24V Motor with 90:1 Gearbox - Change to AC Motor?

DC has a far better starting torque (this will be a problem if you switch over to AC) else you have to have a much larger motor and also the speed control advantage will be missing unless you go for VFD.

Did you consider brushless DC Motor ?

Given the small dimensions of the motor it may be better off to just upgrade the whole drive or winching system itself to a larger system that is capable of handling the loads being demanded of it and is driven off of what ever the primary power source the boat uses.

They probably feel DC is safer on deck than AC. See if someone makes a motor with a better duty cycle, maybe a whole new winch engineered for the job. A light duty winch will just keep breaking down.

First, I'm a little surprised to hear that this motor "requires too much maintenance." A phrase like that makes me wonder if any motor can put up with the abuse this crew will give it.

All of the gear reduction (a total of 270:1) you have, brings me to several questions. How much of a mechanical load happens at the output of the gear reduction? How fast does it have to move? You say that this is part of a towing winch, are you sure that the gear reduction is not also worn out and thus dramatically increasing the effective load on the motor? With this being the drive for a winch intended to tow things underwater I expect that the mechanical load could easily be a lot more than you think, particularly when this vessel goes through some large swells and your towed array is being hauled up.

Without knowing many more mechanical specifics, I would be very hesitant to switch to an AC motor on two grounds. First, DC motors produce the most torque at start up, the exact scenario one would expect for hauling something out of the water. Second, your supply and wiring is already fabricated for 24VDC operation.

Now maybe you do need a more powerful motor and reduction configuration. But I would not say that an AC motor is better with the implied information you have. If anything, an AC motor would be worse.

The crew can only turn it on and off. The arrangement is such that the operators have a proportional control switch. This is needed because when the equipment is being towed behind the vessel it needs to be lowered and raised accordind to the seabed conditions. I totally agree with you all. I believe it needs to be up rated in some way. Most winches that are used offshore are either single phase or three phase ac. These winches are so small they cannot take the duty cycle and the condition.the motors them selfs look like the ones you find on 4x4 winches. On Monday I will take a closer look to find out what the exact power plus model they are.

The previous replies all address very valid points. This motor will only be a few hundred Watts at most, I would guess at 200~300W.

What was the system originally designed for? Was it by any chance a sports fishing reel? We work on winches regularly (sail, anchor and crane) and I have yet to see such a small motor, even on a small sail boat winch.

So, if you want to go to an a.c. motor you need to consider the following:-

1. Can an ac motor be safely fitted. Is it inboard in a dry environment?

2. Will the winch mechanics take the work? If this is sports equipment with a low duty cycle then the gearbox may also be designed for this duty.

3. What will be the problems in changing the supply to ac? 230 or 110? A new cable run from the MDB?

4. Are there any off the shelf units engineered for this duty

If you do decide to go ac then remember to make the controls at low voltage. You needn't use dc, it is usually easier to use a small control transformer and use 24Vac as the control.

I doubt the torque characteristics of an ac motor will be a problem given the very low gear ratio and the stretch and catenery of the towed line

Regards

Chas

The winch was designed by a company that has no experiance in designing winches. I honestly think the winch is incorrect for this type of application. Which ever motor takes it's place it needs to be ip 65 atleast because it will be subjected to the elements. If any of you see one of these winches compared to other winches used for this type of work you would firstly laugh then realise how badly they are made. What annoyed me was the company that sold it has a good reputation, but when it comes to winches they do not have a clue plus the prices are far to high. I will find out the watts of the motor. These winches Are ment to run for 24 hours for days on end. Do any of you know a good site for gear ratios and torque calculations? I will get some more information then Hopefully a solution can be found bully

I do not know from personal experience of any suitable winches, although I'm sure they exist. The first thing I'd consider finding out is what type of load this winch will encounter. To quantify this, I'd start with the tensile strength of the cable that you are already using. Your winch should be capable of at least this much load. This will make the cable your weakest link but likely that's where it should be. (Any sailors out there disagree with my guess. I'm a land lover and likely always will be.) Once this has been identified, talk to your marine supplier. I'm certain that they'll help with your selection.

Hi Redfred,

the winch cable should not normally be the weakest link. Those sounder fish are expensive and they will not want to be losing them very often. They probably have a weak link at the bottom of the line that will part in the event that the fish snags on a wreck or other obstacle. It is better t lose the fish than the fish and the derrick or boom.

regards

Chas

My lure of being a dummy land lover worked.

This guy needs all the help he can get. I know when I'm out of my element and this is likely one of them.

But by knowing the tensile strength of the cable, one can now plan for the maximum tension on that cable. So would you say the winch should be capable of 75% of the cable tensile strength or would that be to close to the maximum?

Can you post a few photos of the system?

Can an inboard site for the winch be found with turning blocks to lead the line to the arm?

Have you considered changing to a hydraulic or pneumatic system? These are inherently IP68 and the motor/pump can be put where ever is convenient, ther may already be a suitable service aboard.

A piece of advice passed to me by an older colleague many years ago was "never try to do the client a favour, it will only turn around and bite you in the backside!" and believe me I've forgotten it often enough only to be reminded when things didn't go as expected.

This boat is going to lose a load of money if they cannot carry out their scanning for want of a good sounder winch, probably more per day than the cost of a new system.

Where are you? Only interested because my son is involved in a project like this, sailing off of east Africa at this moment.

DC motors have their specific futures that is adapted to certain application and uses.

If the process requires a constant torque and level speed without slip, then leave the DC motor and work to repair or rewound it.

AC motors could be simple to service and repair but considering its slip on load, it will be a disappointment on a lucky day of big fish catch.

The winch must have been made to adapt to the motor for same purpose as said in paragraph 2 above. U must also note that those that manufactured the ship are different from the those that installed or manufactured the winch so its either the winch is a standard for such ships base on the expected fish catch or it is necessary and any type of winch can be installed. If any winch can be installed/used and U have viewed all options including cost of making such changes and availability of power to with stand Ur intended AC motor, Ur free to continue if it pleases U.

Dickson

I would just like to reiterate what I said earlier. These winches have been put into an environment that is too harsh for them. I would like to see a more robust system put into place, being realistic it will not happen. I picked up one the motors and gearbox today am I would say it weighs about 8 kilo's at most,far to small for the job. the chain and sprockets are in good order. I don't like the construction of the winch. wait for it,its held together by uni strut sections. It really frustrates me to see people put into a position by companies who buy equipment without any knowledge then expects them to fix the problem. new motors have been fitted today,lets see how long they last. the last ones lasted less than a year. I will keep you posted

Just check up the motor class -it is seaworthy (ie the necessary class for salt water environment)

The whole winch is not sealed correctly.it's a total mess to be honest.there is no make on the motors,I honestly believe it's from a car winch.the slip rings look as if they have been made with no thought what so ever,not like trolex or other well known companies.unfortunately this is the realality of the offshore industry,held together by duct tape and tyraps.I will soon know how they get on,the ship has sailed today and I will find out.

As the Kinks said in their hit Low Budget "...But best of all cheap is cheap"

You get what you pay for.

You must first check if there is AC on board.

Ships usually are just equipped with DC, not AC.

Might be helpful to directly contact a manufacturer -- Baldor, for example, helped me with a project several years ago.

http://www.baldor.com/