Builder’s Manual And User’s Guide

Promoting Private SectorDevelopment in AgricultureRocket brick stoveBuilder’s ManualandUser’s GuideGIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke1

Rocket Brick Stove: Builder’s Manual & User’s GuideConstruction of the rocket brick stoveIntroduction to rocket stove technologyThe rocket stove is a new improved firewood-efficient cooking stove for households. It isdesigned to reduce the firewood needed for cooking and minimise smoke in the kitchen.The rocket stove can be made out of fired clay bricks or good clay soil. In places wherethere is no proper clay for the construction of mud stoves, good red soil which is stickycan be used, although it comes with high maintenance.For long-lasting quality and minimal maintenance, fired clay bricks, cement and limeare the best materials to use. They are available at comparatively low cost even in ruralareas.Advantages of the rocket stove Highly efficient combustion (saves about 60% of firewoodcompared to open 3-stone fire), therefore a significant savingof firewood.Reduces smoke in the kitchen dramatically, due to propercombustion.Fast cooking — the temperature below the pot is about600 C, compared to 300 C for a pot sitting on a 3-stone fire.Long lifespan of stove.Various pot sizes can be used.The stove’s main component is the combustion chamber. It also has insulation tomaximise thermal efficiency, and a built-in brick skirt which increases heat transfer to thepot. The extra air inlet brings oxygen for the firewood to combust completely. Since therocket principle reduces smoke dramatically, no extra chimney is necessary.2GIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke

The Rocket PrincipleThe Rocket PrincipleSmall door encourages theuser to economise on fuel.Smaller sticks burn moreefficiently.Small door also limits theinflow of cool air (cool airlowers the temperature inthe combustion chamberand decreases efficiency).Combustionchamber increasesdraft so that the air(oxygen) is drawnin for more efficientburning.Air (oxygen) passingthrough air inletimproves air-to-fuelratio for hotter burning.Parts of the rocket stoveCompare and see how the rocket principle works in practice. The combustion chamber ensuresgood draft. By insulating thecombustion chamber to maintainmaximum heat, the height can beshort and contained entirely withinthe stove.Skirting allows thepot to sink at least1/3 into the stovefor better heatretention. The firewoodentrance leads to thecombustion chamber.The small entranceencourages the useof small pieces offirewood, which burnmore efficiently. Insulation around thecombustion chamberensures that the woodburns at the hottestpossible temperaturefor complete andefficient combustion.The air inlet on theside wall drawsmore oxygen intothe combustionchamber for hotterburning.The combustion chamber of the rocket stove increases draft to enable almostcomplete burning, hence higher temperatures up to 600 C. This leads to fastercooking, with less firewood and less smoke.GIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke3

Rocket Brick Stove: Builder’s Manual & User’s GuideMaterials needed to build one stoveThe rocket brick stove can be built with mortar made from either cement or clay/anthillsoil. Follow the quantity of materials and the ratios given in this table.Rocket brick stove with cementRocket brick stove with clay/anthill soilMaterialQuantityMaterialQuantityCement0.5 bagClay or anthill soil2 wheelbarrowsSand3 wheelbarrow loadsSawdust or choppedgrassLime1 bag2 wheelbarrows ofchopped grassor 1 wheelbarrow ofsawdustStandard-size firedbricks50 piecesStandard-size firedbricks50 piecesGravel1 bucketAsh2 bucketsClean water for themortar5 bucketsWater5 bucketsRatio for fire chamber,pot rests and skirtingRatio for outside bodyRatio for fire chamber, Ratio for outside bodypot rests and skirting4x cement1x cement1x clay or anthill soil1x clay or anthill soil1x lime1x lime1x grog (crushedbricks in particlessmaller than 3mm) —or fire cement3x sand1x sawdustor 2x grass1x sawdustor 2x grassCement for the combustion chamberCement is not heat resistant and to avoid cracking it is necessary to use a differentmortar for the combustion chamber. If the client can afford it, fire cement isrecommended for the construction of the combustion chamber. If not, use a mixture ofnormal cement, lime and grog in the ratios given above.Tools and equipmentneeded 4Spirit levelTape measureMasonry trowelMasonry wooden flatTri squareSpadeHoeMetal mixing basinWheelbarrowPosition of the stoveGoodpositionBadpositionGoodpositionSite the stove at an angle to the kitchendoorway, not directly opposite it.GIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke

Materials and dimensionsStove plan60cm30cm30cm30cm6cm6cmFirewoodentrance30cmAir inlet 12cmAir inletco60cmmch bua stmbe ior n36cm6cm6cmFirewood entrance 12cmBasic measurements to remember:Stove body 60cm x 60cm squareFirewood entrance in the front 12cm wideAir inlet in the middle of one side 12cm wide x 36cm long x 4cm deepCombustion chamber in the centre 12cm x 12cm squareHint: First mark the mid-point of each side of the stove foundation, then draw lines to jointhe opposite sides. Measuring the firewood entrance and air inlet now become easy.Standard brick dimensions75mm110mmThe rocket stove must be built using fired clay bricksof standard size, because then it is easy to observeproper dimensions for the stove, in particular thecombustion chamber, during construction.230mmA standard-size fired clay brick measures 230mm x 110mm x75mmGIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke5

Rocket Brick Stove: Builder’s Manual & User’s GuideBuilding a rocket brick stove step-by-step1. Making the foundation6Clay methodCement method1.1 Using measuring tape andtri square, measure and markout an area 60x 60 cm wherethe stove will be built. Dig 6cmdeep for the foundation.1.1 Using a measuring tapeand tri square, measure andmark out an area 60 x 60 cmwhere the stove will be built.Dig 4cm deep for thefoundation.1.2 Pour mixture of clay( withchopped grass or sawdust) intothe dug-out foundation area andcompact it firmly.1.2 Pour hardcore (gravel) intothe dug-out foundation areaand compact it firmly.1.3 Lay 6cm as your baseusing the mixture of clay withchopped grass or sawdust.1.3 Mix mortar using 1 spadecement 2 spades sand 2spades gravel.Add enough water to mix well.Spread mortar to a heightof 2cm over the hardcore,extending mortar a little at eachside to make an outer base forthe stove.1.4 Make the foundationslab as smooth and level aspossible.1.4 Make the foundationslab as smooth and level aspossible.1.5 Mark the midpoint of eachside of the slab and draw linesto join opposite sides. Wherethe lines cross is the centre ofthe combustion chamber —mark it with a stick. From thecentre, work outwards to makeyour other measurements. Referto the stove plan on page 5.1.5 Mark the midpoint of eachside of the slab and draw linesto join opposite sides. Where thelines cross is the centre of thecombustion chamber — markit with a stick. From the centre,work outwards to make yourother measurements. Refer tothe stove plan on page 5.GIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke

Building step-by-step2. Constructing the air inletClay methodCement method2.1 Dig out a groove 12cmwide x 4cm deep on one side ofthe foundation slab, through tothe other side of the combustionchamber. This will be the airinlet. Smooth the sides andbottom with a little mortar of theclay mixture.2.1 Dig out a groove 12cmwide x 4cm deep on oneside of the foundation slab,through to the other side ofthe combustion chamber. Thiswill be the air inlet. Smooth thesides and bottom with a littlemortar.2.2 Place 2 bricks in the frontto mark the door of the firewoodentrance. Place 1 brick on theback wall of the combustionchamber. The distance from thefront to back should be 36cm.12cm36cm12cm2.2 Place 2 bricks in the frontto mark the door of the firewoodentrance. Place 1 brick on theback wall of the combustionchamber. The distance fromfront to back should be 36cm.2.3 Complete the left wall ofthe combustion chamber anduse the clay mixture to fix thebricks into position.2.3 Complete the left wall ofthe combustion chamber withbricks and use fire mortar to fixthe bricks into position.For strength, always use firemortar when constructing thecombustion chamber.2.4 Place 4 bricks on eitherside to line the length of the airinlet.2.4 Place 4 bricks on eitherside to line the length of the airinlet.2.5 Complete the roof of theair inlet with another layer ofbricks. Mortar the bricks intoposition.2.5 Complete the roof of theair inlet with another layer ofbricks. Mortar the bricks intoposition.GIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke7

Rocket Brick Stove: Builder’s Manual & User’s Guide3. Close the combustion chamber and finish the first layer of bricksClay methodCement method3.1 Add bricks to close the roofof the combustion chamber anduse the clay mixture to fix theminto position.3.1 Add bricks to close theroof of the combustion chamberand use fire mortar to fix theminto position.3.2 Place the bricks for theouter wall of the stove, leavingspace for insulation betweenthe outer and inner walls.Mortar the bricks into position tocomplete the first course.3.2 Place the bricks for theouter wall of the stove, leavingspace for insulation betweenthe outer and inner walls.Mortar the bricks into position tocomplete the first course.4. Making the second layer of bricks84.1 Build up the second courseof bricks for the outer wall, andmortar them into position usingthe clay mixture.4.1 Build up the secondcourse of bricks for the outerwall, and mortar them intoposition.Make sure to check horizontallevels and height at all times.4.2 Pour the clay mixtureinto the gaps between thecombustion chamber and theouter wall, up to the level of thebricks. This is for insulation.Press down lightly to compactthe material so little air remains.4.2 Pour ash, gravel or strawinto the gaps between thecombustion chamber and theouter wall, up to the level of thebricks. This is for insulation.Press down lightly to compactthe material so little air remains.GIZ PSDA Stoves Promotion PO Box 41607 00100–Nairobi, Kenya T (20) 273 1826 F (20) 273 1836 E stoves@psda.co.ke