VR: Heat Affecting Dashpot?

[tragwag]

not sure about everyone, but on one of my lathes I can drop the head with 15g weight and it's smooth and even every time.
on the other one, the spring is just different and needs slightly more weight, 18-20g to sit down smoothly for the head drop.
see if that helps

[Discomo]

i'm gonig to try some SAE 50 oil, or maybe 40

That's a good point - maybe we can do a quick straw poll...
What weight of oil is everyone using in their VR dashpot?

Maybe a seperate poll opening for this? Interesting information.
I myself have no clue. I still have the same stuff in it which souri poured into it 3 years ago . I hafe a syringe with stuff which I suppose isn't heroin, but it doesn't carry info

[PMST]

Tomorrow i collect my SAE 50, i tried some SAE 30 and it was a little thinner than what came with the syringe, i've had help from a friend on here, seems like its about SAE 40 that comes with it, but in the heat it just wasn't dampening enough, so i hope SAE 50 will help! tomorrow evening i'll do test cuts and report back.

A poll would be great, separate thread, little bits of info like this are massively helpful.

[PMST]

not sure about everyone, but on one of my lathes I can drop the head with 15g weight and it's smooth and even every time.
on the other one, the spring is just different and needs slightly more weight, 18-20g to sit down smoothly for the head drop.
see if that helps

That really goes to show how different each machine can be! Very helpful info, the spring can likely get overlooked as being different lathe to lathe

[SueDenim]

Great info - thanks everyone!

[markrob]

Hi,

Just for my own curiosity:

Is the dashpot only used to allow for a smooth head drop? In that case is there no other mechanical damping to the head suspension when cutting? If that's the case, then the cut depth issues would have to be caused elsewhere.

Mark

[DJ2000]

Hi,

Just for my own curiosity:

Is the dashpot only used to allow for a smooth head drop? In that case is there no other mechanical damping to the head suspension when cutting? If that's the case, then the cut depth issues would have to be caused elsewhere.

Mark

the dashpot also active in cutting the plunger in the oil should dampen out movment along with the spring, not sure what the thickness oil in mine but have been using carburettor damper oil in the dashpot

[PMST]

Hi,

Just for my own curiosity:

Is the dashpot only used to allow for a smooth head drop? In that case is there no other mechanical damping to the head suspension when cutting? If that's the case, then the cut depth issues would have to be caused elsewhere.

Mark

The dashpot is for push/pull dampening whilst cutting, so crucially important to get the right oil

[PMST]

Hi,

Just for my own curiosity:

Is the dashpot only used to allow for a smooth head drop? In that case is there no other mechanical damping to the head suspension when cutting? If that's the case, then the cut depth issues would have to be caused elsewhere.

Mark

the dashpot also active in cutting the plunger in the oil should dampen out movment along with the spring, not sure what the thickness oil in mine but have been using carburettor damper oil in the dashpot

Can you send a link to the oil you use? I have Motul SAE 50 mono grade oil arriving, delayed now until tomorrow! But will test it and will make a thread about how it works, then maybe you could add your oil and thoughts in, be good to make a resource for this info.

[Discomo]

Hi,

Just for my own curiosity:

Is the dashpot only used to allow for a smooth head drop? In that case is there no other mechanical damping to the head suspension when cutting? If that's the case, then the cut depth issues would have to be caused elsewhere.

Mark

The dashpot is not for a smooth headdrop, because it will drop hard and crush the tip of the stylus if the head slips from your fingers. It would be great if there's a way to mod this in the VR.
Do you think it's possible/easy to add another dashpot for a smooth head drop?

There is no other mechanical damping whilst cutting...

I agree with you it must be either in the spring or in the moving big block.

[DJ2000]

Hi,

Just for my own curiosity:

Is the dashpot only used to allow for a smooth head drop? In that case is there no other mechanical damping to the head suspension when cutting? If that's the case, then the cut depth issues would have to be caused elsewhere.

Mark

the dashpot also active in cutting the plunger in the oil should dampen out movment along with the spring, not sure what the thickness oil in mine but have been using carburettor damper oil in the dashpot

Can you send a link to the oil you use? I have Motul SAE 50 mono grade oil arriving, delayed now until tomorrow! But will test it and will make a thread about how it works, then maybe you could add your oil and thoughts in, be good to make a resource for this info.

not got a link as cant remember where bought it from was a few years ago! ill grab a photo of the bottle tomorrow as cant remember what it was called myself.

also anyone thought about changing the oil dashpot to an air one for a test? I do remember a stirling engine being made from an air dashpot and the dashpot movement was really smooth

https://www.airpot.com/product-category/product-lines/dashpots-shock-absorbers/airpot-precision-dashpots/ a link for ref

[PMST]

I've actually emailed Airpot, talking to them at the moment! Will get full info and let you know.

Initial reply is

"It sounds like our dashpot would work well in your application as the damping is only minorly affected by temperature. We have 6 bore sizes, for handling different damping forces. They are available in 2-way and have adjustment for the damping coefficient."

I am sending them info on my VR and measurements, will report back soon!

[trailerparkjesus]

I had to get some new oil from Souri, tried a lot of different substitutes. Steven said he knows the recipe, but not sure if he's making it anymore. Wrong dashpot oil can cause lift outs for sure.

Honestly, most of these issues are from sticking parts. I like to drop the head up and down off the platter repetitively to loosen up the points every so often. A good wiggle and oil goes a long ways. Sometimes I feel it is from how the diamond is made/angle of diamond upon set up, when I change a trouble stylus these issues sometimes go away. I know you know about level platter front to back side to side so thats not the issue.

[trailerparkjesus]

Do you have a dehumidifier?

[Soulbear]

Hi Trolls,
Forgive me for “Chipping In” here, and please understand I am not Criticising anyone by any means!! I am not, nor after now waiting for over 4 years for a response from Herr “S” am I ever likely to be, a VR Owner. But this has not stopped me following this thread with Great Interest, sometimes with Amusement, and sometimes with Bafflement!!. It seems to me that VR Owners are “Quite Reluctant” to Change Very Much about the Design of their VR Lathes in case they somehow “Break” what they perceive to be “the Magic Spell” that makes the VR what it is. This behaviour strikes me as somewhat “Odd in the Extreme” and this makes me curious.
Not all designs are “Perfect” from the “Get GO” and they are of their Own Time, and could maybe stand to be sympathetically modernised and improved upon over time??

Take this for a simple example

“Writing!!” :-

At first Rocks and Stones were used to scrape marks on trees and cave walls, This progressed to dipping the Pointed Tips of Feathers of some Dead Bird into some blood, and scratching marks on animal skins, then along comes the Egyptians with Papyrus, and the Chinese with paper, then we discovered inks, and metalworking for pen nibs, moved onto desks, with pencils, inkwells, fountain pens, biro’s, felt tips, word processors, computers, the works etc etc. All progression over time?? In this modern world this “Speed of Development” has increased exponentially, not in all areas, but many nonetheless. What formerly took many years to design on a Drawing Board, then to develop Prototypes, then Gear Up for Mass Production, can now be done at home on a PC with a Plastic or Metal Printer by a reasonably Savvy Child, in a FEW HOURS!! I read somewhere that if the Automobile Industry had kept pace with the Electronics/Computer Industry, we would now be able to make a Car Journey the equivalent of to the Moon and Back to Earth, on one Tank of Gas!!


If a design has Obvious Drawbacks or Flaws, then WHY NOT CHANGE IT??
Whilst I can appreciate that there may be very many various “Factors” at Play” as to why this may be so, thereby Validating a VR owners decision not change things because of “Time Constraints, Fear of Destroying the Value of the VR, Fear of Potentially Damaging the VR, Loss of Income/Livelihood” etc etc….! I do not think it conceivable, that this applies in each and every VR Owners case. The VR has been around since 2009-ish, so at a conservative 1 or 2 sales a month, that would mean that would maybe mean there are maybe a couple of hundred VR’s now in use Worldwide??? I have also heard muted the possibility of going the “Air Pot/Damper” Route, this also strikes me as being “Worth a Shot” I know at least one of my Lathtroll Buddies is modifying his VR to “Airpot Damping” as I write, and I will encourage him to Post the results of his endeavours here on the Forum , but out of the many Lathetrolls who own the VR, why not others??? Gravity can sometimes be a bit of a nuisance. Oil is Messy!! Oil (Usually) Flows Downhill, therefore the “VR Dashpot” also therefore needs to be as Close to Vertical as Practicable. Do other Lathetrolls not share my view that this is a “Design Limitation” restricting Optimum Positioning on the VR??? One that would not exist if the “Airpot Alternative” was used instead???
Examples of Modifications Demonstrating such changes are possible :-

Airpot on Hara M180 Lathe.jpg

Airpot on BSR DR33C Lathe.jpg

Airpot on Presto-Sugden Adaptor-1.jpg

Various Trolls wrote :-

“the head seems suspended well in the new oil”

”I didn't have Souri's dashpot oil.... so i'm gonig to try some SAE 50 oil, or maybe 40, off advice from a friend”[/quote
[]

“That's a good point - maybe we can do a quick straw poll... What weight of oil is everyone using in their VR dashpot?”

[/]

“the dashpot also active in cutting the plunger in the oil should dampen out movment along with the spring, not sure what the thickness oil in mine but have been using carburettor damper oil in the dashpot”

In my own view, the most Most Thoughtful and Practical inputs were made by Markrob and trailerparkjesus, when they suggested:-

“Honestly, most of these issues are from sticking parts”

“Have you checked to see if the dashpot is damping the head movement properly? If you float the head and give it a slight tap, does it oscillate a few times before settling down? That would indicate that it’s under damped and may need a higher viscosity oil. If it’s over damped, is it sluggish settling down? That would indicate the opposite issue. It would also be interesting to try the experiment dead cold and then after heating the dashpot and other areas with a hair dryer to see if the behaviour changes Another thing to look at is if the undamped motion of the head (no dashpot oil present) is being hindered by bad suspension bearings or some other friction due to rubbing. Friction/ sticktion can act as a damper, but unless it’s controlled, the results could be variable especially with temperature”

My point is this, Why to bother your heads with unnecessary formulae, Temperature Coefficients,, or worry about finding the correct “Weight/Viscosity” of Oil??
Simply Modify the VR And at a Cost of $1 per 1000 Spring/Units, Choose maybe a few "Different Springs" to Try Out, Fit an “Airpot” and Adjust 1 Screw to tune the System!!! And Let us know the results
Regards Soulbear

[PMST]

Do you have a dehumidifier?

I don't have any air con or de-humidifier, its extremely humid here too, i try to avoid de-humidifying due to stack issues. Lathe is getting re-assembled this morning, fully lubricated and thick oil!

[PMST]

Hi Trolls,
Forgive me for “Chipping In” here, and please understand I am not Criticising anyone by any means!! I am not, nor after now waiting for over 4 years for a response from Herr “S” am I ever likely to be, a VR Owner. But this has not stopped me following this thread with Great Interest, sometimes with Amusement, and sometimes with Bafflement!!. It seems to me that VR Owners are “Quite Reluctant” to Change Very Much about the Design of their VR Lathes in case they somehow “Break” what they perceive to be “the Magic Spell” that makes the VR what it is. This behaviour strikes me as somewhat “Odd in the Extreme” and this makes me curious.
Not all designs are “Perfect” from the “Get GO” and they are of their Own Time, and could maybe stand to be sympathetically modernised and improved upon over time??

Take this for a simple example

“Writing!!” :-

At first Rocks and Stones were used to scrape marks on trees and cave walls, This progressed to dipping the Pointed Tips of Feathers of some Dead Bird into some blood, and scratching marks on animal skins, then along comes the Egyptians with Papyrus, and the Chinese with paper, then we discovered inks, and metalworking for pen nibs, moved onto desks, with pencils, inkwells, fountain pens, biro’s, felt tips, word processors, computers, the works etc etc. All progression over time?? In this modern world this “Speed of Development” has increased exponentially, not in all areas, but many nonetheless. What formerly took many years to design on a Drawing Board, then to develop Prototypes, then Gear Up for Mass Production, can now be done at home on a PC with a Plastic or Metal Printer by a reasonably Savvy Child, in a FEW HOURS!! I read somewhere that if the Automobile Industry had kept pace with the Electronics/Computer Industry, we would now be able to make a Car Journey the equivalent of to the Moon and Back to Earth, on one Tank of Gas!!


If a design has Obvious Drawbacks or Flaws, then WHY NOT CHANGE IT??
Whilst I can appreciate that there may be very many various “Factors” at Play” as to why this may be so, thereby Validating a VR owners decision not change things because of “Time Constraints, Fear of Destroying the Value of the VR, Fear of Potentially Damaging the VR, Loss of Income/Livelihood” etc etc….! I do not think it conceivable, that this applies in each and every VR Owners case. The VR has been around since 2009-ish, so at a conservative 1 or 2 sales a month, that would mean that would maybe mean there are maybe a couple of hundred VR’s now in use Worldwide??? I have also heard muted the possibility of going the “Air Pot/Damper” Route, this also strikes me as being “Worth a Shot” I know at least one of my Lathtroll Buddies is modifying his VR to “Airpot Damping” as I write, and I will encourage him to Post the results of his endeavours here on the Forum , but out of the many Lathetrolls who own the VR, why not others??? Gravity can sometimes be a bit of a nuisance. Oil is Messy!! Oil (Usually) Flows Downhill, therefore the “VR Dashpot” also therefore needs to be as Close to Vertical as Practicable. Do other Lathetrolls not share my view that this is a “Design Limitation” restricting Optimum Positioning on the VR??? One that would not exist if the “Airpot Alternative” was used instead???
Examples of Modifications Demonstrating such changes are possible :-

Airpot on Hara M180 Lathe.jpg

Airpot on BSR DR33C Lathe.jpg

Airpot on Presto-Sugden Adaptor-1.jpg



Various Trolls wrote :-

“the head seems suspended well in the new oil”

”I didn't have Souri's dashpot oil.... so i'm gonig to try some SAE 50 oil, or maybe 40, off advice from a friend”[/quote
[]

“That's a good point - maybe we can do a quick straw poll... What weight of oil is everyone using in their VR dashpot?”

[/]

“the dashpot also active in cutting the plunger in the oil should dampen out movment along with the spring, not sure what the thickness oil in mine but have been using carburettor damper oil in the dashpot”

In my own view, the most Most Thoughtful and Practical inputs were made by Markrob and trailerparkjesus, when they suggested:-

“Honestly, most of these issues are from sticking parts”

“Have you checked to see if the dashpot is damping the head movement properly? If you float the head and give it a slight tap, does it oscillate a few times before settling down? That would indicate that it’s under damped and may need a higher viscosity oil. If it’s over damped, is it sluggish settling down? That would indicate the opposite issue. It would also be interesting to try the experiment dead cold and then after heating the dashpot and other areas with a hair dryer to see if the behaviour changes Another thing to look at is if the undamped motion of the head (no dashpot oil present) is being hindered by bad suspension bearings or some other friction due to rubbing. Friction/ sticktion can act as a damper, but unless it’s controlled, the results could be variable especially with temperature”

My point is this, Why to bother your heads with unnecessary formulae, Temperature Coefficients,, or worry about finding the correct “Weight/Viscosity” of Oil??
Simply Modify the VR And at a Cost of $1 per 1000 Spring/Units, Choose maybe a few "Different Springs" to Try Out, Fit an “Airpot” and Adjust 1 Screw to tune the System!!! And Let us know the results
Regards Soulbear

I'm in contact with Airpot at the moment, will be upgrading for sure

[PMST]

Sorry that post included my post, within the quote! Soulbear... I'm in contact with Airpot at the moment, will be upgrading for sure Glad to see good reports from it!

[Soulbear]

I'm in contact with Airpot at the moment, will be upgrading for sure

Kudos to you PMST.....And I sincerely wish you good luck with your efforts
It's good to sometimes not accept the Status Quo, to be creative, adventurous and experiment a little. We know statistically that many experiments end in perceived "Failure"

Without trying to sound "Cliche" no experiment is really and truly a failure because, as it has been said many many times before, even if your "Airpot Modification Experimentation" does not give the results you expected, it will not be a failure. All of the many tests and observations you make, can be used to inform other VR Users, and to maybe plan tests of a different variable. In this case (and it's only a couple of suggestions here) the "Variables" might include "Spring Diameter" "Spring Wire Diameter" "Number of Spring Coils" "Spring Length" "Airpot Piston Stroke Distance" "Airpot Diameter" "Physical Positioning/Location" etc...etc...

I'm instinctively inclined to feel sure you will succeed with this. The two Damper Mediums are so radically different. Variablity of "Air Compressiblity" in an Airpot is miniscule when compared to changes of "Oil Viscosity" in an Oil-filled Damper due to Temperature Changes. And with a little thought, the "Modifications" you make will be "Reversible" that is, capable of being reversed so that the previous state of the VR is restored if needs be. Nothing much to Loose, and very much to Gain in my View. And it will add to the "Public Body of Knowledge" shared on this Splendid Lathetrolls Forum, to the benefit of all other VR Users. Can't wait to read about your results, you go for it PMST
Best Regards Soulbear

[PMST]

I'm in contact with Airpot at the moment, will be upgrading for sure

Kudos to you PMST.....And I sincerely wish you good luck with your efforts
It's good to sometimes not accept the Status Quo, to be creative, adventurous and experiment a little. We know statistically that many experiments end in perceived "Failure"

Without trying to sound "Cliche" no experiment is really and truly a failure because, as it has been said many many times before, even if your "Airpot Modification Experimentation" does not give the results you expected, it will not be a failure. All of the many tests and observations you make, can be used to inform other VR Users, and to maybe plan tests of a different variable. In this case (and it's only a couple of suggestions here) the "Variables" might include "Spring Diameter" "Spring Wire Diameter" "Number of Spring Coils" "Spring Length" "Airpot Piston Stroke Distance" "Airpot Diameter" "Physical Positioning/Location" etc...etc...

I'm instinctively inclined to feel sure you will succeed with this. The two Damper Mediums are so radically different. Variablity of "Air Compressiblity" in an Airpot is miniscule when compared to changes of "Oil Viscosity" in an Oil-filled Damper due to Temperature Changes. And with a little thought, the "Modifications" you make will be "Reversible" that is, capable of being reversed so that the previous state of the VR is restored if needs be. Nothing much to Loose, and very much to Gain in my View. And it will add to the "Public Body of Knowledge" shared on this Splendid Lathetrolls Forum, to the benefit of all other VR Users. Can't wait to read about your results, you go for it PMST
Best Regards Soulbear

I agree 100%, for sure its a great starting point, but we must all be open to adjustments and improvements! Really can not wait to try the Airpot.

I don't have any of souri's oil, hence my issue, but currently as we speak I am cutting, with SAE 50 oil, had teething issues but might of sorted them so will report for others who might be in the same situation. but as you say, no experiment is pointless, all valid info on what does and doesn't work! Hopefully if I get it working good its info to help someone else along the way.

Great lathe by the way, nice to see a Airpot in action!