FYI - Cirrus Servo Mod for sail winch
04-20-2006, 09:56 AM
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FYI - Cirrus Servo Mod for sail winch
Just thought Id pass this along, maybe some usefull info for the other tinkerers out there.
For my custom 36" boat build process I was looking for a sail winch servo. I recently replaced two servos in my elec heli with small Cirrus servos that really work good and were relatively cheap.
Because of size limitations I wanted a servo that was close to standard servo size yet had a bunch of torque. The Cirrus 704MG looked like it fit the task with 181 oz/in at 4V and 195 oz/in at 6V, 1.6" by .78" by 1.61" and only 46g. It indicated 60* travel which I thought was 60* side to side or 120* total (It didnt look like 120* to me more like 90*). Since I really wanted the smaller servo size I decided to try to modify it using the guidelines (Hitec Servo Mod) I read in the USOM construction guide. I figured that I was going to void any warranty by aeroplating the thing anyway......
I dissasembled the servo. The main output gear (all metal gears) had a travel stop pin that I drove out with a tiny punch. The pot had long solid pins connected directly to the circuit board. I snipped those mid way to leave room for solder connections and pulled back the CB and pulled out the pot. Soldered 1/4 watt 2.2k-ohm resistors on each of the outer pot connections (2). The hard part was getting everything to fit back into the small case ( I went with long leads first to test and then made short ones for the final fit).
With the Cirrus pot and the resistors travel increased to about 120* to 140* (eyeball - no protractor). I had a Hitec pot left over from my robotzone gearbox mod from a Hitech 815BB sail winch so I tried that pot which got the servo travel up to 180* (eyeball). I dont know why the Hitec pot was different since they both were marked as 5K.....maybe those of you smart electronic guys can chime in on that -- I would like to know why.
Caution - I have no experience using this servo. I wont have any idea if it works until the boat is completed (maybe in a few months). I also dont know if they are as reliable as the Hitec or Futaba stuff. They indicated that the servo was good for RC Monster Trucks - which I assume take a beating.
So for about 35$ and less than an hours work I hope I have found a cheap, small size, high torque servo solution. My other option looked like one of the new small high torque digital servos but they are more than 2 - 3 times that price.
Good luck,
Spin
For my custom 36" boat build process I was looking for a sail winch servo. I recently replaced two servos in my elec heli with small Cirrus servos that really work good and were relatively cheap.
Because of size limitations I wanted a servo that was close to standard servo size yet had a bunch of torque. The Cirrus 704MG looked like it fit the task with 181 oz/in at 4V and 195 oz/in at 6V, 1.6" by .78" by 1.61" and only 46g. It indicated 60* travel which I thought was 60* side to side or 120* total (It didnt look like 120* to me more like 90*). Since I really wanted the smaller servo size I decided to try to modify it using the guidelines (Hitec Servo Mod) I read in the USOM construction guide. I figured that I was going to void any warranty by aeroplating the thing anyway......
I dissasembled the servo. The main output gear (all metal gears) had a travel stop pin that I drove out with a tiny punch. The pot had long solid pins connected directly to the circuit board. I snipped those mid way to leave room for solder connections and pulled back the CB and pulled out the pot. Soldered 1/4 watt 2.2k-ohm resistors on each of the outer pot connections (2). The hard part was getting everything to fit back into the small case ( I went with long leads first to test and then made short ones for the final fit).
With the Cirrus pot and the resistors travel increased to about 120* to 140* (eyeball - no protractor). I had a Hitec pot left over from my robotzone gearbox mod from a Hitech 815BB sail winch so I tried that pot which got the servo travel up to 180* (eyeball). I dont know why the Hitec pot was different since they both were marked as 5K.....maybe those of you smart electronic guys can chime in on that -- I would like to know why.
Caution - I have no experience using this servo. I wont have any idea if it works until the boat is completed (maybe in a few months). I also dont know if they are as reliable as the Hitec or Futaba stuff. They indicated that the servo was good for RC Monster Trucks - which I assume take a beating.
So for about 35$ and less than an hours work I hope I have found a cheap, small size, high torque servo solution. My other option looked like one of the new small high torque digital servos but they are more than 2 - 3 times that price.
Good luck,
Spin
04-20-2006, 01:30 PM
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RE: FYI - Cirrus Servo Mod for sail winch
Spin;
There is a great info page at Alimos Model Yacht Club on adjusting servo winch rotations. I have done this mod. on 2 of my TX's to change the rotations from 3.5 revs. to 1.75
revs. I had to do this so I could use the same TX for my Ice Yacht and one of my sailboats in the summer. I added a double pole double throw switch to bypass the resisters in circut.
The info on the page might be hard to find but it is there.
Nothing sooths the mind like RC sailing.
There is a great info page at Alimos Model Yacht Club on adjusting servo winch rotations. I have done this mod. on 2 of my TX's to change the rotations from 3.5 revs. to 1.75
revs. I had to do this so I could use the same TX for my Ice Yacht and one of my sailboats in the summer. I added a double pole double throw switch to bypass the resisters in circut.
The info on the page might be hard to find but it is there.
Nothing sooths the mind like RC sailing.
04-20-2006, 08:18 PM
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RE: FYI - Cirrus Servo Mod for sail winch
rcsailor,
Thanks for the link - great info. I am going with a swing arm sail control and not a drum type winch so it looks like the TX mod wouldnt help me -- but I am sure that the info will help others using drum winches. Any info is good info.
Thanks Again,
Spin
Thanks for the link - great info. I am going with a swing arm sail control and not a drum type winch so it looks like the TX mod wouldnt help me -- but I am sure that the info will help others using drum winches. Any info is good info.
Thanks Again,
Spin
