Author Topic: Steam Tractor 3/4" (Rudy K)  (Read 174213 times)

Offline crueby

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #795 on: August 28, 2017, 10:27:26 PM »
I put a slip eccentric on "Robby" my Roberts Mechanism engine. The discussion starts here:

http://www.modelenginemaker.com/index.php/topic,5293.msg107925.html#msg107925

It worked fine, but I disabled it because it caused a distinctive knock that I didn't want to be heard when showing it. I don't know if that's common to slip eccentrics or just my own implementation.
I never really put any effort into trying to remedy it.

--Tim

I remember that build Tim!   But it doesn't show any completed pictures.  You should post one.

I could see how a slip eccentric might result in a knock.  In fact, when I rotate the drive shaft by hand, at a certain point in the rotation (at least in one direction) the eccentric pin disengages from the drive collar as gravity pulls it down. Then the flat on the collar catches up with it and things continue as expected.  That could certainly cause a tick!  I'll have to listen next time and see if I hear any knocking.

Kim
I wonder if a small spring loaded detent would do the trick to keep it from slipping?

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #796 on: September 03, 2017, 01:16:38 AM »
I put a slip eccentric on "Robby" my Roberts Mechanism engine. The discussion starts here:

http://www.modelenginemaker.com/index.php/topic,5293.msg107925.html#msg107925

It worked fine, but I disabled it because it caused a distinctive knock that I didn't want to be heard when showing it. I don't know if that's common to slip eccentrics or just my own implementation.
I never really put any effort into trying to remedy it.

--Tim

I remember that build Tim!   But it doesn't show any completed pictures.  You should post one.

I could see how a slip eccentric might result in a knock.  In fact, when I rotate the drive shaft by hand, at a certain point in the rotation (at least in one direction) the eccentric pin disengages from the drive collar as gravity pulls it down. Then the flat on the collar catches up with it and things continue as expected.  That could certainly cause a tick!  I'll have to listen next time and see if I hear any knocking.

Kim
I wonder if a small spring loaded detent would do the trick to keep it from slipping?
Maybe, Chris, but I don't think I'll be worrying about that at this point. :)
But it is a good thought!
Kim

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #797 on: September 03, 2017, 01:24:28 AM »
Today, I made the Blast Pipe.  My understanding of this part is that it channels the exhaust from the cylinder up the smokestack in such a way as to help increase the movement of the hot air from the fire box past the boiler.  I never knew that this existed, so this is all fascinating new territory for me!

Each individual piece of the Blast Pipe is, in itself, quite simple, so I didn’t end up taking to many pictures of that.  But the overall fabrication was quite extensive! At least for me it was!

I started with the elbow, which was just a piece of 1/4" brass rod.  Using the lathe, I put a 1/8” hole in it for 3/8” of an inch, and cut it off at 1/2".  Then took it to the mill and put a 5/32” hole about half way through.  I didn’t have a 5/32” Ball End mill, so I used a flat end to make the initial hole, and switched to a 1/8” Ball End to help ease the 90 degree corner in the bottom.


After that, I cut a length of 1/8” brass tube, and 5/32” brass tube.  I took notches out of each pipe so it wouldn’t interfere with the elbow.


Now to silver solder them together!  Sounds so easy, doesn’t it? As it usually goes with me, the first time around didn’t end up so pretty.  I melted the 5/32” pipe.  And clearly, I used WAY too much solder!  I was struggling, can you tell?


So I fired up the torch again and unsoldered the 5/32” tube out of the elbow, and cleaned it up again.  Then made another length of 5/32” tube and tried that joint again.  SO much better the second time!  I was so happy with it that I completely forgot to take any pictures.

After some clean-up, I went to reduce the diameter of the blast end of the pipe.  I wasn’t sure how to do this – I kept looking for some way to build a cone, or something that I could use to reduce the diameter of the tube, but in the end, I used a pair of flat nosed pilers, lightly squeezing and turning the tube at the same time:


I annealed the brass tube several times during this process, and it seemed to work OK.

Next, I needed to add a bend in the Blast Pipe.  So I took a scrap piece of aluminum bar and cut an 1/8” wide channel in it, deep enough to give me the radius I was looking for (1/4”).  Then after annealing the brass tube again, I bent the tube using that channel. It again took me 3-4 annealings to get the full 90 degree bend.  Unfortunately, I didn’t take a picture of that either.

And even more unfortunately, I made the bend the wrong direction. :facepalm2: It should be the other way!  :insane:


So, more annealing and bending to get it back ‘mostly’ straight, and then more annealing and bending to get it bending the correct direction.  But I got there!

With that finally done, I still needed to add the mounting flange.  This was nothing more than a 9/16” brass washer I made.  I drilled the two mounting holes, and then silver soldered it to the Elbow of the Blast Pipe.  This time I did it much better, the first time!  Still, too much solder, but MUCH better than before!


With the brass mounting flange freshly annealed by the soldering process, I put the blast pipe in place and carefully formed the flange to the side of the boiler.


And finally, after some significant cleanup, here’s the shot of the completed Blast Pipe:


And this is what it looks like inside the boiler casing – its pointing straight up at the center of the smoke stack opening, just like its supposed to!


I still need to drill the mounting holes in the boiler casing, but it was too hot in the garage and I needed to go in for the day.

Thanks for stopping by!
Kim


Offline b.lindsey

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #798 on: September 03, 2017, 01:29:15 AM »
That looks good to me Kim, despite the initial problem with the 5/32" tubing. Nicely done!!

Bill

Offline Dave Otto

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #799 on: September 03, 2017, 03:00:32 AM »
Nicely done Kim!


Dave

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #800 on: September 03, 2017, 06:12:09 AM »
Thanks Bill and Dave!

I think I'm going to get this silver soldering thing down eventually.   Practice helps, but I still I always screw up my first attempt.  I think I have to be a little more aggressive in heating the part.  I am so focused on NOT melting things that I am too gentle with it and all the flux has boiled away by the time the parts get up to temp.

The reason I melted that part on my first attempt is because the flux had all boiled off  and things were starting to oxidize. So, when the solder finally melted, it wouldn't go down between the parts because of the oxidization.  I tried applying more flux, which helped some, but I had to do several times, and kept adding a little more solder (which I'm sure you could see).  And in the end, I fussed around with it so much, that melting that thin tubing just happened.  The second attempt, I was more aggressive with the heat, and it worked so much better.  There's a fine line between getting the brass hot enough to melt the solder, but not so hot it starts to met itself.  But being TOO gentle with the heat isn't the answer either.

I'm getting there!
Kim

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #801 on: September 04, 2017, 10:44:05 PM »
In my last update, I made a comment about the bending jig I made for the 1/8” brass tube, but I didn’t have a picture of it. Well, here it is.  I used gentle thumb pressure to bend it around the jig. When the bending got hard, I annealed the brass again.  Not high tech, but it seemed to work pretty well.



OK, on with today’s update.

I left off needing to attach the blast pipe to the boiler casing.  So, after marking the location for the holes, I mounted the unit to the mill, to drill and tap the 2-56 holes:


Then I attached the blast pipe.


From the top, it looks about right.  It’s closer to center than this picture makes it look due to perspective.


Continuing with the theme of the exhaust system, I moved next to the Exhaust Pipe.  The only real work to do here was to make the exhaust pipe flange which would help connect the exhaust pipe to the exhaust port in the cylinder.

This was just a little piece of 1/16” x 3/16” brass.  Unfortunately, I only had 1/4" wide brass, so the first step was to mill it down to 3/16” wide, like so:


With that, I cut it to length and drilled the holes.  Unfortunately, I drilled them wrong. So, having made this excellent practice piece, I repeated the procedure for the real piece, drilling in the correct locations the second time.


Then using the filing buttons, I rounded the ends of the mounting flange.


I also needed a short length of 5/32” tube to slip over the 1/8” exhaust tube – this is to help with the slip joint into the blast pipe.  Nothing of note here other than I wanted to show you my little X-acto miter box.  It’s something I picked up in past years when doing other modeling work. It’s really great for cutting this thin walled tubing or other small parts to length.


The last step for the exhaust pipe is to silver solder the pieces together.  However, since I’m out of 1/8” brass tube, I can’t do that yet.  So setting these pieces aside, I started on the Steam Admission Tee.  This will connect the steam supply from the throttle (yet to be made) to the steam chest and the displacement lubricator (also yet to be made).

The Steam Admission Tee is fairly simple.  It’s a 1/4” brass block with a 10-32 threaded rod sticking out the bottom (which will connect to the steam chest).

Here’s the 1/4" brass top of the T being made.  I drilled the bolt holes, and one steam hole in the center:


Rotated it 90 degrees, then drilled and tapped a 10-32 hole half way through.


And finally, using a short piece of 3/16” brass, I threaded it 10-32, drilled a 3/32” hole through its center, then cut it off to length:


And here are the pieces of my Steam Admission Tee:  You can see that my 3/32” hole in the center really wandered there!  I’ve heard about that from others, but haven’t see it so dramatic in my parts before!  Well, this end will go in the Tee so that you don’t see that!


And here we are, assembled.


I need to sliver solder the two pieces of the Tee also, but’s getting hot outside and I didn’t want to open up the garage doors (I like to have good ventilation when I’m using the torch.)  So, I’ll do that another time.

That’s my update for the day.  Besides the soldering on these parts, I’ve still got quite a few other parts to make for the steam supply; Displacement lubricator, Throttle, several more pieces of piping, etc. And eventually, I’ll have to get to the boiler too!  Still a long ways to go for me on this little project.  If I were Chris, it would be done tomorrow.  But I’m me, and I’ve got many months (if not years) left in this journey!

Thanks for following along,
Kim

Offline Dave Otto

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #802 on: September 05, 2017, 12:56:42 AM »
Nice update Kim!

If you don't have any pick up some solvent based white out and coat the threads with it to keep the silver solder from wicking where you don't want it.
If you already know this, well never mind then. :Lol:

Dave

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #803 on: September 05, 2017, 01:23:12 AM »
Good point Dave!  I picked up some stuff like that a while back when it came up on someone else's thread - Some stuff in a green fat-pen-looking bottle.  That should do the trick! Thanks for mentioning it.  I'll have to make sure and use that when I solder up this part.  I keep forgetting about that!

Kim

Offline crueby

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #804 on: September 05, 2017, 02:30:16 AM »
Good point Dave!  I picked up some stuff like that a while back when it came up on someone else's thread - Some stuff in a green fat-pen-looking bottle.  That should do the trick! Thanks for mentioning it.  I'll have to make sure and use that when I solder up this part.  I keep forgetting about that!

Kim
That's Nicrobraze, works great.


 I've never used whiteout, at least some versions of it turn glassy and are very hard toremove, pickle solution doesn't touch it.

Offline Don1966

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #805 on: September 05, 2017, 03:43:13 PM »
I am behind on your build Kim but just caught up. Looks like your silver soldering skills are Improving a lot. You should be getting a lot more comfortable doing it now. Nice work all the way around buddy and the tractor is starting to look sharp.... :ThumbsUp:


 :cheers:
Don

Offline 10KPete

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #806 on: September 05, 2017, 11:25:44 PM »
Hi Kim,

I don't remember what sort of torch you're using....  Twer it me, I would use an average propane torch and a small heat-trap type fire brick hearth. Pre-place the flux and bits of braze then heat it fast with a big, soft flame. Always heat the big parts, not the small ones.

Little bits like those should heat and flow in less that two minutes, probably less.

Still following and still loving what you're doing! :P

Pete
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Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #807 on: September 06, 2017, 04:03:41 AM »
Thanks Don and Pete!

I don't remember what sort of torch you're using....  Twer it me, I would use an average propane torch and a small heat-trap type fire brick hearth. Pre-place the flux and bits of braze then heat it fast with a big, soft flame. Always heat the big parts, not the small ones.

Little bits like those should heat and flow in less that two minutes, probably less.

Thanks for the tips Pete.
I'm using Oxy-Acetylene - I know it's a bit hot, but I feel I have much better control over the flame.  I have a "Bernzomatic" torch that uses MAP Pro gas, but the flame is so big that I don't feel I have any control over what is being heated, and it tends to melt the solder directly, rather than heating the parts to melt the solder.

It seems that part of the trick in silver soldiering is figuring out how to set up the parts to be soldered such that you can find a place to heat that isn't directly on the solder - some back side or underside that you can heat up.  With some of these small pieces, I've found that difficult.

With a hearth, I've had a hard time getting to the back side of a part to heat it up away from the joint.  I can't get the heat back there!

But these are all the fun challenges, aren't the? :)

Thank you!
Kim

Offline Ken K

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #808 on: September 06, 2017, 04:58:13 AM »
  For small parts, I use a sliver solder paste. There are a lot brands but I use Fusion  brazing paste. It works great, for things like soldering a 1/16", wire, to a brass plate.
 Has anyone else, use this type of solder?
 Ken K

Offline 10KPete

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #809 on: September 06, 2017, 05:18:06 AM »
O/A can be much too intense for small parts. But the same heat control must be used for any source. You're gonna need 'X' btu per... to bring a certain mass up at a given rate. Those btu want to be put in fast, but evenly and, yes, carefully. For welding, a tight, intense flame is wanted. For this sort of work, a big, soft, spread out flame is what I like. That flame will still have it's hot spot so you can well control what you're doing but the big flame gives you lots of heat from all around very quickly without having the heat get out of hand.

You mention positioning. Yep that's bear all righty. At times. And always keep the fire off the joint/flux/alloy. Heat the back sides...yep. That's partially positioning, part design, and part cussedness.

Don't forget that many assemblies lend themselves to being tied with heavy iron wire to hold the parts while brazing.

Imagination will overcome!!

Oh, to answer Ken's question: Yes, I love solder and brazing pastes. Used many types and brands over the decades and have rarely had problems. Usually of my own  making!! :slap:



 :cheers:
Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.