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Jeffa Autopilot Failure |
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colinc
Captain Joined: 08 May 2019 Location: UK Status: Offline Points: 169 |
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The manual for the Hypro is here
“Designed for under deck installation only” “Avoid contact with sea water” And as said, designed for much smaller boats and with much less thrust than the DD1. Frying pan to fire?
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ohthetrees
Captain Joined: 24 November 2019 Status: Offline Points: 169 |
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Heard back about a couple of colinc's questions. My assumption was that the DD1 would have less mechanical advantage at extremes of rudder angle, but that seems not to be the case.
Here are my Q's and answers inline:
1) Do I need to restrict the range of motion in the autopilot software? It seems to me with the link arm moved further out on the tiller arm, the DD1 arm must go through a greater range of motion. It seems that the DD1 would have very little leverage at extreme rudder angles. The angle of motion should be the same on the quadrant and therefore the same on the autopilot software where the rudder feedback is mounted. The DD1 has to move further compared to your current setup which in turn, with more leverage, makes the drive stronger. At the outer positions the DD1 will have to move further to move the quadrant the same distance which again makes the DD1 stronger. 2) Surely I must shorten the link arm. Can I modify mine, or do I need to order a shorter one? The draglink can maybe be shortened a bit more. You should try it out, I think it will work out for you. After setting up the new position, please check the outer positions that the output lever isn’t close to camming over. |
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colinc
Captain Joined: 08 May 2019 Location: UK Status: Offline Points: 169 |
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Thanks for getting the answers to those questions. It confirms that the draglink ideally needs shortening whe nmoving holes. About 2cm in my boat which means getting the next size down draglink. The correct length will have the autopilot and rudder drive arms in the centre of their arcs when steering straight ahead. That "centre point" of the arcs has to take into account the different alignment of the drive and tiller. It is also of note that the design relies heavily on the geometry between the two drive arms. Jefa confirm that there is significantly more rudder torque at the extreme port and starboard due to the different arcs of movement. My previous calculation of an extra 20% torque between the two holes was for the central position. I think the difference will be much greater at the ends of the movement. I'll try to work out the much more complex maths of those two positions. In the meantime can you ask them one more question please: "how important is getting the correct offset between the centres of the drive and tiller shaft? How much change in loading would there be if the offset was a lot less than that given on the Direct Drive Specification Form." It would also be useful to know how the drive handles overload situations. What happens if a wave is stronger than the drive can push against? Edited by colinc - 16 January 2020 at 15:20 |
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ohthetrees
Captain Joined: 24 November 2019 Status: Offline Points: 169 |
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Hello, it's been a while. I've been in Hawaii working on my boat. I have some answers from Klaus:
Offset geometry is from the old book, and nowadays we ask people to forget about it because it actually don’t add up 100%. What you should do is mount the draglink between the arms so that the draglink is perpendicular to the arms when steering midships. When this is done, check the outer positions to make sure the output lever isn’t close at camming over. If it is, then adjust your draglink. I recommend anyone to get as close to this with what they have, don’t move the drive unless it is way off from perpendicular at the tiller arm.
I cannot tell you how much change in loading, depends on the amount of offset. Use common sense around the perpendicular setup and you’ll be fine.
The fuse only goes at continuous load or high peaks. So the drive will take a “soft” push at high torque until the fuse goes without problems. On the other hand, should the drive take a hit at high force, the gearwheel teeth on the output shaft might bent or break off completely. The output shaft can be rotated 180° by removing the output lever, rotate the output shaft, and mount the output lever again. Should this happen, then we recommend you order a spare part or send it to Jefa Steering for refurbishing. |
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ohthetrees
Captain Joined: 24 November 2019 Status: Offline Points: 169 |
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I have now been to see the boat, and worked on the autopilot. I have removed the autopilot, and found damage on two gears. The drive gear teeth are totally broken. The ouput gear teeth are damage and bent. In the picture, I have already rotated 180° by removing the output lever, rotate the output shaft, and mount the output lever again. I have disassembled to the point you see in the picture, but I do now know how to remove the gears from this point. For the ouptut gear, even with the output lever removed, the output gear would lift up completely away. I don’t know if there is something holding it in, or whether I just needed more force. For the input gear, I do not know how to remove the gear. If anyone has tips, I'd love to hear. |
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jdderijke
Lieutenant Joined: 13 February 2016 Location: Greece Status: Offline Points: 49 |
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Hello, The drive gear is removed from the other side of the unit. You took of the bottom plate, and this is indeed needed to remove the output gear, but since you already rotated the output gear all the bend teeth are out of the way. Mount the bottom plate again, turn the unit around and dissassemble the other side. Only the top part needs to be removed. It will show the planetary gear and in the middle you will find the other side of the drive gear. You can pull it out from there. Be absolutely sure you found the broken teeth and did not leave them somewhere inside the unit. Jefa can send you a new drive gear...
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JD
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jdderijke
Lieutenant Joined: 13 February 2016 Location: Greece Status: Offline Points: 49 |
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An update on the Hypro linear hydraulic drive experiment.... We
left Curacao in 20-25 knots of wind on the nose, in confused seas of
about 2,5m from multiple directions. The Hypro steered fine in the
beginning (in the lee of the island). When the waves started to build
some of them hit the rudder sideways with force and the Hypro relief valve opened.
The effect was that the drive paused for a moment, one could hear some
(irritating) noise coming from the relief valve, and then the drive
continued its work. During this the rudder stayed in the position it was
in. At no point was the boat/rudder out of control.........but....... The
drive makes a lot of noise. The DD1 (being a pancake motor) is
controlled by the computer using proportional power via (i think) PWM
(Pulse width modulation). This does not work with the Hypro, the Hypro
motor is either ON or OFF and therefore makes a lot of noise
ON-OFF-ON-OFF etc. whereas the DD1 is modulated down to almost silent
mode when small corrections are made in light weather. In heavy weather
with lots of force on the rudder they produce about the same amount of
noise....but hey, that is mostly not the situation.... On
top of that i asked a friend of mine, who is a marine engineer, to make
some calculations between the Hypro and the DD1. The result was that
the DD1 indeed produces more pushing force, and (to my surprise) this
force INCREASES with the rotation angle of the DD1 arm.... So
it was 4500N from the Hypro versus roughly 10000N or more from the DD1.
And the test showed that in 20-25kn wind the Hypro already activated
the relief valve (reached its maximum of 4500N) ......I hate to admit it, but it seems i was wrong in my earlier posts.... I
replaced the drive gear AND the output gear of the DD1, moved the pin
to the outer hole and mounted the revised DD1 back in place. I tried to
shorten the push-rod...BUT (and this is important) .... found out that
if you do that the DD1 can actually travel beyond its top dead-point. If
that would ever happen it would cause the drive to work contra (left
becomes right and vice versa)....very dangerous.....so i left the
push-rod as is. (hope you understand what i am referring to here..) Conclusion:
The Hypro is nice to have as a backup and will do the job, but is
indeed not strong enough for the H505. On top of that it produces
significantly more noise in calm weather. I will keep it as a spare
system because i still don't fully trust the DD1 after all that i
experienced with it..... Jan Dirk
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JD
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kipwrite
Commadore Joined: 14 October 2015 Location: New York Status: Offline Points: 408 |
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Been following this thread for awhile, and I'm glad we are all being more thoughtful about the DDI units on our boats. Thanks to jdderijke for his post on his new hydraulic drive.
On my 505 #123, my Jeffa-rebuilt unit has been flawless since it was rebuilt by Jeffa, and the issue with the inner/outer hold was resolved. I've been careful with it in heavier seas. A question for those of you who have installed a hydrovane, as I have on my boat. Has anyone fitted a tiller autopilot to their hydrovane for use as a back up autopilot? I'm thinking of adding this as a back up, but would like to know if anyone has any experience with this approach, how the system has performed, etc. Photos would be helpful.
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Kipwrite
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kipwrite
Commadore Joined: 14 October 2015 Location: New York Status: Offline Points: 408 |
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My rebuilt DD1 started showing two symptoms recently, an intermittent clunking noise when the autopilot is engaged, and a clicking sound in standby mode when I turned the helm. The latter was worse after the boat had been unused, and seemed to improve with use.
The Jeffa team thought the clicking sound was the result of a sticking magnetic clutch pin/spring set, so I ordered a new set, and yesterday opened the unit up. One pin and magnet set was quite rusty, and the magnet was partially consumed by rust. I’m amazed it still worked at all. Some water had clearly intruded. I also found one bent tooth on the planetary gear output shaft, and I’m in the process of getting a replacement shaft. I think this is the likely cause of the clunking sound. All other parts rotate smoothly. These units open up easily and Jeffa has been helpful in providing instructions and diagrams. It is worthwhile opening them up when they start to make funny noises. Will try to post a photo of the rusty pin and magnet. |
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Kipwrite
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Brufan
Rear Admiral Joined: 16 December 2010 Location: Belgium Status: Offline Points: 629 |
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To avoid (or limit) water ingress, you have to find a suitable plastic cover (i.e. Electronic plastic housing or 'box') and put it over cables glands.
Take the DD1 out and put it upside down on a workbench. You offset plastic cover over the edge of housing to have a "gap" to allow cables to be run downwards and glue it. Through the gap, pour two parts liquid silicone to fill plastic cover. Let it set and put DD1 back in place. I did this 4 years ago after two motor breakdowns due to water. Problem solved ...so far.
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Bruno
hanse 355 - 57 S/Y Spicy Ginger White hull, 2 cabins, Volvo D1-30, Selden rig, removable mainsheet track system, Simrad (now B&G)-Jefa autopilot. |
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