pulsing. The tension limiter proved to be very reliable and we used if for many years. As usual, there ain't no free lunch. The tension limiter winch took a few minutes longer to set up but the considerable reduction in broken lines made it worth while. The tension limiter was set by attaching a 25 pound spring scale to the tow ring and the bolt compressing the spring was screwed down until the desired pull was reached with the foot peddle held down. We checked the tension limiter between rounds and adjusted as necessary to maintain a contestant pull. The winch and turnaround were both mounted on the ground so the tension usually changed as the dew on the grass evaporated. Mounting the winch and turnaround off the ground would reduce this problem. After a few years, we began receiving complaints about not being able to zoom so in order to satisfy those who came to zoom instead of thermal, we added a bypass switch. If the contestant chose to bypass the tension limiter, NO RELAUNCHES were permitted for broken tow lines. A few people had trouble taping the peddle while the tension limiter was cycling. These fliers could usually get better launches by putting the metal to the metal and letting the tension limiter do the tapping. Fliers with Oly II's and similar models didn't notice any difference from normal winches. We finally got tired of listening to complaints about not being able to get good zooms so discontinued using the tension limiter and went to heavier towlines. The original tension limiter base is still rusting in the weeds behind my shed in the woods behind my house. Chuck Anderson RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] line tension
Chuck Anderson wrote: ...Jam/Feb 1977...very smooth pulsing...if the contestant held the foot peddle down and let the winch do the pulsingtension limiter proved to be very reliable and we used if for many yearsthe original tension limiter base is still rusting in the weeds behind my shed in the woods behind my house. = Really interesting, Chuck. Proves there's nothing new under the sun. Probably also proves that talk about F3B winches, limits on TD winches, etc. is unrealistic and that the quest for max catapult power will continue unabated.
Re: [RCSE] line tension
We ran one of those in Cincinnati, for years, It was mine that I had built, from the plans, that I think I still have. We quit using it for the very reasons that Chuck has stated. I ended up giving the frame away...Damn it was 30 years ago -- Jack Strother Granger, IN LSF 2948 LSF Level V #117 LSF Official 1996 - 2004 CSS Gold -- Original message -- From: tony estep [EMAIL PROTECTED] Chuck Anderson wrote: ...Jam/Feb 1977...very smooth pulsing...if the contestant held the foot peddle down and let the winch do the pulsingtension limiter proved to be very reliable and we used if for many yearsthe original tension limiter base is still rusting in the weeds behind my shed in the woods behind my house. = Really interesting, Chuck. Proves there's nothing new under the sun. Probably also proves that talk about F3B winches, limits on TD winches, etc. is unrealistic and that the quest for max catapult power will continue unabated. ---BeginMessage--- Chuck Anderson wrote:...Jam/Feb 1977...very smooth pulsing...if the contestant held the foot peddle down and let the winch do the pulsingtension limiter proved to be very reliable and we used if for many yearsthe original tension limiter base is still rusting in the weeds behind my shed in the woods behind my house. =Really interesting, Chuck. Proves there's nothing new under the sun.Probably also proves that talk about F3B winches, limits on TD winches, etc. is unrealistic and that the quest for max catapult power will continue unabated.---End Message---
Re: [RCSE] line tension
This afternoon, I went out in the woods behind my garage and dug out the original tension limiter winch base and brushed off the leaves to take some photographs. The base is rusty and the wiring is shot but could be refurbished with a little sand blasting, painting, and replace the wiring. I posted the photos on RC Groups for those who would like to know what it looked like. Chuck Anderson At 09:50 AM 12/24/2007, you wrote: We ran one of those in Cincinnati, for years, It was mine that I had built, from the plans, that I think I still have. We quit using it for the very reasons that Chuck has stated. I ended up giving the frame away...Damn it was 30 years ago -- Jack Strother Granger, IN LSF 2948 LSF Level V #117 LSF Official 1996 - 2004 CSS Gold RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] line tension
So Chuck, Tell us how the tension limiter worked and how well it worked. What were the good points and problems? Could such a scheme be used effectively today? Regards, Jim MacLean RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
Re: [RCSE] line tension
I did and used such a winch over 30 years ago. Chuck Anderson At 02:40 PM 12/21/2007, you wrote: There have been various proposals about limiting winch current via a series resistor, but nobody has mentioned directly governing line tension. RCSE-List facilities provided by Model Airplane News. Send subscribe and unsubscribe requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
[RCSE] line tension
There have been various proposals about limiting winch current via a series resistor, but nobody has mentioned directly governing line tension. It is certainly possible to devise a gizmo that would measure line tension, average it over some desired interval, and limit current flow to the winch so that line tension would be capped at some pre-determined amount. Commercial tension meters are common in industrial uses, and it would be straightforward to adapt their design to this purpose. If you broke the line while using this scheme, it definitely wouldn't be your fault, and you'd get a relaunch. Whether the pilot pulsed or not, the equipment wouldn't be overloaded. Every contest would provide identical launching power, and plane designers would know exactly what parameters to use in trying to optimize the plane's performance.
Re: [RCSE] line tension
Tony, I have given the auto line tensioner a bit of thought. Measuring with a three pulley sort of thing and a strain gauge on the moveable pulley or an optical sensor approach should be pretty feasable and low cost. Two problems remain: a motor controller will be very expensive for any analog sort of approach - power FETs ain't that cheap! Which leaves a bang bang sort of controller. Stability issues should be manageable BUT, the pulses to the solenoids will be many and pretty fast unless we use some sort of micro processor to intelligently control things. I don't have the machining tools or skill to make the sensor but in theory it should be fairly simple. I have some crude ideas. The design must allow for fast line speeds and have low mass / inertia on the sensor. The controller should be pretty cheap as it is a simple 4 bit micro and a FET or relay to control the winch solenoid. I envision a small box for the controller which has its own battery supply and plugs between the foot pedal and the winch. The tension is adjusted at the sensor which sits astride the return winch line about 50 feet out. The pilot pulses as he wishes. If the tension gets too high - the winch pulses itself. Anyone with a machine shop want to have a go at making a reasonable cost line tension sensor? I could breadboard up the rest in crude form and see what happens and refine the controller from there. I have two advantages: I fly with the Orlando Buzzards who are really good guys and like to compete and have pretty good weather. I am an electrical designer so that helps a bit. It is possible that a cleverly made sensor would have nothing more on it electrical than a really good micro travel switch and that switch would be in series with the pedal. If the stability / solenoid pulse rate issues are not too bad that alone might work. It should be pretty low cost - if less than $100, should be real practical for most contests to have such a thing. Just thoughts. Comments? Merry Christmas Everyone! Jim MacLean
[RCSE] line tension
James MacLean wrote: ...I have given the auto line tensioner a bit of thoughta bang bang sort of controllerthe sensor...should be fairly simpleThe controller...a simple 4 bit micro and a FET or relay to control the winch solenoid = Yep, that's what I was thinking, Jim. The sensor wouldn't have to be fabricated; sensors are available commercially from various sources, including: http://www.tensionmeters.com/elec.htm#MPHB-Series,%20Base%20Mount,%20Three%20Tension%20Sensors The sensor needs to be mounted on a sturdy frame that can be staked down. That would have to be machined, but it's a simple part. The controller should allow for integration of the readings over a variable interval, and should have circuitry to introduce hysteresis so that it pulses the winch solenoid at a pace that doesn't overload anything. When you think about it, the electronics aren't complicated. This could, at least in theory, address lots of issues. If the gadgets turned out to be not too expensive, it might catch on.
RE: [RCSE] line tension
you guys should all run for congress _ From: tony estep [mailto:[EMAIL PROTECTED] Sent: Friday, December 21, 2007 4:09 PM To: soaring@airage.com Subject: [RCSE] line tension James MacLean wrote: ...I have given the auto line tensioner a bit of thoughta bang bang sort of controllerthe sensor...should be fairly simpleThe controller...a simple 4 bit micro and a FET or relay to control the winch solenoid = Yep, that's what I was thinking, Jim. The sensor wouldn't have to be fabricated; sensors are available commercially from various sources, including: http://www.tensionmeters.com/elec.htm#MPHB-Series,%20Base%20Mount,%20Three%2 0Tension%20Sensors The sensor needs to be mounted on a sturdy frame that can be staked down. That would have to be machined, but it's a simple part. The controller should allow for integration of the readings over a variable interval, and should have circuitry to introduce hysteresis so that it pulses the winch solenoid at a pace that doesn't overload anything. When you think about it, the electronics aren't complicated. This could, at least in theory, address lots of issues. If the gadgets turned out to be not too expensive, it might catch on.
