Automatic Chestnut Roasting Machine

The chestnut is an awesome autumn snack. It can be served cooked, in water, but it has the best flavour when being roasted.

For years we have been roasting chestnuts on a stove in a pan. But there are a few problems with that. Since you need to roast them pretty heavily, a lot of smoke is produced when the shells start to smoulder and despite using a kitchen hood vent, the whole house will smell :)

So roasting is best done outside.

But there is another problem. In the autumn the weather is cold and you don't want to stand outside by the stove for half an hour, freezing and roasting chestnuts while others are inside on a warm couch and drinking tea :)

So I made an automatic chestnut roaster what you set up and leave for half an hour outside and then you just come and collect the perfectly roasted chestnuts.

Here you can see the youtube video showing the build and functioning of the machine, but in this instructable I will further describe the details:

Skills and Tools

You need some basic welding skills and you need to know how to use basic metalworking tools like angle grinder.

You don't need anything fancy. I welded it with an old transformer type stick welder and a 25 year old angle grinder and it came out nicely :)

The AC Motor: https://bit.ly/3dac137

110V version on Amazon: https://amzn.to/3enNqbP

The Gas Burner

You will need a gas burner.

This is the first thing you need to find since the drum size will depend on the burner dimensions.

I found a nice glow type burner on a garage sale. It was never used, but it was made in the 70s. It was a part of a small gas powered grill.

This burner type has some advantages and disadvantages.

The biggest advantage is that it has very even spread of heat. The biggest disadvantage is that you can not regulate the flame intensity. It has only two settings. (on or off ).

If you use a standard gas burner - hollow tube with holes , where you get many little individual flames, you will be able to regulate the fire intensity and you will be able to simplify the build a little as you will see in the following steps.

Both burner types work well for the application. Just find the one of the right size.

The Drum Material

The drum is the most important part.

Ideally you want to make a drum from a stainless steel wire mesh (perforated sheet) which is quite thick, so it will be easy to weld. And it needs to have quite big holes, so a lot of heat will pass through and onto the chestnuts.

I found a scrap piece of this mesh for free which was perfect for my build.

You want stainless steel for the drum because it is constantly subjected to high temperatures. Regular steel will quickly rust and it is difficult to clean rust from the drum every year.

If you can not find a mesh like this, you can go to the local scrapyard and take the drum out of an old washing machine and cut it to get sheets of perforated steel. The sheets will be quite thin and a little bit harder to weld but I say many people did it with great results.

Cut the sheets into two parts - the smaller one will be the door and the larger one will be the rest of the drum.

The Drum Sides

You will need to close the sides of the drum. Also use stainless here.

I went to a machine shop and they cut two circles out of a stainless steel for me. They had some scrap pieces of 2mm stainless which is way too thick but the thicker it is, more easy it is to work with it.

You can also cut it by hand with an angle grinder, the drum does not need to be dead centered but the closer you can get to it the better the outcome will be.

Bending the Sheet Metal Into a Drum

The perforated metal I got was quite thick so I needed to work hard to bend it into shape.

I first pre-bent the sheet on a piece of similarly sized tree log and then I tap welded it on the side plates.

Then I used the straps to press the sheet onto the sides and slowly tap welded every few centimetres.

Since I don't have a MIG welder, the thick material helped me to make decent welds with my stick welder-

The Drum Doors

I welded some stainless steel hinges directly onto the drum and I use a clip for locking the doors.

i also welded a thin piece of metal wire to the door to serve as a handle. It is far away from the burner so it does not get hot and it is safe to touch.

The Drum Shaft

I welded a stainless steel rod through the drum for the shaft.

On one end I made a simple T shaped connector for the motor end and on the other side I made a holder for a wooden handle. More on this later.

The Frame

I welded a simple frame to hold everything in place.

Since I used a gas burner which did not have an option to regulate its power, I made the frame slightly more complex, which allowed me to adjust the height of the drum above the burner for heat regulation.

I also added an option for sliding the drum front-to-back for positioning the chestnuts directly above the burner. Since the drum rotates, they are not directly at the bottom of the drum and I wanted to have the flame where the chestnuts are.

I do not have many pictures of this, for some more details see the video on the top on the instructable.

The frame is made from mild steel and I painted it with a high temperature resistant spray paint.

The Electric Motor

You need something to rotate the drum very slowly.

I bought cheap AC geared motor from Banggood:

The AC Motor: https://bit.ly/3dac137

110V version on Amazon: https://amzn.to/3enNqbP

It rotates 2.5 revolutions per minute. This is the slowest speed and it is just perfect for this application. It directly drives the drum shaft.

I mounted everything in a metal box and added an on-off switch and direction reversal switch (so you don't need to wait a full minute if you accidentally missed the doors passing by for inspecting what is inside)

Motor Coupler

I made a simple coupler which receives the T shaped end of a drum shaft. it is bolted onto the motor shaft and it transmits the power from the motor onto the drum directly.

It has a slightly oversized hole so the drum shaft can be inserted and taken out with ease.

Wooden Handle

Wooden handle started its life as a hammer handle. I drilled a hole through it and it is slid on the shaft. On the other side it is tightened with a nut.

I welded a pin on the shaft which prevents the handle from rotating on the drum shaft. The handle needs to be stable, so you can easily shake the roasted chestnuts out of the drum.

Wood is also an insulator and it keeps the handle cool to touch.

The Shaft Support

I didn't use bearing for supporting the other end, since the motor is powerful enough.

Just a piece of steel welded on the frame on which the shaft sits.

I welded a piece of metal rod on the shaft between the drum and the handle which prevents the shaft from moving too much in axial direction which could cause it to slid out of the motor coupler on the other end.

The Tumbler Addon

I welded another stainless steel rod inside the drum, approximately 1cm away from the drum mesh.

When the drum rotates, the chestnuts will only slide on the smooth bottom of the drum and only the bottom ones will be roasted. They will not be tumbled enough.

This rod pushes the bottom chestnuts away every rotation and the next ones are exposed to the heat so all of them are roasted evenly.