12V "4.8HP" Amazon winch motor LRW0015 review & specs

Thread Starter

strantor

Joined Oct 3, 2010
5,591
Before I get started let me say this post is dual purpose.
1. I need to vent.
2. I'm trying provide helpful data for anyone considering the LRW0015 Ramsey Winch Motor for their project.
If you're interested in listening to me whine about Amazon, start reading now. If you came across this post in search for data on this motor, skip down to the part where I start quoting myself.

Venting:
I purchased this motor for use in a project and wrote a review for it which was/is IMHO one of the most helpful reviews ever written, but Amazon refuses to publish it. Within an hour of my first attempt they sent me an email stating the following:
Thanks for submitting a customer review on Amazon. Your review could not be posted to the website in its current form. While we appreciate your time and comments, reviews must adhere to the following guidelines:
http://www.amazon.com/review-guidelines

[...]

We encourage you to revise your review and submit it again. A few common issues to keep in mind:

  • Your review should focus on specific features of the product and your experience with it. Feedback on the seller or your shipment experience should be provided at www.amazon.com/feedback.
  • We do not allow profane or obscene content. This applies to adult products too.
  • Advertisements, promotional material or repeated posts that make the same point excessively are considered spam.
  • Please do not include URLs external to Amazon or personally identifiable content in your review.
I read through their guidelines and the only thing I came up with was that I had been critical of the negligent manner in which the seller had packaged it for shipment. Apparently they want you to focus your review on the product itself, and file your packaging/shipping complaints through a different channel that the public doesn't get the benefit of seeing. Well screw that. The seller, and the level of effort they put into getting your goods to you undamaged, is half the equation. I wasn't about to sterilize my review and have it say nothing at all about the absolutely pitiful work they did which led to me receiving a damaged product. So I removed all the words I had typed about the shipping but kept the pictures. I put in a little one-liner about them using weak studs which bent before I had a chance to use them. I submitted that revised review over a week ago and it still hasn't been published, nor have I received any subsequent rejection email. They're just not going to post it, they're not going to tell me why, and they're not going to give me an opportunity to plead my case. It really irks me because I spent nearly $100 for the opportunity get my hands on this motor and an appreciable amount of what I consider to be valuable time to measure, record, and compile all this data for the benefit of others, and I'm 90% sure the only reason they won't approve it is because it's TL;DR for their lazy moderators and has too many technical words.

So without further ado, here's REV2 of my review (and I'll attach all the same images I submitted)

Specs on these motors are scarce. Makes it hard for a guy or gal looking to use one for something other than a direct replacement for a winch motor. I took a chance on this one given only 3 parameters: 12V, 4.8hp, 2100rpm. Mine came with what appears to be a bench dyno test card(*), which I've included in my review, plus I took some electrical measurements of my own and did some math to fill in the blanks. Hopefully this electrical data plus all the dimensions I measured helps someone. It sure would have helped me. The seller could have posted this info but didn't, and that accounts for a 1 star reduction. The other star is deducted because they used weak flange studs which were bent over. No further comment on that, pictures are attached.

(*) there is no description of the test conditions so I don't know if the test is of peak efficiency or peak power.

PART A : ELECTRICAL

From the test card:
Volts: 12V
No load amps: 48A
Load current: 125A
Torque: 6NM (4.5 ft-lb)
RPM: 2185 RPM
Power (electrical): 1.5kW (2HP) (*)
(*) I ordered the motor fully expecting the advertised 4.8 HP to be grossly exaggerated. 1-2HP is what I was realistically expecting from it. 2HP peak power I would believe. 4.8HP I do not. I suspect the test card describes a peak power test, not a peak efficiency test.

My test results:
Total Series Winding resistance: 24.8mOhm (*1)
No-load RPM: 7,000RPM [8,700RPM] (*2,3)
No-load amps: 40A [35A] (*3,4)
Peak startup current (no load): 108A (*4)
(*1) measured with 4-wire Kelvin milliohmmeter
(*2) measured with positive contact handheld tachometer.
(*3) Series wound motors with no load will theoretically never stop accelerating until their speed is infinite. Practically, they will accelerate until brush & bearing drag cause a plateau, or until catastrophic bearing or rotor failure. I stopped my no-load test after 10s to prevent shrapnel death. The first number is obtained after 1 second and the 2nd number in brackets [ ] is obtained after 10s. If I had continued The test, I probably would have gotten even lower amps and higher speed. The 2100 RPM no-load spec in the product description is bogus.
(*4) measured with Fluke 376 clamp meter set to peak capture & in rush capture

My calculated values based on the test card & my measurements:
Electrical power: 125A × 12V = 1,500W [2HP]
Mechanical power: (6NM × 2185RPM) / 9.5488 = 1,371W [1.84HP]
Efficiency: 1,371W(m) / 1,500W(e) = 91.4%(*)
Locked rotor amps: 12V / .0248Ohms = 484A
(*) This efficiency number seems too good to be true. 91.4% is what I would expect from a cheap BLDC or a well designed induction motor. For this ultra cheap brushed motor I would expect 75%-80% efficiency. Maybe 85% under the right conditions. But this number calls the validity of the entire test card into question in my mind. I wish I had my own bench dyno to put it through its paces and tease some real verified numbers out of it. I plan to build one, and if/when I do, I will come back and update this review.

PART B : MECHANICAL

Dimensions taken with 12" digital caliper.
Shaft dia: .748"
Shaft length: 1.89"
Shaft height from flange: 1.75"
Woodruff key width: .185" (3/16")
Woodruff key depth: .225"
Flange dia: 3.00"
Flange depth: .232"
Bolt circle dia: 4.00"
Motor housing width: 4.49"
Widest part of motor (flange tabs outside-outside): 5.27"
Flange bolt hole size: 3/8"-24NF
Flange bolt hole depth: .670"
Overall length: 9.79"
# of brushes: 4 (cannot open without fear of destruction. Very tight. Probably loctited).
Electrical connection stud thread: 5/16-24NF
Electrical connection stud lenth: .98"
Ground bolts (2): 1/4"-20 X .25"
For the record, here's the deleted scene from REV1:

. The other star is deducted for their negligence in packaging it for shipment. They put the motor still in the cheezy box it shipped in from China, inside a much larger Amazon box with a single scrap of packing paper. Mine arrived looking trampled by horse. And then a gorilla. Twice. Motor was banged up and the flange studs were bent over. Luckily I don't need those studs and hopefully I can get the bent ones out without cracking the cast housing.
Pics, unboxing:
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