Author Topic: Trevithick  (Read 13360 times)

Online Brian Rupnow

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Re: Trevithick
« Reply #75 on: September 05, 2020, 03:14:57 PM »
Holy Porcapine Roy!!!--That's a lot of hose barbs. I finished drilling and threading the hose barbs this morning and installed them all into tapped holes in the cylinder body with 638 Loctite. Next up will be the cylinder divider, piston, and spool.

Online crueby

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Re: Trevithick
« Reply #76 on: September 05, 2020, 07:19:01 PM »
There's a company near me that repairs pipe organs, you may have a new career there...


 :popcorn: :popcorn: :popcorn:

Online Brian Rupnow

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Re: Trevithick
« Reply #77 on: September 05, 2020, 10:45:28 PM »
Today yielded a piston, a spool valve, and a cylinder partition plate. Those o-rings are Viton---Didn't need to be because there is no heat involved, but that's what I had. I still have to drill and tap 3 holes in the cylinder partition plate.

Online Brian Rupnow

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Re: Trevithick
« Reply #78 on: September 08, 2020, 01:20:29 AM »
The self reversing cylinder as designed by Julius is almost ready for final assembly.  I have all the parts finished, but I have to buy a very small center drill tomorrow to use for starting a 1 mm diameter drilled hole thru a collar which sets out of site inside the spool. I honestly don't know what to expect here. If it works, I will be greatly impressed. If it doesn't, I will go ahead with a design using a rotary valve as used on the original Trevithick engine.

Online Brian Rupnow

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Re: Trevithick
« Reply #79 on: September 08, 2020, 04:17:09 PM »
I had to do it. I've been thinking of a 4 way valve for the last week, so this morning I had to spend a bit of quiet time and model one. I'm not even sure of what I will do with it yet, but at least my head is clearer now that I have a model that I can understand.

Online crueby

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Re: Trevithick
« Reply #80 on: September 08, 2020, 04:20:53 PM »
Well, if the slide valve version you have been building works, you will just have to build one of Trevithicks other locos or wagons to use the 4-way valve in!
 :popcorn: :popcorn: :popcorn:

Online Brian Rupnow

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Re: Trevithick
« Reply #81 on: September 08, 2020, 07:26:03 PM »
Unfortunately, I couldn't get the cylinder with the spool valve to work. I have tried all of the tricks that I know, and it just isn't happening for me. There is a small diameter cross pin (1 mm) thru the center shaft and a collar that is pinned to the shaft, and they are both hidden inside the spool when assembled. When trying this out with 20 psi of air pressure, the 1 mm diameter pin immediately sheared off. The pin was made of 1 mm diameter unheat-treated drill rod, so it was certainly the strongest steel that I had. I am going to go ahead and re-use the piston, piston rod, and front and rear cylinder caps and guide bushing. I will make up a new cylinder  which is operated by a 4-way rotary valve, same as the original Trevithick engine.

Offline Craig DeShong

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Re: Trevithick
« Reply #82 on: September 08, 2020, 10:31:15 PM »
Sometimes you have to take a step backward, before you can take two steps forward.  We’ve all been there.  It’s just part of ‘designing your own’. 

Great progress over all.  Learning something that doesn’t work is still learning. :old:
Craig

Online Brian Rupnow

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Re: Trevithick
« Reply #83 on: September 10, 2020, 04:42:37 PM »
So, after a rather questionable beginning, we start again. This time it will be with a 4 way valve which I design, and a rather plain Jane cylinder. I changed the shape of the boiler, because the convex end adds a level of complexity that I don't need to deal with. This entire project is going to depend on my ability to design and build a 4 way valve, so that is where I will begin.

Online Brian Rupnow

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Re: Trevithick
« Reply #84 on: September 10, 2020, 11:45:44 PM »
Tomorrow I will start building a 4 way valve. The main body will be mild steel, while the green center spindle is machined from cast iron and will be lapped into the steel housing for a very close fit.  First, before I machine anything, I have to go across town to Hercules O-Ring and buy the o-rings I need to seal things up. (They are shown in red in the assembly model.) There is no heat involved here, so they will be Buna-N material. My design is very much dependent on the actual size and cross section of the o-rings. When the transparent red cap is attached to the green spindle with a #10 shcs., the rubber o-rings will be partially compressed.

Online Brian Rupnow

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Re: Trevithick
« Reply #85 on: September 11, 2020, 07:26:03 PM »
Well, that was pretty painless. The only catch was that the o-rings are 9 cents each, but the minimum sale is $15.00---As a result of this I have enough of that size of o-ring to last for the rest of my natural life!!!

Offline Craig DeShong

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Re: Trevithick
« Reply #86 on: September 12, 2020, 12:17:38 AM »
Well, that was pretty painless. The only catch was that the o-rings are 9 cents each, but the minimum sale is $15.00---As a result of this I have enough of that size of o-ring to last for the rest of my natural life!!!

Well, plan on living quite a while longer then  :ThumbsUp:

Glad you're back on track... ever though this model doesn't have any (tracks :insane:)
Craig

Online Brian Rupnow

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Re: Trevithick
« Reply #87 on: September 13, 2020, 01:30:10 AM »
I think this is going to work. So far, I have only tested it with the "Blow your guts out" method, and when the spindle is turned so that the slots don't align with the port you are blowing in, you can't blow.--When they are aligned, you can. I know, that's a pretty cheesy way to test something, but it's cheap and quick. I still have to make the cap which attaches to the end of the spindle which doesn't have a flange, and compresses the o-rings.  I will make that last part tomorrow, and hopefully the valve will function the way I want it to. I am attaching a video link about Trevithick's engine, and about 13 minutes in you can see an animation of the same valve as built by Trevithick over 200 years ago.

« Last Edit: September 13, 2020, 01:34:50 AM by Brian Rupnow »

Online Brian Rupnow

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Re: Trevithick
« Reply #88 on: September 14, 2020, 01:28:27 AM »
The 4 way valve is finished. Not the handsomest piece I've ever crafted, but only the round metal top part with the 3/32" rod will show above the boiler housing. As the piston travels in and out, a mechanism on the cross head will move that rod thru a 90 degree arc, thus reversing the flow of compressed air to the cylinder. It is assembled dry right now for trial "fit-up", but will be greased with white lithium based grease to make it easier to rotate the center spindle for operating.  I have to figure out some way of testing it tomorrow. Might have to "borrow" a cylinder off something else to test the valve and see if it does what I want.

Offline Art K

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Re: Trevithick
« Reply #89 on: September 14, 2020, 02:28:58 AM »
Brian,
I watched that video last night. He was quite creative to come up with ways to make this work. His whole flue setup being riveted and not leaking, yeah they made boats later that were riveted but when the modern way of welding it was a century away. I liked the pegs to keep from overstearing.
Art
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