|ANDREW PARKER||27/03/2013 12:56:23|
|4 forum posts|
Hi chaps, over the last 2 or 3 years I have managed to burn out 2 motors on my milling machine. In both cases the motor casing has become very hot to the touch. I dont really know what has caused the motors to fail as I dont really push the machine very hard. The second motor failed while I was taking thin cuts off a piece of aluminium. The only thing that may have caused it may be that at times I have run it for up to half an hour at a time. I prefer to take multiple thin cuts rather than fewer big cuts. The reason I am posting this thread is to ask if anybody knows of any other suppliers of motor that would bolt straight to my mill without any modifications. As I have alreadry bought one replacement motor from Chester I am reluctant to buy another. Has anybody else had similar problems with this type of mill.
|1037 forum posts|
The motors on these mills should be capable of continuous running, I had the Warco equivalent for a number of years (ZX15) and never had motor problems.
I have seen these motors fail because of poor quality start capacitors or a dodgy centrifugal switch.
Have a search on ebay, there are numerous suppliers of single phase motors suitable for mounting on this machine.
|Ian S C||27/03/2013 13:19:24|
7468 forum posts
Sorry I can't help you from here Andrew, But I see you are getting answers. Ian S C
Edited By Ian S C on 27/03/2013 13:22:23
|john fletcher 1||27/03/2013 14:39:22|
|617 forum posts|
I've just been attending to a friends motor which has a failed start capacitor, nothing otherwise wrong, with the windings or switch. The working voltage was 260 or so it said on the casing, should be at least 400 volts. But as your motor got very hot, it seem that the centrifugal switch wasn't opening leaving the short time rated start winding in circuit when it should disconnected. These Chinese motors and I think it would be, are quite easy to dismantle, remove fan end cover and the plastic fan, which is pressed onto the shaft, then remove the screws and end shields on the shaft end and there is the start switch. No need to mark the motor end shield as one would with a 4, though bolt British motor. Replacement capacitors are available from RS Farnell and others and should be an AC electrolytic type. I think you ought follow Graeme advice.Ted
|Martin W||27/03/2013 16:49:11|
|854 forum posts|
The motor on the Chester Champion Mill, if the same as the items now offered by Chester, is a DC motor which is driven from a speed controller. The problem with these motors is that if they are driven moderately hard at low speeds then the armatures tend to over heat and the windings fail. It would seem that the motor's internal fan is not particularly effective even at normal speeds and virtually ineffective at low speeds. This is compounded by the fact that the effective I2R losses/heating can increase if the motor is loaded at lower speeds when the fan is not performing thereby making the problem worse.
This problem has been subject of several threads on the forum at the Chester web site. I believe that virtually all mills/lathes using this type of drive, irrespective of supplier, are susceptible to this problem. One way to alleviate this would be to fit a small computer type of fan to the motor in order to increase the airflow, however there will be flow conflict if the motor is run in reverse .
I have a mill and lathe that use similar motors and to date while they have got quite warm they haven't, as far as I am aware, overheated significantly. There may be some merit in running the motor at full speed with no load for shortish periods of time when it is being used for longish periods. An ad-hoc form of duty cycling in order to remove some of the heat.
I have run both the mill and lathe for periods in well excess 30 min with no problems. I tend to use the lowest (back) gearing so that the motor runs as fast as possible for a given spindle speed.
Edited By Martin W on 27/03/2013 16:59:22
Edited By Martin W on 27/03/2013 17:05:15
|Stub Mandrel||27/03/2013 19:10:58|
4311 forum posts
There's a thread all about this, including a succesful fan modification by Johan Crous HERE
I think the champion mill is essentially the same as my X2 and Johan's mini-mill.
|392 forum posts|
As to an external fan fighting the internal one when running in reverse, I found that the one I fitted to my lathe won the battle every time. Even at high speed, the internal fan produced a very weak draught. Anyway, I don't think milling machines are often called on to run in reverse, but that opinion may be coloured by the fact that mine has no provision for it.
Sadly, computer fans won't go backwards; if you reverse the supply polarity, they don't run at all.
|Les Jones 1||27/03/2013 21:00:05|
|2152 forum posts|
If there is room why not fit two fans back to back and power the one that blows in the direction to assist the motor fan. If a small changeover relay was fitted and the coil driven via a diode and resistor from the motor supply the fan selection would be automatic. A zenner diode would also need to be connected across the relay coil to limit the voltage when the motor voltage was high,
|Keith Long||27/03/2013 21:08:33|
|842 forum posts|
Rather than trying to fit 2 fans back-to-back and hoping that you'll get a decent draught past a stationary fan - you may or you may not - you could remove the original motor fan, and then just use a single external one run from a constant supply that doesn't depend on the motor speed or direction. The motor won't care that the air flow is always the same direction.
|Stub Mandrel||27/03/2013 21:09:25|
4311 forum posts
Interesting to see yours and Mike's solutions to increasing cross slide travel on a mini lathe.
My solution was similar to Mikes and also in two parts: First - round the end of the feedscrew nut so it can travel all the way into the milled out pocket for it, second - mill a pocket in the cross slide so it can overlap the index.
|David Jupp||28/03/2013 08:23:08|
|737 forum posts|
Re internal fan and direction of rotation. Many internal fans in motors are simple centrifugal fans with straight blades - these work equally well in either direction, and force the air in the same direction regardless of rotation direction.
If the motor has an axial style cooling fan, then the measures suggested above may be worth considering.
Edited By David Jupp on 28/03/2013 08:26:01
|Stub Mandrel||28/03/2013 09:29:23|
4311 forum posts
The fans are a steel disc cut to create about eight vanes which are twisted at 45 degrees. they aren't very effective. The mills are not reversible, so a single fsn in the right direction will be enough.
|ANDREW PARKER||28/03/2013 10:30:06|
|4 forum posts|
Hi chaps, thankyou for all of the advice. Having read your suggestions I suspect it is probably either the start capacitor, centrifugal switch or the fan unit not providing enough cooling. The motor is a single phase AC induction motor 550W, 240V, 3.6A, 1400rpm, 50Hz E. The milling machine is the Chester Champion model and is probably about 10 years old. It has a reverse switch which I rarely use. I have decided to have the motor looked at by a local motor rewinding company to see if it is cost effective to have it repairied. The fan modification also looks like a good solution although I think my motor is larger than the one in the thread so I may have to come up with a diferent method of fixing the new fan to the motor. I would still be interested to know if anyone has managed to replace the motor with a different one. I tried looking on Ebay as suggested but was not really confident in been able to pick the correct type of motor. Once again thanks for your help.
|John Coates||28/03/2013 12:25:31|
558 forum posts
Mine is a Chester Champion from the 90's with the round column, tilting head and reverse switch with a 1/2 HP motor like this one - is yours the same?
I converted mine to 3-phase and have been very happy. When I get home after work I will check to see if I have the original single phase motor as I am pretty sure I put it away in a box.
My first 3-phase conversion used the original cone pulley but I cross threaded the 5mm allen bolt in the end under power and buggered it up. So my next conversion used the keyway slot to secure a single pulley and discarded the cone pulley.
Edited By John Coates on 28/03/2013 12:31:12
|ANDREW PARKER||28/03/2013 12:57:08|
|4 forum posts|
Hi John, yours looks very similar to mine other than the colour. Mine is white, the switch looks identical. If my motor proves costly to repair, assuming it is repairable, would you consider selling your original motor. If so let me know how much you would want for it including the cost of postage.
|Stub Mandrel||28/03/2013 13:04:18|
4311 forum posts
I've confused the Conquest with the Champion, I think.
|John Coates||28/03/2013 19:19:02|
558 forum posts
Andrew: mine is a white one as well. I didn't have a photo so used one I saved from an ebay ad to see if yours was the 90's version
Happy to sell mine once I find and check it works
|65 forum posts|
I've had a Champion like yours for more than 15 years and despite being worked quite hard I've had no motor problems (touch wood).
Here's a thought. Every one is making suggestions around cooling and electrical issues but this might be worth a look.
I recently bought an early 80's Myford lathe which had had little use and when I started using it the motor began to overheat and trip the overload cut-out in the starter. I thought I was looking at £200 for a new motor as it was tripping even when idling. I checked the machine over just to make sure everything was free and discovered the motor back bearing was the problem, so I gave a bit more attention to the oiling of the motor and the problem has gone. Now you have burned out two motors so it might be you have a problem with the spindle bearings on the mill. Mine has quite poor oil seals and the oil has a tendancy to run straight through the bottom bearing. It might just be a shortage of oil that's overloading the motor if you are not oiling frequently.
Hope it's something as simple as that.
Edited By 61962 on 28/03/2013 22:35:16
|Ian S C||29/03/2013 10:54:22|
7468 forum posts
Further to Eddie's suggestion of oiling problems, I noticed trouble last winter of the lathe being sluggish, and not starting well in high gear, once the bearings warmed up it was OK, perhaps I should change to a lighter grade of oil in the winter. My lathe has a 1 1/2hp motor, maybe they are only ponys, definitly not shires.
One problem I had in the early days was the lathe siezing once when I was using backgear, the pullies siezed on the shaft. It wasn't till after I had stripped the shaft that I found out how the oiling system works, I'v had no trouble now for over 20 years, but it sure made the belt slip. Ian S C
|Nicholas Farr||29/03/2013 11:41:22|
2405 forum posts
Hi Andrew, the white ones have the same spec as the green one shown in john's photo. The scan below is from thier 2003 catalogue.
Like Eddie I've had one for 15 years and it still has the oridginal motor on it. Below is a photo of the motor spec plate on mine.
Are you sure you are not putting too much tension on the drive belt adjusutment, it should not be drum tight, you should be able to flex it a little with finger pressure between the pulleys. A tight belt can make the motor work harder and over heat as well as putting undue pressure on the bearings.
Edited By Nicholas Farr on 29/03/2013 12:16:04
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