Author Topic: TECH: portable electric mill, powered by portable electric generator (Read 4122 times)

woodbowl · « **on:** July 08, 2005, 08:33:35 PM »

This topic surley must be covered somewhere on ff, but I can't seem to find it. Why do such a thing when a gas or diesel motor is so reliable and proven? Burning fuel on a job site to generate electricity, then running an electric motor to saw with doesn't make sense........... Does it?

It would seem that more fuel would be burned with this endeavor. If a fellow wanted to build a quick swinger and bypass the problems associated with right angle gearboxes, tilting an electric motor starts to look attractive. Plugging up to the pole is handy, but I'm talking portable.------I've heard that locamotives run on electric motors powered by diesel driven electric generators. Anyone know what that's all about? If anyone knows of a portable sawmill operation in this configuration, please share some wisdom and photos if you have them.

Brad_S. · « **Reply #1 on:** July 08, 2005, 09:47:27 PM »

I'm not very mechanical, but I have read that Diesel-Electric locomotives operate as such because no mechanical transmission can handle the forces involved in pulling trains, but electric traction motors can.
I have seen pictures of portable electric mills with gen sets mounted on the back of the flatbed towing truck. I'm pretty sure it was an article in Sawmill and Woodlot, but then again, it might have been Timberline.

wiam · « **Reply #2 on:** July 08, 2005, 10:19:32 PM »

I think that if you were doing at least half of your sawing at "home" it might be worth it.

Will

D._Frederick · « **Reply #3 on:** July 09, 2005, 01:20:26 PM »

The mill that RON is sawyer for has diesel electric power because it costs too much to get commercial power to.

Baker has a sawmill system with sawmill, edger, resaw, and sorter that would work best with diesel electric power. It mades a nice, quite power system.

Arthur · « **Reply #4 on:** July 10, 2005, 07:12:37 PM »

All the swingers supply electric as an option. The electric engine however does not swing just replaces the power unit.

Electric engines tend to be large in diameter and if swung would interfere with the log. You could have the engine mounted a long way out but you would end up with lots of other problems.

The advantage of the electric is the smooth and constent power supplied to the blade as well as the reduced noise levels. The controls tend to be better as well.

The disadvantage is that you need a 3phase power supply and heavy cables.

When setup it is the better option to petrol.

Ianab · « **Reply #5 on:** July 10, 2005, 09:15:26 PM »

Technically it's possible.
Cost wise it's probably not very practical, add up the cost of the big generator and the electric motor, makes the engine / gearbox seem relatively cheap.

Another option might be to run hydralic power to the blade. A small hydralic motor can pivot along with the blade and be powered by power pack mounted on the mills transport trailer. Some of the early Petersons could even be run from a large farm tractors hydralic system.

Cheers

Ian

woodbowl · « **Reply #6 on:** July 10, 2005, 09:21:46 PM »

Thanks Arthur, all this makes perfect sense. -----Considering the 3 phase efficiency and running a portable generator, how do the numbers crunch out? What watt gen, gen cost, service life (hours) and additional fuel burn as compared to a gas or diesel engine?

woodbowl · « **Reply #7 on:** July 10, 2005, 09:27:33 PM »

Ian, I've heard that hydraulic motors lose about 60% of their power by the time it gets to the blade. This seems like an awful lot if it's true. But I keep seeing ads to buy this type mill.

Ianab · « **Reply #8 on:** July 10, 2005, 09:58:34 PM »

Quote from: woodbowl on July 10, 2005, 09:27:33 PM

Ian, I've heard that hydraulic motors lose about 60% of their power by the time it gets to the blade. This seems like an awful lot if it's true. But I keep seeing ads to buy this type mill.

I didn't say it was a very efficient way to drive a saw... but it is practical.
OK, so you have a 50 hp engine, and only cut as fast as a 25hp... thats still plenty fast

If I remember right the Petersons needed an 80hp tractor to drive them, but a lot of that might be to do with getting enough hydralic flow to spin the saw. I doubt many tractor hydralic systems would fully load the engine under any conditions.

Cheers

Ian

Arthur · « **Reply #9 on:** July 11, 2005, 01:56:30 AM »

Another problem with electric engines is the weight. However a 7.5Kw engine will perform as well as an 18hp petrol but is about the same weight as a 27hp petrol engine. 15Kw electric engines perform as well as 35hp petrol but weight is very high.

We can supply 7.5Kw and 11Kw only. The w5Kw it too heavy for our mills.

Hydraulics - the old hydraulic systems and those on most tractors are low volumn/low power units and do loose considerable power.

Ianab is correct with modern hydrostatic systems in that the motor is very small and can replace the gearbox and swing with the blade. We use a unit which is only 100mm in diameter. This is no wider than the boss/hub of the blade.

With a quality unit you do however pay the price. You can get cheap motors and use cheap hydraulic components but then you will loose power. Our little motor runs good on a 35hp diesel but can copy with an 80hp unit so its down to you how much you want to spend.

The thing with the hydostatic is the flow rate and pressure it runs at. The higher the pressure the more torque is transfered. These modern units working at 400bar are at least 80% efficient.

The biggest advantage is that maximum torque can be acheived at 50 rpm so you have total control of the blade with smooth power.

Another advantage is that once you have a power head (engine and hydraulic pump) you can then power other machinery.

If you want more details about the Hydraulic mills give Lindsay a call at D&L Doublecut. He manufactures his own as well as the EcoSaw with Hydraulic power units.

arthur

slowzuki · « **Reply #10 on:** July 11, 2005, 08:46:23 AM »

The diesel electric model of milling works well when you have a big 3 phase portable generator already, like say if you are a milk farmer or have a big welder/genset in your work truck.

At home you have all the advantages but can still be portable.

Also the multiple equipment factor comes into play, you can buy electric powered stuff cheaper than diesel and power it from the same generator.

Timo · « **Reply #11 on:** July 13, 2005, 01:50:14 PM »

A friend of mine converted his gas powered band saw into an electric powered swing mill, using a 220 volt 7 hp electric motor and an 18" Lucas blade. The whole motor swings/ pivots with the use of an air cylinder. He finds it works better then the 10hp honda powered band mill did....

As far as I am aware (and I am no engineer....)
There are two rationals for gas/ diesel electric: Power modulation and fuel economy. An internal combustion engine can be made to run much more efficiently if it only has to run at a set RPM. The necessity to modulate power delivery by raising or lowering the engine speed hinders it's efficiency. That is one of the things that makes hybrid cars so efficient. Also, as it was pointed out earlier, in the case of diesel electric trains the power modulation and clutching of such a large engine is difficult.

Electric engines also produce 100% torque at no rpm, but this is something that is of little benefit to a saw mill which requires a certain tooth speed to cut properly anyway.

I like the idea of an electric powered mill run by a portable generator. However, there are definite safety issues with this setup. High voltage three phase is not to be mucked with. I don't know about the rest of you... but the idea of trying to safely route power around a mill site with rolling logs, droping cants, axes, loaders, and the usual spectators is not a pretty picture. Just my 2 cents worth...

Murf · « **Reply #12 on:** July 13, 2005, 02:11:07 PM »

I often wondered about it too, but figured, as was mentioned, it would only be a big benefit if working away from 'home base' was just a once in a while thing.

I could see, however, running a silenced genset, or a long power cord, as a good noise solution.

Speaking of tractor driven mills, I wonder why nobody has thought of using the PTO to turn a hexagonal or octagonal shaft, and then have a blade that slides back and forth on that shaft.

If you got a little more sphisticated you could even use a threaded second shaft to give you drive on the blade.

mike_van · « **Reply #13 on:** July 13, 2005, 04:15:12 PM »

Not because i'm with the power co., but I really like my electric powered mill. My 10 hp 3 ph. motor was 300.00 new, unless you constantly overload it, the only thing to go bad is the bearings. No fumes in my barn, super quiet, with the blade in the log, you can talk normal and still hear. No ear protection required. The huge Euclid trucks are deisel electric also, I think one motor on each wheel? They power & brake with the DC current.

Arthur · « **Reply #14 on:** July 13, 2005, 06:33:56 PM »

Timo

If your setting up with electric you need to spend the extra on safety.

We use a very common folding track system which keeps the cables in a nice and tidy order. If the track system is no good for your setup then you need to hang the cable from a wire. For wear its best to fit small wheels for the running along the wire. Works great and gets the cable off the ground out of the way.

The longest ive seen was over 75m. Just beware of overhead cables when using your loader.

Every part of milling has some danger attached to it.

arthur

mike_van · « **Reply #15 on:** July 13, 2005, 07:38:42 PM »

I use a type of boom attached to the wall, about 12' long, on bearings. 2" plastic pipe attached, it follows the head back & forth.

Timo · « **Reply #16 on:** July 14, 2005, 12:18:06 AM »

Arthur,

Don't get me wrong - I think electric is a great idea, for a stationary mill. I just wonder about the logistics of setting up and maintaining a safe arrangement with a truely portable mill. I'm sure it can be done, and is done. I just wonder whether it would continue to be done (safely) over the long run. From an efficiency perspective it makes lots of sense: all sorts of usefull implements could be run off the gen set. Not to mention that a diesel generator has a long operating life.

Take the site I was on today: there are two mills (ones mine

), a tractor, a bobcat, two dogs, and 7 people running around. If I had a gen set, it would have to be set up right next to the mill - which kind of takes away the 'nice and quiet' advantage. Mind you, then I could actually install that beer/ cola fridge on my mill trailer.... you might be on to something!

Arthur · « **Reply #17 on:** July 14, 2005, 07:22:32 PM »

Timo

If you setup the Genset next to your mill and use the track system attached to your mill then its a good long term safety as you never need to break it down once set properly.

good idea with the fridge though. We will need to look at that one as part of the mill price. Good selling point.

arthur

rebocardo · « **Reply #18 on:** July 16, 2005, 06:11:01 AM »

Electric motors put out massive torque as soon as they turn, do not require a clutch or tranmission, can be (generally) oriented any way you without effecting performance, plus, they are quiet, and allow you to isolate the noise and fumes from a gen set.

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Author Topic: TECH: portable electric mill, powered by portable electric generator (Read 4122 times)

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