tone arm lift

[woodturner-fran]

Hi all,


Has anyone come across a good simple design for a DIY arm lift?

or alternatively a source for buying them new?


I could do with one for a new unipivot I made and although I've looked at a few vintage decks for scavenging they all are automatic lifts.

Fran

[Nanook]

something like a bicycle seat post "quick release" could be ok. Basically a cam in a end with a handle.

[Mark Kelly]

Can be bought new from Jelco in Japan, their model JL45. If you start a GB I'm in for at least two.

Jelco site (scroll for JL45)

[hailteflon]

Whatever you do you might keep in mind that the viscous effect is obtained with some very thick silicon oil.

Keeping in mind that 90W differential oil is way less than 100 rating.

The silicon viscous fluid comes in ratings of 30,000, 50,000 and on up to 500K.

It is used in the differentials of hobby cars. 50K is probably what you would want to try first. Mark

[Mark Kelly]

Originally posted by hailteflon

Keeping in mind that 90W differential oil is way less than 100 rating.

The silicon viscous fluid comes in ratings of 30,000, 50,000 and on up to 500K.

You appear to be confusing SAE oil ratings ( eg 90W) with actual viscosity measurements in centiPoise (eg 30,000).

The two are only distantly related as seen here:

Roymech on Viscosity

[hailteflon]

No, I found some spec sheets for some gear lube and the cp number is surprisingly low. I may have been higher than 100, but I am not confusing the two rating systems.


The following is from a gear lube spec sheet. This is one of about twenty lube pages that I stored. I don't know if the cSt is the same as the cp. This is 140W gear oil.

Appearance Light Straw Transparent Fluid
Viscosity, cSt @ 100°C 55.41 77.35
Viscosity, cSt @ 40°C 697.54 1079.19
Viscosity Index 140 145

If I find a spec that says "cp" then I will post it. I tried STP and it did nothing. I tried silicon grease and it did nothing.

I tried to align the chart, but the preview messes it up again, sorry.

[woodturner-fran]

I've sent an email to Jelco to see how much they cost etc. But at this moment something in the DIY route is preferable. The damping isn't that critical to me, just a lift/lower is all thats required...


Fran

[hailteflon]

You may find that viscous damping is more important than you thought.

Mr. Kelly's post has raised a good question. What rating system is used? For those who may be interested in the future I will post the results if I can find an MSDS on traxxas diff lube 30W product number TRA5136.

The following is what I have found so far.

The viscosity of water at room temperature is approximately 1 cP

cp (centipoise) is the dynamic viscosity and cst (centistokes) is the kinematic
viscosity. I was unable to find a conversion factor because the units are different.

“Valvoline Gear Lube passed the test at 130,000 cP, “ said of 90W gear oil. So, the weight of this silicone oil isn’t in cp. The bottle says “30K weight.”

Traxxas has one of those ultra-worthless websites that will not readily respond to the description, labels, or part numbers of its own products. If I figure out what 30K weight means on the bottle I will post it.

[Mark Kelly]

To convert between dynamic and kinematic viscosity you simply divide by the density. Read the reference I posted above (Roymech).

I believe that the standard "weights" of silicone oil in the US are in cS, that's certainly how Dow Corning specify theirs. Since silicone oil has a density very close to 1 g/cc, I don't think there's a big difference between cS and cP for these fluids.

[hailteflon]

Divide by the density. Sounds easy enough.

The following is about the super-thick silicone fluids.


100,000 cSt dimethyl silicone fluid emulsion

Zander Colloids website

This is evidently where I got the comparison to gear lube.

So, 90W gear oil is about 1000cst at room temp.

This silicone fluid is some thick stuff.