Servo Stretcher

[philair]

For those who liked the idea shown in Model Yachting about modifying a CS80 to get 180 degrees, but aren't into soldering resistors and things, check out RobotZones servo stretcher which works with all servos & increases throw to 180 deg. without compromising speed. They're at: "http://www.robotzone.com/customer/product.php?productid=183&cat=19&pag"

[Gene Rosson]

The servo stretcher from Robot Zone works very well. Maybe too well. Attached to a CS80 it gives about 200 degrees of swing. I have not installed this in a boat yet. The servo seems to be plenty strong and very fast, even on 4.8 volts. That speed may make a problem when trying to trim sails delicately. Aside from that possible problem, I am suspicious of the plastic output shaft on the CS80.

I paid Tower only $29.95 for the servo. Cheap! [:D] $14.95 for the stretcher. I am going to try this setup just because I can. On the other hand, I dont believe in Santa Claus, the tooth fairy, or the likelihood of beating the system. I may have to abandon the bargain and buy an RMG [|)] because of the free lunch rule.

The CS80 little brother, the CS70 costs more and it has ball bearings with a metal output shaft. Interestingly, the Hobbico CS70 is identical to the Hitech HS645mg. These compact servos ought to be sufficient for rudder and jib trim. How come none of the information one gets with servos mention amperage ? I suspect that these little jewels are amp suckers.

Anyone have experience with this setup on an EC12 ?

[philair]

So far, the CS80 with the 'manual' conversion per the AMYA magazine works perfectly in my EC12. I get about 170-175 deg. of travel which is enough.

It is very strong and very fast - the speed & tender touch on the stick takes learning (compared to the Ozmun I took out)but so far so good, & a lot less work than refitting an RMG.

[Mike D]

I was going to do the same thing as you did (I had a very old "banger" Ozmun swing arm from the 70's/early80's)but was advised to use a newer Ozmun W-12. I purchaed the W-12 three weeks ago and it works as advertized but is a little touchy on the "stick". I should have tried the CS80 ($30 vs $160) but feel in long run I made the right choice.[:D]

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by philair</i>

So far, the CS80 with the 'manual' conversion per the AMYA magazine works perfectly in my EC12. I get about 170-175 deg. of travel which is enough.

It is very strong and very fast - the speed & tender touch on the stick takes learning (compared to the Ozmun I took out)but so far so good, & a lot less work than refitting an RMG.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

[Gene Rosson]

since writing the comments about the CS80, I have experimented a bit more. Attach servo to workbench so that the arm extends over the side, the arm has a string on which various weights can be attached. A reliable ampmeter is placed in the battery circuit.

The servo is a bear. It will snatch a six pound weight, from a five inch arm, with violence akin to a ballista. The servo is ,as suspected, voltage sensitive. It operates fairly well with 4.8 volts but it becomes real jerky when heavily loaded. At 6 volts it is not jerky, just sudden. The amperage draw was not excessive but surge current, when heavily loaded, could exceed 5 amps. That is instantaneous current so it is not terribly serious. Based on these experiments, I would suggest that battery wire and switches be of the heavy duty variety. Wouldn't hurt to have a fuse in the line as well. If you get a sheet jam it either going to break the sheet or set fire to the boat. Better to blow the fuse.

During the test procedures I noticed a lot of flexure in the plastic output shaft. I abandoned the CS80 for that reason only. I reckoned that the shaft is going to break at the exact moment when I was trying to pull some sort of tricky maneuver, and therefore cause my boat to T Bone someone elses boat.[V] Everyone knows about Murphy's laws. Right ?