Eldorado Bridgemill (model previous to Tri-power)

I have a few questions as I explore the upgrade to a VFD.

1) Could I use a 2 HP motor
(would the stock bearings handle this HP upgrade)?

2) Are VFD motors reversible
(Do the controllers have a reverse function)?

Thanks in advance for any input along these lines.

Gary

Answering my own question regarding the motor reverse function.

As I am looking into a DC powered motor, reversing the polarity via contactors achieves the reverse function, but the Drive control will not directly do this.

If I was to use a 3 phase A/C motor then the Drive would be able to reverse the motor.

Bearing question remains and now...

New question : What are the the merits of using a 3 phase A/c motor over a DC motor?

Gary

There have been reports of the bearings getting warm/hot over 2000 rpm, there are upgrade bearings to suit if needed.
You can get the DC SCR drives with reversing capability without relay (4 quadrant drive).
A VFD is usually reversed by Contact input although some do have ±10 analogue input if needed.
The merits of VFD are brushless motor over DC, some complain of lack of torque at low rpm, this can be overcome by getting a good quality vector controlled VFD, they can also be obtained with an encoder input which not only controls speed accurately but provides torque at lower speeds.
Al.

Hi Gary,

I think you sent me an email, but my outlook has been eating my outgoing messages.

I actually did my VFD upgrade on the cheap because I am friends with an industrial electrician and he sold me the motor and VFD at cost. I’ll give you my best guess.

VFD: Mine was about 350 but you could find a different brand or a cheaper one. If you are going to buy nice motors, it makes sense to get a nice VFD in my opinion. It will help the motors last longer and provide a cleaner control signal. The VFD can either display volts, amps or frequency but none of that gives you RPM. A good industrial tachometer is expensive, in the several hundred dollar range but it will probably read down to 1 RPM. I got a 40 dollar cheapo Chinese one on ebay for 40 bucks that only resolves 100 rpm increments but it seems fine to me.

Motors: the ones I used retail for about 400 each. I know some people have used DC motors from tread mills and SCR speed controllers. You could put any HP motor on the machine but physical size will be a limitation. As far as the lathe, the bearings aren't intended for more than 2500 RPM (same for the mill) but I don't really have any need to run the lathe that fast. I've actually set mine up for a max of 1500 rpm and replaced the bearings anyway.

AC vs. DC: I'm not an electrical engineer or anything, but I don't know of any machine tool (commercial) that is powered by DC motors. I guess for me the main advantage was that you don't need a rectifier for AC. And, as mentioned, a DC motor has brushes that need to be checked, maintained and broken in and pre-seated if you are picky. DC motors do have "better" low RPM torque but I think we are talking about running less than 20% of full power. An AC motor should really be run at above 50% anyway.
Step pulleys for the motors: about 40 each on ebay, the only place I could find good quality ones (made in Canada). I think it's called "E motor store" or something like that.

25 Feet of Fenner Link Belt: about 250

I got all the material for the motor mounts for free and they would be difficult, but not impossible, to make on the shoptask.

I also got the control box for free, but you could make one or use any kind of enclosure.

The allen Bradley push buttons and switches retail for about 50 bucks each but are readily available on ebay for much less.

Hope that helps and let me know if I left anything out.

Cheers,
Jason

Just to clarify a few issues.

. The VFD can either display volts, amps or frequency but none of that gives you RPM.


There are several models that can give RPM as a readout, and if you have the encoder option are extremely accurate.


AC vs. DC: I'm not an electrical engineer or anything, but I don't know of any machine tool (commercial) that is powered by DC motors.

For many years, probabally 30~40 or so, CNC spindles and servo's were mainly all DC motors, it wasn't till the advent of sophisticated micro-processor control That AC VFD came into its own.
In fact there are many of the older DC machines that are still going strong.

DC motor has brushes that need to be checked, maintained and broken in and pre-seated if you are picky. DC motors do have "better" low RPM torque but I think we are talking about running less than 20% of full power.

??Torque is torque (current), DC motors usually exhibit max torque at zero speed and are fairly flat over the speed range, typically DC servo's/spindles in the CNC production environment would go 10~15 yrs without brush replacement.
I am not disputing the fact that VFD's are a boon, I have installed several makes and models, but there is nothing wrong with a good quality DC motor with SCR drive if it is the right price for spindle control.

I guess for me the main advantage was that you don't need a rectifier for AC.

Actually VFD's use a three phase rectifier bank and a large capacitor DC supply which SCR controls do not need.
Al.

Thank you both for your insight, I fear I have missed an opportunity as the 2HP Baldor with Rotary Encoder and Fenner M Drive is long gone...could have gotten that for about 400 including shipping.

Sounds like I could have done it and it would have been a good upgrade from the stock machine from what I have read...will keep my eye out for another deal.

The price seems right based on your investement Jason.

Gary

Found a great supplier of new surplus VFD and Motors.

I got 2 1.5 hp constant duty 3 phase motors and a TECO Westinghouse Fluxmaster model 202 rated at up to 2hp.

I will switch between lathe and mill motors and use the one controller.

Motors are 1800 RPM @ 240 3 Phase.

VFD is rated full power (No HP loss) at 240 1 Phase input.

I think I have only 230v from my local utility so that calculates out to 1725 RPM based on 60Hz. Although the digital readout cannot show RPM (without an outside signal) the calculations are easy enough to build a small chart to keep with machine...I am always looking at charts to figure feed speeds and depths of cut anyway, what's another chart. In time everything will be second nature I am sure.

Found this formula:
Speed (RPM) = (120 * F)/P

where F = Frequency (Hence the VFD)
and P = Number of poles the motor has.

Working backward my motor is rated 1800 RPM at 60 Hz so I deduce that I have a 4 pole motors.

So lets say I want a spindle speed of 100 and I am using a 1:2 pulley setup ( I will be working out want I want to us here as I want direct drive to the quill without running through the intermediate pulleys. Will use a link belt and think I can use a setup like the following 2:1 and 1:1 setup.

Using the 2:1 reduction pulley setup I would need a motor speed of 200 RPM.

200 = (115*F)/4

So... the frequency setting for 100 RPM on the spindle using the 2:1 reduction setup would be 6.96.

I may have to opt for a 3:1 reduction setup although the drive says it can provides constant torque, this remains to be tested on the machine. If nothing else I will be able to turn step pulleys in my sleep.

An interesting thing is that I can overdrive the motor without damage so if I have a direct 1:1 setup I can get ~2585 rpm using 90 Hz for the F setting.

Looks like I will be having fun.

Will let you all know how the install goes.

Gary

I will be doing the VFD on the lathe first I think.

Getting rid of all that mess in the left side of cabinet will be a dream.

Gary

On the lathe, you shouldn't have any bearing heat issues at high rpm because the spindle is splash lubricated with oil. On the mill spindle, I would recommend you remove it , clean the bearings and re-pack with a high quality moly grease. Some guys will replace the bearings with timkens at this point, and its not too expensive- about 15.00 each. But if you are going to re-use the original ones be careful with the bottom one. When pressing it out if you catch the edge of the cage it will pull it apart and you will end up buying new ones- been there -done that.

Most bridgeports only have 1.5 hp motors for their mills so 1.5 hp is all you need. Also you will have to deal with the extra weight of the bigger motor on the mill head. The 3 phase motors are lighter than the single phase ones that I used. I went with the 1.5 hp so I could use 110volt single phase input on the VFD drives. If you go more hp you have to go up to 220 single phase. Thats where the cutoff point is. The lathe can handle more HP and it might be an advantage in some machine operations. As for the mill spindle bearings their is nothing for the bottom bearing to catch on it comes straight out the bottom of the spindle. It is just a piece of junk and should always be replaced if you are serious about your machine and a VFD drive is only for the serious user.

We ran our machine on the chinese bearings for about 5 months with no problems- the TIR was under 0.001". But we had a real problem with fine sand- it seemed to be every where no matter how you tried to seal up the area- computer keyboards were always gritty- even in the coffee. During one of the quiet times we decided to re-pack the spindle as "preventative maintenance" ( had nothing else to do). We pulled the quill and took it to maintenance to press out the bearings- those guys were used to doing a lot of heavy stuff and not re-using things, so this little item was just slapped in the press- unfortunately they did not get it clear of the press plate and when the shaft came out it pulled the cage off the bearing. All the races were fine, and I actually considered putting it back together, but it so happened that it was a stock size we had in parts. Once it was all back together, there was no real difference in TIR or heat, but we managed to keep busy for a day.

There was nothing in the way when I removed these bearings. The cage was already distorted before I removed the spindle from the spindle sleeve. I used a plastic block and taped the spindle out. The bearings just fell out along with the cage. As for the Lathe spindle bearings the rear bearing had to much ID clearance and the front one was so tight it took forever to get off. The new bearings fit just fine. I feel that the mill spindle sleeve could have been machined better. I had some rough machining marks not as smooth as it should have been. I do have a question What are they using to lubricate between the spindle sleeve and mill swing arm. It seem to me that it needs a seal at the botton of the spindle sleeve to keep out metal shavings.

Hey- that could have been a picture of our spindle! I was taught to always use a press and never hammer on a spindle, but I must admit that at times I have " gone caveman" when I didn't have access to the proper tools. I see the top bearing and race seem to have come out complete- On our machine there was no notch cut into the quill to drive out the lower race. The guys in maintenance had that one figured out though- they just used a welder and welded a few places around the inner diameter of the race and it shrunk up enough to drop right out. Those heavy equipment guys do have some good tricks. Our machine had a saw cut in the back of the casting with 2 tabs and a lock handle, so when you tightened the handle the casting squeezed around the quill to lock it in place. This saw cut would get sand in it, so we just filled it with grease to seal it up. Around the quill, we found a piece of inner tube and used a tin can as a punch and cut a hole in it- then just used scissors to cut around the OD and made a primitive seal. We stretched it over the quill and siliconed it to the casting. It was kind of crude looking, but it kept everything out. I don't think you need a seal for normal work unless you are doing a lot of grinding on cast iron.

First off a press is used when no other method can work. The delrin plastic protected the quill and did not damage anything. It alowed me to tap out the quill slowly and not drop it to the floor . That almost always happens in a press when things dont go right. As for the lower bearing race. I used a torch with a small tip and heated the outer race and as it cooled is it sliped right out. The inner race I heated it until I could tap it off without harming the spindle shaft. If you press off the inner race without heating it it can sometimes gouge the shaft and you will lose some of your bearing press. We always do this when we pull off bearings on our steam turbines. We cant afford to repair a rotor shaft from not being careful . A press can cause more damage than its worth. It is used when other options have failed.

Speaking of bearings, here is a story that's a bit off topic, but current to today's news. I had an uncle who was a big " buy American" person all his life. He always bought Buicks when most of our family rode in Fords or Chevys. It was always fun to visit my cousin and ride in his dad's car. During the first gas crisis in 73-74 when prices went from 35 cents up to 70 cents per gallon, my uncle got into a panic because it was costing him 15.00 to fill his tank. Like millions of other Americans he put his patriotism aside in favor of his wallet and began looking for economy cars. Japanese cars were out of the question for him, but other " furrin" makes made by white people were OK. He settled on a Fiat sedan that got about 40 MPG, compared to the 15 for his Buick. When he traded in the Buick, I think they paid him by the pound- practically nothing. Anyway, here is the bearing story- within 6 months, he had taken that Fiat back to the dealer so many times that he was spending more in gas going to and from the shop than he was using in the old Buick. They replaced every single wheel bearing on the car in that time, plus a bunch of other problems. The funniest of them were the window winders which were a sort of cable and pulley affair which would come off the tracks with a cartoonish " sproing" and the window would drop out of sight. He struggled along with that thing for 2 or 3 years, always puffing out his chest to everyone and bragging about his great gas mileage. Eventually people got used to the 70 cent gas prices and bigger cars began to come back. Just before he passed away he traded the Fiat in on a new Buick and of course the dealer gave him zip for the Fiat.

Well I own a Jeep JK 4 door. It had to be reworked to make it off road worthy. I have always owned a Toyota. But I wanted a jeep this time. I am happy because everyone makes parts for it even though its new. Everthing is metric on it and so are most cars these days. My point is why is it so hard to find metric nuts and bolts locally. And metric tooling is like a foreign language to most tool places. Yes they have a few items but they are still pushing standard size tooling. Even at work everthing is going metric because we dont make anything in the US anymore. It seems they would get it together and standardize everthing like they tried thirty years ago but failed.

Not sure where you live, but every auto parts store and Home depot around me carry metric nuts and bolts. Bearings have been built to metric standards for years, of course they still make inch sizes for older products and will continue until there is no more demand. Also, gotta disagree with you on the press issue- I was taught to always use a press as well. A press gives a steady shock free pressure to remove and install parts. If needed you can use a torch in conjunction to aid the process, and of course always put your drop table under the part so it doesn't hit the floor. I cannot imagine you are planning to use a hammer to install your new bearings. It reminds me of that old urban legend of the guy who needed a push to get his car started. He asks a lady to push him and tells her that his car is automatic, so he needs to be going 35 mph before it will start. The lady then backs up and hits him going 35mph.

Fastlane,
I remember that old story about the 35 mph push start along with the one about the cement truck driver who caught his wife with a guy in a cadillac convertible and filled it with concrete. I also have a true story along the lines of your Fiat/Buick uncle. A friend of mine dreamed for years of owning a new pickup. When he finally got to the point of being able to buy one, he went all out. He got a fully loaded 1 ton dually with crew cab, 4 wheel drive, air, power etc. Every option they could pile on it. I think the thing cost him about 40,000. That was 5 years ago, and he used to beam with pride when he drove around, that truck was his life's dream. In the past couple of years though it has all changed. With gas prices going to over 3.00 per gallon, it now costs him about 150.00 to fill all the tanks. Now he hates his truck- always saying how this POS costs him so much to drive etc. He seems to be blaming the truck for the high gas prices. I guess some of his attitude is natural, since the newness of owning the truck has long ago worn off, but its really strange how his life's dream and his pride and joy have become a constant source of anger over this one thing. I tried to tell him that its the same truck he dreamed of years ago, and now that its all paid for, the cost of the gas is really not that big of an issue, but he seems so focussed on his unhappiness that he doesn't listen.

Well pictures tell the truth and I have alot of them and will post them as needed.

To Gfull60,
You mentioned you got a good deal on your VFD drives- can you pass the info along? How did the whole thing work out? I'm having a ball with my new machine, but still thinking of going to a variable speed drive out of laziness.