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Old 24th August 2008, 09:16 PM   #1
Tenson is offline Tenson  United Kingdom
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Default How can I fix this?

Hi,

I recently bought a Cyrus DAD7 CD player that is top loading. The lid is meant to have a damped action as it closes - you give it a little push and it lowers itself down.

It was second hand and the lid took forever to close, so I thought I'd give the insides a bit of a clean. It seems to work by a small syringe-like device (didn't seem to have anything other than air in it) that is fixed at one end and connected to the lid hinge at the other. As the lid closes the distance between the fixed point and the hinge increases, and the plunger thing offers resistance against that.

Having cleaned it, the friction is too high and the lid doesn't close unless you push it down all the way. As you would expect with friction trying to stop it, it's not a smooth movement either. When I add even the smallest amount of oil or grease, it just flops down right away with no damped action.

Click the image to open in full size.
As the lid closes, the distance between points A and B increases.

Now my question that goes out to you guys is - What can I do to offer a linear resistance to the lid as it closes? I have pretty much given up on making the original plunger work again. My first thought was a bit of weak elastic, but that will offer more resistance as the distance increases, so not ideal. It will also sag, as it will spend most of its time under tension as the lid is down. Same with a soft spring (and finding one that has just the right tension is going to be difficult).

How does the mechanisum that makes a tape measure retract work? That might be a good starting point. I want to hear your clever ideas!
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Old 24th August 2008, 10:12 PM   #2
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Try some (a thin layer) silicone damper oil - sold in model/toy shops for radio control cars, both in the suspension dampers and the differential -, in the original cylinder & piston assembly.
Probably you need a viscosity of around or upwards of 50 000 centipoise
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Old 24th August 2008, 10:45 PM   #3
Tenson is offline Tenson  United Kingdom
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Hi Steerpike,

Do you suggest this as a fluid to be compressed in the plunger, or as a viscous lubricant simply to coat the inside of the tube? From you post I assume the latter.

I tried a bit of Vaseline as grease but it made it slip far too easily. Is the silicon damping much differnt?
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Old 25th August 2008, 12:29 AM   #4
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Hello Tenson, A picture would help, but from your description, it sounds as if they used a dashpot. This is a device that works like a small shock absorber, but it uses air to cushion the rate that the piston moves at. It's possible that with the cleaning, a seal was damaged, now the air is allowed to flow too fast. I would suspect that the seal around the circumference of the piston is worn, thus it doesn't seal well to the internal face of the cylinder. It's also possible that the valve that allows air to flow at a controlled rate isn't working correctly. The name I can think of that makes this is Airpot @ http://www.airpot.com/.
Hope this helps.

Peace,

Dave
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Old 25th August 2008, 12:41 AM   #5
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Quote:
I tried a bit of Vaseline as grease but it made it slip far too easily. Is the silicon damping much differnt?
Yes, the silicone damper oil is very much like syrup in consistency, but a lubricant too. So it will only allow the piston to slowly glide in the cylinder, not move quickly.
I'm guessing you only need a thin layer - use it a if it were a lubricant. Too much will drip out.

You'll need to clean out the vaseline completely first though - turpentine ough to work for that.
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Old 25th August 2008, 01:46 AM   #6
Tenson is offline Tenson  United Kingdom
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Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

It does look a lot like the 'Snubbers' on that Airpot page. However, they say there is a valve in the end to control the amount of airflow. This is just a threaded hole with a screw. Its not a valve. Although, there is a small crack in the bit where the screw goes that gets wider as it gets tightened, but it looks like it is broken, not intentional.

Covering the little crack with a bit of PVC tape doesn't improve things (air might have been leaking too fast).

Annoyingly, there is no part number on it! Maybe Cyrus will send me a new one, but I get the feeling they like to service the players themselves.
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Old 25th August 2008, 06:57 AM   #7
Mooly is offline Mooly  United Kingdom
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Hi,
Probably not much help but these dampers were all the rage in the 80's & 90's on music center cassette deck doors.
Agree with steerpike, you have to totally clean it out. Foam cleaner and a little brush ? Remove the O ring and wash that too.
If the plastic is damaged at all round the screw the "plastic metal" type epoxy can be useful.
The secret is in the viscosity of the oil. It's that long since I have seen one now, I am sure you do want just a thin oil and don't you adjust the screw to get the required action. Make sure you DONT use a mineral oil that will soften plastic. WD40 ? that's OK with plastics.
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Old 26th August 2008, 10:02 AM   #8
Eva is offline Eva  Spain
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You have to repair the crack to make it back air tight. You may use a soldering iron to carefully solder the plastic (this is tricky, read on proper techniques) or epoxy-like stuff.
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Old 27th August 2008, 02:20 AM   #9
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If you intend to 'pimp it out', you could replace it with an oil damper from an rc car (radio controlled for completeness ) Then you could really go to work on adjusting the time constant, peak no-load velocity etc..
Otherwise try the solderingiron and or find a solvent glue that dissovles the plastic a little & use some'o that. My bet is a bit of polyurethane cement would be useful here. As the N.Americans quite often instruct in construction manuals, 'use ingenuity.' I believe this can be ordered online somewhere
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Old 28th August 2008, 12:48 AM   #10
Tenson is offline Tenson  United Kingdom
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Thanks for all the replies.

I called Cyrus yesterday and unfortunately they don't have any of the dampers left. So I will either have to fix this or find a replacement.

Where can I get a small amount of this silicone damper oil online? There are no model shops near me and I want to make sure I get the right sort. Most of the model sites I have found don't rate the viscosity in cP, only an arbitrary number. Well it might be cP, bit it seems rather low for that if 50,000 is what I want. For example - http://www.fusionhobbies.com/Tamiya-...-p/ta53445.htm

and

http://www.fusionhobbies.com/Schumac...20w-p/g120.htm

Alternatively where can I get a full replacement? I looked at a website called 'Ace Controls' but their smallest unit didn't have enough stroke length, and the next size up was too big externally.

The main body of the one in the player is 35mm when closed, and 60mm when extended. Its about 8mm dia, but the gap in the player would fit up to about 13mm. What other ones are out there?
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