Originally Posted by skipmac
Well then. It must be the Alpha web site that's showing some age.
Assume you have a linear drive and not a hydraulic unit. My research
on hydraulic AP drives shows they include a bypass for the fluid when the drive is not active and I have heard comments that there is some restriction in the fluid flow through the bypass.
Which brings another question. I have seen a number of recommendations for hydraulic drives being more reliable than mechanical drives. But my question is the power for either system comes down to an electric motor
which I would think the most likely failure point so why is the motor in a hydraulic drive supposedly more reliable than the motor in a linear drive unit?
It does sound like a pain but have never read a single
complaint about the function so it must work better than it sounds.
Which is the reason it is so difficult to compare power draw between different brand autopilots. You would have to install different APs on identical boats and sail in identical conditions with identical sail trim and balance to get exact comparisons.
One reason Alpha claimed to draw less power than older gen APs was other brands used extra power to keep a clutch engaged to drive the rudder where the AP did not (because of the drive?).
That's very interesting information for me. Simrad is certainly on my short list for when I upgrade. But referring back to my comment above, what kind of drive are you using with the Simrad?
It would indeed defy logic to pay more just to not have a feature but I'm guessing the perception is the higher priced unit works better, is more reliable or offers some other benefit. But twice as much? Don't recall
the exact numbers but when I researched below decks APs I thought the price
for all of them were in the $4-$5,000 range.
Years past I saw a few comments from users that had problems with support when they had problems while outside the states and had limited options to send the units back to the factory.
From their website, the basic package will cost ~$5,600. If you want a gyro compass
with the ability to connect a wind
instrument and a computer (half of the functionality of a modern AP), then the costs go north of $6,600. A comparable Simrad system that includes complete electronic integration capabilities, waterproof control head
and far more functionality will cost ~$3,500. Heck, upgrade that to the larger system and it only sets you back ~$4,400 - still less than Alpha's basic system.
We have a Raymarine
electromechanical drive. It has no backdrive pressure at all. Our old B&G hydraulic drive had tremendous backdrive pressure. I have been told that the newer hydraulic drives do not have much backdrive pressure at all, although I do not have first hand experience with them.
Our B&G drive was mostly trouble-free for 13yrs - I had to replace a seal and the motor brushes
. I expect the same from the RM mechanical drive. The hydraulic drives produce a bit more torque and thrust than the mechanical drives and have less moving parts
. The mechanical drives have a whole planetary gear
system and ball screw going on compared to hydraulic drive's simple check valve system. When a mechanical drive does goes tango uniform, it is pretty much done, where a hydraulic drive can be rebuilt almost anywhere. But, like I said, I expect the same trouble-free existence with our mechanical as I did with our hydraulic.
I have sailed on boats with an Alpha, and the fact that the owner's do not complain about the engagement mechanism surprises me. They have either drank that kool-aid or have never used another type for comparison.
The clutch uses very little power - maybe 0.5A. I guess that adds up over time, but is not a good reason for putting up with a cumbersome mechanical engagement mechanism.