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Discussion Starter #1
Hi everybody.
On my sailboat I have a diesel engine that is kaput and a prop shaft awaiting something to spin it. I'm on a small budget and so I'm going with what I can and not with the full meal deal optimal.
Ultimately I'd like to push the sailboat for as much as 3 hours but I prefer to sail and use the tide tables to tell me when the tide is in my favor and so initially I'm expecting I'll only need the motor for a few minutes here and there. When I can afford to bump up the battery bank I will. Until then I'll have to cobble together what I can.
I have about $1000 USD to work with.
I'm looking forward to doing this install. My first challenge is finding a motor. They seem a lot more challenging to find used than I expected.
Any thoughts?

All the best,

Mike
 

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Well...forklift motor is the way to go probably... relatively low rpm, 48volt.

48 volt controllers are very affordable, 48 battery: you can use lots of different types of lithium car batteries. but you can also start with 4 12v lead-acid batteries to try things out and upgrade later.

charger: telecom power supply, usually cheap second hand.
 

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What kind of RPM do you need?

How would you be connecting it mechanically?

Used forklift motors are around $200 from a forklift repair yard (worth about that in scrap). They'll sustain 15-30hp easy. More if you find an effective way to cool them. In boat duty you're not getting the easy coasting you would on a car (water is harder to push out of the way than air). In car use it's normal to spike the motors to high dozens or low hundred horsepower worth of use when accelerating, but then drop back down to travel at speed. You won't ever drop down so you have to be more conservative. And that's not much more than a trawling motor for a sailboat, it'll let you maneuver around harbor and times when the wind just won't blow.

The forklift will have a 36 or 48v controller onboard, see if you can nab that too. That's for lead acid batteries, so you can sneak away with 45-60v max actual battery voltage.

$800 in batteries might get you most of a Chevy Volt pack. Maybe 10-ish kwh, which is 10kw (probably what you'd run your motor at, ~13hp) for 1 hour. About the right range. $1500 would mean you won't have to be so thrifty when parts shopping.

It's close to being able to do what you need. Gas is a lot cheaper.
 

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Discussion Starter #5
I guess I'd connect it by making a custom bracket to mount to the original motor mount area and connecting it to the original prop shaft via a coupling. RPMs should be in the 2-3000 range for cruising speeds from what I've read about original diesels. Do the controllers allow a good range efficiently? I'm more than happy to cruise slowly if it means extending battery life significantly. I did a conversion on a smaller boat about 5 years ago. I basically used all free parts and installed a .5 HP shop scooter motor direct drive to the shaft running at 24v. It was quite slow and I'd say under powered add it pushed her at 2 mph but then at max hull speed of 6-7 miles per hour a 30'sailboat won't go fast no matter how much power you pour at them.

I'm curious about where I might find a reliable forklift motor. They just don't seem to come up on the searches here in Canada.
 

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Hi
If you are happy with hull speed then you don't need much power a kilowatt or so would probably be enough

Forklift motors -you won't find them because nobody buys them! - catch 22

You need to find out who locally repairs forklifts - and then VISIT them - you won't get anywhere with phone calls and email

Forklifts die because the batteries fail and are too expensive - and then the controller dies
The motors just keep running

The guy on the phone may not know (or care) but the actual technician may have a spare kept "just in case" - you need cash and beer to prise it from him

If you can't find somewhere then drop in on any big food or furniture warehouse - some will use gas powered forklift but if it's essential that the goods be CLEAN then they will use electric - ask them who looks after their forklifts

You may need to speak to a number of people before you find paydirt

Here most dead electric forklifts end up with a nice old guy called Graham who is quite willing to sell then for $200 each

Try and find one locally - they are heavy! - a car needs a 9 inch or bigger 60 kg
you don't need such a big one but if you get offered one just grab it

Read the thread on choosing a forklift motor!

https://www.diyelectriccar.com/forums/showthread.php/using-forklift-motor-and-choosing-good-7598p241.html

This one - from that thread - is too small for a car but may be big enough for your boat

https://www.ebay.com/itm/REBUILT-FORKLIFT-WARFIELD-ELECTRIC-DC-MOTOR-CM16/401576542492?hash=item5d7fd3c11c

If you do find your forklift breakers then you may try and get a controller as well as the motor
 

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If you do find your forklift breakers then you may try and get a controller as well as the motor
I think this is an important point: most people in this forum buying forklift motors intend to run them at much higher voltage than they were in the forklift, so the original controller is not usable. In this case, if the stock power output is suitable then the original voltage would work and so all of the motor controls (controller, contactors, etc) could be usable.
 

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Assuming you want to be able to motor into the wind / waves, for a 30ft sailboat I'd say aim at 10kW of power, unless your always in a protected area without potentially dangerous stretches.

If you find a forklift, even when you cannot use the controller, at least take all the thick wiring and contacters, that will safe you a lot of money and work when you can re-use it.

Forklift controllers are not always easely re-usable.

For one boat project I was able to buy a defective forklift (controller dead) with a good battery, used battery, motors, contacters, wiring.

Mounted Kelly controller, this one died after a week, then used an Alltrax controller...1,5 years of use...then the Kelly controller sent to me after first one died and that one is still in use 5 years later.
 

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Discussion Starter #9
Man! You guys are a huge help. Starting to get my head around this now. I've discovered a few forklift repair places around here now so I'm going to go out next week and see what I can find.
Question: Gear reducing. To my mind if the controller will keep the main shaft spinning within the desired RPM range is there any reason not to do a direct drive?
I've read somewhere that a thrust bearing might be a good idea although I haven't figured out what a thrust bearing is or looks like yet.
Definitely appreciate the comments thus far. Things are beginning to make more sense to me.

All the best,

Mike
 

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I've read somewhere that a thrust bearing might be a good idea although I haven't figured out what a thrust bearing is or looks like yet.


https://en.wikipedia.org/wiki/Thrust_bearing

Imagine a shaft. Now imagine trying to bend that shaft into a bow shape, by pushing on it sideways the way you'd snap a pencil. That type of perpendicular force is what normal roller bearings are designed to handle. Not that type.

Imagine instead the same shaft, but that you're using as a gigantic nail and you're hammering on the end of it. Or pretend it's a spear you're trying to stab someone with. A thrust bearing is designed to handle that kind of load. If you used a roller bearing, it would work a little bit but it would get ruined quickly because it's not strong in that direction like a thrust bearing is.

In wheeled EV, there is resistance to turning, but everything else is pretty much locked in place. The rear axle is supported and bolted in place. You move the car forward by turning the shaft.

In a boat, the propeller is pushing the boat directly. Think of using a pole to shove the whole boat forward. Or a spear. That's the load that's on the shaft there. If there was no bearing at all, the propeller shaft and the inside of the motor would push right out like a pool cue through someone's fingers. It doesn't, so, something is stopping it from doing that. You want the thing that's stopping it from doing that to be the thrust bearing, not metal grinding on metal at the end of the motor housing, not a roller bearing being shoved sideways, etc.

It will depend on what's already there. Typically either the end of the shaft or a wider part of the shaft will have the thrust bearing. Something to constrain the stabbing (or "thrusting", if you will, hence the term) motion. If that used to be the engine itself, and the engine's output had a thrust bearing, you'll need something new that does the same.

Generally motors don't have much if anything to handle thrust. Maybe just a wavy spring washer at the ends of the case to float the shaft properly, but they'll be shredded right quick by a thrust load.
 

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...

Generally motors don't have much if anything to handle thrust. Maybe just a wavy spring washer at the ends of the case to float the shaft properly, but they'll be shredded right quick by a thrust load.
Here you go again. Posting BS like you knew what you're talking about. Your quoted statement is totally wrong. Fork lift propulsion motors and gearboxes are designed to handle end thrust from helical spur gears as well as some bevel spiral gear sets. I've asked you before to check out facts. But you still take the easy way and post what you don't know, instead of researching and learning what you really don't know.

And it is obvious that you don't know why wave, Belleville, or spring washers are used, so made up BS about that also.

Regards,

major
 

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Major, you have way too much hatred in your life.

Relax man, go have a beer or something.

Not every conversation requires such viciousness and venomocity.
 

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Discussion Starter #13
Excellent description and explanation thanks.
Any thoughts on whether the controller will make direct drive doable? I'm looking for 2-3000 RPM to the shaft.
 

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Hi
This depends on the size of your prop - the available motor power will be declining if you are using 48 v and a forklift controller

From my experience you would need about 100 v to get your max current at 3000 rpm

How much power did the diesel produce? - and what revs would it drive the prop at?

As a general rule a larger prop run slower is always more efficient than a smaller prop run faster
 

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Excellent description and explanation thanks.
Any thoughts on whether the controller will make direct drive doable? I'm looking for 2-3000 RPM to the shaft.
that's very fast, are you sure that number is correct? I'd say you need 1000-1500 rpm max.

How much thrust a motor can handle: look up the bearing specs, you'll probably want to replace the bearings anyway.

a good reason for installing a thrust bearing (usually just a deep groove ball bearing, or for bigger installations a self-aligning roller bearing), is when you want to use a coupling (like a lovejoy coupling), for ease of installation of the motor, and to handle small mis-alignment

you can see the couplings and the bearing block in this picture:
http://boekel.nu/foto/11/2011-04sloep/image71.htm
 

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Major, you have way too much hatred in your life.

Relax man, go have a beer or something.

Not every conversation requires such viciousness and venomocity.
May be you should learn that just because you can type something, doesn't necessarily make it true.

In this case, a look at most motors will show one bearing fixed in the end housing with a snap ring, a screwed down plate, etc. and the bearing at the other end of the motor floating in a housing, sometimes against a spring washer of some kind. This provides some thrust capability with the fixed bearing(like boekel says, you should check the bearing thrust capacity), and still allows the armature to expand and contract with thermal cycling. If both bearings were fixed, the thermal cycling could impose an unacceptably large thrust load on the bearings

In some lightweight motors, a lightly constructed end housing might limit the the thrust load.

Another consideration is if you want to drag the prop to turn the motor or a generator to produce power under sail. In this case, the thrust will be in the opposite direction. This would also inform the choice of motors types. A series motor would not be a good choice for this application.
 

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Discussion Starter #17
Thanks for keeping me pointed in the right direction guys. Yes. I looked up the specs on the diesel engine. Max RPM of 3600 and then a 2.25:1 gear reduction brings max revs to the prop shaft down to 1600.
Off hand I don't know the exact specs of the prop. I took a swim and looked at it and it was significantly larger than the original small one. The boat came originally with a 12 horse diesel but it's popular on these vessels to upgrade to 20-25 because they are wide (beamy) and so need more push to get through head seas.
Is there a general direct output rpm that forklift motors produce given at their spec battery bank? Are they generally 48 volts?
 

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Discussion Starter #18
Another consideration is if you want to drag the prop to turn the motor or a generator to produce power under sail. In this case, the thrust will be in the opposite direction. This would also inform the choice of motors types. A series motor would not be a good choice for this application.
I've been considering regeneration but I read somewhere that it works well for fast sailing. I rarely get enough way on to drive much of anything so I decided to deprioritize regeneration and focus more on solar. Thanks for your thoughts though.
 

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Discussion Starter #20
I called a few forklift repair shops today. One guy has 5 electric motors on the shelf. Said he can make me a good deal. I'm headed over there tomorrow, Tuesday, to have a look. Now I really have to get my head around this. Any tips on how to avoid a bad or worn motor? I'm going to look at some diagrams to familiarize myself with the workings of an electric motor. This looks like it's about to get real!
 
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