Topic: Viscosity of Silicone Oil in Instrument Dampers/Dashpot

[AshimotoK0]

Now here is a teaser for you. A chocolate frog will be awarded to anyone providing the correct answer !!!!

What is the viscosity of the silicone oil in the dashpot/damper of CB750 instruments  (tacho and speedo)?

BTW it looks to me that if you store the instrument face down the oil can leak out of the damper!!

Cheers

Ash

[betterthanurs916]

I'm gonna go with a kinematic viscosity of around 22 Centi-stokes

[killerdwarf]

it's baby oil

[Duke McDukiedook]

Astroglide.

[Jerry Rxman Griffin aka MuthaF'er]

Glycerin

[AshimotoK0]

Thanks for the suggestions. Anyone actually used what they are proposing? I will have the original Nippon Denso stuff analysed chemically next week but there is not enough to measure its viscosity (The test  sample will be from a 750K7 clock, not my 750K0)

How about laser printer toner oil (silicone)

Best regards

Ash

[AshimotoK0]

Astroglide.

Just Googled 'Astroglide' (didn't realize what it was) Just like on my first business trip to Rockford Illinois, I asked the girl from the plant who was in the hotel too 'can you knock me up in the morning' and got a nasty look. I should have said ' Can you give me a wake up call'. The next day at the factory I was drafting out a circuit diagram and  I asked the secretary ' Do you have a rubber I can borrow'. same response. Should have asked for pencil eraser.

Cheers - Ash

[wrenchmuch]

I have a tach pulled apart to this point . I have ordered some 30,000 cSt silicone fluid and when it gets here I'll put it all back together and see how it works . I don't know if the stuff evaporates over time but certainly storing gauges face down is a bad idea . I just got a pair of gauges that the PO swears were stored face up for my 750 K1 . 5200 miles on the speedo . No staining on the face but the needles are a bit eratic leading me to belive the stuff can evaporate over time . I've taken lots of pics of the process and will post all when I have a solution that works . This tach will be my test bed .

Edit : The clock in the pic is from a 750 K4 . The face was lightly stained and the damper pot was empty . The face looks good except for the stain . Anyone know how to get the stain off ?

[Duke McDukiedook]

Astroglide.

Just Googled 'Astroglide' (didn't realize what it was) Just like on my first business trip to Rockford Illinois, I asked the girl from the plant who was in the hotel too 'can you knock me up in the morning' and got a nasty look. I should have said ' Can you give me a wake up call'. The next day at the factory I was drafting out a circuit diagram and  I asked the secretary ' Do you have a rubber I can borrow'. same response. Should have asked for pencil eraser.

Cheers - Ash

Ah yes, nothing like getting the gist lost in translation. 

[grumpy]

I have ordered some 30,000 cSt silicone fluid and when it gets here I'll put it all back together and see how it works .

Yes please!!!
Let us know if it works!


Where did you order from?

[domer]

subscribed... especially since im about to put mine back together...

[AshimotoK0]

Please also see:

http://www.sohc.co.uk/index.php?topic=3154.0

Also

http://www.turntablebasics.com/silicone.html

Cheers

Ash

[wrenchmuch]

I ordered from turntable basics . Communication is not good . I paid via pay pal and got an automated response acknowledging my order but nothing since . I ordered 2 weeks ago . I emailed 3 days ago to ask if it had been shipped yet and still nothing . At the moment I can't recommend buying from them . I found out that the same type of fluid is used in R.C. car transmissions .
http://hobbyhobby.com/store/product/150178/Silicone-Diff-Fluid--30000CS/
I'll go and check it out before the end of the week . In the mean time I'll go pester turntable basics again.

[scottly]

While I have never heard of a Damper/Dashpot in a speedo or tach, I do know you can find silicone oil in a wide range of viscosity at hobby shops. It is used in the shock absorbers and limited slip differentials of remote control cars and trucks.

Edit: just saw your link, wrench... 

[grumpy]

$3.87

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=390246090967


 

[wrenchmuch]

Went to the hobby store today and got 7000 ,10000 ,30000 ,60000, and 100000 cst silicone differential fluid . They also had silicone shock oil but its like dot5 brake fluid (low viscosity ) . I'll try some out this weekend . Any opinions on which one to try first ? I'll fill the pot and then re-assemble to the point where the pointer goes back on , then I'll try it on the bike . Tired of waiting for Turntable Basics . Don't buy the stuff there .

[scottly]

Are you guys sure that the "pot" is supposed to be filled with oil? If so, wouldn't it have some sort of seal to keep the oil in? I think the "pot" is the magnetic coupling between the cable and the needle, with the resistance to the needle provided by the clock-spring. The magnetic coupling inherently provides some damping. That's how every speedo and tach I've ever seen worked....

[Bodi]

I'm with Scottly on this one.
I've cleaned out a few speedos and tachs by filling them through the lamp holes with pure isopropyl and swishing it around, this (after a few iterations) cleans off the face and glass and has freed up at least one sticky (ie rpm pins above some point) instrument. If there was some fluid in there it would be washed out and the instrument wouldn't work. The ones I've opened up have been dry except maybe a bit of lube on the "jewels". Yours may well work differently, of course - I haven't done 750 ones.
Anyway silicon fluid does evaporate, somehow. I have serviced machines with open silicon fluid cups (100,000 cst as I recall, thick as honey) and these cups would have to be refilled every few years.

[scottly]

Do I win the chocolate frog Wait a minute; just WHAT is a chocolate frog? Not sure if I want one, after hearing about some of the stuff they are serving up at the state fair, like deep-fried bacon. Yum, deep-fried fat.

[wrenchmuch]

There is a top on the cup . There is a dark hard substance that seals the cap to the pot . The cap has a hole in the center that the stationary bearing for the needle passes through . The cap doesn't touch this bearing (brass tube) though . If it did it would cause drag on the moving assembly . Its this gap between the cap and the bearing (brass tube ) that either lets the fluid evaporate or leak out (when the gauge is on its face ) . What was left of the fluid in the pot was thick and sticky , could be old oil though . The magnetic drive for the tach is at the back of the tach . The pot I'm talking about is at the front , behind the face . Since I have it this far apart I'm going to go ahead and try the fluid in it . The pin that the pointer mounts to passes through the bearing (brass tube ) and I think its the fluid in the gap between the two that provides the damping action . I'll try the 30000 cst first .

[scottly]

OK, no chocolate frog for me, I guess. I still can't wrap my head around this, though. Do you have any pics??

[wrenchmuch]

The damper pot is just above the spring .

[scottly]

Thanks. As far as the viscosity is concerned, if it is too high, your instruments will be slow to react. Probably more of a issue with the tach than the speedo.

[Motorcity]

Mineral Oil, they use it in some liquid filled gauges.

[AshimotoK0]

Hmm Chocolate Frog - the saying came from a guy I used to share an office with in the eighties. He used to work in the aerospace industry so I will phone him and ask him where I can get frogs. I seem to recall they were called 'Freddo's

MORE importantly this guy told me about a concoction they used at British Aerospace to chromate etch aluminium parts to help the  paint adhere well and i need to quiz him about it. Pretty sure it used tr-valent chromium chemicals hough so like all good stuff - nasty and hard to get hold of.

Been away all week but going to pursue the Minolta CF 900 silicone user oil for damper fluid (I have 750ccs of it). Probably enough for 750 750's  

http://en.wikipedia.org/wiki/Freddo_Frog

Cheers

Ash