Author Topic: Steam Tractor 3/4" (Rudy K)  (Read 242001 times)

Offline AOG

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #930 on: November 19, 2017, 05:44:16 PM »
Leaving aside the safety issues, I would still test water because it is easier to trace any pin holes you might find.

Tony

Offline crueby

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #931 on: November 19, 2017, 06:12:42 PM »
Definitely go with water - safer AND easier to see leaks, even minor seepages show up as single growing drops that would be hard to find with air. The little ram-type pumps fumopuc showed are available from a variety of sources, they work very well for testing as well as replenishing the water as you are running an engine. With the boiler full of water, along with the line from the pump, it only takes a few strokes to run up the pressure. I used that type to test up to 180psi on my boilers.

Offline b.lindsey

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #932 on: November 19, 2017, 07:26:20 PM »
Another vote for water Kim. Your start on the boiler looks wonderful!!!

Bill

Offline Don1966

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #933 on: November 19, 2017, 07:52:24 PM »
I vote for water also Kim. But I don’t see any danger of air as the amount of volume you have is very little so I din’t See it as any real danger. Water doesn’t give with pressure and when a leak occurred no pressure is released and is instantly gone, where as air can be compressed and releases pressure for a time so water is less dangerous. Looking good buddy.


 :cheers:
Don

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #934 on: November 19, 2017, 10:39:57 PM »
Thanks for the input Achim, Tony, Chris, Bill, and Don,

I do appreciate the input and advice.  Certainly, lots of support for the hydro testing.

As for 'seeing' the air leaks; this boiler is small enough that I believe the idea is to submerge it in a bucket of water and see if any bubbles come up.  That's how I always found small leaks in inner tubes when I was a kid.  Seems like it could work here fairly well.  Assuming that 60lbs isn't overly dangerous for this method.

Any support at all for the 'under water air testing?'

KIm

Offline MJM460

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #935 on: November 20, 2017, 01:53:14 AM »
Hi Kim,  certainly the full size practice is at least in part due to the possibility of brittle fracture in steels, it is certainly to do with crack propagation which on a large vessel is really catastrophic, though not really applicable to copper.  A proper hydro test in steel actually "bluntens" a crack, if it does not fail, and actually makes propagation less likely for future pressure cycles. 

On your copper boiler, I think the danger is more likely to be due to a soldered in bush with poor penetration that fails the on the test.  It raises the picture of a bush flying around like a bullet with all the energy you've stored in the air by using that pump behind it.  With water, the compressibility is minimal, so the stored energy is low, which you know by how few strokes of the tiny feed pump it takes to get the pressure.  And you can be sure that most of those few strokes are necessary due to a small bubble of air you were unable to displace with the water.  More than about 1 stroke is a definitive indication of either air, or a leaky pump valve.  You can easily work out the volume change of the water using the liquid specific volume column of the steam tables, there is no mystery to it.

So, while we are on full size practice, the usual recommendation for that preliminary leak test, a good idea on a very large steel system, is a very low pressure air test, with either soap bubble mix for a large system, or submerging in water where ever practical.  Even my multi million dollar compressor casings are submerged for this test, it always pains me to see it as the water in an unpainted steel tank never looks clean even, and they go as far as to use helium instead of air.  The molecules are smaller, so it is a very much more sensitive test.  Perhaps we have a use for those helium filled party balloons after all.  And the pressure used is very low, 5 to 15 psig, preferably a time at each of several different pressures over the range.  It has been found that higher pressures can temporarily close a leak so it is not detected, but still shows up later.

There are circumstances where it is necessary to use a pneumatic test for full size vessels, it is approached with great care and is never as high as a hydro test which in full size is normally only 1.5 times, I think from memory, 1.25 times for pneumatic tests.  The hydro test pressure is increased to compensate for the difference in material strength for high temperature vessels to 1.5 times the allowable pressure for a new and cold vessel.  That is where the two times design pressure for our model tests come from.  But the circumstances for a pneumatic test do not arise in model scale, so you would not get approval from the authorities for a pneumatic test in that size vessel in industry.

So you might gather that I am another vote for a hydro test, not air.  You will eventually want a pump anyway, so make one with a manual handle that could be converted to axle driven, or gear driven for your tractor.

A great build, beautifully documented by the way, another of my "must reads" at every update.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #936 on: November 20, 2017, 02:19:24 AM »
Thanks for the detailed info on full-sized testing, MJM.  Very interesting.

Sounds like the wisdom of the group is pretty unanimous, so I'll be figuring a way to do a hydro test.

And it all does make sense!  I just worry about what I'd have done if I was just following along with the instructions in Rudy's book without the benefit of the wisdom of this forum.

Again, thank you to each of you for sharing your wisdom and experience with me, yet again, to help keep me safe and having fun with this hobby!
Kim

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #937 on: November 20, 2017, 02:49:35 AM »
Today, I made the Longitudinal Stay, and started the end caps.

The stay is quite simple; a piece of 1/8” copper rod, threaded at both ends.

After cutting, I faced off the end:


And threaded it 5-40.


Here it is. Not very hard :)


Next I started on the end caps. First I laid them out on the copper, trying to waste as little of this expensive sheet as possible!


I drilled the 1/8” center hole on the mill.  This will be for the longitudinal stay,


Then I went to cut them out on the scroll saw.  Cutting the 1/8” copper sheet took a long time. It’s just slow going. The metal blades are very thin, and if you try to push a faster cut, the blade will break.  I broke one blade after 1/4", the next blade I made 2.5” and the final one, I completed all the rest of the cuts.  So I can learn!  These are good Vallorbe blades, so they seem to be up to the task, as long as I treat them well!


And here’s the end caps freed from the parent stock.


And it was time to come in for the evening.  Not a lot accomplished, but I’m taking a few days off this week before Thanksgiving, so hopefully, I’ll get a little bonus shop time this week!  Pretty excited about that!

Kim

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #938 on: November 21, 2017, 01:18:20 AM »
Yes! I got some bonus shop time today!  So, I continued on with the boiler.

Yesterday, I’d left off having just cut the end caps.  Now I needed to make them round.

I went with the LocTite mounting using a piece of 1” steel rod.  I used the center through the 1/8” holes to help center up the coper blank, then used it to hold some pressure on the assembly while the LocTite was setting.


Here’s the other side:


After the LocTite set, I placed a piece of 1” rod between the live center and the copper to help distribute the pressure.  Don’t know if this was needed, but it felt like a good idea.


Then I cut the disk down to the appropriate size to just fit in the end of the boiler tube.


After turning down both end caps, I took one of them to the mill to drill the holes for the end bushings.  I’m using a 60 center to align to the center of the copper plate to set the DROs.


After dialing up the right spot for the first hole, I used my favorite center to start it.  Then I hear a ‘SNAP’.  The tip of the center snapped right off in the copper!  Guess that stuff IS grabby!  I hadn’t had any problem up till now :(


So I sat back for a few minutes to think about what to do, and came up with this – I’d try using a little ‘donut cutter’ like I’d done to take a broken drill bit tip out of the outer boiler casing (if you recall when I was having all THAT drama a year or two back).  Turns out, I didn’t even need to make a new one. The one I already had was just the right size!  How lucky was that?


And it worked like a charm.  I was really careful, went slow and used some cutting oil. It seemed to go fine. Only problem now is that I can’t get the copper plug out of the plug cutter. But I decided to deal with that later.


After that mishap, I went about drilling the two 1/2" holes in the end cap.  Again, I stepped up from 1/8” to 1/2" (by 1/16ths).


After that, I worked on getting the copper plug out of the plug cutter.  I was able to do it using a tiny drill bit (#55) and made a very short hole in the copper,  Then I took a #54 bit (just a wee bit bigger) and twisted that, by hand, into the #55 hole in the soft copper just a smidge, and used the #54 drill bit to pull out the plug.  It worked surprisingly well!

And here’s the fruits of my labor today, including the plug cutter, showing the copper plug after it was mostly pulled out.


I’m a few steps closer to a boiler!
Next up is the bushes and the boiler tubes.  Then I can start silver soldering it all together!

Kim

Offline 10KPete

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #939 on: November 21, 2017, 01:28:19 AM »
See, I told you that tool should be carefully put away for future events!!!   :old:

I don't see any signs of lube in those pics. You are using some, aren't you? I've used butter with excellent results. It only takes a trace to make the difference.

Pete
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SB 10K lathe, Benchmaster mill. And stuff.

Offline Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #940 on: November 21, 2017, 02:32:42 AM »
Yes Pete!  And you were so right!

Yes, I'm using some of my standard stuff, I think its Magic Tap (general purpose cutting oil).  That's what I use unless I've got something more specific (Viper for single point threading steel, A-9 or WD-40 for Aluminum).

I blew away the chips before the I took pictures, which dispersed any cutting oil.  But I brushed some on for every cutting operation.  Including the scroll saw that I did yesterday.  It seemed to help significantly.  Still had to clear chips a lot -that copper is really sticky!

Now, do you use real, full fat butter?  Or margarine? I'm pretty sure the only thing we'd have in the house is some kind of heart healthy omega-3 infused margarine!  Wouldn't want to clog the arteries on the mill!   :Lol:

Kim

Thanks Pete!
Kim

Offline crueby

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #941 on: November 21, 2017, 03:10:21 AM »
Yeah, copper is funky stuff, light cuts, oil, and it still seems to grab chips and tries to weld it back in behind the cutter.

Offline 10KPete

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #942 on: November 21, 2017, 04:03:26 AM »
Well now, that's a good question, Kim. I don't think I've ever had anything other than butter around here. So good old salted premium full on butter.

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

Offline Steamer5

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #943 on: November 21, 2017, 08:25:18 AM »
Pete,
 Plus 1 for real butter!

Kim,
 Looking good! Just catching up, good choice on the hydraulic test.

Cheers Kerrin
Get excited and make something!

Offline Stuart

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #944 on: November 21, 2017, 10:34:28 AM »
Full fat cows milk is the best for copper
My aim is for a accurate part with a good finish

 

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