Fluidyne Gasification Archive

Fluidyne Archive Guillotine

Simple Chip Guillotine for Round Biomass
Proof of Concept Design.

In 2001, I posted a design concept for a simple hand guillotine, to make chips for cooking stoves out of a wide range of round biomass in Developing Countries. To my knowledge, nobody tried to build one to prove the concept, so it came as a surprise to be asked at the beginning of 2014, if I had any more information to offer on this design. As my own current research involves fast growing round woods, it provided me with an interesting distraction to build one for my own application.

The key innovation of the design, is the disc blade that can be turned around six times to change the cutting edge. The body and disc blade is made from standard mild steel plate 1/4" (6mm) thick, with mounting and handle from any angle and pipe stock that retains the spirit of the design. For practical purposes, I have mounted the guillotine onto a flat plate which I can clamp to a very stable support on the end of my metal and wood cut-off saw bench, so I can hang it on the wall when not required.

If anyone would like to make a larger version with a 12" or 15" disc blade, I suggest that you increase the number of holes in the blade so all the cutting surfaces can be rotated in turn.

My tests have shown that you can cut a diameter of 1.3/8" (34mm) across a range of biomass types (hard and soft woods), with some better angled to the blade, while others are just held square to the blade. This is possibly due to the way the blade slices as it displaces the input length away from the blade thickness producing an angled curved cut, reducing the need for angled entry of the wood. The cut off piece or chunk, has very little laminar fracturing of the grain, unlike most chipping systems which tend to shatter the chunk into thin chips. The exception to shattering as normal is bamboo due to it's hollow core. While stoves like the smaller chips, if the fuel is for gasifiers, the chunky round chip has the advantage of maintaining the interstitial space more suited to gas making.

For my own needs, I have made a short trough table on each side, but these can be made to suit the individual application as required. The main moving load bearing bolts, are high tensile for long life, but standard steel bolts will be adequate if easier to replace in rural locations.

The main change to the original Mk1 concept, was to change the face plates from a jaw to a round hole Mk2 model, so that the disc blade could not thrust sideways as the cutting edges met. Also added, is a lever actuated clearing blade to remove chip residue from the back of the blade recess.

A left and right handed guillotine assembly only requires the disc blade to be reversed so the blade angle always faces the incoming length of wood.

In offering this as an alternative solution for cutting round biomass into small pieces, it is only an option available to those who might need it.

Doug Williams.
February 2014

Construction Detail.

NOTE. This is not a design that requires huge skill to make, but attention to detail and a bit of care should provide an end result to please most fabricators.

1. Side plates are made from 1/4" steel plate. All bolt holes are 7/16" diam. Use 2.1/2" hole saw for cutting port.
2. Disc blade is cut from 1/4" steel plate, and one edge sharpened with disc grinder, or lathe if available.
3. Hand leaver plate is 2"x1/4" flat steel.
4. The handle socket pipe will need to match as a sliding fit for the handle pipe. I used a 1" handle pipe socket, and 3/4" pipe handle.
5.The chip clearing blade is 1.1/4" flat steel with an approximate angle end of 35 degrees.
6. The chip clearing blade handle is 5/8" steel round bar 15" long. It can be crank bent L-R either side to suit.
7. The mounting base angles are 3"x2"x1/4" and two are required.
8. The link bars are 1.1/4"x1/4" flat steel. two or required. Fit flat spacer washers outside of and between link bar each side of disc blade.
9. The 1.1/4" flat steel blade stop length needs to match the final assembly to prevent blade hitting the side plate pinch bolt.
10. This spacer is 1.1/4" flat steel to fit between the side plates of the rear base bracket mounting hole.
11. All the moving load bearing bolts are high tensile with a plain shank for part of the length, fitted with Nylock self locking nuts.
12. Use some grease during assembly and don't over tighten the moving parts.

Base plate with angled pedestal mountings for trays.
All finished components for guillotine.
View of moving parts.
Chip clearing blade in clear position.
Finished Mk1 guillotine. Hard testing showed change required to side plates.
Mk2 guillotine testing  maximum cut of1.3/8"  coppiced poplar.
View of  ground disc blade edge done with 4" hand disc grinder.
Mk2 guillotine finished with short support trays for specific application.
Cutting coppiced poplar shows how natural angle of cut evolves as the blade slices the wood.
Cutting bamboo results in shattering due to the hollow centre.
Bamboo cuts fairly cleanly without long fibre feathering of the ends.
A handful of coppiced poplar shows the chunky round fuel of a size ideal for gasifiers.
Once cut, these coppiced poplar chunky chips need to be dried and not stored wet.