Allen models Fitchburg Northern build by first timer

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mcjustis
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Re: Allen models Fitchburg Northern build by first timer

Post by mcjustis » Tue Dec 07, 2021 2:51 pm

Thanks Russ, I'll check it out.

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Bill Shields
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Re: Allen models Fitchburg Northern build by first timer

Post by Bill Shields » Tue Dec 07, 2021 4:49 pm

Very nice...

quad rings work very well in this application.

are you going to actuate with air or hot water?
Too many things going on to bother listing them.

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Re: Allen models Fitchburg Northern build by first timer

Post by mcjustis » Tue Dec 07, 2021 10:08 pm

I was just going per plans and using steam. Or is there a more preferred way? Is there a recommended brake valve or do you just use a simple globe valve?

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NP317
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Re: Allen models Fitchburg Northern build by first timer

Post by NP317 » Tue Dec 07, 2021 10:27 pm

For steam brakes, you will need a control valve that can apply steam, and bleed off that same pressure.
My experience with my Allen Ten Wheeler's steam brakes is that the steam condenses and often lets water into the brake cylinders.
I installed small globe bleed valves at the cylinder top allowing bleed off of the water, if the brake valve fails to let that happen.

Check with Jeff Dute of LocoParts to learn if he offers a brake valve appropriate for steam use.
I cannot remember where I purchased those brake valves. used in my two steamers.
RussN

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Bill Shields
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Re: Allen models Fitchburg Northern build by first timer

Post by Bill Shields » Tue Dec 07, 2021 10:29 pm

So it is hot water... :mrgreen:

I use a push pull three way piston valve with oring seals that I made....but that is not typical. I did this to accommodate an engineer who cannot reach over to a conventional brake valve...and loco brakes are used as much for parking as anything else.

In reality most of what gets to the piston is hot water..since much of the steam condenses before it gets there.

Pressure is pressure.

You need a way to vent the water back out to the atmosphere to release the brakes...so a standard globe valve is not the best unless you add a second on a tee to use for venting..which makes using as a running brake quite problematic as releasing becomes...complex.

Suggest look at a more conventional brake valve arrangement..others will have lots to suggest.

The loco brakes are not the most useful for stopping a load..esp on a lighter loco ..the wheels will just slide.
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Re: Allen models Fitchburg Northern build by first timer

Post by Berkman » Wed Dec 08, 2021 10:36 am

you could use a clippard air cylinder in place of the steam brake cylinder. - super simple, very reliable, then use a tom bee brake valve on the tender that controls air to the engine + tender brakes. Mount a small compressor in the tender.

This setup will be very effective, also lets you have brakes on the engine/tender when loading/unloading without steam.

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Re: Allen models Fitchburg Northern build by first timer

Post by mcjustis » Wed Dec 08, 2021 10:58 am

Never thought about doing that. I have several of those air cylinders laying around in my junk drawer. I just keep following the plans, perhaps I should start thinking outside the box. Thanks!

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Re: Allen models Fitchburg Northern build by first timer

Post by Berkman » Wed Dec 08, 2021 11:02 am

You will have a lot of braking power for a small train with air driver brakes + tom bee or mountain car tender trucks with air brakes.
From here, it's very very simple to add air brakes onto a few following cars since you already have the air system setup on the engine.

I think a lot less hassles than doing steam brakes, making condensation drains etc. plus you can use it as a parking brake and not run down your boiler pressure, etc.

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NP317
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Re: Allen models Fitchburg Northern build by first timer

Post by NP317 » Wed Dec 08, 2021 12:51 pm

Brakes on my steamers use steam brakes for the locomotive drivers, and vacuum brakes for the tender and cars behind.
The loco steam brakes I use primarily as parking brakes, as they do not consume steam when applied. Yes, they can lock the driver rotation.
The vacuum brakes are the primary stopping power, and the vacuum ejector only uses a small amount of steam when activated.

Air brake systems are better, especially for larger steam trains, but for your Fitchburg Northern you are probably never going to require that much braking capabilities. The locomotive lacks the tractive effort for a long train, unless on level tracks.
I like the simplicity of steam brakes for the loco, and vacuum brakes for the tender and cars behind.
Totally self contained, simple, and they work as long as there is steam available.

Anyone can make a train go. It takes some skill to control speed and stopping events. Dual braking systems are prototypical and fun to use. For me.

My 2 cents worth.
RussN

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Re: Allen models Fitchburg Northern build by first timer

Post by Greg_Lewis » Wed Dec 08, 2021 2:45 pm

Here's a question for the physicists out there: For simplicity sake, let's say the area of the brake cylinder piston is 1 square inch. So if you have 125 psi steam, the steam feeds into the piston, fills the cavity, and you would get 125 lbs of push on that piston.

Now let's say that instead of the above, the cylinder fills with condensed steam, a.k.a. water. And let's say so does some of the piping leading to that cylinder. So now the steam from the boiler is pushing only on the water that's in the piping. And let's say the pipe to the cylinder is 3/16 inch inside diameter, making area of the inside of that piping .0274 inch. So the pressure on that is .0274 x 125 = 3.425 lbs. So how does that three and a half pounds of pressure translate to 125 pounds at the piston? Why is not the pressure on the piston 3.425 lbs. or even less since the area of the piston is 36 1/2 times the area of the pipe and therefore the total pressure on the piston should be 36 1/2 times less than 3.425.

:?

(My head hurts. I'm going for lunch.)
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Re: Allen models Fitchburg Northern build by first timer

Post by Pontiacguy1 » Wed Dec 08, 2021 3:01 pm

I think you are confusing pressure with volume. A brake cylinder doesn't need a lot of volume of steam or air, just the pressure to make it move. A cylinder that is reciprocating and constantly using steam will need a much higher volume of steam or air moving through it to maintain its power output.

Same reason brake lines on a car aren't super huge. The pistons that activate your car brakes need a lot of pressure, but not a lot of volume.

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Re: Allen models Fitchburg Northern build by first timer

Post by Greg_Lewis » Wed Dec 08, 2021 7:57 pm

Thanks. Makes sense.
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Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.

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