my lathe needs more torque.

[Wizard69]

Hi MCRIPPer
Wizard69 has covered the alternatives very well for modifications or additions.
I can understand that that you are somewhat frustrated with moving from a large and powerful lathe to a small benchtop lathe having done the same excercise.

I leave a Hardinge HLV at work to a 9X20 at home so I know the feeling well.

"Poly Vee Belts" and pulleys are easy to fabricate and fit and fairly compact.

Poly Vee belts are excellent for these types of machine tools. With all low speed belt installations you need to make sure you don't exceed the belts ability to transmit the torque.

Gear it down if you need more torque at low speed use stepped "Poly Vee Pulleys" to give a selection of ratios.

Eric

I'd shoot for a ten to one reduction. If that doesn't stabilize low speed cutting a more detailed review of what is happening is needed.

 

[mu38&Bg#]

What kind of depth of cut and feed stalls this machine, why not reduce them? At 100RPM the total power available from the motor is very small. Low power means low metal removal rate. This just means you have to use it accordingly.

 

[Alchymist]

Hi MCRIPPer
Wizard69 has covered the alternatives very well for modifications or additions.
I can understand that that you are somewhat frustrated with moving from a large and powerful lathe to a small benchtop lathe having done the same excercise.
"Poly Vee Belts" and pulleys are easy to fabricate and fit and fairly compact.
Gear it down if you need more torque at low speed use stepped "Poly Vee Pulleys" to give a selection of ratios.

Eric

Poly V-belts are the cat's meow, and work quite well on flat pulleys, believe it or not. Makes the fabricating of the pulleys much easier. I run a 1" belt on my old South Bend 9", and a 1/2" on my homemade wood lathe. The half inch works quite well on a pulley down to about 1" diameter, I haven't tried anything smaller.

 

[MCRIPPPer]

you mean poly v belts like the ones that drive power steering and alternator in cars? what is the smallest size i can get in those?

 

[Alchymist]

you mean poly v belts like the ones that drive power steering and alternator in cars? what is the smallest size i can get in those?

Yes, those types. Did a quick check on the part number I used for the small lathe, it was 250K3, which is 7/16" wide by 25.5" around. There are smaller, I don't know how small they do go. Here's a link:

http://www.vbeltsupply.com/ecommerce/250k3.html

 

[velocette]

you mean poly v belts like the ones that drive power steering and alternator in cars? what is the smallest size i can get in those?

Hi
Poly Vee belts are 2.34 mm pitch and available from 406 mm to 2210 length

Have attached a PDF file you may find useful. Plus a photo of my belt drive conversion on an X2 milling machine.

Have fun and enjoy your hobby

Eric

View attachment polydrive ribbed.pdf

 

[Wizard69]

Hi
Poly Vee belts are 2.34 mm pitch and available from 406 mm to 2210 length

Actually Goodyear has 5 different pitches available with two of those being special order. Of course there are other manufactures out there. Poly V belts are becoming very popular showing up in tools like cut off saws or in support equipment like blowers.

Have attached a PDF file you may find useful. Plus a photo of my belt drive conversion on an X2 milling machine.

That conversion looks awesome. I take it that you did the pulleys yourself?

Have fun and enjoy your hobby

Eric

In the end being happy is what it is all about. There are many ways to cook this goose, if I remember right somebody out a planetary gear head on his lathe. That is a little much compared to the cost and effort of a belt drive though. Personally is be tempted to go the big motor route with a variable speed drive. The thing is I can't select the best option for him, that is why manufactures like Goodyear have web sites - it gives you a chance to grok what is right for you.

 

[Wizard69]

you mean poly v belts like the ones that drive power steering and alternator in cars? what is the smallest size i can get in those?

Refer to the catalogs from Gates, Goodyear and so forth. Here is a chart that covers the 3 common belt sizes and horsepower transmission: http://www.gates.com/downloads/down...CSSguide.pdf&folder=brochure&location_id=3107. If you have a Windows machine there is downloadable software to help you engineer a solution.

Another nice feature of Poly V is that you don't have to vary the angle of the belt grooves as sheave diameter varies like you would for standard V belts. This means you can grind one tool to machine all of your pulleys using the same class belt.

In any event you should read up on design issues. For example minimal size pulleys for your motor. A pulley that is too small on a motor can lead to overloaded motor bearings due to excessive tension on the belt. So it is desirable to follow guidelines and avoid motor pulleys that are too small.

 

[MCRIPPPer]

ok, we are getting somewhere. i have researched a little and have decided the best choice would be the poly v j section belts. but what number of ribs? i wonder if local auto stores would have the j type belts?

 

[DJP]

I am not familiar with your lathe but here is an idea from a solution that I used to slow down an industrial sewing machine. A small length of pipe was bored out to hold two bearings and a tab was welded to mount it on the table. On the shaft I placed a simple two gang pulley where the larger diameter is driven by the motor (under the table) and the smaller one drives the sewing machine. Alignment of the belts was possible within the adjustments in the motor mount.

If you want to use automotive type belts consider visiting a wrecker to salvage alternator and power steering pulleys and weld them together. You should get at least two times speed reduction and more torque. Best of all, if it doesn't work just scrap it and go back to the original set up.

Just an idea for your consideration.

 

[steamboat willie]

Hello there! I would be careful applying more torque to the lathe . I know the mill has plastic gears and I suspect that the lathe has similar which may not react too kindly to increased torque being applied through them.
Just a thought.
Bill.

 

[MCRIPPPer]

my lathe has no gears for the spindle, just has a pulley on the spindle shaft that is belted right to the motor.

 

[Nitrous]

my motor is brushless so i cant run it right off a car battery, and besides, the motor needs something like 90v to work right. the mini mill you had used a universal motor, which will run off ac, and dc.

i know my motor is wired right. it does not run rough as if it had a dead spot like if a phase was missing, but you can clearly hear when it switches onto the next magnet and the motor torque changes. im talking around 100 rpm here, so the motor is spinning very slow! i can not hear the actual electrons tho lol.

this thread is turning into a diagnosis of non existent problems lol. the problem is my motor is low horsepower and even lower horsepower when it spinning slow, so i wanted to know if others have done anything about it via gearbox or belt.

i want to be able to turn things slow for my 4 jaw and other things that are large diameter, or off center.

I know this is an old thread but you may want to consider the following with respect to BLDC motors and controllers.

When you use a cheaper motor control with these motors, they often use a sensorless control mode which detects rotor position by detecting the back EMF in the unpowered coil. Trouble with this is that the back emf is not really significant at low RPMs. Without sensors, the motor needs to be run up to fairly high speeds before the controller can actually drive the motor effectively.

A better choice is to use a "Sensored" motor and controller. These are commonly seen in the RC world of model cars. There needs to be good torque even at very low RPM.

Interestingly, Hall Effect Sensors can be added to sensorless motors after the fact, allowing for high torque at low RPM. Of course, the controller must also be a Sensored controller for this to work.

Efficiency improvements can be derived from changing from a Square Wave to Sinusoidal drive controller. This can often be done as part of the same upgrade, but the optical or magnetic sensor array (typically three in a 3-phase BLDC motor) is what will solve your low torque at low RPM problem.

Doug

 

[chucketn]

I have added a jack shaft speed reducer to my 7x14 lathe since this thread started. No more stalling the lathe on mid sized cuts. Don't have specs on depth of cut, but my setup is happier! I had an issue with the controller before I made the jackshaft. Had the controller repaired and with the jack shaft, have had no stalling problems since.
I do now have an issue with vibration in the motor mount. I need to make a jack or something to stabilize the motor, as it reacts greatly to the increase in torque.
Chuck

 

[Dunc1]

Changing the motor pulley (on the 350 watt motor version) from 17 to 12 teeth provides 28% torque increase (comparable to that provided by the 500 watt motor). Details in Home Shop Machinist Vol 32, #3 (May/June 2013).
I have not tried this mod, however.

 

[Brian40]

After cooking 3 control boards on my 7X12 I decided a different approach was required.
The lathe now has a 1 hp reversible motor, steel gears, taper bearings. alloy drive belt gears, and a jack shaft reducer to give 10 speeds,
The lead screw is powered to provide variable feed rate so I do not miss the variable spindle speed at all.
When testing it's capability's I found that if I overloaded it the motor drive belt slipped, so no breakages
Some of the mods on this lathe are on my web site (see below )feel free to down load any of the mods.
Brian

 

[Wizard69]

I have added a jack shaft speed reducer to my 7x14 lathe since this thread started. No more stalling the lathe on mid sized cuts. Don't have specs on depth of cut, but my setup is happier! I had an issue with the controller before I made the jackshaft. Had the controller repaired and with the jack shaft, have had no stalling problems since.
I do now have an issue with vibration in the motor mount. I need to make a jack or something to stabilize the motor, as it reacts greatly to the increase in torque.
Chuck

Maybe an over center belt tensioner.