Boxford AUD motor drive wheel plus reverse switch issue

[Fergus DavidsonParticipant @fergusdavidson50660]

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

[Fergus DavidsonParticipant @fergusdavidson50660]

Drive wheel keyway slipping.. And.. Reverse switch malfunction

[Bob Brown 1Participant @bobbrown1]

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.

[Speedy Builder5Participant @speedybuilder5]

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.

[Martin ConnellyParticipant @martinconnelly55370]

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

[Fergus DavidsonParticipant @fergusdavidson50660]

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.

[Fergus DavidsonParticipant @fergusdavidson50660]

[Fergus DavidsonParticipant @fergusdavidson50660]

[Fergus DavidsonParticipant @fergusdavidson50660]

[Fergus DavidsonParticipant @fergusdavidson50660]

[Fergus DavidsonParticipant @fergusdavidson50660]

[Fergus DavidsonParticipant @fergusdavidson50660]

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 .

[John BaronParticipant @johnbaron31275]

Hi Fergus, Guys,

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

Doubling securing screws is very common.

[larry phelan 1Participant @larryphelan1]

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 ?

[Martin ConnellyParticipant @martinconnelly55370]

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

Martin C

[Fergus DavidsonParticipant @fergusdavidson50660]

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.

[Bob Brown 1Participant @bobbrown1]

This might be useful link

[Fergus DavidsonParticipant @fergusdavidson50660]

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.

[Niels AbildgaardParticipant @nielsabildgaard33719]

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

Upgrading Boxford

It became a rather potent lathe

Facing

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

[Brian MorehenParticipant @brianmorehen85290]

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

[Fergus DavidsonParticipant @fergusdavidson50660]

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

[SillyOldDufferModerator @sillyoldduffer]

Is it worth asking a different question? Rather than assuming the belt twists and wears because the pulley wanders due to a loose key, ask why the belt is moving the pulley at all?

The displacement implies a sideways force on the pulley. Although sideways movement might be worsened by a damaged belt – change it – another question is what damaged the belt in the first place? Misalignment is a possibility. Have a good look at the two shafts: they need to be parallel, and then the pulleys need to be aligned vertically on them.

As motor mounts are usually adjustable maybe the motor isn't parallel with the lathe? May have shifted over time or been left wonky after maintenance. Less likely that the driven shaft is wrong but worn bearings that side could also cause the problem, especially if they've been stressed by a misaligned belt for years.

Whatever the reason, a misaligned pulley will lever against one side of the belt, causing wear while tending to slide the pulley sideways. Worth checking motor alignment and, with the belt off, any sign of play in the motor shaft and/or the bearings on the lathe's driven shaft.

Dave

[Simon Williams 3Participant @simonwilliams3]

Posted by Fergus Davidson on 30/05/2020 21:41:09:

The grub screw is about 20° anticlockwise from the key…

That's mighty fishy!

If, as I understand it, it is a plain key I would sensibly expect that the grub screw would bear on the top of the key, which says to me that the pulley bore has slipped and is somewhat chewed. Trying to tighten the grubscrew to compensate means that the screw is trying to take the drive torque, as the key isn't helping. That in turn chews the motor shaft.

'Fraid you're going to have to dismantle enough at least to get the pulley off the motor and see what the problem is.

As others have said beware of the second grubscrew in the same hole below the first, also another screw (or screws) at 90 deg to the obvious one.

Good luck, and do keep is posted

HTH Simon

[Fergus DavidsonParticipant @fergusdavidson50660]

Another question. I'm going to order bearings for all spindles including the motor. How much should I be spending with their prices ranging from £3 to £80.

Should I be mindful of the rpm and sealed units? The current ones on the motor spindle are deep groove and unsealed.

I've cleaned everything up and have the new v belts, so just the bearings to go.

I drilled a hole for a 5mm grub screw to hold the key in position so even with the new bearings and also lining the pulley up exactly with the one above, there is no chance of the key slipping again. The pulley grub screw is the only one and at 90° round from the keyslot but the flat it should locate onto was about 97° from the keyslot so that's one reason the pulley was slipping. I ground a small concave round into the spindle for the pulley grub screw to settle in so that also will now not move.

Photos to follow

[Fergus DavidsonParticipant @fergusdavidson50660]

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