Hydraulic Pumps for PowerLifts.

[JamesM]

The power rating of a motor is at a particular voltage. Less voltage, less current, less power.

Its not just ohms law however, its also the inductive reactance of the coils (measured in ohms) which is proportional to frequency (speed of the motor). If you reduce the voltage the motor will turn slower which will decrease the inductive reactance of the coils which will increase the current a bit but as the voltage is lower overall the current will be less. In otherwords if you halve the voltage the current won't be half, it will be a bit more than half. If you keep the voltage the same but load the motor up the load will slow it down so its inductive reactance decreases so it pulls more current. If you stall it and the inductive reactance will be zero so all you will have is the dc resistance of the coil (a long bit of wire) between the battery terminals, meaning you've shorted the battery out with a long bit of wire which then melts.

[MrRob]

[JamesM]

[JamesM]

you will need a chunky switch to run it like this and you will have to run a feed direct from the battery to the dash. Dont use a supply thats allready present at the dash. It would be much better to use relays or solenoids local to the pump and battery at the back of the boat.

[MrRob]

explain to me relays and solenoids as I have no idea. can i get them from maplins?

[JamesM]

Originally posted by Johnny Boat Dude
It would be much better to use relays or solenoids local to the pump and battery at the back of the boat.

And that would look something like this

[JamesM]

Originally posted by MrRob
explain to me relays and solenoids as I have no idea. can i get them from maplins?

A relay or a solenoid is just a switch. However rather than physically making or breaking said switch with your hand you open and close it by appling a voltage to a second set of electrical terminals, this is known as energizing the relay or solenoid. So there are the main electrical terminals that you are making or breaking and the second set that you apply the voltage to in order to make or break the connection between the main terminals.

It doesn't take much current to energize a relay or solenoid but depending on their rating they can be used to switch large currents. This means you can locate them local to your battery and pump/motor and keep all the heavy current and thick wire in this area and use a dash mounted switch with a smaller feed from the normal dash wiring to energize the relays or solenoids. So rather than switching the motor down long bits of heavy wire from the dash board with a big heavy dash mounted switch you are switching it local to the pump/motor/battery by remote from the nicer smaller dash board mounted switch. Take a look at the diagram above, the relays or solenoids are the new addtions in the middle. Solenoids are genrally used when there is to much current for a relay to handle, such as when switching a starter motor.

Bear in mind if your going to run solenoids and relays for the trim pump, powerlift, trim tabs, starter motor aswell as tacho and maybe GPS and other bits and bobs all from your dash supply you will need to make sure that the feed to the dash is of an adequate size.

[JamesM]

You can get relays from maplins but you need to know how much current the motor is going to pull when loaded up in order that you can get relays of an adequate rating. Also ensure you get ones that use a 12V DC supply to switch them.

[rama]

There is a general difference between a solenoid and a relay,
A Relay is generaly an electromagnetic switch, using a small current to switch a large current, I.E, Trim relay, or Starter Relay

A solenoid is generaly refered to as a electromagnetic linear actuator. In that it produces linear movement.

On the majority of modern vehicle starter motors we refer to the solenoid/relay as a starter solenoid as it does both the job of the relay and solenoid, first throwing the pinion in to the ring gear and then engaging the motor,

The majority of outboards use bendix starters , using centrifugal force to engage the pinion and therfore it is just a relay that is used.
Im sure i missed something out but hope this helps to distinguish between the two

[JamesM]

Yup solenoids arent just used for electrical switching, we use them at my work for opening and shutting hydraulic valves they're also used on door locks and all sorts of other things. In this post however we are talking electrical switching, that why I likened them to a bigger chunkier version of a relay. Mercury use solenoids for power switching on their starter motors and their trim pumps.

[MrRob]

Couldnt I just rip the solenoids off an old trim pump?

[JamesM]

Probably, don't see why not!!!

[Burty]

i got a trim pump for sale

[MrRob]

Why didnt you tell me before! !
What you want for it? Not a lot I hope!

[Burty]

only just fort about it
say £150 including the hoses

[Taz]

Thats a cheap pump dude i wouldnt mind buying it as a spare if mr rob dnt

[MrRob]

its sold taz! sold! I need it more than you!

[Taz]

Oh well i already have 3

[MrRob]

And you need a 4th?

[Taz]

Yeah im greddy its like my wives i cant ave enougth of them