openspaceman

I thought I replied to this earlier but apparently it didn't send. Warming bricks or stone by a fast hot burn and then allowing the heat to seep out over time is the principle of a masonry stove but they do control combustion air. Alycidon is right, an open fire loses a lot of heat up the chimney in warming excess air, the chimney still needs to be hot at the top to avoid fouling so dumping more flue gases than necessary at this temperature robs heat from the building. Indeed if the building is warm ( say a fire in one room and central heating elsewhere) the open fire can eject more heat up the chimney than the small amount of heat it emits by radiation or heating the brickwork. This of course still happens once the fire is out and the flue still warm.

So if the Gross Combination Weight exceeds 14,230kg and the tractor is less than a quarter of this weight the brakes must operate from the tractor service brake. Event then the weight the trailer imposes on the tractor must not exceed a maximum of 14.230*.35= about 5 tonnes. I got my date wrong in an earlier post when I said 1986 Not at all, it says if it exceeds 14230 then the brakes must operate when the service brake is used. Next it says the brakes must be efficient ( and this covers trail;ers exceeding 750kg) and must operate on 1/2 of the wheels and the parking brake on 2 wheels. which is why I suggested adding brakes to the fornt pair of axles. Yes It means when you push the brake pedal of the tractor it must operate the brakes on the trailer proportionally to the braking of the tractor as opposed to the driver operating a separate lever for the trailer brakes.

Hibernaculum?

I worked for an IH dealer in ~76 when they first came out with q cabs. The fitter then said the immersed disc brakes were paper lined, I never did see any stripped out but they were a b*****r if you had them on independent and tried to press them both instead of the centre pedal, straight to the floor.

If you;re prepared to tart it up a bit I can let my wife's go. It only holds some old tools and such. PM me and I'll take a picture.

Yes that's how I see it. If the tractor is pre 1986 I think you can still use separately controlled brakes, later than that and I think they need to be connected to the service break. I used a spring loaded ram on the county trailer that applied the brakes if the coupling broke. There is an exception for towing unbraked harvesting equipment, which was the argument I was going to use when traveling empty between sites. Looking at the OPs trailer it's similar to my moheda and I think you could cut the front stub axles off and replace with a braked version coupled to a ram.

There's no problem doing as you suggest with the logs providing air passages. You can fill a pan with chip and then light a log fire on top of it. With the Jotul type stove that burns from front to back, like a cigar, you can stack chips at the back and light a log fire at the front. The problems occur when you put a lot of chip in and it all tries to burn at once, assuming you haven't smothered the fire first. You simply cannot get enough air in. A centrifugal fan from a laptop is good for livening things up. An old virtual friend, Alex English in Canada, has devised a wedge shaped burner for woodchip that fits between the stove and door. It is an adaption of a combined updraught and downdraught gasifier invented by Aqua Das, known as a Dasifier. I still prefer a vortex type air curtain device for clean burning but you do require a fan for this.

I should have parts book and engine manual for A55 but not a55f, it will take some searching so pm me if Lamberhurst cannot help.

Sounds like AOD a mixture of ills Forest Research - Acute oak decline

trac in Woking 01483 768485

+1 and it gets much worse

I think it's ok to use brushcutter gear grease in a hedge cutter but not vice versa

w.o.d.??

These things are not approved on smaller strimmer heads, I know we are only allowed them on the two bigger Stihls although I dis use one on my 360. I guess the worry is the head could shear off.

You had me worried there for a bit. Ten years ago using similar I could load 14 .7m3 bags and stack them in barn in a normal 7 hour day.

Perceived wisdom was that working green wood wasn't a problem, possibly because the particles were larger or clumped so the body coped with them. Some hardwood joinery dust was considered dangerous and this included english oak. A couple of exceptions I know of: 1 a sawlog customer of mine is/was a medical doctor (his first ever enquiry to me was via a radio link from a main battle tank in germany in the run up to Iraq1), he was building a house extension and doing all the wood himself from the round. In some way the initial work sensitised him and he subsequently became allergic to sawdust and had to wear gloves and face mask. 2 two round timber buyers I sold to between 1980 and 1995 have died from throat cancer, I don't know what their previous work history was. I have no other acquaintances that have this cancer.

Efficient isn't a very good word to describe conversion of the chemical energy into sensible heat. You can describe how much of the heat released gets into the room and how much is lost up the chimney and you can work out how complete the combustion has been, then you might work out a figure for the overall conversion of energy to useable heat in the room. There is no reason why big logs should be any different but there are problems. Natural gas is a good fuel, you can have a naked flame from a pipe and provide enough oxygen from the air around the pipe to completely oxidise the gas in a yellow flame but as the flame gets bigger the surface area of the flame is inadequate for diffusion of oxygen into the gas and sooty carbon is given off. So you arrange to premix the gas and air before the flame in the right proportions, the result is a blue clean flame. Wood is a bit more difficult, first you have to heat up the surface to drive off moisture, then raise it to pyrolysis temperature, about 270C, to expose some fresh char and ignite it, once the char is burning hot enough it then ignites the pyrolysis offgas if the air is available, this will normally be a diffusion flame in a small fire. At the same time this burning surface is heating up the interior of the wood until it too dries, pyrolyses and ignites. If the wood is in small pieces, like chips, you can continually feed them in with the correct amount of oxygen in air to continuously burn the lot, in practice you will supply double the actual amount of air required to keep things clean. The surface area for reaction is large in relation to the mass of fuel and the conditions are constant. At home you probably do this by throwing on a new split log now and again and the air:fuel ratio constantly varies. With good fuel excess air is the main reason for poor energy transfer into the room as it inevitably means more heat goes up the chimney. Large logs have high mass, poor surface area to mass ratio and probably higher moisture content. The effect of this is adding a large log quenches the combustion temperature while the log heats up and then once it strats burning there is need for more air for the combustion to complete. With big dry logs or logs that have been left to smoulder (char burning but pyrolysis offgas and moisture being driven off unburnt as smoke) they gradually heat up in the box anf go through the drying then offgassing cycle until the firebox is full of hot offgas. Open the door at this stage and you have a potentially lethal deflagration as the stovve contens are all above the autoignition temperature of the woodgas just waiting for oxygen to react with. The whole log burners I dealt with got around the problem by being configured as down draught or cross draught gasifiers. The lot was loaded as a batch and the cool primary air cooled the logs so they just burned at the gasification front, all the offgass then burned in a secondary area. Even so it was always necessary to have a large thermal load to even out the peak from the process.

Ringbarking takes time, I proposed a simple tool like the striper we used to season birch poles but working round the circumference back in the 80s, to avoid herbicide. Using the boyscout axe and dosing with glyphosate meant you could deliver a fatal dose without having to completely frill girdle the stem. I have ringbarked scots pine and the tree has lived due to root grafts, the stem below the debarke section grew fatter whilst that above did not.

I didn't have much problem with cca in use, it was the chemicals that were used at the stake plant before and the pollution when disposed of that were the problem. That and the treatment was seldom properly done. Chromated copper arsenate has three poisonous ingredients but its probably the hexavalent form of chromium that's released on burning that can cause long term damage. When its fixed in the wood it's the trivalent form. I thought it was banned now except for some long life products ( roofing timbers?). The stuff used now is an organic copper salt, as far as I can see it's nowhere near as effective, which might cause problems for nitwork rail soon.

I don't use a saw any more but I too used to rinse and tap in petroil mix. It was specifically deprecated in the saw manual but it worked. After 1976 when we had burned pine to clear up the tech branch at Alice Holt recommended adding some oil used by scrambles motor bikes to the filter (we also tied a sock from a stocking over the filter) because the char was so fine and abrasive on the saw internals, the oil helped hold the particles. I saw little difference twixt this and the oil in the mixture being left when the petrol evaporated but I stand to be corrected.

Most commercial boiler have insulated ss directly above the heat exchanger, the reason is that the heat exchanger is designed to take out all the heat it can from the flue gases and then discharge them at the lowest temperature that's acceptable, otherwise they are wasting heat up the flue. They will typically have a thermocouple in the flue at this point and modulate the chip feed to keep this near a set temperature, often about 150C. Many wood burning stoves simply do not have enough heat exchange area ( the stove body) to extract enough heat, hence the need for higher spec ss for solid fuel stoves compared with gas boilers, also because of the increased likelihood of a chimney fire.

This is about right for biomass in general and hardwoods but pine has higher lignin and if we are talking chipped wood rather than whole trees I think it would be 5.2 @10% mc wwb They base their working on 18.6MJ/kg oven dry, a figure used in the stove community for biomass in general. It's so specific a figure that I think the writer trawled it from past papers or an internet search rather than anything empirical.

The key is to burn smokelessly, which means maintaining a flame. Failing that you are right, the smoke needs to be exhausted before it can condense onto the flue walls. This means keeping the temperature above the dew point of any condensible tars in the smoke (just about impossible) and water (a bit more than 100C) all the way up the flue. As the flue has a thermal mass it's always going to be cold enough at start up. A thin SS flue which is insulated will get to temperature faster than a brick flue. I've seen single skin ss perforated by corrosion from being run too cool, the solution was to insulate it. It's the need to prevent condensation in the flue that makes one reason a woodburner less efficient than a condensing gas boiler.

Even then the energy used to do the drying is always more than necessary to just evaporate the water. Some of the water in wood is "free" water and some weakly "bonded", as wood dries the free water migrates out quite easily and the wood does not change size or shape much. After that (aka the fibre saturation point) the moisture removed is associated with the cell structure and its loss causes the structure to shrink. most of the shrinkage is tangential, which is why you see radial splits in a round log, then a lesser amount of radial shrinkage and very little longitudinal shrinkage. The ratio of the tangential to radial shrinkage is an indication of how stable the wood in a plank will be and is why woods like oak are better quarter sawn to avoid the differential. As wood dries below 25% mc wwb this bonded water is in equilibrium with moisture in the surroundings. As the capacity of the air to absorb moisture goes up ( i.e. its relative humidity goes down) moisture migrates through the wood and is evaporated. There is an equilibrium established between the wood and the air. In my house the rh in summer is around 55% and the temperature now is 18C, the equilibrium moisture content of wood will be around 10% on a wet weight basis on a wet day with no heating in the winter it will be around 15% ( given time for the moisture to migrate through the wood to the surface) An interesting side effect of the water bound to the cell structure having a weak bond is that there is a small energy change in addition to that needed to evaporate the water, this shows up in a hysteresis in the equilibrium moisture content depending on whether the relative humidity is increasing of decreasing. For most of our burning purposes these effects are insignificant and drying to the fibre saturation point is the most bang for buck. If we make some simple assumptions, like ignoring the ash produced and allowing a flue gas exit temperature of 150+C to avoid chimney problems then a simple formula for the energy we release and have available for heating will be: hardwood 5.2kWh/kg oven dry wood-0.75kWh/kg of moisture softwood 5.5kWh/kg dry wood -0.75kWh/kg moisture So a cubic metre of scots pine weighing 1 kg green with 0.4kg of dry wood in it and 60% mc will yield about 1.88kWh from the stove if burned efficiently, dry it to 30% mc wwb and it should give 2.6kWh, a 17% difference. As others have pointed out the advantages of drying below the fibre saturation point are largely to do with clean burning rather than energy gains. Whilst advocating burning wood as dry as possible I don't think much of a burner that cannot cope with 25-30% mc wwb wood.

I agree totally but some allowances have to be made for all technology. I live in a suburb which is mildly attractive and I did think hard about this. Locally there is a development with solar tiles and they are only conspicuous because they are slightly shinier than the rest of the roof (mock slates). Had this house still had a slate roof I'd have considered them.