Author Topic: Steam Tractor 3/4" (Rudy K)  (Read 143762 times)

Online Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1095 on: August 13, 2018, 12:52:33 AM »
It's been 6 weeks since my last update, but believe it or not, Iím still focused on getting this done!  And Iím getting close!  (weíll closer than I was a year ago at least! :) )

Iíve been out camping with the family, visiting relatives and, during what would have been my shop time at home, Iíve been doing house chores.  The main one being completing a re-do of our fence.  Most of the top boards on the fence were in various stages of rotting, so I was hoping that if I replaced them, that I could get another 5-10 years out of the fence.  As it turns out, not only were the top boards rotting, but some of the rails were too. So I ended up replacing ALL the top boards, and about 1/4 of the top rails and a few of the bottom ones too, along with a handful of fence boards.


Anyway, I think it looks 1000% better and should last a few more years till I need to address it again!

So, back to the Steam Dome!

Steam Dome Cover Take 1:  From Sheet Aluminum
Actually, its back to the Seam Dome Cover.  A month ago, you all were giving me excellent advice on how I could create this piece:


I decided Iíd try to form it out of Aluminum, then make a little piece out of sheet steel to act as the spring clips, like Daveís design he posted in reply #1090 of this thread.

First, I cut a circle out of 1/64Ē Aluminum.  Then I made a pattern from wood with the appropriate radius on it.  My idea here was to attempt to pound or spin the Aluminum into shape on this wooden pattern.  To make sure it would hold in place, I put some double sticky tape on it, and then held it in place with a short wood screw.  Like this:


However, try as I might, I couldnít get the thing to shape.  The best I could do was a bit of a Pringles shape. If I tried pounding on one side, the other sides would pop up.

So I tried annealing it.  I used the soap idea to try and make sure I didnít overheat the aluminum.  But even with several rounds of heating, this is about all I could get:


I thought about going to copper, but I didnít have any.  Or trying brass.  But I decided to go with carving it out of the solid, which was another popular suggestion.  I found this route to be quite involved, but it worked, and Iím fairly pleased with the results.

Steam Dome Cover, Take 2:  From the solid
I had a short piece of 1.5Ē 12L14, and thatís what I used for the steam dome cover.
First, I cut a 1/4" flange to fit inside the steam dome column.


Then I brought another 3/8Ē down to the outside diameter of the steam dome, and started to cut if off on the lathe.  But this was hard.  It was going slow, and it kept catching and giving me a real thrill.  So, I decided to take it to the 4Ēx7Ē band saw and cut it off that way.  Very fast and much less anxiety producing!


After cleaning up the sawed face, hereís what I had:


It even fit in the steam dome column, just as designed. How cool is that?


Next, I mounted it in the mill, and went to chew out a bunch of the underside to make it fit around the throttle and what-not, that hides in the steam dome.


Once I got that done, I used a 1/8Ē mill to dig a slot for the throttle lever to poke out through. This was a little worrisome, since I had it clamped in the vice like I did.  I probably should have comped it differently, but I used this method Ė took it slow and careful, and it turned out OK.


Next, I had to figure out how to shape the dome on top.  So, I used Excel to create a step-off table for shaping it the way I wanted.


And hereís what it looked like wnen I was done with it Ė kinda ugly, eh?


But once I got done attacking it with files and some sand paper, it cleaned up really nice!


Then I realized I had forgotten to put a 10-32 hole in the top for the faux pressure gauge. So I did that:


And hereís the completed Steam Dome Cover. Top:


And bottom:


And the beauty shot with the completed steam dome in place.  You can see how the throttle level peaks up through there.




Thanks for taking a look and thanks for all the advice on making this somewhat tricky piece!
Kim

Offline Dave Otto

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1096 on: August 13, 2018, 01:14:26 AM »
Its perfect!
I was thinking to myself this afternoon, I wonder what Kim has been up to? Good to see an update.

Dave

Offline Brian Rupnow

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1097 on: August 13, 2018, 01:31:43 AM »
Kim--That's just marvelous. It looks really good.---Brian

Offline b.lindsey

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1098 on: August 13, 2018, 02:19:47 AM »
That turned out great Kim!!! Very nice  :ThumbsUp:

Bill

Online 10KPete

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1099 on: August 13, 2018, 02:47:09 AM »
While the part looks great, the real thing that happened here was that you determined the designers intent then made it into a part made YOUR way. Kims way!

I would say that you are a genuine model engineer now....

 :cheers:

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

Online Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1100 on: August 13, 2018, 05:30:59 AM »
Thanks Dave, Bill and Pete!
While the part looks great, the real thing that happened here was that you determined the designers intent then made it into a part made YOUR way. Kims way!

I would say that you are a genuine model engineer now....

Thanks Pete, and as long as I have you and dozens of other highly experienced model engineers helping me figure things out, I'm golden! :)

I couldn't do any of this without the excellent advice and coaching I get from all of you!  ;)
Kim

Offline Baner

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1101 on: August 13, 2018, 11:02:39 AM »
The dome turned out great Kim. Well done.

I've often seen the 'Excel Step off Charts' people create for machining radii on the lathe or mill but I haven't come across a good explanation on how to create one. I'm not great with Excel or Trigonometry - I don't suppose you could either explain it or provide a link to someone that has?

Thanks,

Dave.

Online Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1102 on: August 13, 2018, 07:13:04 PM »
Thanks Dave :)

I can tell you what I did - it was just a quick and dirty thing, not really fit for public consumption, but it worked for me.

I didn't really use any trig.  I do sometimes, but not this time.  Just the Pythagorean theorem.  That got me where I needed to go.

Here's what I did:
I was rounding off the end of a bar.  So one of my dimensions was the Z-axis of the lathe.  I would dial in Z, and then use the cross slide to move the y-axis in to produce a specific diameter.  But what diameter for a given Z position?

To figure that out, I used this picture where:
     r is the radius of the dome I want to end up with
     z is the distance from the end of the bar
     y is the length at the distance z from the top of the circle[/li][/list]


To calculate y, I used the Pythagorean theorem; the sum of the square of each of the sides equals the square of the hypotenuse.  In my case, the hypotenuse is the radius (r), the length of the edge I know is on the Z axis.  But it isn't actually the z value.  It's the radius minus z (r-z).  That's because I want to use the y-r triangle for the calculations, NOT the z-y triangle. Why not the z-y triangle?  Because I don't know the length of the hypotenuse for that one.

So, since I know two values, I can calculate the third.

Hypotenuse2 = Side12 + Side22

Hypotenuse = r
Side1 = r-z
Side2 = y

This gives us:
r2 = (r-z)2 + y2

Solving for y, I get:
y2 = r2 - (r-z)2  or y= SQRT( r2 - (r-z)2 )

So I just plugged that into the spreadsheet and solved for y for a whole bunch of z values.

The other thing to remember is that the y value we get is the RADIUS at that z value, and my DRO reads diameter.  So I had to double the y value. (which I also did in the spreadsheet).

The beauty of a spreadsheet is that it lets you take a formula like this and duplicate it a bunch of times for different locations.  And I could try different radius values to to get the look I wanted before I cut the metal.

That's how I did it anyway.  Is that the question you were asking?  Or were you looking for more info on the spreadsheet itself, rather than the math I used?
Kim

Offline zeeprogrammer

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1103 on: August 13, 2018, 08:51:34 PM »
Great job Kim.

A bit of dome head scratching got you a very good looking dome.  ;D
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Online Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1104 on: August 14, 2018, 02:53:55 AM »
Thanks Zee! :)
Kim

Offline Steamer5

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1105 on: August 14, 2018, 06:45:05 AM »
Nailed it!
Well done Kim.

Cheers Kerrin
Get excited and make something!

Offline Baner

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1106 on: August 14, 2018, 01:15:10 PM »
Thanks Kim. You've answered my question. It's nice to have the math explained so clearly- often explanations I come across leave me more confused than ever.
I think I'll be able to figure out how to make a spreadsheet work, but in the spreadsheet screenshot you posted I'm not sure what the third column is for?
Thanks again, :ThumbsUp:
Dave.

Offline Tennessee Whiskey

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1107 on: August 14, 2018, 03:09:54 PM »
Little late, but, awesome results Kim. You gotta be tickled with that.

Eric

Online Kim

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1108 on: August 14, 2018, 07:59:43 PM »
... in the spreadsheet screenshot you posted I'm not sure what the third column is for?

THAT, is a good question, Dave!
I don't actually have the spreadsheet with me now, so I can't look at it.  And it is a confusing column. My best guess is that the third column was an early attempt at me trying to make a graph that would show me how the 'dome' would look.  You can see that I finally got there by simply using an x-y scatter plot.  But I tried some other things early on that didn't end up looking right.  I think that may have been part of that.  In the end, that 3rd column became the y*2 column - I needed the diameter rather than the radius so that it would match my DRO.  In my plot, I used the radius and plotted +/- the radius.  But my DRO uses diameter.

Clearly, this wasn't the FINAL version of the spreadsheet.  It was just what I took a picture of.  If you're actually interested, I can give you more recent version of the spreadsheet when I get home.

But yeah, that 3rd column as shown in the picture is a mystery to me too :)
Sorry about that!
Kim

Offline Baner

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Re: Steam Tractor 3/4" (Rudy K)
« Reply #1109 on: August 15, 2018, 01:32:18 PM »
Thanks for the offer Kim, but there's no need to post the spreadsheet. I could follow the rest, I was just checking I hadn't missed anything in that column. The scatter plot was a clever idea too.
Dave.