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Belt drive vs gear drive

DPittman

DPittman

Ultra Member
I may have known the full answer at one time but it is now escaping my little pea brain and therfore I must ask...

From what I understand and remember, the pros of a gearhead lathe over a belt driven one has been chalked up as:
No pulley changes as the gearbox usually deals with all speed changes

More positive drive (no belt to slip or break or wear out)


The pros to a belt driven lathe as I understand and remember are:
Belt drive lathes are cheaper to manufacture.

Belt drive can provide a nicer finish as there are not the vibrations/harmonics that can occur with a gearhead lathe.

The downside of a belt driven lathe as I see are the belt changes to get the speed and feed changes.

However doesn't a variable speed motor (DC or AC VFD) on a belt drive pretty much elimate %90 of belt changes while providing an on the go range of speeds in any combination?

But even with a gearhead lathe isn't the geardrive always driven by a belt from the motor anyhow? And if so, why would that offer any advantage?

I know I'm missing something otherwise I'd see not only small lathes being predominantly belt driven. :rolleyes:
 
DPittman said:
I know I'm missing something otherwise I'd see not only small lathes being predominantly belt driven.
Click to expand...

I guess everyone is chicken to answer your question. But the jokes were worth it!

Edit - I am a child of the spoon and belt afterward era too. Worse was the strap at school, the spoon or paddle at home to follow, and then run like hell before dad got home with his belt.

I'll try to answer your question from my perspective. Then let the stone throwing begin!

It's a tough question in a lot of ways because you want to add operational advantages and disadvantages.

I think it's more likely a vintage thing than a quality thing. You had to change belts and sometimes activate back gears to change speeds on older lathes.

Gear head lathes typically have gears to change speeds similar to a transmission. Some (like mine) are oil bathed for quieter longer life. Others have an oil pump instead.

The belt between the motor and the gears on newer lathes does not define it as belt drive even though it clearly is...... LOL!

I doubt there is really any significant advantage one way or the other for vibration. That's more of a quality of the machine thing than the type. I have both types. My belt drive lathe is WAAAAY rougher than my gear head.

It is much easier to change speeds on my gear head lathe.

There are also variable speed lathes. These also come in different types.

A VFD on a motor allows the motor to run at different speeds which could reduce the number of gear or belt changes required to achieve a given speed.

A VFD can also make speeds available that are not available through gear changes. The lowest available speed on my gear head is 70rpm. I would like 45 or 50. The easiest way to do that is to install a VFD which adds variable speed to each selected speed. (I'll deliberately resist the temptation to discuss torque and horsepower - LOL!)

I think it's probably best to think of belt drive as just an older technology, variable speed as new technology, and gear drive as something in between. But there is a lot of overlap.

I like the Idea of gear drive to get torque multiplication combined with a VFD to fine tune and add variable speeds.

That's just a, rough attempt at answering your question. The story gets more and more complicated as you discuss it in more detail.

Let the stone throwing and clarifications begin!
 
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Susquatch said:
I guess everyone is chicken to answer your question. But the jokes were worth it!

Edit - I am a child of the spoon and belt afterward era too. Worse was the strap at school, the spoon or paddle at home to follow, and then run like hell before dad got home with his belt.

I'll try to answer your question from my perspective. Then let the stone throwing begin!

It's a tough question in a lot of ways because you want to add operational advantages and disadvantages.

I think it's more likely a vintage thing than a quality thing. You had to change belts and sometimes activate back gears to change speeds on older lathes.

Gear head lathes typically have gears to change speeds similar to a transmission. Some (like mine) are oil bathed for quieter longer life. Others have an oil pump instead.

The belt between the motor and the gears on newer lathes does not define it as belt drive even though it clearly is...... LOL!

I doubt there is really any significant advantage one way or the other for vibration. That's more of a quality of the machine thing than the type. I have both types. My belt drive lathe is WAAAAY rougher than my gear head.

It is much easier to change speeds on my gear head lathe.

There are also variable speed lathes. These also come in different types.

A VFD on a motor allows the motor to run at different speeds which could reduce the number of gear or belt changes required to achieve a given speed.

A VFD can also make speeds available that are not available through gear changes. The lowest available speed on my gear head is 70rpm. I would like 45 or 50. The easiest way to do that is to install a VFD which adds variable speed to each selected speed. (I'll deliberately resist the temptation to discuss torque and horsepower - LOL!)

I think it's probably best to think of belt drive as just an older technology, variable speed as new technology, and gear drive as something in between. But there is a lot of overlap.

I like the Idea of gear drive to get torque multiplication combined with a VFD to fine tune and add variable speeds.

That's just a, rough attempt at answering your question. The story gets more and more complicated as you discuss it in more detail.

Let the stone throwing and clarifications begin!
Click to expand...
You hit the nail on the head . I totally agree with your take on this. I would also like to add that a VFD on a belt drive may affect available torque at lower speeds.
 
Aliva said:
You hit the nail on the head . I totally agree with your take on this. I would also like to add that a VFD on a belt drive may affect available torque at lower speeds.
Click to expand...
Not if you still use the belt pulley change at the extreme end you can have best of both worlds.

And I forgot the advantage of a belt drive that I really like is how quiet they run. The belt driven lathes with an ELS look like a dream.
 
DPittman said:
Not if you still use the belt pulley change at the extreme end you can have best of both worlds.

And I forgot the advantage of a belt drive that I really like is how quiet they run. The belt driven lathes with an ELS look like a dream.
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My oil bathed gear head runs like a sewing machine. Uber quiet. Quieter than a belt.
 
I haven't seen any noticeable difference in surface finish between belt machines and gear machines (I have both).

For the simplicity in changing gear ratios I prefer a gear machine. I don't hate belt machines, but the gear ones are more convenient.

You will still change gears or belts even with a VFD. When turning an extra large piece, you need to gear down to get the appropriate torque. Leaving it there makes going to the highest speeds difficult and harder on the motor. I prefer to try to use the motor from 20% to 120% using the VFD, (that's 300RPM to just over 2000 RPM on the motor) Mill or lathe, you still change the belts(gears)...
 
Susquatch said:
CAREFUL! We don't need to be going down that rabbit hole again! At least give it a few months till the dust settles on the last round....... LOL!
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Ha Ha ya after the last month of you "sparky's" going at it over VFD's & ELS's had me thinking "man I'm a lot smarter now"....I deduced that those old boys with the overhead gang of belts had the answer right off the bat and them someone came along "with a better idea" and ruined it forever more.
 
On cost and quality, all the very finest of lathes in the tool makers category, Monarch 10ee, Hardinge HLV. Smart Brown 1024, Schaublin 120 and probably many more I'm missing are belt driven. Its not to do with era, all were made at the same time as, and priced above, the typical geared head engine lathe.

A geared engine lathe is a real convenience vs changing belts, but I have had instances of gear noise coming through in a finish which is why the above calibre of machine avoids them. Its rare and hasn't much bothered me, but I guess if you making a lathe just a good as it can possibly be, you make it belt driven so it doesn't happen. They still deliver on convenient speed control, through often complex infinity variable arrangements.

otoh you've got the cheapest of lathes that are also belt driven.....I guess my point is, speaking in absolutes is risky business in this space. :)
 
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Om my Taiwanese Generic(BusyBee) engaging and disengaging the back gear involves a pin on the spindle gear, the problem is the gear is pretty tight to the casting . This makes it rather difficult. And I don't have large hands either. Every time I struggle with it, I think a gearhead would be nice.
 
Mcgyver said:
.I guess my point is, speaking in absolutes is risky business in this space. :)
Click to expand...

Is speaking in absolutes ever safe? Heck, I would not even have weighed in if it were not for the dead silence from others.

There are always opinions, and it depends, the exceptions, experience, science, marketing, wives tales, and $.

Btw, I didn't know you could still buy a brand new belt driven lathe today......can you point me at one? I'd like to know more about it!
 
Reading through the posts I just wanted to point out . . .

The gear driven machine maintains ratios that are repeatable, important for thread cutting, gear tooth profiles and fixed pitch details.
The belt driven machine can SLIP . . . this can be a good thing if you need to absorb vibration for machining applications. The belt drive can be built with adjustable sheaves that could be set up for an INFINITE number of speeds without changing pulleys.

Gear driven heads require an accurately built gear train for proper meshing of teeth.
A belt drive is more forgiving because the belt can be tightened by adding a spring or lever.
 
LenVW said:
Reading through the posts I just wanted to point out . . .

The gear driven machine maintains ratios that are repeatable, important for thread cutting, gear tooth profiles and fixed pitch details.
The belt driven machine can SLIP . . . this can be a good thing if you need to absorb vibration for machining applications. The belt drive can be built with adjustable sheaves that could be set up for an INFINITE number of speeds without changing pulleys.

Gear driven heads require an accurately built gear train for proper meshing of teeth.
A belt drive is more forgiving because the belt can be tightened by adding a spring or lever.
Click to expand...
But is not the gear train for carriage travel on a belt driven lathe always driven by the spindle through gears? If the belt slips then the spindle doesn't move and then therefore neither does the carriage.
 
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