Belts on a swinger

[bandmiller2]

Have any of you built or seen a swing mill that used quarter turn belts instead of a gearbox.??I mean the sawhead rotating 90 degrees with just longish belts.Look at some of the tractor finish mowers they get real frisky twisting and turning belts.Gearboxes are a big expense and often problematic.Picture a  diesel with long belts and an arbor that swings from horizontal to verticle. Frank C.

[ladylake]

 Sure should work and be simple .  Maybe mount the motor at a little angle so when turned 90° the belts wouldn't rub toeghter  .   Steve

[Hilltop366]

Thought about it, but never done it.

Other ideas I thought about:

To somehow use some CV joints with a sliding shaft, not sure how much angle a CV joint would take or how many CV joints would be required.

Use a dry sump engine with remote oil tank and swing the motor as well as the blade.

[bandmiller2]

Steve ,that's a good idea tilt the engine 45 degrees between horz. and vert. to reduce the angle the belts need to twist. Frank C.

[longtime lurker]

Long before there was a thing called a swingmill there was a beast called a Hargan Saw -which as a user who lived to tell the tale with all my arms , legs and digits attached and my hearing only mostly destroyed - is something I'd recommend you place on that list of "things I'm glad I never played with".
The operating principal was exactly that: belt drive and the sawhead pivoted.  I can't post pictures but... google image search and thou shalt seeeeeeeeeee.

You can do it... but why would you want to?

[bandmiller2]

Thanks for your concern mate,we used to have those DanGed things here,although I've never used one.I had the attachment for the front of a Gravely two wheel tractor with the swingable blade but gave it to a guy I knew with a briar problem.What I was thinking about would be a four post carriage with the swing saw,everything captive,very much like a Lucas without the gearbox. Frank C.

[longtime lurker]

Yeah Frank, I don't know that those old Hargan saws ever killed anyone... it was mostly lack of blood after it swung and took your legs off that killed you :

I'm not an engineer but... belts aren't a terribly efficient way to transfer power, compared with a gearbox. Should do the job fine but then you need a clutch to disengage the blade for starting, so you need a third pulley in there like the old hargans used, then it's either too tight and half engaged when it's not... or the belts are slipping when it's under heavy load.
In terms of ease of fabrication and fix it in remote areas I think you're onto something.
In terms of mechanical efficiency and general ease of use a gearbox still wins. Takes a bit to kill a well made box. They're expensive sure... but it's a case of pay for it once or pay for it every day when it doesn't work right. You'd also have to position your motor / belt pulleys in line... make for a long carriage which might pose an issue somewhere.

But it would work and there's no reason not to.
I'm actually thinking hydraulic drives for my next project

[bandmiller2]

Lurker,hydraulic drives have a lot going for them,a little costly to buy but give you control and a lot of power in a tight space.A friend of mine drives his bandmill with a hydraulic motor,a pressure gauge in the line lets him adjust his feed to the load. Frank C.

[Ianab]

Efficiency isn't a strong point of hydraulic drive systems.

Years ago Peterson built hydraulic powered swngblades, which obviously simplified the swing mechanism as the hydraulic motor can just swivel with the blade. BUT they took a LOT of power to drive them. Like they needed to be driven off the hydraulic system of an ~80 hp farm tractor. Now I know a tractor can't put it's full power output into it's hydraulic pump, but even with a direct driven pump you still needed more than the 20hp gas engine that would usually power the mill.

I did see one for sale a while back that had a ~60hp diesel mounted on a trailer. To move it you could load the mill and rails on top of the power pack and tow the whole rig around. But it was a big heavy rig compared to the current mills, and wouldn't be economic to manufacture unless you happened to have the big diesel sitting on the shed already.

As far as power efficiency goes belts are actually one of the most efficient transfer methods. Very little friction loss in a good belt drive. Just hard to make them compact.

Ian

[Satamax]

Hey guys, i still think direct electric drive is the most eficient. Even generators are more eficient at transmiting power than hydraulics.

http://www.youtube.com/watch?v=fATvaEQqakU&feature=related

[Nomad]

Efficiency isn't a strong point of hydraulic drive systems.
Ian

     Ian, I have to ask what data you're basing that on?  It disagrees with my electro-hydraulic training.  (You could well be right, but I'd like to see the data for myself!)

Hey guys, i still think direct electric drive is the most eficient. Even generators are more eficient at transmiting power than hydraulics.
http://www.youtube.com/watch?v=fATvaEQqakU&feature=related

     Same comment to Satamax.  You're saying a generator is more efficient than a hydraulic gear or axial piston motor?  I'd like to see the data you're basing that statement on.  It's possible I've been very wrong for quite a few years!

[longtime lurker]

Hydraulics or electicity do take more weight, no doubt about it. And weight is an issue... if you want to carry it into the jungle on your shoulders and carry it and the wood sawn out the same way. Or sling it under a helicopter ;D

Most of though don't want to do it that way. And we live in economies where doing it that way is rarely cost effective anyway - unless you have the volume to support a heli logging operation in which case I really think it is the way to go.

The thing about hydraulics or electric drives is that the power rating may be the same but the torque curve is different. Powers either there and its on full... or it isn't there. Sawing really isn't about HP, it's about torque, at least with circle mills ( don't know enough about bands to say). That's why a Peterson ASM, to pick an example, runs either a 38HP petrol or a 20HP electric. And the electric will have more power transfer into the blade across a wider range of loads.... ie it won't bog down the way a petrol will.

Electric is by far the most efficient drive mechanisim. That's why big mills run electric. Me, I love the stuff, but in my situation where I do need a degree of portability I'd prefer hydraulic. Hydraulics are basicly idiot proof - I know how to fix them. And they can work in the rain. Wet three phase motors are not a good thing.

That's why I'm currently lusting after a duncan beam saw. :D

[beenthere]

Agree with nomad. The gear drive I believe is much more efficient transferring power from engine to blade.

Reminds me of International Harvestor, in the mid 50's, launched a series of their farm tractor models and pull-type equipment with no PTO drives. Instead they put generators on the tractors and electric motors on the balers, combines, etc. They had some complete lines built and were out demonstrating this new revolution - plug in and go! ;D
Apparently not very well field tested. The engines of those days maybe in the 50 hp range, and they would handle the equipment, but had no power left over to pull the baler, load of bales, and all of it around the fields.
A big faux pas that year. This was tauted as the revolution of the century in farm equipment. Sounded good, just plug it in and go. But too much energy was lost converting hp to electricity and then back to turning gears and parts.

[Ianab]

Ian, I have to ask what data you're basing that on?  It disagrees with my electro-hydraulic training.  (You could well be right, but I'd like to see the data for myself!)

Some actual testing here.
http://www.nfpa.com/events/pdf/2012_eehpc/ppt/06_04_michael%20energy%20efficient%20hydraulics%202012nov28.pdf

Basically a test rig with an electric motor, driving a hydraulic pump, to a hydraulic motor, powering a load. So you can compare the power transmitted, vs what you would produce with the load directly coupled. Actual efficiency varies with the type of motor, and the speed / load it's under. But it's in the 60-85% range. The rest of the power goes into heating the oil.

A belt drive is more like 98% efficient, with a gearbox not far behind.

As a quick rule of thumb, you can judge how much power is being wasted by how hot the transmission is getting. A belt might get warm, but that's all. Compared to the heat generated in a large hydraulic system, that you might need a radiator to get rid of it?

Electric also has losses, maybe you have 90% efficiency in the generator and the motor. That still means about 20% of the power if going into making stuff hot. Electric motors need cooling air for a reason, and that power (heat) is coming from some place.

This doesn't mean that either system wont work, and in some applications the advantages of an electric or hydraulic transmission outweigh the inefficiencies. I'm thinking things like Diesel Electric locomotives. In that case using a clutch and gearbox drive (or a drive belt  :D ) isn't practical. The electric drive with it's huge torque at low (zero) revs is ideal for getting a train rolling. For heavy machinery the torque, speed range and precise control of a  hydraulic system is great.

But you don't see them used in a high efficiency car, because putting 10-20% of the power out though the oil cooler isn't efficient.

In a sawmill situation these methods will work. Maybe the advantages will outweigh the efficiency losses? For example being able to power the mill from a tractor or other large reliable and fairly efficient diesel engine. As I said, I've seen mills that work like that. I've even seen an old Peterson set up stationary with a three phase electric motor driving a hydraulic power pack. It worked fine, just a fair percentage of the power went to making oil warm. Not so much as to make it impractical though.

Ian

[longtime lurker]

Ian, I have to ask what data you're basing that on?  It disagrees with my electro-hydraulic training.  (You could well be right, but I'd like to see the data for myself!)

Some actual testing here.
http://www.nfpa.com/events/pdf/2012_eehpc/ppt/06_04_michael%20energy%20efficient%20hydraulics%202012nov28.pdf

Basically a test rig with an electric motor, driving a hydraulic pump, to a hydraulic motor, powering a load. So you can compare the power transmitted, vs what you would produce with the load directly coupled. Actual efficiency varies with the type of motor, and the speed / load it's under. But it's in the 60-85% range. The rest of the power goes into heating the oil.

A belt drive is more like 98% efficient, with a gearbox not far behind.

As a quick rule of thumb, you can judge how much power is being wasted by how hot the transmission is getting. A belt might get warm, but that's all. Compared to the heat generated in a large hydraulic system, that you might need a radiator to get rid of it?

Electric also has losses, maybe you have 90% efficiency in the generator and the motor. That still means about 20% of the power if going into making stuff hot. Electric motors need cooling air for a reason, and that power (heat) is coming from some place.

This doesn't mean that either system wont work, and in some applications the advantages of an electric or hydraulic transmission outweigh the inefficiencies. I'm thinking things like Diesel Electric locomotives. In that case using a clutch and gearbox drive (or a drive belt  :D ) isn't practical. The electric drive with it's huge torque at low (zero) revs is ideal for getting a train rolling. For heavy machinery the torque, speed range and precise control of a  hydraulic system is great.

But you don't see them used in a high efficiency car, because putting 10-20% of the power out though the oil cooler isn't efficient.

In a sawmill situation these methods will work. Maybe the advantages will outweigh the efficiency losses? For example being able to power the mill from a tractor or other large reliable and fairly efficient diesel engine. As I said, I've seen mills that work like that. I've even seen an old Peterson set up stationary with a three phase electric motor driving a hydraulic power pack. It worked fine, just a fair percentage of the power went to making oil warm. Not so much as to make it impractical though.

Ian

Okay, that makes sense. I think the test was somewhat biased towards the hydraulic systems actually, my outside the lab experience tells me that friction from the lines is a major heat generator in hydraulic systems, and that lab test didn' t have a whole lot of hose in it.  I've got an information package coming from Duncan RE their hydraulic drive option. It will be interesting to see just what they spec for power requirements to replace the standard three phase motors.

[Satamax]

Well, Ian hit the nail.  Tho, i thought hydraulic were worse. (having bad experience with hydrostatic for the moment)

Electric, if you don't need a generator is realy eficient, maximum torque at low rpm etc.  Can be made light, cheap too. Imho, it's far cheaper to run electrical wires, than having hyd hoses made.

GEnerators, well the efficiency is low, i don't think you can output more than 28% of the energy stored in the fuel.

But that's due to the 35% efficiency of the explosion motor.

You can have up to 90% mechanical efficiency with hydraulics, at the pump, but more energy is taken from the transmission of the fluid, du to the friction in the pipes. And i think an hydraulic motor has a fair bit more friction than an electric motor.

As well, electric component  degrade far less with time than hydraulic. How often would you change an electric motor compared to a hydraulic one?

Well, i don't have all the data. And i'm too lazy to search now ;D

There's an advantage to the hydraulics, the smoothness in transmissions for work vehicules. I don't think there's many telehandlers or diggers being made with mechanical gearboxes nowadays. May be fading out too on backhoes. But that's variating speed. For constant speed, mechanical should be as good. But there's something on it's way, at least on snow cats, electrics! May be soon with gas turbine generators.

In the  swing mill, i can see the atraction of the hydraulics, easy to switch from vertical to horizontal cut. Power can come from far away. Not necessarily on the head. While the electric motor has to be there, as well as the petrol. And hydraulic motors are way smaller than it's competitors.

Actualy, thinking of it, exept in cases where the swinger has to be caried by hand, hyds can be real intresting, with a nice pump on a pickup truck, two hoses and the usual frame of a swingmill, and a small hydraulic motor. IIRC, a 33kw like the omt 200 hyd motor weights only 40 pounds! But that will be expensive.

On the other hand, stationary, with no weight prob cheap and easy to make, the electric wins! IMHO.

[Ianab]

Those tests where "best case".

Back in the real world with longer lines (more friction losses) and maybe mismatched components things would be worse.

Ian

[Hilltop366]

When it comes to power loss I try to think of things this way.

The more things in between the power source and the work the more energy will be used up getting there.

The more times the type of delivery of the power source is changed the more energy will be used up.

Bandmiller2 if using a belt to drive the blade could one take advantage of a vertical shaft motor to get the output shaft lower while keeping the motor up higher and out of the way of the saw? Perhaps there is no real advantage, not really sure.

[Satamax]

When it comes to power loss I try to think of things this way.

The more things in between the power source and the work the more energy will be used up getting there.
The more times the type of delivery of the power source is changed the more energy will be used up.

Bandmiller2 if using a belt to drive the blade could one take advantage of a vertical shaft motor to get the output shaft lower while keeping the motor up higher and out of the way of the saw? Perhaps there is no real advantage, not really sure.

CF post number nine! ;D

[bandmiller2]

Hilltoper,I don't see why a fella couldn't use a verticle shaft engine,belts will be right half the time same as a horizontal shaft engine. Frank C.

[Hilltop366]

One possible advantage of using a vertical shaft engine would be availability of used engines from used lawn tractors although it may not be easy to find a large enough engine if going with a 10" cut.