Viceroy 280 Syncro Back Gear shift problems

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steamgeek
Posts: 18
Joined: Sun 03 Jan , 2016 17:19 pm
Hardware/Software: Denford Viceroy 280 synchro

Viceroy 280 Syncro Back Gear shift problems

Post by steamgeek » Sat 18 Apr , 2020 10:29 am

Hi

I am having an intermittent problem with the gear shifter on the headstock. The shifter seems to tighten up as if something is heating up causing the mechanism to bind up.

I have checked the oil level in the headstock and it is Ok ( I am using ISO 32 hydraulic oil ) , I have taken the top of the headstock and had a look inside for any thing obvious, but nothing is jumping out at me. I have checked the temperatures around the headstock and nothing is running excessively hot, although I have had instances of the problem occuring when the lathe has been running for a couple of hours, but I have also encountered the problem after relatively short run of less than 10 minutes.

Machine is a 2008 model

Anyone encountered a similar problem or any clues what it may be?

Thanks in Advance

rpwilson
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Joined: Tue 03 Jun , 2014 15:20 pm
Hardware/Software: None. I own a pre CNC Denford 280 Synchro lathe.

Re: Viceroy 280 Syncro Back Gear shift problems

Post by rpwilson » Sat 18 Apr , 2020 11:17 am

At one time there was a problem with the plastic gears expanding as they warmed up and caused binding, but this was resolved a very long time ago, by machining the gears with increased clearance. This should not apply to yours, being such a late machine. Incidently, I didn't know that Denford were still making Synchros as late as 2008.

steamgeek
Posts: 18
Joined: Sun 03 Jan , 2016 17:19 pm
Hardware/Software: Denford Viceroy 280 synchro

Re: Viceroy 280 Syncro Back Gear shift problems

Post by steamgeek » Sat 18 Apr , 2020 15:21 pm

The date came off the manufacturers plate on the machine

I will strip the gears out and have a look on the sides see if there are any score marks

Thanks for the info

steamgeek
Posts: 18
Joined: Sun 03 Jan , 2016 17:19 pm
Hardware/Software: Denford Viceroy 280 synchro

Re: Viceroy 280 Syncro Back Gear shift problems

Post by steamgeek » Fri 22 May , 2020 14:14 pm

I think I may have figured out the problem with the stiff back gear shift

The problem is with the large plastic back gear on the layshaft, when I rotate the head stock shaft by hand the head stock gear and the layshaft gear bind up every second revolution of the headstock shaft, once you turn the headstock a quarter of a turn the problem clears and the back gear shift moves freely. I cannot feel and movement in the gears and visual inspection of the gear teeth does not reveal any issues.

My assumption at this stage is the gear is off centre on the shaft and causing the bind. It is possible the layshaft could be bent, but I would have thought I would see some strange wear patterns on the gear teeth if that was the case

I think my next plan of attack is get and indicator on the gear and measure any run out on the gear

Feel free to chip in any thoughts or ideas to help me move this along

Pete.
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Re: Viceroy 280 Syncro Back Gear shift problems

Post by Pete. » Sat 23 May , 2020 12:32 pm

This is a common complaint. The original nylon gears swell over time. Mine was ok when cold but would start to bind at high speed as it warmed up then of course once the gear started expanding it would bind more and quickly get noisy. Once it got hot you couldn't move the Low/High lever without considerable force. I made a new gear in the end from Delrin.

You'll know if this has happened if/when you remove the gear as all the holes will be out of shape.

steamgeek
Posts: 18
Joined: Sun 03 Jan , 2016 17:19 pm
Hardware/Software: Denford Viceroy 280 synchro

Re: Viceroy 280 Syncro Back Gear shift problems

Post by steamgeek » Sat 23 May , 2020 16:33 pm

Thanks for the info Pete

I managed to get a dial gauge down into the headstock and there looks to be about 0.4mm of ovality at the crown of the teeth

Looks like I will be digging through the drawings archive to find the specs for the gear

You said you used delrin to remake the gear, I wonder if cast iron would be a better bet ?

Either way I had not bargained on stripping down the headstock - bummer

Regards

David

Pete.
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Re: Viceroy 280 Syncro Back Gear shift problems

Post by Pete. » Sat 23 May , 2020 16:44 pm

Cast iron won't work here, it's a plastic gear meshing with a steel one, and it mounts on a steel hub. Plastic to keep noise down and so it doesn't affect the finish by transmitting vibrations down the spindle I suppose.

rpwilson
CNC Expert
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Posts: 156
Joined: Tue 03 Jun , 2014 15:20 pm
Hardware/Software: None. I own a pre CNC Denford 280 Synchro lathe.

Re: Viceroy 280 Syncro Back Gear shift problems

Post by rpwilson » Sun 24 May , 2020 0:04 am

You could try getting the gear OD skimmed to remove the ovality, and hope that the clearance on the bottom of the teeth is sufficient. Or mark the high teeth and take 10 thou off with a fine file. Crude? Possibly, but it can't be worse than what you have now can it? Its not as if you are altering the flank profile of the gear, you'd just be restoring the clearance that was there originally. Denfords solution, when this arose originally, was to reduce the OD of the gear by 10thou (if I recall correctly) and cut the teeth a bit deeper.

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