20V drill to hoist dinghy?

[exMaggieDrum]

The Milwaukee 28v right angle drill is a workhorse and would do the job. It is heavy and bulky though.



One issue is how high to the top of your davit you need to have the dinghy to. Pulleys will definitely help but regardless of the purchase you get, the pulleys themselves can only pull the load up to the combined height of the pulleys when pulled together. That was a real problem hauling my outboard up and I had to go with low profile smaller (but high load capacity, high quality) pulleys and a smaller but strong line.

[mvweebles]

Originally Posted by betwys1

Here are some numbers: 300lb = 136.4 kg so the boat weighs 1337 newtons
Say you need to lift the boat 80 inches = 2 meters. energy required is m.g.h = 1337 X 2 = 2674 joules.
The drill you pointed to is specified as 1.5 A.hr at 20V that's 108000 joules so neglecting inefficiencies and losses that's 20 lifts and 20 drops per battery charge which is OK Trouble is the max torque specified is 28N.m for the drill, so if it turned a 4 inch diameter spool winch that's just 28N / 00.05m = 560 newtons MAXIMUM no losses so you need blocks to get about X6 advantage or better. That's a lot of line flapping around. I have a Harbor Freight (!!) hand winch which is a wormwheel and pinion 1 ton affair. If you used a gear like THAT, you would be in business! A worm gear is self-locking by the way - so you could pull the drill off the winch and the boat would stay put. Hope this helps. (P.S Don't even think about an impact drill - the high torque specified exists for couple of milliseconds per second - good for wheel nuts - bad for winches.

Yikes! This takes me way back to some tragic story-book math experiences in school

So lifting 300 lbs is 1334 Newtons of force. The drill has load-limit of 560? An Andersen 14 winch is rated at 10:1 mechanical advantage. Am I correct that means the effective pull is 133.4 Newtons, or roughly 30% of the rated capacity?

Jeez, I knew I should have sat in the front row back on physics....

[mvweebles]

The issue I have with the Milwaukee 28v it would be an orphan on my boat tool - I have a trawler and don't have need for this tool (you Sailors have many applications such as hoisting a person up the mast, sheets, etc) . I switched from Milwaukee NiCad 18v to Dewalt 20v LiOn several years ago. The 28v Milwaukee is designed as the cordless alternative to the legendary hole-hog for plumbers to use 4-inch hole saws through 2-by wood joists which is about as beefy as work gets in residential construction (more than a few hands have been obliterated by a hole-hog that suddenly grabs).

Looks like DeWalt has a 60v drill that competes with the Milwaukee. It uses a dual use battery that I could at least use in the rest of my tools. When I get to the final install, I'll see how the DeWalt does and make a decision from there - if my existing drill works okay, will get the smaller right angle drill for leverage and ease of use

[Steve Whelan]

If you've ever tried mixing a 5 gallon pale of paint with a Dewalt drill and a paddle you know the drill will burn out quick and then you're "Screwed" (get it). Which will leave you without the drill for other work as well as hoisting the dinghy.

[mvweebles]

Originally Posted by Steve Whelan

If you've ever tried mixing a 5 gallon pale of paint with a Dewalt drill and a paddle you know the drill will burn out quick and then you're "Screwed" (get it). Which will leave you without the drill for other work as well as hoisting the dinghy.

Hmmm.... This past summer I mixed about a dozen 60-lb sacks of mortar mix for outdoor stepping stones with a dewalt 20v cordless. I alternated batteries but could easily get a sack and a half out of a single charge. Not as productive as the very heavy duty mortar mixer I have at home, but it's all I had and worked pretty well. No damage whatsoever.

Are we talking the same DeWalt 20v drill?

[betwys1]

Originally Posted by mvweebles

Yikes! This takes me way back to some tragic story-book math experiences in school

So lifting 300 lbs is 1334 Newtons of force. The drill has load-limit of 560? An Andersen 14 winch is rated at 10:1 mechanical advantage. Am I correct that means the effective pull is 133.4 Newtons, or roughly 30% of the rated capacity?

Jeez, I knew I should have sat in the front row back on physics....

*******************
You supplied the missing link. I could see that the drill mentioned could do the job at a suitable gearing but I was hazy on the gearing used on a typical winch. 10:1 sounds useful!
I still don't know the spool diameter of the winch you have in mind, which is needed to give you a solid answer. The drill is specified at a peak torque of 28N.m for the drill, so if it turned a 4 inch diameter spool winch with a 10:1 gear that's 28N X 10 / 00.05m = 5600 newtons force which represents a lift of about 560 kg or 1232 lbs PEAK no losses. Given losses and all, you would be good for better than 616 lbs with a comfort factor....I forget the speeds that the two speed 20V drill offers, was it something like 300 rpm or 1200 rpm? - call it S rpm ~ so that leads to the speed that the boat lifts. S rpm X 2*pi*radius of winch spool in inches /(10X 60) gives inches per second lift rate ~ example 300 rpm drill , 4 in diameter winch spool gives six inches per second lift or 12 seconds to rise six feet - that's a little fast!...... /end

[le chat beaute]

I have used the 28 V Milwaukie 1/2 right angle drill to hoist main and dinghy for over 10 years. I purchased on line the ultimate crank winch attachment. Would not leave the dock without it. I can be hoisted to the masthead three times on a charge. Just pulling Caine 11.5 with 15 Yamaha attached can do so for 7-10 days without recharging. Downside, batteries are expensive so important to store correctly during lay up periods. 2 batteries and winch adapter in for less than 400$usd. Half the cost of the winch mate system

[Ken Fry]

Originally Posted by mvweebles

I'm really interested to see if the newer 20v LiOn drills are strong enough - I'm looking at an Anderson 12ST which gives a 10:1 mechanical advantage. Compared to my old Milwaukee 18v NiCad, newer Dewalt is a powerhouse. I'm pretty sure it will be plenty, but won't know for a few months. Will probably need a right angle drill.

Cool!

I like the idea of a nice looking, reliable, durable winch on which replacing the line is so simple as to require virtually no thought. This in comparison to the standard trailer winch, which has stainless wire rope, which is no fun to work with, especially once it starts to form ham hooks. And they're ugly.

The Anderson 12 st has a gear ratio of 1.3:1. Its "Power Ratio" ( a physics misnomer.... but a standard neverthess) on the other hand, is calculated with a 10 inch winch handle. The winch drum radius is 1.375". So: 10/1.375*1.3 = 9.45. That means that if you pulled on the 10 inch handle with 20 lb force, you would see a little under 200 lb on the load side.

But: You are trying to use something other than a winch handle, so, to produce a line tension of say 100 lb, you need a certain torque capability from the drill. The torque required to produce 100 lbs is 100*1.375, so 138 inch pounds.* The torque capability of the drill might be specified in foot lbs, and in this case, that figure would be 11.5. My Milwaukee produces "up to 150 inch pounds of torque" so a drill like it would create a line pull of 100 lbs... barely. (we engineering types add in the effects of friction, etc --- we are a gloomy bunch.) SO, how do you get the line tension to less that 100?

Answer: A 4:1 tackle, which is probably what you have in mind already. One rope going over a davit pulley and down to the bow, then back up, then horizontally to the stern davit pulley, and down and back up, gives you 4:1 advantage. (You'd have pulleys with snap shackles at the points where the bow and stern connections to the dinghy are made.)

The reaction at the drill would be 11.5 ft lbs, so if the distance to the center of your hand from the chuck center is 8", then you will have to hold with a force of 17.5 lb : easy peasy.

A standard configuration drill would make this more difficult, but not impossible. On a boat, having a good right angle drill can be pretty handy. They can fit in places where a standard drill will not.

NEVER use an impact drill of any sort to do this. As I suspect others have said, these work with a series of very brief, but destructive-to-gears impulses.)

Disclaimers:
1. Check my math.
2. How will you get the dinghy down? You'll want to experiment a little, so you don't lose control of the line when "easing" (we say in the sailing world -- but perhaps you also sail?) (Maybe a light load at first, and keep the dinghy low for the first few up-down cycles .
3. If the line is rigged as I described, there is nothing to ensure that the dinghy comes up level. The bow and stern forces would need to be equal.
4. The rigging I've described requires that the davits cannot swing inward under the pull of the horizontal segment.
5. Use line that has a standard polyester cover (and whatever core you want) Exposed Dyneema is too slippery for winch use.
6. Re slipperiness, Google capstan ratio. You will want three turns on the winch when you ease the boat down, more for slippery rope, less for not-so-slippery rope.
7. Consider the tension in the horizontal part of the line and the resulting torque on the davit arms. Whatever is keeping them from swinging in has to deal with that torque.


* This really should be pound-inches, but I've given up on this. In the English system, a foot-pound is a measure of work, and a pound-foot is a measure of torque. Re: Power Ratio; The "power" (measured in HP or kW) going into the which is exactly the same a the power coming out, unless the winch and rope are heating up. OK, enough on the language purity thing.

[Ken Fry]

Originally Posted by Ken Fry

Answer: A 4:1 tackle, which is probably what you have in mind already. One rope going over a davit pulley and down to the bow, then back up, then horizontally to the stern davit pulley, and down and back up, gives you 4:1 advantage. (You'd have pulleys with snap shackles at the points where the bow and stern connections to the dinghy are made.)

Are you thinking of a single davit? Then some of what I said is not applicable. With say 2:1 purchase on a single davit, the drill would have to produce twice the torque, (not impossible... but more expensive and heavier). A 4:1 tackle at one lifting point, would work fine.

[Ken Fry]

More disclaimers: the capstan formula might lead to two turns for a not-so-slippery rope, but stick with 3. In your application, there is no advantage to fewer turns. when racing, sailors will sometimes user fewer turns in light air, (or ditch the winch altogether) so easing is easier or more sensitive.

[mvweebles]

Originally Posted by Ken Fry

Cool!

I like the idea of a nice looking, reliable, durable winch on which replacing the line is so simple as to require virtually no thought. This in comparison to the standard trailer winch, which has stainless wire rope, which is no fun to work with, especially once it starts to form ham hooks. And they're ugly.

The Anderson 12 st has a gear ratio of 1.3:1. Its "Power Ratio" ( a physics misnomer.... but a standard neverthess) on the other hand, is calculated with a 10 inch winch handle. The winch drum radius is 1.375". So: 10/1.375*1.3 = 9.45. That means that if you pulled on the 10 inch handle with 20 lb force, you would see a little under 200 lb on the load side.

But: You are trying to use something other than a winch handle, so, to produce a line tension of say 100 lb, you need a certain torque capability from the drill. The torque required to produce 100 lbs is 100*1.375, so 138 inch pounds.* The torque capability of the drill might be specified in foot lbs, and in this case, that figure would be 11.5. My Milwaukee produces "up to 150 inch pounds of torque" so a drill like it would create a line pull of 100 lbs... barely. (we engineering types add in the effects of friction, etc --- we are a gloomy bunch.) SO, how do you get the line tension to less that 100?

Answer: A 4:1 tackle, which is probably what you have in mind already. One rope going over a davit pulley and down to the bow, then back up, then horizontally to the stern davit pulley, and down and back up, gives you 4:1 advantage. (You'd have pulleys with snap shackles at the points where the bow and stern connections to the dinghy are made.)

The reaction at the drill would be 11.5 ft lbs, so if the distance to the center of your hand from the chuck center is 8", then you will have to hold with a force of 17.5 lb : easy peasy.

A standard configuration drill would make this more difficult, but not impossible. On a boat, having a good right angle drill can be pretty handy. They can fit in places where a standard drill will not.

NEVER use an impact drill of any sort to do this. As I suspect others have said, these work with a series of very brief, but destructive-to-gears impulses.)

Disclaimers:
1. Check my math.
2. How will you get the dinghy down? You'll want to experiment a little, so you don't lose control of the line when "easing" (we say in the sailing world -- but perhaps you also sail?) (Maybe a light load at first, and keep the dinghy low for the first few up-down cycles .
3. If the line is rigged as I described, there is nothing to ensure that the dinghy comes up level. The bow and stern forces would need to be equal.
4. The rigging I've described requires that the davits cannot swing inward under the pull of the horizontal segment.
5. Use line that has a standard polyester cover (and whatever core you want) Exposed Dyneema is too slippery for winch use.
6. Re slipperiness, Google capstan ratio. You will want three turns on the winch when you ease the boat down, more for slippery rope, less for not-so-slippery rope.
7. Consider the tension in the horizontal part of the line and the resulting torque on the davit arms. Whatever is keeping them from swinging in has to deal with that torque.


* This really should be pound-inches, but I've given up on this. In the English system, a foot-pound is a measure of work, and a pound-foot is a measure of torque. Re: Power Ratio; The "power" (measured in HP or kW) going into the which is exactly the same a the power coming out, unless the winch and rope are heating up. OK, enough on the language purity thing.

Thanks for this. I tried to figure it out online but just couldn't find something that made sense to me. Really good point about the winch handle being included in the calculation.

According to site below (which is unapologetic about the difficulty in determining torque), the DeWalt brushless drill has 630 in lbs of torque. If your math is correct and the torque values accurate, means about 500 lbs of lift, though there will be frictional losses.

I didn't mention in my original post, but I plan a rope clutch as a safer stop gap. I thought about a cam cleat but decided the reliable clutch would be better even if there is more frictional loss.

Powerboats often lift their dinghy from a single lift point via a custom 3-point cable bridle. The dinghy's painter is used to steady it as its lifted. To lower the dingy, would simply belay it down using the winch.

I guess that if my drill is not beefy enough, I have a few options. I can replace with a beefier one (Milwaukee 28 or DeWalt 60v); get a winch with more mechanical advantage (Andersen makes the same winch with an 18:1 advantage); or double the pull by running the lifting part through a sheave that attaches to the lifting bridle, then dead ends back at the davit end.

I too like the simplicity of this arrangement. Will last a lifetime and no electrical connections. We powerboaters can learn a thing or two from Sailors '

https://toolguyd.com/dewalt-cordless-drills-uwo-torque/

[Ken Fry]

Originally Posted by betwys1

*******************
You supplied the missing link. I could see that the drill mentioned could do the job at a suitable gearing but I was hazy on the gearing used on a typical winch. 10:1 sounds useful!
/end

Sailboat winches use a thing called "Power ratio" which is useful, but confusing for physics types. The gear ratio in the Anderson winch is actually 1.3:1. The power ratio is figured by including the effect of a 10 inch handle turning a drum with 1.375 inch radius.

There are "two speed"winches that change gear ratio depending upon which way one turns the handle. The drum rotation direction remains the same in either speed, even though the handle rotation direction has changed. A non sailor might say "what the heck is wrong with this winch!!!??? I cranked it in, then tried to crank it back out, and it just kept cranking in further!!!"

There is no clear explanation in science for how strange this sailing stuff is. It is believed that it has something to do with offending the wind gods.

[Ken Fry]

Originally Posted by mvweebles

According to site below (which is unapologetic about the difficulty in determining torque), the DeWalt brushless drill has 630 in lbs of torque. If your math is correct and the torque values accurate, means about 500 lbs of lift, though there will be frictional losses.

https://toolguyd.com/dewalt-cordless-drills-uwo-torque/

Torque should not be difficult to specify, and many drill manufacturers specify it clearly. However, it can be determined indirectly from UWO. But every manufacturer knows the actual torque value, and most will provide it, but by the time things get to marketing, stuff can be left out.

You can measure torque of a drill yourself. Affix a board that provides a foot or two (for convenience) lever from the chuck. Use a fishing (etc) spring scale to measure the force 1 foot out. If the force is off scale (too high) then us a longer board, etc.

UWO is not intended to obfuscate things, (I suppose) but it can work that way. Some drills have two speed gear boxes. The internal ratios might be 10:1 and 20:1. Ignoring differences in losses (probably higher for the higher ratio) the "Power" (how fast, how hard) is the same: you trade torque for speed.

Two different manufactures might make otherwise identical drills, but one has a 20:1 gearbox, and one has a 10:0. A person could, looking only at torque, that the first is twice as "good" as the second. However, someone concerned more for the ability to drill small holes fast, will find the less torquey faster drill better. Both could be advertised with the same UWO number, possibly implying that they are more similar than the really are.

In your application, you want plenty of torque, and it could be that of those two identical UWO drills one cannot lift the dinghy, and the other can. If you purchased the one that cannot, all is not lost, because you could compensate with double the purchase on the tackle. But you'd need more rope and more pulleys.

A spec like "produces 500 in.lb at 1000 rpm" tells the story a little more clearly. The other drill, in this case, might say "produces 250 in.lb at 2000 rpm." They have the same electrics, and the same "power"

(Knowing torque and rpm, you can calculate HP (or watts). Knowing watts, and the watt hour capability of the battery , you could know how long the battery will last. This last calculation is fuzzy, because the battery capacity actually changes with load. But for your application this drill would lift the boat several times between charges, no doubt.

630 in.lb is pretty impressive. You'd want to hold on tight. A handle sticking out the side would be a good thing.

[Jim Cate]

Sailboat winches use a thing called "Power ratio" which is useful, but confusing for physics types.

In addition, some winch mfgs (Barient and Barlow for example) use a different nomenclature. Their size numbers are (allegedly) the actual line tension generated when a force of 100 pounds is applied to a standard 10 inch handle, that number divided by 10.

That is for example in our Barient 32 primary winches, if you applied 100 lbs force on the handle, it would exert 3200 lbs tension in a sheet. This supposedly includes frictional losses in a new, well lubed winch on the factory floor. Losses would likely be greater in typical usage. IMO it was a good system, but confusing when intermixed with the "power rating" of other marques.

Jim

[Ken Fry]

I've been poking around looking at availability of drill specs, partly to be helpful, partly for amusement, but also, it turns out, for application to my own project. Time well spent.

One of the Dewalt models is 820 UWO. That is a little over one hp, a rather large amount from a hand held drill.

Possible?

Apparently. The battery for this one can be 5AH x 20 V = 100 Watt hours. In round terms, the battery would last for about 1/8 hour at this 820 watt output. The discharge rate would be called 8C, meaning 8 times the AH value of the battery. That is possible with the LI batteries in portable tools*. In fact, it is one reason that these same batteries are used in huge numbers in the Teslas: discharging a battery fast means high power delivery, desirable in a fast car and in a power tool.

HP = torque x rpm /5252. So, if one gear ratio provides a maximum speed in this drill of 350 rpm, then its torque at that speed will be 15 lb ft, (180 in lb) assuming 1 hp.
Each turn of the winch reels in about 8 inches of rope, and at 4:1 tackle, will lift the boat 2 inches. So 4' would require 24 revolutions -- a small part of a minute.

So it all seems pretty feasible, and the battery could do quite a few lifts per charge.

In my own boat building project, I drive a different sort of winch with a drill, and have been prototyping with my old Milwaukee shop drill. I have planned all along to used a hand crank for part of this longish operation (40 turns of the crank yields one turn of the drum) and then use a drill for the last part where the leverages work out better. But a drill like the Dewalt might save me some exercise... which could be either good or bad.

Good luck with this project!

* Marine LiFePo batteries are more apt to have maximum discharge rates of 3C or 5C.