Author Topic: My scaled down version of the steam traction engine "Minnie"  (Read 6300 times)

Offline Zephyrin

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My scaled down version of the steam traction engine "Minnie"
« on: March 13, 2019, 11:26:42 AM »
I think I've already mentioned the misfortune that happened to my little steam tractor...
Made in 2001, this small model is at 1/19 scale, a reduced down version of  “Minnie”, from the Len Mason’s book. Hence my farm traction engine is pretty small, and was built on the small Emco Unimat SL1 lathe. The rear wheels, with a diameter of 100mm, were the maximum for this little lathe, with a riser under the headstock of course!
But unfortunately, my "home-made" wheel foundries made of unknown alloys have not withstood the passage of years, because of the "Zinkpest", in a few years the wheels became swollen and disintegrated then fallen to bits!
I don’t mix anymore recycled metals for casting now…
I have just finished the overhaul: mainly a front wheel and a rear wheel completely redone; 
I first machined rear and front wheel rims from good quality aluminium, and recycled the old brass parts of the hubs, and the steel spokes and rim irons (strakes ?), in good condition.
Then spokes were screwed on the hub and riveted on the rim. The 2 rows of spokes on the rear wheel were pretty tricky to rivet, as the visible part of the rivet head is the crushed one…

This tractor is now in good shape and runs very well with a small air compressor.
In accordance with the prototype, the absence of differential gears on the rear wheels makes the turns difficult, as well as the gear shifting without synchromesh, which makes the gears squeak a little...
The steam test will follow, as I have to fix first the broken water level and to change the butane filling valve.


https://photos.app.goo.gl/jAunaSNrpXePn9zT8
Some pictures of this repair:

Offline gbritnell

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #1 on: March 13, 2019, 12:39:39 PM »
Beautiful job on the mini Minnie. Excellent rebuild on the wheels.
gbritnell
Talent unshared is talent wasted.

Offline b.lindsey

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #2 on: March 13, 2019, 01:46:00 PM »
Great to see the little Minnie restored to her former glory. Very nicely done on the wheels too!

Bill

Offline Kim

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #3 on: March 13, 2019, 03:41:32 PM »
Very nice little traction engine!  Those old wheels do look like they have seen better days.  Nice rebuild on them!

And thanks for showing us your riveting tools.  I enjoy seeing how people do that.  I struggled for some time to get my rivets to look tolerable.  You'res look great!

Kim

Offline Ye-Ole Steam Dude

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #4 on: March 13, 2019, 05:07:23 PM »
Hello Zephyrin,

That is so cool watching that little dude run over everything, beautiful job. :ThumbsUp:

Have a great day,
Thomas

Offline Roger B

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #5 on: March 13, 2019, 05:10:50 PM »
Splendid and so small  :praise2:  :praise2: Awaiting the live steam video  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline scc

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #6 on: March 13, 2019, 05:14:20 PM »
Proper Job!            Terry

Offline yogi

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #7 on: March 13, 2019, 07:58:48 PM »
Beautiful little engine!  :ThumbsUp: :ThumbsUp: :ThumbsUp:
 :popcorn: :popcorn: :popcorn:

Offline Admiral_dk

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #8 on: March 13, 2019, 10:00:29 PM »
Great rebuild of a nice model - glad to see that you got it running again  :praise2:

ChuckKey

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #9 on: March 14, 2019, 01:53:27 AM »
as well as the gear shifting without synchromesh, which makes the gears squeak a little...

A super little engine. But it cruel of you to engage gears with the engine running. The "Modern Manual For Drivers of Steam Road Vehicles' contains a photo
of a full size engine upside down at the bottom of an embankment. The caption says "Do not change gear on the move!"

Offline Zephyrin

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #10 on: March 14, 2019, 08:01:25 AM »
Thanks for the comments, very appreciated!

As regards the rivets (1mm dia copper rivets with 1.6mm head), the riveting of the strakes on the rim was fast and easy with a rivet squeezer I did last year, the outside part being filed flush after. On the opposite, it takes ages to rivet spokes on the rim as my rivet squeezer was much too large to enter between spokes !
I did not show the second part of the riveting tool, on the underside, where the rivet head sat. It is a sort of anvil made in a plain steel block with a half-round hollow of the same size of the rivet head (with the dremel). the shape of this tool allows to reach recessed parts and is steadily fixed on the base !
once the rivet has entered (from underside !) through holes in the spoke and rim and its head is well positioned on this bucking tool (whew !) and the job stable on it, forming the head on the front face is easy with the 3 riveting tools shown. 


Quote
But it cruel of you to engage gears with the engine running.
I fully agree with that, I don't get how to change gears without clutch !
I have to stop the engine before, I'll try do that next time.
Similar problems holds true for driving in the absence differential gears on the rear wheels, simply 2 pins to engage or not in the hub of the rear wheels, to facilitate turns...not that easy to master.


Offline MJM460

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #11 on: March 14, 2019, 11:02:45 AM »
Hi Zephryn, what a beautiful little traction engine, and running so well.  Looking forward now to seeing it on steam.

It was a pity about the original wheels, but I expect that is part of the learning when you start exploring castings.  I have heard of those effects of zinc in the mix, but would not have anticipated it to be so dramatic.  You have made beautiful replacements.

MJM460

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

Offline Zephyrin

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #12 on: March 15, 2019, 09:23:56 AM »
Thanks MJM...
Wheels were changed into dust in 8-10 years.
Yes it was my first castings, and no help from forum when I built this engine...
The amount of knowledge we can gather over here is amazing !

I don't need an air compressor, as I simply pull the engine backwards to see it running forwards...

https://photos.app.goo.gl/nVw8Xsdp6TZxKa6V6

I did a short steam test, inside the house, rather hectic, the tractor runs much too fast and leaves oily tracks all over !
It is very hard to reduce the flame, as I can't see under the boiler, and I burn my fingers.
I needs practice before I can shoot a video, outside.




Offline Zephyrin

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #13 on: March 19, 2019, 10:35:26 AM »
I have repaired everything, and my small tractor now runs well on steam, but is difficult to control, the steering is difficult on my small terrace, except to make small boring circles;
He's been out in the plant beds a little bit more than a few times !
I think it's just too fast; and adjusting the burner while it's running is difficult without seeing the flames, even with a small mirror!
The cable unwound from the drum and twisted around the rear wheel, blocking the tractor cleanly. And I lost the little lanterns in the garden, but found them thanks to the videos, as I saw where they were lost !

In short, not everything is yet under total control, or nothing is controlled, but I'm quite happy with it.

« Last Edit: March 19, 2019, 06:19:20 PM by Zephyrin »

Offline Ye-Ole Steam Dude

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #14 on: March 19, 2019, 11:20:20 AM »
Hello Zephyrin,

What a wonderful job you have done with this Traction Engine and the video is so entertaining to watch. You must be very pleased.

Have a great day,
Thomas

Offline ddmckee54

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #15 on: March 19, 2019, 04:03:48 PM »
2 speed transmission in the works?  You've really nailed the sprinting speed, now you need a comfortable walking speed option.

Don

Offline Kim

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #16 on: March 19, 2019, 05:31:08 PM »
It runs well!  It seems that these little traction engines all run fast, but you seem to have it handled :)
Congratulations on running it under its own power!  That's a great accomplishment!
Kim

ChuckKey

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #17 on: March 20, 2019, 01:40:57 AM »
Does it not have a regulator (throttle) valve?

Offline MJM460

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #18 on: March 20, 2019, 09:20:10 AM »
Hi Zephyrin, congratulations on getting it running on steam, a great achievement, to be pleased with it is somewhat of an understatement, I would be delighted, or over the moon.

A few posts back, if I understood correctly, you can run it forwards on air by pulling it backward when in gear, so compressing air in the boiler?  Even more impressive.  You are surely a master at these small machines.

 MJM460

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

Offline Zephyrin

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #19 on: March 20, 2019, 09:55:24 AM »
thanks for the comments, very appreciated !
as everyone has noted, my tractor runs much too fast...even at low gear as in the video!

Yes, it do have a regulator, a sliding valve like its larger model, but not as convenient as the needle valve I put on my G1 locos...
the other point is that as soon as I stop the tractor, the idle engine speed raises to tremendous level, and risky for all these little parts, so I closes the regulator, and steam pressure get higher...making the re-start more difficult.
I clearly need a convenient way to regulate the burner.
but, as I know it works, more probably I will leave it as it is on a shelve, with a few paint touch-up...

MJM, yes, pulling it backward raises air pressure in the boiler...
I put a small spring on the steam valve to keep it tight on the port face, hence the engine becomes reversible.
Adiabatic processes I assume, but I have no way to determine precisely changes in pressure and temperature of the air !

Offline MJM460

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #20 on: March 20, 2019, 10:44:13 AM »
Hi Zephyrin, I suspect the little spring is the secret to holding the slide valve against the face to get the air compression started, however, as soon as the air pressure starts building in the boiler, the air pressure will hold the valve against the face, just as when running as an engine.

Compression in a reciprocating compressor is approximately adiabatic as you suggest, just as the expansion when running as an engine is approximately adiabatic.  If you had a pressure gauge on the boiler, it would show the pressure, just as it does for steam, but I guess a gauge would be a bit impractical on such a small machine.  At least it would look out of scale.  The temperature of the air will increase on compression, but the boiler surface area will help it cool back to atmospheric temperature.  You can demonstrate this with a bike pump if you put your thumb over the outlet and push in the handle to compress the air trapped in the pump.  And of course we all know how hot the cylinder of our air compressor can get.

Also interesting problem, how to control such a small plant.  As you say, if you just throttle the steam, you have not decreased the energy input, so the pressure just rises.  Throttling alone is a short term control measure.  However, I wonder if that slide regulator would be easier to use if it had a screw actuator so you could make quite small movements to find a position where forward speed on load and unloaded speed in neutral we’re both acceptable.  But nothing needed on the shelf, just things to ponder for the next model.

I think that machine deserves a place of pride on the shelf.  It is a great tribute to your skill, both as an engine and as a compressor.

MJM460

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

Offline b.lindsey

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #21 on: March 20, 2019, 12:56:17 PM »
Thanks for the latest video. Quite an amazing little engine and just a beautiful restoration job all the way around!!

Bill

Offline Zephyrin

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #22 on: March 21, 2019, 09:51:33 AM »
Thanks for these kind words...
the point is that as soon as the tractor is running, it reaches lawn or flower pots before I have time to turn steering wheel, set the regulator, the butane valve, the gears, the brake, and the whistle too ! I have to move for a much larger plot !

Offline fidlstyks

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #23 on: September 09, 2020, 09:31:06 PM »
I see it has been some time since this post was active. I wanted to advise that even new potmetal falls apart. I read some where that in the old days they heated the castings and dipped them into shellac or other sealers. They then looked like metal but the air was kept out enough that parts lasted 75 years anyway.

Offline Zephyrin

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #24 on: September 10, 2020, 08:27:52 AM »
Ok, that could be a good tip, but I'm not sure if isolating the metal from the air is enough to prevent this corrosion, I'm not good enough in chemistry. and 75 years, hum, it's not that long... 
But everything is fixed now, and I've learned not to make foundries with all the leftovers of the scrap bin.

Offline scc

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Re: My scaled down version of the steam traction engine "Minnie"
« Reply #25 on: September 17, 2020, 09:57:45 PM »
Hi Zephyrin,   Only just seen the video of this little beauty running on steam.  An excellent result.......Well Done :cheers:        Terry