I’m in search of a decent drum servo for a Marblehead class yacht.
I’ve done searches, but the results are several years old, where some of the recommend servos are no longer in production or just stupidly expensive (IMHO).
I know of Hitec’s drum, but everyone says it’s slow (is it?). Futaba I think has quit making them. GWS has some, digital even, but not sure if they are strong enough for a Marblehead. RMG is just to dang expensive for me.
The Hitec drum hs785 is a good reliable workhorse, but yes, it is slow at about 1 second per revolution, so 4 seconds is normal for full travel. OK for fun races, may be a bit slow for top competition, but $50 is a great deal.
RMG is great, if you want the power and speed, there is no equal.
You can have good, fast and cheap. . .pick any two
After checking out the torque range you are interested in I have the following suggestion -
People have ‘Cussed’ these units before - but, in spite of the criticism there are some good ones out there.
Its the ‘Eurgle 64.5g’… Available on eBay…
I have used around 4 of these units at least, and they are much better than the Hitec units for speed/weight & power.
They do tend to come with a personality all of their own, and can be subject to electronic ‘glitches’.
I tried to warn you - I will not B.S. here!
BUT, and its a ‘big’ but, because there isn’t anything on the market that works quite as well for the Dollar, or the same weight for the fact.
I do, however, recommend you over order, test each one in turn, and pick the least Jittery.
I use these in my AC120 and the power is great, just wish they would have a bit more speed and not be so noisy or jittery.
Reliability is fine as I have accumulated a good number of hours on both AC120’s and still on the original units in both yachts in salt water. I also used them in my Open 1 metre for the sail sheeting and canting keel…
I agree ( with the disbelievers) - They are not the finest examples for a sailwinch, but they certainly beat the lazy Hitec alternative before it gets out of bed.
I’m sure that people might shoot me for recommending something that isn’t quite up to scratch (if you get a bad one) but, the Hitec unit is also a pathetic alternative when you compare it to a RMG if we are honest.
Given the choice - I’d rather go with a bit more speed and power… Buy a few and pick the best is my advice and it will still cost you considerably less than a RMG…
If you are on a budget you want the best ‘bang per buck’ then these are really not that bad…
At the end of the day - You pays your money and you takes a chance either way!
Just trying to give a balanced review from 1st hand experience…
Thanks for the suggestion. I looked around for Eurgle servos and found that they have a digital version: Eurgle 56g ≧9.5Kgf.cm 6 Circle RC Sailing Boat Digital Metal Gear Water Resistance Servo Model Number : rcps91116_22ymb The specs aren’t to far off from the analog version. But I’m wondering if the digital one might be of higher quality? Digital are usually are, but who knows.
I think you ought to take a look at the gear and servo combo’s available at www.servocity.com.
I don’t have any specific part numbers for you, but we have club members that are using these
products as an alternative to RMG,and I believe at half the cost - and right here from the U.S.A.
(one of our guys just set one up for a Santa Barbara class boat)
What about an ARM Servo ?
I’m still considering a normal servo with an arm. Then I would get a Hyperion HP-DH20-UCD and program it to 140° degree movement. But I’m not sure I have enough room for an arm. I just have to sit down with a ruler and do the math. Also try to get the sheet lines in place might be a pain.
it is in italian but the pictures show how it is done :
You can always ask renato how he did the sheeting circuit !
lots of guys use this ==> http://servocity.com/html/hs-7955tg_servo.html in their IOMs. Maybe more expensive than the Hyperion, but twice the torque (or more) and titanium output gears. Never heard of anyone having problems with them. All use either an arm, or a “cam” shaped arm. Mine uses a 1:2 sheet arrangement on a 2.75" arm that will pull in 11 inches of sheet. You can use a longer arm for more travel but the “power” will go down too. A cam, or drum on the output shaft will get more travel and be more powerful over the whole range of sail settings, where the arm will have lots of torque at each extreme (close hauled or boom all the way out), but not much in the middle range.
The Hitec HS7955TG has about the same torque has the Hyperion HP-DH20-UCD at 7.4V, and darn near 3/4 the price ($32 vs $112 USD). I’ve used other Hyperion servos in my sailplanes, they are excellent servos.
I think I will take a gamble on the digital Eurgle drum servo, for $30 USD shipped it isn’t to bad.
I have three RMG winches. The one in my IOM started to act up, so I bought a replacement. Then the one in my Soling 50 started to act up too. It was then that I realized the NiMH battery pack didn’t have a discharge rate that would feed the winches the amps they need. I switched to Li Ion Batteries and have had no further issues.
The digital Eurgle winch/drum servos came in, rather quickly form Hong Kong to my surprise. Only 3 days from leaving Hong Kong post to my door. I was lucky to place the order before Chinese New Year (I wish we had that type of holiday, 1 or 2 weeks off where everything shuts down).
They are OK. One is really quiet, the other is noisy (comparatively). They both twitch, the quiet one more than the loud one. It looks like the deadband is to narrow so it’s hunting. I wrote where I bought them asking if there was a programmer for the servos (some digital servos you can program the center, end points, deadband, speed).
I took one apart to see maybe if it was the POT that was sub-par, but it’s a hall sensor! Wow, that was a surprise. Not much to do with that. One thing that I’ve noticed working with Hall sensors in the past, is they sometimes take some usage before they “calm” down. So I put the twitchy one in a 36/600, and played around with with it for awhile. Sure enough, it calmed down, some. It still twitches, but not at bad. Hopefully with some more usage it might get better.
Oh, putting the servo back together was a pain, trying to get the O-rings back in place, so they are water resistant.
Would I recommend them? Can’t say, yet. Need get them on the water and put some time on them (need some wind, it’s been quiet now).
They are strong. Over kill for the 36/600. When powered off, you can’t spin the drum by hand. They are all metal gears inside. No nylon/plastic sacrificial gear to be found.
I got 6 of them last year and the year before 3 analog and 3 digital, all noisy at different degree.The transmitter used is Hitec Ranger III Sky FM - 41Mhz range - Receiver Hitec HFS-05MS
Recently I bought a new transmitter Hitec Laser 4 used with two differents receivers one as above and one HFS-06MT as part of the new set.
Surprise ! the noisy servos are all become quiets.
Changed the trasmitter with the older one Ranger III Sky with the two receivers and all servo became noisy again.
A friend of mine got the same problem, but recently received the 2.4Ghz set and the noise disappeared.
So why with one trasmitter the noise appears and disappears when the other trasmitter is used ?
Every brand of transmitter has a slightly different pulse train for the PPM data stream. Even different models from the same manufacturer. Servo manufactures try to take into account all the variations, but it just doesn’t always work out perfectly, the obvious trade off is the noise as the servo is trying to interrupt the data stream properly and set it’s position.
Then there are programmable digital servos. I really like them because you can hook them up to your computer and change the various settings as I said before, end points, speed, deadband, center. But as I sometimes forget, not all digital servos are programmable. I hope there is a way to program the Eurgle’s.
The other draw back is they tend to draw more amps than analog. But with battery technology, LiPo, LiFe, LSD NiMh, etc., it really isn’t an issue.
Here is a fair description of the differences of digital and analog servos:
I’ve been using Graupner Regatta Winch (#5172) and would like to ram it up from 6.0 V @ 7.2 V for extra speed & torque off a 7.4 V 2S Lipo.
Will the extra .2 V be a problem running directly off the Lipo ?
Further, taking the drum off the winch today I saw for the first time a small hole at top of winch casing which has screw head adjustment, searched all over the net and cannot find any reference to what it does …any ideas ?
Before anyone says just try it …please don’t :rolleyes: uh hmm… had bit of a blond moment soldering wiring into new hull with battery connected and short-circuited the whole system including my winch :scared: and have to wait 2 weeks for replacement (seems to be a supply shortage of servo’s in Europe)
Good question Alan -
and with servo prices so low, it would be interesting for the “electronics guys” to start a thread where discussion can take place on how much over-voltage is still OK versus, “don’t even think about the added .2 volts”.
Will watch for responses.
Remember a 7.4V lipo is actually 8.4V fully charged and 6.6 at full discharge. I use them on my RMG’s and have had good luck, about 150 ma per hour battery usage.
Thanks Slot …I saw 8.4 V @ 100% come up on my voltage meter but never thought about it, thanks for turning my light on :idea_125:
I’ve only been using Lipo for only few months and impressed with amount of sailing time can have, but with voltage and percentage reading coming up on the meter display, could never work out which one I should watch.
Showing my ignorance on electrics here but if Lipo goes down to 6.6 V does meter read 0%(discharged) does it stop supplying charge or does it continue ? understanding the Graupner winch can draw down to 4.8 V, uncertainy here as I understand if you take Lipo beyond certain point of discharge, it can damage the cells.
@ mmickels, RMG is last stop on my shopping list albeit ther’re the best but they are weighty and power hungry
@ Guzz, how have you found the digital Eurgle winches you bought few months ago ?