Author Topic: RC Model Steam Project  (Read 15507 times)

Offline kvom

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Re: RC Model Steam Project
« Reply #25 on: June 17, 2009, 08:27:34 AM »
As a mechanical engineer by training, if not by prefession, I have found it interesting to see how the piston valve works on John's engine. 

One aspect that I have not examined is that optimal phasing of the valve and piston.  Assuming that the engine runs at a constant RPM, then the positions of the piston and valve plotted against time will be sinusoidal curves that are out of phase by some amount.  I would expect that the engine will run over a given range of phase difference, but that one phase would be optimal.  I am now wondering if the phase setup given by the tuning instructions yields the optimum operation.  Obviously it is pretty hard to adjust the eccentric angle by just a few degrees on a model, so this is mostly an academic question.

However, I have read on this forum that piston valves were used on real steam trains in the past, and I'm sure the phase would have been adjusted for peak performance.

Offline Bernd

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Re: RC Model Steam Project
« Reply #26 on: June 17, 2009, 08:42:55 AM »
However, I have read on this forum that piston valves were used on real steam trains in the past, and I'm sure the phase would have been adjusted for peak performance.

kvom,

Your right. The steam locomotives built in the later years used piston valves. But I believe the piston valves worked more on the principle of the D-valve since they had linkage to reverse the engine and not a valve such as is used in the Paddleducks Engine.

Well I've got material that I think I can use to start the chassi and wheels. So look forward to a new "Projects" thread soon.

Regards,
Bernd
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bogstandard

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Re: RC Model Steam Project
« Reply #27 on: June 17, 2009, 10:39:55 AM »
I think you will find that on model engines, it doesn't make much difference, but on larger engines, where they use a lot more steam (not air) the timing and duration was altered as the engine speeded up to allow a more efficient use of the expansion of the steam.

Imagine the engine running at full wack, to keep it running at that speed only needed the pistons to be nudged at a specific time, for a shorter duration, rather than having the full charge of steam admitting into the chamber.

The same principle as you use when driving your car on a motorway, foot to the floor to get you up to the required speed, then gently back off on the accelerator, so the car stays at the same speed, but uses less gas.

Only laymans terms, but explains the reasoning behind it.

Bogs

Offline Bernd

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Re: RC Model Steam Project
« Reply #28 on: June 23, 2009, 09:34:43 PM »
John,

I've been eyeing that engine you posted a pic of at the begining of this thread. It looks simular to the one on the French web site given here somewere. I was wondering if it would work with say 3/16" bore by 3/8" stroke. Then connecting it through one of these Tamyia Gear Boxes. I'm looking at using this for a steering engine. Still working (pictureing in my mind) on the components for making it steer. I want to start with the engine first. It needs to be compact.

Your thoughts?

Bernd
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Offline rleete

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Re: RC Model Steam Project
« Reply #29 on: June 23, 2009, 10:19:17 PM »
Bernd, search Craigslist (or post a want ad) for a cordless drill with a dead battery.  You ought to be able to get one cheap.

Same type of gearset in the nose, and built to withstand quite a bit of abuse.  Heck, I have an old sears one you can have, if you're willing to come get it.
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Offline Bernd

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Re: RC Model Steam Project
« Reply #30 on: June 24, 2009, 11:15:12 AM »
Roger,

Thanks for the offer but I already have one of those and sort of gave it a trail fit. It's to big for what and where I might mount the gear set.

That planetary gear set looks just about right. If the 3V electric motor I have here is any indication, that gear set should be somewere in the neighborhood of 1" in dia. Just about right for what I need.

You have given me another idea with the planetary from the drill though. I can use that for powering the next steam powered vehicle I build.   :proj:  :ddb:

Bernd

P.S. save that one you got I might just drop by and pick it up. Keep the beer cold.  :ddb:  :ddb:
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Offline rleete

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Re: RC Model Steam Project
« Reply #31 on: June 24, 2009, 11:44:26 AM »
The one I have is slightly smaller than those found in pistol style drills.  It's one of those straight cordless screwdriver things, and the rechargable batteries are dead.

Sorta like this one:  http://www.sears.com/shc/s/p_10153_12605_00998422000P?keyword=screwdriver#crumbWrapper  I doubt the outside diameter of it is much more than 1.5", probably less once you open it up.
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Offline Bernd

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Re: RC Model Steam Project
« Reply #32 on: June 24, 2009, 03:25:58 PM »
Roger,

Oh ok. That looks like it's smaller. I was thinking the larger version, just like the regular drill sizes.

When do think a visit would be workable. This weekend Sat. would be ok in the late afternoon or some time on July, 14,15, or 16, in the evening would be fine for me. Or some other time toward fall would be fine too. Spending lots of weekends up at the River now that it's warmer. PM me and let me know. As you know I'm free during the week days to.

Regards,
Bernd
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Offline rleete

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Re: RC Model Steam Project
« Reply #33 on: June 24, 2009, 04:13:45 PM »
This weekend is out, as it's the annual camping trip.  27 years and counting for the rest of the crew, 25 years for me (I missed a couple).  We go out in the middle of nowhere (south of Penn Yan) and camp in the woods.

After that, I'm pretty much free for the summer in the evenings.  Weekdays are okay for me, but I don't get home from work until 5:30 due to summer hours.  I'll send you my phone number.

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Offline Bernd

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Re: RC Model Steam Project
« Reply #34 on: June 29, 2009, 09:16:40 PM »
I've been doing a bit more design work on this project. I've been thinking of how I want to steer the trike. Not wanting to use a servo to do this job I contemplated using a steam engine. I've been looking at the J P Duval twin double action wobbler.
Found here : http://jpduval.free.fr/Moteurs_vapeur_simples/MV%20deo%2010x20.pdf

It's very similar to the horizontal engine Bogs shows at the beginning of this thread. I like that design very much since it's double acting and self starting, plus no complicated linkage to control reversing the engine or speed. It's all done with one valve.

On Bogs engine there is a gear reduction of 3 to 1. He says it's very powerful with the reduction. While looking at the Crabfu steam site I noticed he used a lot of Tamiya gear boxes to drive his steam powered vehicles so I did a little research and found a place here in the US that sells these gear boxes. They can be found here: http://www.servocity.com/html/tamiya_gearboxes.html
I purchased both the dual motor drive and the planetary drive.


I've been in contact with Bogs about what size I should make the steam engine to drive the steering and he suggested 3/16" bore by 3/8" stroke. This engine will then be hooked to the planetary gear box, this in turn will drive a threaded shaft that will have a nut on the threads that will be attached to a geared rack that will drive a pinion on the steering shaft. It's an idea and I don't know if it'll work. Just think of it as a steam powered power steering.

I'm also rethinking the goose neck front end. I'm thinking of making it with angled lines instead. This needs to be researched further and before this engine is designed and built. I'll need the chassis built up for the main engine which is going to be a pretty standard piston valve engine.

Hopefully soon I'll have more to add to the build thread. I've got some of the rear wheel parts roughed out and ready for some finishing work. I still need to assemble the chassis before the wheels will be made. Also I need to come up with an axle size for the rear wheels and weather I want to use a friction bearing or ball bearings for the axles to ride in. Right now I'm awaiting for some drill rod to arrive so I can determine what size I'm going to make the rear axles.

Not much is going to happen with in the next three weeks. Vacation coming up for the 4th. Going to spend it up at the Islands. So not much modeling will be done other than dreaming about how to build this model.

Regards,
Bernd
You can't fix "STUPID".