Author Topic: Trevithick  (Read 27043 times)

Offline Brian Rupnow

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Re: Trevithick
« Reply #180 on: October 14, 2020, 09:21:22 PM »
Mechanically, I'm at about 99%. I can tell, after playing with it half the day, that it wants to run. It is proving very difficult to set the 4 way valve so that it reverses the action of the cylinder at the end of the stroke. I've about had it for today, but wish me luck for tomorrow.

Offline Brian Rupnow

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Re: Trevithick
« Reply #181 on: October 14, 2020, 11:06:06 PM »
Game plan for tomorrow is to broach keyways in the flywheel, bronze gear, and crankshaft. Right now they are only connected with set screws, and the two offset pinions keep getting out of synch and locking things up.

Offline Art K

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Re: Trevithick
« Reply #182 on: October 15, 2020, 02:57:30 AM »
Brian,
That makes a lot of sense so much of that thing is interdependent. Anything could throw off the whole works. What do you figure that Mr. Trevithick had the same problem timing the original?
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Brian Rupnow

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Re: Trevithick
« Reply #183 on: October 15, 2020, 01:51:50 PM »
Art--probably not so much. Mr. Trevithick's engine weighed over 5 tons. the members which made up his engine could take a bit of off-center loading and not even notice it.

Offline Brian Rupnow

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Re: Trevithick
« Reply #184 on: October 15, 2020, 05:51:53 PM »
Keyways have been added to the flywheel, bronze gear, and to the crankshaft. It helps, but still doesn't let the engine get "over the hump" at each end of the stroke and continue running. Once an engine like this runs, it quickly wears down any "tight spots" and the longer you run it, the smoother it gets. Of course, the magic is in getting it to a point where it will run under it's own power. There really aren't any more changes I can do mechanically to get it running. This leaves me with two options. Make a bigger, heavier temporary flywheel to get it running, or hook it up to an electric motor and let it run for a couple of hours to get rid of any remaining tight spots. The electric motor method is the cheapest, since I don't have to buy any material, but this is not an easy beast to hook an electric motor to. I am going to call my metal supplier and ask about the price of a 8 1/2" square plate x 1/2" thick to make a much heavier flywheel.

Offline Charles Lamont

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Re: Trevithick
« Reply #185 on: October 15, 2020, 08:55:13 PM »
Brian, I can think of a couple of things you could try before having to make a new flywheel. Have you yet got it to the state where it will rock backwards and forwards by itself through a (not quite) half turn?
« Last Edit: October 15, 2020, 09:03:46 PM by Charles Lamont »

Offline Brian Rupnow

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Re: Trevithick
« Reply #186 on: October 15, 2020, 09:48:16 PM »
Too late Charles. Now you know how I spent my afternoon. This started life as a piece of 1/2" x 8 1/4" x 10" hot-rolled flatbar. There is no center hole in it yet, just a good center-punch mark. It has double sided tape on the side facing the lathe jaws and is held in place by a live-center in my tailstock. I cut the 4 corners off with my bandsaw and then spent the afternoon nibbling away at it until it is perfectly round. This method always works well for me, but you can only take about 0.010" depth of cut or the tape slips.  I'm not going to put a lot more time in this flywheel. Tomorrow it will get a centerhole and keyway and set screw, and have  a #10-24 thread put in 1 1/2" off center for the  shoulder bolt which connects the con rod. If the heavier flywheel does the job and makes the engine run, I'll worry about doing some cosmetic work on it later.

Offline Charles Lamont

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Re: Trevithick
« Reply #187 on: October 16, 2020, 07:54:31 AM »
Too late Charles.
It's hard to keep up with you, Brian. So, have you got it to the rocking stage?

Offline Brian Rupnow

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Re: Trevithick
« Reply #188 on: October 16, 2020, 01:41:07 PM »
I have it to the stage where the piston will go to one end, trip the 4 way valve, then travel back the other direction and stall out before tripping the valve to go the other way. that is why I'm trying a newer heavier flywheel

Offline Brian Rupnow

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Re: Trevithick
« Reply #189 on: October 16, 2020, 03:50:33 PM »
Okay Charles---Big changes with the heavier flywheel. The flywheel is rocking back and forth like crazy between top dead center and bottom dead center under air pressure.  This is very promising. Based on what it's doing now, it should just require some adjusting of the valve actuators on the slide bar. I have just blown an internal hose and have to tear things down to reconnect it. Is there any kind of liquid glue that I can permanently glue the neoprene hoses to the brass or steel tubes on the 4 way valve ? I do have some small spring wire clips from the hobby shop, but at higher air pressure the hoses keep blowing off. Crazy glue sets up so quickly that I wouldn't have a chance to put some glue on the steel tubes and then slip the neoprene hoses over them. Is there something like a "delayed action" super-glue?
« Last Edit: October 16, 2020, 03:55:12 PM by Brian Rupnow »

Offline Charles Lamont

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Re: Trevithick
« Reply #190 on: October 16, 2020, 05:46:47 PM »
Brian, do you have barbs on the pipe ends? I think they would be more likely to hold the hose than glue.

If you still have trouble getting it to go over the dead centre, even with more pressure, then I suggest you have another look at my earlier posts:
http://www.modelenginemaker.com/index.php/topic,9902.msg225576.html#msg225576
http://www.modelenginemaker.com/index.php/topic,9902.msg225580.html#msg225580
I suspect that once you do get it to run, you may need a regulator (throttle valve) to stop it going into orbit.

Charles
« Last Edit: October 16, 2020, 05:53:02 PM by Charles Lamont »

Offline crueby

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Re: Trevithick
« Reply #191 on: October 16, 2020, 07:13:49 PM »
I always need to turn barbs into the ends of the pipes for the plastic hose, then put either a hose clamp or for smaller tube I just twist some bailing wire around it.

Offline Brian Rupnow

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Re: Trevithick
« Reply #192 on: October 17, 2020, 12:03:56 AM »
I learned three new things today. #1--There is a type of crazy glue that doesn't dry instantly--it gives you about 15 seconds between when it is applied and when it dries. This is enough time to coat a hose barb (actually a piece of 0.185" diameter brass tube) and slip a neoprene hose over it before it becomes absolutely immoveable.---If you're quick!!
---#2--If you have a bunch of air connections inside something else that requires an hours work to take it apart, then never, ever, ever use neoprene tubing  pushed onto metal tubes for connections.--Make them from metal tubing and solder them in place.
---#3---Engines which have wheels on them are as suicide prone as lemmings, which jump off cliffs into the sea. I've probably grabbed this damn thing out of the air half a dozen times today when it jumped off my desk. I haven't moved so fast since my wedding night.

Offline propforward

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Re: Trevithick
« Reply #193 on: October 17, 2020, 12:11:41 AM »
That thing about Lemmings was a falsehood perpetuated by Walt Disney studios. Tell your engine! Maybe it will stay put.
Stuart

Forging ahead regardless.

Offline crueby

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Re: Trevithick
« Reply #194 on: October 17, 2020, 12:23:03 AM »
Three very good lessons!    :Lol:

 

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