Boxford AUD motor drive wheel plus reverse switch issue

Hi everyone

I own an AUD and I have a couple of issues.

1) the key is slipping out of the keyway of the spindle on the rhs of the motor. I only noticed recently when the drive belt wheel was grinding against the wall of the motor compartment! The belt had twisted too so I'm glad I caught it early. This all happened when the key presumably slipped. I managed to get it all back into place with gentle use of a crow bar and I tightened up the grub screw in the spindle.

Sadly the key has slipped out again.

My first question is then, do I have to remove the motor to gain proper access to sort this out? There is virtually no room to work on this in situ.

2) a few weeks ago I was practicing thread cutting. I was starting and stopping the motor quite a bit, in retrospect maybe a bit too frequently. As a result the reverse switch began failing to engage.

If I hold the green start button in, I get a very noisy stuttering as the safety electrics keep shutting it off, like I'm pressing the stop button at the sage time.

So I opened the panel and analysed how things work. I can manually switch the reverse on by pressing the black button on the main junction box. The emergency stop doesn't engage. This makes me wonder if there is something wrong with the reverse switch controlled from the front panel. I am on single phase and the reverse switch had been working since I bought the lathe last year.

My second question is then, does anyone have experience of this happening? And if so can you advise.

Many thanks in advance!!

I'm contemplating getting an inverter as this would make quite a few things better and bypass the current setup.

Regards

Fergus

Taking the motor out may be the best way to solve the key issue.

There are variations in the switch gear and a picture of just what you have may be useful.

As for an inverter not sure that would be worth the expense as you'd need to change the motor as well.

My AUD has been faultless for a number of years and it has done a fair bit of work.

It sounds as if the latching contactor in the start switch could be failing. Does the same thing happen in forward ? or perhaps -

My AUD is an ex-schools model with safety cutout switches on the motor cabinet, the gear casing and back gear selector knob. If any of these are not adjusted correctly, the self latching start contactor would drop out.

I don't think you mean inverter. This is something that changes DC to AC I suspect you mean a variable frequency drive (VFD) for 3 phase motors or a rotary converter for changing single phase supplies to 3 phase to drive a 3 phase motor.

Motors often have specifications such as duty as well as current, power and rpm. The duty may be something like 20 minutes per hour or continuous. Another may be maximum number of starts per hour. The later is important for single phase motors that have a start circuit as well as the run circuit. The start circuit only kicks in when power is first applied and pushes the motor in the correct direction until the motor is up to speed when it is disconnected. This becomes an issue when you are stopping and restarting the motor frequently on a motor with limited starts per hour.

The limitation is due to excess heat build up in the motor needing time to dissipate. There is a possibility that you have overheated the motor and this has had knock on effects in the rest of the system.

The next possibility is that frequent reversals has resulted in the contactors shaking something loose.

Another possibility is that you are using a reversing switch that should only be operated when not powered up. Some reversing switches need the power off before they are operated otherwise the contacts arc and either weld together or fail to make contact due to oxide build up on the surface.

I can't help you with the drive key as I have no experience of this specific lathe.

Martin C

Thanks for your comments everyone.

Martin, I'll systematically go through those suggestions and see what I find.

Speedy, the forward switching was a tiny bit glitchy when this whole thing started but after the first time, forward has been perfect. Reverse works once every 10 times but it feels like I'm damaging something so I've stopped trying.

Bob, it looks like a royal ball ache to remove the motor but I will do it if it's the last resort. I've loosemed the grub screw and eased the key back along the keyway and retightened the grub screw on the wheel. In a pitiful attempt at stopping the key moving again I've put a plastic cable tie on the end of the spindle. You never know a tiny bit of resistance might just stop it edging out.

I didn't realise I could send photos so I'll send a few in the next hour.

Thanks again all.

The picture posted at 20:14:05 shows the drive belt . It seems in good condition although the outside looks very rough.

The control wiring picture shows the button I press that allows the reverse to engage. I just did this to show the reverse actually works but not by the normal method of pressing the green start button on the front panel. This is entirely for demonstration as it's totally impractical to open the panel every time I need to engage reverse. I took a video but I don't think I can pay this here .

Hi Fergus, Guys,

Are you sure there is not a second grub screw under that one ?

Doubling securing screws is very common.

Just as a matter of interest, how or why is the key moving ?

Is it the wrong size ? Why is the screw not clamping it in place ?

Also check for a second grub screw positioned at 90 degrees to the one you can see.

Martin C

Hi

John, that's interesting I'll check it out tomorrow.

Larry, I've no idea. I find it a trial sometimes getting a gear back of I'm changing gears, with the key being a very tight fit. How this one is slipping is a curiosity! There's a possibility this motor has never been removed so I imagine the key is original and I can't see why it would be the wrong size. The grub screw is about 20° anticlockwise from the key so it only there to secure the wheel. I just can't figure out then why the key is moving. Clearly through vibration but normally the are such a bugger to get in I'm surprised it's moving.

This might be useful link

Will do Martin but I'm sure there's just the one. I've photographed it from a few angles now and don't remember spotting any.

Bob, that's really great thanks. I'll definitely do this now I've seen the process. I like the idea of a strip down and refurb of the bearings and belts. I wish I could be certain of the bearing sizes so I could order them and do it all in a day without waiting for deliveries, especially at the present moment. I might just remove it and do a quick check of the sizes and put it back until the parts arrive.

Cheers everyone.

It is not very expensive to adjust an AUD to this century.

It became a rather potent lathe

Facing

Edited By Niels Abildgaard on 31/05/2020 05:35:50

Check Your pulley keyway and the key for wear , both need to be a good fit , Does you belt show any signs of wear also check the motor bearing for any movement , Have had this problem many times with motors and belt drives. If the motor shaft has any wear then this needs to be rebuilt and then turned down to the correct size and a new keyway cut , the pulley can be rebored and sleeved and a new keyway fitted , Continued use can result in your motor shaft breaking off at the point where this comes out of your motor , A difficult and then complicated repair to due , complete shaft can be replaced .Further investigation required to avoid a possible difficult repair..

Good luck

Brian Morehen

Yes I agree now I think about it more. Today is going to be a messy day. Thanks for the good luck!

I'll post back later when I investigate more.

Fergus