VR: Heat Affecting Dashpot?

[PMST]

A few days ago I ran into a problem that I've never had before. I live in Bulgaria and summers get very hot. Last summer I was away a lot more and doing less cutting, whereas this year obviously I haven't been away with everything that's happening and got cutting work booked in every day, this obviously puts a lot more strain on my VR.

Two days ago, I was cutting all morning into the afternoon, about 2pm (about 34 degrees Celsius outside) I started getting skips at the start of my records, mainly in the lead in groove, but no where else. I fully recalibrated, checked weights, alignments, got everything just right, still the same problem, so I shut it down for the day.

Yesterday I go in, check weights, all still perfect, start to cut, no problems whatsoever. Then again in the afternoon the same happened and it started skipping.

This morning is start to cut, all is working perfectly again. So I assume this is the heat affecting the dashpot, as the skips imply the head is bouncing when initially lowered. Anyone else had this? The machine is metal, so of Cours ether heat affects if, but just wondered if anyone had come across anything like this or had any advice?

Im using Myshank stylus and blanks, 13g weight, measured with digital scales.

[PMST]

Also I should add, I'm cutting on a SP-10 and have no platter wobble issues at all

[SueDenim]

Yes, I have similar issues to you but I don't think it's ambient heat levels that are causing mine as I'm in the UK so quite mild or just plain cold!

I encounter the variable groove depth problem when I initially set the head down (lead in) and they continue through the first minute or so of the cut, lessening as the head progresses across the blank. This can occur on all diameters of blank at any position (not just the outer diameter).
My VR is fairly old now and I've assumed that my dashpot's spring is providing inconsistent levels of force until it has been in operation for a while.

The only solution I have found is to either perform test cuts at the beginning of each session, or else run the feedscrew with the head down from the start (i.e. the normal resting position) until just before it would make contact with the platter (I wouldn't want to damage my stylus!).
If I do the later method a couple of times at the start of the session, then I have either no depth issues or they are manageable for the first couple of cuts.

I could really use someone who knows more than I to service my VR - any takers?! hehe

[PMST]

Yeah at the moment I do a test cut at start of each day, im finding the head weight is needing adjusting each day too, how often are you having to adjust head weight?

[SueDenim]

Not that much to be honest, but I only check the weight once I've completed my 'warm up' tests so it's probably stabilised by that point.

[Discomo]

Perhaps it’s a build up of dust / dirt at the long screw which makes it can’t move freely? Or perhaps, but maybe less likely, the spring has lost it’s tension?
I’d think of such things since the device is fully mechanical. I’m planning myself an acryl /plexi cover to prevent dust from entering everywhere.

[Discomo]

Or maybe the iron piece between cuttinghead and horizontal bar isn't moving fluently anymore. Maybe disconnect it and add the appropriate oil to the screws which makes it tilt?

[PMST]

That's a good shout, i haven't cleaned the lead screw for about 6 months! Maybe oil and cleaning... Although the problem hasn't come back since cutting earlier in the day and less into the mid day heat, so fingers crossed i can work around it, but for sure will check all those bits, keep it all lubed!

[PMST]

So, after some tests, I think I can conclude that heat and humidity are 100% effecting the VR.

Yesterday was a cooler day in terms of temperature, I calibrated the machine, 45g weight with no tension, 13g final head weight. Cut until about 1pm and all was fine.
Today I started cutting late, at about 9am, usually I start earlier and due to the heat, I try to finish by mid day. Today it is nearly 1pm and I have been cutting for a few hours, and the skipping issue came back. Today is also considerably hotter outside and much wetter.

I recalibrated the machine and the head weight with no tension was now 38grams, whereas yesterday morning when I calibrated it was 45grams. So I have just got all weights back to normal and its cutting fine.

So, it seems that every 2 days, and mainly on very hot days, the lathe goes out of whack considerably, which I suppose makes sense, as it is metal, which is effected by both heat and humidity!

The weight is changing an awful lot, I've checked all parts of the lathe, nuts, bolts, lead screw etc, all is tight and working very well, its is just on hot days, later in the day something happens, maybe spring tightens or loosens or something, but the head weight is changing drastically. I have found recalibrating gets it all working perfectly, so not a huge issue, just something to think about if you live in hotter/wetter climates.

[PMST]

Unless I am still missing something, which is possible, but I have tried many things, and this is what it seems like, something on hot/humid days is changing the head weight, something that doesn't happen on cooler days.

[Discomo]

Interesting. Maybe the viscosity of the oil changes with higher temperature and a different oil works better? Just guessing here.

[MEGAMIKE]

hi i dont want to have a debate on how hot places get but i ve have my VR mostly in my back shed and in Australia it gets 46/8c easy and in a week straight too and my shed has got to 51c before as i looked on my heat gun many times...my point is that this issue has not happend to me well it has but nothing to do with heat.. i do clean and lube the VR many times a year though..

[PMST]

Hmm ok yes that's definitely hotter than here! I'll keep doing tests..... Some how the head is getting lighter without the black knob and back weight moving (i marked both).

I wonder if the humidity plays a part? Its soaking wet here in terms of humidity, will look into it. If anyone has any ideas on what else it could be that would be great

[Discomo]

hi i dont want to have a debate on how hot places get but i ve have my VR mostly in my back shed and in Australia it gets 46/8c easy and in a week straight too and my shed has got to 51c before as i looked on my heat gun many times...

How can you even survive this kind of heat? Once I experienced 40 in South of Germany. Part of me already died that day.

[MEGAMIKE]

ahh ok humidity is differant here only dry heat so wet and hot is no good for dashpot ..but i suggest you clean up inside to remove hair /old grease etc and lube the whole area ,arm/dash etc..
40c in germany WOW you guys must have cooked..... the only good thing cutting in that heat is no heating stylus and light,oh and i can cook an egg in the sun too. .when i was youth worker in 90s in the middle of australia it was 52c and i was teaching kids how to breakdance

[MEGAMIKE]

know your machine ,pull it apart and back together again "blindfolded" like in the army hahah.
understand what every part does and where it fits..
example the arm:: pull it out clean the hole lube it up again etcetc..
that way you can pin point the problem everytime..

biglove

[PMST]

Will do, also something i have noticed is the oil in the dashpot used to be a translucent yellow, now a much darker almost organge shade, i'll look into replacing that too

[tragwag]

not to complain about the heat and humidity but I'm in FL USA where it's routinely 80+F indoors in the studio, haven't seen any effects like you describe.
when you look at the disc during the outside edge, do you see the head lifting up?
your weight might be a little too low, or the blank is slightly warped, or your dashpot spring is out of spec
all those things have caused similar issues for me

[PMST]

It seems like it might be the dashpot oil..... I have stripped the dashpot and cleaned it and put new oil and so far cuts are good. I spoke to Souri and he said it won't be the dashpot oil and not to change it, however after speaking to people here it seems like it is! When I was told it wasn't the oil, I assumed elsewhere, seems it was as simple as that, I hope! Thanks for the help

[PMST]

Im assuming as the oil was old, as it got hotter the viscosity changed later in the day, as its only an issue when it get's hotter... but changing the oil so far has rectified it, so maybe just a case of old used oil, getting thinner with heat perhaps? The problem was the head lifting slightly out the grooves on the lead ins, but nowhere else, also weight was up to 14g with my shank stylus and blanks. Fingers crossed this has sorted it, will be cutting all day so will see how it goes later on