12" working railroad

Discuss park gauge trains and large scale miniature railways having track gauges from 8" to 24" gauge and designed at scales of 2" to the foot or greater - whether modeled for personal use, or purpose built for amusement park operation or private railroading.

Moderators: Glenn Brooks, Harold_V

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Topics may include: antique park gauge train restoration, preservation, and history; building new grand scale equipment from scratch; large scale miniature railway construction, maintenance, and safe operation; fallen flags; track, gauge, and equipment standards; grand scale vendor offerings; and, compiling an on-line motive power roster.
rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Wed Aug 30, 2017 3:30 pm

I'm thinking of naming my RR the "PG & F". Pallet-wood, Garbage, and Firewood Haha.

Glenn Brooks
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Re: 12" working railroad

Post by Glenn Brooks » Wed Aug 30, 2017 4:21 pm

RK,

In answer to your question regarding brakes. I asked around our breakfast meetup this morning about what type of break system people use. Mostly folk use vacuum brakes rather than air. No worry about pressurized air fittings and damage caused by hard operation and the usual banging around of components when coupling and uncoupling. Also, vacuum is more universally adopted for steam engines and mechanical propulsion - any vacuum source will work, such as a steam driven injector hooked up to a carburetor mounted style vacuum pump, or battery operated vacuum pump.

Another advantage of vacuum over air is that one needs no special fittings to connect vacuum lines between cars. Simply push the end of flexible vacuum hose over rigid tubing and let the vacuum pump tighten it down during use. Air hoses break and blow apart.

Also some people outfit each train/car with an accumulator tank to set up vacuum/air, then open it manually with a hand operated lever or valve to apply brakes.

For uncoupled braking, most people in the club use a separate, hand operated parking brake system. Such as turning a wheel that pulls a wire connected to the vacuum operated brake beam - manually closing the existing brakes on each truck.

Some others use a simple go kart brake drum kit mounted to a drum directly to the axle. See the image below for generic components. However often the diameter of go kart parts is to large for 4" wheel sets. 6" wheels might be OK.
IMG_1623.JPG
IMG_1623.JPG (13.44 KiB) Viewed 4128 times
The sketch below may be hard to read. Basically either vacuum or air clynders on each truck connect to brake linkage that pull brake shoes closed on each wheel. The idea here is that two brake linkages are connected on one end to solidly mounted brake beams, with the outside ends more widely spaced than the pivot points. When you apply vacuum or air, The clynder pulls them laterally towards the center of,the truck, forcing the brake shoes against the wheels. One set of vacuum closers, brake beams and linkages per truck.

They key is a small roller mounted on each side of the second brake beam. The rollers are off-set drilled - essentially creating an eccentric movemeant for the roller and mounting bolts, that enable the train operator to rotate the roller around the bolt, and take up slack against the break beam to adjust the brake shoes. I can make a larger drawing and post if needed.
IMG_4257.JPG
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....

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Wed Aug 30, 2017 7:09 pm

I'll look into it for sure, thanks for the tip.

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Fri Sep 01, 2017 1:38 pm

Lots of parts arrived yesterday. My 25' box of chain, 30T sprockets( I'm using Honda CMX-250 rear sprockets), the air cylinders, and rivets for the aluminum body. I grabbed my 2 sheets of .080 aluminum sheet from storage, and bought some 1/2 and 3/4 aluminum angle from the remnant shelf at another steel shop for $12. I also found a short piece of 3" aluminum pipe in the scrap bin I can use for the headlight "tube".
This weekend I'm planning to swap some things around to make room in the garage to get a bigger workbench and my welder in there so I can start building the body and frame of the locomotive.

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Fri Sep 01, 2017 1:53 pm

I know you guys would like some pics. I'm having a terrible time with Photobucket. It's so riddled with ads and both at work and at home I'm on a wireless router and it's almost unusable. I don't know if it's due to adblocker fighting the ads or the fact that so many of the ads have little clips of some truck driving or someone moving, or both, but it bogs everything down to a near stand still....and I have a pretty decent computer at both places. Pretty disgusting.

Note that I'm using 520 motorcycle chain and sprockets for this project. It's high strength steel construction is like 10x stronger than the cheap industrial chain. I shouldn't have to mess with it for decades, properly lubed and adjusted.

Lastly, I drew up some sketches to get sent off the to laser cutter. I am going to have them burn me some 7" solid rounds with 1" holes in the center from 3/4" plate, then weld some 3/8 plate rings to their backside for the flanges, and turn them on the lathe.

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Sep 05, 2017 12:03 pm

I think I am making some sense of the hydraulic pump and motors sizing.
I've found the CMM50 series motors offered by Prince, they are reversible instantly by reversing fluid flow, and this model has an 800 RPM rated max continuous. Flow chart info varies from 113 rpm at 2GPM to 578 rpm at 8 gpm. With the additional 2.3:1 chain reduction to the wheels, this gives me an RPM range of 49-251 at the wheels. Torque is 40 ft/lbs at the motors, which will be multiplied via the gear reduction to around 90ft/lbs, x 2 motors, total 180ft/lbs of torque if my math is correct.
This is all at 1400 PSI pressures.
I've reviewed the flow charts for pumps, and one offered is 16 gpm. Flow chart is 4 gallons per minute at around 1000 rpm, and 16gpm at 3000 rpm, but this flow chart is at 2500 PSI and the HP required exceeds my 16HP motor by quite a bit at this pressure. However, it appears that at 1500 PSI it's almost perfect at about 1HP=1GPM ratio.

Glenn Brooks
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Re: 12" working railroad

Post by Glenn Brooks » Tue Sep 05, 2017 12:37 pm

Given your intended wheel diameter, what does that translate into as far as speed range on your intended track?
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

Ahaha, Retirement: the good life - drifting endlessly on a Sea of projects....

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Sep 05, 2017 1:46 pm

The speed range should be 1mph at idle to 5mph at 3000 RPM. My engine has been modified and the governor removed, and some pumps can be ran up to 4000 rpm continuous, so there is an option for more speed via more engine RPM for short intervals. I raced this engine for 2 years and geared for a peak RPM of 5800, so I know it will take more than the pump will. It would also be simple enough to add a tooth to the hydraulic motors output shafts and trade some torque for speed if I must, but I think where I'm at now will work really well for what I want to do.
It's important to note that not a lot of motors are reversible without changing the configuration of the motor itself(configuring plugs and fittings for flow direction), as well as not being capable of side loading which a pulley or sprocket will do. These CMM series just have a simple in/out ports and are "instantly reversible", and are also capable and tested with 1000#'s + of shaft loading for 500 hours, so these are the ones you want.
Also notable, hydraulic motors can be driven in series or parallel. When in series, the fluid flows into one motor, out of it, and into the next and would only require a 8gpm pump in my case. There is a myriad of problems with this however (uneven motor speed and torque distribution, backpressure, and so on) so I will be splitting the outputs from the valve and running 2 hoses to each motor along with a 16gpm pump.

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BigDumbDinosaur
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Re: 12" working railroad

Post by BigDumbDinosaur » Tue Sep 05, 2017 2:32 pm

rkcarguy wrote:I think I am making some sense of the hydraulic pump and motors sizing.
I've found the CMM50 series motors offered by Prince...
Speaking from experience, I do not recommend Prince hydraulic products, especially their motors. Caveat emptor!
...they are reversible instantly by reversing fluid flow...
That's true of virtually all hydraulic motors.
...and this model has an 800 RPM rated max continuous.
The 800 RPM for a Prince motor is optimistic, in my experience. Most of them don't work well at all when they are operated near their rated maximum speed.
Flow chart info varies from 113 rpm at 2GPM to 578 rpm at 8 gpm. With the additional 2.3:1 chain reduction to the wheels, this gives me an RPM range of 49-251 at the wheels. Torque is 40 ft/lbs at the motors, which will be multiplied via the gear reduction to around 90ft/lbs, x 2 motors, total 180ft/lbs of torque if my math is correct.
This is all at 1400 PSI pressures.
I've reviewed the flow charts for pumps, and one offered is 16 gpm. Flow chart is 4 gallons per minute at around 1000 rpm, and 16gpm at 3000 rpm, but this flow chart is at 2500 PSI and the HP required exceeds my 16HP motor by quite a bit at this pressure. However, it appears that at 1500 PSI it's almost perfect at about 1HP=1GPM ratio.
No aspersions, but you are going about it all wrong.

Firstly, the most efficient design will use 1:1 "gearing" between motor and axle. There is no reason to set up the 2.3:1 drive ratio you speak of when you can achieve all the reduction you need in hydrostatics.

A fundamental design characteristic of hydraulic pumps and motors is that they possess "positive displacement." What this means is, neglecting losses, they move a fixed amount of fluid per revolution. The amount of fluid moved is the motor's or pump's "displacement," which is measured in cubic inches or cubic centimeters per revolution.

In a closed hydrostatic circuit, the ratio between pump displacement and motor displacement dictates the drive ratio, and hence the motor speed and output torque for any given pump speed and input torque. As a simple example and assuming zero losses in the system, consider the following:
  • Pump displaces one cubic inch per revolution (CI/rev),
  • Motor displaces 10 CI/rev,
  • Pump speed is 3600 RPM,
  • Pump input torque is 10 pounds/feet (Lb/ft).
The motor's behavior would be as follows:
  • Speed: 360 RPM,
  • Torque: 100 Lb/ft
In other words, the effect of 10:1 gear reduction is achieved. Incidentally, the input power to the pump in the above example would be approximately 6.8 horsepower. Disregarding losses, the motor will output 6.8 horsepower as well.

The three other ratings that get into the picture are flow, maximum pressure and maximum RPM.
  • Flow is measured in gallons per minute (GPM) or liters per minute (LPM). In the above example, the pump's theoretical flow at 3600 RPM would be approximately 14.4 GPM, computed by the formula:
    • GPM = RPM × d × .004
    where RPM is the pump speed and d is the pump displacement.

    In a closed system, the same flow will occur through the motor, whose RPM for any given flow may be computed by the formula:
    • RPM = GPM / (d × .004)
    where d is the motor displacement.

    Maximum flow for a motor is related to the maximum safe RPM at which it can operate. If you know that RPM number you can use it in the first formula to figure out the approximate maximum allowable flow.
  • Maximum pressure is a limiting factor that is determined by the mechanical strength of the components. Good design practice avoids operation at maximum pressure, as high pressure accelerates wear on components and decreases the life of the seals and hoses.

    The amount of pressure developed in a hydrostatic propulsion system depends on input power to the pump, the resistance of the load and losses in the piping and valves. The torque generated by the motor is a function of pressure. As it is desirable to avoid very high pressures, I have long used the design philosophy of larger displacement components, which can transmit a given amount of power at lower pressure. This is because larger displacement motors have more "mechanical advantage" and thus do not have to be pressurized as much to develop a given amount of torque.

    The flip side is that larger displacement components are physically larger and owing to the higher flow rates, may result in lower efficiency due to pumping losses in the circuit.
  • Maximum RPM is a limiting factor that, like maximum pressure, should be avoided. Most pumps will tolerate some overspeeding, but usually will suffer significant efficiency loss. Overspeeding a motor can cause damage or seizure.
My general rule of thumb for selecting pump displacement is 1 CI/rev per 10 horsepower, assuming good piping practice is followed (e.g., minimal use of elbows and hoses). From that, select the motor size that will produce the desired overall "gear ratio."

For example, my F7 has a 16 horsepower engine. I used a Barnes G25 pump with a displacement of 1.4 CI/rev. I used Dynamic motors with a displacement of 5.9 CI/rev. As the motors are piped in series, they look like a single 5.9 CI/rev motor to the rest of the system. Hence the effective drive ratio is 4.21:1.

As the maximum governed engine speed is 2400 RPM and the driving wheel diameter is approximately 5.188 inches, the maximum ground speed would be 8.8 MPH, which is 66 MPH in scale. It's a freight engine, so that speed is realistic.

The formula for computing speed is:
  • MPH = (RPM × D ) / (G × 336)
where D is wheel diameter and G is overall drive ratio.

Hope this information is useful to you.
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rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Sep 05, 2017 5:00 pm

Dinosaur, initially I was trying to calculate the effective drive ratio based on the CI/rev, but was finding variances in the math as far as cubic inches @ RPM and the conversion to GPM. Looking over what you've posted, we've gotten to the same place just different ways. I would say it's due to decreasing volumetric efficiency in the pump as speed goes up is my guess because I was getting #'s that were "faster" working from the Cu/in per Rev. Many of the companies offer flow charts based on actually flow and load testing their pumps and motors @ (blank) PSI with torque and RPM output under all the different conditions so that is what I based my information above on(Prince's downloaded chart).
The chart notes an 800 rpm max continuous speed, 1000 rpm intermittent, however I only need 600 rpm to be where I want to be at 5mph. Then I can still go down 1 tooth, or up several, on the sprocket on the motors output shaft. With two of them sharing a 16 GPM pump in "parallel", 8 GPM is 578 RPM at 1400 PSI and 614 RPM at 200 PSI so obviously it varies by load. Most of the valves adjust from 1500 on up, so I'd just run the system with a 1500 PSI setting on the bypass and honestly I'd bet it would see wheel slip before I hit 1500 PSI of system pressure. Not to mention, it looks like 1500 PSI on a 16gpm pump will about max out my engine's available HP, so I feel that the sizing is about right all around.

I have access to a lot of motorcycle parts, and I wanted my motors to be mounted atop the trucks inside the body where I could easily service them. I am also able to utilize the torque multiplication of the chain drive reduction and use smaller and less costly motors, as well as being able to change the output shaft sprockets for more speed or more pulling power as I see fit instead of replacing hydraulic parts. The motors I am looking at are 3.0 Cu/in per Rev. My wheels are going to be 7" is diameter, which x "Pi" gives me a 22" circumference(yours are 16.3"). Take the RPM of the motor at the various conditions from the flow chart, divide by 2.30 for the chain drive reduction in each truck, RPM x 22", then convert to feet per minute, then to MPH.
I'm guessing 180#'s of torque is easily going to slip the wheels, so I'm not worried about the hydraulic motors being too small and potentially failing.

I had researched and wanted Dynamic motors, but they seem to really lack info out there for them and I don't want to buy any of these parts twice, so I thought it was great the Prince had such detailed flow charts.

http://www.princehyd.com/portals/0/wolv ... eMotor.pdf

If they are not up to par as far as quality, I will continue to search for better specs on the Dynamic models. As there is some uniformity to the frame sizes in the industry, it appears your dynamic motors would cross over the CMM100 size Prince offers. I'd be curious as to the part # of your dynamic motor, maybe I can cross reference it to see what they offer in the next size down similar to the CMM50.

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Sep 05, 2017 5:12 pm

Found the Dynamic motor info.

http://www.dynamicfc.com/documents/2016 ... s_BMPH.pdf

Looks like the equal would be a BMPH50. No mention of side loads on the output shaft on this one. ????

rkcarguy
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Re: 12" working railroad

Post by rkcarguy » Tue Sep 05, 2017 5:54 pm

The Dynamic BMPH50 looks like it's more efficient and makes more torque but it's a touch slower at the same GPM. Adding an extra tooth to the output shaft sprocket would make it about equal in RPM at the wheels though to the Prince motor.

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