Replacing with Brush or Brushless DC motor

Don't apologise for being off Motor topic, as you are still on Home Model Machinining topics, So reading with interest. - It is a "chat room", so must have allowance for multiple ideas within the chat...
K2

Steamchick said:

Don't apologise for being off Motor topic, as you are still on Home Model Machinining topics, So reading with interest. - It is a "chat room", so must have allowance for multiple ideas within the chat...
K2

Click to expand...

I agree

Dave

Just a final note on my lathe conversion to the 750W, 3 phase, variable speed sewing machine motor: It's much better to run and cut metal than the original brush motor. Feels smoother.... hard to judge really, but that's my impression.
I am sure there is much better torque, especially at lower speeds, which is a real benefit.
I haven't tried to overwork it (yet) and find the limits.. but for the "regular" sorts of job I do - making brass fittings smaller than 1/2in OD. it just feels like a "new" lathe!
I fitted the emergency stop that came in the post last week. NC contacts of live and neutral to Open when you hit the E-stop, and it locks. Wired on the main power to the controller, it means the "controlled rapid stop" built in to the controller (programmable? - If I understood Chinese?) is disabled, so the chuck slows by whatever friction exists, in the event of a disaster that could be damaging, except there is not so much rotational energy in the rotating chuck, and when a leg is ripping off a limb it is hard to remember to hit the E-stop anyway! - The extreme pain and loud screaming seems to paralyse thinking in such situations. (So I am told!). - But The Emergency Stop is fitted.
I shall normally use the speed control wound to zero as a stop, then switch power OFF at the variable speed controller red On/OFF switch before handling chucks and tools, etc. Just need to train the brain that the E-Stop is not the regular "go and stop" that it was previously.
I fitted the old speed read-out display but it seems the power pack for that was effectively blown-up by the previous motor and Variable Speed units' high voltage spikes! The red display does not illuminate at all.
So that's the end of this story from me - I guess?
K2

SmithDoor said:

Here is photo of a Cat forklift had a little twist.
I am taking photo
The forklift weighted 35,000 pounds before the counter weight is add in back.
The forks are 8 foot [2.44 meters] long and 3½" [89mm] thick . The engine is a Cat 3208
View attachment 158629View attachment 158630View attachment 158631View attachment 158632View attachment 158633
Dave

Click to expand...

Our family lumber mill had Clarkes about that size, and we use to drive them around the lot when we were kids.
Not sure why we were allowed to do that, but we could.
I think they used Detroit Diesel engines, either 453's or 471's.

I learned to drive a manual transmission, I guess when I was five.
They also had Hysters, same size, and they were automatic, with a large pedal, and you stepped on one side of the pedal to go forward, and on the opposite side of the pedal to reverse.

We had a lot of fun driving those around.
.

I have started some maintenance on my lathe and among others cleaned my motor inside. Unluckily, my brushes have different dimensions. 9.77 x 4.38 x 16,25 as measured; they could be 9.8 x4.4 x16....mm native. Luckily, they seem to still have life in them. The motor has 370W nominal. Fun fact, there's an idiot interference between the ground connection screw of the motor and one of head attachment screws. Because of this, motor alignment is a pain.
Anyway, I have already ordered the 500W brushless servo (please don't tell me the 750W one was just a few bucks more) and I expect a big leap forward when it will be fitted.

There is one thing puzzling me. Time ago I have fitted a capacitive DRO - Igaging style- along the bed. At the beginning it worked fine and I was very happy with it, but soon it started jumping and shifting. Here, on the forum, it was said the correction is to insulate completely the unit from lathe's ground. But I have metal brackets fixed with metal screws to connect it with saddle. How can I provide rigidity to the structure and simultaneously insulate it electrically?

NapierDeltic said:

I have started some maintenance on my lathe and among others cleaned my motor inside. Unluckily, my brushes have different dimensions. 9.77 x 4.38 x 16,25 as measured; they could be 9.8 x4.4 x16....mm native. Luckily, they seem to still have life in them. The motor has 370W nominal. Fun fact, there's an idiot interference between the ground connection screw of the motor and one of head attachment screws. Because of this, motor alignment is a pain.
Anyway, I have already ordered the 500W brushless servo (please don't tell me the 750W one was just a few bucks more) and I expect a big leap forward when it will be fitted.

Click to expand...

Good! I think you will enjoy the torque of the lathe better than before? - I hope you are as happy as I am with my change. (NO problems - yet!). I reckon you have sized the motor reasonably.
Take care if cutting "harder" than previously, as I have had lathes for 120W or 1/4HP motors that twisted when I took "bigger" cuts in very low gearing. It's not the motor power, but the gearing and torque applied at the main-shaft (by the tool) that twists machines and loses accuracy. Heavier (Larger industrial) lathes don't do that until you get a HUGE torque applied that tend to break the job or tools! You may find you have double the torque compared to the original motor, especially at the lower speeds. The brush motor will have been limited by the current the controller delivered, and at lower speeds (the bottom 20%?) the torque will have dropped considerably, Not so with the new motor and controller. The design is such that the torque at the low end is much better (less drop-off) compared to the brush motor. And you are starting with "35% extra" anyway... due to the extra power rating... Seems like a sensible choice to me...
- I always found "My" cutting speed and the "text book" rpm varied job by job. Sometimes text book was OK but sometimes not. So it isn't really a problem having "Motor speed" - that I divide by 4 to get my main-shaft speed (pulley ratio). as I tend to tweak the speed of the lathe to suit what I am doing anyway. e.g. facing a large diameter, or parting, both need speed changes as one approaches the centre/smaller diameters. But for a parting tool the amount projecting from the tool holder can be "a bit long" on larger jobs so needs much lower speeds to compensate. - Not the same speed as facing the same diameter where the tool is much better supported. That is a lathe issue, not a motor issue.
Perhaps the only thing I need to get used to is the fact I won't be able to rely on stalling the motor when using the lathe at the slowest speed to cut threads with dead ends. It was convenient that cutting a 1/4in thread I could hit a shoulder with a tailstock die and the lathe would stall... But maybe that is what developed the motor faults eventually? - The new motor will probably strip the thread and not stop! So that must be done "by hand" in future.
And hitting the STOP button previously was a quick stop. Now the quickest stop is by using the OFF switch on the controller, but that has a bit of run-on.... so getting used to that as well..
Take care, and enjoy the new motor!
K2

NapierDeltic said:

I have started some maintenance on my lathe and among others cleaned my motor inside. Unluckily, my brushes have different dimensions. 9.77 x 4.38 x 16,25 as measured; they could be 9.8 x4.4 x16....mm native. Luckily, they seem to still have life in them. The motor has 370W nominal. Fun fact, there's an idiot interference between the ground connection screw of the motor and one of head attachment screws. Because of this, motor alignment is a pain.
Anyway, I have already ordered the 500W brushless servo (please don't tell me the 750W one was just a few bucks more) and I expect a big leap forward when it will be fitted.

Click to expand...

It always comes down to weeks link.
With mini lathes it is belt .
All torque need from motor is so belt just slips.
Manufacturer will put bigger motor for advertising

Dave

Thanks Steamchick; can't wait for the new motor to arrive!
In what concerns cutting speed, I'm not as careful as you and I have never learned to use speed diagrams; but working a lot with HSS, I have got the habit to run rather slower. My lathe came with a set of carbide brass-welded cutters, but they were less forgiving with beginner errors.
Dave, I'm not MotorMouse; even on the road. For the lathe, with its small motor, I have learned what means patience.
I agree with you, the weakest link will be the belt; I have also changed the headstock gears with metal ones, so it is obvious which is next suspect. But first, let's see what happens with the motor.

A correctly sized belt, properly set and not worn out, should handle all the motor torque adequately.
Experience shows almost all slipping belts are either worn, or badly set-up.
Millions of Vee-belts use in industry that do n slip prove how good proper drives are. Toothed belts - for precise consistent timing, are as reliable as any, but many have negative experiences due to exceeding the normal expected lifetime until the belts fail. Correct servicing means trouble free use.
Flat belts, rope drives etc. Have mostly been superceded - but were more prone to slippage. I had a lathe with a flat belt 3 speed drive. Never gave me a problem at the correct tension. The 1/2 hp motor on a 4in swing lathe was way too big. But the belt never slipped when properly tensioned. (It was Slackened for changing gear, so regularly re-tensioned.).
K2

Once, v-belts were the rule in the car engines. With proper adjustment, they were trouble-free for many years. For toothed belts, only safety reasons require faster than normal change.

One of the strangest (?) applications I saw for a toothed belt was as the lift chords for a car lift (high speed) in the factory. Cars at ceiling level were lowered to the floor level on a hoist that had been replaced so instead of chains, the new hoist used large toothed belts. Really much quieter (presumably cheaper?) than the previous chain hoist? As lifting gear it will have been sized, maintained and tested to a schedule, but the cars were moved much faster than the previous chain lift. it lowered car in just a few seconds, and lifted the empty carrier back up similarly. - More than 1 car per minute for production schedule: The hoists had dwell at top and bottom while the lift mechanism lifted the car off the high level carrier, then loaded it onto the ground-level carrier. 4 belts took the lift load, and toothed belts were used to ensure a corner didn't slip/drop and misalign the car being carried.
An example:

Double mast tooth belt lift: ​

https://www.schwingshandl.com/en/solutions/lifts/zweimastheber-zahnriemen​

Of course, there will be thousands of different uses for Belt drives, demonstrating their versatility and reliability.
K2

Car crashes in solid obstacles - one I have acknowledged recently on TV - remind me tremendous importance of deceleration which influences overload.
Tooth belts absorb energy and protect the other elements in a kinematic chain. And this prolongs equipment life.

Interesting comment Napier. I do know about noise generated as teeth fill slots rapidly, then vacate slots similarly, creating high frequency pumping noise, and about heat loses from the belts as flat large radiant surfaces, also rapidly passing through the air for conductive cooling, but I only surmised that they were poor for shock loading as the belts are positively tensioned so the slack side is still in tension on full transmission loading. - unlike chains that can have a slack side....? Or vee-belts that can absorb a shock impulse by pulling further into the pulley as a wedge? But all drives need shock absorbers in the driven (load) end if the load can produce shocks. The belts all contain chords that resist the tension and can be damaged by shocks. - or damage the surrounding elastomer! Or so I understood?
Can you explain more? I am not an expert on these things, just a casual dabbler... so willing to learn.
Ta,
K2

I mean vs gear trains. Let's take this: If something blocks the mechanism instantly, the shock is very high, both in gears and in bearings. Even if there are no instant effects, the usual materials of transmissions are hardened or anyway have predisposition to micro-cracking and metal fatigue. Even if we don't take only this extreme case - used for demonstration, overloads (instant change in resistant torque) use to follow a hyperbolic distribution occurrence -overload. Over one overload limit, they generate irreversible micro-damages which accumulate. Because they are flexible, the belts extend in case of shock, spreading overload energy to a longer period of time. It's what seatbelts do (to use an analogy). Thus, occupant does not react like a rigid fixed component of car body, but suffers a slower deceleration. Funny to compare human brain with a ball bearing steel ball . But they both have their limits.
Rubber/chords are the best combination for tyres also and they do what they know best -shock absorbing. In fact this is a good analogy. If you would have steel tyres , they would quickly be dented, damaged, destroyed by overlapping micro-overloads (not only them but entire drive train); not to mention the comfort...
Usually, shock absorbing is judged only as a geometry shifting. It is ignored that this shift is done in time and its purpose is to slow down the geometric deformation duration. You actually divide shock energy until it transforms from a distructive shore tsunami to ocean tsunami wave which slowly moves a boat up and down. Obviously both tsunamis contain the same huge energy.
For us is easy to understand what we can observe daily and vice-versa. Spreading an event from 5ms to 50ms is unnoticeable but all effects which have time in their formula under "/" will be divided by 10 which translates to 10 times smaller peak values. This can make the difference!

Steamchick said:

Interesting comment Napier. I do know about noise generated as teeth fill slots rapidly, then vacate slots similarly, creating high frequency pumping noise, and about heat loses from the belts as flat large radiant surfaces, also rapidly passing through the air for conductive cooling, but I only surmised that they were poor for shock loading as the belts are positively tensioned so the slack side is still in tension on full transmission loading. - unlike chains that can have a slack side....? Or vee-belts that can absorb a shock impulse by pulling further into the pulley as a wedge? But all drives need shock absorbers in the driven (load) end if the load can produce shocks. The belts all contain chords that resist the tension and can be damaged by shocks. - or damage the surrounding elastomer! Or so I understood?
Can you explain more? I am not an expert on these things, just a casual dabbler... so willing to learn.
Ta,
K2

Click to expand...

It cost lost to make gears quite. Even the chain and noch type belt will a lot noise at higher speeds.
When purchasing a mini lathe I want v- belt or poly-v to keep noise down. I did know belts slip too.

Dave

In fact I love so much varispeed (or whatever its comercial name would be) based on simple V-belt that, If I hadn't go for that brushless servomotor, I would have tried a way to get it for my lathe:

Neat.
But I hate to hear about comments of "belt slippage...". Something is NOT set correctly in most cases if belts slip. (User, not machine!).
The "Vee" is designed to grip under tension from pre-tension PLUS Load tension. Inadequate pre-tension can cause the belt to slip. Or dirty pulleys, or a worn belt where the flanks of the belt are worn (sometimes down to a fabric layer!) thus reducing belt pre-tension, or the belt has lost its durable rubber surface, can also be a cause of slippage.
There is a natural "creep" of the belt as the belt wedges into the vee of the pulley and out again, which is why the shafts do not remain synchronised. This is only a couple of percent per revolution. To rationalise wear on a Vee-belt, pulleys may not have a "divisible" ratio, but a pair of prime numbers, so the belts naturally change relative position on all pulleys at each belt-turn. But then some designers do not understand this and go for simple 2s, 4s, 12s etc that will all develop some non-uniform "resonant" wear patterns given long enough. These uneven wear patterns can cause a resonant torque vibration - that can cause "chattering" patterns on lathe work at very fine cuts. But it does not matter a jot when a car engine is driving an alternator, etc., except the service life is shortened. (Cost for the customer!). I think the effective radius of a vee-belt in a vee-groove is part way into the groove, so it is difficult to determine "actual" pulley ratios without knowing the geometric rules for determining the effective radius of the pulley.
Please correctly set belt tension and keep pulleys clean and you should never see "Slippage".
Suffice to say, I have experienced belt slippage on my pedestal drill, bought second-hand, and I am still using the old, worn belts - knackered by the previous owner. But when properly tensioned, the belts do not slip.
Regular Servicing and Maintenance saves cost of worn stuff. But on my lathe, bought new and regularly maintained, the motor always stalls before belts slip. No apparent wear on the belt either.
K2

Thanks Napier. I appreciate all you are explaining. In fact there is a natural "shock-absorbing" effect - as you explained - in all "belt" drives:
Vee-belts pull deeper into the grooves, and elastomers between fibre chords and pulley surfaces will deform - which allow those extra msec to reduce peak impulse. Toothed belts have elastomers between fibres and teeth, and generally the teeth as well, that deform to allow some extra msecs., and all fibre chord drives have braided or wound fibre chords that can compress their fibre bundles and add those msecs. Chains have steel (or other) fishplates and rollers than deform microscopically, but also have the "slack-run inertia" to absorb energy from an impulse... - that one is very complicated, but makes the slack (return) side of chains "jump" from the natural dynamic curve if there is an impulse in the drive run. The micro-cracking etc. that occurs - as you explained - is simply "fatigue life shortening".. and is usually hidden until the component fails... The same occurs within over-stressed chords and elastomers in all belts. (And in steel belts and chains... e.g. the steel "vee-belts" inside Nissan CVT drives, that work in compression!).
Very complex, and I was told a lot by a drive expert that I have never understood or otherwise forgotten...
Thanks,
K2

My 550W motor has arrived. I will not hurry to install it as I just have cleaned and checked my lathe and it is still going strong.
I will take my time to prepare mounting bracket and pulley.
On another hand my instructions are in Chinese only so I have to check for English version or some tutorials.

Mihai