Chris's Un-Ransome Tree Feller

[bent]

That's AWESOME!  Good job Chris!
 

And...finished in plenty of time to carve the Thanksgiving turkey!  Imagine the surprise for your wife and guests! 

[Dave Otto]

Nice work Chris!

Dave

[Kim]

Very exciting, Chris!  The first run of your little Elf Chopper!   

It has quite the vibration going.  So, how fast would they have run those saws anyway?  Seems like it would have been quite slow, like 60 to 120 RPM or something? 

Kim

[crueby]

Thanks guys!

Kim, I would think they would be on the slower side, since they were moving a big 4 or 6 foot long large blade back and forth through a tree, so would not run anywhere near the speeds we run something like a sawzall or saber saw these days, with a 4 inch blade. The speed I have it running in the video would be about the max, I am guessing, and normally slower than that.

[mklotz]

Congratulations, Chris, to another landmark in your inspirational working model making.

I'm still having trouble grokking how that valving works.  Is there a website somewhere I can use to improve my comprehension?

[crueby]

Congratulations, Chris, to another landmark in your inspirational working model making.

I'm still having trouble grokking how that valving works.  Is there a website somewhere I can use to improve my comprehension?

Hi Marv,
I don't know of any websites that show how they work, it took me a long time to figure it out years ago. Here are some cutaways of the way I am doing it in action, hope this helps. Explanation of each step under each picture.



In this first diagram, the control valve, dark blue, is all the way to the left. It is in this position when the cylinder is all the way to the right (the valve link bars reverse the motion). Both the upper and lower steam chests get steam from the same source. With the control valve all the way to the left, the port underneath on the right is exposed to steam, and the port on the left is connected to the exhaust port (with the black circle in it). This sends steam down and around to the end of the shuttle piston, shown in pink. This pushes the shuttle piston, and the cylinder D-valve (light blue) over to the left end, stopped by the end plate. This sends steam from the lower chest into the lower port on the right, which connects to the right end of the main cylinder, pushing the piston and saw blade off to the left.




In the second picture, the control valve is moving off to the right again, as the main piston and saw blade are in motion. Notice that the shuttle piston (pink) and main D valve (light blue) are still at the left end, there is nothing to move it since both of the ports controlling the shuttle piston are exposed to the exhaust in the passages above it.


Finally, in the third picture, the piston/blade have made it most of the way to the left end, and the control valve (dark blue) has moved far enough to the right to expose the left passage to steam, sending steam down the left passage to the left end of the shuttle piston, moving it and the main d valve all the way to the right end. This sends steam from the lower steam chest down to the left passages, leading to the left end of the cylinder. This will stop and reverse the piston, sending it back to the right end again, where the whole cycle repeats itself.
The key to the whole thing is that while the upper control valve is moving, the shuttle valve below it stays where it was, then when the control valve gets far enough to send steam to the other end of the shuttle valve, the shuttle valve snaps over to the other end. This is very different from normal eccentric-driven steam engines where the main d valve is always moving as the eccentric spins. Here, the valve is at one end or the other, except for the very brief moment when it snaps across.

Hope that helps explain it all. Not my invention, the shuttle valve is old tech, I just took a different approach to the linkages on the piston rod - many old feedwater pump designs use some combination of stops to snap the control valve back and forth, I made the control valve longer so it could be moved slowly by the piston rod while keeping the motion on the main valve sudden.
Chris

[mklotz]

Many thanks for that, Chris.  I had it in my mind that snap action was needed but I hadn't realized that there is a slave piston with its own valving supplying that motion to the valve controlling the sawblade piston.  Those steam engine era engineers were very clever.

FWIW, I extracted your images and the associated text and, using Irfanview, made three files, STEP1-3.  If anyone wants copies of these files, drop me a PM with your email addy and I'll pass them along.

[crueby]

Many thanks for that, Chris.  I had it in my mind that snap action was needed but I hadn't realized that there is a slave piston with its own valving supplying that motion to the valve controlling the sawblade piston.  Those steam engine era engineers were very clever.

FWIW, I extracted your images and the associated text and, using Irfanview, made three files, STEP1-3.  If anyone wants copies of these files, drop me a PM with your email addy and I'll pass them along.

Great! Glad it helped out.   

[crueby]

This afternoon I got the gaskets made for the steam chests, and lapped all the valve faces so they seal well and move smoothly. All re-assembled now, and adjusted to run again (while disassembled one of the adjusters spun). I'm glad I put in both the adjuster on the long link rod as well as the needle valve on the air supply, really helped in the tuning process. The needle valve I am using is made as a shutoff/flow control valve for things like icemakers on refridgerators, available in the plumbing aisle at hardware stores. Very handy for times when it doesn't matter what they look like.

So, here is a new video, this time with the cylinder held in a large (for my tools. Might be the smallest size some of you have!) machine vise so I could hold the camera and also operate the needle valve to start it and control the speed. I am Very happy with how its running in this configuration, never got the first version to run more than 1-1/2 strokes!      

<a href="https://www.youtube.com/watch?v=CxNw6oPu9eA" target="_blank">http://www.youtube.com/watch?v=CxNw6oPu9eA</a>

No shop time tomorrow, combination of friends over with our final pond run of the season with the RC boats. Monday I'll start on the base frame to hold the cylinder.

[samc88]

Cool project, so are you going to cut down some Bonsai trees with the model one?

[crueby]

Cool project, so are you going to cut down some Bonsai trees with the model one?

    great idea!

[Admiral_dk]

Great to see it running so well 

Now I wonder if the original Ransom system would work if it had a Slave system too 

Per         

[crueby]

Great to see it running so well 

Now I wonder if the original Ransom system would work if it had a Slave system too 

Per         

Hmm, very possible! It would still be different than the way Ransome patented their valve system, but possible.

[Michael S.]

It was a good idea to build the saw with this control.
It's similar to the simplex feed pump that I've seen on steamships.
I'm looking forward to someone shouting: Watch out for the tree falling!

Michael

[ozzie46]

  Actually that's "TIMBERrrrrrrrrrr"!

Ron