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Old Jul 25, 2014, 12:11 AM
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Preston Steam Engine Reversing Gear

Dave has worked out the details of the reversing gear. See the image below. We are using a linear servo that can extend over an inch with a force of 40 newtons (8.99 pounds of push) The single servo will rotate a jackshaft with bell cranks on either end. Lift links attach to the hourglass cages. A tiny bit of slop must be provided for in the lift links, so each lift link will have tiny centering springs to allow for this play. I'll program the servo on the DX10t to precisely move the correct distance to protect the eccentric rods from being bent by the linear servo over-driving the lifting mechanism. In the drawing you are looking at one side of the engine. The 3/16" jackshaft will extend athwartships connecting the other cylinder/reversing gear mechanism. Servo travel speed will be set to smoothly reverse the steam engine.

Snagboat Mike
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Last edited by hookpilot; Jul 25, 2014 at 12:31 AM.
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Old Jul 26, 2014, 09:30 PM
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Preston's Reversing Scheme

Open the PDF below and toggle between page 1 and 2 to see how the linear servo operates the reversing gear. A few odds and ends left to machine and the engine will be ready to install in the boat.

Snagboat Mike
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Old Jul 27, 2014, 12:27 AM
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While programing servo travel is perfectly acceptable....you might want to change to a physical limit system in case your servos go nuts. This can happen if the batteries run down/go bad unexpectedly. I once had Pamir, my 4-masted barque, experience low voltage fluctuations during high winds (the alkaline batteries I was using on board the model were not up to the job). The rx would go offline when the voltage drop happened; then, when the rx came back on line, the servos would slam the yards back and forth, irrespective of servo limiting via the tx. The poor Pamir essentially flapped its way across the pond, with no response to my tx stick movement (the rx would come online for only a second, flap the yards, then drop offline).
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Old Aug 01, 2014, 01:05 AM
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Servo Travel

Quote:
Originally Posted by Brooks View Post
While programing servo travel is perfectly acceptable....you might want to change to a physical limit system in case your servos go nuts. This can happen if the batteries run down/go bad unexpectedly. I once had Pamir, my 4-masted barque, experience low voltage fluctuations during high winds (the alkaline batteries I was using on board the model were not up to the job). The rx would go offline when the voltage drop happened; then, when the rx came back on line, the servos would slam the yards back and forth, irrespective of servo limiting via the tx. The poor Pamir essentially flapped its way across the pond, with no response to my tx stick movement (the rx would come online for only a second, flap the yards, then drop offline).
Brooks: Very good idea. When I install the reversing servo it will be easy to physically limit travel and then adjust with TX for fine tuning movement.

Snagboat Mike
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Old Aug 07, 2014, 08:55 PM
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More Preston Reversing Gear Work

Work on Preston's steam engine continues. The linear servo installation in the test fixture is nearing completion. The jack shaft now rotates in bearing blocks that are temporarily epoxied to the aluminum deck. The 3/16" shaft rotates in the bronze blocks and have lubrication holes drilled. The bell crank and lift arms will be locked in place with keys.

Snagboat Mike
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Old Aug 08, 2014, 06:11 AM
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Hi Mike,
just beautiful!

When will we finally see a video of the Preston in the pond running under live steam?

Ernst
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Old Aug 08, 2014, 08:22 PM
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Hi Mike,
just beautiful!

When will we finally see a video of the Preston in the pond running under live steam?

Ernst
We have no date for launching and christening, but we're getting close. Left to do on the hull is fire the boiler for the first time and check out all the automatic features, i.e.: attenuator and water level control system, and do a functional test of the fire suppression system. On the steam engine, left to do is:bronze eccentrics (temp. ones are aluminum), make the two mechanical lubricators, machine connecting steam pipes with flanges into engine valve case, machine the cylinder drain valves, and machine the exhaust pipes with flanges. With all this we'll be able finish this project. Given all this, I'd say we are about a month away from completion, probably mid September. A party is planned for the event.

Snagboat Mike
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Old Aug 09, 2014, 12:55 AM
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As it is completely deserved and earned! Look forward to the launch video!
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Old Aug 23, 2014, 11:53 AM
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Preston and Model

Here's a look at a side by side comparison.

1:1 and 1:32

Snagboat Mike
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Old Aug 23, 2014, 07:36 PM
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Need Source for Steam Oil

Anyone have a source for 460 steam oil in quantities larger than a small 4 oz bottle? I'd like to get a pint can if possible.

Snagboat Mike
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Old Aug 23, 2014, 08:03 PM
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Might be worth a trip to see the maintenance shop guys here
https://www.trainmuseum.org/index.php

Don't know if they use steam oil or not. If they do, you may be able to make a donation and have them slip you some out of a 55 gal drum. They would probably enjoy hearing about your model, too.
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Old Aug 23, 2014, 09:25 PM
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Quote:
Originally Posted by hookpilot View Post
Anyone have a source for 460 steam oil in quantities larger than a small 4 oz bottle? I'd like to get a pint can if possible.

Snagboat Mike
Contact one of the major oil companies, After showing my model to one of their reps she arranged for me to get two one quart tins.
Regards,
Gerald
PS this was several years back, they may want more than a thank you letter and a photo of the model now.
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Old Aug 26, 2014, 08:53 AM
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Quote:
Originally Posted by hookpilot View Post
Anyone have a source for 460 steam oil in quantities larger than a small 4 oz bottle? I'd like to get a pint can if possible.

Snagboat Mike
PM Research is where I buy mine. Select either 8 oz or quart from the drop down.
I have no idea the difference between 460 oil and cylinder oil 8.

http://www.pmmodelengines.com/shop/l.../cylinder-oil/
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Old Aug 30, 2014, 02:37 AM
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PM Research is where I buy mine. Select either 8 oz or quart from the drop down.
I have no idea the difference between 460 oil and cylinder oil 8.

http://www.pmmodelengines.com/shop/l.../cylinder-oil/
Hey, thanks. That's what I'm looking for. Preston's engines are almost completed and ready for installation.

I'm in the middle of a move, so things will be a bit disrupted for a while. The new house will be on a lake. Several candidates look good.

Snagboat Mike
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Old Sep 06, 2014, 03:06 AM
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Preston's Boiler Fired for First Time

W.T. Preston's Maccsteam 3 1/2" boiler was fired for the first time on Sept. 5th. All the valves and plumbing were subjected to 60psi steam pressure with only a few very minor leaks. The boiler's safety relief valve lifted at the proper 60psi. The boiler produced steam at 40psi for 30 minutes on 3/4 tank of distilled water. The engines are now ready to install in the boat.

Snagboat Mike
Preston Boiler First Firing (2 min 55 sec)
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