Month: March 2016

Sub-Compact Stump Grinder Ep. 1

I have been cutting down a lot of trees on my property, to expand the yard. The clearing of the trees has been going well, but  I needed to find a solution for the left over stumps. It became very clear to me that grinding would be the preferred method to deal with them.

I started an evaluation process, to figure out how I would proceed. The following are some of the options I considered:

  • Rental Equipment. Renting a stump grinder seems very economical at first; especially if there are only a few stumps to grind, but as the “yard expansion project” will extend over a rather long period of time, and I’ll be working on it as time and weather allows, it would become less so.
  • Hand Operated Sump Grinder. It takes a lot of effort to operate one of those, and for just a stump or two would be a good option. For the amount of stumps I have to grind, I would prefer something more mechanized. The least expensive one I could find was around $2000. A lot of money for a gas engine on a steel frame.
  • Second Hand Professional Machine. It’s a big investment. The asking price for any used stump grinder I could find was upwards of $5000. These machines are purpose built an would do a wonderful job, but it’s just not in the budget. Also, those machines are rather large, and I would not have a good place to store it when not in use.
  • 3-Point, PTO Driven Grinders. That’s the ticket! Powerful machines, using the tractor PTO, and hydraulics to operate it. But here comes to problem: My tractor! My tractor is a Yanmar SC2450. The tractor falls into the sub-compact category. Even though the tractor has a cat-1 hitch, hydraulics with a 24 hp engine, I felt all the commercially available grinders would be too big for this little tractor. The cost of purchasing such unit is prohibitive too, as they start at around $4500.

In the end, I decided to build my own version of a PTO driven stump grinder, that would be properly sized to fit my tractor. Aside from building a stump grinder that fits my tractor, It will also be the least expensive option.

First, I modeled it in 3D CAD.


I also modeled the hitch and PTO of the tractor to ensure that the drive shaft will clear the frame in all possible positions.


Some of the design considerations:

  • The frame is to be lowered to the ground for grinding. This will transmit the cutting forces into the ground, rather than into the tractor.
  • The gear box is from a rotary mower, turned horizontal.
  • The cutting disc is a compact 11 inches, as this is the largest size for my small lathe.
  • Greenteeth carbide teeth and pockets.
  • Belt drive to increase the cutting disc rpm, to make up for the small diameter disc.
  • Off the shelve hydraulics.


I’m ready to start cutting metal, which we’ll see in the next episode.

Thank you for visiting my shop.

If you have any questions, please feel free to leave a comment and I’ll get back to you.




Welcome to the shop.

As the title of this blog is Yogi’s Workshop, I felt it would be of interest to show the shop and some of the equipment. I’m still in the process of tooling up, and will be adding more machines and tools to the shop, as the opportunity will present itself.

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The Maho MH500W4 mill is the one and only mill in my shop at this time (not counting the Linley Jig Borer in the background).

The mill was made 1988 in Germany, and has a Phillips 432 controller, using standard G-code to program.

The custom enclosure was made by the previous owner, using 80/20 extrusions. It works quite well containing the mess.

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The lathe is a Harrison Model 10-AA

This lathe was made by Colchester in the UK, and re-badged by Harrison for the U.S. market.

To get the complete story and all the details see

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I will be going into more detail about each machine in a separate post, and will be posting about any future acquisitions coming to the shop.

If you have any questions, please feel free to leave a comment and I’ll get back to you.


Duclos Gearless Ep. 7

The build has reached a milestone, as it’s time to begin assembly.

First, I have a couple of sub-assemblies.

The push rod: Of note is the spring that will positively position the indexer a quarter turn every time it indexes.

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The valve chests with the valves installed.

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The valve train complete.

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To demonstrate the valve train, and the indexer, making the gearless part of the engine work, a short video:


At this stage, I just had to see if there is life in this engine.

It’s all just temporary. The engine is mounted on a piece of 2×4 so it can be clamped to the workbench. The fuel tank/carb is borrowed from an other engine. For the ignition, I’m using an ignition kit for a RC airplane engine. The hall sensor is taped and clamped in place, and the trigger magnet placed on the flywheel rim.

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Well, it’s time to give to flywheel a spin…

… and we have a runner!

It is always a relief to hear the first pop of a new engine, after all the work to get to this point. There is still plenty of work to do to get the engine finished. Next I’ll start on the governor.  After that, it will also need a fuel tank, lubricator, and a base.

Please stay tuned for more.

If you have any questions, please feel free to leave a comment and I will get back to you.



Duclos Gearless Ep. 6

In today’s episode, I’ll start with discussing the surface treatment of some of the finished steel parts. I decided to go with a black oxide finish, which I had professionally done by a local heat treatment company. Beside the aesthetics, I’m hoping to gain some corrosion resistance. Corrosion is a big concern for me, as even a small amount of corrosion will take away from the finished engine. I try very hard to use corrosion resistant materials where possible, but sometimes that’s just not economic. That’s the first time I’m using black oxide, and we’ll have to see how it’s going to hold up.

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I continue with some of what I refer to as the fiddly bits. They are small, intricate, and time consuming.

The indexer, which makes the gearless part of the engine possible, is next. The indexer is going to be part of the push rod, and will index a quarter turn every revolution of the crankshaft. I’m going to leave it at this very brief explanation, as I’ll come back to it very soon, when assembly of the engine begins.

First, I turned the material to the outside diameter in the lathe. Then, it is chucked up in a collet block, and machined on four sides on he mill. Material is 303 stainless.

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Back to the lathe, for paring off.

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…and the finished part.

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The Toggle Bracket is the pivot for the latch of the governor, and also the part that holds the push rod in place. I’m holding off with the other parts for the governor until after a successful test run.

First, I machined the contour on the mill. Unfortunately, I didn’t have a better fitting piece of brass stock, so I had to machine off a lot of material.

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Next, parting off on the lathe.

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Then, I chucked the part on the boss using a collet to clean up the second side.

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Finished Toggle Bracket.

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To conclude this episode, I have a few more pictures of finished parts:

The valve body covers. Made out of 6061 Aluminum.

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The tapered bushings, to mount the flywheels.

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The cam. Since the cam gets mounted directly onto the crankshaft, it needs twice the duration then a “regular” four stroke cam.

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Thank you for visiting my Workshop.

If you have any questions, please feel free to leave a comment and I’ll get back to you.