Electric drive motor specs

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Glenn Brooks
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Re: Electric drive motor specs

Post by Glenn Brooks »

As an update, below is a tractive effort calculator method for live steam equipment I found on line. Tom Artzberg wrote this for the Golden Gate Live Steamers at some point. Pretty simple to follow and well written. The author makes several key assumptions relevant to our miniature train scale and gauge. These assumptions (about tractive effort for riding scale equipment), relate to assessing appropriate tractive effort for our size locos.

https://www.goldengatels.org/library/To ... Effort.pdf

Using these formulas, I was able to calculate my center cab electric would exert 325# tractive effort, with 1,300# weight on drivers.

I would need two 24volt 7.5kw small forklift motors, one per truck, to pull an 8,000# consist - up a 2% grade and around 35’ radius curve. Pretty radical capacity! Flat track, (under 1% grade), wider curves >50’ Radius 15Kw (20hp) Power would theoretically pull in excess of 10,000# - 5 loaded cars, 40adult passengers!

Now these are old school, industrial, series wound motors, so should be very heavy duty. Might go with 12 or 15 hp motors if the shop will discount their OTC price some. Sounds like 20 KW power would be a massively impressive power train.
I have found a couple of surplus forklift motors that fit the bill at a local motor resales shop. The owner is holding them for me until I recheck my calcs and find the related controllers and throttle. Looking for a 500 amp controller if anyone has a spare hanging around...

BTW, I posted this link in my previous electric power primer thread, in case someone else wants to do similar background on EV outfitting.

Pretty exciting to think this poor little yard goat could actually become a real workhorse!

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....
Glenn Brooks
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Re: Electric drive motor specs

Post by Glenn Brooks »

BDD, Good to read your comments about rectangular tubing. I made a “short” 40’ scale ROW flat car last year with 1x3 rectangular tubing. The car scales out to 8’ x32”. Works real well, although I kind of overbuilt it a bit. So it is a lot heavier than it probably needs to be. The decking is old growth PNW clear grain fir salvaged from an old 1900’s house remodel in Seattle couple of years ago. I rabbited the edges, prototypical style, so the edges lock together once they affix to the frame. Extra work, but stronger and fun to look at when I walk by.

My interest was to replicate the original 1900-1920 steel car chassis construction method. The original design called for two additional intermediate sills, running full length. I decided sills every 6” was overkill, even for me, so left them out.

The tubing makes it a real workhorse. I loaded it with 3500# of cement block at one point, and couldn’t see any noticeable deflection.

Somebody mentioned one center sill and light laterals for passenger coaches. Think I will try that for my next coach build. Maybe use 2 ship channel, back to back, down the center. Easier to drill and attach stuff with bolts or rivets.

Glenn
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Moderator - Grand Scale Forum

Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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Steggy
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Re: Electric drive motor specs

Post by Steggy »

Glenn Brooks wrote: Thu Oct 15, 2020 1:20 pmSomebody mentioned one center sill and light laterals for passenger coaches. Think I will try that for my next coach build. Maybe use 2 ship channel, back to back, down the center. Easier to drill and attach stuff with bolts or rivets.
Ship-and-car channel tends to be on the heavy side for its bending strength. Rectangular tubing of the same width and height generally works out to about sixty percent of the weight of channel for the same load-bearing capacity. Also, mill finish on tubing is better.

As for attaching things, that's where the trusty old welder gets into the picture. :)

Speaking of pictures, here are a couple of the "backbone" for my F-unit's control car. The finished car takes advantage of the hollowness of the frame..wiring is routed through it.

F7 Control Car Bare Frame
F7 Control Car Bare Frame
F7 Control Car Bare Frame
F7 Control Car Bare Frame
F7 Control Car Bare Frame — Front End Sill
F7 Control Car Bare Frame — Front End Sill
F7 Control Car Bare Frame — Rear End Sill
F7 Control Car Bare Frame — Rear End Sill
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cbrew
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Re: Electric drive motor specs

Post by cbrew »

no way those motors will handle that much weight. you need to big
you need to be in this range of hardware https://www.thunderstruck-ev.com/index. ... HYQAvD_BwE
If it is not live steam. its not worth it.
tetramachine
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Re: Electric drive motor specs

Post by tetramachine »

This is an interesting project. My chair has two 600W 3/4HP motors. The chair weight is just short of 200, and I add 150. At full speed of 6mph, any grade slows me down. A grade of 1:6 is a crawl, (And the wheelie bars are in full use.)

Electronic speed controllers are great but at large amperage needed for a pair of 8kw or more motors, that could be real expensive. You could build a series/parallel controller. A forklift controller would be ideal when matched to the motors.

keep us posted.
My wheels don't slow me down
Glenn Brooks
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Re: Electric drive motor specs

Post by Glenn Brooks »

Hi Cbrew, yep, the motors I just sourced - haven’t bought yet- are the heavy gauge wire, industrial grade, series wound motors used as forklift traction motors. Quite a step up... They each pull about 200 amps. So looking at 400 amp draw total. The numbers for Tom Arbeztgers tractive effort formula work out ok with two of these, one per truck, totaling around 350# tractive effort, if the loco weighs 1500#, hauling a 5 car consist of 10,000#. But, that’s just the calculation... still doing background to learn more, as this is still all quite new to me.

In the shop, Bit of a set back today. I dropped the trucks for the first time and cut out all the old mounting brackets. I found the chassis and trucks are way to light to make this a decent passenger hauler. Mostly light guage 1 1/2” angle iron construction. Sturdy enuf as a back yard trolley, but way, way light and bendy for even pulling 2-3 loaded cars.

Here’s what one of the trucks looks like - solid construction, but light gauge angle for the side frames.
9CEA75EB-CD00-4933-8458-FF0DA053F3F0.jpeg
So taking a day to think over if it’s worth retrofitting frame members and building new trucks etc.

However the hood ends certainly have enuf room to mount a traction motor or two and carry batteries.

Tetramachine, i suspect these motors are similar to what you may have in your wheelchair. A local friend here In .Seattle gave these to me to try out. He is wheelchair bound now and has done a fair bit of wheelchair build and repair. I believe these are in the 500-600 watt range. In the photos they are just resting on the axles. Trying to figure out how to fit two side by side.
BDDE79D5-04F0-4E14-96B8-0413F255AA49.jpeg
4AE1261F-8D70-4A27-8881-8BE4AB5B6A7B.jpeg
My assessment now is the frame, as is, could easily take a couple of 1000watt MC traction motors, mounted vertically, and pull a MOW car, maybe a couple of passengers. But, as is, the loco is to lightly built to pull 10,000#. I do want to continue to learn and experiment with the EV approach, just not sure now, this is the best way to do that.


One big problem I foresee is how to mount the motors so they are free to move up and down with the axle as it moves in the journals and side frame. Maybe BDD’s method of using an idler arm and idler sprocket will work.

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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Steggy
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Re: Electric drive motor specs

Post by Steggy »

Glenn Brooks wrote: Fri Oct 16, 2020 11:16 pmOne big problem I foresee is how to mount the motors so they are free to move up and down with the axle as it moves in the journals and side frame. Maybe BDD’s method of using an idler arm and idler sprocket will work.
If it were me doing this and I were using wheelchair motors (which I wouldn't), I would mount the motors under the truck bolster, with the output shafts as close to the bolster as possible, and the centerline of the motors' output shafts as close to the same plane as the axles. Doing so will allow you to run a relatively long roller chain span with sufficient slack to accommodate vertical wheelset motion as the loco runs over uneven track. If you plan this right you will not need idlers. All you will need is a motor mount that allows some adjustment to get the chain slack where you need it.

The minimum roller chain size I recommend for this sort of application is ANSI 40, with sprockets having hardened teeth to achieve long life. Also, don't underestimate the amount of overhung load that will be applied to the traction motor on an ascending grade. Try to keep the sprockets as close to a wheel as possible so axle deflection doesn't get into the picture. If your mounts are not sufficiently rigid, chain tension under load will pull things out of alignment. It is in this area where you may discover why I wouldn't use those motors. :)
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rkcarguy
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Re: Electric drive motor specs

Post by rkcarguy »

BigDumbDinosaur wrote: Fri Oct 09, 2020 2:13 pm
Pontiacguy1 wrote: Fri Oct 09, 2020 10:53 amI think that you are a bit mis-matched when it comes to locomotive size/weight vs. trailing tonnage...

I find myself agreeing with this.

Assuming a train weight of 20,000 pounds, the drawbar pull required to balance the train on a one percent grade will be 200 pounds. If the train is running on dry and clean (i.e., not rusted) steel rail, we can figure on a 25 percent factor of adhesion, best-case. The weight on the drivers would have to be at least 800 pounds to produce the adhesion required to produce those 200 pounds of drawbar pull. If you are on a three percent grade, which is not entirely uncommon in large-scale railroading, now the required drawbar pull to balance the train is 600 pounds, and the required weight on the drivers to maintain adhesion jumps to 2400 pounds.

However, that only prevents the train from rolling back down the grade. If you are expecting forward motion :D your loco will have to develop proportionally higher drawbar pull and thus would have to be that much heavier to maintain adhesion. I think you can see where this is going.

Given the propulsion requirements to move a 20,000 pound train, I think your locomotive as described will not be feasible in battery-electric form. The big issue will be battery capacity versus required sustained power output over the desired six to eight hour operating period. Unless you were to go the lithium-ion route (costly and almost unobtainable in the sizes you would need), you are limited to deep-cycle type lead-acid batteries...lots of them.

Sealed lead-acid batteries of the type used in uninterruptible power sources are better able to sustain a long discharge than conventional deep-cycle batteries, but are two to three times as expensive as the latter. Either way, you would be hooking up a lot of batteries in series/parallel to get the required amperage (very high) to start the train and sustain a drag up-grade. My opinion is the battery mass required to propel your train at anything above a snail's pace, and do so for six to eight hours, will likely be larger than the locomotive itself—and substantially outweigh it.

Also, the traction motors you mentioned earlier are too lightweight for the expected loading. Given the expected train weight and using the power-to-weight ratio typical of full-sized work trains, you would need about 20 horsepower at the wheels to assure you can maintain a reasonable pace on an ascending grade. In this application, shunt-wound or permanent magnet motors would likely fall short; they may be able to propel the train once it is moving, but not be able to start it. Good luck on finding a series-wound motor with the required continuous output.

Have you given any thought to powering your loco with an ICE? I may be missing something here, but I foresee a lot of difficulties waiting for you in trying to do this with a battery-electric drive.
This is why I had to stick with burning dead compressed dinosaurs for my 12" ga RR. At 3% max grades and wanting 8000#'s of capacity an electric setup was going to be huge, short run time, and very expensive.
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Re: Electric drive motor specs

Post by rkcarguy »

Glenn, I have a 15HP generator that max's out at 7000 watts. Just some rough numbers, you'd need 2 of those to supply a pair of 7.5kw electric motors and the windings would likely be short lived. I'm seeing the need for around 30hp for what you want to do.
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Re: Electric drive motor specs

Post by Steggy »

rkcarguy wrote: Tue Oct 20, 2020 3:29 pm Glenn, I have a 15HP generator that max's out at 7000 watts. Just some rough numbers, you'd need 2 of those to supply a pair of 7.5kw electric motors and the windings would likely be short lived. I'm seeing the need for around 30hp for what you want to do.
Assuming 100 percent conversion efficiency, a generator driven by a 15 horsepower engine would produce 11.19 kilowatts. A more reasonable conversion would produce about 85 percent efficiency, equivalent to 9.51 KW, which is a net output of 12.75 HP.

However, with the train weights earlier quoted, I think a minimum of 20 HP at the wheels would be needed to produce acceptable performance—20 HP is 14.92 KW. Adjusting for conversion losses in the generator and motors, I too would say the prime mover would have to put 30 HP into the generator. Generator life would be prolonged by running it at no more than 75-80 percent design capacity, which means it would have to have a continuous rating of 22-25 KW minimum to avoid a meltdown at drag speeds under maximum load.

While I won't say it can't be done electrically, I will say the cost would be very high and the technical challenges would be considerable. While something like electric forklift motors can be used as traction motors, finding a DC generator with the requisite combination of voltage and amperage will be at least as difficult as trying to find the lost continent of Atlantis. :D And then there would be the switchgear...

What you need, Glenn, is a scaled-up version of the propulsion system in my F-unit, which was able during testing to haul nearly 8000 pounds up an approximate three percent grade. It was barely moving as it crested the grade, but it was moving—and that was with only 8 HP at the wheels.
8000 Test Train Climbing 3% Grade
8000 Test Train Climbing 3% Grade
F-Unit Power Assembly
F-Unit Power Assembly
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Music isn’t at all difficult.  All you gotta do is play the right notes at the right time!  :D
Glenn Brooks
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Re: Electric drive motor specs

Post by Glenn Brooks »

One of the problems is I don’t really want to mount a gas powered generator in each hood end. The noise and fumes would be overpowering. So looking for a way to make it work with battery power.

Iam certainly willing to drop down to 8000# consist or less. The ideal theoretical goal of 11k train weight and 6-8 hours running time, is what the loco could pull, given a weight of 1500# on drivers. But I recognize that may not be doable in 15” gauge. ... Plus cost is a factor. If I can make it work as a 15” ga , well, I’d go for it. Alternately something less would be fine, as long as it ends up being credibly functional.

Now, I keep looking at the EV conversions people have done around town. All using 36 v battery packs (note: re-reading this thread, I mistakenly wrote EF conversions use 36v battery packs. This is not true. EV conversions often use 144 to 350 v battery packs, with 9-11” series wound forklift motors, and perhaps as much as 1000 ah battery capacity- a substantial increase in power, GPB) and, mostly, forklift motors. Lots of VW’s and a fair number of other light weight cars have been converted this way. They are all larger and heavy builds, with sufficient range to run around town 50-200 miles per charge, depending on the configuration. So there does seem to be a proven method out there, albeit dependent on battery life. Which is all a bit frustrating as I can’t get the local EV club to answer their emails or respond to my list serve log in. So, still don’t have an actual resource to ask questions about what these are doing/ investigate the amperage consumption/battery life question. There is also the option of the emerging market for used, crash-surplused Tesla and other hybrid car batteries. Some are nearly near, aka battery life. These have higher battery life and deeper amperage capability than lead acid and deep cycle. But for sure, no one is using generators in their EV car conversions. So still looking for a workable design out there. Looks like it will take some more of poking-under-rocks to find out what the magic formulas are.

Glenn
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Motive power : 1902 A.S.Campbell 4-4-0 American - 12 5/8" gauge, 1955 Ottaway 4-4-0 American 12" gauge

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rkcarguy
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Re: Electric drive motor specs

Post by rkcarguy »

Tesla's have a motor on each wheel if I remember correctly, with "vectoring" speed control to each motor to keep scrub to a minimum as the car turns. I don't think it would be viable to use components from a wrecked one in your train, and even if it was, I'd be concerned that lugging the electric motors with a far heavier load with slow speeds and next to zero airflow for cooling would overheat them in short order. If your heart is set on electric, maybe a Tesla battery pack and electric lift truck motor and controls would be the best bet? Maybe you could even incorporate multiple batteries into the first piece(s) of rolling stock and have "MU cables" connecting to the engine.

Oh, and one more FYI. Right angle drives can contain worm gears which DO NOT spin down when the power is cut to the electric motors driving them. As a result, if they are used in a large scale train application and the throttle is chopped, all that rolling momentum in the train gets turned into lateral forces on the worm gear drive which blows the gearbox apart (or the wheels lock up and the train slides).
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