The sawmill project has undergone some changes in design since the last concept. I have taken over development, and based on a comment on the previous concept we decided to pursue a different design, a dimensional sawmill. A dimensional sawmill is one with multiple blades that work on a stationary log. Because they have multiple blades, they can cut out a piece of dimensional lumber in only one pass. This makes them very fast in lumber production.
Industrial counterparts would be the Mobile Dimension Saw (MDS) and the Mighty Mite. Here is a demonstration video of the MDS taken from YouTube:
We chose a dimensional sawmill because it has the highest output, and the simplest design for personal fabrication – a circular sawmill with 3 blades. These two requirements are high priorities for Global Village construction. A circular blade can be fabricated easily, such as by cutting from a sheet with a torch table. Swing blade sawmills – where a single circular saw and motor rotate/swing to make different angled cuts – are apparently not stable enough to provide the output that they claim – according to feedback from two foresters. Plus, the swing mechanism is more complex. A chainsaw mill is the simplest, but it just doesn’t provide the required output for effective Global Village construction. Dimensional sawmills have the highest output of portable sawmills, but the industrial ones are also the most expensive.
| Woodsman | $12,000 |
| Lucas | $13,000 |
| Peterson | $20,000 |
| Mobile Dimension | $25,000 |
| Mighty Mite | $30,000 |
The industrial designs use gas or diesel engines and also carry the engine with the saws on the platform, whereas ours will have hydraulic motors – powered by the open source tractor, LifeTrac – for 40 hp of available cutting power. The hydraulic drive allows for great simplification in gearing requirements, as well as great simplification of the vertical motion mechanism, as will beome apparent in forthcoming work. The sawmill project will be another experiment in “factor 10” engineering, attempting to reduce the cost of machines by a factor of ten. Our goal is nothing short of high performance – a mill that cuts wood like butter.
So far we’ve decided on a design similar to the MDS, with a space frame (for stability) on two ‘I’ beams for x and y axis movements, a chassis surrounding the space frame with bearings to grip it on all sides, a vertical plate or beams on the chassis with another plate attached with bearings and adjusted vertically with a pulley for the z axis, the MDS like saws are mounted on the vertically moving plate and powered with hydraulic motors and pulleys to get the correct RPM.
A 2D top view layout has been done and some research is on the wiki:
The next step is going to be to make a prototype of the space frame, with a bill of materials, budget, and implementation plan. We need some research on space frames for that.
If anyone has advice, suggestions, ideas, questions, or can help on the design please post in the blog comments, or on the wiki sawmill dicscussion page. Please feel free to rearrange the sawmill page for a better workflow, it’s a work in progress.
Jeremy,
I completely disagree about the notion that you can just cut a saw blade from a piece of plate.
Saw blades are cut, bored to size, precision ground, tensioned (Hammered) then tipped (Brazed Tungsten tips)and the tips are then precision ground.
I highly applaud your intent to build a dimension saw.
Any saw can be a dangerous thing if not built or operated well.
For your saftey do not scrimp on the blade it is the single most important part of the saw.
Jeremy,
I have used a Lucas swing blade mill and they do a fine job.
Granted not as fast as the Mobile. But very easy to take to the log.
As to logs moving this could happen on the mobile too.
So there is a need to design a safe and secure log clamping system
I have serviced the VW motors used on Mobil Dimention saws now for several years … I have several customers near by who use this brand of saw,M D ……..they all say it is the best one man saw out there…….from my view regards the motor, M D did ok on some aspects of the VW air cooled conversion to industrial motor……..in two areas they didn’t do so well…..
FYI…. the VW motor they use is a “1600”( actually less ) cc single port bored for bigger pistons and liners….this turns it into an actual 1835 cc…this works fine, it is very common in the VW conversion world……
they weld 1″ solid shaft extensions to each end of a stock crank and this is how you carry the multi v-belt blade drive and the “cooling” fan….. on the end of the crank that carries the v belt pulleys they added a big , common roller bearing to take the radial force..that works fine…….
where their problems existed , on the older models anyway, they may have improved on this by now….
1) the cylinder / head cooling issues………basically they put a big radial fan on the end of the crank, blew air from under the cylinders and exhausted it up ward …….the tin work around the cylinders was nearly non existent…….as a result of this when the motor was at operating temp and the fan controls were full open for full “cooling”, ALL the “cooling” air was coming out above and as far away from the fan end of the motor, all at one place ahead of the front cylinder / head on each side…….and this air was cold….the motors would start to pre ignite and need shut down to cool…….crank / rod bearings would shell out on a regular a basis……
we solved this “cooling ” fail by modifying the original top tins to fit over the tops of the cylinders and putting a block off tin between the cylinders on their tops……this forced the cooling air to actually inter act with both cylinders and heads and exit dissipating the unnecessary heat not needed by this antique motor….ha ha …. exhausted the now hot air basically straight up from between the cylinders…..
2 ) they made nearly no provision for the air filter for the intake to be effective… nor did they try to filter the intake air that is being blown on the motor to keep it cool……as a result sawdust got into everything……saw dust into the carb’s gas / float / reservoir area….saw dust in the fins of the motor…inside the distributor cap……..everywhere……..
my recommendations for an air cooled VW motor in this use is to add a large surface area screened pre filter of the cooling air….it will get plugged so it needs to be regularly cleaned off and have large surface area……it needs to be a narrow rectangular box affair so it clears all the mill supports on that side of things as they have it designed ……
I think I have some pictures if that would be of any value……I would need to know where to post them…….
the lightness of the air cooled VW motor , lack of complexity vis a vie not needing radiators etc for water cooling, extra stuff and weight,is good…..the motor travels down the tracks with the blade assembly so light and small is good…….
They use stock stroke cranks and go from 85.5 mm cylinders ( stock “1600” cc ) to 92 mm…….
94 mm ‘s are the most common larger cylinders available ……however, you are getting thinner cylinder walls the bigger you go inside ……..
the 90 mm pistons and liners are very well liked because the thickness of cylinder has several positive points….
the operators of these mills all have compressed air and you couldn’t use that enough to keep the motor clean so it will flow cooling air around where it is supposed to be….
If you welded the 1 ” shaft extensions onto a stroked from stock crankshaft, along with bigger pistons and liners , you would increase the torque noticeably which is what I think you would want…….
I had a question about converting a mighty mite sawmill blade, I found this answer over at woodweb, any thoughts?
Sawmill Blade Conversion
I actually make giant custom saws for exactly this. You can see some of them here: http://www.ptmi.net