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Sunday, 21 May 2017

Baumr SX82 Review – first impressions

Model: Baumr-Ag SX82
My friend Alan asked me to have a look at his new Baumr chainsaw. It’s the 82cc saw, which cost him just over $200, delivered. Before even starting it, Alan made some modifications as suggested by Scott O’Malley on youtube, replacing fuel lines and chain adjusting system which are known problems. 
So far, it has done an hour or so of work, working really well apparently. 
Here are the new fuel lines.

these are some of the replaced fuel lines
Here’s the chain adjuster. The original bevel gear adjuster clearly had soft teeth and appears to have burred over almost on first use.
damaged spiral gear on the chain tensioner
Modified adjusting screw on chain tensioner
He also replaced the decompression valve, after early failure.
replaced decompression valve

Obvious issues

- Plastic cover melted by muffler

- Very weak bumper spike/dog, only on left side of bar. No spike mount provided on the clutch cover, but it could probably be improvised.

The saw would probably crosscut vertically down fine, but it wouldn’t be much fun to use in felling where you depend on the spikes more. Freehand ripping (e.g. cutting logs lengthways into beams) often depends on good spikes, so I wouldn't try it unless I'd installed better spikes. 

Chain and bar

The design of the chain bar is very similar to a 3/8” Stihl bar, with tensioner and oil feed holes in about the same places, but has narrower slot for bar studs.
Baumr bar on studs

Baumr bar on left, Stihl on right

Stihl bar doesn't fit - could with suitable bushes
In nearly new condition, the chain has a lot of clearance in the bar slot, with the chain able to tilt with the tooth corner in line with the bar face.
There should be daylight between straightedge and bar face

This means the chain is right on the edge of having no clearance, and the bar becoming bound in its own kerf. With a little bar slot wear, and the teeth losing set by being sharpened and shortened, the saw would cut very poorly very soon.
Normally if a bar and chain have this problem, I’ll consider hammering the bar slot to make it tighter. However in a new saw this didn’t look like a good idea. Measuring with a vernier caliper, I found the chain drive links measure at 1.4mm and the bar at 1.6mm. 

I tried a Stihl 3/8 chain of 1.6mm gauge (which interestingly measured at a shade over 1.5mm), and it fit well. I would say that the saw was delivered with the wrong gauge chain – I don’t know if they all have this problem. With a 1.6mm gauge chain, bar and chain would fit well.

It looks like they do all have this problem. On the Edisons page where the saw is sold [], the chain is specified as .058” gauge, which is just under 1.5mm - just what I found. However the spare chains they sell [] specifically for this saw are specified as .063”, which is 1.6mm - the right gauge for the bar supplied.
1.6mm gauge chain fits snugly
After cleaning, I noticed chipping on the bar slot rails, just behind the roller nose unit. 
This is where the bar might get some hammering from a slightly loose chain. I’ve seen chipped bar rails plenty of times before, but usually only after bad burring after a lot of wear and neglect to dress the bar. Chipping on a new bar suggests a problem with heat treatment – but perhaps indicates the bar has been heat treated which is at least an attempt at good quality.
The rim sprocket was a perfect match for a standard Stihl 3/8” rim sprocket.
Baumr sprocket

Stihl sprocket

Oil pump [added 30 June 2017]

Our neighbour Shaun also bought an SX82 and gave it a first run recently. After a little cutting, Alan noticed that the chain wasn't getting oil, and there was oil running out from under the clutch cover. Dismantling revealed missing hold-down bolts for the oil pump: easily replaced and the saw back in action soon. During this exercise the clutch drum bearing was found to be totally dry - risking damage to the crankshaft. 


This saw is incredibly cheap. It works and seems quite powerful, but has a range of problems from new which really need to be addressed in order to use it at all. You need to be pretty handy to do all these things. The things that need attention before first use so far include:

  • replacing chain with 1.6mm gauge chain (or bar to 1.5mm) 
  • replacing fuel lines with silicone fuel hose
  • greasing clutch drum roller bearing
  • checking oil pump bolts

We’ll see how this saw lasts over time. Maybe the motor itself is fine, and the saw will become reliable after initial problems are addressed. Perhaps I’ll update this post later...

Monday, 20 March 2017

Making a Cant Hook

If you’re going to work with logs, you need a cant hook (unless they’re all too huge to move without machinery or all so small you can pick them up with one hand). Crowbars are very useful, tractors are marvellous, but for a person to be able to move logs around while cutting, milling, building, etc., a cant hook is indispensable. I first met my wife and in-laws when I visited a blacksmith to ask him to make me a cant hook, so they have a special place in my life as well.
Cant hooks allow a person to roll a log with modest effort and ample control. Along with a couple of strong crowbars, a log buggy and a few other bits and pieces, you can move logs around surprisingly effectively. Without these tools, logs are heavy, unyielding lumps that risk doing harm to your body if you try to move them at all. Don't think that you can substitute a crow bar for a cant hook: using a crow bar to roll logs is like eating spaghetti with a spoon. 
I’m very happy with the design of cant hooks I use. The hook is permanently attached to the handle and is easily swung onto the log.  Some cant hooks simply have a hook with a ring (at the handle end), and a crowbar or wooden spar must be put through the ring as the lever. This is a terrible idea if you need to roll a log more than once: you need to do a lot of bending over to pick up the hook and ring, your fingers are at risk of crushing and it's slow and awkward (I tried it early on). A hook with a ring can be useful to roll really large logs when pulled with a tractor and chain, but I have rarely needed to do this.
I use leaf spring steel for the hook, point and hinge. Spring steel makes for a much stronger hook than mild steel, thus enabling a lighter tool. It’s also usually free and being recycled. Trailer springs are often the right size of flat bar: about 44mm x 6 or 7mm. If you couldn’t get leaf spring (from the tip, or from a spring works or suspension shop bin), you might be able to flatten large coil spring or find some other high tensile steel. If not, mild steel will do - I'm sure many good cant hooks have been made from mild steel or wrought iron, preferably with steel points welded on.
10mm threaded rod is used to attach the point to the handle, and a 10mm bolt (with 2 nuts to lock together) to attach the hook to the hinge.
I harden and temper the points of the hook and point, so they stay sharp longer and are less likely to be accidentally bent.
The holes in the hook and hinge are drilled (not punched) so that there is a smoother bearing surface for the bolt. Of course you need to carefully normalise the steel before drilling, by heating to red heat and cooling slowly in the ash bucket. 
The threaded rods which hold the point to the handle are welded into punched holes in the point. I use general purpose electrodes to weld them in, and re-heat the steel in the forge immediately afterwards to normalise and avoid brittleness at the weld. 
It’s very worthwhile shaping the back end of the hook and carefully positioning the hook in the hinge, so that the hook can’t swing back and hit the handle. Your fingers will sometimes be there….
The hinge is also set so it stops the hook from hitting the point, and blunting it.

I make handles from spotted gum, which is very tough. I start with a straight-grained piece of 75 x 50 (can I say 3” x 2”?), 1400mm long, which is then sawn into a taper both ways, then planed with an electric plane into a nice round shape: first square, then octagonal, then rounded; then use a hand plane to finish. I put some red paint on the top of the handle to make it less easy to lose in the bush, and rub the handle with linseed oil (raw) to reduce checking and splintering: it mostly reduces the drying and wetting of the surface, and consequent surface splitting.
Here are some photos to give you dimensions (in millimetres) and shape:
The main dimensions and shape - it's not an exact thing. 

A bird's-eye view of a cant hook doing a shoot on a living room floor. 

This shows the hook hinged back as far as it will go. It stops before it hits your fingers.

This is the hook as far forward as it will go - missing the point. 

The bump on the point plate is where a 10mm threaded rod is welded on. The other 2 threaded rods are under the hinge.  Note the double nuts on the hinge bolt, tightened together to allow free movement of the hook. 

The 10mm threaded rods come thru to the back and have nuts and washers. 

Friday, 3 March 2017

Replacing bicycle wheel bearing hub cups

Bicycle wheel bearings can be damaged, especially by over-tightening the cones and pitting the surfaces where the balls roll: balls roll between a cone on the inside, and a cup on the outside. Most frequently the cones (which screw onto the axle) are damaged, as their convex shape makes them more vulnerable (see my post on repairing cones here). But the cups, fixed into the wheel hub, can also be damaged if treated badly enough. When they're damaged, these cups can be replaced (but nearly no-one does it).

Here's a hub with a flanged cup in place at the top, and another cup on the table

Here's the same hub with the bearing cup knocked out
In most hubs the bearing cups are simple parts, pressed into a concave space in each end of the hub. In many hubs the cups can be knocked out with a steel rod put through the axle space in the middle of the hub and hit with a hammer. Sometimes this is difficult if the cup can't be reached due to the shape of the hub's insides.
Cups come in different sizes, based on outside diameter, and also come with or without a flange.
Here's a few new hub cups, small at the front, big at the back, flanged on the right, plain on the left
Cassette hubs often have a special threaded cup on the cassette side which can be spun out (left hand thread), but good luck finding replacements.
It's not easy to get replacement hub cups, but it can be done (I remember buying bike hub cups from a small town bicycle shop in Thailand in 1993). In Australia, bike shop owners can buy hub cups from a major wholesaler, Bicycle Parts Wholesale (they don't retail). Aliexpress also has several vendors selling hub cups, if you want 10,000 pairs.
We recently repaired an old front hub with new cups (bought through a wholesale account). The hub itself was quite interesting, apparently spun from aluminium tube.
looking into the spoke holes you can see the flange is made of 2 layers of folded pipe
This hub took flanged cups, which are seated on their external rim. Replacing the cups was a piece of cake: knocking out the old cups with a rod, and pressing the new ones with a metal vice. The only complication was that one side of the hub was slightly loose around the cup: light hammering fixed it easily so the cup pressed in tightly.

Here's the reconditioned hub (new cups, re-ground cones) ready to lace into a rim
Bicycles are really very repairable. The wearing surfaces: tyres, bearings, brake pads, rims, discs, cables...) can all be replaced after they have done a huge amount of work for us. We don't treat them like that: the culture of consumerism and novelty is well entrenched in the bicycle industry, with every encouragement provided to get people to throw away old bikes and buy new. But we don't need to do it that way. If your hub bearings are damaged, which is usually caused just by losing a few milligrams of steel from a bearing surface, it isn't necessary to throw away the whole wheel. It can be fixed and do another 100,000km (if you don't tighten the bearings too much!).

Saturday, 14 January 2017

Quick and easy biochar in a 200 litre (44 gallon or 55 US gallon) drum

The bush here provides an abundance of sticks!
This is a cheap, quick, easy way to make bulk biochar for soil improvement.
For a clear description of the burning method, see my page:
Recently we made our first few drums-full of charcoal purely for the garden. For years we have been making charcoal for cooking and blacksmithing, and using the siftings for the garden and orchard. Unfortunately I haven’t tried to make any sort of controlled experiment with our charcoal use in soil, but Erika and I both feel confident in it as a soil improver, lightening the heavy yellow clay we have in a small part of our garden, and hopefully holding water and nutrients as the evidence indicates.
We had a pile of waste sticks and branches, piled and dried after some tree cutting a few months ago. The material was too thin and light for fuel charcoal, but I was keen to try making biochar with it. A couple of Danish backpacker friends who were keen to play with fire did a some very successful burns in 200litre drums.
The bin is lit lying down, building a strong fire before standing it up with a shovel

Most of the time is spent feeding the fire with sticks
The method is exactly the same as our normal method of making fuel charcoal. The thin sticks mean that the wood chars more quickly and the whole burn takes less time. The work is also more intense as the pieces each have less wood in them and the branches need to be broken and fed in. Burning a full drum of charcoal took our 2 friends about 2 ½ hours, from lighting the fire to tipping the drum over to snuff the fire. They could probably have done 2 drums in a similar time, with enough sticks.

Using the biochar in the garden

Once cold (it was ready the next day), we trolleyed the drums up the hill to the garden, and opened full drums of charcoal. 

The pieces were smaller than usual, and less dense: most bigger pieces were easily crushed in hand. We didn’t sift it (which is usually the dirtiest part of making fuel charcoal) and dumped the bin contents straight into trenches in a new section of garden. 

To charge the biochar with water and nutrients, we flooded the charcoal-filled trenches with septic tank effluent (it’s our own microbes…). Then the trenches were given a quick dig over, backfilled with topsoil, mulched with lawn clippings and planted.

A good method

I think the 200litre drum, open top method is a really good way to make biochar from light material:

  • It’s quick: in 2 to 3 hours you can make nearly 200 litres (and probably nearly 400 litres with 2 drums in similar time) of biochar, probably about 30kg per drum (the material was very low density, so the charcoal is also low density).
  • It’s cheap: the kiln for making this charcoal is very cheap, simple and easily obtained: a standard 200 litre drum with the lid chiselled off, holes punched under the rim, and 2 steel skewers. If you oil the drum after the burn, it will last for years.
  • It’s dry: the method doesn’t need water, so doesn’t waste precious Australian rural water and can be done away from a water supply. The resulting biochar/charcoal is dry, so it is easily transported (this drum-full had to be trolleyed up a steep, rough hill after it had cooled).
  • I am confident in the quality of the charcoal, relative to other methods (more on this below).

Less effective methods?

I see a lot of biochar making methods on the net which strike me as difficult and unproductive. Most involve a double drum system, in which a small drum, preloaded with wood, is cooked inside a larger vessel. This clearly works, but is sadly unproductive: sticks are wild, crooked things that don’t easily pack, and which shrink a lot on charring. This leaves many of these double drum methods producing 2 or 3 buckets of biochar after hours of work, using equipment which is relatively complex and time-consuming to construct.
I don’t see the benefts of using double drums, compared to using a single container with fire and charcoal within. There is probably a higher proportion of the wood in the inner drum becoming charcoal, but this is (at least) balanced by the loss of wood burnt in the outer drum. Most importantly, this method is highly inefficient in time: kilograms of charcoal per hour of work; when most of us have abundant sticks to burn.
Other approaches are more similar to our drum method: sometimes called “Kontiki”, “flame curtain”, “open top”. Wood is burnt in an open-top vessel, or pit in the ground, very similar to burning in a drum. However most of these methods extinguish the fire using water. This is demanding: you need to be able to get 100s of litres of water to the fire; and the resulting charcoal is wet, heavy and much harder to transport. Also, I suspect you will often leach out valuable ash minerals from the charcoal, when draining the vessel after the fire is cold.
To me these methods are looking for a lid to extinguish the fire, to avoid needing water and to produce a dry, easily transported charcoal.

Biochar quality

I’m confident that charcoal made this way is as good as any other DIY method available for use as a soil additive - as biochar. I don’t have empirical evidence from experiments: the fertile soils of our gardens and orchards might have been just as good without charcoal, but we get the idea that the charcoal has been helpful.
Claims about what characteristics are important in biochar are diverse and deserve sceptical consideration. Some sources consider that it is important for biochar to include wood-derived tars and oils (from the smoking wood), to feed micro-organisms which will take up residence in the pores. Others are concerned about the toxicity of these same chemicals, and advocate charcoal of a high purity with minimal condensates.
Charcoal making is always a balance between over-cooking and burning some of your charcoal to ash; and under-cooking and making smokey charcoal. Slower methods in better-insulated kilns are likely to produce more consistent batches, as they give larger pieces of wood time to heat through and boil out the smokey content. These methods can take days per burn. Fast, open methods (like I use, or Kontiki) are less consistent, and always over-burn some charcoal to ash, as well as leaving some pieces of undercooked wood.
My conclusion so far is that claims that particular methods of making biochar are correct, or that particular types of charcoal are “biochar” and other types aren’t, are not supported by evidence. Biochar is simply charcoal being used as a soil additive. There is a huge diversity of types of biochar, made from a wide range of biological matter, using a range of cooking methods, and having various effects on plants.
I recommend reading some of the science-based literature on biochar, such as Biochar in Horticulture by NSW Department of Primary Industries.

Room for improvement

I’m sure this method could be improved:

§  A bigger vessel makes more charcoal in less time with less work. There is less cutting and handling, as bigger pieces can be put in whole. The fire is hotter and heats the wood quicker and cooks it more consistently. A bigger vessel would either need to be still able to be tipped over, or would need a method to seal the lid reliably (probably with soil, like my big bin).

§  Some closable air vents would make starting easier. I used to weld in threaded pipe pieces to charcoal drums, but I stopped because it makes more work, makes the method less accessible to people without metalworking skills and equipment, and it works pretty well without them.  

Making charcoal in a pit

Charcoal can be made in a pit in the ground. This is perhaps the oldest and easiest way to make some charcoal.
When I first learnt how to make charcoal for blacksmithing, from my (some time later to be…) Father in Law Adrian Hobba, it was in a pit in the ground. The pit was around 0.5m deep, something under a metre wide, and around 2m long. We made charcoal in the pit very much like we do now in drums.
We brought wood to the pit, lit a fire in the bottom, and fed and spread the fire until it filled the bottom of the pit. We would keep adding wood on top and letting it burn, until the pit was full of coals. When finished, the pit was covered with overlapping pieces of old corrugated iron placed across the pit, and then sealed with sandy soil, placed wherever smoke squeezed out.
At first Adrian’s pit was just a hole in the earth. Later we lined the walls with brick to stop the sides falling in and to help keep soil out of the charcoal. I’ve also made pits and lined them with old corrugated iron to keep the charcoal clean.
The pit made all of our charcoal until I became dissatisfied with the need to handle and transport several times more weight of wood than we produced in charcoal. Surely it would be more easy and efficient to take a steel container to the wood supply than to carry the wood to our pit! That’s when I started to try various steel bins and drums.
If you want to make charcoal from a large supply of wood in one area, a pit could be a good way to go. It’s cheap, not that hard to dig, and won’t rust or burn out.